Geology and geomorphology of Bear Lake Valley and upper Bear River, Utah and Idaho

USGS Publications Warehouse

Reheis, M.C.; Laabs, B.J.C.; Kaufman, D.S.

2009-01-01

Bear Lake, on the Idaho-Utah border, lies in a fault-bounded valley through which the Bear River flows en route to the Great Salt Lake. Surficial deposits in the Bear Lake drainage basin provide a geologic context for interpretation of cores from Bear Lake deposits. In addition to groundwater discharge, Bear Lake received water and sediment from its own small drainage basin and sometimes from the Bear River and its glaciated headwaters. The lake basin interacts with the river in complex ways that are modulated by climatically induced lake-level changes, by the distribution of active Quaternary faults, and by the migration of the river across its fluvial fan north of the present lake. The upper Bear River flows northward for ???150 km from its headwaters in the northwestern Uinta Mountains, generally following the strike of regional Laramide and late Cenozoic structures. These structures likely also control the flow paths of groundwater that feeds Bear Lake, and groundwater-fed streams are the largest source of water when the lake is isolated from the Bear River. The present configuration of the Bear River with respect to Bear Lake Valley may not have been established until the late Pliocene. The absence of Uinta Range-derived quartzites in fluvial gravel on the crest of the Bear Lake Plateau east of Bear Lake suggests that the present headwaters were not part of the drainage basin in the late Tertiary. Newly mapped glacial deposits in the Bear River Range west of Bear Lake indicate several advances of valley glaciers that were probably coeval with glaciations in the Uinta Mountains. Much of the meltwater from these glaciers may have reached Bear Lake via groundwater pathways through infiltration in the karst terrain of the Bear River Range. At times during the Pleistocene, the Bear River flowed into Bear Lake and water level rose to the valley threshold at Nounan narrows. This threshold has been modified by aggradation, downcutting, and tectonics. Maximum lake levels have decreased from as high as 1830 m to 1806 m above sea level since the early Pleistocene due to episodic downcutting by the Bear River. The oldest exposed lacustrine sediments in Bear Lake Valley are probably of Pliocene age. Several high-lake phases during the early and middle Pleistocene were separated by episodes of fluvial incision. Threshold incision was not constant, however, because lake highstands of as much as 8 m above bedrock threshold level resulted from aggradation and possibly landsliding at least twice during the late-middle and late Pleistocene. Abandoned stream channels within the low-lying, fault-bounded region between Bear Lake and the modern Bear River show that Bear River progressively shifted northward during the Holocene. Several factors including faulting, location of the fluvial fan, and channel migration across the fluvial fan probably interacted to produce these changes in channel position. Late Quaternary slip rates on the east Bear Lake fault zone are estimated by using the water-level history of Bear Lake, assuming little or no displacement on dated deposits on the west side of the valley. Uplifted lacustrine deposits representing Pliocene to middle Pleistocene highstands of Bear Lake on the footwall block of the east Bear Lake fault zone provide dramatic evidence of long-term slip. Slip rates during the late Pleistocene increased from north to south along the east Bear Lake fault zone, consistent with the tectonic geomorphology. In addition, slip rates on the southern section of the fault zone have apparently decreased over the past 50 k.y. Copyright ?? 2009 The Geological Society of America.

Geohydrology of deep-aquifer system monitoring-well site at Marina, Monterey County, California

USGS Publications Warehouse

Hanson, Randall T.; Everett, Rhett; Newhouse, Mark W.; Crawford, Steven M.; Pimentel, M. Isabel; Smith, Gregory A.

2002-01-01

In 2000, a deep-aquifer system monitoring-well site (DMW1) was completed at Marina, California to provide basic geologic and hydrologic information about the deep-aquifer system in the coastal region of the Salinas Valley. The monitoring-well site contains four wells in a single borehole; one completed from 930 to 950 feet below land surface (bls) in the Paso Robles Formation (DMW1-4); one 1,040 to 1,060 feet below land surface in the upper Purisima Formation (DMW1-3); one from 1,410 to 1,430 feet below land surface in the middle Purisima Formation (DMW1-2); and one from 1,820 to 1,860 feet below land surface in the lower Purisima Formation (DMW1-1). The monitoring site is installed between the coast and several deep-aquifer system supply wells in the Marina Coast Water District, and the completion depths are within the zones screened in those supply wells. Sediments below a depth of 955 feet at DMW1 are Pliocene age, whereas the sediments encountered at the water-supply wells are Pleistocene age at an equivalent depth. Water levels are below sea level in DMW1 and the Marina Water District deep-aquifer system supply wells, which indicate that the potential for seawater intrusion exists in the deep-aquifer system. If the aquifers at DMW1 are hydraulically connected with the submarine outcrops in Monterey Bay, then the water levels at the DMW1 site are 8 to 27 feet below the level necessary to prevent seawater intrusion. Numerous thick fine-grained interbeds and confining units in the aquifer systems retard the vertical movement of fresh and saline ground water between aquifers and restrict the movement of seawater to narrow water-bearing zones in the upper-aquifer system.Hydraulic testing of the DMW1 and the Marina Water District supply wells indicates that the tested zones within the deep-aquifer system are transmissive water-bearing units with hydraulic conductivities ranging from 2 to 14.5 feet per day. The hydraulic properties of the supply wells and monitoring wells are similar, even though the wells are completed in different geologic formations.Geophysical logs collected at the DMW1 site indicate saline water in most water-bearing zones shallower than 720 feet below land surface and from about 1,025 to 1,130 feet below land surface, and indicate fresher water from about 910 to 950 feet below land surface (DMW1-4), 1,130 to 1,550 feet below land surface, and below 1,650 feet below land surface. Temporal differences between electromagnetic induction logs indicate possible seasonal seawater intrusion in five water-bearing zones from 350 to 675 feet below land surface in the upper-aquifer system.The water-chemistry analyses from the deep-aquifer system monitoring and supply wells indicate that these deep aquifers in the Marina area contain potable water with the exception of the saline water in well DMW1-3. The saline water from well DMW1-3 has a chloride concentration of 10,800 milligrams per liter and dissolved solids concentration of 23,800 milligrams per liter. The source of this water was determined not to be recent seawater based on geochemical indicators and the age of the ground water. The high salinity of this ground water may be related to the dissolution of salts from the saline marine clays that surround the water-bearing zone screened by DMW1-3. The major ion water chemistry of the monitoring wells and the nearby MCWD water-supply wells are similar, which may indicate they are in hydraulic connection, even though the stratigraphic layers differ below 955 feet below land surface.No tritium was detected in samples from the deep monitoring wells. The lack of tritium suggest that there is no recent recharge water (less than 50 years old) in the deep-aquifer system at the DMW1 site. The carbon-14 analyses of these samples indicate ground water from the monitoring site was recharged thousands of years ago.

Vertical variability in saturated zone hydrochemistry near Yucca Mountain, Nevada

USGS Publications Warehouse

Patterson, G.L.; Striffler, P.S.

2006-01-01

The differences in the saturated zone hydrochemistry with depth at borehole NC-EWDP-22PC reflect the addition of recharge along Fortymile Wash. The differences in water chemistry with depth at borehole NC-EWDP-19PB appear to indicate that other processes are involved. Water from the lower part of NC-EWDP-19PB possesses chemical characteristics that clearly indicate that it has undergone cation exchange that resulted in the removal of calcium and magnesium and the addition of sodium. This water is very similar to water from the Western Yucca Mountain facies that has previously been thought to flow west of NC-EWDP-19PB. Water from the lower zone in NC-EWDP-19PB also could represent water from the Eastern Yucca Mountain fades that has moved through day-bearing or zeolitized aquifer material resulting in the altered chemistry. Water chemistry from the upper part of the saturated zone at NC-EWDP-19PB, both zones at NC-EWDP-22PC, and wells in the Fortymile Wash facies appears to be the result of recharge through the alluvium south of Yucca Mountain and within the Fortymile Wash channel.

Results of borehole geophysical logging and hydraulic tests conducted in Area D supply wells, former U.S. Naval Air Warfare Center, Warminster, Pennsylvania

USGS Publications Warehouse

Sloto, Ronald A.; Grazul, Kevin E.

1998-01-01

Borehole geophysical logging, aquifer tests, and aquifer-isolation (packer) tests were conducted in four supply wells at the former U.S. Naval Air Warfare Center (NAWC) in Warminster, PA, to identify the depth and yield of water-bearing zones, occurrence of borehole flow, and effect of pumping on nearby wells. The study was conducted as part of an ongoing evaluation of ground-water contamination at the NAWC. Caliper, natural-gamma, single-point resistance, fluid resistivity, and fluid temperature logs and borehole television surveys were run in the supply wells, which range in depth from 242 to 560 ft (feet). Acoustic borehole televiewer and borehole deviation logs were run in two of the wells. The direction and rate of borehole-fluid movement under non-pumping conditions were measured with a high-resolution heatpulse flowmeter. The logs were used to locate water-bearing fractures, determine probable zones of vertical borehole-fluid movement, and determine the depth to set packers. An aquifer test was conducted in each well to determine open-hole specific capacity and the effect of pumping the open borehole on water levels in nearby wells. Specific capacities ranged from 0.21 to 1.7 (gal/min)/ft (gallons per minute per foot) of drawdown. Aquifer-isolation tests were conducted in each well to determine depth-discrete specific capacities and to determine the effect of pumping an individual fracture or fracture zone on water levels in nearby wells. Specific capacities of individual fractures and fracture zones ranged from 0 to 2.3 (gal/min)/ft. Most fractures identified as water-producing or water-receiving zones by borehole geophysical methods produced water when isolated and pumped. All hydrologically active fractures below 250 ft below land surface were identified as water-receiving zones and produced little water when isolated and pumped. In the two wells greater then 540 ft deep, downward borehole flow to the deep water-receiving fractures is caused by a large difference in head (as much as greater then 49 ft) between water-bearing fractured in the upper and lower part of the borehole. Vertical distribution of specific capacity between land surface and 250 ft below land surface is not related to depth.

Hydrogeologic framework, availability of water supplies, and saltwater intrusion, Cape May County, New Jersey

USGS Publications Warehouse

Lacombe, Pierre J.; Carleton, Glen B.

2002-01-01

During 1960-90, saltwater intrusion forced the abandonment of at least 10 public-supply wells, 3 industrial-supply wells, and more than 100 domestic-supply wells in Cape May County, N.J. Actual or imminent ground-water contamination caused by land-use practices and human activities has forced the closure of at least six shallow public-supply wells and many domestic-supply wells. Freshwater in Cape May County flows in many small streams and is held in wetlands and natural and artificial ponds. More importantly, freshwater from precipitation passes through and is stored in five aquifers-- Holly Beach water-bearing zone, estuarine sand aquifer, Cohansey aquifer, Rio Grande water-bearing zone, and Atlantic City 800-foot sand. Surface-water discharges were measured at 14 stream sites. The Tuckahoe River is the largest stream in Cape May County. The mean annual discharge for the Tuckahoe River at Head of River was 43.8 ft3/s (cubic feet per second) or 10,800 Mgal/yr (million gallons per year) during the period of record (1969-93). Mean daily discharge ranged from 25 ft3/s or 16 Mgal/d in September to 73 ft3/s or 47 Mgal/d in April. Mean daily discharge at the eight largest streams wholly within the county ranged from 15.9 to 3.05 ft3/s (3,750 to 720 Mgal/yr). Total water use in the county was about 8,600 Mgal/yr in 1990, including about 25 Mgal/yr of surface water, 3,000 Mgal/yr from the Holly Beach water-bearing zone, 1,000 Mgal/yr from the estuarine sand aquifer, 2,200 Mgal/yr from the Cohansey aquifer, 200 Mgal/yr from the Rio Grande water-bearing zone, and 2,200 Mgal/yr from the Atlantic City 800-foot sand. Water-level data collected during April 1991 for more than 200 wells show that in some locations ground-water flow directions and rates have changed when compared with those shown on historical potentiometric-surface maps. In 1991, water levels in the Holly Beach water-bearing zone were nearly identical to levels prior to development. A cone of depression has developed in the estuarine sand aquifer; the water-level altitude near the center of the cone was about -5 ft in 1991. An extensive cone of depression has developed in the Cohansey aquifer; the water-level altitude near the center of the cone was about -20 ft. A small cone of depression has developed in the Rio Grande water-bearing zone; the altitude near the center was -5 ft. An elongated cone of depression has developed in the Atlantic City 800-foot sand; the water-level altitude was about -70 ft in Ocean City and -20 ft in Stone Harbor. Waterlevel maps from predevelopment, 1958, 1978, 1983, and 1988 show that the cones of depression are getting deeper and are expanding in the Atlantic City 800-foot sand. The 250-mg/L (milligram per liter) line of equal chloride concentration and 50 mg/L line of equal sodium concentration have moved inland, possibly since the early 1900's. Chloride concentrations have increased in many wells in the confined aquifers along the coastline in the southern part of the county. Nitrate concentrations greater than 1 mg/L were present in water samples collected from 10 wells that tap the Holly Beach water-bearing zone. Concentrations of nitrate greater than 10 mg/L in samples collected in Lower, Middle, Upper, and Dennis Townships may result from effluent from septic systems or from agricultural activities. A water budget shows that the mean annual precipitation is about 42 in., and about 119,000 Mgal falls each year on uplands and freshwater wetlands in the county. About 63,600 Mgal/yr is evapotranspired, 8,200 Mgal/yr becomes overland flow, and 47,200 Mgal/yr recharges the Holly Beach water-bearing zone. In northern Cape MayCounty, most recharge ultimately is discharged to streams. In southern Cape May County, about 20 percent of recharge is diverted to withdrawal wells. Because saltwater intrusion has occurred in the confined aquifers along the Atlantic and Delaware Bay coastlines, new supply wells placed along th

Geohydrology and water chemistry in the Rialto-Colton Basin, San Bernardino County, California

USGS Publications Warehouse

Woolfenden, Linda R.; Kadhim, Dina

1997-01-01

The 40-square-mile Rialto-Colton ground- water basin is in western San Bernardino County, California, about 60 miles east of Los Angeles.This basin was chosen for storage of imported water because of the good quality of native ground water, the known capacity for additional ground-water storage in the basin, and the availability of imported water. Because the movement and mixing of imported water needed to be determined, the San Bernardino Valley Municipal Water District entered into a cooperative program with the U.S.Geological Survey in 1991 to study the geohydrology and water chemistry in the Rialto- Colton basin. Ground-water flow and chemistry were investigated using existing data, borehole- geophysical and lithologic logs from newly drilled test holes, measurement of water levels, and chemical analyses of water samples. The Rialto-Colton basin is bounded on the northwest and southeast by the San Gabriel Mountains and the Badlands, respectively. The San Jacinto Fault and Barrier E form the northeastern boundary, and the Rialto-Colton Fault forms the southwestern boundary. Except in the southeastern part of the basin, the San Jacinto and Rialto-Colton Faults act as groundwater barriers that impede ground- water flow into and out of the basin.Barrier E generally does not impede ground- water flow into the basin. The ground-water system consists primarily of gravel, sand, silt, and clay. The maximum thickness is greater than 1,000 feet. The ground- water system is divided into four water-bearing units: river-channel deposits, and upper, middle, and lower water-bearing units. Relatively impermeable consolidated deposits underlie the lower water- bearing unit and form the lower boundary of the ground- water system. Ground water moves from east to west in the river-channel deposits and upper water-bearing unit in the southeastern part of the basin, and from northwest to southeast in the middle and lower water-bearing units. Two major internal faults, Barrier J and an unnamed fault, affect ground-water movement. Ground water moves across Barrier J in the unfaulted part of the ground-water system. The unnamed fault is a partial barrier to ground-water movement in the middle water- bearing unit and an effective barrier in the lower water-bearing unit.Imported water flows laterally across the unnamed fault above the saturated zone. Major sources of recharge to the ground- water system are underflow; precipitation that collects in small streams that drain the San Gabriel Mountains and the Badlands or runs off the mountain front as sheet flow, and sub-surface inflow; imported water; seepage loss from the Santa Ana River and Warm Creek; infiltration of rainfall; and irrigation return flow. The main component of discharge is pumpage. Long-term water levels in production wells reflect precipitation cycles. During a 194777 dry period, water levels in three wells declined almost continuously?as much as 100 feet in one well.Water levels in a well north of Barrier J are not affected by stresses on the groundwater system south of the barrier, indicating that these two parts of the ground-water system are not well connected. Water levels in cluster wells east of the unnamed fault north and south of the Linden Ponds artificial-recharge site rose as much as 70 feet during 1992-95. The rise in water levels in wells near the recharge ponds was observed within 2 months after the beginning of recharge. Water levels in most wells west of the unnamed fault changed very little during 1992-95. Water-chemistry data indicate that chemical characteristics vary within the groundwater system, and that dissolvedsolids concentrations are generally higher in the river-channel deposits, upper water- bearing unit, and the consolidated deposits than in the middle and lower water-bearing units. The chemical characteristics in water from the middle water-bearing unit were similar for most wells sampled west of the unnamed fault. In water from well

A subtle diagenetic trap in the Cretaceous Glauconite Sandstone of Southwest Alberta

USGS Publications Warehouse

Meshri, I.D.; Comer, J.B.

1990-01-01

Despite the long history of research which documents many studies involving extensive diagenesis, there are a few examples of a fully documented diagenetic trap. In the context of this paper, a trap is a hydrocarbon-bearing reservoir with a seal; because a reservoir without a seal acts as a carrier bed. The difficulty in the proper documentation of diagenetic traps is often due to the lack of: (a) extensive field records on the perforation and production histories, which assist in providing the depth of separation between hydrocarbon production and non-hydrocarbon or water production; and (b) the simultaneous availability of core data from these intervals, which could be studied for the extent and nature of diagenesis. This paper provides documentation for the existence of a diagenetic trap, based on perforation depths, production histories and petrologic data from the cored intervals, in the context of the geologic and stratigraphic setting. Cores from 15 wells and SP logs from 45 wells were carefully correlated and the data on perforated intervals was also acquired. Extensive petrographic work on the collected cores led to the elucidation of a diagenetic trap that separates water overlying and updip from gas downdip. Amoco's Berrymore-Lobstick-Bigoray fields, located near the northeastern edge of the Alberta Basin, are prolific gas producers. The gas is produced from reservoir rock consisting of delta platform deposits formed by coalescing distributary mouth bars. The overlying rock unit is composed of younger distributary channels; although it has a good reservoir quality, it contains and produces water only. The total thickness of the upper, water-bearing and lower gas-bearing sandstone is about 40 ft. The diagenetic seal is composed of a zone 2 to 6 ft thick, located at the base of distributary channels. This zone is cemented with 20-30% ankerite cement, which formed the gas migration and is also relatively early compared to other cements formed in the water zone. In addition to this barrier to vertical flow, a barrier to lateral flow is formed by the merging of the upper sandstone containing 14% kaolinite and the lower sandstone containing 20% siderite. The measured core permeabilities in these zones vary from 0.0002 to 0.001 milli-darcies. This spatial configuration of diagenetic cements causing porous and non-porous zones is a result of the process of geochemical self-organization. The spatial and temporal patterns of diagenesis are a complex result of coupling of natural processes involving fluid flow, fluid composition, mineral composition and mineral dissolution rates under the conditions of varying pressure and temperature in the subsurface. ?? 1990.

Ground-water data for Georgia, 1983

USGS Publications Warehouse

Clarke, J.S.; Peck, M.F.; Longsworth, S.A.; McFadden, K.W.

1984-01-01

Continuous water-level records from 134 wells and more than 700 water-level measurements made in Georgia during 1983 provide the basic data for this report. Selected wells illustrate the effects that changes in recharge and pumping have had on the various ground-water resources in the State. Daily mean water levels are shown in hydrographs for 1983. Monthly means are shown for the 10-year period 1974-83. Mean annual water levels ranged from 9 feet higher to 6 feet lower in 1983 than in 1982. Water-quality samples are collected periodically throughout Georgia and analyzed as part of areal and regional ground-water studies. Along the coast, chloride concentrations in the upper and lower water-bearing zones of the Floridan aquifer system generally remained steady in the Brunswick and Hilton Head Island areas. (USGS)

Identification of water-bearing zones by the use of geophysical logs and borehole television surveys, collected February to September 1997, at the Former Naval Air Warfare Center, Warminster, Bucks County, Pennsylvania

USGS Publications Warehouse

Conger, Randall W.

1998-01-01

Between February 1997 and September 1997, 10 monitor wells were drilled near the site of the former Naval Air Warfare Center, Warminster, Bucks County, Pa., to monitor water levels and sample ground-water contaminants in the shallow, intermediate, and deep water-bearing zones. The sampling will determine the horizontal and vertical distribution of contaminated ground water migrating from known or suspected contaminant sources. Four wells were drilled north of the property adjacent to Area A, three wells along strike located on Lewis Drive, and three wells directly down dip on Ivyland Road. Well depths range from 69 feet to 300 feet below land surface.Borehole-geophysical logging and television surveys were used to identify water-bearing zones so that appropriate intervals could be screened in each monitor well. Geophysical logs were obtained at the 10 monitor wells. Borehole television surveys were obtained at the four monitor wells adjacent to Area A.Caliper and borehole television surveys were used to locate fractures, inflections on fluidtemperature and fluid-resistivity logs were used to locate possible water-bearing fractures, and heatpulse- flowmeter measurements verified these locations. Natural-gamma logs provided information on stratigraphy. After interpretation of geophysical logs, borehole television surveys, and driller's logs, all wells were screened such that water-level fluctuations could be monitored and water samples collected from discrete water-bearing zones in each borehole.

Chemical Constituents in Groundwater from Multiple Zones in the Eastern Snake River Plain Aquifer at the Idaho National Laboratory, Idaho, 2005-08

USGS Publications Warehouse

Bartholomay, Roy C.; Twining, Brian V.

2010-01-01

From 2005 to 2008, the U.S. Geological Survey's Idaho National Laboratory (INL) Project office, in cooperation with the U.S. Department of Energy, collected water-quality samples from multiple water-bearing zones in the eastern Snake River Plain aquifer. Water samples were collected from six monitoring wells completed in about 350-700 feet of the upper part of the aquifer, and the samples were analyzed for major ions, selected trace elements, nutrients, selected radiochemical constituents, and selected stable isotopes. Each well was equipped with a multilevel monitoring system containing four to seven sampling ports that were each isolated by permanent packer systems. The sampling ports were installed in aquifer zones that were highly transmissive and that represented the water chemistry of the top four to five model layers of a steady-state and transient groundwater-flow model. The model's water chemistry and particle-tracking simulations are being used to better define movement of wastewater constituents in the aquifer. The results of the water chemistry analyses indicated that, in each of four separate wells, one zone of water differed markedly from the other zones in the well. In four wells, one zone to as many as five zones contained radiochemical constituents that originated from wastewater disposal at selected laboratory facilities. The multilevel sampling systems are defining the vertical distribution of wastewater constituents in the eastern Snake River Plain aquifer and the concentrations of wastewater constituents in deeper zones in wells Middle 2051, USGS 132, and USGS 103 support the concept of groundwater flow deepening in the southwestern part of the INL.

Sea Level and Paleoenvironment Control on Late Ordovician Source Rocks, Hudson Bay Basin, Canada

NASA Astrophysics Data System (ADS)

Zhang, S.; Hefter, J.

2009-05-01

Hudson Bay Basin is one of the largest Paleozoic sedimentary basins in North America, with Southampton Island on its north margin. The lower part of the basin succession comprises approximately 180 to 300 m of Upper Ordovician strata including Bad Cache Rapids and Churchill River groups and Red Head Rapids Formation. These units mainly comprise carbonate rocks consisting of alternating fossiliferous limestone, evaporitic and reefal dolostone, and minor shale. Shale units containing extremely high TOC, and interpreted to have potential as petroleum source rocks, were found at three levels in the lower Red Head Rapids Formation on Southampton Island, and were also recognized in exploration wells from the Hudson Bay offshore area. A study of conodonts from 390 conodont-bearing samples from continuous cores and well cuttings from six exploration wells in the Hudson Bay Lowlands and offshore area (Comeault Province No. 1, Kaskattama Province No. 1, Pen Island No. 1, Walrus A-71, Polar Bear C-11 and Narwhal South O-58), and about 250 conodont-bearing samples collected from outcrops on Southampton Island allows recognition of three conodont zones in the Upper Ordovician sequence, namely (in ascendant sequence) Belodina confluens, Amorphognathus ordovicicus, and Rhipidognathus symmetricus zones. The three conodont zones suggest a cycle of sea level changes of rising, reaching the highest level, and then falling during the Late Ordovician. Three intervals of petroleum potential source rock are within the Rhipidognathus symmetricus Zone in Red Head Rapids Formation, and formed in a restricted anoxic and hypersaline condition during a period of sea level falling. This is supported by the following data: 1) The conodont Rhipidognathus symmetricus represents the shallowest Late Ordovician conodont biofacies and very shallow subtidal to intertidal and hypersaline condition. This species has the greatest richness within the three oil shale intervals to compare other parts of Red Head Rapids Formation. 2) Type I kerogen is normally formed in quiet, oxygen-deficient, shallow water environment. Rock-Eval6 data from 40 samples of the three oil shale intervals, collected from outcrops on Southampton Island, demonstrate that the proportion of Type I kerogen gradually increases in the mixed Type I-Type II kerogen from the lower to upper oil shale intervals. 3) Pristane/phytane ratio can be used as a paleoenvironment indicator. The low ratios in the three oil shale intervals range from 0.5 to 0.9 and indicate anoxic and hypersaline conditions. In addition, the presence of isorenieratene derivatives from green phototrophic sulfur bacteria (Chlorobiaceae), with highest relative concentrations in the lower oil shale intervals, points to anoxia reaching into the photic zone of the water column.

Integrated geophysical application to investigate groundwater potentiality of the shallow Nubian aquifer at northern Kharga, West

NASA Astrophysics Data System (ADS)

Younis, Abdellatif; Soliman, Mamdouh; Moussa, Salah; Massoud, Usama; ElNabi, Sami Abd; Attia, Magdy

2016-06-01

Continuous evaluation of groundwater aquifers in the basin of Kharga Oasis is very important. Groundwater in Kharga Oasis represents the major factor for the development plans of this area as it is the sole source for water supplies required for drinking and irrigation purposes. This study is concerned by analyzing the groundwater potentiality of the shallow aquifer at the northern part of Kharga basin by integrated application of Vertical Electrical Sounding (VES) and Time domain Electromagnetic (TEM) techniques. The VES data were measured at 28 points arranged along a north-south trending line by applying Schlumberger array with a maximum current-electrode spacing (AB) of 1000 m. The TEM data were measured at 167 points arranged along 11 east-west trending lines by using a single square loop with 50 m loop-side length. The VES and TEM data have been individually inverted, where the VES models were used as initial models for TEM data inversion. The final models were used for construction of 17 geoelectrical sections and 5 contour maps describing subsurface water-bearing layers at the investigated area. Correlation of the obtained models with geologic, hydrogeologic and borehole information indicates that the shallow aquifer comprises two zones (A-up) and (B-down) separated by a highly conductive shale layer. The upper zone (A) is composed of fine to medium sand with thin clay intercalations. It exhibits low to moderate resistivities. This zone was detected at depth values ranging from 10 to 70 m below ground surface (bgs) and shows a thickness of 25-90 m. The lower zone (B) exhibits moderate to high resistivity values with expected good water quality. The upper surface of zone B was detected at 60-165 m depth.

Behavior of uranium under conditions of interaction of rocks and ores with subsurface water

NASA Astrophysics Data System (ADS)

Omel'Yanenko, B. I.; Petrov, V. A.; Poluektov, V. V.

2007-10-01

The behavior of uranium during interaction of subsurface water with crystalline rocks and uranium ores is considered in connection with the problem of safe underground insulation of spent nuclear fuel (SNF). Since subsurface water interacts with crystalline rocks formed at a high temperature, the mineral composition of these rocks and uranium species therein are thermodynamically unstable. Therefore, reactions directed toward the establishment of equilibrium proceed in the water-rock system. At great depths that are characterized by hindered water exchange, where subsurface water acquires near-neutral and reducing properties, the interaction is extremely sluggish and is expressed in the formation of micro- and nanoparticles of secondary minerals. Under such conditions, the slow diffusion redistribution of uranium with enrichment in absorbed forms relative to all other uranium species is realized as well. The products of secondary alteration of Fe- and Ti-bearing minerals serve as the main sorbents of uranium. The rate of alteration of minerals and conversion of uranium species into absorbed forms is slow, and the results of these processes are insignificant, so that the rocks and uranium species therein may be regarded as unaltered. Under reducing conditions, subsurface water is always saturated with uranium. Whether water interacts with rock or uranium ore, the equilibrium uranium concentration in water is only ≤10-8 mol/l. Uraninite ore under such conditions always remains stable irrespective of its age. The stability conditions of uranium ore are quite suitable for safe insulation of SNF, which consists of 95% uraninite (UO2) and is a confinement matrix for all other radionuclides. The disposal of SNF in massifs of crystalline rocks at depths below 500 m, where reducing conditions are predominant, is a reliable guarantee of high SNF stability. Under oxidizing conditions of the upper hydrodynamic zone, the rate of interaction of rocks with subsurface water increases by orders of magnitude and subsurface water is commonly undersaturated with uranium. Uranium absorbed by secondary minerals, particularly by iron hydroxides and leucoxene, is its single stable species under oxidizing conditions. The impact of oxygen-bearing water leads to destruction of uranium ore. This process is realized simultaneously at different hypsometric levels even if the permeability of the medium is variable in both the lateral and vertical directions. As a result, intervals containing uranyl minerals and relics of primary uranium ore are combined in ore-bearing zones with intervals of completely dissolved uranium minerals. A wide halo of elevated uranium contents caused by sorption is always retained at the location of uranium ore entirely destroyed by weathering. Uranium ore commonly finds itself in the aeration zone due to technogenic subsidence of the groundwater table caused by open-pit mining or pumping out of water from underground mines. The capillary and film waters that interact with rocks and ores in this zone are supplemented by free water filtering along fractures when rain falls or snow is thawing. The interaction of uranium ore with capillary water results in oxidation of uraninite, accompanied by loosening of the mineral surface, formation of microfractures, and an increase in solubility with enrichment of capillary water in uranium up to 10-4 mol/l. Secondary U(VI) minerals, first of all, uranyl hydroxides and silicates, replace uraninite, and uranium undergoes local diffusion redistribution with its sorption by secondary minerals of host rocks. The influx of free water facilitates the complete dissolution of primary and secondary uranium minerals, the removal of uranium at the sites of groundwater discharge, and its redeposition under reducing conditions at a greater depth. It is evident that the conditions of the upper hydrodynamic zone and the aeration zone are unfit for long-term insulation of SNF and high-level wastes because, after the failure of containers, the leakage of radionuclides into the environment becomes inevitable.

Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, Warminster Township, Bucks County, Pennsylvania, 2007

USGS Publications Warehouse

Sloto, Ronald A.

2008-01-01

This study was done by the U.S. Geological Survey in cooperation with the U.S. Navy at Area C of the former Naval Air Warfare Center in Warminster Township, Bucks County, Pa., in support of hydrogeological investigations conducted by the Navy to address ground-water contamination in the Stockton Formation. Borehole geophysical logs were collected, heatpulse-flowmeter measurements were made, and borehole television surveys were run in seven boreholes ranging from 31 to 75 feet deep. Caliper logs and borehole television surveys were used to identify fractures and the location of possible water-bearing zones. Heatpulse-flowmeter measurements were used to identify fractures that were water-bearing zones. Natural-gamma and single-point-resistance logs were used to correlate lithology across the area. Elevated concentrations of tetrachloroethylene (PCE) were measured in water samples from wells with water-bearing zones in the interval of the aquifer where monitor well HN-23A is screened. Water samples from wells with water-bearing zones above or below this interval had substantially lower concentrations of PCE. Wells screened in this interval yielded less than 0.5 gallon per minute, indicating that the interval has low permeability; this may account for the small areal extent and slow migration of PCE.

The Middle Jurassic microflora from El Maghara N° 4 borehole, Northern Sinai, Egypt

NASA Astrophysics Data System (ADS)

Mohsen, Sayed Abdel

The coal bearing formation in El Maghara area, northern Sinai, yielded abundant, diverse and generally well preserved spores, pollen and marine microflora. The palynological analysis of the fine clastic sediments in this formation yielded (71) species related to (44) genera. Three different palynological assemblage zones can be distinguished. The sediments which contain lower and the upper assemblage zones bearing the coal seems, were deposited in non-marine (swamp) environment. In the middle assemblage zone few marine microflora can be identified, indicating a coastal near shore marine environment. Compared with other palynologic data obtained from Egypt and other countries, the three described assemblage zones belong to Middle Jurassic (Bathonian) age.

Hydrogeologic framework and salinity distribution of the Floridan aquifer system of Broward County, Florida

USGS Publications Warehouse

Reese, Ronald S.; Cunningham, Kevin J.

2014-01-01

Concerns about water-level decline and seawater intrusion in the surficial Biscayne aquifer, currently the principal source of water supply to Broward County, prompted a study to refine the hydrogeologic framework of the underlying Floridan aquifer system to evaluate its potential as an alternative source of supply. This report presents cross sections that illustrate the stratigraphy and hydrogeology in eastern Broward County; maps of the upper surfaces and thicknesses of several geologic formations or units within the Floridan aquifer system; and maps of two of the potentially productive water-bearing zones within the system, the Upper Floridan aquifer and the Avon Park permeable zone. An analysis of data on rock depositional textures, associated pore networks, and flow zones in the Floridan aquifer system shows that groundwater moves through the system in two ways. These data support a conceptual, dual-porosity model of the system wherein groundwater moves either as concentrated flow in discrete, thin bedding-plane vugs or zones of vuggy megaporosity, or as diffuse flow through rocks with primarily interparticle and moldic-particle porosity. Because considerable exchange of groundwater may occur between the zones of vuggy and matrix-dominated porosity, understanding the distribution of that porosity and flow zone types is important to evaluating the suitability of the several units within the Floridan aquifer system for managing the water through practices such as aquifer storage and recovery (ASR). The salinity of the water in the Floridan aquifer system is highest in the central part of the study area, and lower toward the north and south. Although salinity generally increases with depth, in the western part of the study area a zone of relatively high saline water is perched above water of lower salinity in the underlying Avon Park permeable zone. Overall, the areas of highest salinity in the aquifer system coincide with those with the lowest estimated transmissivity, so that the occurrence of perched saline water in the system may be the consequence of incompletely flushed connate water or intruded seawater. A seismic reflection profile along the Hillsboro Canal, at the northern edge of the study area, shows seven seismic-sag structures that are interpreted as downward deformation of overlying strata into collapsed deep cave systems. These structures may compromise the integrity of the confinement created by the underlying strata by allowing upconing of saline water from depth, which has implications for successful application of ASR and use of the Floridan aquifer system as an alternative water supply.

A progress report on results of test drilling and ground-water investigations of the Snake Plain aquifer, southeastern Idaho: Part 1: Mud Lake Region, 1969-70 and Part 2: Observation Wells South of Arco and West of Aberdeen

USGS Publications Warehouse

Crosthwaite, E.G.

1973-01-01

The results of drilling test holes to depths of approximately 1,000 feet in the Mud Lake region show that a large part of the region is underlain by both sedimentary deposits and basalt flows. At some locations, predominantly sedimentary deposits were penetrated; at others, basalt flows predominated. The so-called Mud Lake-Market Lake barrier denotes a change in geology. From the vicinity of the barrier area, as described by Stearns, Crandall, and Steward (1938, p. 111), up the water-table gradient for at least a few tens of miles, the saturated geologic section consists predominantly of beds of sediments that are intercalated with numerous basalt flows. Downgradient from the barrier, sedimentary deposits are not common and practically all the water-bearing formations are basalt, at least to the depths explored so far. Thus, the barrier is a transition zone from a sedimentary-basaltic sequence to a basaltic sequence. The sedimentary-basaltic sequence forms a complex hydrologic system in which water occurs under water-table conditions in the upper few tens of feet of saturated material and under artesian conditions in the deeper material in the southwest part of the region. The well data indicate that southwest of the barrier, artesian pressures are not significant. Southwest of the barrier, few sedimentary deposits occur in the basalt section and, as described by Mundorff, Crosthwaite, and Kilburn (1964). ground water occurs in a manner typical of the Snake Plain aquifer. In several wells, artesian pressures are higher in the deeper formations than in the shallower ones, but the reverse was found in a few wells. The available data are not adequate to describe the water-bearing characteristics of the artesian aquifer nor the effects that pumping in one zone would have on adjacent zones. The water-table aquifer yields large quantities of water to irrigation wells.

Seabed fluid expulsion along the upper slope and outer shelf of the U.S. Atlantic continental margin

USGS Publications Warehouse

Brothers, D.S.; Ruppel, C.; Kluesner, J.W.; ten Brink, Uri S.; Chaytor, J.D.; Hill, J.C.; Andrews, B.D.; Flores, C.

2014-01-01

Identifying the spatial distribution of seabed fluid expulsion features is crucial for understanding the substrate plumbing system of any continental margin. A 1100 km stretch of the U.S. Atlantic margin contains more than 5000 pockmarks at water depths of 120 m (shelf edge) to 700 m (upper slope), mostly updip of the contemporary gas hydrate stability zone (GHSZ). Advanced attribute analyses of high-resolution multichannel seismic reflection data reveal gas-charged sediment and probable fluid chimneys beneath pockmark fields. A series of enhanced reflectors, inferred to represent hydrate-bearing sediments, occur within the GHSZ. Differential sediment loading at the shelf edge and warming-induced gas hydrate dissociation along the upper slope are the proposed mechanisms that led to transient changes in substrate pore fluid overpressure, vertical fluid/gas migration, and pockmark formation.

The maximum water storage capacities in nominally anhydrous minerals in the mantle transition zone and lower mantle

NASA Astrophysics Data System (ADS)

Inoue, T.; Yurimoto, H.

2012-12-01

Water is the most important volatile component in the Earth, and affects the physicochemical properties of mantle minerals, e.g. density, elastic property, electrical conductivity, thermal conductivity, rheological property, melting temperature, melt composition, element partitioning, etc. So many high pressure experiments have been conducted so far to determine the effect of water on mantle minerals. To clarify the maximum water storage capacity in nominally anhydrous mantle minerals in the mantle transition zone and lower mantle is an important issue to discuss the possibility of the existence of water reservoir in the Earth mantle. So we have been clarifying the maximum water storage capacity in mantle minerals using MA-8 type (KAWAI-type) high pressure apparatus and SIMS (secondary ion mass spectroscopy). Upper mantle mineral, olivine can contain ~0.9 wt% H2O in the condition just above 410 km discontinuity in maximum (e.g. Chen et al., 2002; Smyth et al., 2006). On the other hand, mantle transition zone mineral, wadsleyite and ringwoodite can contain significant amount (about 2-3 wt.%) of H2O (e.g. Inoue et al., 1995, 1998, 2010; Kawamoto et al., 1996; Ohtani et al., 2000). But the lower mantle mineral, perovskite can not contain significant amount of H2O, less than ~0.1 wt% (e.g. Murakami et al., 2002; Inoue et al., 2010). In addition, garnet and stishovite also can not contain significant amount of H2O (e.g. Katayama et al., 2003; Mookherjee and Karato, 2010; Litasov et al., 2007). On the other hand, the water storage capacities of mantle minerals are supposed to be significantly coupled with Al by a substitution with Mg2+, Si4+ or Mg2+ + Si4+, because Al3+ is the trivalent cation, and H+ is the monovalent cation. To clarify the degree of the substitution, the water contents and the chemical compositions of Al-bearing minerals in the mantle transition zone and the lower mantle were also determined in the Al-bearing systems with H2O. We will introduce the recent results on the maximum water storage capacities in nominally anhydrous minerals in the mantle transition zone and lower mantle from the high pressure experimental point of view.

Evaluation of geophysical logs, Phase II, November 1998 to May 1999, at Crossley Farms Superfund Site, Berks County, Pennsylvania

USGS Publications Warehouse

Conger, Randall W.

2000-01-01

Between November 1998 and May 1999, geophysical logging was conducted in 29 boreholes at the Crossley Farms Superfund Site, Hereford Township, Berks County, Pa., to determine the fluidproducing zones, fluid-receiving zones, zones of vertical borehole flow, and casing depth. The wells range in depth from 96 to 500 feet below land surface. Gamma logs only were collected in three bedrock wells. The geophysical logging determined the placement of well screens and packers, which allow monitoring and sampling of water-bearing zones in the fractured bedrock so that the horizontal and vertical distribution of contaminated ground water migrating from known sources could be determined. Geophysical logging included collection of caliper, video, fluid-temperature, fluid-resistivity, single-point-resistance, natural-gamma, fluid-flow, and acoustic-televiewer logs. Caliper and video logs were used to locate fractures, joints, and weathered zones. Inflections on fluidtemperature and fluid-resistivity logs indicated possible water-bearing fractures, and flowmeter measurements verified these locations. Single-point-resistance and natural-gamma logs provided information on stratigraphy. After interpretation of geophysical, video logs, and drillers notes, 24 of the wells were reconstructed such that water levels can be monitored and water samples collected from discrete water-bearing fractures in each well.

33 CFR 165.T08-0315 - Safety Zone; Upper Mississippi River, Mile 183.0 to 183.5.

Code of Federal Regulations, 2012 CFR

2012-07-01

... River, Mile 183.0 to 183.5. 165.T08-0315 Section 165.T08-0315 Navigation and Navigable Waters COAST... Guard District § 165.T08-0315 Safety Zone; Upper Mississippi River, Mile 183.0 to 183.5. (a) Location. The following area is a safety zone: All waters of the Upper Mississippi River, mile 183.0 to 183.5...

40 CFR 146.32 - Construction requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... during drillings. (c) Where the injection zone is a formation which is naturally water-bearing the... characteristics of the formation fluids. (d) Where the injection formation is not a water-bearing formation, the... Section 146.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER PROGRAMS...

Evaluation of borehole geophysical logs at the Sharon Steel Farrell Works Superfund site, Mercer County, Pennsylvania

USGS Publications Warehouse

McAuley, Steven D.

2004-01-01

On April 14?15, 2003, geophysical logging was conducted in five open-borehole wells in and adjacent to the Sharon Steel Farrell Works Superfund Site, Mercer County, Pa. Geophysical-logging tools used included caliper, natural gamma, single-point resistance, fluid temperature, and heatpulse flowmeter. The logs were used to determine casing depth, locate subsurface fractures, identify water-bearing fractures, and identify and measure direction and rate of vertical flow within the borehole. The results of the geophysical logging were used to determine the placement of borehole screens, which allows monitoring of water levels and sampling of water-bearing zones so that the U.S. Environmental Protection Agency can conduct an investigation of contaminant movement in the fractured bedrock. Water-bearing zones were identified in three of five boreholes at depths ranging from 46 to 119 feet below land surface. Borehole MR-3310 (MW03D) showed upward vertical flow from 71 to 74 feet below land surface to a receiving zone at 63-68 feet below land surface, permitting potential movement of ground water, and possibly contaminants, from deep to shallow zones. No vertical flow was measured in the other four boreholes.

Evaluation of borehole geophysical and video logs, at Butz Landfill Superfund Site, Jackson Township, Monroe County, Pennsylvania

USGS Publications Warehouse

Low, Dennis J.; Conger, Randall W.

2001-01-01

Between February 1996 and November 2000, geophysical logging was conducted in 27 open borehole wells in and adjacent to the Butz Landfill Superfund Site, Jackson Township, Monroe County, Pa., to determine casing depth and depths of water-producing zones, water-receiving zones, and zones of vertical borehole flow. The wells range in depth from 57 to 319 feet below land surface. The geophysical logging determined the placement of well screens and packers, which allow monitoring and sampling of water-bearing zones in the fractured bedrock so that the horizontal and vertical distribution of contaminated ground water migrating from known sources could be determined. Geophysical logging included collection of caliper, natural-gamma, single-point-resistance, fluid-resistivity, fluid-temperature, and video logs. Caliper and video logs were used to locate fractures, joints, and weathered zones. Inflections on single-point-resistance, fluid-temperature, and fluid-resistivity logs indicated possible water-bearing fractures, and heatpulse-flowmeter measurements verified these locations. Natural-gamma logs provided information on stratigraphy.

Hydrogeology and water quality of the Floridan aquifer system and effect of Lower Floridan aquifer withdrawals on the Upper Floridan aquifer at Barbour Pointe Community, Chatham County, Georgia, 2013

USGS Publications Warehouse

Gonthier, Gerard; Clarke, John S.

2016-06-02

Two test wells were completed at the Barbour Pointe community in western Chatham County, near Savannah, Georgia, in 2013 to investigate the potential of using the Lower Floridan aquifer as a source of municipal water supply. One well was completed in the Lower Floridan aquifer at a depth of 1,080 feet (ft) below land surface; the other well was completed in the Upper Floridan aquifer at a depth of 440 ft below land surface. At the Barbour Pointe test site, the U.S. Geological Survey completed electromagnetic (EM) flowmeter surveys, collected and analyzed water samples from discrete depths, and completed a 72-hour aquifer test of the Floridan aquifer system withdrawing from the Lower Floridan aquifer.Based on drill cuttings, geophysical logs, and borehole EM flowmeter surveys collected at the Barbour Pointe test site, the Upper Floridan aquifer extends 369 to 567 ft below land surface, the middle semiconfining unit, separating the two aquifers, extends 567 to 714 ft below land surface, and the Lower Floridan aquifer extends 714 to 1,056 ft below land surface.A borehole EM flowmeter survey indicates that the Upper Floridan and Lower Floridan aquifers each contain four water-bearing zones. The EM flowmeter logs of the test hole open to the entire Floridan aquifer system indicated that the Upper Floridan aquifer contributed 91 percent of the total flow rate of 1,000 gallons per minute; the Lower Floridan aquifer contributed about 8 percent. Based on the transmissivity of the middle semiconfining unit and the Floridan aquifer system, the middle semiconfining unit probably contributed on the order of 1 percent of the total flow.Hydraulic properties of the Upper Floridan and Lower Floridan aquifers were estimated based on results of the EM flowmeter survey and a 72-hour aquifer test completed in Lower Floridan aquifer well 36Q398. The EM flowmeter data were analyzed using an AnalyzeHOLE-generated model to simulate upward borehole flow and determine the transmissivity of water-bearing zones. Aquifer-test data were analyzed with a two-dimensional, axisymmetric, radial, transient, groundwater-flow model using MODFLOW–2005. The flowmeter-survey and aquifer-test simulations provided an estimated transmissivity of about 60,000 square feet per day for the Upper Floridan aquifer and about 5,000 square feet per day for the Lower Floridan aquifer.Water in discrete-depth samples collected from the Upper Floridan aquifer, middle semiconfining unit, and Lower Floridan aquifer during the EM flowmeter survey in August 2013 was low in dissolved solids. Tested constituents were in concentrations within established U.S. Environmental Protection Agency drinking water-quality criteria. Concentrations of measured constituents in water samples from Lower Floridan aquifer well 36Q398 collected at the end of the 72-hour aquifer test in November 2013 were generally higher than in the discrete-depth samples collected during EM flowmeter testing in August 2013 but remained within established drinking water-quality criteria.Water-level data for the aquifer test were filtered for external influences such as barometric pressure, earth-tide effects, and long-term trends to enable detection of small (less than 1 ft) water-level responses to aquifer-test withdrawal. During the 72-hour aquifer test, the Lower Floridan aquifer was pumped at a rate of 750 gallons per minute resulting in a drawdown response of 35.5 ft in the pumped well; 1.6 ft in the Lower Floridan aquifer observation well located about 6,000 ft west of the pumped well; and responses of 0.7, 0.6, and 0.4 ft in the Upper Floridan aquifer observation wells located about 36 ft, 6,000 ft, and 6,800 ft from the pumped well, respectively

Hydrogeologic framework of the shallow ground-water system in the Cox Hall Creek basin, Cape May County, New Jersey

USGS Publications Warehouse

Lacombe, Pierre J.; Zapecza, Otto S.

2006-01-01

Cape May County is investigating the feasibility of restoring the lowermost reach of Cox Hall Creek to its former state as a tidal saltwater wetland; however, the potential for contamination of the shallow ground-water system, which provides water to hundreds of nearby privately owned domestic wells, with saltwater from the restored wetland is of particular concern. To evaluate the potential effectiveness and risks of restoring the saltwater wetlands, the County needs information about the hydrogeologic framework in the area, and about the potential vulnerability of the domestic wells to contamination. The shallow ground-water system in the Cox Hall Creek area consists of unconsolidated Holocene and Pleistocene deposits. The Holly Beach water-bearing zone, the unconfined (water-table) aquifer, is about 35 feet thick and contains a 2- to 4-foot-thick clay lens about 10 feet below land surface; a lower, more discontinuous clay lens about 30 to 35 feet below land surface ranges up to 5 feet in thickness. A 75-foot-thick confining unit separates the Holly Beach water-bearing zone from the underlying estuarine sand aquifer. The clay lenses in the Holly Beach water-bearing zone likely retard the movement of contaminants from septic tanks, lawns, and other surficial sources, protecting wells that tap the lower, sandy part of the aquifer. The clay lenses also may protect these wells from salty surface water if withdrawals from the Holly Beach water-bearing zone are not increased substantially. Deeper wells that tap the estuarine sand aquifer are more effectively protected from saltwater from surface sources because of the presence of the overlying confining unit.

Hydrogeology and the distribution of salinity in the Floridan aquifer system, Palm Beach County, Florida

USGS Publications Warehouse

Reese, R.S.; Memberg, S.J.

2000-01-01

The virtually untapped Floridan aquifer system is considered to be a supplemental source of water for public use in the highly populated coastal area of Palm Beach County. A recent study was conducted to delineate the distribution of salinity in relation to the local hydrogeology and assess the potential processes that might control (or have affected) the distribution of salinity in the Floridan aquifer system. The Floridan aquifer system in the study area consists of the Upper Floridan aquifer, middle confining unit, and Lower Floridan aquifer and ranges in age from Paleocene to Oligocene. Included at its top is part of a lowermost Hawthorn Group unit referred to as the basal Hawthorn unit. The thickness of this basal unit is variable, ranging from about 30 to 355 feet; areas where this unit is thick were paleotopographic lows during deposition of the unit. The uppermost permeable zones in the Upper Floridan aquifer occur in close association with an unconformity at the base of the Hawthorn Group; however, the highest of these zones can be up in the basal unit. A dolomite unit of Eocene age generally marks the top of the Lower Floridan aquifer, but the top of this dolomite unit has a considerable altitude range: from about 1,200 to 2,300 feet below sea level. Additionally, where the dolomite unit is thick, its top is high and the middle confining unit of the Floridan aquifer system, as normally defined, probably is not present. An upper zone of brackish water and a lower zone of water with salinity similar to that of seawater (saline-water zone) are present in the Floridan aquifer system. The brackish-water and saline-water zones are separated by a transition zone (typically 100 to 200 feet thick) in which salinity rapidly increases with depth. The transition zone was defined by using a salinity of 10,000 mg/L (milligrams per liter) of dissolved-solids concentration (about 5,240 mg/L of chloride concentration) at its top and 35,000 mg/L of dissolved-solids concentration (about 18,900 mg/L of chloride concentration) at its base. The base of the brackish-water zone and the top of the saline-water zone were approximately determined mostly by means of resistivity geophysical logs. The base of the brackish-water zone in the study area ranges from about 1,600 feet below sea level near the coast to almost 2,200 feet below sea level in extreme southwestern Palm Beach County. In an area that is peripheral to Lake Okeechobee, the boundary unexpectedly rises to perhaps as shallow as 1,800 feet below sea level. In an upper interval of the brackish-water zone within the Upper Floridan aquifer, chloride concentration of water ranges from 490 to 8,000 mg/L. Chloride concentration correlates with the altitude of the basal contact of the Hawthorn Group, with concentration increasing as the altitude of this contact decreases. Several areas of anomalous salinity where chloride concentration in this upper interval is greater than 3,000 mg/L occur near the coast. In most of these areas, salinity was found to decrease with depth from the upper interval to a lower interval within the brackish-water zone: a reversal of the normal salinity trend within the zone. These areas are also characterized by an anomalously low altitude of the base of the brackish-water zone, and a much greater thickness of the transition zone than normal. These anomalies could be the result of seawater preferentially invading zones of higher permeability in the Upper Floridan aquifer during Pleistocene high stands of sea level and incomplete flushing of this high salinity water by the present-day flow system.

An interpretation of core and wireline logs for the Petrophysical evaluation of Upper Shallow Marine sandstone reservoirs of the Bredasdorp Basin, offshore South Africa

NASA Astrophysics Data System (ADS)

Magoba, Moses; Opuwari, Mimonitu

2017-04-01

This paper embodies a study carried out to assess the Petrophysical evaluation of upper shallow marine sandstone reservoir of 10 selected wells in the Bredasdorp basin, offshore, South Africa. The studied wells were selected randomly across the upper shallow marine formation with the purpose of conducting a regional study to assess the difference in reservoir properties across the formation. The data sets used in this study were geophysical wireline logs, Conventional core analysis and geological well completion report. The physical rock properties, for example, lithology, fluid type, and hydrocarbon bearing zone were qualitatively characterized while different parameters such as volume of clay, porosity, permeability, water saturation ,hydrocarbon saturation, storage and flow capacity were quantitatively estimated. The quantitative results were calibrated with the core data. The upper shallow marine reservoirs were penetrated at different depth ranging from shallow depth of about 2442m to 3715m. The average volume of clay, average effective porosity, average water saturation, hydrocarbon saturation and permeability range from 8.6%- 43%, 9%- 16%, 12%- 68% , 32%- 87.8% and 0.093mD -151.8mD respectively. The estimated rock properties indicate a good reservoir quality. Storage and flow capacity results presented a fair to good distribution of hydrocarbon flow.

Chloride Concentration in Water from the Upper Permeable Zone of the Tertiary Limestone Aquifer System, Southeastern United States

USGS Publications Warehouse

Sprinkle, Craig L.

1982-01-01

INTRODUCTION The tertiary limestone aquifer system of the southeastern United States is a sequence of carbonate rocks referred to as the Floridan aquifer in Florida and the principal artesian aquifer in Georgia, Alabama, and South Carolina. More than 3 billion gallons of water are pumped daily from the limestone aquifer; and the system is the principal source of municipal, industrial, and agricultural water supply in south Georgia and most of Florida. The aquifer system includes units of Paleocene to early Miocene age that combine to form a continuous carbonate sequence that is hydraulically connected in varying degrees. In a small area near Brunswick, Ga., a thin sequence of rocks of Late Cretaceous age is part of the system. In and directly downdip from much of the outcrop area, the system consists of one continuous permeable unit. Further downdip the aquifer system generally consists of two major permeable zones separated by a less-permeable unit of highly variable hydraulic properties (very leaky to virtually nonleaky). Conditions for the system vary from unconfined to confined depending upon whether the argillaceous Miocene and younger rocks that form the upper confining unit have been removed by erosion. This report is one of a series of preliminary products depicting the hydrogeologic framework, water chemistry, and hydrology of the aquifer system. The map shows the distribution of chloride ions in water from the upper permeable zone of the limestone aquifer system. The upper permeable zone consists of several formations, primarily the Tampa, Suwannee, Ocala, and Avon Park Limestones (Miller 1981a, b). Chloride concentrations of water within the upper permeable zone vary from nearly zero in recharge areas to many thousands of milligrams per liter (mg/L) in coastal discharge areas. Where the aquifer system discharges into the sea, the upper permeable zone contains increasing amounts of seawater. In these areas, wells that fully penetrate the upper permeable zone will yield water with chloride concentrations that approach that of seawater, about 19500 mg/L.

Simulation of the mulltizones clastic reservoir: A case study of Upper Qishn Clastic Member, Masila Basin-Yemen

NASA Astrophysics Data System (ADS)

Khamis, Mohamed; Marta, Ebrahim Bin; Al Natifi, Ali; Fattah, Khaled Abdel; Lashin, Aref

2017-06-01

The Upper Qishn Clastic Member is one of the main oil-bearing reservoirs that are located at Masila Basin-Yemen. It produces oil from many zones with different reservoir properties. The aim of this study is to simulate and model the Qishn sandstone reservoir to provide more understanding of its properties. The available, core plugs, petrophysical, PVT, pressure and production datasets, as well as the seismic structural and geologic information, are all integrated and used in the simulation process. Eclipse simulator was used as a powerful tool for reservoir modeling. A simplified approach based on a pseudo steady-state productivity index and a material balance relationship between the aquifer pressure and the cumulative influx, is applied. The petrophysical properties of the Qishn sandstone reservoir are mainly investigated based on the well logging and core plug analyses. Three reservoir zones of good hydrocarbon potentiality are indicated and named from above to below as S1A, S1C and S2. Among of these zones, the S1A zone attains the best petrophysical and reservoir quality properties. It has an average hydrocarbon saturation of more than 65%, high effective porosity up to 20% and good permeability record (66 mD). The reservoir structure is represented by faulted anticline at the middle of the study with a down going decrease in geometry from S1A zone to S2 zone. It is limited by NE-SW and E-W bounding faults, with a weak aquifer connection from the east. The analysis of pressure and PVT data has revealed that the reservoir fluid type is dead oil with very low gas liquid ratio (GLR). The simulation results indicate heterogeneous reservoir associated with weak aquifer, supported by high initial water saturation and high water cut. Initial oil in place is estimated to be around 628 MM BBL, however, the oil recovery during the period of production is very low (<10%) because of the high water cut due to the fractures associated with many faults. Hence, secondary and tertiary methods are needed to enhance the oil recovery. Water flooding is recommended as the first step of oil recovery enhancement by changing some of high water cut wells to injectors.

Ground-water hydrology of the Chad Basin in Bornu and Dikwa Emirates, northeastern Nigeria, with special emphasis on the flow life of the artesian system

USGS Publications Warehouse

Miller, Raymond E.; Johnston, R.H.; Olowu, J.A.I.; Uzoma, J.U.

1968-01-01

Bornu and Dikwa Emirates lie in the Nigerian sector of the Chad Basin, a vast region of interior drainage encompassing about 600,000 square miles of north-central Africa. The report area includes about 25,000 square miles of the basin that lie in Nigeria. Most of the area is a featureless plain that slopes gently northeast and east from the uplands of central Nigeria towards Lake Chad. On its eastern side the lake has one surface outlet which overflows only during exceptionally high stages of the lake. This outlet spills into the channel of Bahr al Ghazal, which in turn drains into the Bod616 depression. Because the lake is shallow, the shoreline fluctuates markedly with high and low stages corresponding to the wet and dry seasons. The semiarid climate of Bornu and Dikwa Emirates is characterized by a long dry season and a short wet season that correspond to seasonal winds. Annual rainfall ranges from 15 inches in the northern part of the area to 32 inches in the southern. The Chad Basin in Dikwa and Bornu Emirates is underlain by interbedded sand and clay, collectively termed the Chad Formation. These alluvial and lactustrine sediments were deposited in or near Lake Chad whet it occupied a much greater area during Pliocene and Pleistocene time. The Chad Formation has a very slight primary dip in the direction of Lake Chad and conforms to the gentle slope of land surface. The known thickness of the formation ranges from a few feet where it overlies bedrock on the periphery of the basin to at least 1,800 feet at Maiduguri; however, its total thickness probably exceeds 2,000 feet in the central part of the basin. Three water-bearing units termed upper, middle, and lower zones occur within the Chad Formation. The upper zone yields water to numerous dug wells throughout the rural areas and also is .the major source of the Maiduguri municipal water .supply. The middle zone yields water from flowing artesian boreholes that have heads ranging from a few feet to 70 feet above land surface throughout a 13,000 square-mile area of the basin in Nigeria. The lower zone also yields water from flowing boreholes ; however, its areal extent has not been proved beyond the environs of Maiduguri. The present investigation is concerned primarily with the middle zone, which is the source of water for some 190 flowing boreholes used as little-watering points in the Nigerian sector of the Chad Basin. The thickness of loads of waterbearing sand in the middle zone ranges from less than 1 foot to 200 feet, and the artesian head ranges from land surface at Maiduguri to 70 feet above land surface at Lake Chad. The depth to the top of the middle zone in the area of flowing boreholes ranges from 500 to 1,250 feet below land surface. The waterbearing properties of the middle zone differ greatly from place to place. Also, the yields of individual flowing boreholes generally range from 50 to 20,000 imperial gallons per hour (gph). On the basis of water availability, the middle zone can be divided as follows : Areas of high-, moderate-, and low-yield artesian aquifer ; areas of low- and moderate-yield subartesian aquifer ; and an area where the yields from boreholes are insignificant or the aquifer is missing. Recommended maximum rates of long-term withdrawal from individual boreholes for the three artesian areas range from 100 to 5,000 gph with boreholes spaced 5 to 10 miles apart. By limiting flows to the recommended maximum rates, the boreholes should continue to flow for at least 30 years. The present average use per borehole (265 gph in 1965) is considerably less than the recommended maximum rates. Recharge to the upper zone occurs in significant but as yet unmeasured quantities, mostly in the vicinity of the major streams. Apparently, however, no significant amount of recharge reaches the middle zone from the Upper zone. Although the middle zone is, in effect, being 'mined' by existing flowing wells, the present (1965) rate of withdrawal i

A revision of the Norian Conchostracan Zonation in North America and its implications for Late Triassic North American tectonic history

USGS Publications Warehouse

Weems, Robert E.; Lucas, Spencer G.

2015-01-01

Collections of Upper Triassic (Norian) conchostracans from the upper Cumnock and lower Sanford formations (North Carolina), Bull Run Formation (Virginia), Gettysburg Formation (Pennsylvania), Passaic Formation (New Jersey), Blomidon Formation (Nova Scotia), and Redonda Formation (New Mexico) have significantly expanded our knowledge of the Norian conchostracan faunas in these units. These collections show that the temporal and spatial distribution of Norian conchostracans in North America is more complex and more environmentally controlled than previously thought. The new collections require a revision and simplification of the published conchostracan zonation for this interval. The revised zonation, based almost entirely on evolution within the lineage of the conchostracan genus Shipingia, consists of five zones: the Shipingia weemsi-Euestheria buravasi zone (Lacian), the Shipingia mcdonaldi zone (lower Alaunian), the Shipingia hebaozhaiensis zone (upper Alaunian), the Shipingia olseni zone (lower and middle Sevatian), and the Shipingia gerbachmanni zone (upper Sevatian). A new species of Norian conchostracan, Wannerestheria kozuri, is described from the Groveton Member of the Bull Run Formation (Virginia). Two new members (Plum Run and Fairfield members) are named in the Gettysburg Formation (Gettysburg Basin, Maryland and Pennsylvania). The distribution of upper Carnian and Norian strata in the Fundy, Newark, Gettysburg, and Culpeper basins indicates that there was a significant, previously undetected tectonic reorganization within these basins that occurred around the Carnian-Norian boundary. The presence of an upper Norian-lower Rhaetian unconformity within the Newark Supergroup is reaffirmed. A re-evaluation of the conchostracan record from the Redonda Formation of the Chinle Group in New Mexico indicates that the four conchostracan-bearing lacustrine beds in this unit are part of only a single, consistently recognizable conchostracan zone, which we here designate as the Shipingia gerbachmanni zone.

Evaluation of geophysical logs, Phase I, at Willow Grove Naval Air Station, Montgomery County, Pennsylvania

USGS Publications Warehouse

Conger, R.W.

1997-01-01

Between April and June 1997, the U.S. Navy contracted Brown and Root Environmental, Inc., to drill 20 monitor wells at the Willow Grove Naval Air Station in Horsham Township, Montgomery County, Pa. The wells were installed to monitor water levels and allow collection of water samples from shallow, intermediate, and deep water-bearing zones. Analysis of the samples will determine the horizontal and vertical distribution of any contaminated ground water migrating from known contaminant sources. Eight wells were drilled near the Fire Training Area (Site 5), five wells near the 9th Street Landfill (Site 3), four wells at the Antenna Field Landfill (Site 2), and three wells near Privet Road Compound (Site 1). Depths range from 73 to 167 feet below land surface. The U.S. Geological Survey conducted borehole-geophysical and borehole-video logging to identify water-bearing zones so that appropriate intervals could be screened in each monitor well. Geophysical logs were run on the 20 monitor wells and 1 existing well. Video logs were run on 16 wells. Caliper and video logs were used to locate fractures, inflections on fluid-temperature and fluid-resistivity logs were used to locate possible water-bearing fractures, and flowmeter measurements verified these locations. Single-point-resistance and natural-gamma logs provided information on stratigraphy. After interpretation of geophysical logs, video logs, and driller's notes, all wells were screened such that water-level fluctuations could be monitored and discrete water samples collected from one or more shallow and intermediate water-bearing zones in each borehole.

Silurian and Devonian in Vietnam—Stratigraphy and facies

NASA Astrophysics Data System (ADS)

Thanh, Tống Duy; Phương, Tạ Hoàng; Janvier, Philippe; Hùng, Nguyễn Hữu; Cúc, Nguyễn Thị Thu; Dương, Nguyễn Thùy

2013-09-01

Silurian and Devonian deposits in Viet Nam are present in several zones and regions, including Quang Ninh, East Bac Bo, and West Bac Bo Zones of the Bac Bo Region, the Dien Bien-Nghe An and Binh Tri Thien Zones of the Viet-Lao Region, and the South Trung Bo, and Western Nam Bo Zones of the South Viet Nam Region (Fig. 1). The main lithological features and faunal composition of the Silurian and Devonian Units in all these zones are briefly described. The Silurian consists of deep-water deposits of the upper parts of the Co To and Tan Mai Formations in the Quang Ninh Zone, the upper parts of the Phu Ngu Formation in the East Bac Bo Zone and the upper parts of the Long Dai and Song Ca Formations in the Viet-Lao Region. Shallow water facies Silurian units containing benthic faunas are more widely distributed, including the upper part of the Sinh Vinh and Bo Hieng Formations in the West Bac Bo Zone, the Kien An Formation in the Quang Ninh Zone, and, in the Viet-Lao Region, the Dai Giang Formation and the upper part of the Tay Trang Formation. No Lower and Middle Devonian deposits indicate deep water facies, but they are characterized by different shallow water facies. Continental to near shore, deltaic facies characterize the Lower Devonian Song Cau Group in the East Bac Bo Zone, the Van Canh Formation in the Quang Ninh Zone, and the A Choc Formation in the Binh Tri Thien Zone. Similar facies also occur in the Givetian Do Son Formation of the Quang Ninh Zone, and the Tan Lap Formation in the East Bac Bo Zone, and consist of coarse terrigenous deposits—cross-bedded conglomerates, sandstone, etc. Most Devonian units are characterized by shallow marine shelf facies. Carbonate and terrigenous-carbonate facies dominate, and terrigenous facies occur in the Lower and Middle Devonian sections in some areas only. The deep-water-like facies is characteriztic for some Upper Devonian formations in the Bac Bo (Bang Ca and Toc Tat Formations) and Viet-Lao Regions (Thien Nhan and Xom Nha Formations). These formations contain cherty shale or siliceous limestone, and fossils consist of conodonts, but there are also brachiopods and other benthos. They were possibly deposited in a deep water environment on the slope of the continental shelf. Most Devonian units distributed in the North and the Central Viet Nam consist of self shallow water sediments, and apparently they were deposited in a passive marginal marine environment. The coarse clastic continental or subcontinental deposits are distributed only in some areas of the East Bac Bo and of the Quang Ninh zones of the Bac Bo Region, and in the south of the Binh Tri Thien Zone. This situation suggests the influence of the Caledonian movement at the end of the Silurian period that called the Guangxi movement in South China.

Geochemical Monitoring Of The Gas Hydrate Production By CO2/CH4 Exchange In The Ignik Sikumi Gas Hydrate Production Test Well, Alaska North Slope

NASA Astrophysics Data System (ADS)

Lorenson, T. D.; Collett, T. S.; Ignik Sikumi, S.

2012-12-01

Hydrocarbon gases, nitrogen, carbon dioxide and water were collected from production streams at the Ignik Sikumi gas hydrate production test well (TD, 791.6 m), drilled on the Alaska North Slope. The well was drilled to test the feasibility of producing methane by carbon dioxide injection that replaces methane in the solid gas hydrate. The Ignik Sikumi well penetrated a stratigraphically-bounded prospect within the Eileen gas hydrate accumulation. Regionally, the Eileen gas hydrate accumulation overlies the more deeply buried Prudhoe Bay, Milne Point, and Kuparuk River oil fields and is restricted to the up-dip portion of a series of nearshore deltaic sandstone reservoirs in the Sagavanirktok Formation. Hydrate-bearing sandstones penetrated by Ignik Sikumi well occur in three primary horizons; an upper zone, ("E" sand, 579.7 - 597.4 m) containing 17.7 meters of gas hydrate-bearing sands, a middle zone ("D" sand, 628.2 - 648.6 m) with 20.4 m of gas hydrate-bearing sands and a lower zone ("C" sand, 678.8 - 710.8 m), containing 32 m of gas hydrate-bearing sands with neutron porosity log-interpreted average gas hydrate saturations of 58, 76 and 81% respectively. A known volume mixture of 77% nitrogen and 23% carbon dioxide was injected into an isolated section of the upper part of the "C" sand to start the test. Production flow-back part of the test occurred in three stages each followed by a period of shut-in: (1) unassisted flowback; (2) pumping above native methane gas hydrate stability conditions; and (3) pumping below the native methane gas hydrate stability conditions. Methane production occurred immediately after commencing unassisted flowback. Methane concentration increased from 0 to 40% while nitrogen and carbon dioxide concentrations decreased to 48 and 12% respectively. Pumping above the hydrate stability phase boundary produced gas with a methane concentration climbing above 80% while the carbon dioxide and nitrogen concentrations fell to 2 and 18% respectively. Pumping below the gas hydrate stability phase boundary occurred in two periods with the composition of the produced gases continually increasing in methane reaching an excess of 96%, along with carbon dioxide decreasing to <1% and nitrogen to ~3%. The isotopic composition of all the gases was monitored. Methane carbon and hydrogen isotopic compositions remained stable throughout the test, while the carbon dioxide carbon became isotopically heavier. Nitrogen isotopic composition remained stable or became slightly isotopically depleted at the later phase of the test. These results imply that the produced methane was not isotopically fractionated, whereas carbon dioxide was fractionated becoming isotopically heavier at the end of each production phase. In addition, water samples were analyzed during the production phase documenting an increase in salinity.

Hydrogeologic framework and geochemistry of the intermediate aquifer system in parts of Charlotte, De Soto, and Sarasota counties, Florida

USGS Publications Warehouse

Torres, A.E.; Sacks, L.A.; Yobbi, D.K.; Knochenmus, L.A.; Katz, B.G.

2001-01-01

The hydrogeologic framework underlying the 600-square-mile study area in Charlotte, De Soto, and Sarasota Counties, Florida, consists of the surficial aquifer system, the intermediate aquifer system, and the Upper Floridan aquifer. The hydrogeologic framework and the geochemical processes controlling ground-water composition were evaluated for the study area. Particular emphasis was given to the analysis of hydrogeologic and geochemical data for the intermediate aquifer system. Flow regimes are not well understood in the intermediate aquifer system; therefore, hydrogeologic and geochemical information were used to evaluate connections between permeable zones within the intermediate aquifer system and between overlying and underlying aquifer systems. Knowledge of these connections will ultimately help to protect ground-water quality in the intermediate aquifer system. The hydrogeology was interpreted from lithologic and geophysical logs, water levels, hydraulic properties, and water quality from six separate well sites. Water-quality samples were collected from wells located along six ground-water flow paths and finished at different depth intervals. The selection of flow paths was based on current potentiometric-surface maps. Ground-water samples were analyzed for major ions; field parameters (temperature, pH, specific conductance, and alkalinity); stable isotopes (deuterium, oxygen-18, and carbon-13); and radioactive isotopes (tritium and carbon-14). The surficial aquifer system is the uppermost aquifer, is unconfined, relatively thin, and consists of unconsolidated sand, shell, and limestone. The intermediate aquifer system underlies the surficial aquifer system and is composed of clastic sediments interbedded with carbonate rocks. The intermediate aquifer system is divided into three permeable zones, the Tamiami/Peace River zone (PZ1), the Upper Arcadia zone (PZ2), and the Lower Arcadia zone (PZ3). The Tamiami/Peace River zone (PZ1) is the uppermost zone and is the thinnest and generally, the least productive zone in the intermediate aquifer system. The Upper Arcadia zone (PZ2) is the middle zone and productivity is generally higher than the overlying permeable zone. The Lower Arcadia zone (PZ3) is the lowermost permeable zone and is the most productive zone in the intermediate aquifer system. The intermediate aquifer system is underlain by the Upper Floridan aquifer, which consists of a thick, stratified sequence of limestone and dolomite. The Upper Floridan aquifer is the most productive aquifer in the study area; however, its use is generally restricted because of poor water quality. Interbedded clays and fine-grained clastics separate the aquifer systems and permeable zones. The hydraulic properties of the three aquifer systems are spatially variable. Estimated trans-missivity and horizontal hydraulic conductivity varies from 752 to 32,900 feet squared per day and from 33 to 1,490 feet per day, respectively, for the surficial aquifer system; from 47 to 5,420 feet squared per day and from 2 to 102 feet per day, respectively, for the Tamiami/Peace River zone (PZ1); from 258 to 24,633 feet squared per day and from 2 to 14 feet per day, respectively, for the Upper Arcadia zone (PZ2); from 766 to 44,900 feet squared per day and from 10 to 201 feet per day, respectively, for the Lower Arcadia zone (PZ3); and from 2,350 to 7,640 feet squared per day and from 10 to 41 feet per day, respectively, for the Upper Floridan aquifer. Confining units separating the aquifer systems have leakance coefficients estimated to range from 2.3 x 10-5 to 5.6 x 10-3 feet per day per foot. Strata composing the confining unit separating the Upper Floridan aquifer from the intermediate aquifer system are substantially more permeable than confining units separating the permeable zones in the intermediate aquifer system or separating the surficial aquifer and intermediate aquifer systems. In Charlotte, Sarasota, and western De Soto Counties, hydraulic

Impact of Reservoir Fluid Saturation on Seismic Parameters: Endrod Gas Field, Hungary

NASA Astrophysics Data System (ADS)

El Sayed, Abdel Moktader A.; El Sayed, Nahla A.

2017-12-01

Outlining the reservoir fluid types and saturation is the main object of the present research work. 37 core samples were collected from three different gas bearing zones in the Endrod gas field in Hungary. These samples are belonging to the Miocene and the Upper - Lower Pliocene. These samples were prepared and laboratory measurements were conducted. Compression and shear wave velocity were measured using the Sonic Viewer-170-OYO. The sonic velocities were measured at the frequencies of 63 and 33 kHz for compressional and shear wave respectively. All samples were subjected to complete petrophysical investigations. Sonic velocities and mechanical parameters such as young’s modulus, rigidity, and bulk modulus were measured when samples were saturated by 100%-75%-0% brine water. Several plots have been performed to show the relationship between seismic parameters and saturation percentages. Robust relationships were obtained, showing the impact of fluid saturation on seismic parameters. Seismic velocity, Poisson’s ratio, bulk modulus and rigidity prove to be applicable during hydrocarbon exploration or production stages. Relationships among the measured seismic parameters in gas/water fully and partially saturated samples are useful to outline the fluid type and saturation percentage especially in gas/water transitional zones.

Radial Anisotropy in the Mantle Transition Zone and Its Implications

NASA Astrophysics Data System (ADS)

Chang, S. J.; Ferreira, A. M.

2016-12-01

Seismic anisotropy is a useful tool to investigate mantle flow, mantle convection, and the presence of melts in mantle, since it provides information on the direction of mantle flow or the orientation of melts by combining it with laboratory results in mineral physics. Although the uppermost and lowermost mantle with strong anisotropy have been well studied, anisotropic properties of the mantle transition zone is still enigmatic. We use a recent global radially anisotropic model, SGLOBE-rani, to examine the patterns of radial anisotropy in the mantle transition zone. Strong faster SV velocity anomalies are found in the upper transition zone beneath subduction zones in the western Pacific, which decrease with depth, thereby nearly isotropic in the lower transition zone. This may imply that the origin for the anisotropy is the lattice-preferred orientation of wadsleyite, the dominant anisotropic mineral in the upper transition zone. The water content in the upper transition zone may be inferred from radial anisotropy because of the report that anisotropic intensity depends on the water content in wadsleyite.

Global Transition Zone Anisotropy and Consequences for Mantle Flow and Earth's Deep Water Cycle

NASA Astrophysics Data System (ADS)

Beghein, C.; Yuan, K.

2011-12-01

The transition zone has long been at the center of the debate between multi- and single-layered convection models that directly relate to heat transport and chemical mixing throughout the mantle. It has also been suggested that the transition zone is a reservoir that collects water transported by subduction of the lithosphere into the mantle. Since water lowers mantle minerals density and viscosity, thereby modifying their rheology and melting behavior, it likely affects global mantle dynamics and the history of plate tectonics. Constraining mantle flow is therefore important for our understanding of Earth's thermochemical evolution and deep water cycle. Because it can result from deformation by dislocation creep during convection, seismic anisotropy can help us model mantle flow. It is relatively well constrained in the uppermost mantle, but its presence in the transition zone is still debated. Its detection below 250 km depth has been challenging to date because of the poor vertical resolution of commonly used datasets. In this study, we used global Love wave overtone phase velocity maps, which are sensitive to structure down to much larger depths than fundamental modes alone, and have greater depth resolution than shear wave-splitting data. This enabled us to obtain a first 3-D model of azimuthal anisotropy for the upper 800km of the mantle. We inverted the 2Ψ terms of anisotropic phase velocity maps [Visser, et al., 2008] for the first five Love wave overtones between 35s and 174s period. The resulting model shows that the average anisotropy amplitude for vertically polarized shear waves displays two main stable peaks: one in the uppermost mantle and, most remarkably, one in the lower transition zone. F-tests showed that the presence of 2Ψ anisotropy in the transition zone is required to improve the third, fourth, and fifth overtones fit. Because of parameter trade-offs, however, we cannot exclude that the anisotropy is located in the upper transition zone as well. Azimuthal anisotropy in the transition zone could result from tilted laminated structures, or from the LPO of wadsleyite and hydrous ringwoodite. Anhydrous ringwoodite is mostly isotropic, but it becomes more anisotropic in the presence of water [Kavner, 2003]. The presence of significant seismic anisotropy in the lower transition zone may thus indicate the presence of OH--bearing minerals. This would be consistent with the observed high solubility of water in ringwoodite and wadsleyite, and the hypothesis that the transition zone is a water reservoir. In addition, at most locations the fast azimuth of propagation for Vsv forms approximately a 90° angle in the transition zone with the fast direction found at shallower depths. Assuming that LPO causes the anisotropy and that seismic fast directions are a proxy for flow direction in the transition zone, this angle change combined with mineral physics data could help us infer mantle convective pattern. The robustness of this feature is, however, currently difficult to assess as Love wave overtones are unable to reliably constrain 2Ψ anisotropy at shallow depths. The inclusion of Rayleigh wave fundamental mode data in future work will help resolve that issue.

Performance of a mixed-waste landfill amid geologic uncertainty—learning from a case study: Altamont Hills, California, U.S.A.

NASA Astrophysics Data System (ADS)

Taffet, Michael J.; Lamarre, Albert L.; Oberdorfer, June A.

1991-11-01

This paper presents a case study that illustrates how geologic factors, which are not always obvious without extensive study, may hamper later landfill performance. The site is Lawrence Livermore National Laboratory (LLNL) site 300. Two unlined landfills, opened in 1958, and 1968, contain small amounts of tritium, uranium-238, lead, and beryllium in a vast proportion of inert materials (gravel, wood, and plastic). Groundwater analyses indicate that tritium at activities up to 600,000 picoCuries per liter (pCi/l) is present in two plumes beneath and adjacent to the landfills within a perched water-bearing zone. The affected water-bearing zone averages 2 m in thickness and occurs within the late Miocene Neroly Formation, which is composed of feldspathic sandstones and siltstones and interbedded claystones and conglomerates. Scanning election microscopy (SEM) analysis indicates that diagenetic clays have occluded the porosity of much of the sandstones. However, abundant fractures appear to provide permeability. Depth to the water table fluctuates greatly beneath the site but averages about 10 m. In the past, following heavy rains, groundwater levels rose into the landfill bottoms and mobilized the tritium. Rapid recharge and rise of water levels appear to have been enhanced by the funnelling of surface water by topography, direct infiltration through fractures and permeable landfill materials, and the low permeability of the geologic materials that comprise the water-bearing zone. These and other hydrogeologic conditions contributed to groundwater contact with landfill materials but were not known before landfill construction. Such information is important for siting landfills in the current regulatory environment. Contaminant transport modeling indicates that even if the perched water-bearing zone were continuous to the site 300 boundary, tritium activities would undergo radioactive decay to background levels by the time the tritiated water could reach the site boundary.

Hydrologeology and water quality of the Floridan aquifer system and effect of Lower Floridan aquifer pumping on the Upper Floridan aquifer, Pooler, Chatham County, Georgia, 2011–2012

USGS Publications Warehouse

Gonthier, Gerard

2012-01-01

Two test wells were completed in Pooler, Georgia, in 2011 to investigate the potential of using the Lower Floridan aquifer as a source of water for municipal use. One well was completed in the Lower Floridan aquifer at a depth of 1,120 feet (ft) below land surface; the other well was completed in the Upper Floridan aquifer at a depth of 486 ft below land surface. At the Pooler test site, the U.S. Geological Survey performed flowmeter surveys, packer-isolated slug tests within the Lower Floridan confining unit, slug tests of the entire Floridan aquifer system, and aquifer tests of the Upper and Lower Floridan aquifers. Drill cuttings, geophysical logs, and borehole flowmeter surveys indicate that the Upper Floridan aquifer extends 333 –515 ft below land surface, the Lower Floridan confining unit extends 515–702 ft below land surface, and the Lower Floridan aquifer extends 702–1,040 ft below land surface. Flowmeter surveys indicate that the Upper Floridan aquifer contains two water-bearing zones at depth intervals of 339 –350 and 375–515 ft; the Lower Floridan confining unit contains one zone at a depth interval of 550–620 ft; and the Lower Floridan aquifer contains five zones at depth intervals of 702–745, 745–925, 925–984, 984–1,015, and 1,015–1,040 ft. Flowmeter testing of the test borehole open to the entire Floridan aquifer system indicated that the Upper Floridan aquifer contributed 92.4 percent of the total flow rate of 708 gallons per minute; the Lower Floridan confining unit contributed 3.0 percent; and the Lower Floridan aquifer contributed 4.6 percent. Horizontal hydraulic conductivity of the Lower Floridan confining unit derived from slug tests within three packer-isolated intervals ranged from 0.5 to 10 feet per day (ft/d). Aquifer-test analyses yielded values of transmissivity for the Upper Floridan aquifer, Lower Floridan confining unit, and the Lower Floridan aquifer of 46,000, 700, and 4,000 feet squared per day (ft2/d), respectively. Horizontal hydraulic conductivity of 4 ft/d for the Lower Floridan confining unit, derived from aquifer-test analyses, is near the midrange for values derived from packer-isolated slug tests. The transmissivity of the entire Floridan aquifer system derived from aquifer-test analyses totals about 51,000 ft2/d, similar to the value of 58,000 ft2/d derived from open slug tests on the entire Floridan aquifer system. Water-level data for each aquifer test were filtered for external influences such as barometric pressure, earth-tide effects, and long-term trends to enable detection of small (less than 1 foot) water-level responses to aquifer-test pumping. During the 72-hour aquifer test of pumping the Lower Floridan aquifer, a drawdown response of 51.7 ft was observed in the Lower Floridan pumped well and a drawdown response of 0.9 foot was observed in the Upper Floridan observation well located 85 ft from the pumped well.

Evaluation of borehole geophysical logging, aquifer-isolation tests, distribution of contaminants, and water-level measurements at the North Penn Area 5 Superfund Site, Bucks and Montgomery counties, Pennsylvania

USGS Publications Warehouse

Bird, Philip H.; Conger, Randall W.

2002-01-01

Borehole geophysical logging and aquifer-isolation (packer) tests were conducted at the North Penn Area 5 Superfund site in Bucks and Montgomery Counties, Pa. Caliper, naturalgamma, single-point-resistance, fluid-temperature, fluid-resistivity, heatpulse-flowmeter, and digital acoustic-televiewer logs and borehole television surveys were collected in 32 new and previously drilled wells that ranged in depth from 68 to 302 feet. Vertical borehole-fluid movement direction and rate were measured with a high-resolution heatpulse flowmeter under nonpumping conditions. The suite of logs was used to locate water-bearing fractures, determine zones of vertical borehole-fluid movement, select depths to set packers, and locate appropriate screen intervals for reconstructing new wells as monitoring wells. Aquifer-isolation tests were conducted in four wells to sample discrete intervals and to determine specific capacities of discrete water-bearing zones. Specific capacities of isolated zones during packer testing ranged from 0.12 to 15.30 gallons per minute per foot. Most fractures identified by borehole geophysical methods as water-producing or water-receiving zones produced water when isolated and pumped. The acoustic-televiewer logs define two basic fracture sets, bedding-plane partings with a mean strike of N. 62° E. and a mean dip of 27° NW., and high-angle fractures with a mean strike of N. 58° E. and a mean dip of 72° SE. Correlation of heatpulse-flowmeter data and acoustic-televiewer logs showed 83 percent of identified water-bearing fractures were high-angle fractures.

Geophysical and hydrologic analysis of an earthen dam site in southern Westchester County, New York

USGS Publications Warehouse

Chu, Anthony; Stumm, Frederick; Joesten, Peter K.; Noll, Michael L.

2013-01-01

Ninety percent of the drinking water for New York City passes through the Hillview Reservoir facility in the City of Yonkers, Westchester County, New York. In the past, several seeps located downslope from the reservoir have flowed out from the side of the steepest slope at the southern end of the earthen embankment. One seep that has been flowing continuously was discovered during an inspection of the embankment in 1999. Efforts were made in 2001 to locate the potential sources of the continuous flowing seep. In 2005, the U.S. Geological Survey, in cooperation with the New York City Department of Environmental Protection, began a cooperative study to investigate the relevant hydrogeologic framework to characterize the local groundwater-flow system and to determine possible sources of the seeps. The two agencies used hydrologic and surface geophysical techniques to assess the earthen embankment of the Hillview Reservoir. Between April 1, 2005 and March 1, 2008, water levels were measured manually each month at 46 wells surrounding the reservoir, and flow was measured monthly at three of the five seeps on the embankment. Water levels were measured hourly in the East Basin of the reservoir, at 24 of 46 wells, and discharge was measured hourly at two of the five seeps. Slug tests were performed at 16 wells to determine the hydraulic conductivity of the geologic material surrounding the screened zone. Estimated hydraulic conductivities for 25 wells on the southern embankment ranged from 0.0063 to 1.2 feet per day and averaged 0.17 foot per day. The two-dimensional resistivity surveys indicate a subsurface mound of electrically conductive material (low-resistivity zone) beneath the terrace area (top of dam) surrounding the reservoir with a distinct elevation increase closer to the crest. Two-dimensional shear wave velocity surveys indicate a similar structure of the high shear wave velocity materials (high-velocity zone), increasing in elevation toward the crest and decreasing toward the reservoir and toward the northern part of the study area. Water-quality samples collected from 12 wells, downtake chamber 1 of the reservoir, and two seeps detected the presence of arsenic, toluene, and two trihalomethanes. Water-quality samples collected at the two seeps detected fluoride, indicating a connection with reservoir water. Shallow wells on the southern embankment exhibited the largest seasonal water-level fluctuations ranging between 6 feet and 12 feet. The embankment is constructed from reworked low-permeability glacial deposits at the site. Water-level responses in observation wells within the embankment indicate that there is a shallow (approximately the upper 45 feet of the embankment) and a deep water-bearing unit within the embankment with a large downward vertical gradient between the shallow and deep water-bearing units. Precipitation strongly affected water levels in shallow wells, whereas the basin appears to be the main control on water levels in the deep wells. Seeps on the embankment slope appear to be caused by above-average precipitation that increases water levels in the shallow water-bearing unit, but does not easily recharge the deep water-bearing unit. Based on the data that have been analyzed, source water to the seeps appears to be primarily groundwater and, to a lesser extent, water from the East Basin of the reservoir.

The effect of fluorine on the stability of wadsleyite: Implications for the nature and depths of the transition zone in the Earth's mantle

NASA Astrophysics Data System (ADS)

Grützner, Tobias; Klemme, Stephan; Rohrbach, Arno; Gervasoni, Fernanda; Berndt, Jasper

2018-01-01

The Earth's mantle contains significant amounts of volatile elements, such as hydrogen (H), carbon (C) and the halogens fluorine (F), chlorine (Cl) and bromine (Br) and iodine (I). There is a wealth of knowledge about the global cycling of H and C, but there is only scant data on the concentrations of halogens in different Earth reservoirs and on the behavior of halogens during recycling in subduction zones. Here we focus on the storage potential of F in deeper parts of the Earth's mantle. The transition zone is a region in the Earth's mantle (410-660 km) known for its high water storage capacity, as the high pressure polymorphs of olivine, wadsleyite and ringwoodite are known to be able to incorporate several per-cent of water. In order to assess potential fractionation between water and F in the transition zone of the Earth's mantle, we set out to investigate the storage capacity of the halogen F in wadsleyite and olivine at transition zone conditions. Experiments were performed in a simplified mantle composition at temperatures from 1400 °C to 1900 °C and pressures from 17 up to 21 GPa in a multi anvil apparatus. The results show that F can shift the olivine-wadsleyite transition towards higher pressure. We find that F has an opposing effect to water, the latter of which extends the transition zone towards lower pressure. Moreover, the F storage capacity of wadsleyite is significantly lower than previously anticipated. F concentrations in wadsleyite range from 1470 ± 60 μg/g to 2110 ± 600 μg/g independent of temperature or pressure. The F storage capacity in wadsleyite is even lower than the F storage capacity of forsterite under transition zone conditions, and the latter can incorporate 3930 ± 140 μg/g F under these conditions. Based on our data we find that the transition zone cannot be a reservoir for F as it is assumed to be for water. Furthermore, we argue that during subduction of a volatile-bearing slab, fractionation of water from F will occur, where water enters preferentially the transition zone and F remains in the peridotite of the lowermost upper mantle.

Surficial deposits in the Bear Lake Basin

USGS Publications Warehouse

Reheis, Marith C.; Laabs, Benjamin J.C.; Forester, Richard M.; McGeehin, John P.; Kaufman, Darrell S.; Bright, Jordon

2005-01-01

Mapping and dating of surficial deposits in the Bear Lake drainage basin were undertaken to provide a geologic context for interpretation of cores taken from deposits beneath Bear Lake, which sometimes receives water and sediment from the glaciated Bear River and sometimes only from the small drainage basin of Bear Lake itself. Analyses of core sediments by others are directed at (1) constructing a high-resolution climate record for the Bear Lake area during the late Pleistocene and Holocene, and (2) investigating the sources and weathering history of sediments in the drainage basin. Surficial deposits in the upper Bear River and Bear Lake drainage basins are different in their overall compositions, although they do overlap. In the upper Bear River drainage, Quaternary deposits derived from glaciation of the Uinta Range contain abundant detritus weathered from Precambrian quartzite, whereas unglaciated tributaries downstream mainly contribute finer sediment weathered from much younger, more friable sedimentary rocks. In contrast, carbonate rocks capped by a carapace of Tertiary sediments dominate the Bear Lake drainage basin.

The Gas Hills uranium district and some probable controls for ore deposition

USGS Publications Warehouse

Zeller, Howard Davis

1957-01-01

Uranium deposits occur in the upper coarse-grained facies of the Wind River formation of Eocene age in the Gas Hills district of the southern part of the Wind River Basin. Some of the principal deposits lie below the water table in the unoxidized zone and consist of uraninite and coffinite occurring as interstitial fillings in irregular blanket-like bodies. In the near-surface deposits that lie above the water table, the common yellow uranium minerals consist of uranium phosphates, silicates, and hydrous oxides. The black unoxidized uraninite -coffinite ores show enrichment of molybdenum, arsenic, and selenium when compared to the barren sandstone. Probable geologic controls for ore deposits include: 1) permeable sediments that allowed passage of ore-bearing solutions; 2) numerous faults that acted as impermeable barriers impounding the ore -bearing solutions; 3) locally abundant pyrite, carbonaceous material, and natuial gas containing hydrogen sulfide that might provide a favorable environment for precipitation of uranium. Field and laboratory evidence indicate that the uranium deposits in the Gas Hills district are very young and related to the post-Miocene to Pleistocene regional tilting to the south associated with the collapse of the Granite Mountains fault block. This may have stopped or reversed ground water movement from a northward (basinward) direction and alkaline ground water rich in carbonate could have carried the uranium into the favorable environment that induced precipitation.

Application of flowmeter and depth-dependent water quality data for improved production well construction.

PubMed

Gossell, M A; Nishikawa, T; Hanson, R T; Izbicki, J A; Tabidian, M A; Bertine, K

1999-01-01

Ground water production wells commonly are designed to maximize well yield and, therefore, may be screened over several water-bearing zones. These water-bearing zones usually are identified, and their hydrogeologic characteristics and water quality are inferred, on the basis of indirect data such as geologic and geophysical logs. Production well designs based on these data may result in wells that are drilled deeper than necessary and are screened through zones having low permeability or poor-quality ground water. In this study, we examined the application of flowmeter logging and depth-dependent water quality samples for the improved design of production wells in a complex hydrogeologic setting. As a demonstration of these techniques, a flowmeter log and depth-dependent water quality data were collected from a long-screened production well within a multilayered coastal aquifer system in the Santa Clara-Calleguas Basin, Ventura County, California. Results showed that the well yields most of its water from four zones that constitute 58% of the screened interval. The importance of these zones to well yield was not readily discernible from indirect geologic or geophysical data. The flowmeter logs and downhole water quality data also show that small quantities of poor-quality water could degrade the overall quality of water from the well. The data obtained from one well can be applied to other proposed wells in the same hydrologic basin. The application of flowmeter and depth-dependent water quality data to well design can reduce installation costs and improve the quantity and quality of water produced from wells in complex multiple-aquifer systems.

Application of flowmeter and depth-dependent water quality data for improved production well construction

USGS Publications Warehouse

Gossell, M.A.; Nishikawa, Tracy; Hanson, Randall T.; Izbicki, John A.; Tabidian, M.A.; Bertine, K.

1999-01-01

Ground water production wells commonly are designed to maximize well yield and, therefore, may be screened over several water-bearing zones. These water-bearing zones usually are identified, and their hydrogeologic characteristics and water quality are inferred, on the basis of indirect data such as geologic and geophysical logs. Production well designs based on these data may result in wells that are drilled deeper than necessary and are screened through zones having low permeability or poor-quality ground water. In this study, we examined the application of flowmeter logging and depth-dependent water quality samples for the improved design of production wells in a complex hydrogeologic setting. As a demonstration of these techniques, a flowmeter log and depth-dependent water quality data were collected from a long-screened production well within a multilayered coastal aquifer system in the Santa Clara-Calleguas Basin, Ventura County, California. Results showed that the well yields most of its water from four zones that constitute 58% of the screened interval. The importance of these zones to well yield was not readily discernible from indirect geologic or geophysical data. The flowmeter logs and downhole water quality data also show that small quantities of poor-quality water could degrade the overall quality of water from the well. The data obtained from one well can be applied to other proposed wells in the same hydrologic basin. The application of flowmeter and depth-dependent water quality data to well design can reduce installation costs and improve the quantity and quality of water produced from wells in complex multiple-aquifer systems.

Evaluation of geophysical logs and aquifer-isolation tests, Phase III, August 2002 to March 2004, Crossley Farm superfund site, Hereford township, Berks County, Pennsylvania

USGS Publications Warehouse

Conger, Randall W.; Low, Dennis J.

2006-01-01

Between August 2002 and March 2004, geophysical logging was conducted in 23 boreholes at the Crossley Farm Superfund Site, Hereford Township, Berks County, Pa., to determine the water-producing zones, water-receiving zones, zones of vertical-borehole flow, and fracture orientation where applicable. The boreholes ranged in depth from 71 to 503 ft (feet) below land surface. The geophysical logging determined the placement of well screens and packers, which allow monitoring and sampling of water-bearing zones in the fractured bedrock so the horizontal and vertical distribution of contaminated ground water migrating from known sources could be determined. Geophysical logging included collection of caliper (22 boreholes), fluid-temperature (17 boreholes), single-pointresistance (17 boreholes), natural-gamma (17 boreholes), fluidflow (18 boreholes), and acoustic-televiewer (13 boreholes) logs. Caliper and acoustic-televiewer logs were used to locate fractures, joints, and weathered zones. Inflections on fluid-temperature and single-point-resistance logs indicated possible water-bearing zones, and flowmeter measurements verified these locations. Single-point-resistance, natural-gamma, and geologist logs provided information on stratigraphy; the geologist log also provided information on the location of possible water-producing zones.Borehole geophysical logging and heatpulse flowmetering indicated active flow in 10 boreholes. Seven of the boreholes are in ground-water discharge areas and three boreholes are in ground-water recharge areas. Heatpulse flowmetering, in conjunction with the geologist logs, indicates lithologic contacts (changes in lithology from a gneiss dominated by quartz-plagioclase-feldspar mineralogy to a gneiss dominated by hornblende mineralogy) are typically fractured, permeable, and effective transmitters of water. Single-well, aquifer-isolation (packer) tests were performed on two boreholes. Packers were set at depths ranging from 210 to 465 ft below land surface to isolate water-bearing zones at discrete intervals. Placement and inflation of the packers provided information on hydraulic heads, specific capacities, the hydraulic connection between intervals, and depth-specific water-quality samples. Upon completion of borehole geophysical logging and interpretation of geophysical logs, geologist logs, drillers notes, and packer work, 13 boreholes were reconstructed such that water levels could be monitored and water samples could be collected from discrete shallow, intermediate, and deep waterbearing fractures in each borehole. Boreholes BE-1672, BE-1674, BE-1676, and BE-1677 remained open-hole for sampling purposes. Boreholes RI-2, RI-3, and RI-4 remained openhole for injection purposes. Boreholes P-1, P-2, and P-3 remained open and were converted to pumping wells.

Seismic evidence for water transport out of the mantle transition zone beneath the European Alps

NASA Astrophysics Data System (ADS)

Liu, Zhen; Park, Jeffrey; Karato, Shun-ichiro

2018-01-01

The mantle transition zone has been considered a major water reservoir in the deep Earth. Mass transfer across the transition-zone boundaries may transport water-rich minerals from the transition zone into the water-poor upper or lower mantle. Water release in the mantle surrounding the transition zone could cause dehydration melting and produce seismic low-velocity anomalies if some conditions are met. Therefore, seismic observations of low-velocity layers surrounding the transition zone could provide clues of water circulation at mid-mantle depths. Below the Alpine orogen, a depressed 660-km discontinuity has been imaged clearly using seismic tomography and receiver functions, suggesting downwellings of materials from the transition zone. Multitaper-correlation receiver functions show prominent ∼0.5-1.5% velocity reductions at ∼750-800-km depths, possibly caused by partial melting in the upper part of lower mantle. The gap between the depressed 660-km discontinuity and the low-velocity layers is consistent with metallic iron as a minor phase in the topmost lower mantle reported by laboratory studies. Velocity drops atop the 410-km discontinuity are observed surrounding the Alpine orogeny, suggesting upwelling of water-rich rock from the transition zone in response to the downwelled materials below the orogeny. Our results provide evidence that convective penetration of the mantle transition zone pushes hydrated minerals both upward and downward to add hydrogen to the surrounding mantle.

Reaction between hydrous wadsleyite and iron: Implication for water distribution in Earth's transition zone

NASA Astrophysics Data System (ADS)

Zhu, F.; Li, J.; Liu, J.; Dong, J.

2017-12-01

The mantle transition zone (TZ) is considered as a potential water reservoir due to large capacities of wadsleyite and ringwoodite to store water in the structures. Whether it is a hydrous layer or an empty reservoir, however, is still under debate. Because the TZ may contain metallic iron1, 2 and water is an oxidizing agent at > 5 GPa, the stability of coexisting iron and TZ hydrous phases needs to be examined. In this study, we conducted multi-anvil experiments on iron with synthetic hydrous wadsleyite or forsterite and water under TZ pressure-temperature conditions. Similar rapid reactions were observed for both types of starting materials, producing ferropericlase, iron-bearing wadsleyite or ringwoodite, and iron hydride. The results imply that a hydrous TZ is incompatible with a reduced state, and that water distribution of TZ is confined to subducting slabs and slab-mantle boundaries, where water or hydrous phases in slab must oxidize the adjacent mantle before they can hydrate the silicates. In contrast, the bulk transition zone may be mostly dry. The iron hydride produced from this slab-mantle interaction may sink to greater depths due to their low melting temperature3, thus providing a pathway for hydrogen to enter the lower mantle and core. References 1. O'Neill HSC, McCammon C, Canil D, Rubie D, Ross C, Seifert F. Mossbauer spectroscopy of mantle transition zone phases and determination of minimum Fe3+ content. American Mineralogist 1993, 78(3-4): 456-460. 2. Rohrbach A, Ballhaus C, Golla-Schindler U, Ulmer P, Kamenetsky VS, Kuzmin DV. Metal saturation in the upper mantle. Nature 2007, 449(7161): 456-458. 3. Sakamaki K, Takahashi E, Nakajima Y, Nishihara Y, Funakoshi K, Suzuki T, et al. Melting phase relation of FeH x up to 20GPa: Implication for the temperature of the Earth's core. Physics of the Earth and Planetary Interiors 2009, 174(1): 192-201.

Placing an upper limit on cryptic marine sulphur cycling.

PubMed

Johnston, D T; Gill, B C; Masterson, A; Beirne, E; Casciotti, K L; Knapp, A N; Berelson, W

2014-09-25

A quantitative understanding of sources and sinks of fixed nitrogen in low-oxygen waters is required to explain the role of oxygen-minimum zones (OMZs) in controlling the fixed nitrogen inventory of the global ocean. Apparent imbalances in geochemical nitrogen budgets have spurred numerous studies to measure the contributions of heterotrophic and autotrophic N2-producing metabolisms (denitrification and anaerobic ammonia oxidation, respectively). Recently, 'cryptic' sulphur cycling was proposed as a partial solution to the fundamental biogeochemical problem of closing marine fixed-nitrogen budgets in intensely oxygen-deficient regions. The degree to which the cryptic sulphur cycle can fuel a loss of fixed nitrogen in the modern ocean requires the quantification of sulphur recycling in OMZ settings. Here we provide a new constraint for OMZ sulphate reduction based on isotopic profiles of oxygen ((18)O/(16)O) and sulphur ((33)S/(32)S, (34)S/(32)S) in seawater sulphate through oxygenated open-ocean and OMZ-bearing water columns. When coupled with observations and models of sulphate isotope dynamics and data-constrained model estimates of OMZ water-mass residence time, we find that previous estimates for sulphur-driven remineralization and loss of fixed nitrogen from the oceans are near the upper limit for what is possible given in situ sulphate isotope data.

Preliminary appraisal of the geohydrologic aspects of drainage wells, Orlando area, central Florida

USGS Publications Warehouse

Kimrey, Joel O.

1978-01-01

The Floridan aquifer contains two highly transmissive cavernous zones in the Orlando area: an upper producing zone about 150-600 feet below land surface; and a lower producing zone about 1,100-1,500 feet below land surface. Natural head differences are downward and there is hydraulic connection between the two producing zones. Drainage wells are finished open-end into the upper producing zone and emplace surface waters directly into that zone by gravity. Quantitatively, their use constitutes an effective method of artificial recharge. Their negative aspects relate to the probably poor, but unknown, quality of the recharge water. Caution is suggested in drawing definite and final conclusions on the overall geohydrologic and environmental effects of drainage wells prior to the collection and interpretation of a considerable quantity of new data. Though few ground-water pollution problems have been documented to date, the potential for such pollution should be seriously considered in light of the prob-able continuing need to use drainage wells; the probable volumes and quality of water involved; and the hydraulic relations between the two producing zones.

Geohydrology and potential for upward movement of saline water in the Cocoa well field, East Orange County, Florida

USGS Publications Warehouse

Phelps, G.G.; Schiffer, D.M.

1996-01-01

The Floridan aquifer system, an approximately 2,000-foot thick sequence of Eocene-age limestone and dolomite, is the main source of water supply in central Florida. Hydraulic conductivity is different in strata of different lithology and is the basis for separating the aquifer system into the Upper Floridan aquifer, a middle semi- confining unit, and the Lower Floridan aquifer. The coastal city of Cocoa withdraws about 26 million gallons of water per day from the Upper Floridan aquifer from a well field in east Orange County, about 25 miles inland. About 60 million gallons per day are withdrawn from the Upper Floridan aquifer and 56 million gallons per day from the Lower Floridan aquifer in the Orlando area, about 15 miles west of the Cocoa well field. Wells drilled in the Cocoa well field from 1955-61 yielded water with chloride concentrations ranging from 25-55 milligrams per liter. Soon after the wells were put in service, chloride concentrations increased; therefore, new wells were drilled further inland. Chloride concen- trations in water from many of the new wells also have increased. Possible sources of saline water are lateral movement of relict seawater in the Upper Floridan aquifer from the east, regional upconing of saline water from the Lower Floridan aquifer or underlying older rocks, or localized upward movement of saline water through fractures. Several test wells were drilled to provide information about chloride concentration changes with depth and to monitor changes with time, including a multi-zone well drilled in 1965 (well C) and two wells drilled in the 1990's (wells R and S). Chloride concentrations have increased in the zone pumped by the supply wells (the upper 500 feet of the aquifer) and in the 1,351-1,357-foot deep zone of well C, but not in the two intervening zones. This indicates that the source of saline water is located laterally, rather than vertically, from the pumped zone in the area of well C. The potential for upward movement of saline water depends on the direction of the vertical hydraulic gradient and on the vertical hydraulic conductivity of the aquifer. A series of aquifer tests was run in 1993-94 and existing water-level and water-quality data were analyzed to evaluate the potential for upward movement of saline water in the well field. The transmissivity of the upper 500 feet of the aquifer is about 100,000 feet squared per day (the horizontal hydraulic conductivity is about 200 feet per day) and the storage coefficient is about 2x10 -4. Horizontal hydraulic conductivities determined from slug tests of the three deepest zones of well C ranged from 20-50 feet per day. Vertical hydraulic conductivities probably do not exceed 0.05 feet per day. The vertical hydraulic gradient is determined by comparing water levels in the various zones, but because of density differences, unadjusted water levels in the deepest zone investigated cannot be directly compared to water levels in the overlying freshwater zones. The difference between environmental-water heads (adjusted for density differences) in the saline-water zone of well C and the overlying freshwater zone were calculated from measured water levels for the period 1966 to 1994. During most of this time period, the gradient was downward, indicating that saline water did not move upward. Upconing of saline water probably is not taking place in the center and western part of the well field, based on the low vertical hydraulic conductivity values estimated for the middle semi-confining unit, the generally downward vertical hydraulic gradient, and the constant chloride concentrations in the intermediate zones of well C. However, there is no information about the extent of the zone of low vertical hydraulic conductivity gradient in the eastern part of the well field. Thus, increased chloride concentrations in supply wells in the eastern part of the well field could be caused either by lateral movement of saline water from the east, or by upwar

Hydrogeology, water quality, and simulated effects of ground-water withdrawals from the Floridan aquifer system, Seminole County and vicinity, Florida

USGS Publications Warehouse

Spechler, Rick M.; Halford, Keith J.

2001-01-01

The hydrogeology and ground-water quality of Seminole County in east-central Florida was evaluated. A ground-water flow model was developed to simulate the effects of both present day (September 1996 through August 1997) and projected 2020 ground-water withdrawals on the water levels in the surficial aquifer system and the potentiometric surface of the Upper and Lower Floridan aquifers in Seminole County and vicinity. The Floridan aquifer system is the major source of ground water in the study area. In 1965, ground-water withdrawals from the Floridan aquifer system in Seminole County were about 11 million gallons per day. In 1995, withdrawals totaled about 69 million gallons per day. Of the total ground water used in 1995, 74 percent was for public supply, 12 percent for domestic self-supplied, 10 percent for agriculture self-supplied, and 4 percent for recreational irrigation. The principal water-bearing units in Seminole County are the surficial aquifer system and the Floridan aquifer system. The two aquifer systems are separated by the intermediate confining unit, which contains beds of lower permeability sediments that confine the water in the Floridan aquifer system. The Floridan aquifer system has two major water-bearing zones (the Upper Floridan aquifer and the Lower Floridan aquifer), which are separated by a less-permeable semiconfining unit. Upper Floridan aquifer water levels and spring flows have been affected by ground-water development. Long-term hydrographs of four wells tapping the Upper Floridan aquifer show a general downward trend from the early 1950's until 1990. The declines in water levels are caused predominantly by increased pumpage and below average annual rainfall. From 1991 to 1998, water levels rose slightly, a trend that can be explained by an increase in average annual rainfall. Long-term declines in the potentiometric surface varied throughout the area, ranging from about 3 to 12 feet. Decreases in spring discharge also have been observed in a few springs with long-term record. Chloride concentrations in water from the Upper Floridan aquifer in Seminole County range areally from 6.2 to 5,300 milligrams per liter. Chloride concentrations are lowest in the recharge areas of the Floridan aquifer system in the western part of Seminole County and near Geneva. The most highly mineralized water occurs adjacent to the Wekiva River in northwestern Seminole County, around the eastern part of Lake Jesup, and along the St. Johns River in eastern Seminole County. Analysis of limited long-term water-quality data indicates that the chloride concentrations in water for most wells in the Floridan aquifer system in Seminole County have not changed significantly in the 20-year period from 1976 to 1996, and probably not since the mid 1950's. Analysis of water samples collected from some Upper Floridan aquifer springs, however, indicates that the water has become more mineralized during recent years. Increases in specific conductance and concentrations of major cations and anions were observed at several of the springs within the study area where long-term water-quality data were available. Associated with these increases in the mineralization of spring water has been an increase in total nitrate-plus- nitrite as nitrogen concentration. A three-dimensional model was developed to simulate ground-water flow in the surficial and Floridan aquifer systems. The steady-state ground-water flow model was calibrated to water-level data that was averaged over a 1-year period from September 1996 through August 1997. The calibrated flow model generally produced simulated water levels in reasonably close agreement with measured water levels. As a result, the calibrated model was used to simulate the effects of expected increases in ground-water withdrawals on the water levels in the surficial aquifer system and on the potentiometric surface of the Upper and Lower Floridan aquifers in Seminole County. The ca

Hydrogeologic framework and simulation of shallow ground-water flow in the vicinity of a hazardous-waste landfill near Pinewood, South Carolina

USGS Publications Warehouse

Vroblesky, D.A.

1994-01-01

The geologic units in the vicinity of a hazardous- waste landfill near Pinewood, S.C., were divided into hydrogeologic units on the basis of lithologic and hydrologic characteristics. A quasi-3- dimensional finite-difference ground-water-flow model was constructed to represent the hydrogeologic flamework. The simulation results indicate that if non-reactive constituents were released to the Lang Syne water-bearing zone underlying the central and western pans of the disposal area, the constituents would move in a southwesterly direction at a rate of about one-half to 7 feet per year. Contaminants could move from the Lang Syne water-bearing zone upward to the surficial aquifer, to streams, or to Lake Marion. Although these flow rates indicate that it would require at least 50 years for contaminants to travel between the disposal area and a nearby (400 ft) potential discharge area, the heterogeneity of the site hydrogeology imparts an uncertainty to the conclusion. Faster travel times cannot be ruled out if contamination enters an area having a higher hydraulic conductivity than those determined in this investigation. Faster arrival times at Lake Marion also could result if there are pathways shorter than about 400 feet between contaminated water and an area where it can discharge to the surficial aquifer or to streams. If contaminant releases were to occur on the eastern side of the ground-water mounds, near landfill section II and the southeastern part of land fill section I, initial flow directions would be toward the water-level depression in the eastern part of the facility. Ground water within water- level depression would flow downward, probably to the underlying lower Sawdust Landing water-beating zone. Movement of non-reactive constituents in the tower Sawdust Landing water-bearing zone would be southwestward toward Lake Marion at a rate of about 8 to 20 feet per year. Transport to the lake by this route could require more than 200 years.

Uranium Bio-accumulation and Cycling as revealed by Uranium Isotopes in Naturally Reduced Sediments from the Upper Colorado River Basin

NASA Astrophysics Data System (ADS)

Lefebvre, Pierre; Noël, Vincent; Jemison, Noah; Weaver, Karrie; Bargar, John; Maher, Kate

2016-04-01

Uranium (U) groundwater contamination following oxidized U(VI) releases from weathering of mine tailings is a major concern at numerous sites across the Upper Colorado River Basin (CRB), USA. Uranium(IV)-bearing solids accumulated within naturally reduced zones (NRZs) characterized by elevated organic carbon and iron sulfide compounds. Subsequent re-oxidation of U(IV)solid to U(VI)aqueous then controls the release to groundwater and surface water, resulting in plume persistence and raising public health concerns. Thus, understanding the extent of uranium oxidation and reduction within NRZs is critical for assessing the persistence of the groundwater contamination. In this study, we measured solid-phase uranium isotope fractionation (δ238/235U) of sedimentary core samples from four study sites (Shiprock, NM, Grand Junction, Rifle and Naturita, CO) using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). We observe a strong correlation between U accumulation and the extent of isotopic fractionation, with Δ238U up to +1.8 ‰ between uranium-enriched and low concentration zones. The enrichment in the heavy isotopes within the NRZs appears to be especially important in the vadose zone, which is subject to variations in water table depth. According to previous studies, this isotopic signature is consistent with biotic reduction processes associated with metal-reducing bacteria. Positive correlations between the amount of iron sulfides and the accumulation of reduced uranium underline the importance of sulfate-reducing conditions for U(IV) retention. Furthermore, the positive fractionation associated with U reduction observed across all sites despite some variations in magnitude due to site characteristics, shows a regional trend across the Colorado River Basin. The maximum extent of 238U enrichment observed in the NRZ proximal to the water table further suggests that the redox cycling of uranium, with net release of U(VI) to the groundwater by non-fractionating oxidation, is occurring within this zone. Thus, release of uranium from the NRZs may play a critical role in the persistence of groundwater contamination at these sites.

CORE-BASED INTEGRATED SEDIMENTOLOGIC, STRATIGRAPHIC, AND GEOCHEMICAL ANALYSIS OF THE OIL SHALE BEARING GREEN RIVER FORMATION, UINTA BASIN, UTAH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lauren P. Birgenheier; Michael D. Vanden Berg,

An integrated detailed sedimentologic, stratigraphic, and geochemical study of Utah's Green River Formation has found that Lake Uinta evolved in three phases (1) a freshwater rising lake phase below the Mahogany zone, (2) an anoxic deep lake phase above the base of the Mahogany zone and (3) a hypersaline lake phase within the middle and upper R-8. This long term lake evolution was driven by tectonic basin development and the balance of sediment and water fill with the neighboring basins, as postulated by models developed from the Greater Green River Basin by Carroll and Bohacs (1999). Early Eocene abrupt global-warmingmore » events may have had significant control on deposition through the amount of sediment production and deposition rates, such that lean zones below the Mahogany zone record hyperthermal events and rich zones record periods between hyperthermals. This type of climatic control on short-term and long-term lake evolution and deposition has been previously overlooked. This geologic history contains key points relevant to oil shale development and engineering design including: (1) Stratigraphic changes in oil shale quality and composition are systematic and can be related to spatial and temporal changes in the depositional environment and basin dynamics. (2) The inorganic mineral matrix of oil shale units changes significantly from clay mineral/dolomite dominated to calcite above the base of the Mahogany zone. This variation may result in significant differences in pyrolysis products and geomechanical properties relevant to development and should be incorporated into engineering experiments. (3) This study includes a region in the Uinta Basin that would be highly prospective for application of in-situ production techniques. Stratigraphic targets for in-situ recovery techniques should extend above and below the Mahogany zone and include the upper R-6 and lower R-8.« less

What electrical measurements can say about changes in fault systems.

PubMed Central

Madden, T R; Mackie, R L

1996-01-01

Earthquake zones in the upper crust are usually more conductive than the surrounding rocks, and electrical geophysical measurements can be used to map these zones. Magnetotelluric (MT) measurements across fault zones that are parallel to the coast and not too far away can also give some important information about the lower crustal zone. This is because the long-period electric currents coming from the ocean gradually leak into the mantle, but the lower crust is usually very resistive and very little leakage takes place. If a lower crustal zone is less resistive it will be a leakage zone, and this can be seen because the MT phase will change as the ocean currents leave the upper crust. The San Andreas Fault is parallel to the ocean boundary and close enough to have a lot of extra ocean currents crossing the zone. The Loma Prieta zone, after the earthquake, showed a lot of ocean electric current leakage, suggesting that the lower crust under the fault zone was much more conductive than normal. It is hard to believe that water, which is responsible for the conductivity, had time to get into the lower crustal zone, so it was probably always there, but not well connected. If this is true, then the poorly connected water would be at a pressure close to the rock pressure, and it may play a role in modifying the fluid pressure in the upper crust fault zone. We also have telluric measurements across the San Andreas Fault near Palmdale from 1979 to 1990, and beginning in 1985 we saw changes in the telluric signals on the fault zone and east of the fault zone compared with the signals west of the fault zone. These measurements were probably seeing a better connection of the lower crust fluids taking place, and this may result in a fluid flow from the lower crust to the upper crust. This could be a factor in changing the strength of the upper crust fault zone. PMID:11607664

Draft Title 40 CFR 191 compliance certification application for the Waste Isolation Pilot Plant. Volume 8: Appendices HYDRO, IRD, LTM, NUTS, PAR, PMR, QAPD, RBP

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

Geohydrologic data have been collected in the Los Medanos area at the US Department of Energy`s proposed Waste Isolation Pilot Plant (WIPP) site in southeastern New Mexico since 1975 as part of a study evaluating the feasibility of storing defense-associated nuclear wastes within the bedded salt of the Salado Formation of Permian age. Drilling and hydrologic testing have identified three principal water-bearing zones above the Salado Formation and one below that could potentially transport wastes to the biosphere if the proposed facility were breached. The zones above the Salado are the contact between the Rustler and Salado Formations and themore » Culebra and Magenta Dolomite Members of the Rustler Formation of Permian age. The zone below the Salado Formation consists of channel sandstones in the Bell Canyon Formation of the Permian Delaware Mountain Group. Determinations of hydraulic gradients, directions of flow, and hydraulic properties were hindered because of the negligible permeability of the water-bearing zones. Special techniques in drilling, well completion, and hydraulic testing have been developed to determine the hydrologic characteristics of these water-producing zones.« less

Physiological asymmetry in etiolated pea epicotyls: relation to patterns of auxin distribution and phototropic behavior

NASA Technical Reports Server (NTRS)

Kuhn, H.; Galston, A. W.

1992-01-01

Etiolated pea seedlings require transformation of Pr phytochrome to Pfr before they display optimal phototropic response to unilateral blue light. This study investigates the possible role of auxin transport in explaining these phenomena. Labeled [2-14C]IAA applied to the intact terminal buds of dark-grown and red light-treated pea seedlings was measured 210 min later on the shaded and illuminated sides of the epicotyl as a function of direction and duration of irradiation with blue light. Totally darkened epicotyls show an asymmetry in distribution of radioactivity in the upper growth zone of the epicotyl, in favor of the side under the concave part of the apical hook. Red light, which greatly potentiates curvature toward subsequent unilateral blue light, lowers this asymmetry. Blue light directed to the epicotyl of red-pretreated plants in a plane parallel to the hook and from the side bearing the convex portion of the hook induces positive phototropic curvature as well as a surplus of radioactivity on the illuminated side of the upper epicotyl and on the shaded side of the lower growth zone of the epicotyl. Light directed to the side bearing the concave part of the hook also causes an accumulation of counts in the upper part of the lighted side but produces neither curvature of the epicotyl nor accumulation of counts in the lower shaded side. Because of this built-in physiological asymmetry in the growth zone just below the apical hook, it is difficult to explain the effects of red and blue light on curvature in terms of patterns of auxin distribution alone.

Physiological asymmetry in etiolated pea epicotyls: relation to patterns of auxin distribution and phototropic behavior.

PubMed

Kuhn, H; Galston, A W

1992-01-01

Etiolated pea seedlings require transformation of Pr phytochrome to Pfr before they display optimal phototropic response to unilateral blue light. This study investigates the possible role of auxin transport in explaining these phenomena. Labeled [2-14C]IAA applied to the intact terminal buds of dark-grown and red light-treated pea seedlings was measured 210 min later on the shaded and illuminated sides of the epicotyl as a function of direction and duration of irradiation with blue light. Totally darkened epicotyls show an asymmetry in distribution of radioactivity in the upper growth zone of the epicotyl, in favor of the side under the concave part of the apical hook. Red light, which greatly potentiates curvature toward subsequent unilateral blue light, lowers this asymmetry. Blue light directed to the epicotyl of red-pretreated plants in a plane parallel to the hook and from the side bearing the convex portion of the hook induces positive phototropic curvature as well as a surplus of radioactivity on the illuminated side of the upper epicotyl and on the shaded side of the lower growth zone of the epicotyl. Light directed to the side bearing the concave part of the hook also causes an accumulation of counts in the upper part of the lighted side but produces neither curvature of the epicotyl nor accumulation of counts in the lower shaded side. Because of this built-in physiological asymmetry in the growth zone just below the apical hook, it is difficult to explain the effects of red and blue light on curvature in terms of patterns of auxin distribution alone.

76 FR 33639 - Safety Zone; New York Water Taxi 10th Anniversary Fireworks

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-09

...-AA00 Safety Zone; New York Water Taxi 10th Anniversary Fireworks, Upper New York Bay, Red Hook, NY... New York Water Taxi. The fireworks will commence at 9 p.m. on June 21, 2011 and will last... CFR Part 165 Harbors, Marine safety, Navigation (water), Reporting and recordkeeping requirements...

Evaluation of geophysical logs, phase I, for Crossley Farms Superfund Site, Berks County, Pennsylvania

USGS Publications Warehouse

Conger, Randall W.

1998-01-01

Twenty-one wells were drilled at Crossley Farms Superfund Site between December 15, 1987, and May 1, 1988, to define and monitor the horizontal and vertical distribution of ground-water contamination emanating from a suspected contaminant source area (Blackhead Hill). Eight well clusters were drilled on or near the Crossley Site and three well clusters were drilled at locations hydrologically down gradient from the site. Depths of wells range from 21 to 299 feet below land surface. These wells were installed in saprolite in shallow, intermediate, and deep water-producing zones of the fractured bedrock aquifer. Borehole-geophysical and video logging were conducted between April 24, 1997, and May 8, 1997, to determine the water-producing zones, water-receiving zones, zones of vertical flow, borehole depth, and casing integrity in each well. This data and interpretation will be used to determine the location of the well intake for the existing open-hole wells, which will be retrofitted to isolate and monitor water-producing zones and prevent further cross-contamination within each open borehole, and identify wells that may need rehabilitation or replacement. Caliper and video logs were used to locate fractures, inflections on fluid-temperature and fluidresistivity logs indicated possible fluid-bearing fractures, and flowmeter measurements verified these locations. Single-point-resistance and natural-gamma logs provided information on stratigraphy. After interpretation of geophysical logs, video logs, and driller?s notes, all wells will be constructed so that water-level fluctuations can be monitored and discrete water samples collected from shallow, intermediate, and deep water-bearing zones in each well. Geophysical logs were run on seven bedrock and two deep bedrock wells. Gamma logs were run on 10 bedrock wells. Twenty-two wells were inspected visually with the borehole video camera for casing integrity.

How the 410-km Discontinuity Reflects Mantle Water Content: Constraints from High-Pressure Experiments on Wadsleyite Single-Crystal Elasticity

NASA Astrophysics Data System (ADS)

Buchen, J.; Marquardt, H.; Boffa Ballaran, T.; Kawazoe, T.; Speziale, S.; Kurnosov, A.

2017-12-01

The olivine-wadsleyite phase transition gives rise to a seismic discontinuity at 410 km depth. By incorporating hydroxyl groups in its crystal structure, wadsleyite can store large amounts of water in the shallow transition zone. The velocity contrast across the 410-km seismic discontinuity has been widely used to deduce mantle mineralogy including estimates of the water content at depth. To interpret seismic observations in terms of mantle mineralogy and deep water cycling, the elastic properties of wadsleyite need to be determined at relevant pressures and temperatures. We performed simultaneous sound wave velocity and density measurements on iron-bearing wadsleyite single crystals at high pressures and first experiments at combined high pressures and high temperatures. When compared with previous work on hydrous iron-bearing wadsleyite with identical Fe/(Mg+Fe) ratio of 0.11, our results show that hydration of iron-bearing wadsleyite reduces the sound wave velocities at low pressures. At high pressures, in contrast, P-wave and S-wave velocities of hydrous and anhydrous iron-bearing wadsleyite cross over and become seismically indistinguishable at conditions of the transition zone. As a consequence, hydrated regions in the shallow transition zone cannot be detected by seismic tomography. Motivated by our experimental results, we modeled velocity, density, and acoustic impedance contrasts across the 410-km seismic discontinuity and found velocity contrasts to vary only slightly with hydration. Instead, we show that the impedance contrast caused by the olivine-wadsleyite phase transition and hence the reflectivity of the 410-km seismic discontinuity are more sensitive to hydration. Our findings give important constraints on the interpretation of seismic observations aiming to trace Earth's deep water cycle.

15 CFR Appendix B to Subpart M of... - Zones Within the Sanctuary Where Overflights Below 1000 Feet Are Prohibited

Code of Federal Regulations, 2014 CFR

2014-01-01

... high water to 3 nautical miles (nmi) offshore between a line extending from Point Santa Cruz on a southwesterly bearing of 220° true and a line extending from 2.0 nmi north of Pescadero Point on a southwesterly bearing of 240° true; (2) From mean high water to 3 nmi offshore between a line extending from the Carmel...

15 CFR Appendix B to Subpart M of... - Zones Within the Sanctuary Where Overflights Below 1000 Feet Are Prohibited

Code of Federal Regulations, 2013 CFR

2013-01-01

... high water to 3 nautical miles (nmi) offshore between a line extending from Point Santa Cruz on a southwesterly bearing of 220° true and a line extending from 2.0 nmi north of Pescadero Point on a southwesterly bearing of 240° true; (2) From mean high water to 3 nmi offshore between a line extending from the Carmel...

15 CFR Appendix B to Subpart M of... - Zones Within the Sanctuary Where Overflights Below 1000 Feet Are Prohibited

Code of Federal Regulations, 2012 CFR

2012-01-01

... high water to 3 nautical miles (nmi) offshore between a line extending from Point Santa Cruz on a southwesterly bearing of 220° true and a line extending from 2.0 nmi north of Pescadero Point on a southwesterly bearing of 240° true; (2) From mean high water to 3 nmi offshore between a line extending from the Carmel...

How many upper Eocene microspherule layers: More than we thought

NASA Technical Reports Server (NTRS)

Hazel, Joseph E.

1988-01-01

The scientific controversy over the origin of upper Eocene tektites, microtektites and other microspherules cannot be logically resolved until it is determined just how many events are involved. The microspherule-bearing beds in marine sediments have been dated using standard biozonal techniques. Although a powerful stratigraphic tool, zonal biostratigraph has its limitations. One is that if an event, such as a microspherule occurrence, is observed to occur in a zone at one locality and then a similar event observed in the same zone at another locality, it still may be unwarranted to conclude that these events exactly correlate. To be in a zone a sample only need be between the fossil events that define the zone boundaries. It is often very difficult to accurately determine where within a zone one might be. Further, the zone defining events do not everywhere occur at the same points in time. That is, the ranges of the defining taxa are not always filled. Thus, the length of time represented by a zone (but not, of course, its chronozone) can vary from place to place. These problems can be offset by use of chronostratigraphic modelling techniques such as Graphic Correlation. This technique was used to build a Cretaceous and Cenozoic model containing fossil, magnetopolarity, and other events. The scale of the model can be demonstrated to be linear with time. This model was used to determine the chronostratigraphic position of upper Eocene microspherule layers.

Meteoric calcite cementation: diagenetic response to relative fall in sea-level and effect on porosity and permeability, Las Negras area, southeastern Spain

NASA Astrophysics Data System (ADS)

Li, Zhaoqi; Goldstein, Robert H.; Franseen, Evan K.

2017-03-01

A dolomitized Upper Miocene carbonate system in southeast Spain contains extensive upper and lower zones of calcite cementation that cut across the stratigraphy. Cement textures including isopachous and circumgranular, which are consistent with phreatic-zone cementation. Cements in the upper cemented zone are non-luminescent, whereas those in the lower cemented zone exhibit multiple bands of luminescent and non-luminescent cements. In the upper cemented zone, isotopic data show two meteoric calcite lines (MCL) with mean δ18O at - 5.1‰ and - 5.8‰ VPDB, whereas no clear MCL is defined in the lower cemented zone where mean δ18O for calcite cement is at - 6.7‰ VPDB. δ13C values in both cement zones are predominantly negative, ranging from - 10 to + 2‰ VPDB, suggestive of carbon from soil gas or decayed organics. Measurements of Tm ice in primary fluid inclusions yield a mode of 0.0 °C in both zones, indicating calcite cementation from fresh water. These two zones define the positions of two different paleo-water tables that formed during a relative sea-level fall and erosional downcutting during the Plio-Pleistocene. The upper cemented zone pre-dated the lower cemented zone on the basis of known relative sea-level history. Meteoric calcite cementation reduced porosity and permeability, but measured values are inconsistent with simple filling of open pore space. Each texture, boundstone, grainstone, packstone, wackestone, produces a different relationship between percent calcite cement and porosity/permeability. Distribution of cements may be predictable on the basis of known sea-level history, and the effect of the cementation can be incorporated into subsurface geomodels by defining surfaces of rock boundaries that separate cemented zones from uncemented zones, and applying texture-specific relationships among cementation, porosity and permeability.

Seismic evidence for an extensive gas-bearing layer at shallow depth, offshore from Prudhoe Bay, Alaska

USGS Publications Warehouse

Boucher, G.; Reimnitz, E.; Kempema, E.

1981-01-01

High-resolution seismic reflection data, recorded offshore from Prudhoe Bay, Alaska, were processed digitally to determine the reflectivity structure of the uppermost layers of the seafloor. A prominent reflector, found at 27 m below the mud line (water depths 7-9 m), has a negative reflection coefficient greater than 0.5. The large acoustic impedance contrast, coupled with a report of gas encountered at a corresponding depth in a nearby drillhole, shows that the reflector is the upper boundary of a zone containing gas. The gas exists in sandy gravel capped by stiff, silty clay. Analysis of unprocessed conventional high-resolution records from the region indicates that the gas-bearing layer may extend over an area of at least 50 km2 at a depth of 20-35 m below the mud line. Similar-appearing reflectors (Reimnitz, 1972), previously unexplained, occur in patches over wide regions of the shelf where offshore oil development is beginning at a rapid pace. This suggests the exercise of caution with respect to possible hazards from shallow gas pockets.

Habitable Planets with Dynamic System of Global Air-Liquid-Solid Planet and Life

NASA Astrophysics Data System (ADS)

Miura, Y.; Kato, T.

2017-11-01

Habitable zone is dynamic three phase states (air-liquid-solid), which will be obtained in water-planet with volatile exchanges. Water and carbon-bearing grains at older extraterrestrial stones suggest that there are no global ocean water system.

Silicate melts density, buoyancy relations and the dynamics of magmatic processes in the upper mantle

NASA Astrophysics Data System (ADS)

Sanchez-Valle, Carmen; Malfait, Wim J.

2016-04-01

Although silicate melts comprise only a minor volume fraction of the present day Earth, they play a critical role on the Earth's geochemical and geodynamical evolution. Their physical properties, namely the density, are a key control on many magmatic processes, including magma chamber dynamics and volcanic eruptions, melt extraction from residual rocks during partial melting, as well as crystal settling and melt migration. However, the quantitative modeling of these processes has been long limited by the scarcity of data on the density and compressibility of volatile-bearing silicate melts at relevant pressure and temperature conditions. In the last decade, new experimental designs namely combining large volume presses and synchrotron-based techniques have opened the possibility for determining in situ the density of a wide range of dry and volatile-bearing (H2O and CO2) silicate melt compositions at high pressure-high temperature conditions. In this contribution we will illustrate some of these progresses with focus on recent results on the density of dry and hydrous felsic and intermediate melt compositions (rhyolite, phonolite and andesite melts) at crustal and upper mantle conditions (up to 4 GPa and 2000 K). The new data on felsic-intermediate melts has been combined with in situ data on (ultra)mafic systems and ambient pressure dilatometry and sound velocity data to calibrate a continuous, predictive density model for hydrous and CO2-bearing silicate melts with applications to magmatic processes down to the conditions of the mantle transition zone (up to 2773 K and 22 GPa). The calibration dataset consist of more than 370 density measurements on high-pressure and/or water-and CO2-bearing melts and it is formulated in terms of the partial molar properties of the oxide components. The model predicts the density of volatile-bearing liquids to within 42 kg/m3 in the calibration interval and the model extrapolations up to 3000 K and 100 GPa are in good agreement with results from ab initio calculations. The density model has been applied to examine the mineral-melt buoyancy relations at depth and the implications of these results for the dynamics of magma chambers, crystal settling and the stability and mobility of magmas in the upper mantle will be discussed.

Water-table and potentiometric-surface altitudes of the upper glacial, Magothy, and Lloyd aquifers on Long Island, New York, in March-April 2000, with a summary of hydrogeologic conditions

USGS Publications Warehouse

Busciolano, Ronald J.

2002-01-01

The three main water-bearing units on Long Island, New York--the upper glacial aquifer (water table) and the underlying Magothy and Lloyd aquifers--are the sole source of water supply for more than 3 million people. Water-table and potentiometric-surface altitudes were contoured from water-level measurements made at 394 observation, public-supply, and industrial-supply wells during March-April 2000. In general, water-level altitudes in the upper glacial, Magothy, and Lloyd aquifers were lower throughout most parts of Long Island than those measured during March-April 1997. Changes in altitude during this period ranged from an increase of about 6 feet in the Magothy aquifer in southwestern Nassau County to a decrease of more than 8 feet in the upper glacial aquifer in eastern Suffolk County.

Use of joint-growth directions and rock textures to infer thermal regimes during solidification of basaltic lava flows

NASA Astrophysics Data System (ADS)

Degraff, James M.; Long, Philip E.; Aydin, Atilla

1989-09-01

Thermal contraction joints form in the upper and lower solidifying crusts of basaltic lava flows and grow toward the interior as the crusts thicken. Lava flows are thus divided by vertical joints that, by changes in joint spacing and form, define horizontal intraflow layers known as tiers. Entablatures are tiers with joint spacings less than about 40 cm, whereas colonnades have larger joint spacings. We use structural and petrographic methods to infer heat-transfer processes and to constrain environmental conditions that produce these contrasting tiers. Joint-surface morphology indicates overall joint-growth direction and thus identifies the level in a flow where the upper and lower crusts met. Rock texture provides information on relative cooling rates in the tiers of a flow. Lava flows without entablature have textures that develop by relatively slow cooling, and two joint sets that usually meet near their middles, which indicate mostly conductive cooling. Entablature-bearing flows have two main joint sets that meet well below their middles, and textures that indicate fast cooling of entablatures and slow cooling of colonnades. Entablatures always occur in the upper joint sets and sometimes alternate several times with colonnades. Solidification times of entablature-bearing flows, constrained by lower joint-set thicknesses, are much less than those predicted by a purely conductive cooling model. These results are best explained by a cooling model based on conductive heat transfer near a flow base and water-steam convection in the upper part of an entablature-bearing flow. Calculated solidification rates in the upper parts of such flows exceed that of the upper crust of Kilauea Iki lava lake, where water-steam convection is documented. Use of the solidification rates in an available model of water-steam convection yields permeability values that agree with measured values for fractured crystalline rock. We conclude, therefore, that an entablature forms when part of a flow cools very rapidly by water-steam convection. Flooding of the flow top by surface drainage most likely induces the convection. Colonnades form under conditions of slower cooling by conductive heat transfer in the absence of water.

Double diffusion in the frontal zones of the Yellow and East China Seas in winter

NASA Astrophysics Data System (ADS)

Oh, K.; Lee, S.

2017-12-01

Where the cold, fresh water of the Yellow Sea (YS) and the warm, salty water of the East China Sea (ECS) meet, northern and southern fronts are formed in the southeastern YS and the northwestern ECS, respectively. Strong thermohaline fronts are formed on the northern front, and a strong thermocline and a temperature reversal phenomenon are represented in this front. To understand the water structure of this thermohaline zone, we examined double diffusion in the frontal zones in February 2003 using hydrographic data. In the northern front, the warm, salty Cheju Warm Current Water (CWCW) moved northwards along the bottom layer and the cold, fresh Yellow Sea Cold Water (YSCW) flowed southward in the upper layer. As a result, strong thermohaline fronts forms in the area where the two water masses met, and the slope was developed downward across the front. In this area, a strong thermocline and temperature reversal structures were present. The cold, fresh Korean Coastal Water (KCW) was also found in the upper layer near the thermocline, and has a low-temperature, low-salinity more than surrounding water. When cold, fresh water is located over warm, salty water, heat diffuses through the interface between the two water masses, and then the diffusive-convection can be expected to occur. On the other hand, when warm, salty water overlays cold, fresh water, heat in the upper layer is preferentially transferred downward, and the salt-fingering occurs. The diffusive-convection occurs predominantly in the northern thermohaline front, where the cold, fresh YSCW is situated above the warm, salty CWCW and has the effect of strengthening stratification, so that the water column maintains a physically stable structure. In addition, this phenomenon seems to play a role in maintaining the reversal structure. The salt-fingering occurs in upper layers of the northern front where the cold, fresh YSCW is located over the most cold, fresh KCW. Near the northern thermo-halocline zone, the salt-fingering occurs simultaneously with the diffusive-convection, because three water masses, YSCW, KCW and CWCW, interact in that area. Therefore, it can be seen that the water structure of the northern frontal zone in winter is influenced mainly by the cold, fresh YSCW, the most cold, fresh KCW, and the warm, salty CWCW.

Catalytic destruction of groundwater contaminants in reactive extraction wells

DOEpatents

McNab, Jr., Walt W.; Reinhard, Martin

2002-01-01

A system for remediating groundwater contaminated with halogenated solvents, certain metals and other inorganic species based on catalytic reduction reactions within reactive well bores. The groundwater treatment uses dissolved hydrogen as a reducing agent in the presence of a metal catalyst, such a palladium, to reduce halogenated solvents (as well as other substituted organic compounds) to harmless species (e.g., ethane or methane) and immobilize certain metals to low valence states. The reactive wells function by removing water from a contaminated water-bearing zone, treating contaminants with a well bore using catalytic reduction, and then reinjecting the treated effluent into an adjacent water-bearing zone. This system offers the advantages of a compact design with a minimal surface footprint (surface facilities) and the destruction of a broad suite of contaminants without generating secondary waste streams.

SOIL ALUMINUM DISTRIBUTION IN THE NEAR-STREAM ZONE AT THE BEAR BROOK WATERSHED IN MAINE

EPA Science Inventory

Near-stream and upslope soil chemical properties were analyzed to infer linkages between soil and surface water chemistry at the Bear Brook Watershed in Maine [BBWM]. Organic and mineral soil samples were collected along six 20 m transects perpendicular to the stream and one 200 ...

Geochemistry and origins of mineralized waters in the Floridan aquifer system, northeastern Florida

USGS Publications Warehouse

Phelps, G.G.

2001-01-01

Increases in chloride concentration have been observed in water from numerous wells tapping the Floridan aquifer system in northeastern Florida. Although most increases have been in the eastern part of Duval County, Florida, no spatial pattern in elevated chloride concentrations is discernible. Possible sources of the mineralized water include modern seawater intrusion; unflushed Miocene-to-Pleistocene-age seawater or connate water in aquifer sediments; or mineralized water from deeper zones of the aquifer system or from formations beneath the Floridan aquifer system. The purpose of this study was to document the chemical and isotopic characteristics of water samples from various aquifer zones, and from geochemical and hydrogeologic data, to infer the source of the increased mineralization. Water samples were collected from 53 wells in northeastern Florida during 1997-1999. Wells tapped various zones of the aquifer including: the Fernandina permeable zone (FPZ), the upper zone of the Lower Floridan aquifer (UZLF), the Upper Floridan aquifer (UFA), and both the UFA and the UZLF. Water samples were analyzed for major ions and trace constituents and for isotopes of carbon, oxygen, hydrogen, sulfur, strontium, chlorine, and boron. Samples of rock from the aquifer were analyzed for isotopes of oxygen, carbon, and strontium. In general, water from various aquifer zones cannot be differentiated based on chemistry, except for water from FPZ wells. Major-ion concentrations vary as much within the upper zone of the Lower Floridan aquifer and the Upper Floridan aquifer as between these two zones. Simple models of mixing between fresh ground water and either modern seawater or water from the FPZ as a mineralized end member show that many water samples from the UZLF aquifer and the UFA are enriched in bicarbonate, calcium, magnesium, sulfate, fluoride, and silica and are depleted in sodium and potassium (as compared to concentrations predicted by simple mixing). Chemical mass-balance models of mixing and reactions between a hypothetical initial seawater and aquifer minerals cannot account for the observed water chemistry in a few wells, implying a source other than seawater, either ancient or modern, or the occurrence of other more complex rock-water reactions. Hydrogeologic and geochemical data from water and aquifer samples indicate that the most likely source of mineralized water in some wells yielding water with increasing chloride concentrations is water from the FPZ. In other wells, the flushing of Miocene-to-Pleistocene-age seawater can account for the observed chloride concentrations. The fact that most of the water samples collected are a mixture of less than one percent of mineralized water with more than 99 percent fresh or recharge water makes identifying the source of the mineralized water difficult. Differences in carbon-14 and sulfur-34 values probably reflect areal differences in aquifer mineralogy and distribution of organic carbon related to paleokarst features. Geochemical mass-balance models of seawater-rock interaction are unable to account for the chemical and isotopic composition of mineralized water from the FPZ, which implies another source of mineralized water, such as a brine, or the occurrence of more complex water-rock reactions.

Dissolved organic carbon concentrations and compositions, and trihalomethane formation potentials in waters from agricultural peat soils, Sacramento-San Joaquin Delta, California; implications for drinking-water quality

USGS Publications Warehouse

Fujii, Roger; Ranalli, Anthony J.; Aiken, George R.; Bergamaschi, Brian A.

1998-01-01

Water exported from the Sacramento-San Joaquin River delta (Delta) is an important drinking-water source for more than 20 million people in California. At times, this water contains elevated concentrations of dissolved organic carbon and bromide, and exceeds the U.S. Environmental Protection Agency's maximum contaminant level for trihalomethanes of 0.100 milligrams per liter if chlorinated for drinking water. About 20 to 50 percent of the trihalomethane precursors to Delta waters originates from drainage water from peat soils on Delta islands. This report elucidates some of the factors and processes controlling and affecting the concentration and quality of dissolved organic carbon released from peat soils and relates the propensity of dissolved organic carbon to form trihalomethanes to its chemical composition.Soil water was sampled from near-surface, oxidized, well-decomposed peat soil (upper soil zone) and deeper, reduced, fibrous peat soil (lower soil zone) from one agricultural field in the west central Delta over 1 year. Concentrations of dissolved organic carbon in the upper soil zone were highly variable, with median concentrations ranging from 46.4 to 83.2 milligrams per liter. Concentrations of dissolved organic carbon in samples from the lower soil zone were much less variable and generally slightly higher than samples from the upper soil zone, with median concentrations ranging from 49.3 to 82.3 milligrams per liter. The dissolved organic carbon from the lower soil zone had significantly higher aromaticity (as measured by specific ultraviolet absorbance) and contained significantly greater amounts of aromatic humic substances (as measured by XAD resin fractionation and carbon-13 nuclear magnetic resonance analysis of XAD isolates) than the dissolved organic carbon from the upper soil zone. These results support the conclusion that more aromatic forms of dissolved organic carbon are produced under anaerobic conditions compared to aerobic conditions. Dissolved organic carbon concentration, trihalomethane formation potential, and ultraviolet absorbance were all highly correlated, showing that trihalomethane precursors increased with increasing dissolved organic carbon and ultraviolet absorbance for whole water samples. Contrary to the generally accepted conceptual model for trihalomethane formation that assumes that aromatic forms of carbon are primary precursors to trihalomethanes, results from this study indicate that dissolved organic carbon aromaticity appears unrelated to trihalomethane formation on a carbon-normalized basis. Thus, dissolved organic carbon aromaticity alone cannot fully explain or predict trihalomethane precursor content, and further investigation of aromatic and nonaromatic forms of carbon will be needed to better identify trihalomethane precursors.

Numerical studies of gas production from several CH4 hydrate zones at the Mallik site, Mackenzie Delta, Canada

USGS Publications Warehouse

Moridis, G.J.; Collett, T.S.; Dallimore, S.R.; Satoh, T.; Hancock, S.; Weatherill, B.

2004-01-01

The Mallik site represents an onshore permafrost-associated gas hydrate accumulation in the Mackenzie Delta, Northwest Territories, Canada. A gas hydrate research well was drilled at the site in 1998. The objective of this study is the analysis of various gas production scenarios from five methane hydrate-bearing zones at the Mallik site. In Zone #1, numerical simulations using the EOSHYDR2 model indicated that gas production from hydrates at the Mallik site was possible by depressurizing a thin free gas zone at the base of the hydrate stability field. Horizontal wells appeared to have a slight advantage over vertical wells, while multiwell systems involving a combination of depressurization and thermal stimulation offered superior performance, especially when a hot noncondensible gas was injected. Zone #2, which involved a gas hydrate layer with an underlying aquifer, could yield significant amounts of gas originating entirely from gas hydrates, the volumes of which increased with the production rate. However, large amounts of water were also produced. Zones #3, #4 and #5 were lithologically isolated gas hydrate-bearing deposits with no underlying zones of mobile gas or water. In these zones, thermal stimulation by circulating hot water in the well was used to induce dissociation. Sensitivity studies indicated that the methane release from the hydrate accumulations increased with the gas hydrate saturation, the initial formation temperature, the temperature of the circulating water in the well, and the formation thermal conductivity. Methane production appears to be less sensitive to the specific heat of the rock and of the hydrate, and to the permeability of the formation. ?? 2004 Published by Elsevier B.V.

Impact of the geological structures on the groundwater potential using geophysical techniques in West Bani Mazar area, El Minia - Western Desert, Egypt

NASA Astrophysics Data System (ADS)

Mahmoud, Hussein Hosni; Kotb, Adel Diab Mohammed

2017-06-01

Establishment of the new agricultural projects in west Bani Mazar area, El Minia, Egypt needs a good knowledge about groundwater. Groundwater serves as the unique source of water supplies in the study area. Vertical Electrical Sounding technique is a convenient tool for groundwater exploration. This technique was utilized to illustrate the geoelectric succession, vertical and spatial extensions of the encountered layers, depth to water bearing layers and the structures affecting these layers. Profiling technique was carried out along a grid pattern using different half current electrode spacings (150 m, 300 m and 500 m) to clarify changes in resistivity values throughout the study area at different depths. Geoelectric layers B1 and B2 of the saturated zone are suitable for groundwater extraction in the study area. The resistivity values of the geoelectric layer B1 decrease towards the West direction, they decrease from 23.0 Ωm to 16.0 Ωm; and its thicknesses increase towards the SE direction from 12.0 m to 18.0 m. Whereas, the resistivity values of the geoelectric layer B2 decrease towards the NW direction from 40.0 Ωm to 26.5 Ωm; and its thicknesses vary from 34.0 m to 40.0 m. The depths to the upper surface of the water bearing layer B1 increase towards the NW direction from 44.0 m to 89.4 m. Based on the results obtained from the Vertical Electrical Soundings, four two-dimensional resistivity imaging profiles were measured at the selected sites. These 2-D resistivity profiles aim to determine depths to the water bearing layers, their thicknesses and the shallow structure. The inverted models of these profiles matched with the geoelectric sequence at these sites. In addition, a normal fault is detected at the northwestern part of the study area. According to the results obtained from this study it is clear that the groundwater in the area under consideration is occurred in the fractured limestone layers that belong to Eocene Age. Resistivity values of the water bearing layers increase with depth as a result of decreasing fracture density; and these values decreased towards the northwestern direction due to their proximity from the fault zone. The groundwater potential of these layers depends mainly on the lithologic composition and the geological structures affecting these layers. The secondary porosity of these limestone layers depends mainly on the degree of fracturing and fissuring. The proper sites to drill new productive wells were recommended, and the obtained data from drilling new well in the southeastern part of the study area coincide with the interpreted data of the different geophysical techniques.

Genetic implications of the trace element distribution pattern in the upper knox carbonate rocks, copper ridge district, East Tennessee

NASA Astrophysics Data System (ADS)

Churnet, Habte G.; Misra, Kula C.

1981-11-01

The Lower Ordovician, Upper Knox Group rocks (the Kingsport and Mascot formations) in the Copper Ridge district consist predominantly of fine-grained dolostones, medium and coarser grained dolostones, and limestones. Dolomite crystals of medium and coarser grained dolostones show up to eight cathodoluminescent zones of variable width and intensity. Electron microprobe analyses indicate that the zoning is related to variation in Fe/Mn ratios, the brighter luminescent zones corresponding to lower ratios. Superposed on this growth zoning is a compositional zoning characterized by a general increase in Fe from core to rim of individual dolomite crystals. Field and petrographic studies (Churnet, 1979; Churnet et al., 1981) indicate that the fine-grained dolostones formed in supratidal to upper intratidal environments, whereas the precursor lime muds of the limestones as well as of the medium and coarser grained dolostones formed in shallow subtidal to lower intertidal environments. The large areal extent of the dolostones must have required a regionally abundant source of Mg such as marine water. Yet, both limestones and dolostones have low Na and Sr contents suggestive of their formation in solutions more dilute than normal marine water. It is proposed that the fine-grained dolostones formed by aggradation of initially very fine-grained dolostones in presence of fresh water, and that the limestones stabilized and the medium and coarser grained dolostones formed in environments of mixed marine and fresh waters. Considered in the light of ordering of partition coefficients, such a mixing model can account for the observed correlation pattern of trace elements (especially, SMn and SrFe) as well as the Fe distribution in the zoned dolomite crystals. Variation of the partition coefficient of Mn due to fluctuations in the relative proportions of fresh and marine waters in the diagenetic solution may explain the different Fe/Mn ratios observed in the growth zones (luminescence bands) of zoned dolomite crystals.

Shallow methane hydrate system controls ongoing, downslope sediment transport in a low-velocity active submarine landslide complex, Hikurangi Margin, New Zealand

NASA Astrophysics Data System (ADS)

Mountjoy, Joshu J.; Pecher, Ingo; Henrys, Stuart; Crutchley, Gareth; Barnes, Philip M.; Plaza-Faverola, Andreia

2014-11-01

Morphological and seismic data from a submarine landslide complex east of New Zealand indicate flow-like deformation within gas hydrate-bearing sediment. This "creeping" deformation occurs immediately downslope of where the base of gas hydrate stability reaches the seafloor, suggesting involvement of gas hydrates. We present evidence that, contrary to conventional views, gas hydrates can directly destabilize the seafloor. Three mechanisms could explain how the shallow gas hydrate system could control these landslides. (1) Gas hydrate dissociation could result in excess pore pressure within the upper reaches of the landslide. (2) Overpressure below low-permeability gas hydrate-bearing sediments could cause hydrofracturing in the gas hydrate zone valving excess pore pressure into the landslide body. (3) Gas hydrate-bearing sediment could exhibit time-dependent plastic deformation enabling glacial-style deformation. We favor the final hypothesis that the landslides are actually creeping seafloor glaciers. The viability of rheologically controlled deformation of a hydrate sediment mix is supported by recent laboratory observations of time-dependent deformation behavior of gas hydrate-bearing sands. The controlling hydrate is likely to be strongly dependent on formation controls and intersediment hydrate morphology. Our results constitute a paradigm shift for evaluating the effect of gas hydrates on seafloor strength which, given the widespread occurrence of gas hydrates in the submarine environment, may require a reevaluation of slope stability following future climate-forced variation in bottom-water temperature.

Simulation of ground-water flow and stream-aquifer relations in the vicinity of the Savannah River Site, Georgia and South Carolina, predevelopment through 1992

USGS Publications Warehouse

Clarke, John S.; West, Christopher T.

1998-01-01

Ground-water flow and stream-aquifer relations were simulated for seven aquifers in Coastal Plain sediments in the vicinity of the U.S. Department of Energy, Savannah River Site (SRS), in Georgia and South Carolina to evaluate the potential for ground water containing hazardous materials to migrate from the SRS into Georgia through aquifers underlying the Savannah River (trans-river flow). The work was completed as part of a cooperative study between the U.S. Geological Survey, the U.S. Department of Energy, and Georgia Department of Natural Resources. The U.S. Geological Survey three-dimensional finite-difference ground-water flow model, MODFLOW, was used to simulate ground-water flow in three aquifer systems containing seven discrete aquifers: (1) the Floridan aquifer system, consisting of the Upper Three Runs and Gordon aquifers in sediments of Eocene age; (2) the Dublin aquifer system, consisting of the Millers Pond, and upper and lower Dublin aquifers in sediments of Paleocene and Late Cretaceous age; and (3) the Midville aquifer system, consisting of the upper and lower Midville aquifers of sediments in Late Cretaceous age. Ground-water flow was simulated using a series of steady-state simulations of predevelopment (pre-1953) conditions and six pumping periods--1953-60, 1961-70, 1971-75, 1976-80, 1981-86, and 1987-92--results are presented for predevelopment (prior to 1953) and modern-day (1987-92) conditions. Total simulated predevelopment inflow is 1,023 million gallons per day (Mgal/d), of which 76 percent is contributed by leakage from the Upper Three Runs aquifer. Over most of the study area, pumpage induced changes in ground-water levels, ground-water discharge to streams, and water-budget components were small during 1953-92, and changes in aquifer storage were insignificant. Simulated drawdown between predevelopment and modern-day conditions is small (less than 7 feet) and of limited areal extent--the largest simulated declines occur in the upper and lower Dublin aquifers in the vicinity of the Sandoz plant site in South Carolina. These declines extend beneath the Savannah River and change the configuration of the simulated potentiometric surface and flow paths near the river. Predevelopment and modern-day flowpaths were simulated near the Savannah River by using the U.S. Geological Survey particle-tracking code MODPATH. Eastward and westward zones of trans-river flow were identified in three principal areas as follows: --zone 1-from the Fall Line southward to the confluence of Hollow Creek and the Savannah River; --zone 2-from the zone 1 boundary southward to the southern border of the SRS (not including the Lower Three Runs Creek section); and --zone 3-from the zone 2 boundary, southward into the northern part of Screven County, Ga. All zones for all model layers were located within or immediately adjacent to the Savannah River alluvial valley and most were located in the immediate vicinity of the Savannah River. Recharge areas for each of the zones of trans-river flow generally are in the vicinity of major interstream drainage divides. Mean time-of-travel simulated for predevelopment conditions ranges from 300 to 24,000 years for westward trans-river flow zones; and from 550 to 41,000 years for eastward zones. Corresponding travel times under modern-day conditions range from 300 to 34,000 years for westward zones and from 580 to 31,000 years for eastward zones. Differences in travel times between predevelopment and modern-day simulations result from changes in hydraulic gradients due to ground-water pumpage that alter flow paths in the vicinity of the river. Recharge to Georgia trans-river flow zones originating on the SRS was simulated for the Gordon and upper Dublin aquifers during predevelopment, and in the Gordon aquifer during 1987-92. During 1987-92, SRS recharge was simulated in 6 model cells covering a 2-square mile area, located away from areas of ground-water contamination. Si

Peat characteristics and groundwater geochemistry of calcareous fens in the Minnesota River Basin, U.S.A

USGS Publications Warehouse

Almendinger, J.E.; Leete, J.H.

1998-01-01

. Calcareous fens in Minnesota are spring-seepage peatlands with a distinctive flora of rare calciphilic species. Peat characteristics and groundwater geochemistry were determined for six calcareous fens in the Minnesota River Basin to better understand the physical structure and chemical processes associated with stands of rare vegetation. Onset of peat accumulation in three of the fens ranged from about 4,700 to 11,000 14C yrs BP and probably resulted from a combination of climate change and local hydrogeologic conditions. Most peat cores had a carbonate-bearing surface zone with greater than 10% carbonates (average 27%, dry wt basis), an underlying carbonate-depleted zone with 10% or less carbonates (average 4%), and a carbonate-bearing lower zone again with greater than 10% carbonates (average 42%). This carbonate zonation was hypothesized to result from the effect of water-table level on carbonate equilibria: carbonate precipitation occurs when the water table is above a critical level, and carbonate dissolution occurs when the water table is lower. Other processes that changed the major ion concentrations in upwelling groundwater include dilution by rain water, sulfate reduction or sulfide oxidation, and ion adsorption or exchange. Geochemical modeling indicated that average shallow water in the calcareous fens during the study period was groundwater mixed with about 6 to 13% rain water. Carbonate precipitation in the surface zone of calcareous fens could be decreased by a number of human activities, especially those that lower the water table. Such changes in shallow water geochemistry could alter the growing conditions that apparently sustain rare fen vegetation.

Biostratigraphy and event stratigraphy in Iran around the Permian Triassic Boundary (PTB): Implications for the causes of the PTB biotic crisis

NASA Astrophysics Data System (ADS)

Kozur, H. W.

2007-01-01

The conodont succession and stratigraphic events around the Permian-Triassic boundary (PTB) have been investigated in detail in the open sea deposits of Iran (Abadeh and Shahreza in central Iran, and Jolfa and Zal in northwestern Iran). This investigation produced a very detailed conodont zonation from the Clarkina nodosa Zone up to the Isarcicella isarcica Zone. All significant events have been accurately located and dated within this zonation, and the duration of most of these conodont zones has been calculated by cross-correlation with continental lake deposits that display obvious Milankovitch cyclicity. The unusually short duration of all conodont zones in the interval from the C. nodosa up to the Hindeodus parvus Zone indicates that there was persistent high ecological stress during this time interval. Most of the conodont zones can be accurately correlated with South China. In the interval from the C. hauschkei Zone to the H. parvus Zone, even correlation with the Arctic is possible. Within three thin stratigraphic intervals, the Changhsingian (Dorashamian) warm water conodont fauna of the C. subcarinata lineage is replaced by a cool water fauna with small H. typicalis, rare Merrillina sp., and cool water Clarkina that have very widely spaced denticles. The uppermost cool water fauna horizon comprises the lower C. zhangi Zone and can be accurately correlated with continental beds by recognition of a short reversed magnetozone below the long uppermost Permian-lowermost Triassic normal magnetozone. In Iran and Transcaucasia, this short reversed zone comprises the upper C. changxingensis- C. deflecta Zone and most of the C. zhangi Zone. Its top lies 50 cm below the top of the Paratirolites Limestone (s.s.) in the Dorasham 2 section, which is at the beginning of the upper quarter of the C. zhangi Zone. In the Germanic Basin, this short palaeomagnetic interval comprises the lower and the basal part of the upper Fulda Formation. On the Russian Platform, the Nedubrovo Formation belongs to this short reversed magnetic interval. In its upper part (corresponding to the top of the lower C. zhangi Zone, see above) there is a fallout of mafic tuffs from the Siberian Trap event that originated about 3000 km away in eruption centres in the Siberian Tungusska Basin. In the Germanic Basin and in Iran, this horizon contains volcanic microsphaerules. Thus, a direct correlation can be made between the immigration of a cool water fauna into the tropical realm and an exceptionally strong interval of explosive activity during the Siberian Trap volcanic episode. These faunal changes are the same as those found at the base of the Boundary Clay, suggesting that a short cooling event at this horizon also was due to intense volcanism. Additional influence by a bolide impact cannot be excluded. Most of the events in the interval from the C. nodosa up to the I. isarcica Zone (upper Changhsingian to middle Gangetian) in the Iranian sections can be also observed in other marine sections (e.g., in Meishan) and even in continental sections of the Germanic Basin. Of particular significance is the fact that, in the investigated Iranian sections, the PTB lies either in red sediments or in light grey sediments (as in Abadeh) that contain an ostracod fauna indicative of highly oxygenated bottom waters. Therefore, anoxia cannot be the reason for the PTB extinction event in this region, even though anoxia does cause locally or regionally elsewhere an overprint on the extinction event.

Hydrodynamic caracterisation of an heterogeneous aquifer system under semi-arid climate

NASA Astrophysics Data System (ADS)

Drias, T.; Toubal, A. Ch

2009-04-01

The studied zone is a part of the Mellegne's (North-East of Algeria) under pound, this zone is characterised by its semi-arid climate. The water bearing system is formed by the plio-quaternairy alluviums resting on a marley substratuim of age Eocene. The geostatiscitcs approach of the hydrodynamics parameters (Hydrolic load, transmisivity) allowed the study of their spatial distrubution (casting) by the method of Krigeage by blocks and the identification of zones with water-bearing potentialities. In this respect, the zone of Ain Chabro which, is situated in the South of the plain shows the best values of the transmisivity...... The use of a bidimensinnel model in the differences ended in the permanent regime allowed us to establish the global balence sheet (overall assessment) of the tablecloth and to refine the transmisivity field. These would vary more exactley between 10-4 to 10-2 m²/s. The method associating the probability appraoch of Krigeage to that determining the model has facilited the wedging of the model and clarified the inflitration value. Keys words: hydrodynamics, geostatiscitcs, Modeling, Chabro, Tébessa.

Effects of aquifer heterogeneity on ground-water flow and chloride concentrations in the Upper Floridan aquifer near and within an active pumping well field, west-central Florida

USGS Publications Warehouse

Tihansky, A.B.

2005-01-01

Chloride concentrations have been increasing over time in water from wells within and near the Eldridge-Wilde well field, near the coast in west-central Florida. Variable increases in chloride concentrations from well to well over time are the combined result of aquifer heterogeneity and ground-water pumping within the Upper Floridan aquifer. Deep mineralized water and saline water associated with the saltwater interface appear to move preferentially along flow zones of high transmissivity in response to ground-water withdrawals. The calcium-bicarbonate-type freshwater of the Upper Floridan aquifer within the study area is variably enriched with ions by mixing with introduced deep and saline ground water. The amount and variability of increases in chloride and sulfate concentrations at each well are related to well location, depth interval, and permeable intervals intercepted by the borehole. Zones of high transmissivity characterize the multilayered carbonate rocks of the Upper Floridan aquifer. Well-developed secondary porosity within the Tampa/Suwannee Limestones and the Avon Park Formation has created producing zones within the Upper Floridan aquifer. The highly transmissive sections of the Avon Park Formation generally are several orders of magnitude more permeable than the Tampa/Suwannee Limestones, but both are associated with increased ground-water flow. The Ocala Limestone is less permeable and is dominated by primary, intergranular porosity. Acoustic televiewer logging, caliper logs, and borehole flow logs (both electromagnetic and heat pulse) indicate that the Tampa/Suwannee Limestone units are dominated by porosity owing to dissolution between 200 and 300 feet below land surface, whereas the porosity of the Avon Park Formation is dominated by fractures that occur primarily from 600 to 750 feet below land surface and range in angle from horizontal to near vertical. Although the Ocala Limestone can act as a semiconfining unit between the Avon Park Formation and the Tampa/Suwannee Limestones, seismic-reflection data and photolinear analyses indicate that fractures and discontinuities in the Ocala Limestone are present within the southwestern part of the well field. It is possible that some fracture zones extend upward from the Avon Park Formation through the Ocala, Suwannee, and Tampa Limestones to land surface. These fractures may provide a more direct hydrologic connection between transmissive zones that are vertically separated by less permeable stratigraphic units. Ground water moves along permeable zones within the Upper Floridan aquifer in response to changes in head gradients as a result of pumping. Borehole geophysical measurements, including flow logs, specific conductance logs, and continuous monitoring of specific conductance at selected fixed depths, indicate that borehole specific conductance varies substantially with time and in response to pumping stresses. Ground-water mixing between hydrogeologic units likely occurs along highly transmissive zones and within boreholes of active production wells. Ground-water movement and water-quality changes were greatest along the most transmissive zones. Variable mixing of three water-type end members (freshwater, deepwater, and saltwater) occurs throughout the study area. Both deepwater and saltwater are likely sources for elevated chloride and sulfate concentrations in ground water. Mass-balance calculations of mixtures of the three end members indicate that deepwater is found throughout the aquifer units. Samples from wells within the southwestern part of the well field indicate that deepwater migrates into the shallow permeable units in the southwestern part of the well field. Deepwater contributes to elevated sulfate and chloride concentrations, which increase with depth and are elevated in wells less than 400 feet deep. The greatest increases in chloride concentrations over time are found in water from wells closest to the saltwater interface. Gro

Hydrogeology at Air Force Plant 4 and vicinity and water quality of the Paluxy Aquifer, Fort Worth, Texas

USGS Publications Warehouse

Kuniansky, Eve L.; Jones, Sonya A.; Brock, Robert D.; Williams, M.D.

1996-01-01

Ground water in the surficial terrace alluvial aquifer is contaminated at Air Force Plant 4, Fort Worth, Texas, and at the adjacent Naval Air Station. Some of the contaminated water has leaked from the terrace alluvial aquifer to an uppermost interval of the Paluxy Formation (the Paluxy "upper sand") beneath the east parking lot, east of the assembly building, and to the upper and middle zones of the Paluxy aquifer near Bomber Road, west of the assembly building. Citizens are concerned that contaminants from the plant, principally trichloroethylene and chromium might enter nearby municipal and domestic wells that pump water from the middle and lower zones of the Paluxy aquifer. Geologic formations that crop out in the study area, from oldest to youngest, are the Paluxy Formation (aquifer), Walnut Formation (confining unit), and Goodland Limestone (confining unit). Beneath the Paluxy Formation is the Glen Rose Formation (confining unit) and Twin Mountains Formation (aquifer). The terrace alluvial deposits overlie these Cretaceous rocks. The terrace alluvial aquifer, which is not used for municipal water supply, is separated from the Paluxy aquifer by the Goodland-Walnut confining unit. The confining unit restricts the flow of ground water between these aquifers in most places; however, downward leakage to the Paluxy aquifer might occur through the "window," where the confining unit is thin or absent. The Paluxy aquifer is divided into upper, middle, and lower zones. The Paluxy "upper sand" underlying the "window" is an apparently isolated, mostly unsaturated, sandy lens within the uppermost part of the upper zone. The Paluxy aquifer is recharged by leakage from Lake Worth and by precipitation on the outcrop area. Discharge from the aquifer primarily occurs as pumpage from municipal and domestic wells. The Paluxy aquifer is separated from the underlying Twin Mountains aquifer by the Glen Rose confining unit. Water-level maps indicate that (1) ground water in the terrace alluvial aquifer appears to flow outward, away from Air Force Plant 4; (2) a ground-water mound, possibly caused by downward leakage from the terrace alluvial aquifer, is present in the Paluxy "upper sand" beneath the "window;" and (3) lateral ground-water flow in regionally extensive parts of the Paluxy aquifer is from west to east-southeast. Trichloroethylene concentrations at Air Force Plant 4 have ranged from about 10,000 to about 100,000 micrograms per liter in the terrace alluvial aquifer, from 8,000 to 11,000 micrograms per liter in the Paluxy "upper sand," and from 2 to 50 micrograms per liter in the upper and middle zones of the Paluxy aquifer. Chromium concentrations at Air Force Plant 4 have ranged from 0 to 629 micrograms per liter in the terrace alluvial aquifer. The seven municipal wells mostly west and south of Air Force Plant 4 are not along a flowpath for leakage of contaminants from the plant because ground-water flow in the Paluxy aquifer is toward the east-southeast. Furthermore, trichloroethylene was not detected in any of these wells in 1993 when all were sampled for water quality. The results of water-quality sampling at 10 domestic wells northwest of the Air Force Plant 4 during April 1993 and April 1995 indicated that neither trichloroethylene nor chromium had migrated off-site to these wells.

Using imaging spectroscopy to map acidic mine waste

USGS Publications Warehouse

Swayze, G.A.; Smith, K.S.; Clark, R.N.; Sutley, S.J.; Pearson, R.M.; Vance, J.S.; Hageman, P.L.; Briggs, P.H.; Meier, A.L.; Singleton, M.J.; Roth, S.

2000-01-01

The process of pyrite oxidation at the surface of mine waste may produce acidic water that is gradually neutralized as it drains away from the waste, depositing different Fe-bearing secondary minerals in roughly concentric zones that emanate from mine-waste piles. These Fe-bearing minerals are indicators of the geochemical conditions under which they form. Airborne and orbital imaging spectrometers can be used to map these mineral zones because each of these Fe-bearing secondary minerals is spectrally unique. In this way, imaging spectroscopy can be used to rapidly screen entire mining districts for potential sources of surface acid drainage and to detect acid producing minerals in mine waste or unmined rock outcrops. Spectral data from the AVIRIS instrument were used to evaluate mine waste at the California Gulch Superfund Site near Leadville, CO. Laboratory leach tests of surface samples show that leachate pH is most acidic and metals most mobile in samples from the inner jarosite zone and that leachate pH is near-neutral and metals least mobile in samples from the outer goethite zone.

Hydrologically Controlled Arsenic Release in Deltaic Wetlands and Coastal Riparian Zones

NASA Astrophysics Data System (ADS)

Stuckey, J.; LeMonte, J. J.; Yu, X.; Schaefer, M.; Kocar, B. D.; Benner, S. G.; Rinklebe, J.; Tappero, R.; Michael, H. A.; Fendorf, S. E.; Sparks, D. L.

2016-12-01

Wetland and riparian zone hydrology exerts critical controls on the biogeochemical cycling of metal contaminants including arsenic. The role of wetlands in driving geogenic arsenic release to groundwater has been debated in the deltas of South and Southeast Asia where the largest impacted human population resides. In addition, groundwater in coastal areas worldwide, such as those in South and Southeast Asia and the Mid-Atlantic of the U.S., is at risk to largely unexplored biogeochemical and hydrologic impacts of projected sea level rise. First, we present data from fresh-sediment incubations, in situ model sediment incubations and a controlled field experiment with manipulated wetland hydrology and organic carbon inputs in the minimally disturbed upper Mekong Delta. Here we show that arsenic release is limited to near-surface sediments of permanently saturated wetlands where both organic carbon and arsenic-bearing solids are sufficiently reactive for microbial oxidation of organic carbon and reduction of arsenic-bearing iron oxides. In contrast, within the deeper aquifer or seasonally saturated sediments, reductive dissolution of iron oxides is observed only when either more reactive exogenous forms of iron oxides or organic carbon are added, revealing a potential thermodynamic restriction to microbial metabolism. Second, in order to assess the potential impacts of sea level rise on arsenic release to groundwater, we determined the changes in arsenic speciation and partitioning in sediment collected from an anthropogenically contaminated coastal riparian zone under controlled Eh regimes in both seawater and freshwater systems. Here we show greater arsenic release under anoxic/suboxic conditions in the freshwater system than in the seawater system, potentially due to high salinity induced microbial inhibition. Collectively, our work shows that shifting hydrologic conditions in deltaic wetlands and tidally influenced zones impacts the extent of arsenic release to groundwater. Land and water management decisions that increase the duration of wetland inundation may promote arsenic release to groundwater.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone from Autonomous Gliders

NASA Astrophysics Data System (ADS)

Lee, Craig; Rainville, Luc; Perry, Mary Jane

2016-04-01

The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer (PSW) and Atlantic (AW) waters), and elevated surface wave energy that acts to deform and fracture sea ice. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, and how the balance of processes shift as a function of ice fraction and distance from open water, four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse as they progress through the MIZ and into open water. The isopynal layer between 1023 and 1024 kgm-3, just above the PSW, consistently thickens near the ice edge, likely due to mixing or energetic vertical exchange associated with strong lateral gradients in this region. This presentation will discuss the upper ocean variability, its relationship to sea ice extent, and evolution over the summer to the start of freeze up.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone from Autonomous Gliders

NASA Astrophysics Data System (ADS)

Lee, C.; Rainville, L.; Perry, M. J.

2016-02-01

The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer (PSW) and Atlantic (AW) waters), and elevated surface wave energy that acts to deform and fracture sea ice. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, and how the balance of processes shift as a function of ice fraction and distance from open water, four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse as they progress through the MIZ and into open water. The isopynal layer between 1023 and 1024 kg m-3, just above the PSW, consistently thickens near the ice edge, likely due to mixing or energetic vertical exchange associated with strong lateral gradients in this region. This presentation will discuss the upper ocean variability, its relationship to sea ice extent, and evolution over the summer to the start of freeze up.

Geophysical Logs, Aquifer Tests, and Water Levels in Wells in and Near the North Penn Area 7 Superfund Site, Upper Gwynedd Township, Montgomery County, Pennsylvania, 2002-2006

USGS Publications Warehouse

Senior, Lisa A.; Conger, Randall W.; Bird, Philip H.

2008-01-01

Ground water in the vicinity of several industrial facilities in Upper Gwynedd Township and Lansdale Borough, Montgomery County, Pa., is contaminated with several volatile organic compounds (VOCs). The 2-square-mile area was placed on the National Priorities List as the North Penn Area 7 Superfund Site by the U.S. Environmental Protection Agency (USEPA) in 1989. The U.S. Geological Survey (USGS) conducted geophysical logging, aquifer testing, water-level monitoring, and streamflow measurements in the vicinity of North Penn Area 7 from October 2002 through December 2006. This followed work that began in 2000 to assist the USEPA in developing an understanding of the hydrogeologic framework in the area as part of the USEPA Remedial Investigation. The study area is underlain by Triassic- and Jurassic-age sandstones, siltstones, and shales of the Lockatong Formation and the Brunswick Group. Regionally, these rocks strike northeast and dip to the northwest. The sequence of rocks form fractured-rock aquifers that act as a set of confined to semi-confined layered aquifers of differing permeabilities. The aquifers are recharged by precipitation and discharge to streams and wells. The Wissahickon Creek headwaters are less than 1 mile northeast of the study area. This stream flows southwest approximately parallel to strike and bisects North Penn Area 7. Ground water is pumped in the vicinity of North Penn Area 7 for industrial use and public supply. The USGS collected geophysical logs for 42 wells that ranged in depth from 40 to 477 ft. Aquifer-interval-isolation testing was done in 17 of the 42 wells, for a total of 122 zones tested. A multiple-well aquifer test was conducted by monitoring the response of 14 wells to pumping and shutdown of a 600-ft deep production well in November-December 2004. In addition, water levels were monitored continuously in four wells in the area from October 2002 through September 2006, and streamflow was measured quarterly at two sites on Wissahickon Creek from December 2002 through September 2005. Geophysical logging identified water-bearing zones associated with high-angle fractures and bedding-plane openings throughout the depth of the boreholes. Heatpulse-flowmeter measurements under non-pumping, ambient conditions in 16 wells greater than 200 ft in depth indicated that borehole flow, where detected, was only upward in 2 wells and only downward in 5 wells. In nine wells, both upward and downward flow were measured. Geologic structure and pumping in the area affect the spatial distribution of vertical gradients. Heatpulse-flowmeter measurements under pumping conditions were used to identify the most productive intervals in wells. Correlation of natural-gamma-ray logs indicated bedding in the area probably strikes about 45 to 65 degrees northeast and dips about 9 degrees northwest. Aquifer intervals isolated by inflatable packers in 17 wells were pumped to test productivity of water-bearing zones and to collect samples to determine chemical quality of water produced from the interval. Interval-isolation testing confirmed the vertical hydraulic gradients indicated by heatpulse-flowmeter measurements. The specific capacities of the 122 isolated intervals ranged over about three orders of magnitude, from 0.01 to 10.6 gallons per minute per foot, corresponding to calculated transmissivities of 1.2 to 2,290 feet squared per day. Intervals adjacent to isolated pumped intervals commonly showed little response to pumping of the isolated zone. The presence of vertical hydraulic gradients and lack of adjacent-interval response to pumping in isolated intervals indicate a limited degree of vertical hydraulic connection between the aquifer sections tested. Differences were apparent in inorganic water quality of water from isolated intervals, including pH, specific conductance, and dissolved oxygen. Concentrations of most VOC contaminants in most wells with predominantly upward vertical gradients were g

Trace fossils and sedimentology of a Late Cretaceous Progradational Barrier Island sequence: Bearpaw and Horseshoe Canyon Formations, Dorothy, Alberta

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saunders, T.D.; Pemberton, A.G.; Ranger, M.J.

A well-exposed example of a regressive barrier island succession crops out in the Alberta badlands along the Red Deer River Valley. In the most landward (northwestern) corner of the study area, only shallow-water and subaerial deposits are represented and are dominated by tidal inlet related facies. Seaward (southeast), water depth increases and the succession is typified by open-marine beach to offshore-related facies arranged in coarsening-upward progradational sequence. Detailed sedimentologic and ichnologic analyses of this sequence have allowed for its division into three distinct environmental zones (lower, middle, and upper). The lower zone comprises a laterally diverse assemblage of storm-influenced, lowermore » shoreface through offshore deposits. Outcrop in the northeast is dominated by thick beds of hummocky and/or swaley cross-stratified storm sand. In the southeast, storm events have only minor influence. This lower zone contains a wide diversity of well-preserved trace fossils whose distribution appears to have been influenced by gradients in wave energy, bottom stagnation, and the interplay of storm and fair-weather processes. The middle zone records deposition across an upper shoreface environment. Here, horizontal to low-angle bedding predominates, with interspersed sets of small- and large-scale cross-bedding increasing toward the top. A characteristic feature of the upper part of this zone is the lack of biogenic structures suggesting deposition in an exposed high-energy surf zone. The upper zone records intertidal to supratidal progradation of the shoreline complex. Planar-laminated sandstone forms a distinct foreshore interval above which rhizoliths and organic material become increasingly abundant, marking transition to the backshore. A significant feature of this zone is the occurrence of an intensely bioturbated interval toward the top of the foreshore.« less

MICROCHARACTERIZATION OF ARSENIC- AND SELENIUM-BEARING PYRITE IN UPPER FREEPORT COAL, INDIANA COUNTY, PENNSYLVANIA.

USGS Publications Warehouse

Minkin, J.A.; Finkelman, R.B.; Thompson, C.L.; Chao, E.C.T.; Ruppert, L.F.; Blank, H.; Cecil, C.B.

1984-01-01

Optical and scanning electron microscope as well as electron and proton microprobe techniques have been used in a detailed investigation of the modes of occurrence of arsenic and selenium in pyrite in Upper Freeport coal from the Homer City area, Indiana County, Pennsylvania. Polished blocks were prepared from columnar samples of the coal bed to represent particular zones continuously from top to bottom. Initial selection of zones to be studied was based on chemical analysis of bench-channel samples. Microprobe data indicate that the highest concentrations of arsenic (as great as 1. 5 wt. %) are apparently in solid solution in pyrite within a limited stratigraphic interval of the coal bed. Smaller amounts of arsenic and selenium (concentrations up to approximately 0. 1 and 0. 2 wt. % respectively) were detected at isolated points within pyrite grains in various strata of the coal bed.

Conventional and technical diving surveys reveal elevated biomass and differing fish community composition from shallow and upper mesophotic zones of a remote United States coral reef.

PubMed

Muñoz, Roldan C; Buckel, Christine A; Whitfield, Paula E; Viehman, Shay; Clark, Randy; Taylor, J Christopher; Degan, Brian P; Hickerson, Emma L

2017-01-01

The world's coral reefs appear to be in a global decline, yet most previous research on coral reefs has taken place at depths shallower than 30 m. Mesophotic coral ecosystem (depths deeper than ~30 m) studies have revealed extensive, productive habitats and rich communities. Despite recent advances, mesophotic coral ecosystems remain understudied due to challenges with sampling at deeper depths. The few previous studies of mesophotic coral ecosystems have shown variation across locations in depth-specific species composition and assemblage shifts, potentially a response to differences in habitat or light availability/water clarity. This study utilized scuba to examine fish and benthic communities from shallow and upper mesophotic (to 45 m) zones of Flower Garden Banks National Marine Sanctuary (FGBNMS, 28°0'N; 93°50'W) from 2010-2012. Dominant planktivores were ubiquitous in shallow and upper mesophotic habitats, and comparisons with previous shallow research suggest this community distribution has persisted for over 30 years. Planktivores were abundant in shallow low-relief habitats on the periphery of the coral reef, and some of these sites that contained habitat transitioning from high to low relief supported high biomass of benthic predators. These peripheral sites at FGBNMS may be important for the trophic transfer of oceanic energy to the benthic coral reef. Distinct differences between upper mesophotic and shallow communities were also observed. These included greater overall fish (as well as apex predator) biomass in the upper mesophotic, differences in apex predator community composition between depth zones, and greater percent cover of algae, rubble, sand, and sponges in the upper mesophotic. Greater fish biomass in the upper mesophotic and similar fish community composition between depth zones provide preliminary support that upper mesophotic habitats at FGBNMS have the capacity to serve as refugia for the shallow-water reefs. Diving surveys of the upper mesophotic and shallow-water coral reef have revealed valuable information concerning the reef fish community in the northern Gulf of Mexico, with implications for the conservation of apex predators, oceanic coral reefs, and the future management of FGBNMS.

Conventional and technical diving surveys reveal elevated biomass and differing fish community composition from shallow and upper mesophotic zones of a remote United States coral reef

PubMed Central

Buckel, Christine A.; Whitfield, Paula E.; Viehman, Shay; Clark, Randy; Taylor, J. Christopher; Degan, Brian P.; Hickerson, Emma L.

2017-01-01

The world’s coral reefs appear to be in a global decline, yet most previous research on coral reefs has taken place at depths shallower than 30 m. Mesophotic coral ecosystem (depths deeper than ~30 m) studies have revealed extensive, productive habitats and rich communities. Despite recent advances, mesophotic coral ecosystems remain understudied due to challenges with sampling at deeper depths. The few previous studies of mesophotic coral ecosystems have shown variation across locations in depth-specific species composition and assemblage shifts, potentially a response to differences in habitat or light availability/water clarity. This study utilized scuba to examine fish and benthic communities from shallow and upper mesophotic (to 45 m) zones of Flower Garden Banks National Marine Sanctuary (FGBNMS, 28°0ʹN; 93°50ʹW) from 2010–2012. Dominant planktivores were ubiquitous in shallow and upper mesophotic habitats, and comparisons with previous shallow research suggest this community distribution has persisted for over 30 years. Planktivores were abundant in shallow low-relief habitats on the periphery of the coral reef, and some of these sites that contained habitat transitioning from high to low relief supported high biomass of benthic predators. These peripheral sites at FGBNMS may be important for the trophic transfer of oceanic energy to the benthic coral reef. Distinct differences between upper mesophotic and shallow communities were also observed. These included greater overall fish (as well as apex predator) biomass in the upper mesophotic, differences in apex predator community composition between depth zones, and greater percent cover of algae, rubble, sand, and sponges in the upper mesophotic. Greater fish biomass in the upper mesophotic and similar fish community composition between depth zones provide preliminary support that upper mesophotic habitats at FGBNMS have the capacity to serve as refugia for the shallow-water reefs. Diving surveys of the upper mesophotic and shallow-water coral reef have revealed valuable information concerning the reef fish community in the northern Gulf of Mexico, with implications for the conservation of apex predators, oceanic coral reefs, and the future management of FGBNMS. PMID:29161314

Hydrology of Polk County, Florida

USGS Publications Warehouse

Spechler, Rick M.; Kroening, Sharon E.

2007-01-01

Local water managers usually rely on information produced at the State and regional scale to make water-resource management decisions. Current assessments of hydrologic and water-quality conditions in Polk County, Florida, commonly end at the boundaries of two water management districts (South Florida Water Management District and the Southwest Florida Water Management District), which makes it difficult for managers to determine conditions throughout the county. The last comprehensive water-resources assessment of Polk County was published almost 40 years ago. To address the need for current countywide information, the U.S. Geological Survey began a 3?-year study in 2002 to update information about hydrologic and water-quality conditions in Polk County and identify changes that have occurred. Ground-water use in Polk County has decreased substantially since 1965. In 1965, total ground-water withdrawals in the county were about 350 million gallons per day. In 2002, withdrawals totaled about 285 million gallons per day, of which nearly 95 percent was from the Floridan aquifer system. Water-conservation practices mainly related to the phosphate-mining industry as well as the decrease in the number of mines in operation in Polk County have reduced total water use by about 65 million gallons per day since 1965. Polk County is underlain by three principal hydrogeologic units. The uppermost water-bearing unit is the surficial aquifer system, which is unconfined and composed primarily of clastic deposits. The surficial aquifer system is underlain by the intermediate confining unit, which grades into the intermediate aquifer system and consists of up to two water-bearing zones composed of interbedded clastic and carbonate rocks. The lowermost hydrogeologic unit is the Floridan aquifer system. The Floridan aquifer system, a thick sequence of permeable limestone and dolostone, consists of the Upper Floridan aquifer, a middle semiconfining unit, a middle confining unit, and the Lower Floridan aquifer. The Upper Floridan aquifer provides most of the water required to meet demand in Polk County. Data from about 300 geophysical and geologic logs were used to construct hydrogeologic maps showing the tops and thicknesses of the aquifers and confining units within Polk County. Thickness of the surficial aquifer system ranges from several feet thick or less in the extreme northwestern part of the county and along parts of the Peace River south of Bartow to more than 200 feet along the southern part of the Lake Wales Ridge in eastern Polk County. Thickness of the intermediate aquifer system/intermediate confining unit is highly variable throughout the county because of past erosional processes and sinkhole formation. Thickness of the unit ranges from less than 25 feet in the extreme northwestern part of the county to more than 300 feet in southwestern Polk County. The altitude of the top of the Upper Floridan aquifer in the county ranges from about 50 feet above National Geodetic Vertical Datum of 1929 (NGVD 29) in the northwestern part to more than 250 feet below NGVD 29 in the southern part. Water levels in the Upper Floridan aquifer fluctuate seasonally, increasing during the wet season (June through September) and decreasing during the rest of the year. Water levels in the Upper Floridan aquifer also can change from year to year, depending on such factors as pumpage and climatic variations. In the southwestern part of the county, fluctuations in water use related to phosphate mining have had a major impact on ground-water levels. Hydrographs of selected wells in southwestern Polk County show a general decline in water levels that ended in the mid-1970s. This water-level decline coincides with an increase in water use associated with phosphate mining. A substantial increase in water levels that began in the mid-1970s coincides with a period of decreasing water use in the county. Despite reductions in water use since 1970, howev

Characterization of the Hydrocarbon Potential and Non-Potential Zones Using Wavelet-Based Fractal Analysis

NASA Astrophysics Data System (ADS)

Mukherjee, Bappa; Roy, P. N. S.

The identification of prospective and dry zone is of major importance from well log data. Truthfulness in the identification of potential zone is a very crucial issue in hydrocarbon exploration. In this line, the problem has received considerable attention and many conventional techniques have been proposed. The purpose of this study is to recognize the hydrocarbon and non-hydrocarbon bearing portion within a reservoir by using the non-conventional technique. The wavelet based fractal analysis (WBFA) has been applied on the wire-line log data in order to obtain the pre-defined hydrocarbon (HC) and non-hydrocarbon (NHC) zones by their self-affine signal nature is demonstrated in this paper. The feasibility of the proposed technique is tested with the help of most commonly used logs, like self-potential, gamma ray, resistivity and porosity log responses. These logs are obtained from the industry to make out several HC and NHC zones of all wells in the study region belonging to the upper Assam basin. The results obtained in this study for a particular log response, where in the case of HC bearing zones, it is found that they are mainly situated in a variety of sandstones lithology which leads to the higher Hurst exponent. Further, the NHC zones found to be analogous to lithology with higher shale content having lower Hurst exponent. The above proposed technique can overcome the chance of miss interpretation in conventional reservoir characterization.

Hydrogeologic framework and geologic structure of the Floridan aquifer system and intermediate confining unit in the Lake Okeechobee area, Florida

USGS Publications Warehouse

Reese, Ronald S.

2014-01-01

The successful implementation of aquifer storage and recovery (ASR) as a water-management tool requires detailed information on the hydrologic and hydraulic properties of the potential water storage zones. This report presents stratigraphic and hydrogeologic sections of the upper part of the Floridan aquifer system and the overlying confining unit or aquifer system in the Lake Okeechobee area, and contour maps of the upper contacts of the Ocala Limestone and the Arcadia Formation, which are represented in the sections. The sections and maps illustrate hydrogeologic factors such as confinement of potential storage zones, the distribution of permeability within the zones, and geologic features that may control the efficiency of injection, storage, and recovery of water, and thus may influence decisions on ASR activities in areas of interest to the Comprehensive Everglades Restoration Plan.

Water sensitivity of the seismic properties of upper-mantle olivine

NASA Astrophysics Data System (ADS)

Cline, Christopher; David, Emmanuel; Faul, Ulrich; Berry, Andrew; Jackson, Ian

2017-04-01

The wave speeds and attenuation of seismic waves in the upper mantle are expected to be strongly influenced by the defect chemistry of olivine grain interiors and the associated chemical complexity of grain-boundary regions. Changes in chemical environment (oxygen fugacity and/or water fugacity) can impose different defect chemistries, including the creation and retention of hydrous defects, and therefore can directly influence anelastic relaxation involving stress-induced migration of lattice defects and/or grain-boundary sliding. Here we report the first low-frequency experimental study of the seismic properties of olivine under water-undersaturated conditions. Three synthetic sol-gel derived olivine (Fo90) specimens were fabricated by hot-pressing in welded Pt capsules with various concentrations of hydroxyl, chemically bound as doubly protonated Si vacancies, charge balanced by substitution of Ti on a neighboring M-site (i.e., the Ti-clinohumite-like defect). Hydroxyl contents, determined following the subsequent mechanical testing within Pt sleeves, increased systematically with the amount of added Ti-dopant. Added Ti concentrations ranged between 176 and 802 atom ppm Ti/Si, resulting in concentrations of bound hydrogen in the three samples ranging between 330 and 1150 atom ppm H/Si. Each hot-pressed specimen was precision ground and then sleeved in Pt for mechanical testing in forced torsional oscillation under water-undersaturated conditions. Forced-oscillation tests were conducted at seismic periods of 1 - 1000 s and 200 MPa confining pressure during slow staged cooling from 1200 to 25°C. Each Ti-doped specimen showed mechanical behavior of the high-temperature background type involving monotonically increasing dissipation and decreasing shear modulus with increasing oscillation period and increasing temperature. Comparison of the mechanical data acquired in these water-undersaturated conditions with a similarly tested, but dry, Ti-bearing specimen (enclosed within an Ni-Fe sleeve under more reducing conditions) shows a marked contrast. The OH-bearing specimens exhibit much lower shear moduli (by as much as 80%) and higher levels of dissipation (by as much as 0.5 log units in Q-1), but also limited sensitivity of the seismic properties to the total water content among the hydrated specimens in the series. These results indicate that the higher oxygen and water fugacities prevailing within Pt-sleeved specimens result in lower shear moduli and higher dissipation under water-undersaturated conditions - presumably attributable to contrasting defect populations and/or grain boundary chemistries. Clarification of the relative roles of grain-boundary sliding and any additional intragranular relaxation under increased fH2O and fO2 thus offers the prospect of an improved understanding of the seismological signature of more oxidized/hydrous portions of the Earth's upper mantle, such as subduction zone environments.

Geohydrology of the proposed Waste Isolation Pilot Plant site, Los Medanos area, southeastern New Mexico

USGS Publications Warehouse

Mercer, Jerry W.

1983-01-01

Geohydrologic data have been collected in the Los Medanos area at the U.S. Department of Energy 's proposed Waste Isolation Pilot Plant (WIPP) site in southeastern New Mexico since 1975 as part of an intensive study evaluating the feasibility of storing defense-associated nuclear wastes within the bedded salt of the Salado Formation of Permian age. Drilling and hydrologic testing have identified three principal water-producing zones above the salt, including the Rustler-Salado Formational contact and the Culebra and Magenta Dolomite Members of the Permian Rustler Formation. Below the bedded salt there is another water-bearing zone, the channel sandstones of the Bell Canyon formation of the Permian Delaware Mountain Group. Most data collected from 33 hydrologic test holes indicate that the water-bearing zones are characterized by low transmissivities and contain slightly saline to briny water. Data collected from drill-stem tests in the Bell Canyon Formation indicate the channel sandstones have hydraulic conductivities ranging from 0.02 to 0.36 feet per day grade vertically and laterally into siltstones and shales of very low permeability. The Rustler Formation contains the principal water-producing zones identified at the WIPP site. The Rustler-Salado formational contact has the least transmissivity, ranging from 0.00003 to 0.003 feet squared per day. The Culebra Dolomite is the most productive unit at the WIPP site with transmissivities ranging from 0.001 to 73 feet squared per day; the greater values result from fracturing in the dolomite created by dissolution of underlying halite. Minute vertical permeabilities prevent movement of water between hydrologic units. (USGS)

Geohydrology and water quality in northern Portage County, Ohio, in relation to deep-well brine injection

USGS Publications Warehouse

Eberts, S.M.

1991-01-01

Geohydrology and water quality of the principal freshwater aquifers near oilfield and gasfield brine-injection wells in northern Portage County, Ohio, were evaluated. Since 1975, 13 wells in this part of the Country have been used to dispose of more than 4.5 million barrels of brine by injection into Silurian carbonate and sandstone rocks that generally are greater than 3,500 feet below land surface. More than 3,000 feet of interbedded shales, sandstones, carbonates, and evaporites separate the freshwater aquifers from these brine-injection zones. The shallowest brine-injection zone is greater than 2,200 feet below sea level. Native fluids in the injection zones have dissolved-solids concentrations greater than 125,000 milligrams per liter and are hydraulically isolated from the freshwater aquifers. No known faults or fracture systems are present in northern Portage County, although abandoned oil and gas wells could exist and serve as conduits for migration of injected brine. Pennsylvanian clastic units are freshwater bearing in northern Portage County, and two bedrock aquifers generally are recognized. The shallower bedrock aquifer (Connoquenessing Sandstone Member of the Pottsville Formation) principally consists of sandstone; this aquifer is separated from a deeper sandstone and conglomerate aquifer in the lower part of the Sharon Member (Pottsville Formation) by shale in the upper part of the Sharon Member that acts as a confining unit. The upper sandstone aquifer is the surficial aquifer where overlying glacial deposits are unsaturated in the uplands; glacial deposits comprise the surficial aquifer in buried valleys where the sandstone is absent. These two surficial aquifers are hydraulically connected and act as a single unit. The lower sandstone and conglomerate aquifer is the most areally extensive aquifer within the project area. From November 1987 through August 1988, ground-water levels remained at least 60 feet higher in the upper sandstone aquifer than in the lower sandstone and conglomerate aquifer at a topographically high recharge area. Water levels in the surficial aquifers and the lower sandstone and conglomerate aquifer were nearly the same along the Cuyahoga River. Ground water in the upper sandstone aquifer flows radially from topographically high recharge areas into the glacial deposits in the buried valleys. Much of the ground water in these surficial aquifers discharges into the Cuyahoga River. Most ground water in the lower sandstone and conglomerate aquifer flows toward discharge areas near the Cuyahoga River and Eagle Creek. In June 1988, the Cuyahoga River gained 15.8 cubic feet per second of water from the aquifers between the northern edge of Portage County and State Route 303. Ground water may have discharged into the upstream end of Lake Rockwell but did not discharge into the downstream end of the Lake during most of the period from October 1987 through September 1988. Measurements of the specific conductance of ground water sampled from areas near the 13 brine-injection wells and along the Cuyahoga River indicate no widespread ground-water contamination related to brine injection. Chemical analysis of water from 25 wells indicates that most ground waters are a calcium bicarbonate type. Water analyses show that four wells sampled contain water with chloride concentrations greater than 250 milligrams per liter. Sodium concentrations in water from these four wells ranged from 67 to 190 milligrams per liter. A mixing diagram constructed from bromide and chloride data was used to distinguish between the sources of elevated chloride concentrations in these four wells. Waters from two of the wells have been mixed with oilfield and gasfield brine, and waters from the other two wells have been mixed with a salt-solution brine such as that derived from diluted highway-deicing salts.

Surficial aquifer system in eastern Lee County, Florida

USGS Publications Warehouse

Boggess, D.H.; Watkins, F.A.

1986-01-01

The surficial aquifer system in eastern Lee County consists of an upper water bearing unit, which is generally unconfined, and a lower water bearing unit, which is confined and is the major source tapped by most wells. The top of the lower unit, which is of primary interest in this report, ranges in depth from 40 to 60 ft below land surface in the east-central part of the county to more than 120 ft in the southern part. In the extreme southern part of the county, a middle water bearing unit also contains water under artesian pressure. Recharge to the lower unit occurs primarily by leakage from the overlying saturated section through the confining beds. Water levels in the lower unit fluctuate similarly to those in the upper (unconfined) unit. Groundwater in the lower unit moves from areas of highest water level in the south part of Lehigh acres, northward toward the Caloosahatchee River, and toward the coast. The lower unit contains freshwater throughout much of its extent and is the source of public water supply at Lehigh Acres and Green Meadows where an average of about 3 mil gal/day was withdrawn in 1980. In several areas, the concentrations of chlorides and dissolved solids exceed drinking water standards. Yields of wells that tap the lower unit range from 10 to 1,100 gal/min. Transmissivities ranging from about 17,700 to 7,750 sq ft/day were determined for different areas of the unit. Storage coefficients range from 0.0001 to 0.0003. (Author 's abstract)

Geology of the Midnite uranium mine, Stevens County, Washington; a preliminary report

USGS Publications Warehouse

Nash, J. Thomas; Lehrman, Norman J.

1975-01-01

The Midnite mine is one of only two mines in the United States currently producing uranium from discordant deposits in crystalline host rocks. Ore bodies are in metamorphosed steeply dipping Precambrian pelitic and calcareous rocks of a roof pendant adjacent to a Cretaceous(?) porphyritic quartz monzonite pluton. Production during 14 years, of operation has been about 8 million pounds of U3O8 from oxidized and reduced ores averaging 0.23 percent U3O8. Uranium deposits are generally tabular in form and dimensions range up to 380 m long, 210 m wide, and 50 m thick. Deposits are bounded on at least one side by unmineralized intrusive ribs of granitic rock, and thickest mineralized zones invariably occur at depressions in the intrusive contact. Upper limits of some deposits are nearly horizontal, and upper elevations of adjacent mineralized zones separated by ribs of granite are similar. Near surface ore is predominantly autunite, but ore at depth consists of pitchblende and coffinite with abundant pyrite and marcasite. Uranium minerals occur as .disseminations along foliation, replacements, and stockwork fracture-fillings. No stratigraphic controls on ore deposition are recognized. Rather, mineralized zones cut across lithologic boundaries if permeability is adequate. Most ore is in muscovite schist and mica phyllite, but important deposits occur in calc-silicate hornfels. Amphibolite sills and mid-Tertiary dacite dikes locally, carry ore where intensely fractured. High content of iron and sulfur, contained chiefly in FeS2, appear to be an important feature of favorable host rocks. Geometry of deposits, structural, and geochemical features suggest that uranium minerals were deposited over a span of time from late Cretaceous to late Tertiary. Ore occurs in but is not offset by a shear zone that displaces mid-Tertiary rocks.. Economic zones of uranium are interpreted to have been secondarily enriched in late Tertiary time by downward and lateral migration of uranium into permeable zones where deposition was influenced by ground water controls and minerals that could reduce or neutralize uranium-bearing solutions.

Widespread gas hydrate instability on the upper U.S. Beaufort margin

NASA Astrophysics Data System (ADS)

Phrampus, Benjamin J.; Hornbach, Matthew J.; Ruppel, Carolyn D.; Hart, Patrick E.

2014-12-01

The most climate-sensitive methane hydrate deposits occur on upper continental slopes at depths close to the minimum pressure and maximum temperature for gas hydrate stability. At these water depths, small perturbations in intermediate ocean water temperatures can lead to gas hydrate dissociation. The Arctic Ocean has experienced more dramatic warming than lower latitudes, but observational data have not been used to study the interplay between upper slope gas hydrates and warming ocean waters. Here we use (a) legacy seismic data that constrain upper slope gas hydrate distributions on the U.S. Beaufort Sea margin, (b) Alaskan North Slope borehole data and offshore thermal gradients determined from gas hydrate stability zone thickness to infer regional heat flow, and (c) 1088 direct measurements to characterize multidecadal intermediate ocean warming in the U.S. Beaufort Sea. Combining these data with a three-dimensional thermal model shows that the observed gas hydrate stability zone is too deep by 100 to 250 m. The disparity can be partially attributed to several processes, but the most important is the reequilibration (thinning) of gas hydrates in response to significant (~0.5°C at 2σ certainty) warming of intermediate ocean temperatures over 39 years in a depth range that brackets the upper slope extent of the gas hydrate stability zone. Even in the absence of additional ocean warming, 0.44 to 2.2 Gt of methane could be released from reequilibrating gas hydrates into the sediments underlying an area of ~5-7.5 × 103 km2 on the U.S. Beaufort Sea upper slope during the next century.

Airborne Remote Sensing of Trafficability in the Coastal Zone

DTIC Science & Technology

2009-01-01

validation instruments: Analytical Spectral Devices (ASD) full-range spectrometer; light weight deflectometer ( LWD ), which measures dynamic deflection...liquid water absorption features. The corresponding bearing strength measured by the LWD was high at the shoreline site and low at the backdune site...REVIEW REMOTE SENSING FIGURE 7 Correlation of in situ grain size, moisture, and bearing strength measurements. Scatterplot of percent moisture vs LWD

Two-stage fluid flow and element transfers in shear zones during collision burial-exhumation cycle: Insights from the Mont Blanc Crystalline Massif (Western Alps)

NASA Astrophysics Data System (ADS)

Rolland, Y.; Rossi, M.

2016-11-01

The Mont-Blanc Massif was intensely deformed during the Alpine orogenesis: in a first stage of prograde underthrusting at c. 30 Ma and in a second stage of uplift and exhumation at 22-11 Ma. Mid-crustal shear zones of 1 mm-50 m size, neighbouring episyenites (quartz-dissolved altered granite) and alpine veins, have localised intense fluid flow, which produced substantial changes in mineralogy and whole-rock geochemistry. Four main metamorphic zones are oriented parallel to the strike of the massif: (i) epidote, (ii) chlorite, (iii) actinolite-muscovite ± biotite and (iv) muscovite ± biotite. In addition, phlogopite-bearing shear zones occur in the chlorite zone, and calcite-bearing shear zones are locally found in the muscovite zone. The initial chemical composition of the granitic protolith is relatively constant at massif scale, which allows investigating compositional changes related to shear zone activity, and subsequent volume change and elements mobility. The variations of whole-rock composition and mineral chemistry in shear zones reflect variations in fluid/rock ratios and fluid's chemistry, which have produced specific mineral reactions. Estimated time-integrated fluid fluxes are of the order of 106 m3/m2. The mineral assemblages that crystallised upon these fluid-P-T conditions are responsible for specific major and trace element enrichments. The XFe (Fe/Fe + Mg) pattern of shear zone phyllosilicates and the δ13C pattern of vein calcite both show a bell-type pattern across the massif with high values on the massif rims and low values in the centre of the massif. These low XFe and δ13C values are explained by down temperature up-flow of a Fe-Mg-CO2-rich and silica-depleted fluid during stage 1, while the massif was underthrusting. These produced phlogopite, chlorite and actinolite precipitation and quartz hydrolysis, resulting in strong volume losses. In contrast, during stage 2 (uplift), substantial volume gains occurred on the massif rims due to the precipitation of quartz, epidote and muscovite from a local fluid hosted in the Helvetic cover. These two fluids advocate for the presence of an upper-crustal scaled fluid convection cell, with up-going fluids through the lower crust and likely down-going fluids in the 15 km upper crust.

Groundwater Protection Program Calendar Year 1998 Groundwater Monitoring Report, U.S. Department of Energy Y-12 Plant, Oak Ridge, Tennessee

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1999-03-01

This annual monitoring report contains groundwater and surface water monitoring data obtained during calendar year (CY) 1998 by the Lockheed Martin Energy Systems, Inc. Y-12 Plant Groundwater Protection Program (GWPP) at the U.S. Department of Energy (DOE) Oak Ridge Y-12 Plant, Groundwater and surface water monitoring during CY 1998 was performed in three hydrogeologic regimes at the Y-12 Plant: the Bear Creek Hydrogeologic Regime (Bear Creek Regime), the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime), and the Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime). The Bear Creek and East Fork regimes are located in Bear Creek Valleymore » (BCV), and the Chestnut Ridge Regime which is located south of the Y-12 Plant.« less

Lateral traction of laminar flow between sliding pair with heterogeneous slip/no-slip surface

NASA Astrophysics Data System (ADS)

Wu, Zhenpeng; Zeng, Liangcai; Chen, Xiaolan; Chen, Keying; Ding, Xianzhong

2017-11-01

The problem of shaft axial motion which significantly affects the lubrication performance has been a common phenomenon in journal bearing systems. The existing work involved in the solution of shaft axial motion is also very rare. In this study, we choose to examine the flow between sliding pair in which regard we present a unique heterogeneous surface consisting of a slip zone and a no-slip zone. The results reveal the following points: 1) By appropriately arranging the slip zone to change the angle between the borderline and the moving direction of the upper plate, it is possible to control the direction of the lateral traction in which the liquid film acts on the upper plate. 2) Exponent of the power function of the borderline and aspect ratio of the computational domain are large or small are not conducive to increasing the effect of lateral traction. For the object of this study, the final results of the optimization are shown that the lateral traction can account for 20% of the resistance.

Shallow groundwater investigation using time-domain electromagnetic (TEM) method at Itay El-Baroud, Nile Delta, Egypt

NASA Astrophysics Data System (ADS)

Shaaban, H.; El-Qady, G.; Al-Sayed, E.; Ghazala, H.; Taha, A. I.

2016-12-01

The Nile Delta is one of the oldest known ancient delta, largest and most important depositional complex in the Mediterranean sedimentary basin. Furthermore, it is a unique site in Egypt that is suitable for accumulation and preservation of the Quaternary sediments. In this work we applied time-domain electromagnetic (TEM) method to investigate the Quaternary sediments sequence as well as detecting the groundwater aquifer in the area of study. A suite of 232 TEM sounding at 43 stations were carried out using a ;SIROTEM MK-3; time-domain electromagnetic system. A simple coincident loop configuration, in which the same loop transmits and receives signals, was employed with loop side length of 25 m. The 1-D modeling technique was applied to estimate the depth and the apparent resistivity of the interpreted geoelectrical data. Based on the interpretation of the acquired geophysical data, four geoelectric cross-sections were constructed. These sections show that the Upper Quaternary sequence consists of three geoelectric layers. The Holocene Nile mud is separated into two layers: the agricultural root zone (Layer 1) and thick water saturated mud (Layer 2). The Upper Pleistocene sandy aquifer (Layer 3) is very complicated non-linear boundary. This aquifer is the most important unit since it is considered as the main water bearing unit in the study area.

Petrography, geochemistry, and depositional setting of the San Pedro and Santo Tomas coal zones: Anomalous algae-rich coals in the middle part of the Claiborne Group (Eocene) of Webb County, Texas

USGS Publications Warehouse

Warwick, Peter D.; Hook, Robert W.

1995-01-01

Two coal zones, the San Pedro and the overlying Santo Tomas, are present for nearly 35 km in outcrop, surface and underground mines, and shallow drill holes along the strike of the middle part of the Claiborne Group (Eocene) in Webb County, Texas. A sandstone-dominated interval of 25 to 35 m separates the two coal zones, which range up to 3 m in thickness. Each coal zone contains carbonaceous shales, thin (<0.75 m) impure coal beds, and thin (<0.85 m) but commercially significant nonbanded coal beds. The nonbanded coals are different from other Tertiary coals of the Gulf of Mexico Coastal Plain: unlike lignites that are typical of the older Wilcox Group (Paleocene-Eocene) and younger Jackson Group (Eocene), nonbanded coals of the Claiborne Group have high vitrinite-reflectance values (0.53 Rmax) and high calorific yields (average 6670 kcal/kg or 12,000 Btu, dry basis). The coals are weakly agglomerating (free-swelling index is 1.5–2.0) and have an apparent rank of high-volatile bituminous.The coal-bearing portion of the middle Claiborne Group in the Rio Grande area represents a fining-upward transition from sandstone-dominated, marine-influenced, lower delta plain depositional environments to more inland, mudstone-rich, predominantly freshwater deltaic settings. Discontinuities within the San Pedro coal zone are attributed mainly to the influence of contemporaneous deposition of distributary mouth-bar sand bodies. The less variable nature of the Santo Tomas coal zone reflects its origin in the upper part of an interlobe basin that received only minor clastic influx.Petrographic attributes of the nonbanded coals indicate that they formed subaqueously in fresh to possibly brackish waters. A highly degraded groundmass composed of eugelinite is the main petrographic component (approximately 71%, mineral-matter-free basis). An enriched liptinite fraction (approximately 23%) probably accounts for unusually high calorific values. There is negligible inertinite. Petrographic study of polished blocks indicates that approximately 10 percent of the nonbanded coal from both coal zones is composed of green algae fructifications, which also occur in clastic rocks of the coal-bearing interval. Such algal material cannot be identified or quantified by conventional coal petrographic techniques that utilize particle pellets or by palynological analyses that include acid preparation.

The Utilization of the Microflora Indigenous to and present in Oil-Bearing Formations to Selectively Plug the More Porous Zones Thereby Increasing Oil Recovery During Waterflooding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alex A. Vadie; Lewis R. Brown

1998-04-20

The use of indigenous microbes as a method of profile control in waterfloods is investigated. It is expected that as the microbial population is induced to increase the expanded biomass will selectively block the more permeable zones of the reservoir thereby forcing injection water to flow through the less permeable zones which will result in improved sweep efficiency.

Anaerobic methane oxidation in low-organic content methane seep sediments

USGS Publications Warehouse

Pohlman, John W.; Riedel, Michael; Bauer, James E.; Canuel, Elizabeth A.; Paull, Charles K.; Lapham, Laura; Grabowski, Kenneth S.; Coffin, Richard B.; Spence, George D.

2013-01-01

Sulfate-dependent anaerobic oxidation of methane (AOM) is the key sedimentary microbial process limiting methane emissions from marine sediments and methane seeps. In this study, we investigate how the presence of low-organic content sediment influences the capacity and efficiency of AOM at Bullseye vent, a gas hydrate-bearing cold seep offshore of Vancouver Island, Canada. The upper 8 m of sediment contains 14C. A fossil origin for the DIC precludes remineralization of non-fossil OM present within the sulfate zone as a significant contributor to pore water DIC, suggesting that nearly all sulfate is available for anaerobic oxidation of fossil seep methane. Methane flux from the SMT to the sediment water interface in a diffusion-dominated flux region of Bullseye vent was, on average, 96% less than at an OM-rich seep in the Gulf of Mexico with a similar methane flux regime. Evidence for enhanced methane oxidation capacity within OM-poor sediments has implications for assessing how climate-sensitive reservoirs of sedimentary methane (e.g., gas hydrate) will respond to ocean warming, particularly along glacially-influenced mid and high latitude continental margins.

Hydrogeology and simulated effects of ground-water withdrawals from the Floridan aquifer system in Lake County and in the Ocala National Forest and vicinity, north-central Florida

USGS Publications Warehouse

Knowles, Leel; O'Reilly, Andrew M.; Adamski, James C.

2002-01-01

The hydrogeology of Lake County and the Ocala National Forest in north-central Florida was evaluated (1995-2000), and a ground-water flow model was developed and calibrated to simulate the effects of both present day and future ground-water withdrawals in these areas and the surrounding vicinity. A predictive model simulation was performed to determine the effects of projected 2020 ground-water withdrawals on the water levels and flows in the surficial and Floridan aquifer systems. The principal water-bearing units in Lake County and the Ocala National Forest are the surficial and Floridan aquifer systems. The two aquifer systems generally are separated by the intermediate confining unit, which contains beds of lower permeability sediments that confine the water in the Florida aquifer system. The Floridan aquifer system has two major water-bearing zones (the Upper Floridan aquifer and the Lower Floridan aquifer), which generally are separated by one or two less-permeable confining units. The Floridan aquifer system is the major source of ground water in the study area. In 1998, ground-water withdrawals totaled about 115 million gallons per day in Lake County and 5.7 million gallons per day in the Ocala National Forest. Of the total ground water pumped in Lake County in 1998, nearly 50 percent was used for agricultural purposes, more than 40 percent for municipal, domestic, and recreation supplies, and less than 10 percent for commercial and industrial purposes. Fluctuations of lake stages, surficial and Floridan aquifer system water levels, and Upper Floridan aquifer springflows in the study area are highly related to cycles and distribution of rainfall. Long-term hydrographs for 9 lakes, 8 surficial aquifer system and Upper Floridan aquifer wells, and 23 Upper Floridan aquifer springs show the most significant increases in water levels and springflows following consecutive years with above-average rainfall, and significant decreases following consecutive years with below-average rainfall. Long-term (1940-2000) hydrographs of lake and ground-water levels and springflow show a slight downward trend; however, after the early 1960's, this downward trend generally is more pronounced, which corresponds with accumulating rainfall deficits and increased development. The U.S. Geological Survey three-dimensional ground-water flow model MODFLOW-2000 was used to simulate ground-water flow in the surficial and Floridan aquifer systems in Lake County, the Ocala National Forest, and adjacent areas. A steady-state calibration to average 1998 conditions was facilitated by using the inverse modeling capabilities of MODFLOW-2000. Values of hydrologic properties from the calibrated model were in reasonably close agreement with independently estimated values and results from previous modeling studies. The calibrated model generally produced simulated water levels and flows in reasonably close agreement with measured values and was used to simulate the hydrologic effects of projected 2020 conditions. Ground-water withdrawals in the model area have been projected to increase from 470 million gallons per day in 1998 to 704 million gallons per day in 2020. Significant drawdowns were simulated in Lake County from average 1998 to projected 2020 conditions: the average and maximum drawdowns, respectively, were 0.5 and 5.7 feet in the surficial aquifer system, 1.1 and 7.6 feet in the Upper Floridan aquifer, and 1.4 and 4.3 feet in the Lower Floridan aquifer. The largest drawdowns in Lake County were simulated in the southeastern corner of the County and in the vicinities of Clermont and Mount Dora. Closed-basin lakes and wetlands are more likely to be affected by future pumping in these large drawdown areas, as opposed to other areas of Lake County. However, within the Ocala National Forest, drawdowns were relatively small: the average and maximum drawdowns, respectively, were 0.1 and 1.0 feet in the surficial aquifer system, 0.2 and

The habitable zone and extreme planetary orbits.

PubMed

Kane, Stephen R; Gelino, Dawn M

2012-10-01

The habitable zone for a given star describes the range of circumstellar distances from the star within which a planet could have liquid water on its surface, which depends upon the stellar properties. Here we describe the development of the habitable zone concept, its application to our own solar system, and its subsequent application to exoplanetary systems. We further apply this to planets in extreme eccentric orbits and show how they may still retain life-bearing properties depending upon the percentage of the total orbit which is spent within the habitable zone. Key Words: Extrasolar planets-Habitable zone-Astrobiology.

Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, Martin and St. Lucie Counties, Florida

USGS Publications Warehouse

Reese, Ronald S.

2004-01-01

The Floridan aquifer system is considered to be a valuable source for agricultural and municipal water supply in Martin and St. Lucie Counties, despite its brackish water. Increased withdrawals, however, could increase salinity and threaten the quality of withdrawn water. The Floridan aquifer system consists of limestone, dolomitic limestone, and dolomite and is divided into three hydrogeologic units: the Upper Floridan aquifer, a middle confining unit, and the Lower Floridan aquifer. An informal geologic unit at the top of the Upper Floridan aquifer, referred to as the basal Hawthorn/Suwannee unit, is bound above by a marker unit in the Hawthorn Group and at its base by the Ocala Limestone; a map of this unit shows an area where substantial eastward thickening begins near the coast. This change in thickness is used to divide the study area into inland and coastal areas. In the Upper Floridan aquifer, an area of elevated chloride concentration greater than 1,000 milligrams per liter and water temperature greater than 28 degrees Celsius exists in the inland area and trends northwest through north-central Martin County and western St. Lucie County. A structural feature coincides with this area of greater salinity and water temperature; this feature is marked by a previously mapped northwest-trending basement fault and, based on detailed mapping in this study of the structure at the top of the basal Hawthorn/Suwannee unit, an apparent southeast-trending trough. Higher hydraulic head also has been mapped in this northwest-trending area. Another area of high chloride concentration in the Upper Floridan aquifer occurs in the southern part of the coastal area (in eastern Martin County and northeastern Palm Beach County); chloride concentration in this area is more than 2,000 milligrams per liter and is as great as 8,000 milligrams per liter. A dissolved-solids concentration of less than 10,000 milligrams per liter defines the brackish-water zone in the Floridan aquifer system; the top and base of this zone are present at the top of the aquifer system and within the Lower Floridan aquifer, respectively. The base of the brackish-water zone, which can approximate a brackish-water/saltwater interface, was determined in 13 wells, mostly using resistivity geophysical logs. The depth to the saltwater interface was calculated using the Ghyben-Herzberg approximation and estimated predevelopment hydraulic heads in the Upper Floridan aquifer. In five of six inland area wells, the depth to the base of the brackish-water zone was substantially shallower than the estimated predevelopment interface (260 feet or greater), whereas in five of seven coastal area wells, the difference was not large (less than about 140 feet). Confining units in the inland area, such as dense dolomite, may prevent an interface from forming at its equilibrium position. Because of head decline, the calculated interface using recent (May 2001) water levels is as much as 640 ft above the base of the brackish water zone (in the northern part of the coastal area). Isotopic data collected during this study, including deuterium and oxygen-18 (18O/16O), the ratio of strontium-87 to strontium-86, and carbon-13 (13C/12C) and carbon-14, provide evidence for differences in the Floridan aquifer system ground-water geochemistry and its evolution between inland and coastal areas. Ground water from the inland area tends to be older than water from the coastal area, particularly where inland area water temperature is elevated. Isotopic data together with an anomalous vertical distribution of salinity in the coastal area indicate that the coastal area was invaded with seawater in relatively recent geologic time, and this water has not been completely flushed out by the modern-day flow system. Upward leakage from the Lower to Upper Floridan aquifer of high salinity water occurs through structural deformities, such as faults or fracture zones or associated dissolution features

Environmental Assessment: For Joint Biological Point Detection System (JBPDS) at Multiple Test Ranges, Eglin Air Force Base, Florida

DTIC Science & Technology

2003-06-01

bed. This clay layer restricts the downward migration of pollutants and restricts saline water from Choctawhatchee Bay and the Gulf of Mexico from...Because it is saline , the Lower Limestone unit is not used as a water source (U.S. Air Force, 1995). Groundwater storage and movement in the Upper... purslane , among others. Inland from the produne zone is the “scrub” zone. Vegetation found in this zone is usually stunted and wind/salt sprayed

Soil water dynamics during precipitation in genetic horizons of Retisol

NASA Astrophysics Data System (ADS)

Zaleski, Tomasz; Klimek, Mariusz; Kajdas, Bartłomiej

2017-04-01

Retisols derived from silty deposits dominate in the soil cover of the Carpathian Foothills. The hydrophysical properties of these are determined by the grain-size distribution of the parent material and the soil's "primary" properties shaped in the deposition process. The other contributing factors are the soil-forming processes, such as lessivage (leaching of clay particles), and the morphogenetic processes that presently shape the relief. These factors are responsible for the "secondary" differentiation of hydrophysical properties across the soil profile. Both the primary and secondary hydrophysical properties of soils (the rates of water retention, filtration and infiltration, and the moisture distribution over the soil profile) determine their ability to take in rainfall, the amount of rainwater taken in, and the ways of its redistribution. The aims of the study, carried out during 2015, were to investigate the dynamics of soil moisture in genetic horizons of Retisol derived from silty deposits and to recognize how fast and how deep water from precipitation gets into soil horizons. Data of soil moisture were measured using 5TM moisture and temperature sensor and collected by logger Em50 (Decagon Devices USA). Data were captured every 10 minutes from 6 sensors at depths: - 10 cm, 20 cm, 40 cm, 60 cm and 80 cm. Precipitation data come from meteorological station situated 50 m away from the soil profile. Two zones differing in the type of water regime were distinguished in Retisol: an upper zone comprising humic and eluvial horizons, and a lower zone consisting of illuvial and parent material horizons. The upper zone shows smaller retention of water available for plants, and relatively wide fluctuations in moisture content, compared to the lower zone. The lower zone has stable moisture content during the vegetation season, with values around the water field capacity. Large changes in soil moisture were observed while rainfall. These changes depend on the volume of the precipitation and soil moisture before the precipitation. The following changes of moisture in the soil profile during precipitation were distinguished: if soil moisture in upper zone horizons oscillates around field capacity (higher than 0.30 m3ṡm-3) there is an evident increase in soil moisture also in the lower zone horizons. If soil moisture in the upper zone horizons is much lower than the field capacity (less than 0.20 m3ṡm-3), the soil moisture in the lower zone has very little fluctuations. The range of wetting front in the soil profile depends on the volume of the precipitation and soil moisture. The heavier precipitation, the wetting front in soil profile reaches deeper horizons. The wetter the soil is, the faster soil moisture in the deeper genetic horizons increase. This Research was financed by the Ministry of Science and Higher Education of the Republic of Poland, DS No. 3138/KGiOG/2016.

Microwave remote sensing of soil water content

NASA Technical Reports Server (NTRS)

Cihlar, J.; Ulaby, F. T.

1975-01-01

Microwave remote sensing of soils to determine water content was considered. A layered water balance model was developed for determining soil water content in the upper zone (top 30 cm), while soil moisture at greater depths and near the surface during the diurnal cycle was studied using experimental measurements. Soil temperature was investigated by means of a simulation model. Based on both models, moisture and temperature profiles of a hypothetical soil were generated and used to compute microwave soil parameters for a clear summer day. The results suggest that, (1) soil moisture in the upper zone can be predicted on a daily basis for 1 cm depth increments, (2) soil temperature presents no problem if surface temperature can be measured with infrared radiometers, and (3) the microwave response of a bare soil is determined primarily by the moisture at and near the surface. An algorithm is proposed for monitoring large areas which combines the water balance and microwave methods.

The hydrogeology of Kilauea volcano

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ingebritsen, S.E.; Scholl, M.A.

1993-08-01

The hydrogeology of Kilauea volcano and adjacent areas has been studied since the turn of this century. However, most studies to date have focused on the relatively shallow, low-salinity parts of the ground-water system, and the deeper hydrothermal system remains poorly understood. The rift zones of adjacent Mauna Loa volcano bound the regional ground-water flow system that includes Kilauea, and the area bounded by the rift zones of Kilauea and the ocean may comprise a partly isolated subsystem. Rates of ground-water recharge vary greatly over the area, and discharge is difficult to measure, because streams are ephemeral and most ground-watermore » discharges diffusely at or below sea level. Hydrothermal systems exist at depth in Kilauea's east and southwest rift zone, as evidenced by thermal springs at the coast and wells in the lower east-rift zone. Available data suggest that dike-impounded, heated ground water occurs at relatively high elevations in the upper east- and southwest-rift zones of Kilauea, and that permeability at depth in the rift zones. Available data suggest that dike-impounded, heated ground water occurs at relatively high elevations in the upper east- and southwest-rift zones of Kilauea, and that permeability at depth in the rift zones (probably [le]10[sup [minus]15] m[sup 2]) is much lower than that of unaltered basalt flows closer to the surface ([ge]10[sup [minus]10] m[sup 2]). Substantial variations in permeability and the presence of magmatic heat sources influence that structure of the fresh water-salt water interface, so the Ghyben-Herzberg model will often fail to predict its position. Numerical modeling studies have considered only subsets of the hydrothermal system, because no existing computer code solves the coupled fluid-flow, heat- and solute-transport problem over the temperature and salinity range encountered at Kilauea. 73 refs., 7 figs., 2 tabs.« less

Delineating Potential Karst Water-Bearing Structures based on Resistivity Anomalies and Microtremor Analyses-A Case Study in Yunnan Province, China

NASA Astrophysics Data System (ADS)

Gan, F.; Su, C.; Liu, W.; Zhao, W.

2016-12-01

Heterogeneity, anisotropy and rugged landforms become challenges for geophysicists to locate drilling site by water-bearing structure profiling in Karst region. If only one geophysical method is used to achieve this objective, low resistivity anomalies deduced to be water-rich zones could actually be zones rich in marl and shale. In this study, integrated geophysical methods were used to locate a favorable drilling position for the provision of karst water to Juede village, which had been experiencing severe water shortages over a prolonged period. According to site conditions and hydrogeological data, appropriate geophysical profiles were conducted, approximately perpendicular to the direction of groundwater flow. In general, significant changes in resistivity occur between water-filled caves/ fractures and competent rocks. Thus, electrical and electromagnetic methods have been widely applied to search for karst groundwater indirectly. First, electrical resistivity tomography was carried out to discern shallow resistivity distributions within the profile where the low resistivity anomalies were of most interest. Second, one short profile of audio-frequency magnetotelluric survey was used to ascertain the vertical and horizontal extent of these low resistivity anomalies. Third, the microtremor H/V spectral ratio method was applied to identify potential water-bearing structures from low resistivity anomalies and to differentiate these from the interference of marl and shale with low resistivity. Finally, anomalous depths were estimated by interpreting Schlumberger sounding data to determine an optimal drilling site. The study shows that karst hydrogeology and geophysical methods can be effectively integrated for the purposes of karst groundwater exploration.

An Updated Model for the Anomalous Resistivity of LNAPL Plumes in Sandy Environments

NASA Astrophysics Data System (ADS)

Sauck, W. A.; Atekwana, E. A.; Werkema, D. D.

2006-05-01

Anomalously low resistivities have been observed at some sites contaminated by light non-aqueous phase liquid (LNAPL) since. The model that has been used to explain this phenomenon was published in 2000. This working hypothesis invokes both physical mixing and bacterial action to explain the low resistivities near the base of the vadose zone and the upper part of the aquifer. The hydrocarbon-degrading bacteria (of which there are numerous species found in soils) produce organic acids and carbonic acids. The acidic pore waters dissolve readily soluble ions from the native soil grains and grain coatings, to produce a leachate high in total dissolved solids. The free product LNAPL is initially a wetting phase, although not generally more than 50% extent, and seasonal water table fluctuations mix the hydrocarbons vertically through the upper water saturated zone and transition zone. This update introduces several new aspects of the conductive model. The first is that, in addition to the acids being produced by the oil-degrading bacteria, they also produce surfactants. Surfactants act similarly to detergents in detaching the oil phase from the solid substrate, and forming an emulsion of oil droplets within the water. This has helped to explain how continuous, high-TDS capillary paths can develop and pass vertically through what appears to be a substantial free product layer, thus providing easy passage for electrical current during electrical resistivity measurements. Further, it has also been shown that the addition of organic acids and biosurfactants to pore fluids can directly contribute to the conductivity of the pore fluids. A second development is that large-diameter column experiments were conducted for nearly two years (8 columns for 4 experiments). The columns had a vertical row of eletrodes for resistivity measurements, ports for extracting water samples with a syringe, and sample tubes for extracting soil samples. Water samples were used for chemical analysis and the soil samples for bacterial assays. Those columns to which diesel oil had been added (4) clearly showed the resistivity to decrease, the TDS of water samples to increase, and a radical change in bacterial populations favoring the oil degraders to occur. In the laboratory, most of the significant changes occurred in the time span of 4 to 6 months. The third development that may have a bearing on anomalous conductivity was the recent discovery that certain bacteria, (e.g., Geobacter sulfurreducens) have hairlike structures called pili that are excellent electrical conductors. These pili (nano-wires), longer than the bacterial body itself, are apparently used for electron transfer by the bacteria. In sufficient numbers, they could conceivably alter the electrical resistivity of a volume of earth. In summary, our understanding for the cause of anomalous conductive zones associated with areas impacted by LNAPL spills has been significantly improved by these recent developments.

Potentiometric surface of the intermediate aquifer system, west- central Florida, May 1987

USGS Publications Warehouse

Lewelling, B.R.

1988-01-01

The intermediate aquifer system within the Southwest Florida Water Management District underlies a 5,000 sq mi area of De Soto, Sarasota, Hardee, Manatee, and parts of Charlotte, Hillsborough, Highlands, and Polk Counties. The intermediate aquifer system occurs between the overlying surficial aquifer system and the underlying Floridan aquifer system, and consists of layers of sand, shell, clay, marl, limestone, and dolom of the Tamiami, Hawthorn, and Tampa Formations of late Tertiary age. The intermediate aquifer system contains one or more water-bearing units separated by discontinuous confining units. This aquifer system is the principal source of potable water in the southwestern part of the study area and is widely used as a source of water in other parts where wells are open to the intermediate aquifer system or to both the intermediate and Floridan aquifer systems. Yields of individual wells open to the intermediate aquifer system range from a few gallons to several hundred gallons per minute. The volume of water withdrawn from the intermediate aquifer system is considerably less than that withdrawn from the Floridan aquifer system in the study area. The surface was mapped by determining the altitude of water levels in a network of wells and is represented on maps by contours that connect points of equal altitude. The compos potentiometric surface of all water-bearing units within the intermediate aquifer system is shown. In areas where multiple aquifers exist, wells open to all aquifers were selected for water level measurements whenever possible. In the southwestern and lower coastal region of the study area, two aquifers and confining units are described for the intermediate aquifer system: the Tamiami-upper Hawthorn aquifer and the underlying lower Hawthorn-upper Tampa aquifer. The potentiometric surface of the Tamiami-upper Hawthorn aquifer is also shown. Water levels are from wells drilled and open exclusively to that aquifer. The exact boundary for the Tamiami-upper Hawthorn aquifer is undetermined because of limd geohydrologic data available from wells. (Lantz-PTT)

Rocky-shore communities as indicators of water quality: a case study in the Northwestern Mediterranean.

PubMed

Pinedo, Susana; García, María; Satta, Maria Paola; de Torres, Mariona; Ballesteros, Enric

2007-01-01

The collection of 152 samples from the upper sublittoral zone along the rocky coasts of Catalonia (Northwestern Mediterranean) was carried out in 1999 in order to test the suitability of littoral communities to be used as indicators of water quality in the frame of the European Water Framework Directive. Detrended correspondence analysis were performed to distinguish between different communities and to relate communities composition to water quality. Samples collected in reference sites were included in the analysis. Mediterranean rocky shore communities situated in the upper sublittoral zone can be used as indicators of the water quality: there is a gradient from high to bad status that comprises from dense Cystoseira mediterranea forests to green algae dominated communities. The geographical patterns in the distribution of these communities show that the best areas are situated in the Northern coast, where tourism is the main economic resource of the area, and the worst area is situated close to the metropolitan zone of Barcelona with high population and industrial development. Thus, Mediterranean sublittoral rocky shore communities are useful indicators of water quality and multivariate analysis are a suitable statistical tool for the assessment of the ecological status.

78 FR 12748 - Upper Yampa Water Conservancy District; Notice of Application Accepted for Filing, Soliciting...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-25

... allow commercial development of the site with a marina and restaurant operation that would have elements... the particular application. o. Filing and Service of Documents: Any filing must (1) bear in all...

Widespread gas hydrate instability on the upper U.S. Beaufort margin

USGS Publications Warehouse

Phrampus, Benjamin J.; Hornbach, Matthew J.; Ruppel, Carolyn D.; Hart, Patrick E.

2014-01-01

The most climate-sensitive methane hydrate deposits occur on upper continental slopes at depths close to the minimum pressure and maximum temperature for gas hydrate stability. At these water depths, small perturbations in intermediate ocean water temperatures can lead to gas hydrate dissociation. The Arctic Ocean has experienced more dramatic warming than lower latitudes, but observational data have not been used to study the interplay between upper slope gas hydrates and warming ocean waters. Here we use (a) legacy seismic data that constrain upper slope gas hydrate distributions on the U.S. Beaufort Sea margin, (b) Alaskan North Slope borehole data and offshore thermal gradients determined from gas hydrate stability zone thickness to infer regional heat flow, and (c) 1088 direct measurements to characterize multidecadal intermediate ocean warming in the U.S. Beaufort Sea. Combining these data with a three-dimensional thermal model shows that the observed gas hydrate stability zone is too deep by 100 to 250 m. The disparity can be partially attributed to several processes, but the most important is the reequilibration (thinning) of gas hydrates in response to significant (~0.5°C at 2σ certainty) warming of intermediate ocean temperatures over 39 years in a depth range that brackets the upper slope extent of the gas hydrate stability zone. Even in the absence of additional ocean warming, 0.44 to 2.2 Gt of methane could be released from reequilibrating gas hydrates into the sediments underlying an area of ~5–7.5 × 103 km2 on the U.S. Beaufort Sea upper slope during the next century.

The Multi-Stage History of Mt. Sharp

NASA Technical Reports Server (NTRS)

Allen, C.; Dapremont, A.

2013-01-01

The Curiosity rover is exploring Gale crater and Mt. Sharp, Gale's 5-km high central mound. We are investigating the history of alteration and erosion of Mt. Sharp using orbital imagery, spectroscopy and rover observations. Our results suggest a significant time gap between emplacement of the upper and lower sections of the mound. Crater counts show that the lower mound was formed soon after Gale itself, and that it contains distinct units ranging in altitude from approximately -4,500 to -1,800 m. Spectral data suggest that many units contain phyllosilicates. We found that these clay-bearing rocks occur in distinct layers concentrated below -2,900 m. Parts of the lower mound exhibit a transition from clays to sulfates with increasing altitude. The lower mound shows evidence of flowing water, including canyons and inverted channels. Wind erosion produced km-scale yardangs and scalloped cliffs. Our mapping shows that many yardangs in the lower mound are clay-bearing, with a predominant orientation of around N-S. Curiosity's ground-level images show myriad fine-scale, mainly horizontal layers in the lower mound. The rover has found stream beds and conglomerates, indicating that water once flowed on the crater floor. Drilling near the deepest point in Gale produced abundant clay, providing additional evidence of aqueous alteration. Upper mound units range in altitude from -2,100 m to +500 m, and mantle the lower mound above an angular unconformity. Most upper mound units are composed of layers. The formation age of the upper mound is unknown, since few craters are preserved. Clay-bearing layers are detectable in several locations, mainly at altitudes near -2,000 m. There is no evidence of water flow, but wind erosion has scalloped the surfaces and edges of layers, and fine-scale yardangs are common. Correlations between yardangs and clay spectra are apparent only in the lowermost units of the upper mound. Yardang orientations vary, and include N-S, NW-SE, and NE-SW. Upper mound units resemble the planet-wide Medusae Fossae formation, dated as Hesperian and argued to be composed of ignimbrites. Medusae Fossae layers are easily eroded by wind, and our mapping demonstrates their resemblance to upper mound fine-scale yardangs. The history of Mt. Sharp started with deposition and lithification of sediments shortly after crater formation. Some lower mound layers were partially altered to clays and sulfates, and water formed streams and canyons. Wind erosion of the lower mound produced large-scale yardangs, particularly in clay-rich layers, oriented generally N-S. Upper mound units were emplaced following a considerable period of wind erosion. The absence of water flow on the upper mound suggests that these units were emplaced after atmospheric loss rendered water unstable at the surface. The shift in dominant wind direction, as indicated by yardang orientations, also argues for a time gap between erosion of the lower and upper mound. These observations are consistent with upper mound units being related to the Hesperian Medusae Fossae formation. During 2014 Curiosity is expected to reach the foot of Mt. Sharp and ascend through the clay-rich layers, into the sulfate-rich layers, and possibly past the interface with the upper mound. This will be a unique opportunity to field check geologic models on the surface of Mars.

Environmental assessment of water, sediment, and biota collected from the Bear Creek watershed, Colusa County, California

USGS Publications Warehouse

Rytuba, James J.; Hothem, Roger L.; Brussee, Brianne E.; Goldstein, Daniel; May, Jason T.

2015-01-01

The Cache Creek watershed lies within California's North Coast Range, an area with abundant geologic sources of mercury (Hg) and a long history of Hg contamination (Rytuba, 2000). Bear Creek, Cache Creek, and the North Fork of Cache Creek are the major streams of the Cache Creek watershed, encompassing 2978 km2. The Cache Creek watershed contains soils naturally enriched in Hg as well as natural springs (both hot and cold) with varying levels of aqueous Hg (Domagalski and others, 2004, Suchanek and others, 2004, Holloway and others 2009). All three tributaries are known to be significant sources of anthropogenically derived Hg from historic mines, both Hg and gold (Au), and associated ore storage/processing sites and facilities (Slotton and others, 1995, 2004; CVRWQCB, 2003; Schwarzbach and others, 2001; Gassel and others, 2005; Suchanek and others., 2004, 2008a, 2009). Historically, two of the primary sources of mercury contamination in the upper part of Bear Creek have been the Rathburn and Petray Hg Mines. The Rathburn Hg mine was discovered and initially mined in the early 1890s. The Rathburn and the more recently developed Petray open pit mines are localized along fault zones in serpentinite that has been altered and cut by quartz and chalcedony veins. Cold saline-carbonate springs are located perepheral to the Hg deposits and effluent from the springs locally has high concentrations of Hg (Slowey and Rytuba, 2008). Several ephemeral tributaries to Bear Creek drain the mine area which is located on federal land managed by the U.S. Bureau of Land Management (USBLM). The USBLM requested that the U.S. Geological Survey (USGS) measure and characterize Hg and other geochemical constituents in sediment, water, and biota to establish baseline information prior to remediation of the Rathburn and Petray mines. Samples sites were established in Bear Creek upstream and downstream from the mine area. This report is made in response to the USBLM request, the lead agency mandated to conduct a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) - Removal Site Investigation (RSI). The RSI applies to the possible removal of Hg-contaminated mine waste from Bear Creek. This report summarizes data obtained from field sampling of water, sediment, and biota in Bear Creek, above input from the mine area and downstream from the Rathburn-Petray mine area to the confluence with Cache Creek. Our results permit a preliminary assessment of the chemical constituents that could elevate levels of monomethyl Hg (MMeHg) in Bear Creek and its uptake by biota and provide baseline information for comparison to conditions after mine remediation is completed.

Borehole geophysical logging and aquifer-isolation tests conducted in well MG-1693 at North Penn Area 5 Superfund Site near Colmar, Montgomery County, Pennsylvania

USGS Publications Warehouse

Bird, Philip H.

2006-01-01

Borehole geophysical logging and aquifer-isolation (packer) tests were conducted in well MG-1693 (NP-87) at the North Penn Area 5 Superfund Site near Colmar, Montgomery County, Pa. Objectives of the study were to identify the depth and yield of water-bearing zones, occurrence of vertical borehole flow, and effects of pumping on water levels in nearby wells. Caliper, natural-gamma, single-point-resistance, fluidtemperature, fluid-resistivity, heatpulse-flowmeter, and borehole-video logs were collected. Vertical borehole-fluid movement direction and rate were measured under nonpumping conditions. The suite of logs was used to locate water-bearing fractures, determine zones of vertical borehole-fluid movement, and select depths to set packers. Aquifer-isolation tests were conducted to sample discrete intervals and to determine specific capacities of water-bearing zones and effects of pumping individual zones on water levels in two nearby monitor wells. Specific capacities of isolated zones during aquifer-isolation tests ranged from 0.03 to 3.09 (gal/min)/ft (gallons per minute per foot). Fractures identified by borehole geophysical methods as water-producing or water-receiving zones produced water when isolated and pumped.Water enters the borehole primarily through high-angle fractures at 416 to 435 ft bls (feet below land surface) and 129 to 136 ft bls. Water exits the borehole through a high-angle fracture at 104 to 107 ft bls, a broken casing joint at 82 ft bls, and sometimes as artesian flow through the top of the well. Thirteen intervals were selected for aquifer-isolation testing, using a straddle-packer assembly. The specific capacity of interval 1 was 2.09 (gal/min)/ft. The specific capacities of intervals 2, 3, and 4 were similar—0.27, 0.30, and 0.29 (gal/min)/ft, respectively. The specific capacities of intervals 5, 6, 7, 8, and 10 were similar—0.03, 0.04, 0.09, 0.09, and 0.04 (gal/min)/ft, respectively. Intervals 9, 11, and 12 each showed a strong hydraulic connection outside the borehole with intervals above and below the isolated interval. The specific capacities of intervals 9, 11, 12, and 13 were similar—2.12, 2.17, 3.09, and 3.08 (gal/min)/ft, respectively. The aquifer-isolation tests indicate that wells MG-1693 (NP-87) and MG-924 (NP-21) are connected primarily through the high-angle fracture from 416 to 435 ft bls. Pumping in either of these wells directly impacts the other well, allowing the pumped well to draw from water-bearing zones in the nonpumped well that are not present in or are not connected directly to the pumped well. The two boreholes act as a single, U-shaped well. The aquifer-isolation tests also show that the lower zones in well MG-1693 (NP-87) are a major source of hydraulic head in well MG-1661 (W-13) through the broken casing joint at 82 ft bls. Water moving upward from the lower intervals in well MG-1693 (NP-87) exits the borehole through the broken casing joint, moves upward outside the borehole, possibly around and (or) through a poor or damaged casing seal, and through the weathered zone above bedrock to well MG-1661 (W-13).Samples for volatile organic compounds (VOCs) were collected in nine isolated intervals. Six compounds were detected (1,1-dichloroethane, 1,1-dichloroethene, cis-1,2-dichloroethene, toluene, 1,1,1-trichloroethane, and trichloroethene (TCE)), and TCE was found in all nine isolated intervals. Intervals 4 (124-149 ft bls) and 6 (277-302 ft bls) had the highest total concentration of VOCs (6.66 and 6.2 micrograms per liter, respectively). Intervals 1 (68-93 ft bls) and 4 each had five compounds detected, which was the highest number of compounds detected. Interval 5 (252-277 ft bls) had the lowest total concentration of VOCs (0.08 microgram per liter) and the least number of VOCs detected (one). Detected compounds were not evenly distributed throughout the intervals. Contaminants were found in shallow, intermediate, and deep intervals and were associated with high-angle fractures and rough areas that showed no distinct fractures.

Paleomagnetism and environmental magnetism of GLAD800 sediment cores from Bear Lake, Utah and Idaho

USGS Publications Warehouse

Heil, C.W.; King, J.W.; Rosenbaum, J.G.; Reynolds, R.L.; Colman, Steven M.

2009-01-01

A ???220,000-year record recovered in a 120-m-long sediment core from Bear Lake, Utah and Idaho, provides an opportunity to reconstruct climate change in the Great Basin and compare it with global climate records. Paleomagnetic data exhibit a geomagnetic feature that possibly occurred during the Laschamp excursion (ca. 40 ka). Although the feature does not exhibit excursional behavior (???40?? departure from the expected value), it might provide an additional age constraint for the sequence. Temporal changes in salinity, which are likely related to changes in freshwater input (mainly through the Bear River) or evaporation, are indicated by variations in mineral magnetic properties. These changes are represented by intervals with preserved detrital Fe-oxide minerals and with varying degrees of diagenetic alteration, including sulfidization. On the basis of these changes, the Bear Lake sequence is divided into seven mineral magnetic zones. The differing magnetic mineralogies among these zones reflect changes in deposition, preservation, and formation of magnetic phases related to factors such as lake level, river input, and water chemistry. The occurrence of greigite and pyrite in the lake sediments corresponds to periods of higher salinity. Pyrite is most abundant in intervals of highest salinity, suggesting that the extent of sulfidization is limited by the availability of SO42-. During MIS 2 (zone II), Bear Lake transgressed to capture the Bear River, resulting in deposition of glacially derived hematite-rich detritus from the Uinta Mountains. Millennial-scale variations in the hematite content of Bear Lake sediments during the last glacial maximum (zone II) resemble Dansgaard-Oeschger (D-O) oscillations and Heinrich events (within dating uncertainties), suggesting that the influence of millennial-scale climate oscillations can extend beyond the North Atlantic and influence climate of the Great Basin. The magnetic mineralogy of zones IV-VII (MIS 5, 6, and 7) indicates varying degrees of post-depositional alteration between cold and warm substages, with greigite forming in fresher conditions and pyrite in the more saline conditions. Copyright ?? 2009 The Geological Society of America.

Magmatic processes revealed by anorthoclase textures and trace element modeling: The case of the Lajes Ignimbrite eruption (Terceira Island, Azores)

NASA Astrophysics Data System (ADS)

D'Oriano, Claudia; Landi, Patrizia; Pimentel, Adriano; Zanon, Vittorio

2017-11-01

The Lajes Ignimbrite on Terceira Island (Azores) records the last major pyroclastic density current-forming eruption of Pico Alto Volcano that occurred ca. 21 kyrs ago. This comenditic trachyte ignimbrite contains up to 30 vol% of crystals, mostly anorthoclase. Geochemical investigation of the products collected throughout two key outcrops reveals that major element compositions are poorly variable, whereas trace elements show significant variability, pointing to the presence of a zoned magma reservoir. Thermometry and oxygen fugacity estimations yielded pre-eruptive temperatures of 850-900 °C and ΔNNO from - 2.4 to - 1.8. Melt-alkali-feldspar hygrometer indicates magmatic H2O contents ranging from 5.8 wt% in the upper part of the reservoir to 3.6 wt% at the bottom, indicating that the magma reservoir (confined at 4 km depth) was mainly water-undersaturated before the eruption, except for the topmost portion. Two types of anorthoclase crystals were identified. Type 1 crystals show reverse to oscillatory zoning with An contents of 0.4-2.1 mol% and Ba of 200-2000 ppm. They formed in the middle/upper portion of the reservoir, where fractional crystallization processes dominated. Type 2 crystals, mainly present in the less evolved products, are characterized by patchy-zoned cores with large dissolution pockets surrounded by thick oscillatory-zoned rims and show a wide compositional range (An of 0.5-4.7 mol% and Ba of 142-4824 ppm). Their zoning patterns, together with whole-rock and glass compositions of the juvenile clasts, are consistent with the involvement of an anorthoclase-bearing cumulate from the bottom of the reservoir that underwent partial melting. Crystal dissolution was likely induced by the presence of a heat source at depth, without any mass transfer to the eruptible magma, as suggested by the lack of petrographic and chemical evidences of mixing between the resident comenditic trachyte and a mafic/intermediate magma. Thermal instability generated convective plumes that were responsible for the admittance of crystals from the cumulate level into the intermediate portions of the magma reservoir and possibly acted as trigger of the explosive eruption.

Understanding Differences in the Nitrogen Cycle in Low-Oxygen Zones in the Eastern Tropical North Pacific

NASA Astrophysics Data System (ADS)

Wood, C.; Travis, N. M.; Forbes, M. S.; Casciotti, K. L.

2016-12-01

Hypoxic and anoxic zones are found in oceans worldwide. These zones can be caused by warm water "caps" that trap colder water underneath the warm water so the cold water cannot replenish its oxygen. Processes such as global warming and eutrophication can also contribute to such oxygen-depleted zones. Thus, it is important to study these zones to investigate and reveal the impact humans have on ecosystems worldwide so we can fix the problems we have caused. The Eastern Tropical North Pacific (ETNP), off the southwestern coast of Mexico, contains a natural-oxygen deficient zone. On a research cruise to the ETNP in April 2016, incubations were conducted to measure the rates of nitrification in the upper water column (upper 100 m) at three stations. Incubations were conducted in light and dark bottles spiked with 15N-containing nitrite. In this study, nitrite concentration in incubation starting points was analyzed. For each point, four depths of increasing depth (they varied depending on the station) were analyzed, and for each depth there were three samples. For each sample five absorbance measurements were averaged to calculate nitrite concentration against known standards. Concentrations of nitrite were found to increase moving into the oxygen deficient zone. The nitrite peaks at the coastal stations were at shallower depths than the peak at the centermost station in the low-oxygen zone. At the centermost station within the oxygen-deficient region, the nitrite concentration at the primary peak was 1.6µM, which was the highest point out of all the stations. This nitrite concentration data will be expanded to all stations where 15N addition incubation experiments were performed. In the future, these time-zero data will be combined with time-24 data to calculate nitrite oxidation rates based on 15N isotope analysis. Measuring nitrite oxidation rates will help us further understand processes structuring nitrite accumulation in the ETNP low-oxygen zone.

Uranium-bearing copper deposits in the Coyote district, Mora County, New Mexico

USGS Publications Warehouse

Zeller, H.D.; Baltz, Elmer Harold

1954-01-01

Uranium-bearing copper deposits occur in steeply dipping beds of the Sangre de Cristo formation of Pennsylvanian and Permian(?) age south of Coyote, Mora County, N. Mex. Mapping and sampling of these deposits indicate that they are found in lenticular carbonaceous zones in shales and arkosic sandstones. Samples from these zones contain as much as 0.067 percent uranium and average 3 percent copper. Metatyuyamunite is dissemihatedin some of the arkosic sandstone beds, and uraninite is present in some of the copper sulfide nodules occurring in the shale. These sulfide nodules are composed principally of chalcocite but include some bornite, covellite, pyrite, and malachite. Most of the samples were collected near the surface from the weathered zone. The copper and uranium were probably deposited with the sediments and concentrated into zones during compaction and lithification. Carbonaceous material in the Sangre de Cristo formation provided the environment that precipitated uranium and copper from mineral-charged connate waters forced from the clayey sediments.

Assessing the Vulnerability of Public-Supply Wells to Contamination: Floridan Aquifer System Near Tampa, Florida

USGS Publications Warehouse

Jagucki, Martha L.; Katz, Brian G.; Crandall, Christy A.; Eberts, Sandra M.

2009-01-01

This fact sheet highlights findings from the vulnerability study of a public-supply well in Temple Terrace, Florida, northeast of Tampa. The well selected for study typically produces water at the rate of 700 gallons per minute from the Upper Floridan aquifer. Water samples were collected at the public-supply well and at monitoring wells installed in or near the simulated zone of contribution to the supply well. Samples of untreated water from the public-supply wellhead contained the undesirable constituents nitrate, arsenic, uranium, radon-222, volatile organic compounds (VOCs), and pesticides, although all were detected at concentrations less than established drinking-water standards, where such standards exist. Overall, study findings point to four primary factors that affect the movement and fate of contaminants and the vulnerability of the public-supply well in Temple Terrace: (1) groundwater age (how long ago water entered, or recharged, the aquifer); (2) short-circuiting of contaminated water through sinkholes; (3) natural geochemical processes within the aquifer; and (4) pumping stress. Although the public-supply well is completed in the Upper Floridan aquifer, it produces water with concentrations of nitrate, VOCs, and the natural contaminant radon that are intermediate between the typical composition of water from the Upper Floridan aquifer and that of the overlying surficial aquifer system. Mixing calculations show that the water produced by the public-supply well could consist of upwards of 50 percent water from the surficial aquifer system mixed with water from the Upper Floridan aquifer. Anthropogenically affected water from the surficial aquifer system travels rapidly to depth through sinkholes that must be directly connected to the cavernous zone intersected by the public-supply well (and several other production wells in the region). Such solution features serve as fast pathways to the well and circumvent the natural attenuation of nitrate and radon that occurs when water from the surficial aquifer flows downward through the confining unit and then through the Upper Floridan aquifer matrix. Roughly 50 percent of the simulated flow to the public-supply well consists of water less than about 10 years old, thus making the well vulnerable to contamination from human activities. Sampling at various depths in the public-supply well during pumping and nonpumping conditions showed that water entering the well from the cavernous zone had much higher arsenic concentrations during pumping conditions (18.9 ug/L) than during nonpumping conditions (4.2 ug/L). This implies that movement of arsenic to the public-supply well from the cavernous zone is enhanced by pumping. One possible explanation is that pumping increases the movement of water with elevated dissolved oxygen content through the cavernous zone, which causes dissolution of arsenic associated with pyrite. All public-supply wells in the area may not have the same level of vulnerability as the well studied - many of the public-supply wells in the region have lower pumping rates and longer open intervals that may draw in a larger proportion of old water that predates anthropogenic influences. Determining the similarity of water produced by various public-supply wells in the region to that of the surficial aquifer system is one measure of well vulnerability that could be used to prioritize monitoring and land-use planning efforts to protect the most vulnerable wells.

Nitrogen cycle between surface and mantle (Invited)

NASA Astrophysics Data System (ADS)

Watenphul, A.; Heinrich, W.

2009-12-01

Nitrogen cycling between the surface and the deep Earth occurs mainly through subduction of ammonium-bearing sediments and alterated oceanic crust and nitrogen release via degassing of molecular nitrogen. Whereas in most environments nitrogen is soon released to the surface via arc volcanism [1] or lost during increasing metamorphic grade [2] at cold slab conditions nitrogen remains in the rocks at least down to 90 km and very probably beyond the depth locus of island arc magmatism [3]. In these rocks, nitrogen is initially bound as ammonium, substituting potassium in the relevant K-bearing phases such as clay minerals, micas, and feldspars, due to similarities in the ionic radius and charge. Multi-anvil experiments [4] have shown that at pressures exceeding the upper stability of phengitic mica and feldspar, ammonium is easily incorporated into high-pressure successor K-bearing phases such as K-cymrite, K-Si-wadeite, K-hollandite and to minor amounts also into omphacitic clinopyroxene. This implies that NH4 can probably be transported down to the transition zone and beyond. The global nitrogen input to the mantle as NH4 via cold slab subduction and the global output to the atmosphere as N2 through mid-ocean ridge basalts and volcanic arcs roughly balance each other [3,5] and are estimated to about 3 - 5 × 1010 mol/a N. Because a large portion of the nitrogen release occurs at mid-ocean ridges [1], a nitrogen reservoir in peridotites probably does exist. High-pressure experiments up to 13 GPa, 750 °C have shown that Cr-diopside may store NH4 by up to 500 to 1000 ppm, making clinopyroxene the ideal candidate for nitrogen storage at depth. If so, the nitrogen storage capacity of the upper mantle is roughly estimated at 1012 mol N. This reservoir also contributes to the deep Earth's water budget. The input of NH4 by slab minerals and the output as N2 requires the occurrence of oxidation reactions during the recycling process. Nitrogen speciation in H-N-O fluids is dependent on oxygen fugacity fO2, which changes with depth. At relevant upper mantle conditions with fO2 around ± 2 log units relative to FMQ [6], H-N-O fluids consist of water and molecular nitrogen. With depth fO2 may decrease by several log units [6], so that in H-N-O fluids NH3/NH4+ would predominate at the middle and lower part of the upper mantle. This stabilizes the NH4-component relative to N2 plus water in Cr-diopside and possibly also in other high-pressure phases. This would imply that nitrogen indeed can be stored as ammonium within the mid and lower part of the upper mantle and that towards shallower depths it is lost due to oxidation and degassing. The stability of ammonium as a component in subducted slabs and mantle phases is, therefore, very important for long-time, large-scale recycling of nitrogen and hydrogen between the Earth's crust and the deeper mantle. References: [1] Sano et al. (2001). Chem Geol, 171, 263-271. [2] Sadofsky and Bebout (2000). GCA, 64, 2835-2849. [3] Busigny et al. (2003). EPSL, 215, 27-42. [4] Watenphul et al. (2009). Am Min, 94, 283-292. [5] Hilton et al. (2002). Rev Mineral Geochem, 47, 319-370. [6] Frost and McCammon (2008). Annu Rev Earth Pl Sc, 36, 389-420.

Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones.

PubMed

Kalvelage, Tim; Lavik, Gaute; Jensen, Marlene M; Revsbech, Niels Peter; Löscher, Carolin; Schunck, Harald; Desai, Dhwani K; Hauss, Helena; Kiko, Rainer; Holtappels, Moritz; LaRoche, Julie; Schmitz, Ruth A; Graco, Michelle I; Kuypers, Marcel M M

2015-01-01

Oxygen minimum zones are major sites of fixed nitrogen loss in the ocean. Recent studies have highlighted the importance of anaerobic ammonium oxidation, anammox, in pelagic nitrogen removal. Sources of ammonium for the anammox reaction, however, remain controversial, as heterotrophic denitrification and alternative anaerobic pathways of organic matter remineralization cannot account for the ammonium requirements of reported anammox rates. Here, we explore the significance of microaerobic respiration as a source of ammonium during organic matter degradation in the oxygen-deficient waters off Namibia and Peru. Experiments with additions of double-labelled oxygen revealed high aerobic activity in the upper OMZs, likely controlled by surface organic matter export. Consistently observed oxygen consumption in samples retrieved throughout the lower OMZs hints at efficient exploitation of vertically and laterally advected, oxygenated waters in this zone by aerobic microorganisms. In accordance, metagenomic and metatranscriptomic analyses identified genes encoding for aerobic terminal oxidases and demonstrated their expression by diverse microbial communities, even in virtually anoxic waters. Our results suggest that microaerobic respiration is a major mode of organic matter remineralization and source of ammonium (~45-100%) in the upper oxygen minimum zones, and reconcile hitherto observed mismatches between ammonium producing and consuming processes therein.

Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones

PubMed Central

Kalvelage, Tim; Lavik, Gaute; Jensen, Marlene M.; Revsbech, Niels Peter; Löscher, Carolin; Schunck, Harald; Desai, Dhwani K.; Hauss, Helena; Kiko, Rainer; Holtappels, Moritz; LaRoche, Julie; Schmitz, Ruth A.; Graco, Michelle I.; Kuypers, Marcel M. M.

2015-01-01

Oxygen minimum zones are major sites of fixed nitrogen loss in the ocean. Recent studies have highlighted the importance of anaerobic ammonium oxidation, anammox, in pelagic nitrogen removal. Sources of ammonium for the anammox reaction, however, remain controversial, as heterotrophic denitrification and alternative anaerobic pathways of organic matter remineralization cannot account for the ammonium requirements of reported anammox rates. Here, we explore the significance of microaerobic respiration as a source of ammonium during organic matter degradation in the oxygen-deficient waters off Namibia and Peru. Experiments with additions of double-labelled oxygen revealed high aerobic activity in the upper OMZs, likely controlled by surface organic matter export. Consistently observed oxygen consumption in samples retrieved throughout the lower OMZs hints at efficient exploitation of vertically and laterally advected, oxygenated waters in this zone by aerobic microorganisms. In accordance, metagenomic and metatranscriptomic analyses identified genes encoding for aerobic terminal oxidases and demonstrated their expression by diverse microbial communities, even in virtually anoxic waters. Our results suggest that microaerobic respiration is a major mode of organic matter remineralization and source of ammonium (~45-100%) in the upper oxygen minimum zones, and reconcile hitherto observed mismatches between ammonium producing and consuming processes therein. PMID:26192623

Tidal-Fluvial and Estuarine Processes in the Lower Columbia River: II. Water Level Models, Floodplain Wetland Inundation, and System Zones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jay, David A.; Borde, Amy B.; Diefenderfer, Heida L.

Spatially varying water-level regimes are a factor controlling estuarine and tidal-fluvial wetland vegetation patterns. As described in Part I, water levels in the Lower Columbia River and estuary (LCRE) are influenced by tides, river flow, hydropower operations, and coastal processes. In Part II, regression models based on tidal theory are used to quantify the role of these processes in determining water levels in the mainstem river and floodplain wetlands, and to provide 21-year inundation hindcasts. Analyses are conducted at 19 LCRE mainstem channel stations and 23 tidally exposed floodplain wetland stations. Sum exceedance values (SEVs) are used to compare wetlandmore » hydrologic regimes at different locations on the river floodplain. A new predictive tool is introduced and validated, the potential SEV (pSEV), which can reduce the need for extensive new data collection in wetland restoration planning. Models of water levels and inundation frequency distinguish four zones encompassing eight reaches. The system zones are the wave- and current-dominated Entrance to river kilometer (rkm) 5; the Estuary (rkm-5 to 87), comprised of a lower reach with salinity, the energy minimum (where the turbidity maximum normally occurs), and an upper estuary reach without salinity; the Tidal River (rkm-87 to 229), with lower, middle, and upper reaches in which river flow becomes increasingly dominant over tides in determining water levels; and the steep and weakly tidal Cascade (rkm-229 to 234) immediately downstream from Bonneville Dam. The same zonation is seen in the water levels of floodplain stations, with considerable modification of tidal properties. The system zones and reaches defined here reflect geological features and their boundaries are congruent with five wetland vegetation zones« less

FLUID EVOLUTION AND MINERAL REACTIONS DURING SHEAR ZONE FORMATION AT NUSFJORD, LOFOTEN, NORWAY (Invited)

NASA Astrophysics Data System (ADS)

Kullerud, K.

2009-12-01

At Nusfjord in Lofoten, Norway, three 0.3 - 3 m thick shear zones occur in a gabbro-anorthosite. During deformation, the shear zones were infiltrated by a hydrous fluid enriched in Cl. In the central parts of the shear zones, fluid-rock interaction resulted in complete break-down of the primary mafic silicates. Complete hydration of these minerals to Cl-free amphibole and biotite suggests that the hydrous fluid was present in excess during deformation in these parts of the shear zones. Along the margins of the shear zones, however, the igneous mafic silicates (Cpx, Bt, Opx) were only partly overgrown by hydrous minerals. Here, Cl-enriched minerals (Amph, Bt, Scp, Ap) can be observed. Amphibole shows compositions covering the range 0.1 - 4.0 wt % Cl within single thin sections. Mineral textures and extreme compositional variations of the Cl-bearing minerals indicate large chemical gradients of the fluid phase. Relics of primary mafic silicates and compositionally zoned reaction coronas around primary mafic silicates suggest that the free fluid was totally consumed before the alteration of the primary phases were completed. The extreme variations in the Cl-content of amphibole are inferred to monitor a gradual desiccation of the Cl-bearing grain-boundary fluid during fluid-mineral reactions accordingly: 1) The first amphibole that formed during the reactions principally extracted water from the fluid, resulting in a slight increase in the Cl content of the fluid. 2) Continued amphibole-forming reactions resulted in gradual consumption of the free fluid phase, principally by extracting water from the fluid, resulting in an increase in its Cl-content. Higher Cl-content of the fluid resulted in higher Cl-content of the equilibrium amphibole. 3) The most Cl-enriched amphibole (4 wt % Cl) formed in equilibrium with the last volumes of the grain-boundary fluid, which had evolved to a highly saline solution. Mineral reactions within a 1-2 thick zone of the host rock along the contact to the shear zones indicate a more complicated involvement of fluids during shear zone formation than described above. Apparently, fluids have been transported laterally from the outer parts of the shear zones into the gabbro-anorthosite along thin recrystallized zones of plagioclase. The fluid that infiltrated the undeformed host rock of the shear zones resulted in formation of Cl-free amphibole and garnet between the primary mafic minerals and plagioclase. A working hypothesis is that narrow fractures formed within the host rock, outside the sheared rock during shear zone formation. During shear zone formation, the central parts of the shear zones were completely hydrated by an externally derived Cl-bearing hydrous fluid. Some of the fluid migrated to the marginal parts of the shear zones and evolved to a highly saline solution. However, during desiccation of the fluid along the marginal parts of the shear zones, some of the fluid escaped along narrow fractures into the host rock of the shear zones. The Cl-free amphibole that formed from this fluid suggests that the narrow pathways of the fluid provided a path for water transport, but acted as a filter for the much larger ions of Cl.

The mantle beneath the Red Sea margin: xenoliths from western Saudi Arabia

NASA Astrophysics Data System (ADS)

McGuire, Anne Vaughan

1988-07-01

Xenoliths from alkali basalts in western Saudi Arabia provide the opportunity to study the composition and rheology of the mantle beneath the Red Sea rift margins. Characteristics of mantle xenolith suites from each of three localities in western Saudi Arabia can be related to locality position relative to the rift axis, and to crustal thickness and heat flow at each locality. Mantle xenoliths from Harrat al Birk, nearest the rift axis, are dominantly websterites (± spinel, plagioclase, amphibole, olivine), garnet clinopyroxenite, and two-pyroxene gabbro (± olivine); peridotite xenoliths, are rare. Garnet clinopyroxenites contain zoned clinopyroxene with Fe-Al-rich rims and reaction rims on garnet formed by breakdown of garnet to orthopyroxene + clinopyroxene + spinel + plagioclase. Zoning and reaction rims are interpreted as forming under conditions of increasing temperature. Thermobarometry on Harrat al Birk garnet-bearing xenoliths yield high temperatures (1015-1040°C) at about 12 kbar. The abundance of plagioclase-bearing assemblages may be related to a relatively shallow upper mantle which extends up into stability fields for plagioclase-bearing pyroxenite and peridotite. Harrat al Kishb and Harrat Hutaymah are farther from the Red Sea axis, on the flanks of the rift. The mantle xenolith suites of al Kishb and Hutaymah are similar, consisting of abundant spinel peridotite and spinel pyroxenite xenoliths and minor garnet pyroxenites; plagioclase-bearing xenoliths are extremely rare. The Harrat Hutaymah suite includes wehrlite and amphibole-bearing peridotite lithologies not found at al Kishb. Variation of peridotite composition may reflect varying degrees of partial melt extraction. Igneous textures of some pyroxenite xenoliths and structural relationships in composite peridotite/pyroxenite nodules suggest that pyroxenites formed by crystallization of magmas within mantle veins. Abundant pyroxenites and fragments of amphibole veins reflect the activity of magmas and hydrous fluids within the mantle. Thermobarometry of al Kishb and Hutaymah garnet-bearing nodules yield temperatures of 1000-1050 °C at pressures of about 13.5-16.0 kbar. Mineral zoning and exsolution features indicate decreasing temperature conditions in the mantle at the flanks of the Red Sea rift.

Spatial-altitudinal and temporal variation of Degree Day Factors (DDFs) in the Upper Indus Basin

NASA Astrophysics Data System (ADS)

Khan, Asif; Attaullah, Haleema; Masud, Tabinda; Khan, Mujahid

2017-04-01

Melt contribution from snow and ice in the Hindukush-Karakoram-Himalayan (HKH) region could account for more than 80% of annual river flows in the Upper Indus Basin (UIB). Increase or decrease in precipitation, energy input and glacier reserves can significantly affect water resources of this region. Therefore improved hydrological modelling and accurate future water resources prediction are vital for food production and hydro-power generation for millions of people living downstream, and are intensively needed. In mountain regions Degree Day Factors (DDFs) significantly vary on spatial and altitudinal basis, and are primary inputs of temperature-based hydrological modelling. However previous studies have used different DDFs as calibration parameters without due attention to the physical meaning of the values employed, and these estimates possess significant variability and uncertainty. This study provides estimates of DDFs for various altitudinal zones in the UIB at sub-basin level. Snow, clean ice and ice with debris cover bear different melt rates (or DDFs), therefore areally-averaged DDFs based on snow, clean and debris-covered ice classes in various altitudinal zones have been estimated for all sub-basins of the UIB. Zonal estimates of DDFs in the current study are significantly different from earlier adopted DDFs, hence suggest a revisit of previous hydrological modelling studies. DDFs presented in current study have been validated by using Snowmelt Runoff Model (SRM) in various sub-basins with good Nash Sutcliffe coefficients (R2 > 0.85) and low volumetric errors (Dv<10%). DDFs and methods provided in the current study can be used in future improved hydrological modelling and to provide accurate predictions of future river flows changes. The methodology used for estimation of DDFs is robust, and can be adopted to produce such estimates in other regions of the, particularly in the nearby other HKH basins.

Scaly fabrics and veins of the Mugi and Makimine mélanges in the Shimanto belt, SW Japan

NASA Astrophysics Data System (ADS)

Ramirez, G. E.; Fisher, D. M.; Yamaguchi, A.; Kimura, G.

2016-12-01

Two regionally extensive ancient subduction fault zones provide a microstructural record of the plate boundary deformation associated with underthrusting. These rocks exhibit many of the characteristics associated with exposed ancient subduction fault zones worldwide, including: (1) σ1 is near orthogonal to the deformation fabric (2) there are microstructurally pervasive quartz and calcite filled veins concentrated in coarser blocks and along extensional jogs on slip surfaces, (3) evidence for local diffusion of silica sourced from web-like arrays of slip surfaces (i.e., scaly fabrics), and (4) evidence for cycles of cracking and sealing that record cyclic variations in stress. We present new backscatter SEM observations of scaly fabrics from two ancient subduction-related shear zones from the Shimanto Belt in Japan that exemplify these characteristics and represent the full temperature range of the seismogenic zone: 1) the Mugi mélange (lower ( 130-150 °C) and upper ( 170-200 °C) sections) and 2) Makimine mélange (peak temperatures of 340 °C). The Mugi mélange is an underplated duplex consisting of two horses separated by an OOST. The upper section is bounded at the top by a pseudotachylite-bearing paleodécollement. The Makimine mélange was underplated at the downdip limit of the seismogenic zone. The scaly fabrics associated with these shear zones display significantly different microstructural characteristics. A slip surface from along the upper Mugi is characterized by broader ( 20-30 μm), zones of quartz-poor, anastomosing shear zones composed of fine-grained (0.5-2 μm in length) phyllosilicates. The Makimine mélange exhibits thinner (10-20 μm), anastomosing shear zones with coarser (1-4 μm in length) phyllosilicate grains that are more strongly oriented into parallelism with slip surfaces. Quartz veins are pervasively developed in more competent blocks and are oriented at near perpendicular angles to the slip surfaces. Microstructural analyses of ancient subduction-related faults show differences with temperature that highlight the importance of establishing the geochemical processes and activation energies that contribute to slip, fracturing, and healing of rocks that underthrust the subduction interface.

Assessment of hydrogeologic conditions with emphasis on water quality and wastewater injection, southwest Sarasota and West Charlotte counties, Florida

USGS Publications Warehouse

Hutchinson, C.B.

1992-01-01

The 250-square-mile area of southwest Sarasota and west Charlotte Counties is underlain by a complex hydrogeologic system having diverse ground-water quality. The surficial and intermediate aquifer systems and the Upper Floridan aquifer of the Floridan aquifer system contain six separate aquifers, or permeable zones, and have a total thickness of about 2,000 feet. Water in the clastic surficial aquifer system is potable and is tapped by hundreds of shallow, low-yielding supply wells. Water in the mixed clastic and carbonate intermediate aquifer system is potable in the upper part, but in the lower part, because of increasing salinity, it is used primarily for reverse-osmosis desalinization feed water and irrigation. Within the Upper Floridan aquifer, limestone and dolomite of the Suwannee permeable zone are tapped by irrigation and reverse-osmosis supply wells. The underlying, less permeable limestone of the Suwannee-Ocala semiconfining unit generally encompasses the transition zone between freshwater and very saline water. Interbedded limestone and dolomite of the Ocala-Avon Park moderately permeable zone and Avon Park highly permeable zone compose the deep, very saline injection zone. Potential ground-water contamination problems include flooding by storm tides, upward movement of saline water toward pumping centers by natural and induced leakage or through improperly constructed and abandoned wells, and lateral and vertical movement of treated sewage and reverse-osmosis wastewater injected into deep zones. Effects of flooding are evident in coastal areas where vertical layering of fresh and saline waters is observed. Approximately 100 uncontrolled flowing artesian wells that have interaquifer flow rates as high as 350 gallons per minute have been located and scheduled for plugging by the Southwest Florida Water Management District--in an attempt to improve ground-water quality of the shallow aquifers. Because each aquifer or permeable zone has unique head and water-quality characteristics, construction of single-zone wells would eliminate cross-contamination and borehole interflow. Such a program, when combined with the plugging of shallow-cased wells having long open-hole intervals connecting multiple zones, would safeguard ground-water resources in the study area. The study area encompasses seven wastewater injection sites that have a projected capacity for injecting 29 million gallons per day into the zone 1,100 to 2,050 feet below land surface. There are six additional sites within 20 miles. The first well began injecting reverse-osmosis wastewater in 1984, and since then, other wells have been drilled and permitted for injection of treated sewage. A numerical model was used to evaluate injection-well design and potential for movement of injected wastewater within the hydrogeologic framework. The numerical model was used to simulate injection through a representative well at a rate of 1 million gallons per day for 10 years. In this simulation, a convection cell developed around the injection well with the buoyant fresh injectant rising to form a lens within the injection zone below the lower Suwannee-Ocala semiconfining unit. Around an ideal, fully penetrating well cased 50 feet into the injection zone and open from a depth of 1,150 feet to 2,050 feet, simulations show that the injectant moves upward to a depth of 940 feet, forms a lens about 600 feet thick, and spreads radially outward to a distance of about 2,300 feet after 10 years. Comparison simulations of injection through wells having open depth intervals of 1,150 to 1,400 feet and 1,450 to 2,050 feet demonstrate that such changes in well construction have little effect on the areal spread of the injectant lens or the rate of upward movement. Simulations also indicate that reverse-osmosis wastewater injected beneath a supply well field, where water levels above the semiconfining unit are lowered 20 feet by pumping, would move upward after 10 years to a de

Relationship between pyrite Stability and arsenic mobility during aquifer storage and recovery in southwest central Florida.

PubMed

Jones, Gregg W; Pichler, Thomas

2007-02-01

Elevated arsenic concentrations are common in water recovered from aquifer storage and recovery (ASR) systems in west-central Florida that store surface water. Investigations of the Suwannee Limestone of the Upper Floridan aquifer, the storage zone for ASR systems, have shown that arsenic is highest in pyrite in zones of high moldic porosity. Geochemical modeling was employed to examine pyrite stability in limestone during simulated injections of surface water into wells open only to the Suwannee Limestone with known mineralogy and water chemistry. The goal was to determine if aquifer redox conditions could be altered to the degree of pyrite instability. Increasing amounts of injection water were added to native storage-zone water, and resulting reaction paths were plotted on pyrite stability diagrams. Native storage-zone water plotted within the pyrite stability field, indicating that conditions were sufficiently reducing to allow for pyrite stability. Thus, arsenic is immobilized in pyrite, and its groundwater concentration should be low. This was corroborated by analysis of water samples, none of which had arsenic concentrations above 0.036 microg/L. During simulation, however, as injection/native storage-zone water ratios increased, conditions became less reducing and pyrite became unstable. The result would be release of arsenic from limestone into storage-zone water.

When interflow also percolates: downslope travel distances and hillslope process zones.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, C. Rhett; Bitew, Menberu; Du, Enhao

2014-02-17

In hillslopes with soils characterized by deep regoliths, such as Ultisols,Oxisols, and Alfisols, interflow occurs episodically over impeding layers near and parallel to the soil surface such as low-conductivity B horizons (e.g.Newman et al., 1998; Buttle andMcDonald, 2002; Du et al., In Review), till layers (McGlynn et al., 1999; Bishop et al., 2004), hardpans (McDaniel et al., 2008), C horizons (Detty and McGuire, 2010), and permeable bedrock (Tromp van Meerveld et al., 2007). As perched saturation develops within and above these impeding but permeable horizons, flow moves laterally downslope, but the perched water also continues to percolate through the impedingmore » horizon to the unsaturated soils and saprolite below. Perched water and solutes will eventually traverse the zone of perched saturation above the impeding horizon and then enter and percolate through the impeding horizon. In such flow situations, only lower hillslope segments with sufficient downslope travel distance will deliver water to the riparian zone within the time scale of a storm.farther up the slope, lateral flow within the zone of perched saturation. will act mainly to shift the point of percolation (location where a water packet leaves the downslope flow zone in the upper soil layer and enters the impeding layer) down the hillslope from the point of infiltration. In flatter parts of the hillslope or in areas with little contrast between the conductivities of the upper and impeding soil layers, lateral flow distances will be negligible.« less

Method of removing oxidized contaminants from water

DOEpatents

Amonette, James E.; Fruchter, Jonathan S.; Gorby, Yuri A.; Cole, Charles R.; Cantrell, Kirk J.; Kaplan, Daniel I.

1998-01-01

The present invention is a method for removing oxidized contaminant(s) from water. More specifically, the invention has the steps of contacting water containing the oxidized contaminant(s) with a layered aluminosilicate having Fe(II). The aluminosilicate may contain naturally occurring Fe(II), or the Fe(II) may be produced by reducing Fe(III) that is initially present. Reduction may be either by exposure to a chemical or biological reductant. Contacting the water containing oxidized contaminant(s) may be by (1) injection of Fe(II)-containing layered aluminosilicate, via a well, into a saturated zone where it is likely to intercept the contaminated water; (2) injection of contaminated water into a vessel containing the Fe(II)-bearing layered aluminosilicate; and (3) first reducing Fe(III) in the layered aluminosilicate to Fe(II) by injection of a biological or chemical reductant, into an aquifer or vessel having sufficient Fe(III)-bearing aluminosilicate to produce the necessary Fe(II).

Method of removing oxidized contaminants from water

DOEpatents

Amonette, J.E.; Fruchter, J.S.; Gorby, Y.A.; Cole, C.R.; Cantrell, K.J.; Kaplan, D.I.

1998-07-21

The present invention is a method for removing oxidized contaminant(s) from water. More specifically, the invention has the steps of contacting water containing the oxidized contaminant(s) with a layered aluminosilicate having Fe(II). The aluminosilicate may contain naturally occurring Fe(II), or the Fe(II) may be produced by reducing Fe(III) that is initially present. Reduction may be either by exposure to a chemical or biological reductant. Contacting the water containing oxidized contaminant(s) may be by (1) injection of Fe(II)-containing layered aluminosilicate, via a well, into a saturated zone where it is likely to intercept the contaminated water; (2) injection of contaminated water into a vessel containing the Fe(II)-bearing layered aluminosilicate; and (3) first reducing Fe(III) in the layered aluminosilicate to Fe(II) by injection of a biological or chemical reductant, into an aquifer or vessel having sufficient Fe(III)-bearing aluminosilicate to produce the necessary Fe(II). 8 figs.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone

NASA Astrophysics Data System (ADS)

Lee, C.; Rainville, L.; Gobat, J. I.; Perry, M. J.; Freitag, L. E.; Webster, S.

2016-12-01

The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer and Atlantic waters), and elevated surface wave energy that acts to deform and fracture sea ice. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, how the balance of processes shift as a function of ice fraction and distance from open water, and how these processes impact sea ice evolution, a network of autonomous platforms sampled the atmosphere-ice-ocean system in the Beaufort, beginning in spring, well before the start of melt, and ending with the autumn freeze-up. Four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Gliders penetrated up to 200 km into the ice pack, under complete ice cover for up to 10 consecutive days. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse late in the season as they progress through the MIZ and into open water. Stratification just above the Pacific Summer Water rapidly weakens near the ice edge and temperature variance increases, likely due to mixing or energetic vertical exchange associated with strong lateral gradients at the MIZ. This presentation will discuss the evolution of the Arctic upper ocean over the summer to the start of freeze up and the relationship of its variability to sea ice extent and atmospheric forcing.

[Distribution characteristics of dissolved oxygen and mechanism of hypoxia in the upper estuarine zone of the Daliaohe River].

PubMed

Yang, Li-Na; Li, Zheng-Yan; Zhang, Xue-Qing

2011-01-01

Based on field surveys in the upper estuarine zone of the Daliaohe River in Spring and Summer of 2009, the spatial and temporal distributions of dissolved oxygen were analyzed and the mechanism of hypoxia were preliminarily discussed. The results indicated that DO concentrations were higher in the river mouth and lower in the upper reaches, higher in surface layers and lower in bottom concerning its spatial distribution. For its temporal distribution, DO concentrations were higher in daytime and lower at night, higher in Spring and lower in Summer. The DO concentrations in the upper estuarine zone of the Daliaohe River in Summer ranged between 1.36-4.77 mg/L with an average of 3.44 mg/L. The concentrations in the lower reaches were higher with an average of 3.94 mg/L. A large hypoxia area was recorded in Summer in the upper reaches of the estuary starting from about 45 km away from the river gate with an average DO concentration of 2.33 mg/L and a minimum of 1.36 mg/L. The correlation analysis showed that DO concentration was significantly correlated with nutrients and permanganate index. Excessive discharge of nutrients and organic pollutants were, therefore, main factors causing hypoxia, and water column stratification due to temperature rise in Summer in surface layers led to further reduction of DO in bottom layers of the water.

Water chemistry at Snowshoe Mountain, Colorado: mixed processes in a common bedrock

USGS Publications Warehouse

Hoch, A.R.; Reddy, M.M.

2001-01-01

At Snowshoe Mountain the primary bedrock is quite homogeneous, but weathering processes vary as waters moves through the soils, vadose zone and phreatic zone of the subsurface. In the thin soil, physical degradation of tuff facilitates preferential dissolution of potassium ion from glass within the rock matrix, while other silicate minerals remain unaltered. In the vadose zone, in the upper few meters of fractured bedrock, dilute water infiltrates during spring snowmelt and summer storms, leading to preferential dissolution of augite exposed on fracture surfaces. Deeper yet, in the phreatic zone of the fractured bedrock, Pleistocene calcite fracture fillings dissolve, and dioctahedral and trioctahedral clays form as penetrative weathering alters feldspar and pyroxene. Alkalinity is generated and silica concentrations are buffered by mineral alteration reactions.

Magma interaction in the root of an arc batholith

NASA Astrophysics Data System (ADS)

Chapman, T.; Robbins, V.; Clarke, G. L.; Daczko, N. R.; Piazolo, S.

2016-12-01

Fiordland, New Zealand, preserves extensive Cretaceous arc plutons, emplaced into parts of the Delamerian/Ross Orogen. Dioritic to gabbroic material emplaced at mid to lower crustal levels are exposed in the Malaspina Pluton (c. 1.2 GPa) and the Breaksea Orthogneiss (c. 1.8 GPa). Distinct magmatic pulses can be mapped in both of these plutons consistent with cycles of melt advection. Relationships are consistent with predictions from lower crustal processing zones (MASH and hot zones) considered important in the formation of Cordilleran margins. Metamorphic garnet growth is enhanced along magmatic contacts, such as where hornblende gabbronorite is cut by garnet-clinopyroxene-bearing diorite. Such features are consistent with cycles of incremental emplacement, younger magma having induced localised garnet granulite metamorphism in wall rock of older material. Temperature estimates and microstructures preserved in garnet granulite are consistent with sub-solidus, water-poor conditions in both the Malaspina and Breaksea Orthogneiss. The extent and conditions of the metamorphism implies conditions and duration was incapable of partially melting older wall rock material. The nature of interactions in intermediate to basic compositions are assessed in terms of magma genesis in the Cretaceous batholith. Most of the upper crustal felsic I-type magmatism along the margin being controlled by high-pressure garnet-clinopyroxene fractionation.

Paracontinuous boundaries within the Devonian Columbus Limestone and Delaware Formation of central Ohio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Conkin, J.E.; Conkin, B.M.

1994-04-01

Internal units within the Columbus Limestone (Early Devonian Emsian [Schoharie] to Middle Devonian Eifelian [late Onesquethawan]) and the Delaware Formation (Middle Devonian early Givetian [Cazenovian]) of central Ohio are separated by disconformities of the magnitude of paracontinuities. Stauffer (1909) divided the Columbus Limestone into zones A--H and the Delaware Formation into zones I--M. Within the Columbus, the A Zone (conglomerate at the base of Bellepoint Member) disconformably overlies Late Silurian beds. The D zone at top of the Bellepoint Member (bearing the Kawkawlin Metabentonite horizon) is overlain paracontinuously by the Marblehead Member (Lower Paraspirifer acuminatus-Spirifer macrothyris to Brevispirifer gregarius-Moellerina greeneimore » zones [= E--G zones]), with the Onondagan Indian Nation Metabentonite in the top of the G Zone. The Marblehead Member is overlain paracontinuously by a bone bed at base of the Venice Member (H zone = Upper Paraspirifer acuminatus- Spirifer duodenarius'' Zone). I Zone (Dublin Shale=Marcellus) of the Delaware Formation overlies the Columbus and has two bone beds at its base; Tioga Metabentonite (restricted) overlies the I Zone bone beds and is a few tenths to 1.85 feet above the base of the I Zone. Paracontinuities and bone beds occur at the bases of J, K, and L zones. Conkin and Conkin (1975) have shown Stauffer's (1909) M Zone is an extension of his L Zone. The Olentangy paracontinuously overlies the L Zone.« less

Life on the boundary: Environmental factors as drivers of habitat distribution in the littoral zone

NASA Astrophysics Data System (ADS)

Cefalì, Maria Elena; Cebrian, Emma; Chappuis, Eglantine; Pinedo, Susana; Terradas, Marc; Mariani, Simone; Ballesteros, Enric

2016-04-01

The boundary between land and sea, i.e. the littoral zone, is home to a large number of habitats whose distribution is primarily driven by the distance to the sea level but also by other environmental factors such as littoral's geomorphological features, wave exposure, water temperature or orientation. Here we explore the relative importance of those major environmental factors that drive the presence of littoral rocky habitats along 1100 Km of Catalonia's shoreline (Spain, NW Mediterranean) by using Geographic Information Systems and Generalized Linear Models. The distribution of mediolittoral and upper infralittoral habitats responded to different environmental factors. Mediolittoral habitats showed regional differences drawn by sea-water temperature and substrate type. Wave exposure (hydrodynamism), slope and geological features were only relevant to those mediolittoral habitats with specific environmental needs. We did not find any regional pattern of distribution in upper infralittoral habitats, and selected factors only played a moderate role in habitat distribution at the local scale. This study shows for the first time that environmental factors determining habitat distribution differ within the mediolittoral and the upper infralittoral zones and provides the basis for further development of models oriented at predicting the distribution of littoral marine habitats.

A review of water resources of the Umiat area, northern Alaska

USGS Publications Warehouse

Williams, John R.

1970-01-01

Surface-water supplies from the Colville River, small tributary creeks, and lakes are abundant in summer but limited in winter by low or zero flow in streams and thick ice cover on lakes. Fresh ground water occurs in unfrozen zones in alluvium and in the upper part of bedrock beneath the Colville River and beneath lakes that do not freeze to the bottom in winter. These unfrozen zones, forming depressions in the upper surface of permafrost, are maintained by flow of heat from bodies of surface water into subjacent alluvium and bedrock. Brackish or saline ground water occurs in bedrock beneath as much as 1,055 feet of permafrost in the Arctic foothills and beneath 750 to 800 feet of permafrost beneath low terraces of the Colville River valley. The foothill area is unfavorable for developing supplies of potable ground water because of the great depth to water, predominance of brackish or saline water, and low potential yield of the bedrock. In the Colville River valley, shallow unfrozen alluvium beneath the river and deep lakes will yield abundant year-round supplies of ground water, but the bedrock below permafrost yields less than 10 gpm (gallons per minute) of saline or brackish water.

Carbon storage, soil carbon dioxide efflux and water quality in three widths of piedmont streamside management zones

Treesearch

Erica F. Wadl; William Lakel; Michael Aust; John Seiler

2010-01-01

Streamside management zones (SMZs) are used to protect water quality. Monitoring carbon pools and fluxes in SMZs may a good indicator of the SMZ’s overall function and health. In this project we evaluated some of these pools and fluxes from three different SMZ widths (30.5, 15.3, and 7.6 m) in the Piedmont of Virginia. We quantified carbon storage in the soil (upper 10...

Development of a Unified Hydrostratigraphic Framework for the Floridan Aquifer System in Central and Southern Florida

NASA Astrophysics Data System (ADS)

Reese, R. S.

2008-05-01

The mostly carbonate Floridan aquifer system (FAS) of central and southern Florida is a widely used resource with a complex hydrostratigraphic framework that is managed primarily in a subregional context according to water management jurisdictional boundaries. As use of the FAS increases, a consistent regional hydrostratigraphic framework is needed for effective management across these boundaries. Stratigraphic marker horizons within and near the top of FAS were delineated and mapped to develop a preliminary, correlative stratigraphic framework. This framework was used to identify and determine aquifers, subaquifers, and confining units and map their spatial distribution. These horizons are based on lithologic changes and geophysical log signatures identified in previous studies, and they were extended throughout the study area primarily by correlation of natural gamma-ray logs. The FAS consists of the Upper Floridan aquifer, middle confining unit, and Lower Floridan aquifer. A regional, productive zone is delineated and informally referred to as the Avon Park permeable zone. This zone is present over most of the study area and is characterized by thick units of dolostone with interbedded limestone and high fracture permeability. The zone has been identified in different regions in previous studies, either as the upper part of the Lower Floridan aquifer or as the lower part of the Upper Floridan aquifer. In this study it is generally considered to be within the middle confining unit. Transmissivity of the Avon Park permeable zone, a major source of water supply, generally ranges from less than 1x104 up to 1.6x106 ft2/day, and is greatest in central Florida where dolomite is developed as a major component of the zone. A large area of low transmissivity (less than 105 ft2/day) in southern Florida coincides with an area where limestone is the predominant lithology within the zone. Major uses of the FAS now include withdrawal for public and agricultural supply, including treatment with reverse osmosis, aquifer storage and recovery, and disposal of treated wastewater. Water-level and water-quality conflicts could arise between these competing uses, and delineating the extent and hydraulic connectivity of the Avon Park permeable zone within the FAS may help managers and others predict and minimize such conflicts.

STRUCTURAL GEOMETRY OF AN EXHUMED UHP TERRANE IN THE EASTERN SULU OROGEN, CHINA: IMPLICATIONS FOR CONTINENTAL COLLISIONAL PROCESSES

NASA Astrophysics Data System (ADS)

Wang, L.; Kusky, T.

2009-12-01

High-precision 1:1,000 mapping of Yangkou Bay, eastern Sulu orogen, defines the structural geometry and history of the world’s most significant UHP (Ultrahigh Pressure) rock exposures. Four stages of folds are recognized in the UHP rocks and associated quartzo-feldspathic gneiss. Eclogite facies rootless F1 and isoclinal F2 folds are preserved locally in coesite-eclogite. Mylonitic to ultramylonitic cosesit-eclogite shear zones separate 5-10-meter-thick nappes of ultramafic-mafic UHP rocks from banded quartzo-feldspathic gneiss. These shear zones are folded, and progressively overprinted by amphibolite and greenschist facies shear zones that become wider with lower grade. The deformation sequences is explained by deep subduction of offscraped thrust slices of oceanic or lower continental crust, caught between the colliding North and South China cratons in the Mesozoic. After these slices were structurally isolated along the plate interface, they were rolled like ball-bearings, in the subduction channel during their exhumation, forming several generations of folds, sequentially lower-grade foliations and lineations, and intruded by several generations of in situ and exotically derived melts. The shear zones formed during different generations of deformation are wider with lower grades, suggesting that deep-crustal/upper mantle deformation operates efficiently (perhaps with more active crystallographic slip systems) than deformation at mid to upper crustal levels.

Sedimentological Control on Hydrate Saturation Distribution in Arctic Gas-Hydrate-Bearing Deposits

NASA Astrophysics Data System (ADS)

Behseresht, J.; Peng, Y.; Bryant, S. L.

2010-12-01

Grain size variations along with the relative rates of fluid phases migrating into the zone of hydrate stability, plays an important role in gas-hydrate distribution and its morphologic characteristics. In the Arctic, strata several meters thick containing large saturations of gas hydrate are often separated by layers containing small but nonzero hydrate saturations. Examples are Mt. Elbert, Alaska and Mallik, NW Territories. We argue that this sandwich type hydrate saturation distribution is consistent with having a gas phase saturation within the sediment when the base of gas hydrate stability zone (BGHSZ) was located above the sediment package. The volume change during hydrate formation process derives movement of fluid phases into the GHSZ. We show that this fluid movement -which is mainly governed by characteristic relative permeability curves of the host sediment-, plays a crucial role in the amount of hydrate saturation in the zone of major hydrate saturation. We develop a mechanistic model that enables estimating the final hydrate saturation from an initial gas/water saturation in sediment with known relative permeability curves. The initial gas/water saturation is predicted using variation of capillary entry pressure with depth, which in turn depends on the variation in grain-size distribution. This model provides a mechanistic approach for explaining large hydrate saturations (60%-75%) observed in zones of major hydrate saturation considering the governing characteristic relative permeability curves of the host sediments. We applied the model on data from Mount Elbert well on the Alaskan North Slope. It is shown that, assuming a cocurrent flow of gas and water into the GHSZ, such large hydrate saturations (up to 75%) cannot result from large initial gas saturations (close to 1-Sw,irr) due to limitations on water flux imposed by typical relative permeability curves. They could however result from modest initial gas saturations (ca. 40%) at which we have reasonable phase mobility ratios required for appropriate relative rates of gas and water transporting into GHSZ to form large hydrate saturations. Nevertheless, from the profile of capillary entry pressure vs. depth, we expect large initial gas saturations and thus the final high hydrate saturation suggests another form of water flow: water moves down through accumulated hydrate from the unfrozen water above. For this to happen the water phase must remain connected within the hydrate-bearing sediment. This seems plausible in hydrate bearing sediments because hydrate formation will be stopped before water saturation gets to very low values (lower than Sw,irr) due to salinity build up. The location of small hydrate saturations (10-15%) is consistent with the location of the residual gas phase established during water imbibition into these locations while they serve as a gas source to the layers above.

Using Geophysics to Define Hydrostratigraphic Units in the Edwards and Trinity Aquifers, Texas

NASA Astrophysics Data System (ADS)

Smith, B. D.; Blome, C. D.; Clark, A. K.; Kress, W.; Smith, D. V.

2007-05-01

Airborne and ground geophysical surveys conducted in Uvalde, Medina, and northern Bexar counties, Texas, can be used to define and characterize hydrostratigraphic units of the Edwards and Trinity aquifers. Airborne magnetic surveys have defined numerous Cretaceous intrusive stocks and laccoliths, mainly in Uvalde County, that influence local hydrology and perhaps regional ground-water flow paths. Depositional environments in the aquifers can be classified as shallow water platforms (San Marcos Platform, Edwards Group), shoal and reef facies (Devils River Trend, Devils River Formation), and deeper water basins (Maverick Basin, West Nueces, McKnight, and Salmon Peak Formations). Detailed airborne and ground electromagnetic surveys have been conducted over the Edwards aquifer catchment zone (exposed Trinity aquifer rocks), recharge zone (exposed Edwards aquifer rocks), and artesian zone (confined Edwards) in the Seco Creek area (northeast Uvalde and Medina Counties; Devils River Trend). These geophysical survey data have been used to divide the Edwards exposed within the Balcones fault zone into upper and lower hydrostratigraphic units. Although both units are high electrical resistivity, the upper unit has slightly lower resistivity than the lower unit. The Georgetown Formation, at the top of the Edwards Group has a moderate resistivity. The formations that comprise the upper confining units to the Edwards aquifer rocks have varying resistivities. The Eagleford and Del Rio Groups (mainly clays) have very low resistivities and are excellent electrical marker beds in the Seco Creek area. The Buda Limestone is characterized by high resistivities. Moderate resistivities characterize the Austin Group rocks (mainly chalk). The older Trinity aquifer, underlying the Edwards aquifer rocks, is characterized by less limestone (electrically resistive or low conductivity units) and greater quantities of mudstones (electrically conductive or low resistivity units). In the western area (Devils River Trend and Maverick Basin) of the Trinity aquifer system there are well-defined collapse units and features that are marked by moderate resistivities bracketed by resistive limestone and conductive mudstone of the Glen Rose Limestone. In the central part of the aquifer (San Marcos Platform) the Trinity's lithologies are divided into upper and lower units with further subdivisions into hydrostratigraphic units. These hydrostratigraphic units are well mapped by an airborne electromagnetic survey in Bexar County. Electrical properties of the Edwards aquifer also vary across the fresh-saline water interface where ground and borehole electrical surveys have been conducted. The saline- saturated Edwards is predictably more conductive than the fresh-water saturated rocks. Similar fresh-saline water interfaces exist within the upper confining units of the Edwards aquifer (Carrizo-Wilcox aquifer) and the Trinity aquifer rocks.

Water-chemistry and chloride fluctuations in the Upper Floridan Aquifer in the Port Royal Sound area, South Carolina, 1917-93

USGS Publications Warehouse

Landmeyer, J.E.; Belval, D.L.

1996-01-01

Withdrawal of water from the Upper Floridan aquifer south of Port Royal Sound in Beaufort and Jasper Counties, South Carolina, has lowered water levels and reversed the hydraulic gradient beneath Hilton Head Island, South Carolina. Ground water that had previously discharged at the Sound is now being deflected southwest, toward withdrawals located near the city of Savannah, Georgia, and the island of Hilton Head. The reversal of this hydraulic gradient and the decline of water levels have caused saltwater in the Upper Floridan aquifer north of Port Royal Sound to begin moving southwest, toward water-supply wells for the town of Hilton Head and toward industries pumping ground water near Savannah. Analytical results from ground-water samples collected from wells in the Upper Floridan aquifer beneath and adjacent to Port Royal Sound show two plumes in the aquifer with chloride concentrations above the drinking- water standard. One plume of high chloride concentration extends slightly south of the theoretical predevelopment location of the steady- state freshwater-saltwater interface as indicated by numerical modeling. The other plume is present beneath the town of Port Royal, where the upper confining unit above the Upper Floridan aquifer is thin or absent. In these areas, the decline in water levels caused by ground-water withdrawals may have made it possible for water from tidal creeks to enter the Upper Floridan aquifer. Many wells completed in the upper permeable zone of the Upper Floridan aquifer show a distinct specific- conductance profile. One non-producing, monitoring well on Hilton Head Island (BFT-1810) was selected to depict a worst-case scenario to examine the short- and long-term water-chemistry and chloride fluctuations in the aquifer. Specific conductance was monitored at depths of 170, 190, and 200 feet below the top of the well casing. The specific conductance measured in 1987 ranged from approximately 450 microsiemens per centimeter near the top of the Upper Floridan aquifer to 1,500 microsiemens per centimeter near the lower, less permeable zone. Short-term fluctuations in conductance were measured at each probe and were found to be related to water-level fluctuations in the well caused by tidal cycles. The conductance varied regularly up to 100 microsiemens per centimeter, with an increasing time lag between high and low tides and low and high specific conductance for progressively shallower depths. Well BFT-1810 was monitored for specific conductance and water levels from October 1987 through September 1993. Specific conductance at the 170-foot probe showed little long-term change, while the 190- and the 200-foot probes showed long-term increases to approximately 4,000 and 10,000 microsiemens per centimeter, respectively. This well is located closest to one of the two plumes of saltwater delineated in the Upper Floridan aquifer, and the long-term chloride increases are a result of the movement of saltwater in the Upper Floridan aquifer toward Hilton Head Island under the influence of regional ground-water withdrawals.

8. Generator Barrel and Shaft of Unit 1, view to ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

8. Generator Barrel and Shaft of Unit 1, view to the northwest, with turbine shaft and thrust bearing visible in upper center of photograph. - Washington Water Power Clark Fork River Noxon Rapids Hydroelectric Development, Powerhouse, South bank of Clark Fork River at Noxon Rapids, Noxon, Sanders County, MT

Permafrost and Subsurface Ice in the Solar System

NASA Technical Reports Server (NTRS)

Anderson, D. M.

1985-01-01

The properties and behavior of planetary permafrost are discussed with reference to the ability of such surfaces to sustain loads characteristics of spacecraft landing and planetary bases. In most occurrences, water ice is in close proximity to, or in contact with, finely divided silicate mineral matter. When ice contacts silicate mineral surfaces, a liquid-like, transition zone is created. Its thickness ranges from several hundred Angstron units at temperatures near 0 degrees C to about three Angstrom units at -150 degrees C. When soluble substances are present, the resulting brine enlarges the interfacial zone. When clays are involved, although the interfacial zone may be small, its extent is large. The unfrozen, interfacial water may amount to 100% or more weight at a temperature of -5 degrees C. The presence of this interfacial unfrozen water acts to confer plasticity to permafrost, enabling it to exhibit creep at all imposed levels of stress. Nucleation processes and load-bearing capacity are examined.

The Spar Lake strata-Bound Cu-Ag deposit formed across a mixing zone between trapped natural gas and metals-bearing brine

USGS Publications Warehouse

Hayes, Timothy S.; Landis, Gary P.; Whelan, Joseph F.; Rye, Robert O.; Moscati, Richard J.

2012-01-01

Ore formation at the Spar Lake red bed-associated strata-bound Cu deposit took place across a mixing and reaction zone between a hot oxidized metals-transporting brine and a reservoir of “sour” (H2S-bearing) natural gas trapped in the host sandstones. Fluid inclusion volatile analyses have very high CH4 concentrations (≥1 mol % in most samples), and a sample from the fringe of the deposit has between 18 and 36 mol % CH4. The ratio of CH4/CO2 in fluid inclusions appears to vary regularly across the deposit, with the lowest CH4/CO2 ratios from high-grade chalcocite-bearing ore, and the highest from the chalcopyrite-bearing fringe. The helium R/Ra isotope ratios (0.23–0.98) and concentrations define a mixture between crustal and atmospheric helium. The volatiles in fluid inclusions (CH4, CO2, H2S, SO2, H2, H2O, and other organic gases) and values of fO2 and temperature calculated from the volatiles data all show gradations across the deposit that are completely consistent with such a mixing and reaction zone. Other volatiles from the fluid inclusions (HCl, HF, 3He, Msup>4He, N2, Ar) characterize the brine and give evidence for only shallow crustal fluids with no magmatic influences. The brine entered the gas reservoir from below and along the axis of the deposit and migrated out along bedding to the southwest, northeast, and northwest. Metals-transporting brines may have been fed into the host sandstones from the East Fault, but that remains uncertain. Abundant ore-stage Fe and Mn calcite cements from the reduced fringe have δ13C values as low as −18.4‰, and many values less than −10‰, which indicate that significant carbonate was generated by oxidation of organic carbon from the natural gas. The zone of calcite cements with very low δ13C values approximately envelopes chalcocite-bearing ore. Sulfur isotope data of Cu, Pb, and Fe sulfides and barite indicate derivation of roughly half of the orebody sulfide directly from sour gas H2S. That sour gas H2S had developed in steps known from other sedimentary basins, starting with (1) bacterial sulfate reduction (BSR) of seawater sulfate having δ34S of about 20‰ and sequestering of the sulfide in organic matter in source rocks stratigraphically below the deposit host rocks, followed by (2) maturation of the sulfide-bearing organic matter into liquid petroleum with relatively homogeneous sulfide having δ34S of 5 ± 5‰, then by (3) thermal cracking of the oil to CH4 and H2S with relatively homogeneous sulfide having δ34S closely distributed, about 6‰. The CH4 and H2S migrated and were trapped in sandstones of the upper member of the Revett Formation, where they were later met by the 200°C metals-transporting brine. There was additional contribution of sulfide to ore from later thermochemical sulfate reduction (TSR) operating on sulfate δ34S of 20 to 29‰ in both formation waters and metals-transporting solutions. A large range of δ34S in sulfides resulted as the 6‰ sour gas sulfide was supplemented with varying proportions of 20 to 29‰ sulfide from TSR.

Results of borehole geophysical logging and aquifer-isolation tests conducted in the John Wagner and Sons, Inc. former production well, Ivyland, Pennsylvania

USGS Publications Warehouse

Sloto, Ronald A.

1997-01-01

A suite of borehole geophysical logs and heat-pulse-flowmeter measurements run in the former production well at the John Wagner and Sons, Inc. plant indicate two zones of borehole flow. In the upper part of the well, water enters the borehole through a fracture at 90 ft (feet) below floor level, moves upward, and exits the borehole through a fracture at 72 ft below floor level. Water also enters the borehole through fractures at 205-213, 235, and 357 ft below floor level; moves downward; and exits the borehole through fractures at 450-459, 468-470, and 483-490 ft below floor level. Five zones were selected for aquifer-isolation (packer) tests on the basis of borehole geophysical logs. The zones were isolated using a straddle-packer assembly. The lowermost three zones (below 248, 223 to 248, and 198 to 223 ft below floor level) were hydraulically isolated from zones above and below. Specific capacities were 0.12, 0.034, and 0.15 gallons per minute per foot, respectively. The hydrograph from zone 2 (223 to 248 ft below floor level) showed interference from a nearby pumping well. For the upper two zones (81 to 106 and 57 to 81 ft below floor level), similar drawdowns in the isolated zone and the zones above and below the isolated zone indicate that these fractures are hydraulically connected outside the borehole in the unconfined part of the Stockton Formation. The specific capacity of zones 4 and 5 are similar—0.82 and 0.61, respectively.

Review of metamorphic and kinematic data from Internal Crystalline Massifs (Western Alps): PTt paths and exhumation history

NASA Astrophysics Data System (ADS)

Gasco, Ivano; Gattiglio, Marco; Borghi, Alessandro

2013-01-01

Detailed geological mapping combined with micro-structural and petrological investigation allowed to clarify the tectono-metamorphic relationships between continental and oceanic units transition in the Penninic domain of the Western Alps. The three study areas (Gressoney, Orco and Susa sections) take into consideration the same structural level across the axial metamorphic belt of the Western Italian Alps, i.e., a geological section across the Internal Crystalline Massifs vs Piedmont Zone boundary. The units outcropping in these areas can be grouped into two Tectonic Elements according to their tectono-metamorphic evolution. The Lower Tectonic Element (LTE) consists of the Internal Crystalline Massifs and the Lower Piedmont Zone (Zermatt-Saas like units), both showing well preserved eclogite facies relics. Instead, the Upper Tectonic Element (UTE) consists of the Upper Piedmont Zone (Combin like units) lacking evidence of eclogite facies relics. In the Lower Tectonic Element two main Alpine tectono-metamorphic stages were identified: M1/D1 developed under eclogite facies conditions and M2/D2 is related to the development of the regional foliation under greenschist to epidote-albite amphibolite facies conditions. In the Upper Tectonic Element the metamorphic stage M1/D1 developed under bluschist to greenschist facies conditions and M2/D2 stage under greenschist facies conditions. These two Tectonic Elements are separated by a tectonic contact of regional importance generally developed along the boundary between the Lower and the Upper Piedmont zone under greenschist facies conditions. PT data compared to geochronology indicate that the first exhumation of ICM can be explained by buoyancy forces acting along the subduction channel that occurred during the tectonic coupling between the continental and oceanic eclogite units. These buoyancy forces vanished at the base of the crust where the density difference between the subducted crustal units and the surroundings rocks is too low. A stage where compression prevails on the previous exhumation followed, which leads to the development of the regional foliation under greenschist to amphibolite facies metamorphic conditions. Further exhumation occurred after the M2/D2 stage at shallower crustal levels along conjugated shear zones leading to the development of a composite axial dome consisting of eclogite-bearing continental-oceanic units (ICM and Zermatt-Saas Zones) beneath greenschist ones (Combin Zone).

Stress concentration on Intraplate Seismicity: Numerical Modeling of Slab-released Fluids in the New Madrid Seismic Zone

NASA Astrophysics Data System (ADS)

Saxena, A.; Choi, E.; Powell, C. A.

2017-12-01

The mechanism behind the seismicity of the New Madrid Seismic Zone (NMSZ), the major intraplate earthquake source in the Central and Eastern US (CEUS), is still debated but new insights are being provided by recent tomographic studies involving USArray. A high-resolution tomography study by Nyamwandha et al. (2016) in the NMSZ indicates the presence of low (3 % - 5 %) upper mantle Vp and Vs anomalies in the depth range 100 to 250 km. The elevated anomaly magnitudes are difficult to explain by temperature alone. As the low-velocity anomalies beneath the northeast China are attributed to fluids released from the stagnant Pacific slab, water released from the stagnant Laramide Slab, presently located at transition zone depths beneath the CEUS might be contributing to the low velocity features in this region's upper mantle. Here, we investigate the potential impact of the slab-released fluids on the stresses at seismogenic depths using numerical modeling. We convert the tomographic results into temperature field under various assumed values of spatially uniform water content. In more realistic cases, water content is added only when the converted temperature exceeds the melting temperature of olivine. Viscosities are then computed based on the temperature and water content and given to our geodynamic models created by Pylith, an open source software for crustal dynamics. The model results show that increasing water content weakens the upper mantle more than temperature alone and thus elevates the differential stress in the upper crust. These results can better explain the tomography results and seismicity without invoking melting. We also invert the tomography results for volume fraction of orthopyroxene and temperature and compare the resultant stresses with those for pure olivine. To enhance the reproducibility, selected models in this study will be made available in the form of sharable and reproducible packages enabled by EarthCube Building block project, GeoTrust.

Effect of deforestation on stream water chemistry in the Skrzyczne massif (the Beskid Śląski Mountains in southern Poland).

PubMed

Kosmowska, Amanda; Żelazny, Mirosław; Małek, Stanisław; Siwek, Joanna Paulina; Jelonkiewicz, Łukasz

2016-10-15

The purpose of the study was to identify the factors affecting stream water chemistry in the small mountain catchments deforested to varying degrees, from 98.7 to 14.1%, due to long-term acid deposition. Water samples were collected monthly in 2013 and 2014 from 17 streams flowing across three distinct elevation zones in the Skrzyczne massif (Poland): Upper, Middle and Lower Forest Zone. Chemical and physical analyses, including the pH, electrical conductivity (EC), total mineral content (Mt), water temperature, and the concentrations of Ca(2+), Mg(2+), Na(+), K(+), HCO3(-), SO4(2-), Cl(-), and NO3(-), were conducted. Based on Principal Component Analysis (PCA), the most important factor affecting water chemistry was human impact associated with changes in pH, SO4(2-) concentration, and the concentration of most of the main ions. The substantial acidity of the studied environment contributed to the exclusion of natural factors, associated with changes in discharge, from the list of major factors revealed by PCA. All of the streams were characterized by very low EC, Mt, and low concentrations of the main ions such as Ca(2+) and HCO3(-). This is the effect of continuous leaching of solutes from the soils by acidic precipitation. The lowest parameter values were measured for the streams situated in the Upper Forest Zone, which is associated with greater acid deposition at the higher elevations. In the streams located in the Upper Forest Zone, a higher percentage of SO4(2-) occurred than in the streams situated in the Middle and Lower Forest Zones. However, the largest share of SO4(2-) was measured in the most deforested catchment. The saturation of the studied deforested catchment with sulfur compounds is reflected by a positive correlation between SO4(2-) and discharge. Hence, a forest acts as a natural buffer that limits the level of acidity in the natural environment caused by acidic atmospheric deposition. Copyright © 2016 Elsevier B.V. All rights reserved.

Geochemical features of the ore-bearing medium in uranium deposits in the Khiagda ore field

NASA Astrophysics Data System (ADS)

Kochkin, B. T.; Solodov, I. N.; Ganina, N. I.; Rekun, M. L.; Tarasov, N. N.; Shugina, G. A.; Shulik, L. S.

2017-09-01

The Neogene uranium deposits of the Khiagda ore field (KOF) belong to the paleovalley variety of the hydrogene type and differ from other deposits of this genetic type in the geological and geochemical localization conditions. The contemporary hydrogeochemical setting and microbiological composition of ore-bearing medium are discussed. The redox potential of the medium (Eh is as low as-400 mV) is much lower than those established at other hydrogenic deposits, both ancient Late Mesozoic and young Late Alpine, studied with the same methods in Russia, Uzbekistan, and southern Kazakhstan. The pH of subsurface water (6.86-8.13) differs in significant fluctuations both between neighboring deposits and within individual ore lodes. Hydrogen-forming and denitrifying bacteria are predominant in microbiological populations, whereas sulfate-reducing bacteria are low-active. The consideration of these factors allowed us to describe the mechanism of uranium ore conservation as resulting from the development of the cryolithic zone, which isolates ore lodes from the effect of the external medium. Carbonated water supplied from the basement along fault zones also participates in the formation of the present-day hydrogeochemical setting. Based on the features of the ore-bearing medium, we propose a method of borehole in situ acid leaching to increase the efficiency of mining in the Khiagda ore field.

Summary of well construction, testing, and preliminary findings from the Alligator Alley test well, Broward County, Florida

USGS Publications Warehouse

Meyer, F.W.

1988-01-01

A 2,811-foot deep test well was drilled during 1980 in The Everglades along Alligator Alley as part of the Floridan Regional Aquifer Systems Analysis project. The well was cased 895 feet deep. Hydraulic packers were used to isolate selected zones in the open hole for water samples and measurement of water levels. The well penetrated the surficial and intermediate aquifers into the Floridan aquifer system. The top of the Floridan aquifer system occurs at 770 feet and includes limestone ranging in age from Oligocene to early Eocene. About 67 percent of the total thickness of the Floridan aquifer system was penetrated by the well. The chief water-producing zones in the Floridan aquifer system occur at about 1,030 feet and at about 2,560 feet. The 1,030-foot zone contains brackish artesian groundwater, and the 2,560-foot zone contains salty artesian groundwater similar in composition to seawater. The static water geothermal gradient is indicated, and radiocarbon activities suggest that the saltwater in the lower zone is younger than brackish groundwater in the upper zone. (USGS)

Borehole Geophysical Logging of Water-Supply Wells in the Piedmont, Blue Ridge, and Valley and Ridge, Georgia

USGS Publications Warehouse

,

2007-01-01

Crystalline and carbonate-rock aquifers in northern Georgia provide water to an ever-increasing number of private and public wells in the region. Understanding the depth and yield of water-bearing zones in such wells is crucial for the development and long-term sustainability of ground-water resources and for keeping wells in good operating condition. Portable geophysical logging units are now widely available and have greatly increased the ability of geoscientists to obtain subsurface information from water wells.

Hydrogeology of the surficial and intermediate aquifer systems in Sarasota and adjacent counties, Florida

USGS Publications Warehouse

Barr, G.L.

1996-01-01

From 1991 to 1995, the hydrogeology of the surficial aquifer system and the major permeable zones and confining units of the intermediate aquifer system in southwest Florida was studied. The study area is a 1,400-square-mile area that includes Sarasota County and parts of Manatee, De Soto, Charlotte, and Lee Counties. Lithologic, geophysical, hydraulic property, and water-level data were used to correlate the hydrogeology and map the extent of the aquifer systems. Water chemistry was evaluated in southwest Sarasota County to determine salinity of the surficial and intermediate aquifer systems. The surficial aquifer is an unconfined aquifer system that overlies the intermediate aquifer system and ranges from a few feet to over 60 feet in thickness in the study area. Hydraulic properties of the surficial aquifer system determined from aquifer and laboratory tests, and model simulations vary considerably across the study area. The intermediate aquifer system, a confined aquifer system that lies between the surficial and the Upper Floridan aquifers, is composed of alternating confining units and permeable zones. The intermediate aquifer system has three major permeable zones that exhibit a wide range of hydraulic properties. Horizontal flow in the intermediate aquifer system is northeast to southwest. Most of the study area is in a discharge area of the intermediate aquifer system. Water ranges naturally from fresh in the surficial aquifer system and upper permeable zones of the intermediate aquifer system to moderately saline in the lower permeable zone. Water-quality data collected in coastal southwest Sarasota County indicate that ground-water withdrawals from major pumping centers have resulted in lateral seawater intrusion and upconing into the surficial and intermediate aquifer systems.

Brittle deformation during Alpine basal accretion and the origin of seismicity nests above the subduction interface

NASA Astrophysics Data System (ADS)

Menant, Armel; Angiboust, Samuel; Monié, Patrick; Oncken, Onno; Guigner, Jean-Michel

2018-04-01

Geophysical observations on active subduction zones have evidenced high seismicity clusters at 20-40 km depth in the fore-arc region whose origin remains controversial. We report here field observations of pervasive pseudotachylyte networks (interpreted as evidence for paleo-seismicity) in the now-exhumed Valpelline continental unit (Dent Blanche complex, NW. Alps, Italy), a tectonic sliver accreted to the upper plate at c. 30 km depth during the Paleocene Alpine subduction. Pre-alpine granulite-facies paragneiss from the core of the Valpelline unit are crosscut by widespread, mm to cm-thick pseudotachylyte veins. Co-seismic heating and subsequent cooling led to the formation of Ti-rich garnet rims, ilmenite needles, Ca-rich plagioclase, biotite microliths and hercynite micro-crystals. 39Ar-40Ar dating yields a 51-54 Ma age range for these veins, thus suggesting that frictional melting events occurred near peak burial conditions while the Valpelline unit was already inserted inside the duplex structure. In contrast, the base of the Valpelline unit underwent synchronous ductile and brittle, seismic deformation under water-bearing conditions followed by a re-equilibration at c. 40 Ma (39Ar-40Ar on retrograded pseudotachylyte veins) during exhumation-related deformation. Calculated rheological profiles suggest that pseudotachylyte veins from the dry core of the granulite unit record upper plate micro-seismicity (Mw 2-3) formed under very high differential stresses (>500 MPa) while the sheared base of the unit underwent repeated brittle-ductile deformation at much lower differential stresses (<40 MPa) in a fluid-saturated environment. These results demonstrate that some of the seismicity clusters nested along and above the plate interface may reflect the presence of stiff tectonic slivers rheologically analogous to the Valpelline unit acting as repeatedly breaking asperities in the basal accretion region of active subduction zones.

Gas exchange in the ice zone: the role of small waves and big animals

NASA Astrophysics Data System (ADS)

Loose, B.; Takahashi, A.; Bigdeli, A.

2016-12-01

The balance of air-sea gas exchange and net biological carbon fixation determine the transport and transformation of carbon dioxide and methane in the ocean. Air-sea gas exchange is mostly driven by upper ocean physics, but biology can also play a role. In the open ocean, gas exchange increases proportionate to the square of wind speed. When sea ice is present, this dependence breaks down in part because breaking waves and air bubble entrainment are damped out by interactions between sea ice and the wave field. At the same time, sea ice motions, formation, melt, and even sea ice-associated organisms can act to introduce turbulence and air bubbles into the upper ocean, thereby enhancing air-sea gas exchange. We take advantage of the knowledge advances of upper ocean physics including bubble dynamics to formulate a model for air-sea gas exchange in the sea ice zone. Here, we use the model to examine the role of small-scale waves and diving animals that trap air for insulation, including penguins, seals and polar bears. We compare these processes to existing parameterizations of wave and bubble dynamics in the open ocean, to observe how sea ice both mitigates and locally enhances air-sea gas transfer.

Sequence stratigraphy of the Hith/Upper Arab formations offshore Abu Dhabi, U.A.E.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azer, S.R.; Peebles, R.G.

1995-11-01

The Kimmeridgian Upper Arab zones A, B, and C, are prolific hydrocarbon bearing reservoirs in central and western Offshore Abu Dhabi (OAD). They were deposited in an arid climate which dominated the Arabian peninsula during Late Jurassic times. The Berriasian to Tithonian Hith Formation which overlies the Arab reservoirs constitute the cap rock, which just to the east of central OAD gradually pinches out and forms a N-S feather edge. The Hith and Upper Arab zones A, B, and C form 450 to over 600 feet of massive to interbedded anhydrites with varying proportions of limestones and dolomites in centralmore » and western OAD. The Arab Formation in OAD is a major regressive unit which was deposited on a broad carbonate platform and prograded eastwards into an open marine shelf environment. The objectives of this paper are to develop a sequence stratigraphic framework, emphasizing cyclicity, facies architecture and diagenesis. Core and well log data geared with various inorganic geochemical analyses from four wells are used to constrain the current uncertainties in age dating and integrate the diagenetic signatures in the patterns of relative sea level change which considerably control the formation of those parasequences. This effort will help in better understanding and possible prediction of porosity in such prospective reservoirs.« less

Mars Landing + 50 Years: Repurposing the First Viking Landing Site on Chryse Planitia as an Exploration Zone for Automated Infrastructure Construction

NASA Astrophysics Data System (ADS)

Farrell, K. W.

2015-10-01

The proposed Chryse Planitia EZ centered near the VL-1 landing site has evidence for adequate water ice, silica, and load-bearing bedrock surface resources to utilize as infrastructure for long-term missions to support humans.

Global Ocean Phytoplankton

NASA Technical Reports Server (NTRS)

Franz, B. A.; Behrenfeld, M. J.; Siegel, D. A.; Werdell, P. J.

2013-01-01

Phytoplankton are free-floating algae that grow in the euphotic zone of the upper ocean, converting carbon dioxide, sunlight, and available nutrients into organic carbon through photosynthesis. Despite their microscopic size, these photoautotrophs are responsible for roughly half the net primary production on Earth (NPP; gross primary production minus respiration), fixing atmospheric CO2 into food that fuels our global ocean ecosystems. Phytoplankton thus play a critical role in the global carbon cycle, and their growth patterns are highly sensitive to environmental changes such as increased ocean temperatures that stratify the water column and prohibit the transfer of cold, nutrient richwaters to the upper ocean euphotic zone.

Silicic magma differentiation in ascent conduits. Experimental constraints

NASA Astrophysics Data System (ADS)

Rodríguez, Carmen; Castro, Antonio

2017-02-01

Crystallization of water-bearing silicic magmas in a dynamic thermal boundary layer is reproduced experimentally by using the intrinsic thermal gradient of piston-cylinder assemblies. The standard AGV2 andesite under water-undersaturated conditions is set to crystallize in a dynamic thermal gradient of about 35 °C/mm in 10 mm length capsules. In the hotter area of the capsule, the temperature is initially set at 1200 °C and decreases by programmed cooling at two distinct rates of 0.6 and 9.6 °C/h. Experiments are conducted in horizontally arranged assemblies in a piston cylinder apparatus to avoid any effect of gravity settling and compaction of crystals in long duration runs. The results are conclusive about the effect of water-rich fluids that are expelled out the crystal-rich zone (mush), where water saturation is reached by second boiling in the interstitial liquid. Expelled fluids migrate to the magma ahead of the solidification front contributing to a progressive enrichment in the fluxed components SiO2, K2O and H2O. The composition of water-rich fluids is modelled by mass balance using the chemical composition of glasses (quenched melt). The results are the basis for a model of granite magma differentiation in thermally-zoned conduits with application of in-situ crystallization equations. The intriguing textural and compositional features of the typical autoliths, accompanying granodiorite-tonalite batholiths, can be explained following the results of this study, by critical phenomena leading to splitting of an initially homogeneous magma into two magma systems with sharp boundaries. Magma splitting in thermal boundary layers, formed at the margins of ascent conduits, may operate for several km distances during magma transport from deep sources at the lower crust or upper mantle. Accordingly, conduits may work as chromatographic columns contributing to increase the silica content of ascending magmas and, at the same time, leave behind residual mushes that eventually are dragged as enclaves or autoliths.

Hydrogeology and groundwater quality of Highlands County, Florida

USGS Publications Warehouse

Spechler, Rick M.

2010-01-01

Groundwater is the main source of water supply in Highlands County, Florida. As the demand for water in the county increases, additional information about local groundwater resources is needed to manage and develop the water supply effectively. To address the need for additional data, a study was conducted to evaluate the hydrogeology and groundwater quality of Highlands County. Total groundwater use in Highlands County has increased steadily since 1965. Total groundwater withdrawals increased from about 37 million gallons per day in 1965 to about 107 million gallons per day in 2005. Much of this increase in water use is related to agricultural activities, especially citrus cultivation, which increased more than 300 percent from 1965 to 2005. Highlands County is underlain by three principal hydrogeologic units. The uppermost water-bearing unit is the surficial aquifer, which is underlain by the intermediate aquifer system/intermediate confining unit. The lowermost hydrogeologic unit is the Floridan aquifer system, which consists of the Upper Floridan aquifer, as many as three middle confining units, and the Lower Floridan aquifer. The surficial aquifer consists primarily of fine-to-medium grained quartz sand with varying amounts of clay and silt. The aquifer system is unconfined and underlies the entire county. The thickness of the surficial aquifer is highly variable, ranging from less than 50 to more than 300 feet. Groundwater in the surficial aquifer is recharged primarily by precipitation, but also by septic tanks, irrigation from wells, seepage from lakes and streams, and the lateral groundwater inflow from adjacent areas. The intermediate aquifer system/intermediate confining unit acts as a confining layer (except where breached by sinkholes) that restricts the vertical movement of water between the surficial aquifer and the underlying Upper Floridan aquifer. The sediments have varying degrees of permeability and consist of permeable limestone, dolostone, or sand, or relatively impermeable layers of clay, clayey sand, or clayey carbonates. The thickness of the intermediate aquifer system/ intermediate confining unit ranges from about 200 feet in northwestern Highlands County to more than 600 feet in the southwestern part. Although the intermediate aquifer system is present in the county, it is unclear where the aquifer system grades into a confining unit in the eastern part of the county. Up to two water-bearing units are present in the intermediate aquifer system within the county. The lateral continuity and water-bearing potential of the various aquifers within the intermediate aquifer system are highly variable. The Floridan aquifer system is composed of a thick sequence of limestone and dolostone of Upper Paleocene to Oligocene age. The top of the aquifer system ranges from less than 200 feet below NGVD 29 in extreme northwestern Highlands County to more than 600 feet below NGVD 29 in the southwestern part. The principal source of groundwater supply in the county is the Upper Floridan aquifer. As of 2005, about 89 percent of the groundwater withdrawn from the county was obtained from this aquifer, mostly for agricultural irrigation and public supply. Over most of Highlands County, the Upper Floridan aquifer generally contains freshwater, and the Lower Floridan aquifer contains more mineralized water. The potentiometric surface of the Upper Floridan aquifer is constantly fluctuating, mainly in response to seasonal variations in rainfall and groundwater withdrawals. The potentiometric surface of the Upper Floridan aquifer in May 2007, which represents the hydrologic conditions near the end of the dry season when water levels generally are near their lowest, ranged from about 79 feet above NGVD 29 in northwestern Highlands County to about 40 feet above NGVD 29 in the southeastern part of the county. The potentiometric surface of the Upper Floridan aquifer in September 2007 was about 3 to 10 feet high

Saltwater movement in the upper Floridan aquifer beneath Port Royal Sound, South Carolina

USGS Publications Warehouse

Smith, Barry S.

1994-01-01

Freshwater for Hilton Head Island, South Carolina, is supplied by withdrawals from the Upper Floridan aquifer. Freshwater for the nearby city of Savannah, Georgia, and for the industry that has grown adjacent to the city, has also been supplied, in part, by withdrawal from the Upper Floridan aquifer since 1885. The withdrawal of ground water has caused water levels in the Upper Floridan aquifer to decline over a broad area, forming a cone of depression in the potentiometric surface of the aquifer centered near Savannah. In 1984, the cone of depression extended beneath Hilton Head Island as far as Port Royal Sound. Flow in the aquifer, which had previously been toward Port Royal Sound, has been reversed, and, as a result, saltwater in the aquifer beneath Port Royal Sound has begun to move toward Hilton Head Island. The Saturated-Unsaturated Transport (SUTRA) model of the U.S. Geological Survey was used for the simulation of density-dependent ground-water flow and solute transport for a vertical section of the Upper Floridan aquifer and upper confining unit beneath Hilton Head Island and Port Royal Sound. The model simulated a dynamic equilibrium between the flow of seawater and freshwater in the aquifer near the Gyben-Herzberg position estimated for the period before withdrawals began in 1885; it simulated reasonable movements of brackish water and saltwater from that position to the position determined by chemical analyses of samples withdrawn from the aquifer in 1984, and it approximated hydraulic heads measured in the aquifer in 1976 and 1984. The solute-transport simulations indicate that the transition zone would continue to move toward Hilton Head Island even if pumping ceased on the island. Increases in existing withdrawals or additional withdrawals on or near Hilton Head Island would accelerate movement of the transition zone toward the island, but reduction in withdrawals or the injection of freshwater would slow movement toward the island, according to the simulations. Future movements of the transition zone toward Hilton Head Island will depend on hydraulic gradients in the aquifer beneath the island and the sound. Hydraulic gradients in the Upper Floridan aquifer beneath Hilton Head Island and Port Royal Sound are strongly influenced by withdrawals on the island and near Savannah. Since 1984, withdrawals on Hilton Head Island have increased.

Applications of ISES for coastal zone studies

NASA Technical Reports Server (NTRS)

Bartlett, D. S.

1990-01-01

In contrast to the discipline- and process-oriented topics addressed, coastal zone studies are defined geographically by the special circumstances inherent in the interface between land and water. The characteristics of coastal zones which make them worthy of separate consideration are: (1) the dynamic nature of natural and anthropogenic processes taking place; (2) the relatively restricted spatial domain of the narrow land/water interface; and (3) the large proportion of the Earth's population living within coastal zones, and the resulting extreme pressure on natural and human resources. These characteristics place special constraints and priorities on remote sensing applications, even though the applications themselves bear close relation to those addressed by other elements of this report (e.g., oceans, ice, vegetation/land use). The discussion which follows first describes the suite of remote sensing activities relevant to coastal zone studies. Potential Information Sciences Experiment System (ISES) experiments will then be addressed within two general categories: applications of real-time data transmission and applications of onboard data acquisition and processing.

Determination of diffusivities in the Rustler Formation from exploratory-shaft construction at the Waste Isolation Pilot Plant in southeastern New Mexico

USGS Publications Warehouse

Stevens, Ken; Beyeler, Walt

1985-01-01

The construction of an exploratory shaft 12 feet in diameter into the Salado Formation (repository horizon for transuranic waste material) at the Waste Isolation Pilot Plant site in southeastern New Mexico affected water-levels in water-bearing zones above the repository horizon. By reading the construction history of the exploratory shaft, an approximation of construction-generated hydraulic stresses at the shaft was made. The magnitude of the construction-generated stresses was calibrated using the hydrographs from one hydrologic test pad. Whereas flow rates from the Magenta Dolomite and Culebra Dolomite Members in the Rustler Formation into the exploratory shaft were unknown, the ratio of transmissivity to storage (diffusivity) was determined by mathematically simulating the aquifers and the hydrologic stresses with flood-wave-response digital model. These results indicate that the Magenta Dolomite and Culebra Dolomite Members of the Rustler Formation can be modeled as homogeneous, isotropic, and confined water-bearing zones. One simple and consistent explanation, but by no means the only explanation, of the lack of a single diffusivity value in the Culebra aquifer is that the open-hole observation wells at the hydrologic test pads dampen the amplitude of water-level changes. (USGS)

Geohydrology of Big Bear Valley, California: phase 1--geologic framework, recharge, and preliminary assessment of the source and age of groundwater

USGS Publications Warehouse

Flint, Lorraine E.; Brandt, Justin; Christensen, Allen H.; Flint, Alan L.; Hevesi, Joseph A.; Jachens, Robert; Kulongoski, Justin T.; Martin, Peter; Sneed, Michelle

2012-01-01

The Big Bear Valley, located in the San Bernardino Mountains of southern California, has increased in population in recent years. Most of the water supply for the area is pumped from the alluvial deposits that form the Big Bear Valley groundwater basin. This study was conducted to better understand the thickness and structure of the groundwater basin in order to estimate the quantity and distribution of natural recharge to Big Bear Valley. A gravity survey was used to estimate the thickness of the alluvial deposits that form the Big Bear Valley groundwater basin. This determined that the alluvial deposits reach a maximum thickness of 1,500 to 2,000 feet beneath the center of Big Bear Lake and the area between Big Bear and Baldwin Lakes, and decrease to less than 500 feet thick beneath the eastern end of Big Bear Lake. Interferometric Synthetic Aperture Radar (InSAR) was used to measure pumping-induced land subsidence and to locate structures, such as faults, that could affect groundwater movement. The measurements indicated small amounts of land deformation (uplift and subsidence) in the area between Big Bear Lake and Baldwin Lake, the area near the city of Big Bear Lake, and the area near Sugarloaf, California. Both the gravity and InSAR measurements indicated the possible presence of subsurface faults in subbasins between Big Bear and Baldwin Lakes, but additional data are required for confirmation. The distribution and quantity of groundwater recharge in the area were evaluated by using a regional water-balance model (Basin Characterization Model, or BCM) and a daily rainfall-runoff model (INFILv3). The BCM calculated spatially distributed potential recharge in the study area of approximately 12,700 acre-feet per year (acre-ft/yr) of potential in-place recharge and 30,800 acre-ft/yr of potential runoff. Using the assumption that only 10 percent of the runoff becomes recharge, this approach indicated there is approximately 15,800 acre-ft/yr of total recharge in Big Bear Valley. The INFILv3 model was modified for this study to include a perched zone beneath the root zone to better simulate lateral seepage and recharge in the shallow subsurface in mountainous terrain. The climate input used in the INFILv3 model was developed by using daily climate data from 84 National Climatic Data Center stations and published Parameter Regression on Independent Slopes Model (PRISM) average monthly precipitation maps to match the drier average monthly precipitation measured in the Baldwin Lake drainage basin. This model resulted in a good representation of localized rain-shadow effects and calibrated well to measured lake volumes at Big Bear and Baldwin Lakes. The simulated average annual recharge was about 5,480 acre-ft/yr in the Big Bear study area, with about 2,800 acre-ft/yr in the Big Bear Lake surface-water drainage basin and about 2,680 acre-ft/yr in the Baldwin Lake surface-water drainage basin. One spring and eight wells were sampled and analyzed for chemical and isotopic data in 2005 and 2006 to determine if isotopic techniques could be used to assess the sources and ages of groundwater in the Big Bear Valley. This approach showed that the predominant source of recharge to the Big Bear Valley is winter precipitation falling on the surrounding mountains. The tritium and uncorrected carbon-14 ages of samples collected from wells for this study indicated that the groundwater basin contains water of different ages, ranging from modern to about 17,200-years old.The results of these investigations provide an understanding of the lateral and vertical extent of the groundwater basin, the spatial distribution of groundwater recharge, the processes responsible for the recharge, and the source and age of groundwater in the groundwater basin. Although the studies do not provide an understanding of the detailed water-bearing properties necessary to determine the groundwater availability of the basin, they do provide a framework for the future development of a groundwater model that would help to improve the understanding of the potential hydrologic effects of water-management alternatives in Big Bear Valley.

Ground-water recharge and flowpaths near the edge of the Decorah-Platteville-Glenwood confining unit, Rochester, Minnesota

USGS Publications Warehouse

Lindgren, Richard J.

2001-01-01

The water withdrawn by pumped wells or discharged to Bear Creek is derived predominantly from areal recharge near the edge of the Decorah-Platteville-Glenwood confining unit (0.47 ft3/s), rather than from water that has leaked downward through the Decorah unit (0.03 ft3/s). Model simulated discharge through springs and seeps in the lower part of the upper carbonate aquifer (0.21 ft3/s) represents a potential source of water to the St. Peter-Prairie du Chien-Jordan aquifer.

Topographical Variation of Human Femoral Articular Cartilage Thickness, T1rho and T2 Relaxation Times Is Related to Local Loading during Walking.

PubMed

Van Rossom, Sam; Wesseling, Mariska; Van Assche, Dieter; Jonkers, Ilse

2018-01-01

Objective Early detection of degenerative changes in the cartilage matrix composition is essential for evaluating early interventions that slow down osteoarthritis (OA) initiation. T1rho and T2 relaxation times were found to be effective for detecting early changes in proteoglycan and collagen content. To use these magnetic resonance imaging (MRI) methods, it is important to document the topographical variation in cartilage thickness, T1rho and T2 relaxation times in a healthy population. As OA is partially mechanically driven, the relation between these MRI-based parameters and localized mechanical loading during walking was investigated. Design MR images were acquired in 14 healthy adults and cartilage thickness and T1rho and T2 relaxation times were determined. Experimental gait data was collected and processed using musculoskeletal modeling to identify weight-bearing zones and estimate the contact force impulse during gait. Variation of the cartilage properties (i.e., thickness, T1rho, and T2) over the femoral cartilage was analyzed and compared between the weight-bearing and non-weight-bearing zone of the medial and lateral condyle as well as the trochlea. Results Medial condyle cartilage thickness was correlated to the contact force impulse ( r = 0.78). Lower T1rho, indicating increased proteoglycan content, was found in the medial weight-bearing zone. T2 was higher in all weight-bearing zones compared with the non-weight-bearing zones, indicating lower relative collagen content. Conclusions The current results suggest that medial condyle cartilage is adapted as a long-term protective response to localized loading during a frequently performed task and that the weight-bearing zone of the medial condyle has superior weight bearing capacities compared with the non-weight-bearing zones.

Freshwater-saltwater transition zone movement during aquifer storage and recovery cycles in Brooklyn and Queens, New York City, USA

USGS Publications Warehouse

Misut, P.E.; Voss, C.I.

2007-01-01

Freshwater storage in deep aquifers of Brooklyn and Queens, New York, USA, is under consideration as an emergency water supply for New York City. The purpose of a New York City storage and recovery system is to provide an emergency water supply during times of drought or other contingencies and would entail longer-term storage phases than a typical annual cycle. There is concern amongst neighboring coastal communities that such a system would adversely impact their local water supplies via increased saltwater intrusion. This analysis uses three-dimensional modeling of variable-density ground-water flow and salt transport to study conditions under which hypothetical aquifer storage and recovery (ASR) may not adversely impact the coastal water supplies. A range of storage, pause, and recovery phase lengths and ASR cycle repetitions were used to test scenarios that emphasize control of potential saltwater intrusion. The USGS SUTRA code was used to simulate movement of the freshwater-saltwater transition zones in a detailed model of the upper glacial, Jameco, Magothy, and Lloyd aquifers of western Long Island, New York. Simulated transition zones in the upper glacial, Jameco, and Magothy aquifers reach a steady state for 1999 stress and recharge conditions within 1 ka; however, saltwater encroachment is ongoing in the Lloyd (deepest) aquifer, for which the effects of the rise in sea level since deglaciation on transition zone equilibration are retarded by many ka due to the thick, overlying Raritan confining unit. Pumping in the 20th century has also caused widening and landward movement of the Lloyd aquifer transition zone. Simulation of scenarios of freshwater storage by injection followed by phases of pause and recovery by extraction indicates that the effect of net storage when less water is recovered than injected is to set up a hydraulic saltwater intrusion barrier in the Lloyd aquifer which may have beneficial effects to coastal water users. ?? 2007 Elsevier B.V. All rights reserved.

Freshwater saltwater transition zone movement during aquifer storage and recovery cycles in Brooklyn and Queens, New York City, USA

NASA Astrophysics Data System (ADS)

Misut, Paul E.; Voss, Clifford I.

2007-04-01

SummaryFreshwater storage in deep aquifers of Brooklyn and Queens, New York, USA, is under consideration as an emergency water supply for New York City. The purpose of a New York City storage and recovery system is to provide an emergency water supply during times of drought or other contingencies and would entail longer-term storage phases than a typical annual cycle. There is concern amongst neighboring coastal communities that such a system would adversely impact their local water supplies via increased saltwater intrusion. This analysis uses three-dimensional modeling of variable-density ground-water flow and salt transport to study conditions under which hypothetical aquifer storage and recovery (ASR) may not adversely impact the coastal water supplies. A range of storage, pause, and recovery phase lengths and ASR cycle repetitions were used to test scenarios that emphasize control of potential saltwater intrusion. The USGS SUTRA code was used to simulate movement of the freshwater-saltwater transition zones in a detailed model of the upper glacial, Jameco, Magothy, and Lloyd aquifers of western Long Island, New York. Simulated transition zones in the upper glacial, Jameco, and Magothy aquifers reach a steady state for 1999 stress and recharge conditions within 1 ka; however, saltwater encroachment is ongoing in the Lloyd (deepest) aquifer, for which the effects of the rise in sea level since deglaciation on transition zone equilibration are retarded by many ka due to the thick, overlying Raritan confining unit. Pumping in the 20th century has also caused widening and landward movement of the Lloyd aquifer transition zone. Simulation of scenarios of freshwater storage by injection followed by phases of pause and recovery by extraction indicates that the effect of net storage when less water is recovered than injected is to set up a hydraulic saltwater intrusion barrier in the Lloyd aquifer which may have beneficial effects to coastal water users.

75 FR 22620 - Upper Klamath, Lower Klamath, Tule Lake, Bear Valley, and Clear Lake National Wildlife Refuges...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-29

.... In addition to outlining broad management direction on conserving wildlife and their habitats, CCPs... ensure the best possible approach to wildlife, plant, and habitat conservation, while providing for... hardstem-cattail marsh and open water, along with 30 acres of forested uplands. These habitats serve as...

The surficial aquifer in east-central St Johns County, Florida

USGS Publications Warehouse

Hayes, Eugene C.

1981-01-01

The surficial aquifer, a composite of confined and unconfined water-bearing zones overlying the Miocene Hawthorn Formation, is an important source of water in St. Johns County, Fla. The water from wells open to the surficial aquifer generally meets quality standards recommended by the U.S. Environmental Protection Agency for public water supplies, except for concentrations of iron that for most wells are substantially greater than the recommended limit of 0.3 milligrams per liter. Data from 12 test wells drilled to the top of the Hawthorn formation, about 100 feet below land surface, indicate that the productive zones and confining beds in the surficial aquifer are discontinuous. Test well yields from individual zones range from less than 1 to 42 gallons per minute from depths between 20 and 100 feet below land surface. The most productive zones were generally found in the Tillman Ridge area, about 10 square miles in the west-central part of the area of investigation. Analysis of an aquifer test on a well in the Tillman Ridge area indicates a transmissivity of about 6,500 to 7,000 feet squared per day. The best local source of good quality water for development of a relatively large water supply is in the vicinity of Tillman Ridge. (USGS)

Three-Dimensional Distribution of Larval Fish Habitats in the Shallow Oxygen Minimum Zone in the Eastern Tropical Pacific Ocean off Mexico

NASA Astrophysics Data System (ADS)

Davies, S.; Sanchez Velasco, L.; Beier, E.; Godinez, V. M.; Barton, E. D.; Tamayo, A.

2016-02-01

Three-dimensional distribution of larval fish habitats was analyzed, from the upper limit of the shallow oxygen minimum zone ( 0.2 mL/L) to the sea surface, in the eastern tropical Pacific Ocean off Mexico in February 2010.The upper limit rises from 250 m depth in the entrance of the Gulf of California to 80 m depth off Cabo Corrientes. Three larval fish habitats were defined statistically: (i) a Gulf of California habitat dominated by Anchoa spp. larvae (epipelagic species), constrained to the oxygenated surface layer (>3.5 mL/L) in and above the thermocline ( 60 m depth), and separated by a salinity front from the Tropical Pacific habitat; (ii) a Tropical Pacific habitat, dominated by Vinciguerria lucetia larvae (mesopelagic species), located throughout the sampled water column, but with the highest abundance in the oxygenated upper layer above the thermocline; (iii) an Oxygen Minimum habitat defined mostly below the thermocline in hypoxic (<1 mL/L; 70 m depth) and anoxic (<0.2 mL/L; 80 m depth) water off Cabo Corrientes. This subsurface hypoxic habitat had the highest species richness and larval abundance, with dominance of Bregmaceros bathymaster, an endemic neritic pelagic species; which was an unexpected result. This maybe associated with the shoaling of the upper limit of the shallow oxygen minimum zone near the coast, a result of the strong costal upwelling detected by the Bakun Index. In this region of strong and semi-continuous coastal upwelling in the eastern tropical Pacific off Mexico, the shallow hypoxic water does not have dramatic effects on the total larval fish abundance but appears to affect species composition.

Paleoenvironmental model for the occurrence of vertebrate fossils in Carboniferous coal-bearing strata

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hook, R.W.

An interdisciplinary investigation was undertaken to identify the paleoenvironmental factors that governed the accumulation and preservation of a prolific Upper Carboniferous vertebrate assemblage known from a cannel coal underlying the Upper Freeport coal in the Diamond Coal Mine of Linton, Ohio. Stratigraphic data from previous work and field studies within an approximately 15 km radius of the fossil locality show that the channel occupies a 10 km long, north-northwest trending abandoned channel that occurs within a sandstone-dominated, fining-upwards fluvial sequence. Petrographic analysis of samples from eight sites along the course of the abandoned channel establishes that the cannel is composedmore » primarily of spores and very fine-grained micrinitic groundmass. Abundant primary pyrite and the absence of well-reserved humic materials suggest that the fossiliferous cannel originated as a sapropelic peat within a non-acidic anaerobic environment. Skeletal remains of animals are well preserved with little to no mineralogic alteration. Outside the abandoned channel in the Linton area and to the north, Upper Freeport coal averages 1 m in thickness. To the south, the Upper Freeport horizon is represented by interbedded flint clays and freshwater limestones. These sediment distribution patterns reflect the synsedimentary influence of the Transylvania Fault Zone, a previously documented, basement-controlled feature which trends east-west through the study area. Contemporaneous movement along this fault produced a topographic high in the Linton area which was locally entrenched by northward-flowing rivers. Upper Freeport swamps developed on this upthrown surface whereas carbonate lakes formed to the south of the fault zone in topographically lower areas.« less

Has irrigated water from Mahaweli River contributed to the kidney disease of uncertain etiology in the dry zone of Sri Lanka?

PubMed

Diyabalanage, Saranga; Abekoon, Sumith; Watanabe, Izumi; Watai, Chie; Ono, Yuko; Wijesekara, Saman; Guruge, Keerthi S; Chandrajith, Rohana

2016-06-01

The Mahaweli is the largest river basin in Sri Lanka that provides water to the dry zone region through multipurpose irrigation schemes . Selenium, arsenic, cadmium, and other bioimportant trace elements in surface waters of the upper Mahaweli River were measured using ICP-MS. Trace element levels were then compared with water from two other rivers (Maha Oya, Kalu Ganga) and from six dry zone irrigation reservoirs. Results showed that the trace metal concentrations in the Mahaweli upper catchment were detected in the order of Fe > Cu > Zn > Se > Cr > Mn > As > Ni > Co > Mo. Remarkably high levels of Ca, Cr, Co, Ni, Cu, As, and Se were observed in the Mahaweli Basin compared to other study rivers. Considerably high levels of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, and Se were found in upstream tributaries of the Mahaweli River. Such metals possibly originated from phosphate and organic fertilizers that are heavily applied for tea and vegetable cultivations within the drainage basin. Cadmium that is often attributed to the etiology of unknown chronic kidney diseases in certain parts of the dry zone is much lower than previously reported levels. Decrease in these metals in the lower part of the Mahaweli River could be due to adsorption of trace metals onto sediment and consequent deposition in reservoirs.

Theoretical investigation of the upper and lower bounds of a generalized dimensionless bearing health indicator

NASA Astrophysics Data System (ADS)

Wang, Dong; Tsui, Kwok-Leung

2018-01-01

Bearing-supported shafts are widely used in various machines. Due to harsh working environments, bearing performance degrades over time. To prevent unexpected bearing failures and accidents, bearing performance degradation assessment becomes an emerging topic in recent years. Bearing performance degradation assessment aims to evaluate the current health condition of a bearing through a bearing health indicator. In the past years, many signal processing and data mining based methods were proposed to construct bearing health indicators. However, the upper and lower bounds of these bearing health indicators were not theoretically calculated and they strongly depended on historical bearing data including normal and failure data. Besides, most health indicators are dimensional, which connotes that these health indicators are prone to be affected by varying operating conditions, such as varying speeds and loads. In this paper, based on the principle of squared envelope analysis, we focus on theoretical investigation of bearing performance degradation assessment in the case of additive Gaussian noises, including distribution establishment of squared envelope, construction of a generalized dimensionless bearing health indicator, and mathematical calculation of the upper and lower bounds of the generalized dimensionless bearing health indicator. Then, analyses of simulated and real bearing run to failure data are used as two case studies to illustrate how the generalized dimensionless health indicator works and demonstrate its effectiveness in bearing performance degradation assessment. Results show that squared envelope follows a noncentral chi-square distribution and the upper and lower bounds of the generalized dimensionless health indicator can be mathematically established. Moreover, the generalized dimensionless health indicator is sensitive to an incipient bearing defect in the process of bearing performance degradation.

Stratigraphic test well, Nantucket Island, Massachusetts

USGS Publications Warehouse

Folger, David W.; Hathaway, J.C.; Christopher, R.A.; Valentine, P.C.; Poag, C.W.

1978-01-01

The U.S. Geological Survey, in cooperation with the Massachusetts Water Resources Commission and the Nantucket Conservation Foundation, continuously cored 514 m of sediment and volcanic rock in a stratigraphic and water-quality test near the geographic center of Nantucket Island. Stratified sediments were divided texturally into three zones: the upper zone (0-128 m) contains mostly coarse sand and gravel; the middle zone (128-349 m) contains mostly silty clay and a few beds of sand and silt; and the lower zone (349-457 m) contains soft, unconsolidated, clayey sand. Below the lower zone, a saprolite, composed mostly of clay, grades abruptly downward at 470 m into partially altered basalt that extends to the bottom of the hole at 514 m. Calculations based on the Ghyben-Herzberg principle predicted a zone of freshwater 120-150 m thick. This principle is the theory of hydrostatic equilibrium between freshwater and more dense seawater in a coastal aquifer; it states that for each meter of ground-water elevation above sea level, the freshwater lens will depress the saltwater interface about 40 m below sea level. Freshwater or low-salinity brackish water was found in sediments far below the depth predicted by the Ghyben-Herzberg principle. These interstitial waters are probably relict ground water emplaced during times of low sea level during the Pleistocene. (Woodard-USGS)

Upper Illinois River basin

USGS Publications Warehouse

Friedel, Michael J.

1998-01-01

During the past 25 years, industry and government made large financial investments that resulted in better water quality across the Nation; however, many water-quality concerns remain. Following a 1986 pilot project, the U.S. Geological Survey began implementation of the National Water-Quality Assessment (NAWQA) Program in 1991. This program differs from other national water-quality assessment studies in that the NAWQA integrates monitoring of surface- and ground-water quality with the study of aquatic ecosystems. The goals of the NAWQA Program are to (1) describe current water-quality conditions for a large part of the Nation's freshwater streams and aquifers (water-bearing sediments and rocks), (2) describe how water quality is changing over time, and (3) improve our understanding of the primary natural and human factors affecting water quality.The Upper Illinois River Basin National Water- Quality Assessment (NAWQA) study will increase the scientific understanding of surface- and ground-water quality and the factors that affect water quality in the basin. The study also will provide information needed by water-resource managers to implement effective water-quality management actions and evaluate long-term changes in water quality.

Gas geochemistry studies at the gas hydrate occurrence in the permafrost environment of Mallik (NWT, Canada)

NASA Astrophysics Data System (ADS)

Wiersberg, T.; Erzinger, J.; Zimmer, M.; Schicks, J.; Dahms, E.; Mallik Working Group

2003-04-01

We present real-time mud gas monitoring data as well as results of noble gas and isotope investigations from the Mallik 2002 Production Research Well Program, an international research project on Gas Hydrates in the Northwest Territories of Canada. The program participants include 8 partners; The Geological Survey of Canada (GSC), The Japan National Oil Corporation (JNOC), GeoForschungsZentrum Potsdam (GFZ), United States Geological Survey (USGS), United States Department of the Energy (USDOE), India Ministry of Petroleum and Natural Gas (MOPNG)/Gas Authority of India (GAIL) and the Chevron-BP-Burlington joint venture group. Mud gas monitoring (extraction of gas dissolved in the drill mud followed by real-time analysis) revealed more or less complete gas depth profiles of Mallik 4L-38 and Mallik 5L-38 wells for N_2, O_2, Ar, He, CO_2, H_2, CH_4, C_2H_6, C_3H_8, C_4H10, and 222Rn; both wells are approx. 1150 m deep. Based on the molecular and and isotopic composition, hydrocarbons occurring at shallow depth (down to ˜400 m) are mostly of microbial origin. Below 400 m, the gas wetness parameter (CH_4/(C_2H_6 + C_3H_8)) and isotopes indicate mixing with thermogenic gas. Gas accumulation at the base of permafrost (˜650 m) as well as δ13C and helium isotopic data implies that the permafrost inhibits gas flux from below. Gas hydrate occurrence at Mallik is known in a depth between ˜890 m and 1100 m. The upper section of the hydrate bearing zone (890 m--920 m) consists predominantly of methane bearing gas hydrates. Between 920 m and 1050 m, concentration of C_2H_6, C_3H_8, and C_4H10 increases due to the occurrence of organic rich sediment layers. Below that interval, the gas composition is similar to the upper section of the hydrate zone. At the base of the hydrate bearing zone (˜1100 m), elevated helium and methane concentrations and their isotopic composition leads to the assumption that gas hydrates act as a barrier for gas migration from below. In mud gas samples from the hydrate zone, the concentrations of all noble gases are lower than in air. Using Ne as a tracer for air contamination, the air-normalized abundances of Ar, Ke and Xe in those samples increase with their mass. Non-atmospheric elemental ratios of the heavier noble gases are most possible the result of elemental fractionation during hydrate formation.

Mapping Ground Water in Three Dimensions - An Analysis of Airborne Geophysical Surveys of the Upper San Pedro River Basin, Cochise County, Southeastern Arizona

USGS Publications Warehouse

Wynn, Jeff

2006-01-01

This report summarizes the results of two airborne geophysical surveys conducted in the upper San Pedro Valley of southeastern Arizona in 1997 and 1999. The combined surveys cover about 1,000 square kilometers and extend from the Huachuca Mountains on the west to the Mule Mountains and Tombstone Hills on the east and from north of the Babocomari River to near the Mexican border on the south. The surveys included the acquisition of high-resolution magnetic data, which were used to map depth to the crystalline basement rocks underlying the sediments filling the basin. The magnetic inversion results show a complex basement morphology, with sediment thickness in the center of the valley ranging from ~237 meters beneath the city of Sierra Vista to ~1,500 meters beneath Huachuca City and the Palominas area near the Mexican border. The surveys also included acquisition of 60-channel time-domain electromagnetic (EM) data. Extensive quality analyses of these data, including inversion to conductivity vs. depth (conductivity-depth-transform or CDT) profiles and comparisons with electrical well logs, show that the electrical conductor mapped represents the subsurface water-bearing sediments throughout most of the basin. In a few places (notably the mouth of Huachuca Canyon), the reported water table lies above where the electrical conductor places it. These exceptions appear to be due to a combination of outdated water-table information, significant horizontal displacement between the wells and the CDT profiles, and a subtle calibration issue with the CDT algorithm apparent only in areas of highly resistive (very dry) overburden. These occasional disparities appear in less than 5 percent of the surveyed area. Observations show, however, that wells drilled in the thick unsaturated zone along the Huachuca Mountain front eventually intersect water, at which point the water rapidly rises high into the unsaturated zone within the wellbore. This rising of water in a wellbore implies some sort of confinement below the thick unsaturated zone, a confinement that is not identified in the available literature. Occasional disparities notwithstanding, maps of the electrical conductor derived from the airborne EM system provide a synoptic view of the presence of water underlying the upper San Pedro Valley, including its three-dimensional distribution. The EM data even show faults previously only inferred from geologic mapping. The magnetic and electromagnetic data together appear to show the thickness of the sediments, the water in the saturated sediments down to a maximum of about 400 meters depth, and even places where the main ground-water body is not in direct contact with the San Pedro River. However, the geophysical data cannot reveal anything directly about hydraulic conductivity or ground-water flow. Estimating these characteristics requires new hydraulic modeling based in part on this report. One concern to reviewers of this report is the effect that clays may have on the electrical conductor mapped with the airborne geophysical system. Although the water in the basin is unusually conductive, averaging 338 microsiemens per centimeter, reasoning cited below suggests that the contribution of clays to the overall conductivity would be relatively small. Basic principles of sedimentary geology suggest that silts and clays should dominate the center of the basin, while sands and gravels would tend to dominate the margins. Although clay content may increase the amplitude of the observed electrical conductors somewhat, it will not affect the depths to the conductor derived from depth inversions. Further, fine-grained sediments generally have higher porosity and tend to lie toward a basin center, a fact in general agreement with the observed geophysical data.

Acid precipitation: compositional changes during throughfall; soil water. Technical completion report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, R.

1984-12-01

Lysimeters were installed at two soil depths within each of the three major ecosystems on Camels Hump Mountain. Collections were made weekly during the frost-free season of 1982 and 1983. Samples were analyzed for pH, conductivity, and a broad range of metals, anionic and cationic constituents, and for other physical properties. The findings included: soil solutions obtained from the upper-elevations in a northern coniferous forest zone are significantly more acidic than those from the lower elevation hardwood forest zone; soil solutions for all ecological zones are more acidic in the spring during and shortly after snowmelt than they are latermore » in the frost free-season; aluminum in soil solutions from the upper elevations is present in concentrations known to be phytotoxic to seedlings of forest trees and to groundcover plants; cadmium, Pb, and Zn are, in the spring, present in concentrations that are close to being phytotoxic; there are changes in the ratios of divalent cations to specific metals during the season and as functions of altitude and forest zones; nitrate concentration in soil water are also elevation- and time dependent.« less

Multi-geophysical approaches to detect karst channels underground - A case study in Mengzi of Yunnan Province, China

NASA Astrophysics Data System (ADS)

Gan, Fuping; Han, Kai; Lan, Funing; Chen, Yuling; Zhang, Wei

2017-01-01

Mengzi locates in the south 20 km away from the outlet of Nandong subsurface river, and has been suffering from water deficiency in recent years. It is necessary to find out the water resources underground according to the geological characteristics such as the positions and buried depths of the underground river to improve the civil and industrial environments. Due to the adverse factors such as topographic relief, bare rocks in karst terrains, the geophysical approaches, such as Controlled Source Audio Magnetotellurics and Seismic Refraction Tomography, were used to roughly identify faults and fracture zones by the geophysical features of low resistivity and low velocity, and then used the mise-a-la-masse method to judge which faults and fracture zones should be the potential channels of the subsurface river. Five anomalies were recognized along the profile of 2.4 km long and showed that the northeast river system has several branches. Drilling data have proved that the first borehole indicated a water bearing channel by a characteristics of rock core of river sands and gravels deposition, the second one encountered water-filled fracture zone with abundant water, and the third one exposed mud-filled fracture zone without sustainable water. The results from this case study show that the combination of Controlled Source Audio Magnetotellurics, Seismic Refraction Tomography and mise-a-la-Masse is one of the effective methods to detect water-filled channels or fracture zones in karst terrains.

Localized sulfate-reducing zones in a coastal plain aquifer

USGS Publications Warehouse

Brown, C.J.; Coates, J.D.; Schoonen, M.A.A.

1999-01-01

High concentrations of dissolved iron in ground water of coastal plain or alluvial aquifers contribute to the biofouling of public supply wells for which treatment and remediation is costly. Many of these aquifers, however, contain zones in which microbial sulfate reduction and the associated precipitation of iron-sulfide minerals decreases iron mobility. The principal water-bearing aquifer (Magothy Aquifer of Cretaceous age) in Suffolk County, New York, contains localized sulfate-reducing zones in and near lignite deposits, which generally are associated with clay lenses. Microbial analyses of core samples amended with [14C]-acetate indicate that microbial sulfate reduction is the predominant terminal-electron-accepting process (TEAP) in poorly permeable, lignite-rich sediments at shallow depths and near the ground water divide. The sulfate-reducing zones are characterized by abundant lignite and iron-sulfide minerals, low concentrations of Fe(III) oxyhydroxides, and by proximity to clay lenses that contain pore water with relatively high concentrations of sulfate and dissolved organic carbon. The low permeability of these zones and, hence, the long residence time of ground water within them, permit the preservation and (or) allow the formation of iron-sulfide minerals, including pyrite and marcasite. Both sulfate-reducing bacteria (SRB) and iron-reducing bacteria (IRB) are present beneath and beyond the shallow sulfate-reducing zones. A unique Fe(III)-reducing organism, MD-612, was found in core sediments from a depth of 187 m near the southern shore of Long Island. The distribution of poorly permeable, lignite-rich, sulfate-reducing zones with decreased iron concentration is varied within the principal aquifer and accounts for the observed distribution of dissolved sulfate, iron, and iron sulfides in the aquifer. Locating such zones for the placement of production wells would be difficult, however, because these zones are of limited aerial extent.

Oreshoot zoning in the Carlin-type Betze orebody, Goldstrike Mine, Eureka County, Nevada

USGS Publications Warehouse

Peters, Stephen G.; Ferdock, Gregory C.; Woitsekhowskaya, Maria B.; Leonardson, Robert; Rahn, Jerry

1998-01-01

Field and laboratory investigations of the giant Betze gold orebody, the largest Carlin-type deposit known, in the north-central Carlin trend, Nevada document that the orebody is composed of individual high-grade oreshoots that contain different geologic, mineralogic, and textural characteristics. The orebody is typical of many structurally controlled Carlin-type deposits, and is hosted in thin-bedded, impure carbonate or limy siltstone, breccia bodies, and intrusive or calc-silicate rock. Most ores in the Betze orebody are highly sheared or brecciated and show evidence of syndeformational hydrothermal deposition. The interplay between rock types and pre- and syn-structural events accounts for most of the distribution and zoning of the oreshoots. Hydrothermal alteration is scale dependent, either in broad, pervasive alteration patterns, or in areas related to various oreshoots. Alteration includes decarbonatization (~decalcification) of carbonate units, argillization (illite-clay), and silicification. Patterns of alteration zoning in and surrounding the Betze orebody define a large porous, dilated volume of rock where high fluid flow predominated. Local restriction of alteration to narrow illite- and clay-rich selvages around unaltered marble or calc-silicate rock phacoids implies that fluid flow favored permeable structures and deformed zones. Gold mainly is present as disseminated sub-micron-sized particles, commonly associated with Asñrich pyrite, although one type of oreshoot contains micron-size free gold. Oreshoots form a three-dimensional zoning pattern in the orebody within a WNW-striking structural zone of shearing and shear folding, termed the Dillon deformation zone (DDZ). Main types of oreshoots are: (1) rutile-bearing siliceous oreshoots; (2) illite-clay-pyrite oreshoots; (3) realgar- and orpiment-bearing oreshoots; (4) stibnite-bearing siliceous oreshoots; and (5) polymetallic oreshoots. Zoning patterns result from paragenetically early development of illite-clay-pyrite oreshoots during movement along the DDZ, and subsequent silicification and brecciation, associated with formation of the realgar- and orpiment-bearing, and stibnite-bearing oreshoots. Additional shear movement along the DDZ followed. Polymetallic oreshoots, which contain minerals rich in Hg, Cu, Zn, Ag, and native Au, were the last ores to form and overprint most earlier oreshoots. Ore textures, gouge, phyllonitic rock, alteration style, and previously documented isotopic and fluid-inclusion data, all indicate a weakly to moderately saline fluid that ascended and cooled during structural displacements. Changing conditions, due to water-wall rock reactions and P-T changes during deformation, are probably responsible for fluid variation that resulted in zoning of the different oreshoots during dynamic interaction of the Au-bearing fluid with the wall rock. This investigation indicates that isolated As-, Sb-, and Hg-rich ores are separate parts of a larger single gold system. This large gold system was contemporaneous with post-Jurassic brittle-ductile deformation, on the basis of deformed mineralized pods of the Jurassic Goldstrike pluton, and large-scale hydrothermal flow, and together they appear to be an integral part of the formation of some Carlin-type gold deposits in north-central Nevada.

Tertiary coals in South Texas: Anomalous cannel-like coals of Webb County (Claiborne Group, Eocene) and lignites of Atascosa County (Jackson Group, Eocene) - Geologic setting, character, source-rock and coal-bed methane potential

USGS Publications Warehouse

Warwick, Peter D.; Aubourg, Claire E.; Willett, Jason C.

1999-01-01

The coal-bearing Gulf of Mexico Coastal Plain of North America contains a variety of depositional settings and coal types. The coal-bearing region extends westward from Alabama and Mississippi, across Louisiana to the northern part of the Mississippi Embayment, and then southward to eastern Arkansas, Texas and northern Mexico (fig. 1). Most of the coal currently mined in Texas is lignite from the upper part of the Wilcox Group (Paleocene-Eocene) and, in Louisiana, lignite is mined from the lower part of the Wilcox (fig. 2). Gulf Coast coal is used primarily as fuel for mine-mouth electric plants. On this field trip we will visit the only two non-Wilcox coal mining intervals in the Texas-Louisiana Coastal Plain; these include the San Pedro - Santo Tomas bituminous cannel-like coal zone of the Eocene Claiborne Group, and the San Miguel lignite coal zone of the Eocene Jackson Group (fig. 2). Other coal-mining areas in northern Mexico are currently producing bituminous coal from the Cretaceous Olmos Formation of the Navaro Group (fig. 2).

Retrogressive hydration of calc-silicate xenoliths in the eastern Bushveld complex: evidence for late magmatic fluid movement

NASA Astrophysics Data System (ADS)

Wallmach, T.; Hatton, C. J.; De Waal, S. A.; Gibson, R. L.

1995-11-01

Two calc-silicate xenoliths in the Upper Zone of the Bushveld complex contain mineral assemblages which permit delineation of the metamorphic path followed after incorporation of the xenoliths into the magma. Peak metamorphism in these xenoliths occurred at T=1100-1200°C and P <1.5 kbar. Retrograde metamorphism, probably coinciding with the late magmatic stage, is characterized by the breakdown of akermanite to monticellite and wollastonite at 700°C and the growth of vesuvianite from melilite. The latter implies that water-rich fluids (X CO 2 <0.2) were present and probably circulating through the cooling magmatic pile. In contrast, calc-silicate xenoliths within the lower zones of the Bushveld complex, namely in the Marginal and Critical Zones, also contain melilite, monticellite and additional periclase with only rare development of vesuvianite. This suggests that the Upper Zone cumulate pile was much 'wetter' in the late-magmatic stage than the earlier-formed Critical and Marginal Zone cumulate piles.

DIN retention-transport through four hydrologically connected zones in a headwater catchment of the Upper Mississippi River

USGS Publications Warehouse

Triska, F.J.; Duff, J.H.; Sheibley, R.W.; Jackman, A.P.; Avanzino, R.J.

2007-01-01

Dissolved inorganic nitrogen (DIN) retention-transport through a headwater catchment was synthesized from studies encompassing four distinct hydrologic zones of the Shingobee River Headwaters near the origin of the Mississippi River. The hydrologic zones included: (1) hillslope ground water (ridge to bankside riparian); (2) alluvial riparian ground water; (3) ground water discharged through subchannel sediments (hyporheic zone); and (4) channel surface water. During subsurface hillslope transport through Zone 1, DIN, primarily nitrate, decreased from ???3 mg-N/l to <0.1 mg-N/l. Ambient seasonal nitrate:chloride ratios in hillslope flow paths indicated both dilution and biotic processing caused nitrate loss. Biologically available organic carbon controlled biotic nitrate retention during hillslope transport. In the alluvial riparian zone (Zone 2) biologically available organic carbon controlled nitrate depletion although processing of both ambient and amended nitrate was faster during the summer than winter. In the hyporheic zone (Zone 3) and stream surface water (Zone 4) DIN retention was primarily controlled by temperature. Perfusion core studies using hyporheic sediment indicated sufficient organic carbon in bed sediments to retain ground water DIN via coupled nitrification-denitrification. Numerical simulations of seasonal hyporheic sediment nitrification-denitrification rates from perfusion cores adequately predicted surface water ammonium but not nitrate when compared to 5 years of monthly field data (1989-93). Mass balance studies in stream surface water indicated proportionally higher summer than winter N retention. Watershed DIN retention was effective during summer under the current land use of intermittently grazed pasture. However, more intensive land use such as row crop agriculture would decrease nitrate retention efficiency and increase loads to surface water. Understanding DIN retention capacity throughout the system, including special channel features such as sloughs, wetlands and floodplains that provide surface water-ground water connectivity, will be required to develop effective nitrate management strategies. ?? 2007 American Water Resources Association.

Lithostratigraphy, biostratigraphy and chemostratigraphy of Upper Cretaceous sediments from southern Tanzania: Tanzania drilling project sites 21-26

NASA Astrophysics Data System (ADS)

Jiménez Berrocoso, Álvaro; MacLeod, Kenneth G.; Huber, Brian T.; Lees, Jacqueline A.; Wendler, Ines; Bown, Paul R.; Mweneinda, Amina K.; Isaza Londoño, Carolina; Singano, Joyce M.

2010-04-01

The 2007 drilling season by the Tanzania drilling project (TDP) reveals a much more expanded Upper Cretaceous sequence than was recognized previously in the Lindi region of southern Tanzania. This TDP expedition targeted recovery of excellently preserved microfossils (foraminifera and calcareous nannofossils) for Late Cretaceous paleoclimatic, paleoceanographic and biostratigraphic studies. A total of 501.17 m of core was drilled at six Upper Cretaceous sites (TDP Sites 21, 22, 23, 24, 24B and 26) and a thin Miocene-Pleistocene section (TDP Site 25). Microfossil preservation at all these sites is good to excellent, with foraminifera often showing glassy shells and consistently good preservation of small and delicate nannofossil taxa. In addition to adding to our knowledge of the subsurface geology, new surface exposures were mapped and the geological map of the region is revised herein. TDP Sites 24, 24B and 26 collectively span the upper Albian to lower-middle Turonian (planktonic foraminiferal Planomalina buxtorfi- Whiteinella archaeocretacea Zones and calcareous nannofossil zones UC0a-UC8a). The bottom of TDP Site 21 is barren, but the rest of the section represents the uppermost Cenomanian-Coniacian ( W. archaeocretacea- Dicarinella concavata Zones and nannofossil zones UC5c-UC10). Bulk organic δ 13C data suggest recovery of part of Ocean Anoxic Event 2 (OAE2) from these four sites. In the upper part of this interval, the lower Turonian nannofossil zones UC6a-7 are characterized by a low-diversity nannoflora that may be related to OAE2 surface-water conditions. TDP Site 22 presents a 122-m-thick, lower-middle Turonian ( W. archaeocretacea- Helvetoglobotruncana helvetica Zones) sequence that includes the nannofossil zones UC6a(-7?), but invariable isotopic curves. Further, a lower to upper Campanian ( Globotruncana ventricosa- Radotruncana calcarata Zones and nannofossil subzones UC15b TP-UC15d TP) succession was drilled at TDP Site 23. Lithologies of the new sites include thin units of gray, medium to coarse sandstones, separating much thicker intervals of dark claystones with organic-rich laminated parts, irregular silty to fine sandstone partings, and rare inoceramid and ammonite debris. These lithofacies are interpreted to have been deposited in outer shelf and upper slope settings and indicate relatively stable sedimentary conditions during most of the Late Cretaceous on the Tanzanian margin.

El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

NASA Astrophysics Data System (ADS)

Arntz, W. E.; Gallardo, V. A.; Gutiérrez, D.; Isla, E.; Levin, L. A.; Mendo, J.; Neira, C.; Rowe, G. T.; Tarazona, J.; Wolff, M.

2006-03-01

To a certain degree, Eastern Boundary Current (EBC) ecosystems are similar: Cold bottom water from moderate depths, rich in nutrients, is transported to the euphotic zone by a combination of trade winds, Coriolis force and Ekman transport. The resultant high primary production fuels a rich secondary production in the upper pelagic and nearshore zones, but where O2 exchange is restricted, it creates oxygen minimum zones (OMZs) at shelf and upper slope (Humboldt and Benguela Current) or slope depths (California Current). These hypoxic zones host a specifically adapted, small macro- and meiofauna together with giant sulphur bacteria that use nitrate to oxydise H2S. In all EBC, small polychaetes, large nematodes and other opportunistic benthic species have adapted to the hypoxic conditions and co-exist with sulphur bacteria, which seem to be particularly dominant off Peru and Chile. However, a massive reduction of macrobenthos occurs in the core of the OMZ. In the Humboldt Current area the OMZ ranges between <100 and about 600 m, with decreasing thickness in a poleward direction. The OMZ merges into better oxygenated zones towards the deep sea, where large cold-water mega- and macrofauna occupy a dominant role as in the nearshore strip. The Benguela Current OMZ has a similar upper limit but remains shallower. It also hosts giant sulphur bacteria but little is known about the benthic fauna. However, sulphur eruptions and intense hypoxia might preclude the coexistence of significant mega- und macrobenthos. Conversely, off North America the upper limit of the OMZ is considerably deeper (e.g., 500-600 m off California and Oregon), and the lower boundary may exceed 1000m. The properties described are valid for very cold and cold (La Niña and "normal") ENSO conditions with effective upwelling of nutrient-rich bottom water. During warm (El Niño) episodes, warm water masses of low oxygen concentration from oceanic and equatorial regions enter the upwelling zones, bringing a variety of (sub)tropical immigrants. The autochthonous benthic fauna emigrates to deeper water or poleward, or suffers mortality. However, some local macrofaunal species experience important population proliferations, presumably due to improved oxygenation (in the southern hemisphere), higher temperature tolerance, reduced competition or the capability to use different food. Both these negative and positive effects of El Niño influence local artisanal fisheries and the livelihood of coastal populations. In the Humboldt Current system the hypoxic seafloor at outer shelf depths receives important flushing from the equatorial zone, causing havoc on the sulphur bacteria mats and immediate recolonisation of the sediments by mega- and macrofauna. Conversely, off California, the intruding equatorial water masses appear to have lower oxygen than ambient waters, and may cause oxygen deficiency at upper slope depths. Effects of this change have not been studied in detail, although shrimp and other taxa appear to alter their distribution on the continental margin. Other properties and reactions of the two Pacific EBC benthic ecosystems to El Niño seem to differ, too, as does the overall impact of major episodes (e.g., 1982/1983(1984) vs. 1997/1998). The relation of the "Benguela Niño" to ENSO seems unclear although many Pacific-Atlantic ocean and atmosphere teleconnections have been described. Warm, low-oxygen equatorial water seems to be transported into the upwelling area by similar mechanisms as in the Pacific, but most major impacts on the eukaryotic biota obviously come from other, independent perturbations such as an extreme eutrophication of the sediments ensuing in sulphidic eruptions and toxic algal blooms. Similarities and differences of the Humboldt and California Current benthic ecosystems are discussed with particular reference to ENSO impacts since 1972/73. Where there are data available, the authors include the Benguela Current ecosystem as another important, non-Pacific EBC, which also suffers from the effects of hypoxia.

Geohydrology of the near-surface unsaturated zone adjacent to the disposal site for low-level radioactive waste near Beatty, Nevada: A section in Safe disposal of radionuclides in low-level radioactive-waste repository sites; Low-level radioactive-waste disposal workshop, U.S. Geological Survey, July 11-16, 1987, Big Bear Lake, Calif., Proceedings (Circular 1036)

USGS Publications Warehouse

Fisher, Jeffrey M.; Bedinger, Marion S.; Stevens, Peter R.

1990-01-01

Shallow-land burial in arid areas is considered the best method for isolating low-level radioactive waste from the environment (Nichols and Goode, this report; Mercer and others, 1983). A major threat to waste isolation in shallow trenches is ground-water percolation. Repository sites in arid areas are believed to minimize the risk of ground-water contamination because such sites receive minimal precipitation and are underlain by thick unsaturated zones. Unfortunately, few data are available on rates of water percolation in an arid environment.

Simulation of saltwater movement in the Floridan aquifer system, Hilton Head Island, South Carolina

USGS Publications Warehouse

Bush, Peter W.

1988-01-01

Freshwater to supply Hilton Head Island, S.C., is obtained from the upper permeable zone of the Upper Floridan aquifer. Long-term pumping at Savannah, Ga., and the steadily increasing pumping on Hilton Head Island, have lowered Upper Floridan heads near the center of the island from about 10 feet above sea level to about 6 to 7 feet below sea level. The seaward hydraulic gradient that existed before pumping began has been reversed, thus increasing the potential for saltwater intrusion. Simulations of predevelopment, recent, and future ground-water flow in the Floridan aquifer system beneath the north end of Hilton Head Island and Port Royal Sound are presented. A finite-element model for fluid-density-dependent ground-water flow and solute transport was used in cross section. The general configuration of the simulated predevelopment flowfield is typical of a coastal aquifer having a seaward gradient in the freshwater. The freshwater flows toward Port Royal Sound over an intruding wedge of saltwater. The simulated flowfield at the end of 1983 shows that ground water in the Floridan aquifer system beneath most of Hilton Head Island has reversed its predevelopment direction and is moving toward Savannah. The distribution of chloride concentrations, based on simulation at the end of 1983, is about the same as the predevelopment distribution of chloride concentrations obtained from simulation. Results of two 50-year simulations from 1983 to 2034 suggest that there will be no significant threat of saltwater intrusion into the upper permeable zone of the Upper Floridan aquifer if heads on Hilton Head Island remain at current levels for the next 45 to 50 years. However, if head decline continues at the historical rate, any flow that presently occurs from the north end of the island toward Port Royal Sound will cease, allowing lateral intrusion of saltwater to proceed. Even under these conditions, chloride concentrations in the upper permeable zone of the Upper Floridan aquifer beneath Hilton Head Island should remain below 250 milligrams per liter for the next 45 to 50 years. Aquifer properties and selected boundary conditions were tested with several 1,000-year simulations which show that lateral permeability, transverse dispersivity, and landward boundary flow have the most influence on saltwater movement in the Upper Floridan aquifer.

Hydrogeological impacts of a railway tunnel in fractured Precambrian gneiss rocks (south-eastern Norway)

NASA Astrophysics Data System (ADS)

Kværner, Jens; Snilsberg, Petter

2013-11-01

Groundwater monitoring along the Romeriksporten tunnel, south-eastern Norway, provided an opportunity for studying the impacts of tunnelling on groundwater in fractured Precambrian gneiss rocks, and examining relations between bedrock hydrology, tectonic weakness zones and catchments. Tunnel leakage resulted in groundwater drawdown up to 35 m in weakness zones, converted groundwater discharge zones into recharge zones, and affected groundwater chemistry. The magnitude of drawdown and fluctuations in groundwater level differed between weakness zones, and varied with distance from the tunnel route, tunnel leakage, and recharge from catchments. Clear differences in groundwater level and fluctuation patterns indicated restricted groundwater flow between weakness zones. The groundwater drawdowns demonstrated coherent water-bearing networks to 180-m depth in faults and fracture zones. Similar groundwater levels with highly correlated fluctuations demonstrated hydraulic connectivity within fracture zones. Different groundwater drawdown and leakage in weakness zones with different appearance and influence of tectonic events demonstrated the importance of the geological history for bedrock hydrogeology. Water injection into the bedrock counteracted groundwater drawdowns. Even moderate leakage to underground constructions may lead to large groundwater drawdown in areas with small groundwater recharge. Hydrogeological interpretation of tectonic weakness zones should occur in the context of geological history and local catchment hydrology.

Inorganic nitrogen transformations in the bed of the Shingobee River, Minnesota: Integrating hydrologic and biological processes using sediment perfusion cores

USGS Publications Warehouse

Sheibley, R.W.; Duff, J.H.; Jackman, A.P.; Triska, F.J.

2003-01-01

Inorganic N transformations were examined in streambed sediments from the Shingobee River using sediment perfusion cores. The experimental design simulated groundwater-stream water mixing within sediment cores, which provided a well-defined one-dimensional representation of in situ hydrologic conditions. Two distinct hydrologic and chemical settings were preserved in the sediment cores: the lowermost sediments, perfused with groundwater, remained anaerobic during the incubations, whereas the uppermost sediments, perfused with oxic water pumped from the overlying water column, simulated stream water penetration into the bed. The maintenance of oxic and anoxic zones formed a biologically active aerobic-anaerobic interface. Ammonium (NH4+) dissolved in groundwater was transported conservatively through the lower core zone but was removed as it mixed with aerated recycle water. Concurrently, a small quantity of nitrate (NO3-) equaling ???25% of the NH4+ loss was produced in the upper sediments. The NH4+ and NO3- profiles in the uppermost sediments resulted from coupled nitrification-denitrification, because assimilation and sorption were negligible. We hypothesize that anaerobic microsites within the aerated upper sediments supported denitrification. Rates of nitrification and denitrification in the perfusion cores ranged 42-209 and 53-160 mg N m-2 day-1, respectively. The use of modified perfusion cores permitted the identification and quantification of N transformations and verified process control by surface water exchange into the shallow hyporheic zone of the Shingobee River.

Igneous layering in the peralkaline intrusions ,Kola Peninsula :leading role of gravitational differentiation

NASA Astrophysics Data System (ADS)

Kogarko, L. N..

2012-04-01

In the center of Kola Peninsula there are two large layered intrusions of agpaitic nepheline syenites - Khibina and Lovozero. . The Khibina alkaline massif (Kola Peninsula,Russia) hosts the world's largest and economically most important apatite deposit. The Khibina massif is a complex multiphase body built up from a number of ring-like and conical intrusions. The apatite bearing intrusion is ring-like and is represented by a layered body of ijolitic composition with a thickness of about 1 - 2 km. The upper zone is represented by different types of apatite ores. These rocks consist of 60-90% euhedral very small (tenths of mm)apatite crystals. The lower zone has mostly ijolitic composition. The lower zone grades into underlying massive urtite consisting of 75-90% large (several mm) euhedral nepheline. Our experimental studies of systems with apatite demonstrated the near-eutectic nature of the apatite-bearing intrusion, resulting in practically simultaneous crystallization of nepheline, apatite and pyroxene. The mathematical model of the formation of the layered apatite-bearing intrusion based on the processes of sedimentation under the conditions of steady state convection taking account of crystal sizes is proposed. Under the conditions of steady-state convection large crystals of nepheline continuously had been settling forming massive underlying urtite whereas smaller crystals of pyroxenes, nepheline and apatite had been stirred in the convecting melt. During the cooling the intensity of convection decreased causing a settling of smaller crystals of nepheline and pyroxene and later very small crystalls of apatite in the upper part of alkaline magma chamber. The Lovozero massif, the largest of the Globe layered peralkaline intrusion, comprises super-large rare-metal (Nb, Ta, REE) deposit. The main ore mineral is loparite (Na, Ce, Ca)2 (Ti, Nb)2O6 which was mined during many years. The composition of cumulus loparite changed systematically upward through the intrusion with an increase in Na, Sr, Nb, Th, Nb/Ta, U/Th and decrease in REE, Zr, V, Zn, Ba and Ti. Our investigation indicates that the formation of loparite ore was the result of several factors including the chemical evolution of highly alkaline magmatic system and mechanical accumulation of loparite at the base of convecting unit.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, S.M.; Smolensky, D.A.; Masterson, J.P.

A plume of contaminated ground water has been delineated within an 11.4-square-mile area in east-central Nassau County, where residential neighborhoods surround an area zoned for industrial use. The industrial zone contains several firms that, in the past, have discharged effluent containing volatile organic compounds into the upper glacial aquifer through onsite recharge basins. The upper glacial aquifer is in direct hydraulic connection with the underlying Magothy aquifer; the first continuous formation that impedes downward movement of ground water is the Raritan confining unit, which is more than 500 feet below sea level. The report documents the chemical quality of groundmore » water in and around the industrial area, identifies which VOCs have entered the ground-water system beneath the area of investigation, and includes maps that delineate the vertical and horizontal extent of the contaminant plumes. It also examines the effect of local stresses, such as pumping and recharge, on the distribution of contaminants and describes the various sources of contamination and the fate of the contaminants as they migrate offsite. Analyses of groundwater samples are presented in the appendixes.« less

Geohydrology and Potential for Upward Movement of Saline Water in the Cocoa Well Field, East Orange County, Florida

DTIC Science & Technology

1996-01-01

11 8. Map showing chloride concentration in water from the Upper...not move upward. Upconing of saline water probably is not taking place in the center and western part of the well field, based on the low vertical...zone of low hydraulic conductivity, based on the geophysical logs of well R (fig. 5). Chloride concentrations increase sharply in water from both

Selenium in the Blackfoot, Salt, and Bear River Watersheds

USGS Publications Warehouse

Hamilton, S.J.; Buhl, K.J.

2005-01-01

Nine stream sites in the Blackfoot River, Salt River, and Bear River watersheds in southeast Idaho, USA were sampled in May 2001 for water, surficial sediment, aquatic plants, aquatic invertebrates, and fish. Selenium was measured in these aquatic ecosystem components, and a hazard assessment was performed on the data. Water quality characteristics such as pH, hardness, and specific conductance were relatively uniform among the nine sites. Of the aquatic components assessed, water was the least contaminated with selenium because measured concentrations were below the national water quality criterion of 5 μ g/L at eight of the nine sites. In contrast, selenium was elevated in sediment, aquatic plants, aquatic invertebrates, and fish from several sites, suggesting deposition in sediments and food web cycling through plants and invertebrates. Selenium was elevated to concentrations of concern in fish at eight sites (> 4 μ g/g in whole body). A hazard assessment of selenium in the aquatic environment suggested a moderate hazard at upper Angus Creek (UAC) and Smoky Creek (SC), and high hazard at Little Blackfoot River (LiB), Blackfoot River gaging station (BGS), State Land Creek (SLC), upper (UGC) and lower Georgetown Creek (LGC), Deer Creek (DC), and Crow Creek (CC). The results of this study indicate that selenium concentrations from the phosphate mining area of southeast Idaho were sufficiently elevated in several ecosystem components to cause adverse effects to aquatic resources in southeastern Idaho.

Results of hydrologic tests and water-chemistry analyses, Wells H-6A, H-6B, and H-6C, at the proposed Waste Isolation Pilot Plant site, southeastern New Mexico

USGS Publications Warehouse

Dennehy, Kevin F.

1982-01-01

Hydrologic testing was conducted at 3 test wells in the northwestern part of the proposed Waste Isolation Pilot Plant site in southeastern New Mexico to define hydraulic properties of three water-bearing zones. The zones tested were the Magenta and Culebra Dolomite Members of the Rustler Formation and the Rustler Formation-Salado contact. The Rustler Formation and the contact yield water to wells at rates less than 0.5 gallon per minute as determined from shut-in and slug tests. These test methods were not applicable for the Culebra Dolomite Member of the Rustler Formation at well H-6B. A transmissivity value for the Culebra Dolomite Member was obtained by conducting a conventional pumping test. Well H-6B was pumped at a rate of approximately 11 gallons per minute. Throughout the testing of the Magenta Dolomite Member and the Rustler Salado contact, water-pressure response in the test zones were monitored by a pressure transducer system. Water samples from the Magenta Dolomite Member had a dissolved solids concentration of 5,760 milligrams per liter. The major chemical constituents of water samples from this zone were sulfate, sodium, and chloride. Water samples from the Culebra Dolomite Member and the Rustler-Salado contact had dissolved-solids concentrations of 52,600 and 316 ,000 milligrams per liter, respectively; chloride and sodium were the major constituents in the water samples. Radium-266, a naturally occurring radioactive element, was present in samples from all three zones. (USGS)

Numerical modeling the genetic mechanism of Cenozoic intraplate Volcanoes in Northeastern China

NASA Astrophysics Data System (ADS)

Qu, Wulin; Chen, Yongshun John; Zhang, Huai; Jin, Yimin; Shi, Yaolin

2017-04-01

Changbaishan Volcano located about 1400 km west of Japan Trench is an intra continental volcano which having different origin from island arc volcanoes. A number of different mechanisms have been proposed to interpret the origin of intraplate volcanoes, such as deep mantle plumes, back-arc extension and decompressional partial melting, asthenosphere upwelling and decompressional melting, and deep stagnant slab dehydration and partial melting. The recent geophysical research reveals that the slow seismic velocity anomaly extends continuously just below 660 km depth to surface beneath Changbaishan by seismic images and three-dimensional waveform modelling [Tang et al., 2014]. The subduction-induced upwelling occurs within a gap in the stagnant subducted Pacific Plate and produces decompressional melting. Water in deep Earth can reduce viscosity and lower melting temperature and seismic velocity and has effects on many other physical properties of mantle materials. The water-storage capacity of wadsleyite and ringwoodite, which are the main phase in the mantle transition zone, is much greater than that of upper mantle and lower mantle. Geophysical evidences have shown that water content in the mantle transition zone is exactly greater than that of upper mantle and lower mantle [Karato, 2011]. Subducted slab could make mantle transition zone with high water content upward or downward across main phase change surface to release water, and lead to partial melting. We infer that the partial melting mantle and subducted slab materials propagate upwards and form the Cenozoic intraplate Volcanoes in Northeastern China. We use the open source code ASPECT [Kronbichler et al., 2012] to simulate the formation and migration of magma contributing to Changbaishan Volcano. We find that the water entrained by subducted slab from surface has only small proportion comparing to water content of mantle transition zone. Our model provide insights into dehydration melting induced by water transport out of the mantle transition zone associated with dynamic interactions between the subducted slab and surrounding mantle. References Karato, S. (2011), Water distribution across the mantle transition zone and its implications for global material circulation, EARTH PLANET SC LETT, 301(3), 413-423. Kronbichler, M., et al. (2012), High accuracy mantle convection simulation through modern numerical methods, GEOPHYS J INT, 191(1), 12-29. Tang, Y., et al. (2014), Changbaishan volcanism in northeast China linked to subduction-induced mantle upwelling, NAT GEOSCI, 7(6), 470-475.

Results of hydrologic tests and water-chemistry analyses, wells H-5A, H-5B, and H-5C, at the proposed Waste Isolation Pilot Plant site, southeastern New Mexico

USGS Publications Warehouse

Dennehy, Kevin F.; Mercer, Jerry W.

1982-01-01

Data were collected during hydrologic testing at wells H-5A, H-5B, and H-5C in the northeastern part of the proposed Waste Isolation Pilot Plant site in southeastern New Mexico. The three water-bearing zones tested, the Magenta and Culebra Dolomite Members of the Rustler Formation and the Rustler Formation-Salado Formation contact, yield water to wells at rates less than 0.6 gallon per minute. Throughout the testing, water-pressure response in the tested zone was monitored by a pressure-transducer system. Shut-in and slug tests were conducted to acquire data. Water samples from the Magenta Dolomite Member, Culebra Dolomite Member, and Rustler Formation-Salado Formation contact had dissolved-solids concentrations of 6,090, 144,000, and 412,000 milligrams per liter, respectively. The major chemical constituents of water samples from the Magenta Dolomite Member were sodium and sulfate; from the Culebra Dolomite Member, sodium and chloride; and from the Rustler Formation-Salado Formation contact, magnesium, and chloride. Radium-226, a naturally occurring radioactive element, was present in samples from all three zones. (USGS)

Hydrogeology and the distribution of salinity in the Floridan Aquifer system, southwestern Florida

USGS Publications Warehouse

Reese, R.S.

2000-01-01

In most of the study area, the Floridan aquifer system can be divided into a brackish-water zone, a salinity transition zone, and a saline-water zone. The brackish-water zone contains water with a dissolved-solids concentration of less than 10,000 milligrams per liter. The saline-water zone has a dissolved-solids concentration of at least 35,000 milligrams per liter and a salinity similar to that of seawater. The salinity transition zone that separates these two zones is usually 150 feet or less in thickness. The altitude of the base of the brackish-water zone was mapped primarily using geophysical logs; it ranges from as shallow as 565 feet below sea level along the coast to almost 2,200 feet below sea level inland. This mapping indicated that the boundary represents a salinity interface, the depth of which is controlled by head in the brackish-water zone. Chloride concentrations in the upper part of the brackish-water zone range from 400 to 4,000 milligrams per liter. A large area of relatively low salinity in north-central Collier County and to the northwest, as defined by a 1,200-milligram-per-liter chloride-concentration line, coincides with a high area on the basal contact of the Hawthorn Group. As this contact dips away from this high area to central Hendry and southwestern Collier Counties, chloride concentration increases to 2,000 milligrams per liter or greater. However, the increase in salinity in these areas occurs only in the basal Hawthorn unit or Suwannee Limestone, but not in deeper units. In central Hendry County, the increase occurs only in the basal Hawthorn unit in an area where the unit is well developed and thick. These areas of higher salinity could have resulted from the influx of seawater from southwestern Collier County into zones of higher permeability in the Upper Floridan aquifer during high sea-level stands. The influx may only have occurred in structurally low areas and may have experienced incomplete flushing subsequently by the modern freshwater flow system. In an area in north-central Collier County, the altitude of the base of the brackish-water zone is anomalously deep given the position of this area relative to the coast. In this area, the base extends as deep as 2,090 feet below sea level, and the salinity transition zone is not present or is poorly defined. The origin of this anomalous area is interpreted to be related to the development of a unit containing thick dolomite and evaporite beds high in the middle confining unit of the Floridan aquifer system. The top of this dolomite-evaporite unit, which probably has very low permeability, occurs at the base of the brackish-water zone in this area. The axis of a high area mapped at the top of the unit trends to the northwest from central Collier County into north-central Lee County. This axis parallels and lies just to the west of the anomalous area, and it could have acted as an impermeable sill, preventing saline water from moving in laterally from the coast to the southwest and up from the Lower Floridan aquifer. Locating a Floridan aquifer system well field in or near this anomalous area could be optimal because of the lack of a salinity interface at depth.

Evaluation of ground-water flow and solute transport in the Lompoc area, Santa Barbara County, California

USGS Publications Warehouse

Bright, Daniel J.; Nash, David B.; Martin, Peter

1997-01-01

Ground-water quality in the Lompoc area, especially in the Lompoc plain, is only marginally acceptable for most uses. Demand for ground water has increased for municipal use since the late 1950's and has continued to be high for irrigation on the Lompoc plain, the principal agricultural area in the Santa Ynez River basin. As use has increased, the quality of ground water has deteriorated in some areas of the Lompoc plain. The dissolved-solids concentration in the main zone of the upper aquifer beneath most of the central and western plains has increased from less than 1,000 milligrams per liter in the 1940's to greater than 2,000 milligrams per liter in the 1960's. Dissolved- solids concentration have remained relatively constant since the 1960's. A three-dimensional finite-difference model was used to simulate ground-water flow in the Lompoc area and a two-dimensional finite-element model was used to simulate solute transport to gain a better understanding of the ground-water system and to evaluate the effects of proposed management plans for the ground-water basin. The aquifer system was simulated in the flow model as four horizontal layers. In the area of the Lompoc plain, the layers represent the shallow, middle, and main zones of the upper aquifer, and the lower aquifer. For the Lompoc upland and Lompoc terrace, the four layers represent the lower aquifer. The solute transport model was used to simulate dissolved-solids transport in the main zone of the upper aquifer beneath the Lompoc plain. The flow and solute-transport models were calibrated to transient conditions for 1941-88. A steady-state simulation was made to provide initial conditions for the transient-state simulation by using long-term average (1941-88) recharge rates. Model- simulated hydraulic heads generally were within 5 feet of measured heads in the main zone for transient conditions. Model-simulated dissolved- solids concentrations for the main zone generally differed less than 200milligrams per liter from concentrations in 1988. During 1941-88 about 1,096,000 acre-feet of water was pumped from the aquifer system. Average pumpage for this period (22,830 acre-feet per year) exceeded pumpage for the steady-state simulation by 16,590 acre-feet per year. The results of the transient simulation indicate that about 60 percent of this increase in pumpage was contributed by increased recharge, 28 percent by decreased natural discharge from the system (primarily discharge to the Santa Ynez River and transpiration), and 13 percent was withdrawn from storage. Total simulated downward leakage from the middle zone to the main zone in the central plain and upward leakage from the consolidated rocks to the main zone significantly increased in response to increased pumpage, which increased from about 6,240 to 30,870 acre-feet per year from 1941 to 1988. Average dissolved-solid concentration in the middle zone in 1987-88 ranged from 2,000 to 3,000 milligrams per liter beneath the northeastern plain and the dissolved-solids concentration of two samples from the consolidated rocks beneath the western plain averaged 4,300 milligrams per liter. Because the dissolved-solids concentration for the middle zone and the consolidated rocks is higher than the simulated steady-state dissolved-solids concentration of the main zone, the increase in the leakage from these two sources resulted in increased dissolved-solids concentration in the main zone during the transient period. The model results indicate that the main source of increased dissolved- solids concentration in the northeastern and central plains was downward leakage from the middle zone; whereas, upward leakage from the consolidated rocks was the main source of the increased dissolved-solids concentrations in the northwestern and western plains. The models were used to estimate changes in hydraulic head and in dissolved-solids concentration resulting from three proposed management alternatives: (1) average recharge

Dehydration-driven stress transfer triggers intermediate-depth earthquakes

NASA Astrophysics Data System (ADS)

Ferrand, Thomas P.; Hilairet, Nadège; Incel, Sarah; Deldicque, Damien; Labrousse, Loïc; Gasc, Julien; Renner, Joerg; Wang, Yanbin; Green, Harry W., II; Schubnel, Alexandre

2017-05-01

Intermediate-depth earthquakes (30-300 km) have been extensively documented within subducting oceanic slabs, but their mechanics remains enigmatic. Here we decipher the mechanism of these earthquakes by performing deformation experiments on dehydrating serpentinized peridotites (synthetic antigorite-olivine aggregates, minerals representative of subduction zones lithologies) at upper mantle conditions. At a pressure of 1.1 gigapascals, dehydration of deforming samples containing only 5 vol% of antigorite suffices to trigger acoustic emissions, a laboratory-scale analogue of earthquakes. At 3.5 gigapascals, acoustic emissions are recorded from samples with up to 50 vol% of antigorite. Experimentally produced faults, observed post-mortem, are sealed by fluid-bearing micro-pseudotachylytes. Microstructural observations demonstrate that antigorite dehydration triggered dynamic shear failure of the olivine load-bearing network. These laboratory analogues of intermediate-depth earthquakes demonstrate that little dehydration is required to trigger embrittlement. We propose an alternative model to dehydration-embrittlement in which dehydration-driven stress transfer, rather than fluid overpressure, causes embrittlement.

Origin Of Methane Gas And Migration Through The Gas Hydrate Stability Zone Beneath The Permafrost Zone

NASA Astrophysics Data System (ADS)

Uchida, T.; Waseda, A.; Namikawa, T.

2005-12-01

In 1998 and 2002 Mallik wells were drilled at Mackenzie Delta in the Canadian Arctic that clarified the characteristics of gas hydrate-dominant sandy layers at depths from 890 to 1110 m beneath the permafrost zone. Continuous downhole well log data as well as visible gas hydrates have confirmed pore-space hydrate as intergranular pore filling within sandy layers whose saturations are up to 80% in pore volume, but muddy sediments scarcely contain. Plenty of gas hydrate-bearing sand core samples have been obtained from the Mallik wells. According to grain size distributions pore-space hydrate is dominant in medium- to very fine-grained sandy strata. Methane gas accumulation and original pore space large enough to occur within host sediments may be required for forming highly saturated gas hydrate in pore system. The distribution of a porous and coarser-grained host rock should be one of the important factors to control the occurrence of gas hydrate, as well as physicochemical conditions. Subsequent analyses in sedimentology and geochemistry performed on gas hydrate-bearing sandy core samples also revealed important geologic and sedimentological controls on the formation and concentration of natural gas hydrate. This appears to be a similar mode for conventional oil and gas accumulations. It is necessary for investigating subsurface fluid flow behaviors to evaluate both porosity and permeability of gas hydrate-bearing sandy sediments, and the measurements of water permeability for them indicate that highly saturated sands may have permeability of a few millidarcies. The isotopic data of methane show that hydrocarbon gas contained in gas hydrate is generated by thermogenic decomposition of kerogen in deep mature sediments. Based on geochemical and geological data, methane is inferred to migrate upward closely associated with pore water hundreds of meters into and through the hydrate stability zone partly up to the permafrost zone and the surface along faults and permeable sandy pathways. It should be remarked that there are many similar features in appearance and characteristics between the terrestrial and deep marine areas such as Nankai Trough with observations of well-interconnected and highly saturated pore-space hydrate.

Studies on geological background and source of fluorine in drinking water in the North China Plate fluorosis areas

USGS Publications Warehouse

Luo, K.; Feng, F.; Li, H.; Chou, C.-L.; Feng, Z.; Yunshe, D.

2008-01-01

Endemic fluorosis in northern China is usually produced by high fluorine (F) content in drinking water. Thirty-one samples of drinking waters, mainly well waters and nearly 200 samples of rocks, loess, and coal were analyzed for F content using the combustion hydrolysis-fluoride-ion selective electrode (ISE) method. The geologic cross sections of two well-known fluorosis basins were studied. The solubility of F in different rock types collected from fluorosis areas was determined. Results showed that areas of endemic fluorosis in northern China are located in coal-bearing basins which are comprised of three stratagraphic portions. The lowest portion is Precambrian granitic rocks or Cambrian-Ordovician carbonates. The middle portion consists of Permo-Carboniferous or Jurassic coal-bearing sequences. The upper portion is 0-400 m Pleistocene loess. Flourine content in the Precambrian granite-gneiss contained (a) 1090-1460 ppm, in the Cambrian-Ordovician limestone and dolomite, (b) 52-133 ppm, in black shales and coal gob of Permo-Carboniferous coal-bearing strata, (c) 200-700 ppm, and (d) Pleistocene loess 454-542 ppm. The solubility of F in black shales of coal-bearing sequences was higher than in Precambrian granitic rocks, and both were more soluble than loess. F solubility from Precambrian granitic rocks was moderate, but Precambrian granitic rocks have high F content and thus contribute an appreciable amount of ion to the shallow groundwater (well water). Varying F content in shallow groundwater is controlled by geological conditions. The sources of F in the shallow groundwater from fluorosis areas in northern China are mainly derived from black shales of coal-bearing sequences and Precambrian granitic basement in the basins of northern China. ?? 2008 Taylor & Francis.

Brine Migration from a Flooded Salt Mine in the Genesee Valley, Livingston County, New York: Geochemical Modeling and Simulation of Variable-Density Flow

USGS Publications Warehouse

Yager, Richard M.; Misut, Paul E.; Langevin, Christian D.; Parkhurst, David L.

2009-01-01

The Retsof salt mine in upstate New York was flooded from 1994 to 1996 after two roof collapses created rubble chimneys in overlying bedrock that intersected a confined aquifer in glacial sediments. The mine now contains about 60 billion liters of saturated halite brine that is slowly being displaced as the weight of overlying sediments causes the mine cavity to close, a process that could last several hundred years. Saline water was detected in the confined aquifer in 2002, and a brine-mitigation project that includes pumping followed by onsite desalination was implemented in 2006 to prevent further migration of saline water from the collapse area. A study was conducted by the U.S. Geological Survey using geochemical and variable-density flow modeling to determine sources of salinity in the confined aquifer and to assess (1) processes that control movement and mixing of waters in the collapse area, (2) the effect of pumping on salinity, and (3) the potential for anhydrite dissolution and subsequent land subsidence resulting from mixing of waters induced by pumping. The primary source of salinity in the collapse area is halite brine that was displaced from the flooded mine and transported upward by advection and dispersion through the rubble chimneys and surrounding deformation zone. Geochemical and variable-density modeling indicate that salinity in the upper part of the collapse area is partly derived from inflow of saline water from bedrock fracture zones during water-level recovery (January 1996 through August 2006). The lateral diversion of brine into bedrock fracture zones promoted the upward migration of mine water through mixing with lower density waters. The relative contributions of mine water, bedrock water, and aquifer water to the observed salinity profile within the collapse area are controlled by the rates of flow to and from bedrock fracture zones. Variable-density simulations of water-level recovery indicate that saline water has probably not migrated beyond the collapse area, while simulations of pumping indicate that further upward migration of brine and saline water is now prevented by groundwater withdrawals under the brine-mitigation project. Geochemical modeling indicates that additional land subsidence as a result of anhydrite dissolution in the collapse area is not a concern, as long as the rate of brine pumping is less than the rate of upward flow of brine from the flooded mine. The collapse area above the flooded salt mine is within a glacially scoured bedrock valley that is filled with more than 150 meters of glacial drift. A confined aquifer at the bottom of the glacial sediments (referred to as the lower confined aquifer, or LCA) was the source of most of the water that flooded the mine. Two rubble chimneys that formed above the roof collapses in 1994 hydraulically connect the flooded mine to the LCA through 180 meters of sedimentary rock. From 1996 through 2006, water levels in the aquifer system recovered and the brine-displacement rate ranged from 4.4 to 1.6 liters per second, as estimated from land-surface subsidence above the mine. A zone of fracturing within the bedrock (the deformation zone) formed around the rubble chimneys as rock layers sagged toward the mine cavity after the roof collapses. Borehole geophysical surveys have identified three saline-water-bearing fracture zones in the bedrock: at stratigraphic contacts between the Onondaga and Bertie Limestones (O/B-FZ) and the Bertie Limestone and the Camillus Shale (B/C-FZ), and in the Syracuse Formation (Syr-FZ). The only outlets for brine displaced from the mine are through the rubble chimneys, but some of the brine could be diverted laterally into fracture zones in the rocks that lie between the mine and the LCA. Inverse geochemical models developed using PHREEQC indicate that halite brine in the flooded mine is derived from a mixture of freshwater from the LCA (81 percent), saline water from bedrock fracture zones (16 per

Joint inversion of satellite-detected tidal and magnetospheric signals constrains electrical conductivity and water content of the upper mantle and transition zone.

PubMed

Grayver, A V; Munch, F D; Kuvshinov, A V; Khan, A; Sabaka, T J; Tøffner-Clausen, L

2017-06-28

We present a new global electrical conductivity model of Earth's mantle. The model was derived by using a novel methodology, which is based on inverting satellite magnetic field measurements from different sources simultaneously. Specifically, we estimated responses of magnetospheric origin and ocean tidal magnetic signals from the most recent Swarm and CHAMP data. The challenging task of properly accounting for the ocean effect in the data was addressed through full three-dimensional solution of Maxwell's equations. We show that simultaneous inversion of magnetospheric and tidal magnetic signals results in a model with much improved resolution. Comparison with laboratory-based conductivity profiles shows that obtained models are compatible with a pyrolytic composition and a water content of 0.01 wt% and 0.1 wt% in the upper mantle and transition zone, respectively.

The effect of channel shape, bed morphology, and shipwrecks on flow velocities in the Upper St. Clair River

USGS Publications Warehouse

Czuba, Jonathan A.; Oberg, Kevin; Best, Jim; Parsons, Daniel R.

2009-01-01

In the Great Lakes of North America, the St. Clair River is the major outlet of Lake Huron and conveys water to Lake St. Clair which then flows to Lake Erie. One major topic of interest is morphological change in the St. Clair River and its impact on water levels in the Upper Great Lakes and connecting channel flows. A combined multibeam echosounder (MBES) bathymetric survey and acoustic Doppler current profiler (ADCP) flow survey of the outlet of Lake Huron and the Upper St. Clair River was conducted July 21 – 25, 2008. This paper presents how channel morphology and shipwrecks affect the flow in the Upper St. Clair River. The river is most constricted at the Blue Water Bridge near Port Huron, Michigan, with water velocities over 2 ms-1 for a flow of 5,200 m3s-1. Downstream of this constriction, the river flows around a bend and expands creating a large recirculation zone along the left bank due to flow separation. This recirculation zone reduces the effective channel width, and thus increases flow velocities to over 2 ms-1 in this region. The surveys reveal several shipwrecks on the bed of the St. Clair River, which possess distinct wakes in their flow velocity downstream of the wrecks. The constriction and expansion of the channel, combined with forcing of the flow by bed topography, initiates channel-scale secondary flow, creating streamwise vortices that maintain coherence downstream over a distance of several channel widths.

Hydrogeology, ground-water movement, and subsurface storage in the Floridan aquifer system in southern Florida

USGS Publications Warehouse

Meyer, Frederick W.

1989-01-01

The Floridan aquifer system of southern Florida is composed chiefly of carbonate rocks that range in age from early Miocene to Paleocene. The top of the aquifer system in southern Florida generally is at depths ranging from 500 to 1,000 feet, and the average thickness is about 3,000 feet. It is divided into three general hydrogeologic units: (1) the Upper Floridan aquifer, (2) the middle confining unit, and (3) the Lower Floridan aquifer. The Upper Floridan aquifer contains brackish ground water, and the Lower Floridan aquifer contains salty ground water that compares chemically to modern seawater. Zones of high permeability are present in the Upper and Lower Floridan aquifers. A thick, cavernous dolostone in the Lower Floridan aquifer, called the Boulder Zone, is one of the most permeable carbonate units in the world (transmissivity of about 2.5 x 107 feet squared per day). Ground-water movement in the Upper Floridan aquifer is generally southward from the area of highest head in central Florida, eastward to the Straits of Florida, and westward to the Gulf of Mexico. Distributions of natural isotopes of carbon and uranium generally confirm hydraulic gradients in the Lower Floridan aquifer. Groundwater movement in the Lower Floridan aquifer is inland from the Straits of Florida. The concentration gradients of the carbon and uranium isotopes indicate that the source of cold saltwater in the Lower Floridan aquifer is seawater that has entered through the karat features on the submarine Miami Terrace near Fort Lauderdale. The relative ages of the saltwater suggest that the rate of inland movement is related in part to rising sea level during the Holocene transgression. Isotope, temperature, and salinity anomalies in waters from the Upper Floridan aquifer of southern Florida suggest upwelling of saltwater from the Lower Floridan aquifer. The results of the study support the hypothesis of circulating relatively modern seawater and cast doubt on the theory that the saltwater in the Floridan aquifer system probably is connate or unflushed seawater from high stands of sea level. The principal use of the Floridan aquifer system in southern Florida is for subsurface storage of liquid waste. The Boulder Zone of the Lower Floridan aquifer is extensively used as a receptacle for injected treated municipal wastewater, oil field brine, and, to a lesser extent, industrial wastewater. Pilot studies indicate a potential for cyclic storage of freshwater in the Upper Floridan aquifer in southern Florida.

Reconciling laboratory and observational models of mantle rheology in geodynamic modelling

NASA Astrophysics Data System (ADS)

King, Scott D.

2016-10-01

Experimental and geophysical observations constraining mantle rheology are reviewed with an emphasis on their impact on mantle geodynamic modelling. For olivine, the most studied and best-constrained mantle mineral, the tradeoffs associated with the uncertainties in the activation energy, activation volume, grain-size and water content allow the construction of upper mantle rheology models ranging from nearly uniform with depth to linearly increasing from the base of the lithosphere to the top of the transition zone. Radial rheology models derived from geophysical observations allow for either a weak upper mantle or a weak transition zone. Experimental constraints show that wadsleyite and ringwoodite are stronger than olivine at the top of the transition zone; however the uncertainty in the concentration of water in the transition zone precludes ruling out a weak transition zone. Both observational and experimental constraints allow for strong or weak slabs and the most promising constraints on slab rheology may come from comparing inferred slab geometry from seismic tomography with systematic studies of slab morphology from dynamic models. Experimental constraints on perovskite and ferropericlase strength are consistent with general feature of rheology models derived from geophysical observations and suggest that the increase in viscosity through the top of the upper mantle could be due to the increase in the strength of ferropericlase from 20-65 GPa. The decrease in viscosity in the bottom half of the lower mantle could be the result of approaching the melting temperature of perovskite. Both lines of research are consistent with a high-viscosity lithosphere, a low viscosity either in the upper mantle or transition zone, and high viscosity in the lower mantle, increasing through the upper half of the lower mantle and decreasing in the bottom half of the lower mantle, with a low viscosity above the core. Significant regions of the mantle, including high-stress regions of the lower mantle, may be in the dislocation creep (power-law) regime. Due to our limited knowledge of mantle grain size, the best hope to resolve the question of whether a region is in diffusion creep (Newtonian rheology) or dislocation or grain-boundary creep (power-law rheology), may be the presence of absence of seismic anisotropy, because there is no mechanism to rotate crystals in diffusion creep which would be necessary to develop anisotropy from lattice preferred orientation. While non-intuitive, the presence or absence of a weak region in the upper mantle has a profound effect on lower mantle flow. With an asthenosphere, the lower mantle organizes into a long-wavelength plan form with one or two (degree 1 or degree 2) large downwellings and updrafts, which may contain a cluster of plumes. The boundary between the long-wavelength lower mantle flow and upper region flow may be deeper, likely 800-1200 km, than the usually assumed base of the transition zone. There are competing hypotheses as to whether this change in flow pattern is caused by a change in rheology, composition, or phase.

Glass Inclusions and Melt Volatile Contents in the Late-Quaternary Basanites and Minettes of Colima (Mexico)

NASA Astrophysics Data System (ADS)

Maria, A. H.; Luhr, J. F.

2002-12-01

Olivine-hosted glass inclusions from fine tephra collected at three basanite-minette cinder cones on the lower flanks of the Colima Volcanic Complex in western Mexico were analyzed by electron microprobe and Fourier-transform infrared spectroscopy (FTIR). These nepheline-normative rocks have elemental-abundance patterns that mimic those of the volumetrically dominant subduction-related andesites, but at much higher abundance levels. Sr, Nd, and Pb isotopic ratios are also similar for the two suites. We interpret the Colima basanites and minettes as recording the "essence" of subduction-zone geochemistry, produced by nearly pure melting of phlogopite-rich veins in the mantle wedge, and erupted in western Mexico only because of its unusual upper crustal extensional regime. Similar melts impart the subduction-zone geochemical flavor to the dominant andesites, which differentiate from basalts produced by higher degrees of mantle wallrock melting. Olivine crystals separated from the basanite-minette tephra have Mg#s that range from 81.5 to 90.7. The 34 glass inclusions studied contain 49-60 wt.% SiO2 and include 2 with normative quartz, and 6 with normative hypersthene, with the remaining 26 containing up to 11.5% normative nepheline. The glasses also contain 2.8-8.4% K2O, 0.16-0.33% Cl, and 0.03-1.19% total sulfur as SO3. Comparison of Fe/Mg values of glass and host olivines indicates 1-5% crystallization of olivine from the inclusions following entrapment. FTIR measurements were made on 26 of the inclusions. No reliable carbonate or CO2 peaks were detected in any glass inclusion, but a significant 2350 cm-1 CO2 peak was found for a bubble completely trapped within one inclusion. Total water contents estimated from the 3535 cm-1 peak range from 0.2 % to 2.0%, with only 8 values above 1%. These relatively low water contents are surprising, especially for the phlogopite-bearing minettes. A value of 2.0% water corresponds to water saturation at a pressure of 415 bars, equivalent to a depth of 1600 m. We consider the possibility that the magmas ascended through much of the crust in a superheated condition, and stagnated in the uppermost crust where the bulk of the olivine crystals grew in a rapid skeletal fashion trapping the glass inclusions. Such stagnation is consistent with the complete lack of ultramafic xenoliths at these cones. Published phase-equilibrium experiments on an olivine-bearing minette imply that phlogopite is stable down to pressures of 200-400 bars, also consistent with this interpretation.

Dry Juan de Fuca slab revealed by quantification of water entering Cascadia subduction zone

NASA Astrophysics Data System (ADS)

Canales, J. P.; Carbotte, S. M.; Nedimović, M. R.; Carton, H.

2017-11-01

Water is carried by subducting slabs as a pore fluid and in structurally bound minerals, yet no comprehensive quantification of water content and how it is stored and distributed at depth within incoming plates exists for any segment of the global subduction system. Here we use seismic data to quantify the amount of pore and structurally bound water in the Juan de Fuca plate entering the Cascadia subduction zone. Specifically, we analyse these water reservoirs in the sediments, crust and lithospheric mantle, and their variations along the central Cascadia margin. We find that the Juan de Fuca lower crust and mantle are drier than at any other subducting plate, with most of the water stored in the sediments and upper crust. Variable but limited bend faulting along the margin limits slab access to water, and a warm thermal structure resulting from a thick sediment cover and young plate age prevents significant serpentinization of the mantle. The dryness of the lower crust and mantle indicates that fluids that facilitate episodic tremor and slip must be sourced from the subducted upper crust, and that decompression rather than hydrous melting must dominate arc magmatism in central Cascadia. Additionally, dry subducted lower crust and mantle can explain the low levels of intermediate-depth seismicity in the Juan de Fuca slab.

Alumina+Silica+/-Germanium Alteration in Smectite-Bearing Marathon Valley, Endeavour Crater Rim, Mars

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Gellert, R.; Van Bommel, S.; Arvidson, R. E.; Clark, B. C.; Ming, D. W.; Schroeder, C.; Yen, A. S.; Fox, V. K.; Farrand, W. H.;

Environmental tritium and radiocarbon studies in the Vedavati River basin, Karnataka and Andhra Pradesh, India

NASA Astrophysics Data System (ADS)

Sukhija, B. S.; Achutha Rao, A.

1983-01-01

Environmental tritium and radiocarbon studies were undertaken in the Vedavati river basin situated partly in Karnataka and partly in Andhra Pradesh, India, aimed at the determination of the general recharge condition of the water-bearing zones in the gneissic complex, granites and the Dharwar Group of metamorphic rocks, where groundwater occurs under semi-unconfined to semi-confined conditions and at places under the water-table condition. The groundwater movement is controlled by fractures, fissures, a weathered zone and surficial mantle. An attempt was also made to find out whether substantial recharge occurs along fractured lineaments; whether the water-bearing zones can be considered as interconnected or isolated, and whether the recharge and discharge areas identified by geohydrological considerations can be confirmed. Environmental tritium and radiocarbon contents, measured in ˜ 45 groundwater samples, show that a large number of samples are very young, containing water from post-thermonuclear-era rain, thus indicating an age less than 25 yr. In some other samples, despite radiocarbon ages found to be older, some component of recent precipitation is found to be present as indicated by bomb tritium. Groundwater dating in the area shows an excellent correlation between hydro-isochrons of minimum age with the recharge contour of maximum magnitude. This study has clearly resulted in the demarcation of the recharge areas. However, the discharge areas as such cannot be clearly delineated because of lack of a pattern indicating increase of ages in any particular direction. This, however, also reflects somewhat discontinuous groundwater bodies, which may also be expected from the general structure and hydrogeology of the region. Along a major lineament the groundwater is found to be very young thus confirming that substantial recharge occurs along lineaments.

Links between climate change, water-table depth, and water chemistry in a mineralized mountain watershed

USGS Publications Warehouse

Manning, Andrew H.; Verplanck, Philip L.; Caine, Jonathan S.; Todd, Andrew S.

2013-01-01

Recent studies suggest that climate change is causing rising solute concentrations in mountain lakes and streams. These changes may be more pronounced in mineralized watersheds due to the sensitivity of sulfide weathering to changes in subsurface oxygen transport. Specific causal mechanisms linking climate change and accelerated weathering rates have been proposed, but in general remain entirely hypothetical. For mineralized watersheds, a favored hypothesis is that falling water tables caused by declining recharge rates allow an increasing volume of sulfide-bearing rock to become exposed to air, thus oxygen. Here, we test the hypothesis that falling water tables are the primary cause of an increase in metals and SO4 (100-400%) observed since 1980 in the Upper Snake River (USR), Colorado. The USR drains an alpine watershed geologically and climatologically representative of many others in mineralized areas of the western U.S. Hydrologic and chemical data collected from 2005 to 2011 in a deep monitoring well (WP1) at the top of the USR watershed are utilized. During this period, both water table depths and groundwater SO4 concentrations have generally increased in the well. A numerical model was constructed using TOUGHREACT that simulates pyrite oxidation near WP1, including groundwater flow and oxygen transport in both saturated and unsaturated zones. The modeling suggests that a falling water table could produce an increase in metals and SO4 of a magnitude similar to that observed in the USR (up to 300%). Future water table declines may produce limited increases in sulfide weathering high in the watershed because of the water table dropping below the depth of oxygen penetration, but may continue to enhance sulfide weathering lower in the watershed where water tables are shallower. Advective air (oxygen) transport in the unsaturated zone caused by seasonally variable recharge and associated water table fluctuations was found to have little influence on pyrite oxidation rates near WP1. However, this mechanism could be important in the case of a shallow dynamic water table and more abundant/reactive sulfides in the shallow subsurface. Data from WP1 and numerical modeling results are thus consistent with the falling water table hypothesis, and illustrate fundamental processes linking climate and sulfide weathering in mineralized watersheds.

Recovery of Ground-Water Levels from 1988 to 2003 and Analysis of Effects of 2003 and Full-Allocation Withdrawals in Critical Area 2, Southern New Jersey

USGS Publications Warehouse

Spitz, Frederick J.; dePaul, Vincent T.

2008-01-01

Water levels in the Potomac-Raritan-Magothy aquifer system within Water Supply Critical Area 2 in the southern New Jersey Coastal Plain have recovered as a result of reductions in ground-water withdrawals initiated in the early 1990s. The Critical Area consists of the depleted zone and the threatened margin. The Potomac-Raritan-Magothy aquifer system consists of the Upper, Middle, and Lower aquifers. Generally, ground-water withdrawals from these aquifers declined 5 to 10 Mgal/d (million gallons per day) and water levels recovered 0 to 40 ft (foot) from 1988 to 2003. In order to reevaluate water-allocation restrictions in Critical Area 2 in response to changes in the ground-water-flow system and demands for additional water supply due to increased development, the New Jersey Department of Environmental Protection (NJDEP) needs information about the effects of changes in those allocations. Therefore, the U.S. Geological Survey (USGS), in cooperation with the NJDEP, used an existing ground-water-flow model of the New Jersey Coastal Plain to evaluate the effects of withdrawal alternatives on hydraulic heads in the Potomac-Raritan-Magothy aquifer system in Critical Area 2. The U.S. Geological Survey Regional Aquifer System Analysis model was used to simulate steady-state ground-water flow. Two withdrawal conditions were tested by using the model to evaluate hydraulic heads and differences in heads in these aquifers: 2003 withdrawals and full-allocation withdrawals (17.4 Mgal/d greater than 2003 withdrawals). Model results are presented using head maps and head-difference maps that compare 2003 to full-allocation withdrawals. Mandated hydrologic conditions for Critical Area protection are that the simulated -30-ft head contour not extend beyond the boundary of the depleted zone and (or) be at least 5 mi (miles) updip from the 250-mg/L (milligram per liter) isochlor in all three aquifers. Simulation results indicate that, for 2003 withdrawals, the simulated -30-ft head contour in all three aquifers is generally within the boundary of the depleted zone, except in the Lower aquifer in northern Camden and northwestern Burlington Counties, and is generally 1 to 10 mi downdip from the 250-mg/L isochlor. (Corresponding observed data indicate that the -30-ft water-level contour extends beyond the southwest boundary of the depleted zone in the Upper and Middle aquifers, and is generally 5 to 20 mi downdip from the 250-mg/L isochlor in all three aquifers.) The area in which heads are below -30 ft ranges from 389 mi2 (square miles) in the Middle aquifer to 427 mi2 in the Lower aquifer. For full-allocation withdrawals, the simulated -30-ft head contour extends beyond the boundary of the depleted zone in all three aquifers in northern Camden and northwestern Burlington Counties and in the Upper aquifer in Gloucester and Salem Counties, and is generally 5 to 15 mi downdip from the 250-mg/L isochlor. The area in which heads are below -30 ft ranges from 616 mi2 in the Upper aquifer to 813 mi2 in the Lower aquifer. These results and observed data indicate that any increase in withdrawals from 2003 values would likely cause heads in the three aquifers to decline below the minimum values mandated by the NJDEP for the Critical Area.

Diagenesis of the Oligocene-Miocene rocks of the Upper Floridan and Intermediate aquifer systems by meteoric and mixing-zone waters in southwest Florida

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weedman, S.D.; McCartan, L.

1993-03-01

Optical and SEM of samples from 6 cores of Oligocene and Miocene rocks that compose portions of the Florida and Intermediate aquifers and the intervening semiconfining unit documents meteoric and mixing-zone (seawater and fresh carbonate ground water) diagenesis inferred to have occurred over several cycles of sea level change. Dolomite, limestone, sandstone, and claystone of the Suwannee Formation and the Arcadia Formation (Hawthorn Group) were examined. Core samples from time-equivalent strata in two E--W transects in Manatee, Hardee, Highlands, Sarasota, and DeSoto Counties are estimated to be 16--33 Ma on the basis of [sup 87]Sr/[sup 86]Sr ratios from unaltered molluskmore » shells and by molluscan biostratigraphy. Lithostratigraphic correlations are based on examination of 19 cores, 62 thin sections, 60 geophysical logs, and mineralogy determined by X-ray diffraction. Diagenetic indicators that the authors tracked petrographically include shell micritization, shell dissolution, equant and (or) fibrous CaCO[sub 3] cement, neomorphism, dolomite, etched phosphate grains, echinoderm fragment syntaxial overgrowths, and amorphous silica pore lining. Infiltration of meteoric water caused dissolution of carbonate minerals, especially aragonite, and precipitation of equant calcite crystals in voids of dissolved fossils and in pore spaces between grains. The silica was precipitated as pore linings in zones having soil textures. Observed replacement of calcite by limpid dolomite is consistent with modeling predictions of mixing-zone diagenesis. Etched crystals of limpid dolomite may indicate freshwater dissolution of a mixing-zone precipitate. Mapping of regional unconformities revealed pronounced thickening and thinning of some units. Evidence of meteoric water diagenesis is observed in the upper 600 ft of the transects examined. Evidence of mixing-zone diagenesis is observed at varying depths, but appears to increase in abundance and thickness toward the west.« less

Geological Assessment of Cores from the Great Bay National Wildlife Refuge, New Hampshire

USGS Publications Warehouse

Foley, Nora K.; Ayuso, Robert A.; Ayotte, Joseph D.; Montgomery, Denise L.; Robinson, Gilpin R.

2007-01-01

Geological sources of metals (especially arsenic and zinc) in aquifer bedrock were evaluated for their potential to contribute elevated values of metals to ground and surface waters in and around Rockingham County, New Hampshire. Ayotte and others (1999, 2003) had proposed that arsenic concentrations in ground water flowing through bedrock aquifers in eastern New England were elevated as a result of interaction with rocks. Specifically in southeastern New Hampshire, Montgomery and others (2003) established that nearly one-fifth of private bedrock wells had arsenic concentrations that exceed the U.S. Environmental Protection Agency (EPA) maximum contamination level for public water supplies. Two wells drilled in coastal New Hampshire were sited to intersect metasedimentary and metavolcanic rocks in the Great Bay National Wildlife Refuge. Bulk chemistry, mineralogy, and mineral chemistry data were obtained on representative samples of cores extracted from the two boreholes in the Kittery and Eliot Formations. The results of this study have established that the primary geologic source of arsenic in ground waters sampled from the two well sites was iron-sulfide minerals, predominantly arsenic-bearing pyrite and lesser amounts of base-metal-sulfide and sulfosalt minerals that contain appreciable arsenic, including arsenopyrite, tetrahedrite, and cobaltite. Secondary minerals containing arsenic are apparently limited to iron-oxyhydroxide minerals. The geologic source of zinc was sphalerite, typically cadmium-bearing, which occurs with pyrite in core samples. Zinc also occurred as a secondary mineral in carbonate form. Oxidation of sulfides leading to the liberation of acid, iron, arsenic, zinc, and other metals was most prevalent in open fractures and vuggy zones in core intervals containing zones of high transmissivity in the two units. The presence of significant calcite and lesser amounts of other acid-neutralizing carbonate and silicate minerals, acting as a natural buffer to reduce acidity, forced precipitation of iron-oxyhydroxide minerals and the removal of trace elements, including arsenic and lead, from ground waters in the refuge. Zinc may have remained in solution to a greater extent because of complexing with carbonate and its solubility in near-neutral ground and surface waters. The regional link between anomalously high arsenic contents in ground water and a bedrock source as established by Ayotte and others (1999, 2003) and Montgomery and others (2003) was confirmed by the presence of some arsenic-bearing minerals in rocks of the Kittery and Eliot Formations. The relatively low amounts of arsenic and metals in wells in the Great Bay National Wildlife Refuge as reported by Ayotte and others (U.S. Geological Survey Water Resources Data, 2005) were likely controlled by local geochemical environments in partially filled fractures, fissures, and permeable zones within the bedrock formations. Carbonate and silicate gangue minerals that line fractures, fissures, and permeable zones likely limited the movement of arsenic from bedrock to ground water. Sources other than the two geologic formations might have been required to account for anomalously high arsenic contents measured in private bedrock aquifer wells of Rockingham County.

Water-Level Conditions in Selected Confined Aquifers of the New Jersey and Delaware Coastal Plain, 2003

USGS Publications Warehouse

dePaul, Vincent T.; Rosman, Robert; Lacombe, Pierre J.

2009-01-01

The Coastal Plain aquifers of New Jersey provide an important source of water for more than 2 million people. Steadily increasing withdrawals from the late 1800s to the early 1990s resulted in declining water levels and the formation of regional cones of depression. In addition to decreasing water supplies, declining water levels in the confined aquifers have led to reversals in natural hydraulic gradients that have, in some areas, induced the flow of saline water from surface-water bodies and adjacent aquifers to freshwater aquifers. In 1978, the U.S. Geological Survey began mapping the potentiometric surfaces of the major confined aquifers of New Jersey every 5 years in order to provide a regional assessment of ground-water conditions in multiple Coastal Plain aquifers concurrently. In 1988, mapping of selected potentiometric surfaces was extended into Delaware. During the fall of 2003, water levels measured in 967 wells in New Jersey, Pennsylvania, northeastern Delaware, and northwestern Maryland were used estimate the potentiometric surface of the principal confined aquifers in the Coastal Plain of New Jersey and five equivalent aquifers in Delaware. Potentiometric-surface maps and hydrogeologic sections were prepared for the confined Cohansey aquifer of Cape May County, the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, the Vincentown aquifer, and the Englishtown aquifer system in New Jersey, as well as for the Piney Point aquifer, the Wenonah-Mount Laurel aquifer, and the Upper Potomac-Raritan-Magothy, the Middle and undifferentiated Potomac-Raritan-Magothy, and the Lower Potomac-Raritan-Magothy aquifers in New Jersey and their equivalents in Delaware. From 1998 to 2003, water levels in many Coastal Plain aquifers in New Jersey remained stable or had recovered, but in some areas, water levels continued to decline as a result of pumping. In the Cohansey aquifer in Cape May County, water levels near the center of the cone of depression underlying the southern part of the peninsula remained about the same as in 1998. To the south, recoveries up to 8 feet were observed in southern Lower Township as withdrawals had decreased since 1998. In the northern part of Cape May County, water levels had not changed substantially from historic conditions. In the Rio Grande water-bearing zone, water levels rose by as much as 13 ft at the Rio Grande well field; elsewhere across the aquifer, little change had occurred. In the Atlantic City 800-foot sand, water-level changes were greatest in southern Cape May County; at the Cape May desalination wells, water levels were as much as 32 ft lower in 2003 than in 1998. In contrast, water levels at the center of a regional cone of depression near Atlantic City rose by as much as 10 ft. Within the Piney Point aquifer water levels rose by 46 ft near Seaside Park. Similarly, water levels increased by more than 30 ft in and around the major cone of depression underlying Dover, Delaware. In the Vincentown aquifer, water levels stabilized or recovered by 2 ft to 6 ft from 1998 to 2003 in most of the wells measured; the exception is near Adelphia in Monmouth County, where water levels rose by as much as 18 ft. From 1998 to 2003, water levels near the center of a large cone of depression that extends from Monmouth to Ocean County recovered by as much as 20 ft in the Wenonah-Mount Laurel aquifer. Concurrently, ground-water levels within the Englishtown aquifer system declined by as much as 13 ft in the same area. Water levels across much of the Upper Potomac-Raritan-Magothy aquifer in the northern Coastal Plain remained about the same as 5 years previous, except in northern Ocean County where ground-water levels declined 10 ft to 33 ft. Water levels in the Middle Potomac-Raritan-Magothy aquifer declined from 5 to 9 ft along the border between Monmouth and Middlesex County. Elsewhere, across the northern part of the Coastal Plain, water levels stabilized within the Cretaceous-a

Calibration parameters used to simulate streamflow from application of the Hydrologic Simulation Program-FORTRAN Model (HSPF) to mountainous basins containing coal mines in West Virginia

USGS Publications Warehouse

Atkins, John T.; Wiley, Jeffrey B.; Paybins, Katherine S.

2005-01-01

This report presents the Hydrologic Simulation Program-FORTRAN Model (HSPF) parameters for eight basins in the coal-mining region of West Virginia. The magnitude and characteristics of model parameters from this study will assist users of HSPF in simulating streamflow at other basins in the coal-mining region of West Virginia. The parameter for nominal capacity of the upper-zone storage, UZSN, increased from south to north. The increase in UZSN with the increase in basin latitude could be due to decreasing slopes, decreasing rockiness of the soils, and increasing soil depths from south to north. A special action was given to the parameter for fraction of ground-water inflow that flows to inactive ground water, DEEPFR. The basis for this special action was related to the seasonal movement of the water table and transpiration from trees. The models were most sensitive to DEEPFR and the parameter for interception storage capacity, CEPSC. The models were also fairly sensitive to the parameter for an index representing the infiltration capacity of the soil, INFILT; the parameter for indicating the behavior of the ground-water recession flow, KVARY; the parameter for the basic ground-water recession rate, AGWRC; the parameter for nominal capacity of the upper zone storage, UZSN; the parameter for the interflow inflow, INTFW; the parameter for the interflow recession constant, IRC; and the parameter for lower zone evapotranspiration, LZETP.

Burnable absorber arrangement for fuel bundle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowther, R.L.; Townsend, D.B.

1986-12-16

This patent describes a boiling water reactor core whose operation is characterized by a substantial proportion of steam voids with concomitantly reduced moderation toward the top of the core when the reactor is in its hot operating condition. The reduced moderation leads to slower burnup and greater conversion ratio in an upper core region so that when the reactor is in its cold shut down condition the resulting relatively increased moderation in the upper core region is accompanied by a reactivity profile that peaks in the upper core region. A fuel assembly is described comprising; a component of fissile materialmore » distributed over a substantial axial extent of the fuel assembly; and a component of neutron absorbing material having an axial distribution characterized by an enhancement in an axial zone of the fuel assembly, designated the cold shutdown control zone, corresponding to at least a portion of the axial region of the core when the cold shutdown reactivity peaks. The aggregate amount of neutron absorbing material in the cold shutdown zone of the fuel assembly is greater than the aggregate amount of neutron absorbing material in the axial zones of the fuel assembly immediately above and immediately below the cold shutdown control zone whereby the cold shutdown reactivity peak is reduced relative to the cold shutdown reactivity in the zones immediately above and immediately below the cold shutdown control zone. The cold shutdown zone has an axial extent measured from the bottom of the fuel assembly in the range between 68-88 percent of the height of the fissile material in the fuel assembly.« less

Geochemical evidence for enhanced preservation of organic matter in the oxygen minimum zone of the continental margin of northern California during the Late Pleistocene

USGS Publications Warehouse

Dean, Walter E.; Gardner, James V.; Anderson, Roger Y.

1994-01-01

The present upper water mass of the northeastern Pacific Ocean off California has a well-developed oxygen minimum zone between 600 and 1200 m wherein concentrations of dissolved oxygen are less than 0.5 mL/L. Even at such low concentrations of dissolved oxygen, benthic burrowing organisms are abundant enough to thoroughly bioturbate the surface and near-surface sediments. These macro organisms, together with micro organisms, also consume large quantities of organic carbon produced by large seasonal stocks of plankton in the overlying surface waters, which are supported by high concentrations of nutrients within the California Current upwelling system. In contrast to modern conditions of bioturbation, laminated sediments are preserved in upper Pleistocene sections of cores collected on the continental slope at water depths within the present oxygen minimum zone from at least as far north as the California-Oregon border and as far south as Point Conception. Comparison of sediment components in the laminae with those delivered to sediment traps as pelagic marine “snow” demonstrates that the dark-light lamination couplets are indeed annual (varves). These upper Pleistocene varved sediments contain more abundant lipid-rich “sapropelic” (type II) organic matter than the overlying bioturbated, oxidized Holocene sediments. The baseline of stable carbon isotopic composition of the organic matter in these slope cores does not change with time, indicating that the higher concentrations of type II organic matter in the varved sediments represent better preservation of organic matter rather than any change in the source of organic matter.

3D modeling of magnetotelluric data unraveling the tectonic setting and sources of magmatism in the northeastern corner of Borborema Province, NE Brazil

NASA Astrophysics Data System (ADS)

Padilha, A. L.; Vitorello, I.; Padua, M. B.; Batista, J. C.; Fuck, R. A.

2017-12-01

The Borborema Province in northeast Brazil is a complex orogenic system formed by crustal blocks of different ages, origin and evolution amalgamated during the West Gondwana convergence in late Neoproterozoic-early Phanerozoic Brasiliano Orogeny. We discuss here new magnetotelluric (MT) data collected along four linear profiles crisscrossing the northeastern corner of the province to assess its deep electrical resistivity structure. Dimensionality analysis showed that a 3D electrical structure predominates in the subsurface and thus the data were modeled by a 3D MT data inversion scheme. The modeling revealed several subvertical discontinuities, with significant lateral contrast in the overall geoelectric structure, down to upper mantle depths. A major conductivity anomaly is registered in the crust beneath Neoproterozoic supracrustal rocks (Serido Group) and this anomaly deepens to upper mantle depths in the northwest direction below a zone of Paleoproterozoic plutons (Caico Complex). It has been suggested that the Serido Group was originally initiated as a sedimentary basin developed upon a Paleoproterozoic basement during a Neoproterozoic extension event related to a collisional foredeep of a south-dipping subduction slab, contrary to our northwest-dipping conductivity vergence. In case of the Caico Complex, because of the petrogenesis of its orthogneisses that indicates partial melting of a metasomatically enriched spinel-to garnet-bearing lherzolite with adakitic features, we also propose a subduction zone environment for its original magmatism. Considering the tenuous evidence indicating that this conductive anomaly could extend down into the upper mantle in the same region where teleseismic tomography register an attenuation of P waves, it can be concluded that this zone could also be the source of the metasomatic fluids and minerals observed along north-south Mesozoic volcanic plugs and flows of alkaline rocks and alkali basalts (Macau-Queimadas belt). In contrast to the general pattern in several parts of the province exhibiting a multitude of resistive and conductive zones marking the crust and upper mantle, an elongated resistive cratonic-like keel in the WSW-ENE direction is observed along the southeastern side of the study area.

The Approach to Study the Kama Reservoir Basin Deformation in the Zone of a Variable Backwater

NASA Astrophysics Data System (ADS)

Dvinskikh, S. A.; Kitaev, A. B.; Shaydulina, A. A.

2018-01-01

A reservoir floor starts to change since it has been filled up to a normal headwater level (NHL) under the impact of hydrosphere and lithosphere interactions as well as under the impact of chemical and biological processes that occur in its water masses. At that complicated and often contradictory “relations” between features of geo- and hydrodynamic processes are created. The consequences of these relations are the alterations of values of morphometric indices of the reservoir water surface, depth and volume. We observe two processes that are oppositely directed. They are accumulation and erosion. They are more complex at the upper area of the reservoir - the zone of a variable backwater. The basin deformation observed there is lop-sided and relatively quiet, but with time these deformations make difficulties for water users. To provide good navigation and to reduce harmful effect of waters on other water consumption objects, it is necessary to study and to forecast constantly the basin transformation processes that occur at this zone.

Subduction zone earthquake probably triggered submarine hydrocarbon seepage offshore Pakistan

NASA Astrophysics Data System (ADS)

Fischer, David; José M., Mogollón; Michael, Strasser; Thomas, Pape; Gerhard, Bohrmann; Noemi, Fekete; Volkhard, Spiess; Sabine, Kasten

2014-05-01

Seepage of methane-dominated hydrocarbons is heterogeneous in space and time, and trigger mechanisms of episodic seep events are not well constrained. It is generally found that free hydrocarbon gas entering the local gas hydrate stability field in marine sediments is sequestered in gas hydrates. In this manner, gas hydrates can act as a buffer for carbon transport from the sediment into the ocean. However, the efficiency of gas hydrate-bearing sediments for retaining hydrocarbons may be corrupted: Hypothesized mechanisms include critical gas/fluid pressures beneath gas hydrate-bearing sediments, implying that these are susceptible to mechanical failure and subsequent gas release. Although gas hydrates often occur in seismically active regions, e.g., subduction zones, the role of earthquakes as potential triggers of hydrocarbon transport through gas hydrate-bearing sediments has hardly been explored. Based on a recent publication (Fischer et al., 2013), we present geochemical and transport/reaction-modelling data suggesting a substantial increase in upward gas flux and hydrocarbon emission into the water column following a major earthquake that occurred near the study sites in 1945. Calculating the formation time of authigenic barite enrichments identified in two sediment cores obtained from an anticlinal structure called "Nascent Ridge", we find they formed 38-91 years before sampling, which corresponds well to the time elapsed since the earthquake (62 years). Furthermore, applying a numerical model, we show that the local sulfate/methane transition zone shifted upward by several meters due to the increased methane flux and simulated sulfate profiles very closely match measured ones in a comparable time frame of 50-70 years. We thus propose a causal relation between the earthquake and the amplified gas flux and present reflection seismic data supporting our hypothesis that co-seismic ground shaking induced mechanical fracturing of gas hydrate-bearing sediments creating pathways for free gas to migrate from a shallow reservoir within the gas hydrate stability zone into the water column. Our results imply that free hydrocarbon gas trapped beneath a local gas hydrate seal was mobilized through earthquake-induced mechanical failure and in that way circumvented carbon sequestration within the sediment. These findings lead to conclude that hydrocarbon seepage triggered by earthquakes can play a role for carbon budgets at other seismically active continental margins. The newly identified process presented in our study is conceivable to help interpret data from similar sites. Reference: Fischer, D., Mogollon, J.M., Strasser, M., Pape, T., Bohrmann, G., Fekete, N., Spieß, V. and Kasten, S., 2013. Subduction zone earthquake as potential trigger of submarine hydrocarbon seepage. Nature Geoscience 6: 647-651.

The hydrogeology of Kilauea volcano

USGS Publications Warehouse

Ingebritsen, S.E.; Scholl, M.A.

1993-01-01

The hydrogeology of Kilauea volcano and adjacent areas has been studied since the turn of this century. However, most studies to date have focused on the relatively shallow, low-salinity parts of the ground-water system, and the deeper hydrothermal system remains poorly understood. The rift zones of adjacent Mauna Loa volcano bound the regional ground-water flow system that includes Kilauea, and the area bounded by the rift zones of Kilauea and the ocean may comprise a partly isolated subsystem. Rates of ground-water recharge vary greatly over the area and discharge is difficult to measure, because streams are ephemeral and most ground-water discharges diffusely at or below sea level. Hydrothermal systems exist at depth in Kilauea's cast and southwest rift zone, as evidenced by thermal springs at the coast and wells in the lower east-rift zone. Available data suggest that dike-impounded, heated ground water occurs at relatively high elevations in the upper east-and southwest-rift zones of Kilauea, and that permeability at depth in the rift zones (probably 10 10 m2). Substantial variations in permeability and the presence of magmatic heat sources influence the structure of the fresh water-salt water interface, so the Ghyben-Herzberg model will often fail to predict its position. Numerical modeling studies have considered only subsets of the hydrothermal system, because no existing computer code solves the coupled fluid-flow, heat- and solute-transport problem over the temperature and salinity range encountered at Kilauea. ?? 1993.

Relating rheology to geometry in large-scale natural shear zones

NASA Astrophysics Data System (ADS)

Platt, John

2016-04-01

The geometry and width of the ductile roots of plate boundary scale faults are very poorly understood. Some field and geophysical data suggests widths of tens of km in the lower crust, possibly more in the upper mantle. Other observations suggest they are much narrower. Dip slip shear zones may flatten out and merge into zones of subhorizontal lower crustal or asthenospheric flow. The width of a ductile shear zone is simply related to relative velocity and strain rate. Strain rate is related to stress through the constitutive relationship. Can we constrain the stress, and do we understand the rheology of materials in ductile shear zones? A lot depends on how shear zones are initiated. If they are localized by pre-existing structures, width and/or rheology may be inherited, and we have too many variables. If shear zones are localized primarily by shear heating, initial shear stress has to be very high (> 1 GPa) to overcome conductive heat loss, and very large feedbacks (both positive and negative) make the system highly unstable. Microstructural weakening requires a minimum level of stress to cause deformation and damage in surrounding rock, thereby buffering the stress. Microstructural weakening leads to grain-size sensitive creep, for which we have constitutive laws, but these are complicated by phase mixing in polyphase materials, by viscous anisotropy, by hydration, and by changes in mineral assemblage. Here are some questions that need to be addressed. (1) If grain-size reduction by dynamic recrystallization results in a switch to grain-size sensitive creep (GSSC) in a stress-buffered shear zone, does dynamic recrystallization stop? Does grain growth set in? If grain-size is still controlled by dislocation processes, then the effective stress exponent for GSSC is 4-5, even though the dominant mechanism may be diffusion and/or grain-boundary sliding (GBS). (2) Is phase mixing in ultramylonites primarily a result of GBS + neighbour switching, creep cavitation and diffusion, or metamorphic reactions? (3) In two-phase / polyphase mixtures, does the strong phase generally form a load-bearing framework, favoring constant strain-rate (Voigt) bound behavior, or does the weak phase form through-going strain pathways, favoring constant stress (Reuss) bound behavior, or do the phases remain well mixed, favoring an intermediate behavior (e.g., Tullis et al model)? (4) How do we deal with the rheological effect of water? Is it simply an unconstrained variable in nature? Is the water fugacity model in flow laws adequate? (5) How can we better relate experimental results (often carried out at constant strain-rate, and not reaching microstructural steady state) to deformation in natural shear zones? Rheological observations on well-constrained natural shear zones are helping us answer some of these questions.

A study of the trace sulfide mineral assemblages in the Stillwater Complex, Montana, USA

NASA Astrophysics Data System (ADS)

Aird, Hannah M.; Ferguson, Katherine M.; Lehrer, Malia L.; Boudreau, Alan E.

2017-03-01

The sulfide assemblages of the Stillwater Complex away from the well-studied ore zones are composed mainly of variable proportions of pyrrhotite, chalcopyrite, pentlandite, and ±pyrite. Excluding vein assemblages and those affected by greenschist and lower temperature alteration, the majority can be classified into two broad assemblages, defined here as pristine (multiphase, often globular in shape) or volatile-bearing (multiphase, high-temperature, volatile-rich minerals such as biotite, hornblende, or an unmixed calcite-dolomite assemblage). The volatile-bearing assemblages are mainly found within and below the J-M reef, where native copper and sphalerite are also locally present. Pristine sulfides are found throughout the stratigraphy. Both groups can be affected by apparent S loss in the form of pyrite being converted to magnetite and chalcopyrite to a Cu-Fe-oxide (delafossite), with little to no silicate alteration. An upward trend from pentlandite-rich to pyrrhotite-rich to pyrite-rich assemblages is observed in the footwall rocks in upper GN-I, and the same trend repeats from just below the reef and continues into the overlying N-II and GN-II. Modeling suggests that the sulfide Ni in the Peridotite Zone is largely controlled by silicate Ni. When taken together, observations are most readily explained by the remobilization of selected elements by a high-temperature fluid with the apparent loss of S > Cu > Ni. This could concentrate ore metals by vapor refining, eventually producing a platinum group element-enriched sulfide ore zone, such as the J-M reef.

30. BEARING SHOE / VERTICAL / DIAGONAL / UPPER AND ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

30. BEARING SHOE / VERTICAL / DIAGONAL / UPPER AND LOWER CHORD DETAIL OF DECK TRUSS. VIEW TO NORTHEAST. - Abraham Lincoln Memorial Bridge, Spanning Missouri River on Highway 30 between Nebraska & Iowa, Blair, Washington County, NE

Least-cost control of agricultural nutrient contributions to the Gulf of Mexico hypoxic zone.

PubMed

Rabotyagov, Sergey; Campbell, Todd; Jha, Manoj; Gassman, Philip W; Arnold, Jeffrey; Kurkalova, Lyubov; Secchi, Silvia; Feng, Hongli; Kling, Catherine L

2010-09-01

In 2008, the hypoxic zone in the Gulf of Mexico, measuring 20 720 km2, was one of the two largest reported since measurement of the zone began in 1985. The extent of the hypoxic zone is related to nitrogen and phosphorous loadings originating on agricultural fields in the upper Midwest. This study combines the tools of evolutionary computation with a water quality model and cost data to develop a trade-off frontier for the Upper Mississippi River Basin specifying the least cost of achieving nutrient reductions and the location of the agricultural conservation practices needed. The frontier allows policymakers and stakeholders to explicitly see the trade-offs between cost and nutrient reductions. For example, the cost of reducing annual nitrate-N loadings by 30% is estimated to be US$1.4 billion/year, with a concomitant 36% reduction in P and the cost of reducing annual P loadings by 30% is estimated to be US$370 million/year, with a concomitant 9% reduction in nitrate-N.

Fault rocks as indicators of slip behavior

NASA Astrophysics Data System (ADS)

Hayman, N. W.

2017-12-01

Forty years ago, Sibson ("Fault rocks and fault mechanisms", J. Geol. Soc. Lon., 1977) explored plastic flow mechanisms in the upper and lower crust which he attributed to deformation rates faster than tectonic ones, but slower than earthquakes. We can now combine observations of natural fault rocks with insights from experiments to interpret a broad range of length and time scales of fault slip in more detail. Fault rocks are generally weak, with predominantly frictionally stable materials in some fault segments, and more unstable materials in others. Both upper and lower crustal faults contain veins and mineralogical signatures of transiently elevated fluid pressure, and some contain relicts of pseudotachylite and bear other thermal-mechanical signatures of seismic slip. Varying strain rates and episodic-tremor-and-slip (ETS) have been attributed to fault zones with varying widths filled with irregular foliations, veins, and dismembered blocks of varying sizes. Particle-size distributions and orientations in gouge appear to differ between locked and creeping faults. These and other geologic observations can be framed in terms of constitutive behaviors derived from experiments and modeling. The experimental correlation of velocity-dependence with microstructure and the behavior of natural fault-rocks under shear suggest that friction laws may be applied liberally to fault-zone interpretation. Force-chains imaged in stress-sensitive granular aggregates or in numerical simulations show that stick-slip behavior with stress drops far below that of earthquakes can occur during quasi-periodic creep, yet localize shear in larger, aperiodic events; perhaps the systematic relationship between sub-mm shear bands and surrounding gouge and/or cataclasites causes such slip partitioning in nature. Fracture, frictional sliding, and viscous creep can experimentally produce a range of slip behavior, including ETS-like events. Perhaps a similar mechanism occurs to cause ETS at the up-dip limit of faults where water-saturated, highly porous sedimentary aggregates are incorporated into fault zones. Forty years on, fault-rock studies continue to refine a model for fault slip that continuously encompasses the full range of lithospheric depths and seismic to geologic time scales.

An estimation method of the direct benefit of a waterlogging control project applicable to the changing environment

NASA Astrophysics Data System (ADS)

Zengmei, L.; Guanghua, Q.; Zishen, C.

2015-05-01

The direct benefit of a waterlogging control project is reflected by the reduction or avoidance of waterlogging loss. Before and after the construction of a waterlogging control project, the disaster-inducing environment in the waterlogging-prone zone is generally different. In addition, the category, quantity and spatial distribution of the disaster-bearing bodies are also changed more or less. Therefore, under the changing environment, the direct benefit of a waterlogging control project should be the reduction of waterlogging losses compared to conditions with no control project. Moreover, the waterlogging losses with or without the project should be the mathematical expectations of the waterlogging losses when rainstorms of all frequencies meet various water levels in the drainage-accepting zone. So an estimation model of the direct benefit of waterlogging control is proposed. Firstly, on the basis of a Copula function, the joint distribution of the rainstorms and the water levels are established, so as to obtain their joint probability density function. Secondly, according to the two-dimensional joint probability density distribution, the dimensional domain of integration is determined, which is then divided into small domains so as to calculate the probability for each of the small domains and the difference between the average waterlogging loss with and without a waterlogging control project, called the regional benefit of waterlogging control project, under the condition that rainstorms in the waterlogging-prone zone meet the water level in the drainage-accepting zone. Finally, it calculates the weighted mean of the project benefit of all small domains, with probability as the weight, and gets the benefit of the waterlogging control project. Taking the estimation of benefit of a waterlogging control project in Yangshan County, Guangdong Province, as an example, the paper briefly explains the procedures in waterlogging control project benefit estimation. The results show that the waterlogging control benefit estimation model constructed is applicable to the changing conditions that occur in both the disaster-inducing environment of the waterlogging-prone zone and disaster-bearing bodies, considering all conditions when rainstorms of all frequencies meet different water levels in the drainage-accepting zone. Thus, the estimation method of waterlogging control benefit can reflect the actual situation more objectively, and offer a scientific basis for rational decision-making for waterlogging control projects.

Salt-water encroachment, geology, and ground-water resources of Savannah area, Georgia and South Carolina

USGS Publications Warehouse

Counts, H.B.; Donsky, Ellis

1964-01-01

The Savannah area consists of about 2,300 square miles of the Coastal Plain along the coast of eastern Georgia and southeastern South Carolina. Savannah is near the center of the area. Most of the large ground-water developments are in or near Savannah. About 98 percent of the approximately 60 mgd of ground water used is pumped from the principal artesian aquifer, which is composed of about 600 feet of limestone of middle Eocene, Oligocene, and early Miocene ages. Industrial and other wells of large diameter yield as much as 4,200 gpm from the principal artesian aquifer. Pumping tests and flow-net analyses show that the coefficient of transmissibility averages about 200,000 gpd per ft in the immediate Savannah area. The specific capacity of wells in the principal artesian aquifer generally is about 50 gpm per ft of drawdown. The coefficient of storage of the principal artesian aquifer is about 0.0003 in the Savannah area. Underlying the Savannah area are a series of unconsolidated and semiconsolidated sediments ranging in age from Late Cretaceous to Recent. The Upper Cretaceous, Paleocene, and lower Eocene sediments supply readily available and usable water in other parts of the Coastal Plain, but although the character and physical properties of these formations are similar in the Savannah area to the same properties in other areas, the hydraulic and structural conditions appear to be different. Deep test wells are needed to evaluate the ground-water potential of these rocks. The lower part of the sediments of middle Eocene age acts as a confining layer to the vertical movement of water into or out of the principal artesian aquifer. Depending on the location and depth, the principal artesian aquifer consists of from one to five geologic units. The lower boundary of the aquifer is determined by a reduction in permeability and an increase in salt-water content. Although the entire limestone section is considered water bearing, most of the ground water used in the area comes from the upper part of the Ocala limestone of late Eocene age and the limestones of Oligocene age. The greatest volume of water comes from the upper part of the Ocala limestone, but the greatest number of wells are supplied from the rocks of Oligocene age. The Tampa limestone and Hawthorn formation of early Miocene age are generally water bearing; the amount and quality of the water depends on the location. The water from some wells in the Tampa and most of the water from the Hawthorn is high in hydrogen sulfide. In the northeastern part of the area the principal artesian aquifer is close to the land surface. Here the confining layer is thin and in some of the estauaries it may be completely cut through by the scouring action of the streams during tidal fluctuations. In this part of the area artesian groundwater at one time discharged from the aquifer as submarine springs. Now a reverse effect may be occurring; ocean and river water may be entering the aquifer. The silts, clays, and very fine sands of the upper Miocene and Pliocene ( ?) series generally have low permeabilities and form the upper confining layer for the principal artesian aquifer. Although all the sediments overlying the principal artesian aquifer are considered to be part of the confining layer, locally some of the upper units are water bearing. The uppermost geologic units in the Savannah area are sediments of Pliocene ( ?) to Recent age and consist of sands, silts, and clays with shell and gravel beds which are a source of water for shallow wells. The first large ground-water supply from the principal artesian aquifer was developed in 1886 by the city of Savannah. Additional municipal and industrial supplies have been developed since that time. Pumpage progressively increased to a peak of 62 mgd in 1957. Outside of the city and industrial area the 1957 pumpage was about 9 mgd. In 1958 the total pumpage in the Savannah area was about 68 mgd or about 3 mgd less th

Potential for Water Savings by Defoliation of Saltcedar (Tamarix spp.) by Saltcedar Beetles (Diorhabda carinulata) in the Upper Colorado River Basin

NASA Astrophysics Data System (ADS)

Nagler, P. L.; Nguyen, U.; Bateman, H. L.; Jarchow, C.; van Riper, C., III; Waugh, W.; Glenn, E.

2016-12-01

Northern saltcedar beetles (Diorhabda carinata) have spread widely in riparian zones on the Colorado Plateau since their initial release in 2002. One goal of the releases was to reduce water consumption by saltcedar in order to conserve water through reduction of evapotranspiration (ET). The beetle moved south on the Virgin River and reached Big Bend State Park in Nevada in 2014, an expansion rate of 60 km/year. This is important because the beetle's photoperiod requirement for diapause was expected to prevent them from moving south of 37°N latitude, where endangered southwest willow flycatcher habitat occurs. In addition to focusing on the rate of dispersal of the beetles, we used remote sensing estimates of ET at 13 sites on the Colorado, San Juan, Virgin and Dolores rivers and their tributaries to estimate riparian zone ET before and after beetle releases. We estimate that water savings from 2007-2015 was 31.5 million m3/yr (25,547 acre-ft/yr), amounting to 0.258 % of annual river flow from the Upper Colorado River Basin to the Lower Basin. Reasons for the relatively low potential water savings are: 1) baseline ET before beetle release was modest (0.472 m/yr); 2) reduction in ET was low (0.061 m/yr) because saltcedar stands tended to recover after defoliation; 3) riparian ET even in the absence of beetles was only 1.8 % of river flows, calculated as the before beetle average annual ET (472 mm/yr) times the total area of saltcedar (51,588 ha) divided by the combined total average annual flows (1964-2015) from the upper to lower catchment areas of the Colorado River Basin at the USGS gages (12,215 million m3/yr or 9.90 million acre-ft). Further research is suggested to concentrate on the ecological impacts (both positive and negative) of beetles on riparian zones and on identifying management options to maximize riparian health.

Water movement through a thick unsaturated zone underlying an intermittent stream in the western Mojave Desert, southern California, USA

USGS Publications Warehouse

Izbicki, J.A.; Radyk, J.; Michel, R.L.

2000-01-01

Previous studies indicated that small amounts of recharge occur as infiltration of intermittent streamflow in washes in the upper Mojave River basin, in the western Mojave Desert, near Victorville, California. These washes flow only a few days each year after large storms. To reach the water table, water must pass through an unsaturated zone that is more than 130 m thick. Results of this study, done in 1994-1998, showy that infiltration to depths below the root zone did not occur at control sites away from the wash. At these sites, volumetric water contents were as low as 0.01 and water potentials (measured as the combination of solute and matric potentials using a water activity meter) were as negative as -14,000 kPa. Water-vapor movement was controlled by highly negative solute potentials associated with the accumulation of soluble salts in the unsaturated zone. Highly negative matric potentials above and below the zone of maximum solute accumulation result from movement of water vapor toward the highly negative solute potentials at that depth. The ??18O and ??D (delta oxygen-18 and delta deuterium) isotopic composition of water in coarse-grained deposits plots along a Rayleigh distillation line consistent with removal of water in coarse-grained layers by vapor transport. Beneath Oro Grande Wash, water moved to depths below the root zone and, presumably, to the water table about 130 m below land surface. Underneath Oro Grande Wash, volumetric water contents were as high as 0.27 and water potentials (measured as matric potential using tensiometers) were between -1.8 and -50 kPa. On the basis of tritium data, water requires at least 180-260 years to infiltrate to the water table. Clay layers impede the downward movement of water. Seasonal changes in water vapor composition underneath the wash are consistent with the rapid infiltration of a small quantity of water to great depths and subsequent equilibration of vapor with water in the surrounding material. It may be possible to supplement natural recharge from the wash with imported water. Recharge to the wash may be advantageous because the unsaturated zone is not as dry as most areas in the desert and concentrations of soluble salts are generally lower underneath the wash.Previous studies indicated that small amounts of recharge occur as infiltration of intermittent streamflow in washes in the upper Mojave River basin, in the western Mojave Desert, near Victorville, California. These washes flow only a few days each year after large storms. To reach the water table, water must pass through an unsaturated zone that is more than 130 m thick. Results of this study, done in 1994-1998, show that infiltration to depths below the root zone did not occur at control sites away from the wash. At these sites, volumetric water contents were as low as 0.01 and water potentials (measured as the combination of solute and matric potentials using a water activity meter) were as negative as -14,000 kPa. Water-vapor movement was controlled by highly negative solute potentials associated with the accumulation of soluble salts in the unsaturated zone. Highly negative matric potentials above and below the zone of maximum solute accumulation result from movement of water vapor toward the highly negative solute potentials at that depth. The ??18O and ??D (delta oxygen-18 and delta deuterium) isotopic composition of water in coarse-grained deposits plots along a Rayleigh distillation line consistent with removal of water in coarse-grained layers by vapor transport. Beneath Oro Grande Wash, water moved to depths below the root zone and, presumably, to the water table about 130 m below land surface. Underneath Oro Grande Wash, volumetric water contents were as high as 0.27 and water potentials (measured as matric potential using tensiometers) were between -1.8 and -50 kPa. On the basis of tritium data, water requires at least 180-260 years to infiltrate to the water table. Clay layers impede the downwa

Post-depositional behavior of Cu in a metal-mining polishing pond (East Lake, Canada).

PubMed

Martin, Alan J; Jambor, John L; Pedersen, Tom F; Crusius, John

2003-11-01

The post-depositional behavior of Cu in a gold-mining polishing pond (East Lake, Canada) was assessed after mine closure by examination of porewater chemistry and mineralogy. The near-surface (upper 1.5 cm) sediments are enriched in Cu, with values ranging from 0.4 to 2 wt %. Mineralogical examination revealed that the bulk of the Cu inventory is present as authigenic copper sulfides. Optical microscopy, energy-dispersion spectra, and X-ray data indicate that the main Cu sulfide is covellite (CuS). The formation of authigenic Cu-S phases is supported by the porewater data, which demonstrate that the sediments are serving as a sink for dissolved Cu below sub-bottom depths of 1-2 cm. The zone of Cu removal is consistent with the occurrence of detectable sulfide and the consumption of sulfate. The sediments can be viewed as a passive bioreactorthat permanently removes Cu as insoluble copper sulfides. This process is not unlike that which occurs in other forms of bioremediation, such as wetlands and permeable reactive barriers. Above the zone of Cu removal, dissolved Cu maxima in the interfacial porewaters range from 150 to 450 microg L(-1) and reflect the dissolution of a Cu-bearing phase in the surface sediments. The reactive phase is thought to be a component of treatment sludges delivered to the lake as part of cyanide treatment. Flux calculations indicate that the efflux of dissolved Cu from the sediments to the water column (14-51 microg cm(-2) yr(-1)) can account for the elevated levels of dissolved Cu in lake waters (approximately 50 microg L(-1)). Implications for lake recovery are discussed.

Post-Depositional Behavior of Cu in a Metal-Mining Polishing Pond (East Lake, Canada)

USGS Publications Warehouse

Martin, A.J.; Jambor, J.L.; Pedersen, Thomas F.; Crusius, John

2003-01-01

The post-depositional behavior of Cu in a gold-mining polishing pond (East Lake, Canada) was assessed after mine closure by examination of porewater chemistry and mineralogy. The near-surface (upper 1.5 cm) sediments are enriched in Cu, with values ranging from 0.4 to 2 wt %. Mineralogical examination revealed that the bulk of the Cu inventory is present as authigenic copper sulfides. Optical microscopy, energy-dispersion spectra, and X-ray data indicate that the main Cu sulfide is covellite (CuS). The formation of authigenic Cu-S phases is supported by the porewater data, which demonstrate that the sediments are serving as a sink for dissolved Cu below sub-bottom depths of 1-2 cm. The zone of Cu removal is consistent with the occurrence of detectable sulfide and the consumption of sulfate. The sediments can be viewed as a passive bioreactor that permanently removes Cu as insoluble copper sulfides. This process is not unlike that which occurs in other forms of bioremediation, such as wetlands and permeable reactive barriers. Above the zone of Cu removal, dissolved Cu maxima in the interfacial porewaters range from 150 to 450 ??g L-1 and reflect the dissolution of a Cu-bearing phase in the surface sediments. The reactive phase is thought to be a component of treatment sludges delivered to the lake as part of cyanide treatment. Flux calculations indicate that the efflux of dissolved Cu from the sediments to the water column (14-51 ??g cm-2 yr-1) can account for the elevated levels of dissolved Cu in lake waters (???50 ??g L-1). Implications for lake recovery are discussed.

Analysis of flowpath dynamics in a steep unchannelled hollow in the Tanakami Mountains of Japan

NASA Astrophysics Data System (ADS)

Uchida, Taro; Asano, Yuko; Ohte, Nobuhito; Mizuyama, Takahisa

2003-02-01

Simultaneous measurements of runoff, soil pore water pressure, soil temperature, and water chemistry were taken to evaluate the spatial and temporal nature of flowpaths in a steep 0·1 ha unchannelled hollow in the Tanakami Mountains of central Japan. Tensiometers showed that a saturated area formed and a downward hydraulic gradient existed continuously in the area near a spring. The amplitude of the soil-bedrock interface temperature difference near the spring was smaller than that in the upper hollow, although soil depth near the spring was smaller than in the upper hollow. This suggests that, in the small perennially saturated area near the spring, water percolates through the vadose zone mixed with water emerging from the bedrock. During summer rainstorms, the soil-bedrock interface temperature increased as the ground became saturated. Silica and sodium concentrations in the transient saturated groundwater during these episodes were significantly lower than those in the perennial groundwater, suggesting that both rainwater and shallow soil water had important effects on the formation of transient saturated groundwater on the upper slope. In this case, the streamflow varied with the soil pore water pressure on the upper slope; the soil pore water pressure in the area near the spring remained nearly constant. Moreover, the spring water temperature was almost the same as the transient groundwater temperature on the upper slope. This indicates that the transient groundwater in the upper slope flowed to the spring via lateral preferential paths. The relative inflow of bedrock groundwater to the spring decreased as rainfall increased.

Evaluation of geophysical logs and video surveys in boreholes adjacent to the Berkley Products Superfund Site, West Cocalico Township, Lancaster County, Pennsylvania

USGS Publications Warehouse

Low, Dennis J.; Conger, Randall W.

1998-01-01

Between February 1998 and April 1998, geophysical logs were collected in nine boreholes adjacent to the Berkley Products Superfund Site, West Cocalico Township, Lancaster County, Pa. Video surveys were conducted on four of the nine boreholes. The boreholes range in depth from 320 to 508 feet below land surface, are completed open holes, have ambient vertical flow of water, and penetrate a series of interbedded siltstone, sandstone, and conglomerate units. The purpose of collecting geophysical-log data was to help determine horizontal and vertical distribution of contaminated ground water migrating from known or suspected sources and to aid in the placement of permanent borehole packers. The primary contaminants were derived from paint waste that included pigment sludges and wash solvents. The chlorinated volatile organic compounds probably originated from the wash solvents.Caliper logs and video surveys were used to locate fractures; inflections on fluid-resistivity and fluid-temperature logs were used to locate possible water-bearing fractures. Heatpulse-flowmeter measurements were used to verify the locations of water-producing or water-receiving zones and to measure rates of flow between water-bearing fractures. Single-point-resistance and natural-gamma logs provided information on stratigraphy. After interpretation of geophysical logs, video surveys, and driller's logs, permanent multiple-packer systems were installed in each borehole to obtain depth specific water samples from one or more water-bearing fractures in each borehole.

3D mapping, hydrodynamics and modelling of the freshwater-brine mixing zone in salt flats similar to the Salar de Atacama (Chile)

NASA Astrophysics Data System (ADS)

Marazuela, M. A.; Vázquez-Suñé, E.; Custodio, E.; Palma, T.; García-Gil, A.; Ayora, C.

2018-06-01

Salt flat brines are a major source of minerals and especially lithium. Moreover, valuable wetlands with delicate ecologies are also commonly present at the margins of salt flats. Therefore, the efficient and sustainable exploitation of the brines they contain requires detailed knowledge about the hydrogeology of the system. A critical issue is the freshwater-brine mixing zone, which develops as a result of the mass balance between the recharged freshwater and the evaporating brine. The complex processes occurring in salt flats require a three-dimensional (3D) approach to assess the mixing zone geometry. In this study, a 3D map of the mixing zone in a salt flat is presented, using the Salar de Atacama as an example. This mapping procedure is proposed as the basis of computationally efficient three-dimensional numerical models, provided that the hydraulic heads of freshwater and mixed waters are corrected based on their density variations to convert them into brine heads. After this correction, the locations of lagoons and wetlands that are characteristic of the marginal zones of the salt flats coincide with the regional minimum water (brine) heads. The different morphologies of the mixing zone resulting from this 3D mapping have been interpreted using a two-dimensional (2D) flow and transport numerical model of an idealized cross-section of the mixing zone. The result of the model shows a slope of the mixing zone that is similar to that obtained by 3D mapping and lower than in previous models. To explain this geometry, the 2D model was used to evaluate the effects of heterogeneity in the mixing zone geometry. The higher the permeability of the upper aquifer is, the lower the slope and the shallower the mixing zone become. This occurs because most of the freshwater lateral recharge flows through the upper aquifer due to its much higher transmissivity, thus reducing the freshwater head. The presence of a few meters of highly permeable materials in the upper part of these hydrogeological systems, such as alluvial fans or karstified evaporites that are frequently associated with the salt flats, is enough to greatly modify the geometry of the saline interface.

Monitoring regional effects of high pressure injection of wastewater in a limestone aquifer

USGS Publications Warehouse

Faulkner, Glen L.; Pascale, Charles A.

1975-01-01

More than 10 billion gallons (38 × 106 m3) of acid industrial liquid waste has been injected in about 11 years under high pressure into a saline-water-filled part of a limestone aquifer of low transmissivity between 1,400 and 1,700 feet (430 and 520 m) below land surface near Pensacola, Florida. A similar waste disposal system is planned for the same zone at a site about 8.5 miles (13.7 km) to the east. The injection zone is the lower limestone of the Floridan aquifer. The lower limestone is overlain by a confining layer of plastic clay about 220 feet (67 m) thick at the active injection site and underlain by another confining layer of shale and clay. The upper confining layer is overlain by the upper limestone of the Floridan aquifer.The active injection system consists of two injection wells about a quarter of a mile (0.4 km) apart and three monitor wells. Two of the monitor wells (deep monitors) are used to observe hydraulic and geochemical effects of waste injection in the injection zone at locations about 1.5 miles (2.4 km) south and 1.9 miles (3.1 km) north of the center of the injection site. The third well (shallow monitor), used to observe any effects in the upper limestone, is about 100 feet (30 m) from one of the injection wells. Since 1972 the injection zone has also been monitored at a test well at the planned new injection site. Three more monitor wells in the injection zone were activated in early 1974 at sites 17 miles (27 km) northeast, 22 miles (35 km) east and 33 miles (53 km) northeast of the injection site. The six deep monitors provide a system for evaluating the regional effects of injecting wastes. No change in pressure or water quality due to injection was, by mid-1974, evident in the upper limestone at the injection site, but static pressures in the lower limestone at the site had increased 8 fold since injection began in 1963. Chemical analyses indicated probable arrival of the diluted waste at the south monitor well in 1973. By mid-1974 waste evidently had not reached the north monitor well.Calculations indicate that by mid-1974 pressure effects from waste injection extended radially more than 40 miles (64 km) from the injection site. By mid-1974 pressure effects of injection were evident from water-level measurements made at the five deep monitor wells nearest the active injection site. No effects were recognized at the well 33 miles (53 km) away. Less than 20 miles (32 km) northeast of the active injection site, the lower limestone contains fresh water. Changes in the pressure regime due to injection indicate a tendency for northeastward movement of the fresh-water/salt-water interface in the lower limestone.

A search for water on the moon at the Reiner Gamma Formation - A possible site of cometary coma impact

NASA Technical Reports Server (NTRS)

Roush, Ted L.; Lucey, Paul G.

1988-01-01

Earth-based telescopic measurements of the Reiner Gamma Formation in the 3-micron region were made to search for evidence of water at this proposed site of cometary interaction with the lunar surface. Comparison of the spectra of Reiner Gamma and laboratory measurements of a variety of minerals with adsorbed water or structural OH(-) show that there is no evidence for water at the locations measured. While these measurements rule out the presence of abundant bound H2O at these locations, they do not exclude the presence of OH(-) bearing minerals that have absorptions not detectable through the wet terrestrial atmosphere. The possible effects of high lunar temperatures on the reflectance spectra were examined, and it was concluded that these effects would not obscure a bound water absorption if it were present. Upper limits on the amount of water that could be present at the locations observed and remain undetected are 2.25 average wt pct for a mixture consisting of discrete patches of water-bearing and water-free minerals and 0.01 wt pct for an intimate mixture of these two materials.

Dehydration-driven stress transfer triggers intermediate-depth earthquakes

NASA Astrophysics Data System (ADS)

Ferrand, T. P.; Schubnel, A.; Hilairet, N.; Incel, S.; Deldicque, D.; Labrousse, L.; Gasc, J.; Renner, J.; Wang, Y.; Green, H. W., II

2016-12-01

Intermediate-depth earthquakes (30-300 km) have been extensively documented within subducting oceanic slabs but their physical mechanisms remain enigmatic. Earthquakes occur both in the upper and lower Wadati-Benioff planes of seismicity (UBP and LBP). The LBP is located in the mantle of the subducted oceanic lithosphere, 20-40 km below the plate interface. Several mechanisms have been proposed: dehydration embrittlement of antigorite, shear heating instabilities, and the reactivation of pre-existing shear zones. We dehydrated synthetic antigorite-olivine aggregates, a proxy for serpentinized mantle, during deformation at upper mantle conditions. Acoustic emissions (AEs) were recorded during dehydration of samples with antigorite contents as low as 5 vol.% and with up to 50 vol.%, deformed at pressures of 1.1 GPa and 3.5 GPa, respectively. Source characteristics of these AEs are compatible with faults sealed by fluid-bearing micro-pseudotachylytes in recovered samples, demonstrating that antigorite dehydration triggered dynamic shear failure of the olivine load-bearing network. These intermediate-depth earthquake analogs reconcile the apparent contradictions of previous laboratory studies and confirm that little mantle hydration, as suggested by seismic imaging, may suffice to generate LBP seismicity. We propose an alternative model to dehydration-embrittlement in which dehydration-induced stress transfer, rather than fluid overpressure, is the trigger of mantle rocks embrittlement.

[Correlation analysis between residual displacement and hip function after reconstruction of acetabular fractures].

PubMed

Ma, Kunlong; Fang, Yue; Luan, Fujun; Tu, Chongqi; Yang, Tianfu

2012-03-01

To investigate the relationships between residual displacement of weight-bearing and non weight-bearing zones (gap displacement and step displacement) and hip function by analyzing the CT images after reconstruction of acetabular fractures. The CT measures and clinical outcome were retrospectively analyzed from 48 patients with displaced acetabular fracture between June 2004 and June 2009. All patients were treated by open reduction and internal fixation, and were followed up 24 to 72 months (mean, 36 months); all fractures healed after operation. The residual displacement involved the weight-bearing zone in 30 cases (weight-bearing group), and involved the non weight-bearing zone in 18 cases (non weight-bearing group). The clinical outcomes were evaluated by Merle d'Aubigné-Postel criteria, and the reduction of articular surface by CT images, including the maximums of two indexes (gap displacement and step displacement). All the data were analyzed in accordance with the Spearman rank correlation coefficient analysis. There was strong negative correlation between the hip function and the residual displacement values in weight-bearing group (r(s) = -0.722, P = 0.001). But there was no correlation between the hip function and the residual displacement values in non weight-bearing group (r(s) = 0.481, P = 0.059). The results of clinical follow-up were similar to the correlation analysis results. In weight-bearing group, the hip function had strong negative correlation with step displacement (r(s) = 0.825, P = 0.002), but it had no correlation with gap displacement (r(s) = 0.577, P = 0.134). In patients with acetabular fracture, the hip function has correlation not only with the extent of the residual displacement but also with the location of the residual displacement, so the residual displacement of weight-bearing zone is a key factor to affect the hip function. In patients with residual displacement in weight-bearing zone, the bigger the step displacement is, the worse the hip function is.

Experimental Study on the Coupling Mechanism of Early-strength Backfill and Rock

NASA Astrophysics Data System (ADS)

Wang, Mingxu

2017-11-01

In order to study the interaction mechanism between the ore rock and backfill at the early stage, paraffin is chosen as the cementing agent. Based on the damage mechanics and fractal theory, the interaction mechanism between the ore rock and backfill is characterized by the relevant tests on the complex of proportioned ore rock and backfill with resistance strain gauge, crack propagation, microscopic imaging and AE. The experimental results showed that: 1) Through the axial loading test, compared with the early strength of the cemented filling and paraffin mechanical deformation characteristics, the stress and strain curves of the two had a common linear deformation law, while in the early strength of the filling elastic capacity strong, with a certain degree of resilience. 2) The bearing capacity of the backfill was weak, but the deformation ability was strong. During the bearing process, the deformation of the upper load was mainly caused by the ore rock, which leaded to the damage of the rock. 3) The distribution of AE points during the co-carrying of the filling and the ore rock was monitored by the acoustic emission instrument. The damage occurred mainly in the contact zone between the backfill and the ore rock zone. The corresponding AE point distribution also validated the crack happening.

Water partitioning in the Earth's mantle

NASA Astrophysics Data System (ADS)

Inoue, Toru; Wada, Tomoyuki; Sasaki, Rumi; Yurimoto, Hisayoshi

2010-11-01

We have conducted H2O partitioning experiments between wadsleyite and ringwoodite and between ringwoodite and perovskite at 1673 K and 1873 K, respectively. These experiments were performed in order to constrain the relative distribution of H2O in the upper mantle, the mantle transition zone, and the lower mantle. We successfully synthesized coexisting mineral assemblages of wadsleyite-ringwoodite and ringwoodite-perovskite that were large enough to measure the H2O contents by secondary ion mass spectrometry (SIMS). Combining our previous H2O partitioning data (Chen et al., 2002) with the present results, the determined water partitioning between olivine, wadsleyite, ringwoodite, and perovskite under H2O-rich fluid saturated conditions are 6:30:15:1, respectively. Because the maximum H2O storage capacity in wadsleyite is ∼3.3 wt% (e.g. Inoue et al., 1995), the possible maximum H2O storage capacity in the olivine high-pressure polymorphs are as follows: ∼0.7 wt% in olivine (upper mantle just above 410 km depth), ∼3.3 wt% in wadsleyite (410-520 km depth), ∼1.7 wt% in ringwoodite (520-660 km depth), and ∼0.1 wt% in perovskite (lower mantle). If we assume ∼0.2 wt% of the H2O content in wadsleyite in the mantle transition zone estimated by recent electrical conductivity measurements (e.g. Dai and Karato, 2009), the estimated H2O contents throughout the mantle are as follows; ∼0.04 wt% in olivine (upper mantle just above 410 km depth), ∼0.2 wt% in wadsleyite (410-520 km depth), ∼0.1 wt% in ringwoodite (520-660 km depth) and ∼0.007 wt% in perovskite (lower mantle). Thus, the mantle transition zone should contain a large water reservoir in the Earth's mantle compared to the upper mantle and the lower mantle.

Vertical flow chemical detection portal

DOEpatents

Linker, K.L.; Hannum, D.W.; Conrad, F.J.

1999-06-22

A portal apparatus is described for screening objects or persons for the presence of trace amounts of chemical substances such as illicit drugs or explosives. The apparatus has a test space, in which a person may stand, defined by two generally upright sides spanned by a horizontal transom. One or more fans in the transom generate a downward air flow (uni-directional) within the test space. The air flows downwardly from a high pressure upper zone, past the object or person to be screened. Air moving past the object dislodges from the surface thereof both volatile and nonvolatile particles of the target substance. The particles are entrained into the air flow which continues flowing downward to a lower zone of reduced pressure, where the particle-bearing air stream is directed out of the test space and toward preconcentrator and detection components. The sides of the portal are specially configured to partially contain and maintain the air flow. 3 figs.

Vertical flow chemical detection portal

DOEpatents

Linker, Kevin L.; Hannum, David W.; Conrad, Frank James

1999-01-01

A portal apparatus for screening objects or persons for the presence of trace amounts of chemical substances such as illicit drugs or explosives. The apparatus has a test space, in which a person may stand, defined by two generally upright sides spanned by a horizontal transom. One or more fans in the transom generate a downward air flow (uni-directional) within the test space. The air flows downwardly from a high pressure upper zone, past the object or person to be screened. Air moving past the object dislodges from the surface thereof both volatile and nonvolatile particles of the target substance. The particles are entrained into the air flow which continues flowing downward to a lower zone of reduced pressure, where the particle-bearing air stream is directed out of the test space and toward preconcentrator and detection components. The sides of the portal are specially configured to partially contain and maintain the air flow.

Geochemical and isotopic composition of ground water with emphasis on sources of sulfate in the upper Floridan Aquifer and intermediate aquifer system in southwest Florida

USGS Publications Warehouse

Sacks, Laura A.; Tihansky, Ann B.

1996-01-01

In southwest Florida, sulfate concentrations in water from the Upper Floridan aquifer and overlying intermediate aquifer system are commonly above 250 milligrams per liter (the drinking water standard), particularly in coastal areas. Possible sources of sulfate include dissolution of gypsum from the deeper part of the Upper Floridan aquifer or the middle confining unit, saltwater in the aquifer, and saline waters from the middle confining unit and Lower Floridan aquifer. The sources of sulfate and geochemical processes controlling ground-water composition were evaluated for the Peace and Myakka River Basins and adjacent coastal areas of southwest Florida. Samples were collected from 63 wells and a saline spring, including wells finished at different depth intervals of the Upper Floridan aquifer and intermediate aquifer system at about 25 locations. Sampling focused along three ground-water flow paths (selected based on a predevelopment potentiometric-surface map). Ground water was analyzed for major ions, selected trace constituents, dissolved organic carbon, and stable isotopes (delta deuterium, oxygen-18, carbon-13 of inorganic carbon, and sulfur-34 of sulfate and sulfide); the ratio of strontium-87 to strontium-86 was analyzed for waters along one of the flow paths. Chemical and isotopic data indicate that dedolomitization reactions (gypsum and dolomite dissolution and calcite precipitation) control the chemical composition of water in the Upper Floridan aquifer in inland areas. This is confirmed by mass-balance modeling between wells in the shallowest interval in the aquifer along the flow paths. However, gypsum occurs deeper in the aquifer than these wells. Upwelling of sulfate-rich water that previously dissolved gypsum in deeper parts of the aquifer is a more likely source of sulfate than gypsum dissolution in shallow parts of the aquifer. This deep ground water moves to shallower zones in the aquifer discharge area. Saltwater from the Upper Floridan aquifer has not dissolved significant amounts of gypsum compared to fresher water in the aquifer. This is consistent with a shallow seawater source for the saltwater, rather than a deeper source from the underlying middle confining unit or Lower Floridan aquifer, which would have elevated sulfate concentrations. Ion exchange and dolomitization may be important reactions for saltwater in the aquifer. According to geochemical modeling, the freshwater end member for water in the saltwater mixing zone in the southwestern part of the study area is not upgradient water from the Upper Floridan aquifer that dissolved gypsum. Instead, this water appears to be isolated from the regional freshwater flow system and may be part of a more localized flow system. The chemical and isotopic composition of water in the intermediate aquifer system is controlled by differences in extent of reactions with aquifer minerals, upward leakage from the Upper Floridan aquifer, and saltwater mixing. In inland areas, water generally is characterized by relatively low sulfate concentrations (less than 250 milligrams per liter) and differences in extent of carbonate mineral dissolution. Some inland waters have elevated chloride concentrations, which may be related to evaporation prior to recharge. In coastal Sarasota County and in isolated inland areas, water from the intermediate aquifer system has high sulfate concentrations characteristic of dedolomitization waters from the Upper Floridan aquifer. The chemical and isotopic composition of these waters is controlled by upward leakage from the Upper Floridan aquifer, which naturally occurs in the discharge area but may be locally enhanced by pumping or interconnection of wells open to both aquifer systems. In western Charlotte County, the waters are dominated by sodium and chloride, and their compositions are consistent with mixing between saltwater and inland intermediate aquifer system water that has not been influenced by discharge from the

UNDERSTANDING HARD ROCK HYDROGEOLOGY THROUGH AN EXPERIMENTAL HYDROGEOLOGICAL PARK IN SOUTH INDIA: Site development and investigations on the major role of the fractured zone in crystalline aquifers

NASA Astrophysics Data System (ADS)

Ahmed, S.; Guiheneuf, N.; Boisson, A.; Marechal, J.; Chandra, S.; Dewandel, B.; Perrin, J.

2012-12-01

In water stressed south India most of the groundwater used for irrigation is pumped from crystalline rocks aquifers. In those structures groundwater flow dominantly occur in a shallow higher-permeability zone that overlies a deeper lower-permeability zone hosting little flow. The fractured zone of the weathering profile plays an important role for groundwater. In order to understand clearly this impact on water availability and quality changes the Experimental Hydrogeological Park at Choutuppal, Andhra Pradesh, India is developed in the framework of the SORE H+ network. Several hydraulic tests (injection, flowmeter profiles, single-packer tests…) and geophysical measurements (ERT, Borehole logging…) are carried out on the site in order to characterize the depth-dependence of hydrodynamic parameters in the Indian Archean granite. Specific investigation on a borewell through packer tests demonstrate that the most conductive part of the aquifer corresponds to the upper part of the fractured layer, located just below the saprolite bottom, between 15 meters and 20 meters depth. There is no highly conductive fracture beyond 20 meters depth and no indication for any conductive fracture beyond 25 meters depth. Packer tests show that the upper part of the fractured layer (15-20 m depth) is characterized by a good vertical connectivity. On the contrary, the tests carried out below 20 m depth show no vertical connectivity at all. The geometry of the fracture network and associated hydrodynamic parameters are in agreement with the conceptual model of hard-rock aquifers that derive its properties from weathering processes. The general existence of such a highly conductive structure at the top of the fractured zone has a great impact on water prospection and exploitation in such crystalline aquifers.

From Black Hole to Hydrate Hole: Gas hydrates, authigenic carbonates and vent biota as indicators of fluid migration at pockmark sites of the Northern Congo Fan

NASA Astrophysics Data System (ADS)

Kasten, S.; Schneider, R.; Spiess, V.; Cruise Participants Of M56b

2003-04-01

A recent high-resolution seismic, echosounder and video survey combined with detailed geological and geochemical sampling of pockmark sites on the Northern Congo Fan was carried out with RV Meteor in November/December 2002 in the frame of the project "CONGO" (BMBF/BEO "Geotechnologien"). These investigations revealed the extensive occurrence of surface and sub-surface gas hydrates as well as characteristic features of fluid venting such as clams (Calyptogena), tube worms (Pogonophera) and huge amounts of authigenic carbonates. In a first approach the patchyness in the occurrence of these features was mapped in relation to pockmark structure and seismic reflectors. Detailed sampling of three pockmarks by gravity corer showed that gas hydrates are present at and close to the sediment surface and often occur as several distinct layers and/or veins intercalated with hemipelagic muds. The depth of the upper boundary of these hydrate-bearing sediments increases from the center towards the edge of the pockmark structures. Pore water concentration profiles of sulfate and methane document the process of anaerobic methane oxidation above the hydrate-bearing layers. For those cores which contained several gas hydrate layers preliminary pore water profiles suggest the occurrence of more than one zone of anaerobic methane oxidation. Authigenic carbonates are found in high abundance, irregularly distributed within the pockmarks close to the sediment surface. These carbonates occur in a wide variety with respect to size, shape, structure and mineralogy. Their formation is associated with high amounts of bicarbonate released by the process of anaerobic methane oxidation. In the gravity cores authigenic carbonates are always present above hydrate-bearing sections. However, the quantities and characteristics of these authigenic minerals in relation to venting and microbial activity as well as to gas hydrate dissociation are not clear yet. Unraveling this relationship will be a major target of further investigation. By means of detailed studies of the sedimentary solid-phase, authigenic carbonates, clam layers and molecular biomarkers we will also try to reconstruct the history of venting and the dynamics of gas hydrate formation and decomposition in the Northern Congo fan area.

Delineation and description of the regional aquifer systems of Tennessee; Cumberland Plateau aquifer system

USGS Publications Warehouse

Brahana, J.V.; Macy, J.A.; Mulderink, Dolores; Zemo, Dawn

1986-01-01

The Cumberland Plateau aquifer system consists of Pennsylvanian sandstones, conglomerates, shales, and coals which underlie the Cumberland Plateau in Tennessee. Major water-bearing zones occur within the sandstones and conglomerates in interconnected fractures. The water-bearing formations are separated by shale and siltstone that retard the vertical circulation of ground water, The Pennington Formation serves as the base of this aquifer system and is an effective confining unit, The Cumberland Plateau aquifer system is an important water source for the Cumberland Plateau, wells and springs from the aquifer system supply most of the rural domestic and public drinking-water supplies, water from wells drilled into the Cumberland Plateau aquifer system is generally of good to excellent quality. Of the 32 water-quality analyses on file from this aquifer. only 2 had dissolved-solids concentrations greater than 500 milligrams per liter, and about three-fourths had less than 200 milligrams per liter dissolved solids, However, no samples from depths greater than 300 feet below land surface have been recorded. Ground water from locations where the sandstones are buried deeply, such as the Wartburg basin, may contain dissolved-solids concentrations greater than 1,000 milligrams per liter.

Preliminary delineation and description of the regional aquifers of Tennessee : Cumberland Plateau aquifer system

USGS Publications Warehouse

Brahana, J.V.; Macy, Jo Ann; Mulderink, Dolores; Zemo, Dawn

1986-01-01

The Cumberland Plateau aquifer system consists of Pennsylvanian sandstones, conglomerates, shales, and coals which underlie the Cumberland Plateau in Tennessee. Major water-bearing zones occur within the sandstones and conglomerates in interconnected fractures. The water-bearing formations are separated by shale and siltstone that retard the vertical circulation of ground water. The Pennington Formation serves as the base of this aquifer system and is an effective confining unit. The Cumberland Plateau aquifer system is an important water source for the Cumberland Plateau. Wells and springs from the aquifer system supply most of the rural domestic and public drinking-water supplies. Water from wells drilled into the Cumberland Plateau aquifer system is generally of good to excellent quality. Of the 32 water-quality analyses on file from this aquifer, only 2 had dissolved-solids concentrations greater than 500 milligrams per liter, and about three-fourths had less than 200 milligrams per liter dissolved solids. However, no samples from depths greater than 300 feet below land surface have been recorded. Ground water from locations where the sandstones are buried deeply, such as the Wartburg basin, may contain dissolved-solids concentrations greater than 1,000 milligrams per liter.

Permian macro- and miofloral diversity, palynodating and palaeoclimate implications deduced from the coal-bearing sequences of Singrauli coalfield, Son-Mahanadi Basin, central India

NASA Astrophysics Data System (ADS)

Singh, Kamal Jeet; Murthy, Srikanta; Saxena, Anju; Shabbar, Husain

2017-03-01

The coal-bearing sequences of Barakar and Raniganj formations exposed in Bina and Jhingurdah open-cast collieries, respectively, are analysed for their macro- and miofloral content. The sediment successions primarily comprise of sandstones, shales, claystones and coal seams. In addition to the diverse glossopterid assemblage, four palynoassemblage zones, namely Zones I and II in Bina Colliery and Zones III and IV in Jhingurdah Colliery, have also been recorded in the present study. The megafossil assemblage from the Barakar strata of Bina Colliery comprises of three genera, namely Gangamopteris, Glossopteris and cf. Noeggerathiopsis. Palynoassemblage-I is characterised by the dominance of non-striate bisaccate pollen genus Scheuringipollenites and subdominance of striate bisaccate Faunipollenites and infers these strata to be of Early Permian (Artinskian) age (Lower Barakar Formation). The palynoassemblage has also yielded a large number of naked fossil spore tetrads, which is the first record of spore tetrads from any Artinskian strata in the world and has a significant bearing on the climatic conditions. The palynoassemblage-II is characterised with the dominance of Faunipollenites over Scheuringipollenites and is indicative of Kungurian age (Upper Barakar Formation). The megafossil assemblage from the Raniganj Formation of Jhingurdah Colliery comprises of five genera with 26 species representing four orders, viz., Equisetales, Cordaitales, Cycadales and Glossopteridales. The order Glossopteridales is highly diversified with 23 taxa and the genus Glossopteris, with 22 species, dominates the flora. The mioflora of this colliery is represented by two distinct palynoassemblages. The palynoassemblage-III is correlatable with the palynoflora of Early Permian (Artinskian) Lower Barakar Formation. The assemblage suggests the continuity of older biozones into the younger ones. The palynoassemblage-IV equates the beds with composition V: Striatopodocarpites-Faunipollenites-Gondisporites assemblage zone of Tiwari and Tripathi (1992) of Late Permian (Lopingian) Raniganj Formation in Damodar Basin. The FAD's of Alisporites, Klausipollenites, Falcisporites, Arcuatipollenites pellucidus and Playfordiaspora cancellosa palynotaxa in this assemblage enhance the end Permian level of the Jhingurdah Top seam, as these elements are the key species to mark the transition of Permian into the Lower Triassic.

Transmissivity and water quality of water-producing zones in the intermediate aquifer system, Sarasota County, Florida

USGS Publications Warehouse

Knochenmus, L.A.; Bowman, Geronia

1998-01-01

The intermediate aquifer system is an important water source in Sarasota County, Florida, because the quality of water in it is usually better than that in the underlying Upper Floridan aquifer. The intermediate aquifer system consists of a group of up to three water-producing zones separated by less-permeable units that restrict the vertical movement of ground water between zones. The diverse lithology, that makes up the intermediate aquifer system, reflects the variety of depositional environments that occurred during the late Oligocene and Miocene epochs. Slight changes in the depositional environment resulted in aquifer heterogeneity, creating both localized connection between water-producing zones and abrupt culmination of water-producing zones that are not well documented. Aquifer heterogeneity results in vertical and areal variability in hydraulic and water-quality properties. The uppermost water-producing zone is designated producing zone 1 but is not extensively used because of its limited production capability and limited areal extent. The second water-producing zone is designated producing zone 2, and most of the domestic- and irrigation-supply wells in the area are open to this zone. Additionally, producing zone 2 is utilized for public supply in southern coastal areas of Sarasota County. Producing zone 3 is the lowermost and most productive water-producing zone in the intermediate aquifer system. Public-supply well fields serving the cities of Sarasota and Venice, as well as the Plantation and Mabry Carlton Reserve well fields, utilize producing zone 3. Heads within the intermediate aquifer system generally increase with aquifer depth. However, localized head-gradient reversals occur in the study area, coinciding with sites of intense ground-water withdrawals. Heads in producing zones 1, 2, and 3 range from 1 to 23, 0.2 to 34, and 7 to 42 feet above sea level, respectively. Generally, an upward head gradient exists between producing zones 3 and 2. However, an upward head gradient between producing zones 2 and 1 does not consistently occur throughout Sarasota County, probably the result of greater ground-water withdrawals from producing zone 2 than from producing zone 1. The transmissivity of the intermediate aquifer system is spatially variable. Specific-capacity data from selected wells penetrating producing zones 2 and 3, were used to estimate transmissivity. Estimated transmissivity values for producing zones 2 and 3 range from about 100 to 26,000 feet squared per day and from about 1,300 to 6,200 feet squared per day, respectively. Because the capacity of specific water-producing zones is highly variable from site to site, estimating the performance of a specific water-producing zone as a water resource is difficult. Water samples collected during the study were analyzed for major-ion concentrations. Generally, bicarbonate type water from rock interaction occurs in northern Sarasota County; enriched calcium-magnesium-sulfate type water from deeper aquifers occurs in central Sarasota County; and sodium-chloride type water from saltwater mixing occurs in southern Sarasota County. In some areas of northern Sarasota County, the major-ion concentrations in water are lower in producing zone 2 than in producing zone 1. Major-ion concentrations in water are higher in producing zone 3 throughout the study area. A major objective of the study was to evaluate hydraulic and water-quality data to determine distinctions that could be used to characterize a particular producing zone. However, data indicate that both hydraulic and water-quality properties are highly variable within and between zones, and are more related to the degree of connection between and areal extent of water-producing zones than to aquifer depth and distance from the coast.

Bear-inflicted injuries - a report from Nepal.

PubMed

Atreya, Alok; Kanchan, Tanuj; Nepal, Samata; Acharya, Jenash

2016-06-01

Upper Mustang in the Northern Himalayan range of Nepal is the home of brown bears (Ursusarctos). Low-plant biomass as a result of scanty rainfall in Upper Mustang is a reason for habitat overlap of humans and wild animals. Humans who enter into the wild to collect firewood and graze cattle are liable to wild animal attacks. Such attacks, especially by brown bears, are readily identified by the type of injuries. These are more commonly confined to head and neck regions. Cutting, gnawing and tearing by sharp teeth and claws produces specific pattern of injuries, which are devastating but seldom fatal. This article reports a rare case of brown bear injury inflicted upon a man from the Upper Mustang region in Nepal. © The Author(s) 2016.

Evaluation of geophysical logs, Phase II, at Willow Grove Naval Air Station Joint Reserve Base, Montgomery County, Pennsylvania

USGS Publications Warehouse

Conger, Randall W.

1999-01-01

Between March and April 1998, the U.S. Navy contracted Tetra Tech NUS Inc., to drill two monitor wells in the Stockton Formation at the Willow Grove Naval Air Station Joint Reserve Base, Horsham Township, Montgomery County, Pa. The wells MG-1634 and MG-1635 were installed to monitor water levels and sample contaminants in the shallow, intermediate, and deep water-producing zones of the fractured bedrock. Chemical analyses of the samples will help determine the horizontal and vertical distribution of any contaminated ground water migrating from known contaminant sources. Wells were drilled near the Fire Training Area (Site 5). Depths of all boreholes range from 69 to 149 feet below land surface. The U.S. Geological Survey conducted borehole geophysical logging and video surveys to identify water-producing zones in newly drilled monitor wells MG-1634 and MG-1635 and in wells MG-1675 and MG-1676. The logging was conducted from March 5, 1998, to April 16, 1998. This work is a continuation of the Phase I work. Caliper logs and video surveys were used to locate fractures; inflections on fluid-temperature and fluid-resistivity logs were used to locate possible water-producing fractures. Heatpulse-flowmeter measurements were used to verify the locations of water-producing or water-receiving zones and to measure rates of flow between water-bearing fractures. Single-point-resistance and natural-gamma logs provided information on stratigraphy. After interpretation of geophysical logs, video surveys, and driller's notes, wells MG-1634 and MG-1635 were screened such that water-levels fluctuations could be monitored and discrete water samples collected from one or more water-producing zones in each borehole.

The Pennsylvanian-early permian bird spring carbonate shelf, Southeastern California: Fusulinid biostratigraphy, paleogeographic evolution, and tectonic implications

USGS Publications Warehouse

Stevens, C.H.; Stone, P.

2007-01-01

The Bird Spring Shelf in southeastern California, along with coeval turbidite basins to the west, records a complex history of late Paleozoic sedimentation, sea-level changes, and deformation along the western North American continental margin. We herein establish detailed correlations between deposits of the shelf and the flanking basins, which we then use to reconstruct the depositional history, paleogeography, and deformational history, including Early Permian emplacement of the regionally significant Last Chance allochthon. These correlations are based on fusulinid faunas, which are numerous both on the shelf and in the adjoining basins. Study of 69 fusulinid species representing all major fusulinid-bearing Pennsylvanian and Lower Permian limestone outcrops of the Bird Spring Shelf in southeastern California, including ten new species of the genera Triticites, Leptotriticites, Stewartina, Pseudochusenella, and Cuniculinella, forms the basis for our correlations. We group these species into six fusulinid zones that we correlate with fusulinid-bearing strata in east-central and southern Nevada, Kansas, and West Texas, and we propose some regional correlations not previously suggested. In addition, we utilize recent conodont data from these areas to correlate our Early Permian fusulinid zones with the standard Global Permian Stages, strengthening their chronostratigraphic value. Our detailed correlations between the fusulinid-bearing rocks of the Bird Spring Shelf and deep-water deposits to the northwest reveal relationships between the history of shelf sedimentation and evolution of basins closer to the continental margin. In Virgilian to early Asselian (early Wolfcampian) time (Fusulinid Zones 1 and 2), the Bird Spring Shelf was flanked on the west by the deep-water Keeler Basin in which calcareous turbidites derived from the shelf were deposited. In early Sakmarian (early middle Wolfcampian) time (Fusulinid Zone 3), the Keeler Basin deposits were uplifted and transported eastward on the Last Chance thrust. By middle Sakmarian (middle middle Wolfcampian) time (within Fusulinid Zone 4), emplacement of the Last Chance allochthon was complete, and subsidence caused by thrust loading had resulted in development of a new turbidite basin (Darwin Basin) along the former western part of the Bird Spring Shelf. At the same time, farther east into the craton, paralic facies began prograding westward, so that the youngest fusulinid-bearing limestones on the shelf in this area become progressively younger to the west. Eventually, in Artinskian to Kungurian (late Wolfcampian to Leonardian) time (Fusulinid Zones 5 and 6), deposition of fusulinid-bearing limestone on the shelf was restricted to a marginal belt between the prograding paralic facies to the east and the Darwin Basin to the west. Development of the Keeler Basin in Pennsylvanian to earliest Permian time was approximately coeval with collision between South America-Africa (Gondwana) and North America (Laurentia) on the Ouachita-Marathon orogenic belt. This basin developed inboard of a northwest-trending, sinistral fault zone that truncated the continental margin. Later, in the Early Permian, the Last Chance allochthon, which was part of a northeast-trending belt of deformation that extended into northeastern Nevada, was emplaced. This orogenic belt probably was driven by convergence at the continental margin to the northwest. This work adds significant detail to existing interpretations of the late Paleozoic as a time of major tectonic instability on the continental margin of southeastern California as it changed from a relatively passive margin that had characterized most of the Paleozoic to an active convergent margin that would characterize the Mesozoic. ?? 2007 The Geological Society of America. All rights reserved.

Map Showing Geology and Hydrostratigraphy of the Edwards Aquifer Catchment Area, Northern Bexar County, South-Central Texas

USGS Publications Warehouse

Clark, Amy R.; Blome, Charles D.; Faith, Jason R.

2009-01-01

Rock units forming the Edwards and Trinity aquifers in northern Bexar County, Texas, are exposed within all or parts of seven 7.5-minute quadrangles: Bulverde, Camp Bullis, Castle Hills, Helotes, Jack Mountain, San Geronimo, and Van Raub. The Edwards aquifer is the most prolific ground-water source in Bexar County, whereas the Trinity aquifer supplies water for residential, commercial, and industrial uses for areas north of the San Antonio. The geologic map of northern Bexar County shows the distribution of informal hydrostratigraphic members of the Edwards Group and the underlying upper member of the Glen Rose Limestone. Exposures of the Glen Rose Limestone, which forms the Trinity aquifer alone, cover approximately 467 km2 in the county. This study also describes and names five informal hydrostratigraphic members that constitute the upper member of the Glen Rose Limestone; these include, in descending order, the Caverness, Camp Bullis, Upper evaporite, Fossiliferous, and Lower evaporite members. This study improves our understanding of the hydrogeologic connection between the two aquifers as it describes the geology that controls the infiltration of surface water and subsurface flow of ground water from the catchment area (outcropping Trinity aquifer rocks) to the Edwards water-bearing exposures.

Coccolithophore ecology at the HOT station ALOHA, Hawaii

NASA Astrophysics Data System (ADS)

Cortés, Mara Y.; Bollmann, Jörg; Thierstein, Hans R.

Cell densities of total coccolithophores and dominant taxa were determined in 183 samples from the upper 200 m of the water column at about monthly intervals between January 1994 and August 1996 at the HOT station ALOHA, Hawaii. High cell densities were observed twice a year, in March (up to 41×10 3 cells l -1) and in September/October (up to 52×10 3 cells l -1). In the intervening months, cell densities were extremely low (0-20×10 3 cells l -1), reflecting a strong seasonality. The main production of coccolithophores took place in the middle photic zone between 50 and 100 m water depth. In total 125 coccolithophore species were identified but only five constituted on average more than 30% of the community: Emiliania huxleyi, Umbellosphaera irregularis, U. tenuis, Florisphaera profunda and Gephyrocapsa ericsonii. The generally low, but seasonally dynamic coccolithophore cell density variability is compared with in situ measurements of environmental parameters. Correlation analyses between cell density variability of the dominant taxa and potentially controlling environmental parameters show significant correlation coefficients when the data set was separated into upper and lower photic zone. Cell densities of all dominant taxa are most highly correlated with temperature variability. U. irregularis is positively correlated in the upper photic zone, whereas E. huxleyi and G. ericsonii are negatively correlated. In the lower photic zone, F. profunda cell densities are positively correlated with light, which corresponds to the maximum bottom-up control (i.e. by physical forcing) of any species encountered. The surprisingly low correlations of cell densities with nitrate and phosphate may be caused by insufficient sampling resolution, nutrient levels close to detection limits, or both.

Summary of hydrogeologic and ground-water-quality data and hydrogeologic framework at selected well sites, Adams County, Pennsylvania

USGS Publications Warehouse

Low, Dennis J.; Dugas, Diana L.

1999-01-01

Rapid population growth in Adams County has increased the demand for ground water and led Adams County planning officials to undertake an effort to evaluate the capabilities of existing community water systems to meet future, projected growth and to begin wellhead-protection programs for public-supply wells. As part of this effort, this report summarizes ground-water data on a countywide scale and provides hydrogeologic information needed to delineate wellheadprotection areas in three hydrogeologic units (Gettysburg Lowland, Blue Ridge, and Piedmont Lowland).Reported yields, specific capacities, well depths, and reported overburden thickness can vary by hydrogeologic unit, geologic formation, water use (domestic and nondomestic), and topographic setting. The reported yields of domestic wells drilled in the Gettysburg Lowland (median reported yield of 10 gallons per minute) are significantly greater than the reported yields from the Blue Ridge, Piedmont Lowland, and Piedmont Upland (median reported yields of 7.0, 8.0, and 7.0 gallons per minute, respectively). Reported yields of domestic wells completed in the diabase and the New Oxford Formation of the Gettysburg Lowland, and in the metarhyolite and metabasalt of the Blue Ridge, are significantly lower than reported yields of wells completed in the Gettysburg Formation. For nondomestic wells, reported yields from the Conestoga Formation of the Piedmont Lowland are significantly greater than in the diabase. Reported yields of nondomestic wells drilled in the Gettysburg, New Oxford, and Conestoga Formations, and the metarhyolite are significantly greater than those for domestic wells drilled in the respective geologic formations. Specific capacities of nondomestic wells in the Conestoga and Gettysburg Formations are significantly greater than their domestic counterparts. Specific capacities of nondomestic wells in the Conestoga Formation are significantly greater than the specific capacities of nondomestic wells in the metarhyolite, diabase, and Gettysburg and New Oxford Formations.Well depths do not vary considerably by hydrogeologic unit; instead, the greatest variability is by water use. Nondomestic wells drilled in the metarhyolite, Kinzers, Conestoga, Gettysburg, and New Oxford Formations are completed at significantly greater depths than their domestic counterparts. The reported thickness of overburden varies significantly by geologic formation and water use, but not by topographic setting. The median overburden thickness of the Blue Ridge (35 feet) is greater than in any other hydrologic unit.Except where adversely affected by human activities, ground water in Adams County is suitable for most purposes. Calcium and magnesium are the dominant cations, and bicarbonate is the dominant anion. In general, the pH and hardness of ground water is lower in areas that are underlain by crystalline rocks (Blue Ridge and Piedmont Upland) than in areas underlain by sedimentary rocks, especially where limestone or dolomite is dominant (Piedmont Lowland). Dissolved nitrate (as N) and dissolved nitrite (as N) concentrations in the water from 9 of 69 wells and 3 of 80 wells sampled exceeded the U.S. Environmental Protection Agency (USEPA) maximum contaminant levels (MCL) of 10 and 1.0 mg/L (milligrams per liter), respectively. Sulfate concentrations greater than the proposed USEPA MCL of 500 mg/L were reported from the water in 3 of 110 wells sampled. Iron concentrations in the water from 13 of 67 wells sampled and manganese in the water from 9 of 64 wells sampled exceeded the USEPA secondary maximum contaminant level (SMCL) of 300 and 50 mg/L (micrograms per liter), respectively. Aluminum concentrations in the water from 16 of 22 wells sampled exceeded the lower USEPA SMCL threshold of 50 µg/L. Pesticides were detected in the water from seven wells but at concentrations that did not exceed USEPA MCL's. Most volatile organic compounds detected in the ground water were confined to USEPA Superfund sites or the immediate area around the sites.The hydrogeologic framework in the vicinity of four public-supply well fields (Gettysburg, Abbottstown, Fairfield, and Littlestown) consists of two zones—an upper zone and a lower zone. In general, the upper zone is thin (5 to 60 feet or more) and dominated by saturated regolith and deeply weathered bedrock. The upper zone is bounded at the top by the water table and below by bedrock in which secondary porosity and permeability are considerably lower. Ground water is generally unconfined, and recharge rates are rapid. Ground-water flow is influenced more strongly by the topography of the ground surface and bedrock surface than by geologic structure. The lower zone is relatively thick (400 to 1,000 feet) and consists of slightly weathered to highly competent bedrock. Ground-water flow paths in the lower zone are generally greater and recharge rates are longer than in the upper zone; confined conditions are common, especially at depth.

Water Quality Conditions in Upper Klamath and Agency Lakes, Oregon, 2005

USGS Publications Warehouse

Hoilman, Gene R.; Lindenberg, Mary K.; Wood, Tamara M.

2008-01-01

During June-October 2005, water quality data were collected from Upper Klamath and Agency Lakes in Oregon, and meteorological data were collected around and within Upper Klamath Lake. Data recorded at two continuous water quality monitors in Agency Lake showed similar temperature patterns throughout the field season, but data recorded at the northern site showed more day-to-day variability for dissolved oxygen concentration and saturation after late June and more day-to-day variability for pH and specific conductance values after mid-July. Data recorded from the northern and southern parts of Agency Lake showed more comparable day-to-day variability in dissolved oxygen concentrations and pH from September through the end of the monitoring period. For Upper Klamath Lake, seasonal (late July through early August) lows of dissolved oxygen concentrations and saturation were coincident with a seasonal low of pH values and seasonal highs of ammonia and orthophosphate concentrations, specific conductance values, and water temperatures. Patterns in these parameters, excluding water temperature, were associated with bloom dynamics of the cyanobacterium (blue-green alga) Aphanizomenon flos-aquae in Upper Klamath Lake. In Upper Klamath Lake, water temperature in excess of 28 degrees Celsius (a high stress threshold for Upper Klamath Lake suckers) was recorded only once at one site during the field season. Large areas of Upper Klamath Lake had periods of dissolved oxygen concentration of less than 4 milligrams per liter and pH value greater than 9.7, but these conditions were not persistent throughout days at most sites. Dissolved oxygen concentrations in Upper Klamath Lake on time scales of days and months appeared to be influenced, in part, by bathymetry and prevailing current flow patterns. Diel patterns of water column stratification were evident, even at the deepest sites. This diel pattern of stratification was attributable to diel wind speed patterns and the shallow nature of most of Upper Klamath Lake. Timing of the daily extreme values of dissolved oxygen concentration, pH, and water temperature was less distinct with increased water column depth. Chlorophyll a concentrations varied spatially and temporally throughout Upper Klamath Lake. Location greatly affected algal concentrations, in turn affecting nutrient and dissolved oxygen concentrations - some of the highest chlorophyll a concentrations were associated with the lowest dissolved oxygen concentrations and the highest un-ionized ammonia concentrations. The occurrence of the low dissolved oxygen and high un-ionized ammonia concentrations coincided with a decline in algae resulting from cell death, as measured by concentrations of chlorophyll a. Dissolved oxygen production rates in experiments were as high as 1.47 milligrams of oxygen per liter per hour, and consumption rates were as much as -0.73 milligrams of oxygen per liter per hour. Dissolved oxygen consumption rates measured in this study were comparable to those measured in a 2002 Upper Klamath Lake study, and a higher rate of dissolved oxygen consumption was recorded in dark bottles positioned higher in the water column. Data, though inconclusive, indicated that a decreasing trend of dissolved oxygen productivity through July could have contributed to the decreasing dissolved oxygen concentrations and percent saturation recorded in Upper Klamath Lake during this time. Phytoplankton self-shading was evident from a general inverse relation between depth of photic zone and chlorophyll a concentrations. This shading caused net dissolved oxygen consumption during daylight hours in lower parts of the water column that would otherwise have been in the photic zone. Meteorological data collected in and around Upper Klamath Lake showed that winds were likely to come from a broad range of westerly directions in the northern one-third of the lake, but tended to come from a narrow range of northwesterly directions

Hydrogen-bearing iron peroxide and the origin of ultralow-velocity zones

NASA Astrophysics Data System (ADS)

Liu, Jin; Hu, Qingyang; Young Kim, Duck; Wu, Zhongqing; Wang, Wenzhong; Xiao, Yuming; Chow, Paul; Meng, Yue; Prakapenka, Vitali B.; Mao, Ho-Kwang; Mao, Wendy L.

2017-11-01

Ultralow-velocity zones (ULVZs) at Earth’s core-mantle boundary region have important implications for the chemical composition and thermal structure of our planet, but their origin has long been debated. Hydrogen-bearing iron peroxide (FeO2Hx) in the pyrite-type crystal structure was recently found to be stable under the conditions of the lowermost mantle. Using high-pressure experiments and theoretical calculations, we find that iron peroxide with a varying amount of hydrogen has a high density and high Poisson ratio as well as extremely low sound velocities consistent with ULVZs. Here we also report a reaction between iron and water at 86 gigapascals and 2,200 kelvin that produces FeO2Hx. This would provide a mechanism for generating the observed volume occupied by ULVZs through the reaction of about one-tenth the mass of Earth’s ocean water in subducted hydrous minerals with the effectively unlimited reservoir of iron in Earth’s core. Unlike other candidates for the composition of ULVZs, FeO2Hx synthesized from the superoxidation of iron by water would not require an extra transportation mechanism to migrate to the core-mantle boundary. These dense FeO2Hx-rich domains would be expected to form directly in the core-mantle boundary region and their properties would provide an explanation for the many enigmatic seismic features that are observed in ULVZs.

Numerical analysis for sea wave loading on the pile foundation of detached structures by using CADMAS-SURF

NASA Astrophysics Data System (ADS)

Matsuda, Tatsuya; Miura, Kinya; Sawada, Yayoi

2017-10-01

This study investigated the characteristics of wave forces loading on the detached structure that consisted of an upper structure and a pile foundation. In this study, structure stability was also considered on the results obtained from previous studies on the instability of seabed induced by wave force. When a wave force acted on the structure, an external force acted on the pile foundation as if pulling out the foundation on the outer harbor side and pushing it in on the inner harbor. The effective stress in seabed was increase so the pile foundation was considered to maintain sufficient bearing capacity. Subsequently, when the bearing capacity of the ground was decreased because the water pressure in the ground surface layer decreased, the pile foundation will be aggravated settled down. The external force acting on the pile foundation was not same on outer harbor and inner harbor with the form of the upper structure. As a result, we found that the strain will be generated on the structure.

Ground-water resources in the Hood Basin, Oregon

USGS Publications Warehouse

Grady, Stephen J.

1983-01-01

The Hood Basin, an area of 1,035 square miles in north-central Oregon, includes the drainage basins of all tributaries of the Columbia River between Eagle Creek and Fifteenmile Creek. The physical characteristics and climate of the basin are diverse. The Wasco subarea, in the eastern half of the basin, has moderate relief, mostly intermittent streams, and semiarid climate. The Hood subarea, in the western half, has rugged topography, numerous perennial streams, and a humid climate.Water-bearing geologic units that underlie the basin include volcanic, volcaniclastic, and sedimentary rocks of Miocene to Holocene age, and unconsolidated surficial deposits of Pleistocene and Holocene age. The most important water-bearing unit, the Columbia River Basalt Group, underlies almost the entire basin. Total thickness probably exceeds 2,000 feet, but by 1980 only the upper 1,000 feet or less had been developed by wells. Wells in this unit generally yield from 15 to 1,000 gallons per minute and a few yield as much as 3,300 gallons per minute.The most productive aquifer in the Columbia River Basalt Group is The Dalles Ground Water Reservoir, a permeable zone of fractured basalt about 25 to 30 square miles in extent that underlies the city of The Dalles. During the late 1950's and mid-1960's, withdrawals of 15,000 acre-feet per year or more caused water levels in the aquifer to decline sharply. Pumpage had diminished to about 5,000 acre-feet per year in 1979 and water levels have stabilized, indicating that ground water recharge and discharge, including the pumping, are in balance.The other principal geologic units in the basin have more limited areal distribution and less saturated thickness than the Columbia River Basalt Group. Generally, these units are capable of yielding from a few to a hundred gallons per minute to wells.Most of the ground water in the basin is chemically suitable for domestic, irrigation, or other uses. Some ground water has objectionable concentrations of iron (0.3 to 6.4 milligrams per liter) and manganese (0.05 to 1.2 milligrams per liter) or is moderately hard to very hard (60 to 260 milligrams per liter as CaCO3).The principal use of ground water in the Hood Basin is for irrigation of crops, with an estimated withdrawal of 7,700 acre-feet in 1979. Additional ground-water withdrawals in 1979 were estimated as: Industrial, 2,600 acre-feet; public supply, 2,100 acre-feet; and domestic and stock supply, 200 acre-feet.

Ground-water hydrology of the Cocoa well-field area, Orange County, Florida

USGS Publications Warehouse

Tibbals, C.H.; Frazee, J.M.

1976-01-01

The city of Cocoa, Brevard County, Florida, supplies water for much of central Brevard County including Cape Kennedy and Patrick Air Force Base. The water supply is obtained from a well field in east Orange County. Many of the easternmost wells in that well field yield salty water (chloride concentration greater than 250 milligrams per liter). The interface between the fresh and salty water in the west part of the well field occurs at a depth of about 1,400 feet. An upward hydraulic gradient exists between the the lower (salty) zones and the upper, or pumped zones of the Floridan aquifer in the west part of the well field. Secondary artesian aquifers in the well-field area are relatively high-yielding but are of limited areal extent. However, they are suitable as a source of water for supplemental supply or for artificially recharging the Floridan aquifer. Fresh water was transferred by siphon from a secondary artesian aquifer to the Floridan aquifer at 90 gallons per minute. Artificial recharge and recovery experiments show that it is feasible to retrieve fresh water stored in salty zones of the Floridan aquifer. (Woodard-USGS)

Fe and S redox states during serpentinite dehydration in subduction settings

NASA Astrophysics Data System (ADS)

Merkulova, Margarita; Munoz, Manuel; Vidal, Olivier; Brunet, Fabrice

2016-04-01

Serpentinite rocks formed by hydrothermal alteration of oceanic peridotites compose ~70% of the oceanic crust (Hacker et al., 2003), which later sinks into subduction zone and experiences metamorphic reactions. Serpentinites carry ~12 wt.% H2O and thereby introduces large amount of water in the upper mantle during dehydration in subduction (Ulmer and Trommsdorff, 1995). In addition, serpentinites are known to contain such minerals as magnetite Fe3O4 and pyrite FeS2 in the amounts of ~5 wt.% (Debret et al., 2014) and 1.5 wt.% (Alt et al., 2013), respectively. During metamorphic reactions speciations of Fe and S are tended to change and affect oxygen fugacity. In turn, oxygen fugacity influences the mobility of fluid mobile elements and metals (Pokrovski and Dubrovinsky 2011). We characterized Fe and S speciation and amount of released water during serpentinite dehydration at different temperature and pressure intervals along a subduction zone. We performed three sets of experiments using piston-cylinder apparatus. Three different starting materials composed of powdered mineral mixtures were used: Fe(III)-antigorite (atg), atg + magnetite, atg + pyrite. Experimental runs were performed at 2 GPa, between 400 and 900°C. Experimental products were first characterized by X-ray diffraction and electron microprobe. Speciation of Fe and S were characterized by X-ray absorption spectroscopy (XANES) at iron and sulfur K-edges. In addition, thermodynamic modeling was applied in this work with constrained thermodynamical data for Fe-bearing antigorite. The results demonstrate the continuous dehydration of serpentinites with the main water releasing domain between 670 and 700°C, which is happening due to breakdown of antigorite. Fe K-edge XANES measurements show that the amount of ferric iron dramatically decreases between 550-650°C, leading to a release of free oxygen in the system. As a result, we show that the first fluids released from the slab dehydration most likely present highly oxidizing properties. At higher P-T conditions, higher amounts of water are released with minor oxygen release. In addition, sulfur is shown to be progressively reduced at temperature 450-500°C due to pyrite to pyrrhotite transition. The reaction of pyrite reduction was observed to happen with sequestration of Fe from silicates and a release of oxygen. Effectively, the presence of sulphides in serpentinites contribute additional oxygen to the fluid, whereas the release of S may be negligible. The detailed study of the evolution of redox conditions during serpentinite dehydration in subduction zones will help constraining, 1) the behavior and mobility, from slab to the upper mantle, of elements of economical interest, as well as 2) the global geochemical cycling of elements. References: 1. Hacker et al. (2003) J. Geophys. Res. 108, article number 2029. 2. Ulmer & Trommsdorff (1995) Science 268, 858-861. 3. Debret et al. (2014) EPSL 400, 206-218. 4. Alt et al. (2013) Lithos 178, 40-54. 5. Pokrovski & Dubrovinsky (2011) Science 331, 1052-1056.

Potentiometric Surface of the Upper Floridan Aquifer, West-central Florida, May 2010

USGS Publications Warehouse

Ortiz, A.G.

2010-01-01

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2010. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 55.21 inches for west-central Florida (from June 2009 through May 2010) was 2.55 inches above the historical cumulative average of 52.66 inches (Southwest Florida Water Management District, 2010). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 17-21, 2010. Supplemental water-level data were collected by other agencies and companies. Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

Gas centrifuge purge method

DOEpatents

Theurich, Gordon R.

1976-01-01

1. In a method of separating isotopes in a high speed gas centrifuge wherein a vertically oriented cylindrical rotor bowl is adapted to rotate about its axis within an evacuated chamber, and wherein an annular molecular pump having an intake end and a discharge end encircles the uppermost portion of said rotor bowl, said molecular pump being attached along its periphery in a leak-tight manner to said evacuated chamber, and wherein end cap closure means are affixed to the upper end of said rotor bowl, and a process gas withdrawal and insertion system enters said bowl through said end cap closure means, said evacuated chamber, molecular pump and end cap defining an upper zone at the discharge end of said molecular pump, said evacuated chamber, molecular pump and rotor bowl defining a lower annular zone at the intake end of said molecular pump, a method for removing gases from said upper and lower zones during centrifuge operation with a minimum loss of process gas from said rotor bowl, comprising, in combination: continuously measuring the pressure in said upper zone, pumping gas from said lower zone from the time the pressure in said upper zone equals a first preselected value until the pressure in said upper zone is equal to a second preselected value, said first preselected value being greater than said second preselected value, and continuously pumping gas from said upper zone from the time the pressure in said upper zone equals a third preselected value until the pressure in said upper zone is equal to a fourth preselected value, said third preselected value being greater than said first, second and fourth preselected values.

An integrated study of earth resources in the state of California using remote sensing techniques

NASA Technical Reports Server (NTRS)

Colwell, R. N. (Principal Investigator)

1977-01-01

The author has identified the following significant results. The effects on estimates of monthly volume runoff were determined separately for each of the following parameters: precipitation, evapotranspiration, lower zone and upper zone tension water capacity, imperviousness of the watershed, and percent of the watershed occupied by riparian vegetation, streams, and lakes. The most sensitive and critical parameters were found to be precipitation during the entire year and springtime evapotranspiration.

Soil water stable isotopes reveal evaporation dynamics at the soil-plant-atmosphere interface of the critical zone

NASA Astrophysics Data System (ADS)

Sprenger, Matthias; Tetzlaff, Doerthe; Soulsby, Chris

2017-07-01

Understanding the influence of vegetation on water storage and flux in the upper soil is crucial in assessing the consequences of climate and land use change. We sampled the upper 20 cm of podzolic soils at 5 cm intervals in four sites differing in their vegetation (Scots Pine (Pinus sylvestris) and heather (Calluna sp. and Erica Sp)) and aspect. The sites were located within the Bruntland Burn long-term experimental catchment in the Scottish Highlands, a low energy, wet environment. Sampling took place on 11 occasions between September 2015 and September 2016 to capture seasonal variability in isotope dynamics. The pore waters of soil samples were analyzed for their isotopic composition (δ2H and δ18O) with the direct-equilibration method. Our results show that the soil waters in the top soil are, despite the low potential evaporation rates in such northern latitudes, kinetically fractionated compared to the precipitation input throughout the year. This fractionation signal decreases within the upper 15 cm resulting in the top 5 cm being isotopically differentiated to the soil at 15-20 cm soil depth. There are significant differences in the fractionation signal between soils beneath heather and soils beneath Scots pine, with the latter being more pronounced. But again, this difference diminishes within the upper 15 cm of soil. The enrichment in heavy isotopes in the topsoil follows a seasonal hysteresis pattern, indicating a lag time between the fractionation signal in the soil and the increase/decrease of soil evaporation in spring/autumn. Based on the kinetic enrichment of the soil water isotopes, we estimated the soil evaporation losses to be about 5 and 10 % of the infiltrating water for soils beneath heather and Scots pine, respectively. The high sampling frequency in time (monthly) and depth (5 cm intervals) revealed high temporal and spatial variability of the isotopic composition of soil waters, which can be critical, when using stable isotopes as tracers to assess plant water uptake patterns within the critical zone or applying them to calibrate tracer-aided hydrological models either at the plot to the catchment scale.

Geologic framework and hydrogeologic characteristics of the Glen Rose limestone, Camp Stanley Storage Activity, Bexar County, Texas

USGS Publications Warehouse

Clark, Allan K.

2004-01-01

The Trinity aquifer is a regional water source in the Hill Country of south-central Texas that supplies water for agriculture, commercial, domestic, and stock purposes. Rocks of the Glen Rose Limestone, which compose the upper zone and upper part of the middle zone of the Trinity aquifer, crop out at the Camp Stanley Storage Activity (CSSA), a U.S. Army weapons and munitions supply, maintenance, and storage facility in northern Bexar County (San Antonio area) (fig. 1). On its northeastern, eastern, and southern boundaries, the CSSA abuts the Camp Bullis Training Site, a U.S. Army field training site for military and Federal government agencies. During 2003, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army, studied the outcropping Glen Rose Limestone at the CSSA and immediately adjacent area (Camp Stanley study area, fig. 1) to identify and map the hydrogeologic subdivisions and faults of the Glen Rose Limestone at the facility. The results of the study are intended to help resource managers improve their understanding of the distribution of porosity and permeability of the outcropping rocks, and thus the conditions for recharge and the potential for contaminants to enter the Glen Rose Limestone. This study followed a similar study done by the USGS at Camp Bullis (Clark, 2003). The purpose of this report is to present the geologic framework and hydrogeologic characteristics of the Glen Rose Limestone in the study area. The hydrogeologic nomenclature follows that introduced by Clark (2003) for the outcropping Glen Rose Limestone at Camp Bullis in which the upper member of the Glen Rose Limestone (hereinafter, upper Glen Rose Limestone), which is coincident with the upper zone of the Trinity aquifer, is divided into five intervals on the basis of observed lithologic and hydrogeologic properties. An outcrop map, two generalized sections, related illustrations, and a table summarize the description of the framework and distribution of characteristics.

Interacting vegetative and thermal contributions to water movement in desert soil

USGS Publications Warehouse

Garcia, C.A.; Andraski, Brian J.; Stonestrom, David A.; Cooper, C.A.; Šimůnek, J.; Wheatcraft, S.W.

2011-01-01

Thermally driven water-vapor flow can be an important component of total water movement in bare soil and in deep unsaturated zones, but this process is often neglected when considering the effects of soil–plant–atmosphere interactions on shallow water movement. The objectives of this study were to evaluate the coupled and separate effects of vegetative and thermal-gradient contributions to soil water movement in desert environments. The evaluation was done by comparing a series of simulations with and without vegetation and thermal forcing during a 4.7-yr period (May 2001–December 2005). For vegetated soil, evapotranspiration alone reduced root-zone (upper 1 m) moisture to a minimum value (25 mm) each year under both isothermal and nonisothermal conditions. Variations in the leaf area index altered the minimum storage values by up to 10 mm. For unvegetated isothermal and nonisothermal simulations, root-zone water storage nearly doubled during the simulation period and created a persistent driving force for downward liquid fluxes below the root zone (total net flux ~1 mm). Total soil water movement during the study period was dominated by thermally driven vapor fluxes. Thermally driven vapor flow and condensation supplemented moisture supplies to plant roots during the driest times of each year. The results show how nonisothermal flow is coupled with plant water uptake, potentially influencing ecohydrologic relations in desert environments.

Integration of seismic interpretation and petrophysical studies on Hawaz Formation in J-field NC-186 concession, Northwest Murzuq basin, Libya

NASA Astrophysics Data System (ADS)

Mohamed, A. K.; Selim, E. I.; Kashlaf, A.

2016-12-01

This study has been carried out by the integration of seismic interpretations and the well-logging analysis of ten wells distributed in J-field of concession NC-186, Murzuq basin, Libya. Twenty (3D) seismic lines and ten wells have been analyzed. The results of this study indicated that, the main reservoir in this concession is Hawaz Formation. Hawaz has been split into 8 units with a subdivision of Hawaz H4 into three subunits with the objective of better characterization of the three general fine upward intervals. The lower interval of H4 zone presents the better reservoir properties. The depth of reflector H4 ranges from 4100 ft in the northwestern part of the study area and increases to 4600 ft in the southeastern part of the study area. In this study, the outline of the Hawaz paleohighs which is NC-186 Field ;J; is generally trending in the NW-SE direction. The well logging analysis particularly quick look interpretation indicates that Hawaz Formation in the studied wells is mainly oil-bearing with some water-bearing sand levels at the horizons from H4 to and H6 which are potentially the main reservoirs. The water bearing zones are beyond these horizons starting from the sub-horizon H6c and the oil water contact is probably at depth 4495 ft. The crossplot of porosity-saturation for H5 and H6b indicates firmly that these horizons are indeed at irreducible state and will produce mainly oil as indicated in J4-NC186 well, while the crossplot of H8 shows wide scattering of points which is the main characteristic for water producing horizon. The depth of Hawaz Formation H4 is more than 4160 ft in J4, J12 and J16 wells in the northwestern parts of this field and increases to 4400 in the central part of the concession at well J1.

Hydrogeology of the Mogollon Highlands, central Arizona

USGS Publications Warehouse

Parker, John T.C.; Steinkampf, William C.; Flynn, Marilyn E.

2005-01-01

The Mogollon Highlands, 4,855 square miles of rugged, mountainous terrain at the southern edge of the Colorado Plateau in central Arizona, is characterized by a bedrock-dominated hydrologic system that results in an incompletely integrated regional ground-water system, flashy streamflow, and various local water-bearing zones that are sensitive to drought. Increased demand on the water resources of the area as a result of recreational activities and population growth have made necessary an increased understanding of the hydrogeology of the region. The U.S. Geological Survey conducted a study of the geology and hydrology of the region in cooperation with the Arizona Department of Water Resources under the auspices of the Arizona Rural Watershed Initiative, a program launched in 1998 to assist rural areas in dealing with water-resources issues. The study involved the analysis of geologic maps, surface-water and ground-water flow, and water and rock chemical data and spatial relationships to characterize the hydrogeologic framework. The study area includes the southwestern corner of the Colorado Plateau and the Mogollon Rim, which is the eroded edge of the plateau. A 3,000- to 4,000-foot sequence of early to late Paleozoic sedimentary rocks forms the generally south-facing scarp of the Mogollon Rim. The area adjacent to the edge of the Mogollon Rim is an erosional landscape of rolling, step-like terrain exposing Proterozoic metamorphic and granitic rocks. Farther south, the Sierra Ancha and Mazatzal Mountain ranges, which are composed of various Proterozoic rocks, flank an alluvial basin filled with late Cenozoic sediments and volcanic flows. Eight streams with perennial to intermittent to ephemeral flow drain upland regions of the Mogollon Rim and flow into the Salt River on the southern boundary or the Verde River on the western boundary. Ground-water flow paths generally are controlled by large-scale fracture systems or by karst features in carbonate rocks. Stream channels are also largely controlled by structural features, such as regional joint or fault systems. Precipitation, which shows considerable variability in amount and intensity, recharges the ground-water system along the crest of the Mogollon Rim and to a lesser extent along the crests and flanks of the rim and the Mazatzal Mountains and Sierra Ancha. Flashy runoff in the mainly bedrock stream channels is typical. Springs are distributed throughout the region, typically discharging at or above the contact of variably permeable formations along the face of the Mogollon Rim with a scattering of low-discharge springs in the Proterozoic rocks below the rim. The surface of the Colorado Plateau is the primary recharge area for the C aquifer in which ground-water flows north toward the Little Colorado River and south toward the Mogollon Highlands. Within the study area, flow from the C aquifer primarily discharges from large, stable springs in the upper East Verde River, Tonto Creek, and Canyon Creek Basins along the top of the Mogollon Rim and to the west as base flow in West Clear Creek. On the basis of chemical evidence and the distribution and flow characteristics of springs and perennial streams, the C aquifer is also the source of water for the limestone aquifer that discharges from carbonate rocks near the base of the Mogollon Rim. Vertical flow from the C aquifer, the base of which is in the Schnebly Hill Formation, recharges the limestone aquifer that discharges mainly at Fossil Springs in the western part of the study area and as base flow in Cibecue Creek on the eastern edge of the study area. Local, generally shallow aquifers of variable productivity occur in plateau and mesa-capping basalts in the sedimentary rocks of the Schnebly Hill and Supai Formations, in fractured zones of the Proterozoic Payson granite, and in the alluvium of the lower Tonto Creek Basin. Where time series data exist, such water-bearing zones are shown to be sensitive to short-

Potentiometric surface of the upper Floridan aquifer, west-central Florida, May 2011

USGS Publications Warehouse

Ortiz, Anita G.

2011-01-01

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2011. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 45.74 inches for west-central Florida (from June 2010 through May 2011) was 6.85 inches below the historical cumulative average of 52.59 inches (Southwest Florida Water Management District, 2011). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September from 1975 through 2010. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 23-27, 2011. Supplemental water-level data were collected by other agencies and companies. Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a "snapshot" of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

Combining the Neuman and Boulton models for flow to a well in an unconfined aquifer

USGS Publications Warehouse

Moench, Allen F.

1995-01-01

A Laplace transform solution is presented for flow to a well in a homogeneous, water-table aquifer with noninstanta-neous drainage of water from the zone above the water table. The Boulton convolution integral is combined with Darcy's law and used as an upper boundary condition to replace the condition used by Neuman. Boulton's integral derives from the assumption that water drained from the unsaturated zone is released gradually in a manner that varies exponentially with time in response to a unit decline in hydraulic head, whereas the condition used by Newman assumes that the water is released instantaneously. The result is a solution that reduces to the solution obtained by Neuman as the rate of release of water from the zone above the water table increases. A dimensionless fitting parameter, γ, is introduced that incorporates vertical hydraulic conductivity, saturated thickness, specific yield, and an empirical constant α1, similar to Boulton's α. Results show that theoretical drawdown in water-table piezometers is amplified by noninstantaneous drainage from the unsaturated zone to a greater extent than drawdown in piezometers located at depth in the saturated zone. This difference provides a basis for evaluating γ by type-curve matching in addition to the other dimensionless parameters. Analysis of drawdown in selected piezometers from the published results of two aquifer tests conducted in relatively homogeneous glacial outwash deposits but with significantly different hydraulic conductivities reveals improved comparison between the theoretical type curves and the hydraulic head measured in water-table piezometers.

Internally Consistent Single-Crystal Elasticity of (Mg0.89Fe0.11)2SiO4 Wadsleyite at High Pressures and High Temperatures

NASA Astrophysics Data System (ADS)

Buchen, J.; Marquardt, H.; Kurnosov, A.; Boffa Ballaran, T.; Speziale, S.; Kawazoe, T.

2016-12-01

The transition zone in Earth's upper mantle attains a pivotal role in deep Earth dynamics. Various scenarios for the fate of subducted lithospheric slabs have been identified from seismic tomographic images while petrological observations point to potential reservoirs of volatile elements in the transition zone. Among the mineral phases expected to assemble a mantle rock at depths between 410 km and 520 km, wadsleyite stands out with a remarkable hydrogen storage capacity of several weight percent H2O, a volume fraction of about 60 % for a pyrolitic mantle composition, and the potential to cause seismic anisotropy. Interpretations of seismological observations in terms of the thermal and mineralogical state of the upper transition zone rely on the elastic properties of wadsleyite at the prevailing conditions of pressure and temperature including its elastic anisotropy. We have determined internally consistent single-crystal elastic constants for wadsleyite with a relevant composition ((Mg0.89Fe0.11)1.98H0.04SiO4, 0.25(3) wt-% H2O) up to a pressure of 16 GPa at room temperature and conducted first measurements at combined high pressures and high temperatures. Single-crystal segments were cut from oriented thin sections with a focused ion beam and complementary orientations loaded together into the same pressure chamber of resistively heated diamond anvil cells. Using this two-sample approach and a combination of Brillouin spectroscopy and single-crystal X-ray diffraction, all nine independent elastic constants can be obtained under consistent conditions of pressure and temperature. Comparison of our room temperature results with those reported for wadsleyites with different iron contents suggests a very small effect of Fe-Mg substitution on the bulk modulus while the shear modulus decreases with increasing iron content. This differential effect of iron on the elastic moduli bears the potential to be seismically distinguishable from the signatures of temperature or other chemical substituents like volatile elements. The two-sample approach is currently being extended to four crystal segments to directly quantify the effect of hydrogen incorporation on the elastic behavior of iron-bearing wadsleyite.

Polyphase enrichment and redistribution processes in silver-rich mineral associations of the hydrothermal fluorite-barite-(Ag-Cu) Clara deposit, SW Germany

NASA Astrophysics Data System (ADS)

Keim, Maximilian F.; Walter, Benjamin F.; Neumann, Udo; Kreissl, Stefan; Bayerl, Richard; Markl, Gregor

2018-03-01

The silver-copper sulfide mineralization associated with the fluorite-barite vein system at the Clara deposit in SW Germany shows large scale vertical zoning. Low to moderate silver contents prevail in the upper 350 m, whereas high silver contents occur in the subsequent 450 m of the currently known vein system. This change in Ag tenor is related to conspicuous mineralogical changes with depth. A detailed petrographic and fluid inclusion study identifies evidence for five subsequent hydrothermal and one alteration stage—all contributing to mineralogical diversity. The vertical Ag zoning, however, is attributed only to the first of these stages. During this first stage, increasing oxidation of ascending hydrothermal fluids (90-160 °C, 24.2-26.7 wt% NaCl+CaCl2) led to the formation of high-Ag tetrahedrite-tennantite in the lower parts and basically Ag-free enargite in the upper parts of the vein system. The subsequent hydrothermal stage led to significant mineralogical changes, but inherited the pre-existing Ag zonation. In this second hydrothermal stage, which was related to fluids similar in composition to those of the first stage (70-125 °C, 23.1-26.5 wt% NaCl+CaCl2), dissolution of high Ag-tetrahedrite-tennantite resulted in the formation of complex Ag-sulfosalts together with moderately Ag-bearing tetrahedrite-tennantite and chalcopyrite. The first two stages were formed by fluid mixing of a sedimentary and a hot basement fluid. The influx of fluids with high Ag, Bi and Pb activity during stage 3 and 5 resulted in the local replacement of earlier Ag-sulfosalts by galena and Ag-(Bi)-sulfosalts. The fourth stage is marked by partial dissolution of sulfides and sulfosalts by a late, hot, undiluted basement fluid (250 °C, 18.7-20.9 wt% NaCl+CaCl2) precipitating fluorite, barite and quartz. Finally, supergene alteration lead to the dissolution of silver-bearing phases and the precipitation of acanthite and native silver. The study illustrates, how metal tenor and mineralogy are decoupled in vertically extensive, polyphase hydrothermal vein systems. This may be pertinent to similarly zoned polymetallic vein systems.

Description and application of capture zone delineation for a wellfield at Hilton Head Island, South Carolina

USGS Publications Warehouse

Landmeyer, J.E.

1994-01-01

Ground-water capture zone boundaries for individual pumped wells in a confined aquffer were delineated by using groundwater models. Both analytical and numerical (semi-analytical) models that more accurately represent the $round-water-flow system were used. All models delineated 2-dimensional boundaries (capture zones) that represent the areal extent of groundwater contribution to a pumped well. The resultant capture zones were evaluated on the basis of the ability of each model to realistically rapresent the part of the ground-water-flow system that contributed water to the pumped wells. Analytical models used were based on a fixed radius approach, and induded; an arbitrary radius model, a calculated fixed radius model based on the volumetric-flow equation with a time-of-travel criterion, and a calculated fixed radius model derived from modification of the Theis model with a drawdown criterion. Numerical models used induded the 2-dimensional, finite-difference models RESSQC and MWCAP. The arbitrary radius and Theis analytical models delineated capture zone boundaries that compared least favorably with capture zones delineated using the volumetric-flow analytical model and both numerical models. The numerical models produced more hydrologically reasonable capture zones (that were oriented parallel to the regional flow direction) than the volumetric-flow equation. The RESSQC numerical model computed more hydrologically realistic capture zones than the MWCAP numerical model by accounting for changes in the shape of capture zones caused by multiple-well interference. The capture zone boundaries generated by using both analytical and numerical models indicated that the curnmtly used 100-foot radius of protection around a wellhead in South Carolina is an underestimate of the extent of ground-water capture for pumped wetis in this particular wellfield in the Upper Floridan aquifer. The arbitrary fixed radius of 100 feet was shown to underestimate the upgradient contribution of ground-water flow to a pumped well.

Constraints on the Amount of deeply subducted Water from numerical Models in comparison with natural Samples

NASA Astrophysics Data System (ADS)

Konrad-Schmolke, M.; Halama, R.

2014-12-01

The subduction of hydrated slab mantle to beyond-arc depths is the most important and yet weakly constrained factor in the quantification of the Earth's deep geologic water cycle. During subduction of hydrated oceanic lithosphere, dehydration reactions in the downgoing plate lead to a partitioning of water between upper and lower plate. Water retained in the slab is recycled into the mantle where it controls its rheology and thus plate tectonic velocities. Hence, quantification of the water partitioning in subduction zones is crucial for the understanding of mass transfer between the Earth's surface and the mantle. Combined thermomechanical and thermodynamic models yield quantitative constraints on the water cycle in subduction zones, but unless model results can be linked to natural observations, the reliability of such models remains speculative. We present combined thermomechanical, thermodynamic and geochemical models of active and paleo-subduction zones, whose results can be tested with independent geochemical features in natural rocks. In active subduction zones, evidence for the validity of our model comes from the agreement between modeled and observed across-arc trends of boron concentrations and isotopic compositions in arc volcanic rocks. In the Kamchatkan subduction zone, for example, the model successfully predicts complex geochemical patterns and the spatial distribution of arc volcanoes. In paleo-subduction zones (e.g. Western Gneiss Region and Western Alps), constraints on the water budget and dehydration behavior of the subducting slab come from trace element zoning patterns in ultra-high pressure (UHP) garnets. Distinct enrichments of Cr, Ni and REE in the UHP zones of the garnets can be reconciled by our models that predict intense rehydration and trace element re-enrichment of the eclogites at UHP conditions by fluids released from the underlying slab mantle. Models of present-day subduction zones indicate the presence of 2.5-6 wt.% of water within the uppermost 15 km of the subducted slab mantle. Depending on hydration depth, between 25 and 90% of this water is recycled into the deeper mantle. The Lower Devonian example from the Western Gneiss Region indicates that subduction of water into the Earth's deeper mantle is an active process at least since the middle Paleozoic.

Introduction to paleoenvironments of Bear Lake, Utah and Idaho, and its catchment

USGS Publications Warehouse

Rosenbaum, Joseph G.; Kaufman, Darrell S.

2009-01-01

In 1996 a group led by the late Kerry Kelts (University of Minnesota) and Robert Thompson (U.S. Geological Survey) acquired three piston cores (BL96-1, -2, and -3) from Bear Lake. The coring arose from their recognition of Bear Lake as a potential repository of long records of paleoenvironmental change. They recognized that the lake is located in an area that is sensitive to changes in regional climate patterns (Dean et al., this volume), that the lake basin is long lived (see Colman, 2006; Kaufman et al., this volume), and that, unlike many lakes in the Great Basin, Bear Lake was never dry during warm dry periods. Bear Lake lies in the northeastern Great Basin to the northeast of Great Salt Lake, just south of the Snake River drainage, and a short distance west of the Green River drainage that makes up part of the Upper Colorado River Basin (Fig. 1). Similarity among the historic Bear Lake and Great Salt Lake hydrographs and flows on the Green River indicates that the hydrology of Bear Lake reflects regional precipitation (Fig. 2). Therefore, paleorecords from Bear Lake are important to understanding past climate for a large region, including the Upper Colorado River Basin, the source of much of the water for the southwestern United States. Initially, paleoenvironmental studies of Bear Lake sediments focused on cores BL96-1, -2, and -3. Additional coring was conducted to elucidate the spatial distribution of sedimentary units and to extend the record back in time. The study was also expanded to include extensive study of the catchment, including the properties of catchment materials and the processes that could potentially affect the delivery of catchment materials to the lake. Cores BL96-1, -2, and -3 were taken with a Kullenburg piston corer along an east–west profile in roughly 50, 40, and 30 m of water, respectively (Table 1, Fig. 3). These three cores, each taken as a single 4- to 5-m-long segment, provide a nearly complete composite section from ca. 26 cal ka to the late Holocene. In 1998 a number of short gravity cores were taken from the uppermost water-rich sediments that were not sampled by the 1996 cores. During 2000, cores were taken with a percussion piston corer (manufactured by UWITEC) at three locations in and around Mud Lake and at two locations in the northern end of Bear Lake (Fig. 3). Cores acquired with the percussion corer comprise as many as three overlapping segments up to 2 m in length. In 2002, additional percussion piston cores and associated gravity cores of the uppermost sediments were acquired from five sites in the northern half of the lake. In conjunction with two of the cores collected in 2000, these cores form a north–south profile along a seismic line and span water depths from less than 10 m to ~40 m. Data from this profile provide much of the evidence for lake-level variations (Smoot and Rosenbaum, this volume). Finally, during 2000, two long cores, BL00-1D and -1E (collectively referred to here simply as BL00-1), were taken at a site near the depocenter during testing of the GLAD800 coring platform (Fig. 4; Dean et al., 2002). These cores provide a record back to ca. 220 ka.

Physical-Biological Coupling in the Western South China Sea: The Response of Phytoplankton Community to a Mesoscale Cyclonic Eddy.

PubMed

Wang, Lei; Huang, Bangqin; Chiang, Kuo-Ping; Liu, Xin; Chen, Bingzhang; Xie, Yuyuan; Xu, Yanping; Hu, Jianyu; Dai, Minhan

2016-01-01

It is widely recognized that the mesoscale eddies play an important part in the biogeochemical cycle in ocean ecosystem, especially in the oligotrophic tropical zones. So here a heterogeneous cyclonic eddy in its flourishing stage was detected using remote sensing and in situ biogeochemical observation in the western South China Sea (SCS) in early September, 2007. The high-performance liquid chromatography method was used to identify the photosynthetic pigments. And the CHEMical TAXonomy (CHEMTAX) was applied to calculate the contribution of nine phytoplankton groups to the total chlorophyll a (TChl a) biomass. The deep chlorophyll a maximum layer (DCML) was raised to form a dome structure in the eddy center while there was no distinct enhancement for TChl a biomass. The integrated TChl a concentration in the upper 100 m water column was also constant from the eddy center to the surrounding water outside the eddy. However the TChl a biomass in the surface layer (at 5 m) in the eddy center was promoted 2.6-fold compared to the biomass outside the eddy (p < 0.001). Thus, the slight enhancement of TChl a biomass of euphotic zone integration within the eddy was mainly from the phytoplankton in the upper mixed zone rather than the DCML. The phytoplankton community was primarily contributed by diatoms, prasinophytes, and Synechococcus at the DCML within the eddy, while less was contributed by haptophytes_8 and Prochlorococcus. The TChl a biomass for most of the phytoplankton groups increased at the surface layer in the eddy center under the effect of nutrient pumping. The doming isopycnal within the eddy supplied nutrients gently into the upper mixing layer, and there was remarkable enhancement in phytoplankton biomass at the surface layer with 10.5% TChl a biomass of water column in eddy center and 3.7% at reference stations. So the slight increasing in the water column integrated phytoplankton biomass might be attributed to the stimulated phytoplankton biomass at the surface layer.

Gravity anomaly and density structure of the San Andreas fault zone

NASA Astrophysics Data System (ADS)

Wang, Chi-Yuen; Rui, Feng; Zhengsheng, Yao; Xingjue, Shi

1986-01-01

A densely spaced gravity survey across the San andreas fault zone was conducted near Bear Valley, about 180 km south of San Francisco, along a cross-section where a detailed seismic reflection profile was previously made by McEvilly (1981). With Feng and McEvilly's velocity structure (1983) of the fault zone at this cross-section as a constraint, the density structure of the fault zone is obtained through inversion of the gravity data by a method used by Parker (1973) and Oldenburg (1974). Although the resulting density picture cannot be unique, it is better constrained and contains more detailed information about the structure of the fault than was previously possible. The most striking feature of the resulting density structure is a deeply seated tongue of low-density material within the fault zone, probably representing a wedge of fault gouge between the two moving plates, which projects from the surface to the base of the seismogenic zone. From reasonable assumptions concerning the density of the solid grains and the state of saturation of the fault zone the average porosity of this low-density fault gouge is estimated as about 12%. Stress-induced cracks are not expected to create so much porosity under the pressures in the deep fault zone. Large-scaled removal of fault-zone material by hydrothermal alteration, dissolution, and subsequent fluid transport may have occurred to produce this pronounced density deficiency. In addition, a broad, funnel-shaped belt of low density appears about the upper part of the fault zone, which probably represents a belt of extensively shattered wall rocks.

Analysing the mechanisms of soil water and vapour transport in the desert vadose zone of the extremely arid region of northern China

NASA Astrophysics Data System (ADS)

Du, Chaoyang; Yu, Jingjie; Wang, Ping; Zhang, Yichi

2018-03-01

The transport of water and vapour in the desert vadose zone plays a critical role in the overall water and energy balances of near-surface environments in arid regions. However, field measurements in extremely dry environments face many difficulties and challenges, so few studies have examined water and vapour transport processes in the desert vadose zone. The main objective of this study is to analyse the mechanisms of soil water and vapour transport in the desert vadose zone (depth of ∼350 cm) by using measured and modelled data in an extremely arid environment. The field experiments are implemented in an area of the Gobi desert in northwestern China to measure the soil properties, daily soil moisture and temperature, daily water-table depth and temperature, and daily meteorological records from DOYs (Days of Year) 114-212 in 2014 (growing season). The Hydrus-1D model, which simulates the coupled transport of water, vapour and heat in the vadose zone, is employed to simulate the layered soil moisture and temperature regimes and analyse the transport processes of soil water and vapour. The measured results show that the soil water and temperatures near the land surface have visible daily fluctuations across the entire soil profile. Thermal vapour movement is the most important component of the total water flux and the soil temperature gradient is the major driving factor that affects vapour transport in the desert vadose zone. The most active water and heat exchange occurs in the upper soil layer (depths of 0-25 cm). The matric potential change from the precipitation mainly re-draws the spatio-temporal distribution of the isothermal liquid water in the soil near the land surface. The matric potential has little effect on the isothermal vapour and thermal liquid water flux. These findings offer new insights into the liquid water and vapour movement processes in the extremely arid environment.

Geophysical characteristics of the hydrothermal systems of Kilauea volcano, Hawaii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kauahikaua, J.

1993-08-01

Clues to the structure of Kilauea volcano can be obtained from spatial studies of gravity, magnetic, and seismic velocity variations. The rift zones and summit are underlain by dense, magnetic, and seismic velocity variations. The rift zones and summit are underlain by dense, magnetic, high P-wave-velocity rocks at depths of about 2 km less. The gravity and seismic velocity studies indicate that the rift structures are broad, extending farther to the north than to the south of the surface features. The magnetic data allow separation into a narrow, highly-magnetized, shallow zone and broad, flanking, magnetic lows. The patterns of gravity,more » magnetic variations, and seismicity document the southward migration of the upper east rift zone. Regional, hydrologic features of Kilauea can be determined from resistivity and self-potential studies. High-level groundwater exists beneath Kilauea summit to elevations of +800 m within a triangular area bounded by the west edge of the upper southwest rift zone, the east edge of the upper east rift zone, and the Koa'e fault system. High-level groundwater is present within the east rift zone beyond the triangular summit area. Self-potential mapping shows that areas of local heat produce local fluid circulation in the unconfined aquifer (water table). Shallow seismicity and surface deformation indicate that magma is intruding and that fractures are forming beneath the rift zones and summit area. Heat flows of 370--820 mW/m[sup 2] are calculated from deep wells within the lower east rift zone. The estimated heat input rate for Kilauea of 9 gigawatts (GW) is at least 25 times higher than the conductive heat loss as estimated from the heat flow in wells extrapolated over the area of the summit caldera and rift zones. 115 refs., 13 figs., 1 tab.« less

Study on vibration characteristics of the shaft system for a dredging pump based on FEM

NASA Astrophysics Data System (ADS)

Zhai, L. M.; Qin, L.; Liu, C. Y.; Liu, X.; He, L. Y.; He, Y.; Wang, Z. W.

2012-11-01

The dynamic characteristics of the shaft system for a dredging pump were studied with the Finite Element Method (FEM) by SAMCEF ROTOR. At first, the influence of the fluid-solid coupling interaction of mud water and impeller, water sealing and pump shaft on the lateral critical speeds were analyzed. The results indicated that the mud water must be taken into consideration, while the water sealing need not to. Then the effects of radial and thrust rolling bearings on the lateral critical speeds were discussed, which shows that the radial bearing close to the impeller has greatest impact on the 1st order critical speed. At last, the upper and lower limits of the critical speeds of lateral, axial and torsional vibration were calculated. The rated speed of the dredging pump was far less than the predicted critical speed, which can ensure the safe operation of the unit. Each vibration mode is also shown in this paper. This dynamic analysis method offers some reference value on the research of vibration and stability of the shaft system in dredging pump.

High aeration rate enhances flow stratification in full-scale oxidation ditch.

PubMed

Diamantis, Vasileios; Papaspyrou, Ioannis; Melidis, Parasxos; Aivasidis, Alexander

2010-02-01

Aerated channel reactors with a uniform field of aeration may display flow stratification and short-circuit phenomena in wastewater treatment systems. In this study, we present data suggesting that flow stratification is closely related to the aeration rate and the arrangement of aerators. A full-scale oxidation ditch, with a total volume of 6,500 m(3) and a membrane-diffused aerated zone of 60 x 7 x 5 m (length-width-depth), was selected for water velocity measurements. Two profiles of the oxidation ditch were studied in detail: the first one was at the end of the aerated zone and the second one at the end of the anoxic zone. The results of this work demonstrate that the horizontal water velocity at the end of the aerated zone displayed significant stratification, with maximum velocity near the water surface (0.5-0.7 m/s) and almost zero velocity at a depth of 2.5 m. At the end of the anoxic zone, water velocity was uniform and equal to 0.27-0.31 m/s. Increasing the aeration rate from 1,800 to 4,300 m(3)/h, almost 90% of the water flow was found to discharge through the upper-half of the channel reactor profile. Different options to mitigate flow stratification of the oxidation ditch are discussed in this paper.

Dehydration-driven stress transfer triggers intermediate-depth earthquakes

PubMed Central

Ferrand, Thomas P.; Hilairet, Nadège; Incel, Sarah; Deldicque, Damien; Labrousse, Loïc; Gasc, Julien; Renner, Joerg; Wang, Yanbin; Green II, Harry W.; Schubnel, Alexandre

2017-01-01

Intermediate-depth earthquakes (30–300 km) have been extensively documented within subducting oceanic slabs, but their mechanics remains enigmatic. Here we decipher the mechanism of these earthquakes by performing deformation experiments on dehydrating serpentinized peridotites (synthetic antigorite-olivine aggregates, minerals representative of subduction zones lithologies) at upper mantle conditions. At a pressure of 1.1 gigapascals, dehydration of deforming samples containing only 5 vol% of antigorite suffices to trigger acoustic emissions, a laboratory-scale analogue of earthquakes. At 3.5 gigapascals, acoustic emissions are recorded from samples with up to 50 vol% of antigorite. Experimentally produced faults, observed post-mortem, are sealed by fluid-bearing micro-pseudotachylytes. Microstructural observations demonstrate that antigorite dehydration triggered dynamic shear failure of the olivine load-bearing network. These laboratory analogues of intermediate-depth earthquakes demonstrate that little dehydration is required to trigger embrittlement. We propose an alternative model to dehydration-embrittlement in which dehydration-driven stress transfer, rather than fluid overpressure, causes embrittlement. PMID:28504263

The frontier beneath our feet

NASA Astrophysics Data System (ADS)

Grant, Gordon E.; Dietrich, William E.

2017-04-01

Following the simple question as to where water goes when it rains leads to one of the most exciting frontiers in earth science: the critical zone—Earth's dynamic skin. The critical zone extends from the top of the vegetation canopy through the soil and down to fresh bedrock and the bottom of the groundwater. Only recently recognized as a distinct zone, it is challenging to study because it is hard to observe directly, and varies widely across biogeoclimatic regions. Yet new ideas, instruments, and observations are revealing surprising and sometimes paradoxical insights, underscoring the value of field campaigns and long-term observatories. These insights bear directly on some of the most pressing societal problems today: maintaining healthy forests, sustaining streamflow during droughts, and restoring productive terrestrial and aquatic ecosystems. The critical zone is critical because it supports all terrestrial life; it is the nexus where water and carbon is cycled, vegetation (hence food) grows, soil develops, landscapes evolve, and we live. No other frontier is so close to home.

Liquid interfacial water and brines in the upper surface of Mars

NASA Astrophysics Data System (ADS)

Moehlmann, Diedrich

2013-04-01

Liquid interfacial water and brines in the upper surface of Mars Diedrich T.F. Möhlmann DLR Institut für Planetenforschung, Rutherfordstr. 2, D - 12489 Berlin, Germany dirk.moehlmann@dlr.de Interfacial water films and numerous brines are known to remain liquid at temperatures far below 0° C. The physical processes behind are described in some detail. Deliquescence, i.e. the liquefaction of hygroscopic salts at the threshold of a specific "Deliquescence Relative Humidity", is shown to be that process, which on present Mars supports the formation of stable interfacial water and bulk liquids in form of temporary brines on and in a salty upper surface of present Mars in a diurnally temporary and repetitive process. Temperature and relative humidity are the governing conditions for deliquescence (and the counterpart "efflorescence") to evolve. The current thermo-dynamical conditions on Mars support these processes to evolve on present Mars. The deliquescence-driven presence of liquid brines in the soil of the upper surface of Mars can expected to be followed by physical and chemical processes like "surface cementation", down-slope flows, and physical and chemical weathering processes. A remarkable and possibly also biologically relevant evolution towards internally interfacial water bearing structures of dendritic capillaries is related to their freezing - thawing driven formation. The internal walls of these network-pores or -tubes can be covered by films of interfacial water, providing that way possibly habitable crack-systems in soil and rock. These evolutionary processes of networks, driven by their tip-growth, can expected to be ongoing also at present.

Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig

NASA Technical Reports Server (NTRS)

Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Mehmed, Oral; Johnson, Dexter; Montague, Gerald; Duffy, Kirsten; Jansen, Ralph

2005-01-01

The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig is an apparatus for vibration testing of turbomachine blades in a vacuum at rotational speeds from 0 to 40,000 rpm. This rig includes (1) a vertically oriented shaft on which is mounted an assembly comprising a rotor holding the blades to be tested, (2) two actively controlled heteropolar radial magnetic bearings at opposite ends of the shaft, and (3) an actively controlled magnetic thrust bearing at the upper end of the shaft. This rig is a more capable successor to a prior apparatus, denoted the Dynamic Spin Rig (DSR), that included a vertically oriented shaft with a mechanical thrust bearing at the upper end and a single actively controlled heteropolar radial magnetic bearing at the lower end.

A preliminary appraisal of the Garber-Wellington Aquifer, southern Logan and northern Oklahoma counties, Oklahoma

USGS Publications Warehouse

Carr, Jerry E.; Marcher, Melvin V.

1977-01-01

The Garber-Wellington aquifer, which dips westward at 30 to 40 feet per mile, consists of about 900 feet of interbedded sandstone, shale, and siltstone. Sandstone comprises 35 to 75 percent of the aquifer and averages about 50 percent. Water-table conditions generally exist in the upper 200 feet in the outcrop area of the aquifer; semi-artesian or artesian conditions exist below a depth of 200 feet and beneath rocks of the Hennessey Group (predominantly shale) where the aquifer is fully saturated. Water containing more than 1,000 milligrams per liter dissolved solids occurs at various depths through the area. The altitude of the base of fresh water ranges from 250 feet above sea level in the south-central part of the area to 950 feet in the northwestern part. The thickness of the fresh-water zone ranges from less than 150 feet in the northern part of the area to about 850 feet in the southern part. The total amount of water stored in the fresh-water zone is estimated to be 21 million acre-feet based on specific yield of 0.20. Minimum recharge to the aquifer in 1975 is estimated to be 190 acre-feet per square mile or about 10 percent of the annual precipitation. Total minimum recharge to the aquifer in the study area in 1975 is estimated to be 129,000 acre-feet. Streams in the area are the principal means of ground-water discharge; the amount of discharge is essentially the same as recharge. The amount of groundwater used for municipal and rural water supply in 1975 is estimated to have been 5,000 acre-feet; a similar amount may have been used for industrial purposes. As a result of pumping, the potentiometric surface in 1975 had been lowered about 200 feet in the vicinity of Edmond and about 100 feet in the vicinity of Nichols Hills. Chemical analyses of water from the aquifer indicates that hardness is greater in the upper part of the aquifer than in the lower part, and that sulfate, chloride, and dissolved solids increase with depth. Reported yields of wells more than 250 feet deep range from 70 to 475 gallons per minute and average 240 gallons per minute. Potential well yields range from 225 gallons per minute when the fresh-water zone is 350 feet thick to about 550 gallons per minute where the fresh water zone is 850 feet thick. These estimates of potential yield are based on an available drawdown of half the thickness of the fresh-water zone and a specific capacity of 1.3 gallons per minute per foot. Intrusion of saline water into the fresh-water zone is a potential threat to water quality in the aquifer if the pressure head in the fresh-water zone is reduced sufficiently to allow upconing of saline water. One way to avoid the problem of upconing is by steady pumping at low rates from widely spaced wells; however, information required to determine pumping rates and well spacing is not available. For proper aquifer management the distribution of wells and rates of withdrawals should be designed to capture maximum recharge to the ground-water system. This may be accomplished by developing regional ground-water gradients that are sufficiently large to move water to pumpage centers but not so steep as to cause upconing of saline water or excessive water-level declines.

STRATOSPHERIC TEMPERATURES AND WATER LOSS FROM MOIST GREENHOUSE ATMOSPHERES OF EARTH-LIKE PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasting, James F.; Kopparapu, Ravi K.; Chen, Howard, E-mail: jfk4@psu.edu, E-mail: hwchen@bu.edu

A radiative-convective climate model is used to calculate stratospheric temperatures and water vapor concentrations for ozone-free atmospheres warmer than that of modern Earth. Cold, dry stratospheres are predicted at low surface temperatures, in agreement with recent 3D calculations. However, at surface temperatures above 350 K, the stratosphere warms and water vapor becomes a major upper atmospheric constituent, allowing water to be lost by photodissociation and hydrogen escape. Hence, a moist greenhouse explanation for loss of water from Venus, or some exoplanet receiving a comparable amount of stellar radiation, remains a viable hypothesis. Temperatures in the upper parts of such atmospheresmore » are well below those estimated for a gray atmosphere, and this factor should be taken into account when performing inverse climate calculations to determine habitable zone boundaries using 1D models.« less

Potential effects of surface coal mining on the hydrology of the Little Bear Creek area, Moorhead coal field, southeastern Montana

USGS Publications Warehouse

McClymonds, N.E.

1986-01-01

The Little Bear Creek area of the Moorhead Coal Field, 27 miles south of Ashland, Montana, contains large reserves of Federally owned coal that have been identified for potential lease sale. A hydrologic study was conducted in the area to describe existing hydrologic system and to assess potential effects of surface mining on local water resources. Hydrologic data collected from private wells, observation wells, test holes and springs indicate that the aquifers are coal and sandstone beds in the upper part of the Tongue River Member, Fort Union Formation (Paleocene age), and sand and gravel layers of valley alluvium (Pleistocene and Holocene age). Surface water is available from ephemeral flow along stretches of the main streams, and from stock ponds throughout the area. Mining the Anderson and Dietz coal beds would destroy one stock well and several stock ponds, would possibly interfere with the flow of one spring, and would lower the potentiometric surface within the coal and sandstone aquifers. The alluvial aquifer beneath Little Bear Creek and Davidson Draw would be removed at the mine site, as would sandstone and coal aquifers above the mine floor. Although mining would alter existing hydrologic systems, alternative water supplies are available. Planned structuring of the spoils and reconstruction of the alluvial aquifers could minimize downstream water-quality degradation. (USGS)

Nitrate in groundwater and water sources used by riparian trees in an agricultural watershed: A chemical and isotopic investigation in southern Minnesota

USGS Publications Warehouse

Komor, Stephen C.; Magner, Joseph A.

1996-01-01

This study evaluates processes that affect nitrate concentrations in groundwater beneath riparian zones in an agricultural watershed. Nitrate pathways in the upper 2 m of groundwater were investigated beneath wooded and grass-shrub riparian zones next to cultivated fields. Because trees can be important components of the overall nitrate pathway in wooded riparian zones, water sources used by riparian trees and possible effects of trees on nitrate concentrations in groundwater were also investigated. Average nitrate concentrations in shallow groundwater beneath the cultivated fields were 5.5 mg/L upgradient of the wooded riparian zone and 3.5 mg/L upgradient of the grass-shrub zone. Shallow groundwater beneath the fields passed through the riparian zones and discharged into streams that had average nitrate concentrations of 8.5 mg/L (as N). Lateral variations of δD values in groundwater showed that mixing among different water sources occurred beneath the riparian zones. In the wooded riparian zone, nitrate concentrations in shallow groundwater were diluted by upwelling, nitrate-poor, deep groundwater. Upwelling deep groundwater contained ammonium with a δ15N of 5‰ that upon nitrification and mixing with nitrate in shallow groundwater caused nitrate δ15N values in shallow groundwater to decrease by as much as 19.5‰. Stream water penetrated laterally beneath the wooded riparian zone as far as 19 m from the stream's edge and beneath the grass-shrub zone as far as 27 m from the stream's edge. Nitrate concentrations in shallow groundwater immediately upgradient of where it mixed with stream water averaged 0.4 mg/L in the wooded riparian zone and 0.8 mg/L near the grass-shrub riparian zone. Nitrate concentrations increased toward the streams because of mixing with nitrate-rich stream water. Because nitrate concentrations were larger in stream water than shallow groundwater, concentrated nitrate in the streams cannot have come from shallow groundwater at these sites. Water sources of riparian trees were identified by comparing δD values of sap water, soil water, groundwater, and stream water. Soil water was the main water source for trees in the outer 4 to 6 m of one part of the wooded riparian zone and outer 10 m of another part. Groundwater was a significant water source for trees closer to the streams where the water table was less than about 2.1 to 2.7 m below the surface. No evidence was found in the nitrate concentration profiles that trees close to the streams that took up groundwater through their roots also took up nitrate from groundwater. The lack of such evidence is attributed to the nitrate concentration profiles being insufficiently sensitive indicators of nitrate removal by trees.

Hydrogeologic Framework and Occurrence and Movement of Ground Water in the Upper Humboldt River Basin, Northeastern Nevada

USGS Publications Warehouse

Plume, Russell W.

2009-01-01

The upper Humboldt River basin encompasses 4,364 square miles in northeastern Nevada, and it comprises the headwaters area of the Humboldt River. Nearly all flow of the river originates in this area. The upper Humboldt River basin consists of several structural basins, in places greater than 5,000 feet deep, in which basin-fill deposits of Tertiary and Quaternary age and volcanic rocks of Tertiary age have accumulated. The bedrock of each structural basin and adjacent mountains is composed of carbonate and clastic sedimentary rocks of Paleozoic age and crystalline rocks of Paleozoic, Mesozoic and Cenozoic age. The permeability of bedrock generally is very low except for carbonate rocks, which can be very permeable where circulating ground water has widened fractures through geologic time. The principal aquifers in the upper Humboldt River basin occur within the water-bearing strata of the extensive older basin-fill deposits and the thinner, younger basin-fill deposits that underlie stream flood plains. Ground water in these aquifers moves from recharge areas along mountain fronts to discharge areas along stream flood plains, the largest of which is the Humboldt River flood plain. The river gains flow from ground-water seepage to its channel from a few miles west of Wells, Nevada, to the west boundary of the study area. Water levels in the upper Humboldt River basin fluctuate annually in response to the spring snowmelt and to the distribution of streamflow diverted for irrigation of crops and meadows. Water levels also have responded to extended periods (several years) of above or below average precipitation. As a result of infiltration from the South Fork Reservoir during the past 20 years, ground-water levels in basin-fill deposits have risen over an area as much as one mile beyond the reservoir and possibly even farther away in Paleozoic bedrock.

Effects of two stormwater management methods on the quality of water in the upper Biscayne aquifer at two commercial areas in Dade County, Florida

USGS Publications Warehouse

McKenzie, D.J.; Irwin, G.A.

1988-01-01

This study is part of a continued effort to assess the effects of urban stormwater recharge on the water quality of the Biscayne aquifer in southeast Florida. In this report, the water-quality effects on shallow ground water resulting from stormwater disposal by exfiltration trench and grassy swale were investigated at two small commercial areas in Dade County, Florida. One study area (airport ) was located near the Miami International Airport and had a drainage area of about 10 acres overlying a sandy soil; the other study area ( free zone ) was located at the Miami International Free Trade Zone and had a drainage area of about 20 acres overlying limestone. The monitoring design for each study area consisted of seven sites and included water-quality sampling of the stormwater in the catch basin of the exfiltration trench, ground water from two wells 1 foot from the trench (trench wells), two wells 20 feet from the trench, and ground water from two wells at the swale from April 1985 through May 1986. Eleven water-quality variables (target variables) commonly found in high levels in urban stormwater runoff were used as tracers to estimate possible changes in ground-water quality that may have been caused by stormwater recharge. Comparison of the distribution of target variables indicated that the concentrations tended to be greater in the stormwater in the exfiltration trench than in water from the two wells 1 foot from the trench at both study areas. The concentration difference for several target variables was statistically significant at the 5-percent level. Lead, for example, had median concentrations of 23 and 4 micrograms per liter, respectively, in stormwater and water from the two trench wells at the airport study area, and 38 and 2 micrograms per liter, respectively, in stormwater and groundwater at the free zone. Similar reductions in concentrations between stormwater and water from the two trench wells were indicated for zinc at both study areas and also for nitrogen, phosphorus, and organic content at the free zone. This trend suggested that the exfiltration trench at both study areas may function as a partial trap for some chemical substances present in stormwater. A comparison of the distribution of the 11 target variables and major ionic composition in water from the two trench wells and the two wells 20 feet from the trench did not indicate a notable horizontal stratification at either study area. A vertical difference between 10 and 15 feet, however, was indicated at the free zone with major ions in greater concentrations at 15 feet. The vertical variability in groundwater near the trench at the free zone may have been the result of stormwater dilution in the upper (10-foot ) zone. The groundwater quality at the swale was quite dissimilar to that near the exfiltration trench at both the airport and free zone study areas. Data indicated that the groundwater environment at both sales was anaerobic as evidenced by abundant ammonia nitrogen and iron and trace levels of sulfate. Anaerobic conditions at the swale may have been the result of poor drainage and high organic content of soils. Significant biochemical cycling in the ground water at the swales precluded any assessment of quality effects that may result from storm-water infiltration.

Depth-dependent groundwater quality sampling at City of Tallahassee test well 32, Leon County, Florida, 2013

USGS Publications Warehouse

McBride, W. Scott; Wacker, Michael A.

2015-01-01

A test well was drilled by the City of Tallahassee to assess the suitability of the site for the installation of a new well for public water supply. The test well is in Leon County in north-central Florida. The U.S. Geological Survey delineated high-permeability zones in the Upper Floridan aquifer, using borehole-geophysical data collected from the open interval of the test well. A composite water sample was collected from the open interval during high-flow conditions, and three discrete water samples were collected from specified depth intervals within the test well during low-flow conditions. Water-quality, source tracer, and age-dating results indicate that the open interval of the test well produces water of consistently high quality throughout its length. The cavernous nature of the open interval makes it likely that the highly permeable zones are interconnected in the aquifer by secondary porosity features.

Sulfur speciation and sulfide oxidation in the water column of the Black Sea

NASA Astrophysics Data System (ADS)

Luther, George W., III; Church, Thomas M.; Powell, David

We have applied sulfur speciation techniques to understand the chemistry and cycling of sulfur in Black Sea waters. The only reduced dissolved inorganic sulfur species detected (above the low minimum detection limits of the voltammetric methods employed) in the water column was hydrogen sulfide. The maximum concentration of sulfide (423 μM) is similar to previous reports. Using a cathodic stripping square wave voltammetry (CSSWV) method for nanomolar levels of sulfide, we determined the precise boundary between the "free" hydrogen sulfide (sulfidic) zone and the upper (oxic/suboxic) water column at the two stations studied. This boundary has apparently moved up by about 50 m in the past 20 years. Our results help demonstrate three chemically distinct zones of water in the central basin of the Black Sea: (1) the oxic [0-65 m], (2) the anoxic/nonsulfidic [65-100 m] and (3) the sulfidic [>100 m]. Sulfide bound to metals ("complexed" sulfide) is observed in both the oxic and anoxic/nonsulfidic zones of the water column. This supports previous studies on metal sulfide forms. From the electrochemical data, it is possible to estimate the strength of the complexation of sulfide to metals (log K = 10 to 11). Thiosulfate and sulfite were below our minimum detectable limit (MDL) of 50 nM using CSSWV. Elemental sulfur (MDL 5 nM) was detected below the onset of the hydrogen sulfide zone (90-100 m) with a maximum of 30-60 nM near 120 m. The sulfur speciation results for the Black Sea are lower by one order of magnitude or more than other marine systems such as the Cariaco Trench and salt marshes. New HPLC techniques were applied to detect thiols at submicromolar levels. The presence of thiols (2-mercaptoethylamine, 2-mercaptoethanol, N-acetylcysteine and glutathione) is correlated with the remineralization of organic matter at the oxic and anoxic/nonsulfidic interface. Water samples collected from the upper 50 m of the sulfidic zone showed significant sulfide oxidation on storage onboard ship even though they were filtered (0.2 μm) and handled to exclude oxygen contamination. Chemical additives such as formaldehyde, glutaraldehyde, hydroxylamine and ascorbic acid prevented or retarded the sulfide loss. Thiosulfate and azide did not inhibit sulfide loss. These studies suggest an anaerobic chemical oxidation of sulfide rather than a biological oxidation on stored and filtered samples.

The geology and petroleum potential of the North Afghan platform and adjacent areas (northern Afghanistan, with parts of southern Turkmenistan, Uzbekistan and Tajikistan)

NASA Astrophysics Data System (ADS)

Brookfield, Michael E.; Hashmat, Ajruddin

2001-10-01

The North Afghan platform has a pre-Jurassic basement unconformably overlain by a Jurassic to Paleogene oil- and gas-bearing sedimentary rock platform cover, unconformably overlain by Neogene syn- and post-orogenic continental clastics. The pre-Jurassic basement has four units: (1) An ?Ordovician to Lower Devonian passive margin succession developed on oceanic crust. (2) An Upper Devonian to Lower Carboniferous (Tournaisian) magmatic arc succession developed on the passive margin. (3) A Lower Carboniferous (?Visean) to Permian rift-passive margin succession. (4) A Triassic continental magmatic arc succession. The Mesozoic-Palaeogene cover has three units: (1) A ?Late Triassic to Middle Jurassic rift succession is dominated by variable continental clastics. Thick, coarse, lenticular coal-bearing clastics were deposited by braided and meandering streams in linear grabens, while bauxites formed on the adjacent horsts. (2) A Middle to Upper Jurassic transgressive-regressive succession consists of mixed continental and marine Bathonian to Lower Kimmeridgian clastics and carbonates overlain by regressive Upper Kimmeridgian-Tithonian evaporite-bearing clastics. (3) A Cretaceous succession consists of Lower Cretaceous red beds with evaporites, resting unconformably on Jurassic and older deposits, overlain (usually unconformably) by Cenomanian to Maastrichtian shallow marine limestones, which form a fairly uniform transgressive succession across most of Afghanistan. (4) A Palaeogene succession rests on the Upper Cretaceous limestones, with a minor break marked by bauxite in places. Thin Palaeocene to Upper Eocene limestones with gypsum are overlain by thin conglomerates, which pass up into shales with a restricted brackish-water ?Upper Oligocene-?Lower Miocene marine fauna. The Neogene succession consists of a variable thickness of coarse continental sediments derived from the rising Pamir mountains and adjacent ranges. Almost all the deformation of the North Afghan platform began in the Miocene. Oil and gas traps are mainly in Upper Jurassic carbonates and Lower Cretaceous sandstones across the entire North Afghan block. Upper Jurassic carbonate traps, sealed by evaporites, occur mainly north of the southern limit of the Upper Jurassic salt. Lower Cretaceous traps consist of fine-grained continental sandstones, sealed by Aptian-Albian shales and siltstones. Upper Cretaceous-Palaeocene carbonates, sealed by Palaeogene shales are the main traps along the northern edge of the platform and in the Tajik basin. Almost all the traps are broad anticlines related to Neogene wrench faulting, in this respect, like similar traps along the San Andreas fault. Hydrocarbon sources are in the Mesozoic section. The Lower-Middle Jurassic continental coal-bearing beds provide about 75% of the hydrocarbons; the Callovian-Oxfordian provides about 10%; the Neocomian a meagre 1%, and the Aptian-Albian about 14%. The coal-bearing source rocks decrease very markedly in thickness southwards cross the North Afghan platform. Much of the hydrocarbon generation probably occurred during the Late Cretaceous-Paleogene and migrated to structural traps during Neogene deformation. Since no regional structural dip aids southward hydrocarbon migration, and since the traps are all structural and somewhat small, then there is little chance of very large petroleum fields on the platform. Nevertheless, further studies of the North Afghan platform should be rewarding because: (a) the traps of strike-slip belts are difficult to find without detailed exploration; (b) the troubles of the last 20 years mean that almost no exploration has been done; and, (c) conditions may soon become more favorable. There should be ample potential for oil, and particularly gas, discoveries especially in the northern and western parts of the North Afghan platform.

An unusual occurrence of arsenic-bearing pyrite in the Upper Freeport coal bed, West-Central Pennsylvania

USGS Publications Warehouse

Ruppert, L.F.; Minkin, J.A.; McGee, J.J.; Cecil, C.B.

1992-01-01

Scanning electron microscopy and electron microprobe analysis were used to identify a rare type of As-bearing pyrite in selected specific gravity separates from the Pennsylvanian age Upper Freeport coal bed, west-central Pennsylvania. Arsenic was detected mainly in cell-wall replacement pyrite where concentrations ranged from nondetectable to 1.9 wt %. Although the majority of arsenic-bearing pyrite in the Upper Freeport coal bed is concentrated in massive and late diagenetic pyrite morphologies, the rarer As-bearing cell-replacement pyrite was observed in both light and heavy gravity separates from the three coal facies examined. Arsenic was occasionally detected in cell-filling replacement pyrite, but this As appears to be an artifact produced by signals from underlying and/or adjacent As-bearing cell-wall replacement pyrite. It is postulated that some plants of the Upper Freeport paleoswamp may have biomethylated As, which later could have been converted to dimethylarsine or other volatile organoarsenic compounds by either biologically or chemically driven processes. Once liberated, the arsenic may have been incorporated into pyrite during pyritization of the cell walls. The As incorporation occurred early, before significant compaction of the peat, because the pyritized cell walls are not compacted.

Geohydrology of the lower Apalachicola-Chattahoochee-Flint River basin, southwestern Georgia, northwestern Florida, and southeastern Alabama

USGS Publications Warehouse

Torak, Lynn J.; Painter, Jaime A.

2006-01-01

The lower Apalachicola-Chattahoochee-Flint (ACF) River Basin contains about 4,600 square miles of karstic and fluvial plains and nearly 100,000 cubic miles of predominantly karst limestone connected hydraulically to the principal rivers and lakes in the Coastal Plain of southwestern Georgia, northwestern Florida, and southwestern Alabama. Sediments of late-middle Eocene to Holocene in hydraulic connection with lakes, streams, and land surface comprise the surficial aquifer system, upper semiconfining unit, Upper Floridan aquifer, and lower semiconfining unit and contribute to the exchange of ground water and surface water in the stream-lake-aquifer flow system. Karst processes, hydraulic properties, and stratigraphic relations limit ground-water and surface-water interaction to the following hydrologic units of the stream-lake-aquifer flow system: the surficial aquifer system, upper semiconfining unit, Upper Floridan aquifer, and lower confining unit. Geologic units corresponding to these hydrologic units are, in ascending order: Lisbon Formation; Clinchfield Sand; Ocala, Marianna, Suwannee, and Tampa Limestones; Hawthorn Group; undifferentiated overburden (residuum); and terrace and undifferentiated (surficial) deposits. Similarities in hydraulic properties and direct or indirect interaction with surface water allow grouping sediments within these geologic units into the aforementioned hydrologic units, which transcend time-stratigraphic classifications and define the geohydrologic framework for the lower ACF River Basin. The low water-transmitting properties of the lower confining unit, principally the Lisbon Formation, allow it to act as a nearly impermeable base to the stream-lake-aquifer flow system. Hydraulic connection of the surficial aquifer system with surface water and the Upper Floridan aquifer is direct where sandy deposits overlie the limestone, or indirect where fluvial deposits overlie clayey limestone residuum. The water level in perched zones within the surficial aquifer system fluctuates independently of water-level changes in the underlying aquifer, adjacent streams, or lakes. Where the surficial aquifer system is connected with surface water and the Upper Floridan aquifer, water-table fluctuations parallel those in adjacent streams or the underlying aquifer. More...

Temporal variability of dissolved iron species in the mesopelagic zone at Ocean Station PAPA

NASA Astrophysics Data System (ADS)

Schallenberg, Christina; Ross, Andrew R. S.; Davidson, Ashley B.; Stewart, Gillian M.; Cullen, Jay T.

2017-08-01

Deposition of atmospheric aerosols to the surface ocean is considered an important mechanism for the supply of iron (Fe) to remote ocean regions, but direct observations of the oceanic response to aerosol deposition are sparse. In the high nutrient, low chlorophyll (HNLC) subarctic Pacific Ocean we observed a dissolved Fe and Fe(II) anomaly at depth that is best explained as the result of aerosol deposition from Siberian forest fires in May 2012. Interestingly, there was no evidence of enhanced dFe concentrations in surface waters, nor was there a detectable phytoplankton bloom in response to the suspected aerosol deposition. Dissolved Fe (dFe) and Fe(II) showed the strongest enhancement in the subsurface oxygen deficient zone (ODZ), where oxygen concentrations <50 μmol kg-1 are prevalent. In the upper 200 m, dFe concentrations were at or below historic background levels, consistent with a short residence time of aerosol particles in surface waters and possible scavenging loss of dFe. Aerosol toxicity and/or dominance of particle scavenging over dissolution of Fe in the upper water column may have contributed to the lack of a strong phytoplankton response.

PILOT-SCALE REMOVAL OF FLUORIDE FROM LEGACY PLUTONIUM MATERIALS USING VACUUM SALT DISTILLATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, R. A.; Pak, D. J.

2012-09-11

Between September 2009 and January 2011, the Savannah River National Laboratory (SRNL) and HB-Line designed, developed, tested, and successfully deployed a system for the distillation of chloride salts. In 2011, SRNL adapted the technology for the removal of fluoride from fluoride-bearing salts. The method involved an in situ reaction between potassium hydroxide (KOH) and the fluoride salt to yield potassium fluoride (KF) and the corresponding oxide. The KF and excess KOH can be distilled below 1000{deg}C using vacuum salt distillation (VSD). The apparatus for vacuum distillation contains a zone heated by a furnace and a zone actively cooled using eithermore » recirculated water or compressed air. During a vacuum distillation operation, a sample boat containing the feed material is placed into the apparatus while it is cool, and the system is sealed. The system is evacuated using a vacuum pump. Once a sufficient vacuum is attaned, heating begins. Volatile salts distill from the heated zone to the cooled zone where they condense, leaving behind the non-volatile material in the feed boat. Studies discussed in this report were performed involving the use of non-radioactive simulants in small-scale and pilot-scale systems as well as radioactive testing of a small-scale system with plutonium-bearing materials. Aspects of interest include removable liner design considerations, boat materials, in-line moisture absorption, and salt deposition.« less

Groundwater and solute transport modeling at Hyporheic zone of upper part Citarum River

NASA Astrophysics Data System (ADS)

Iskandar, Irwan; Farazi, Hendy; Fadhilah, Rahmat; Purnandi, Cipto; Notosiswoyo, Sudarto

2017-06-01

Groundwater and surface water interaction is an interesting topic to be studied related to the water resources and environmental studies. The study of interaction between groundwater and river water at the Upper Part Citarum River aims to know the contribution of groundwater to the river or reversely and also solute transport of dissolved ions between them. Analysis of drill logs, vertical electrical sounding at the selected sections, measurement of dissolved ions, and groundwater modeling were applied to determine the flow and solute transport phenomena at the hyporheic zone. It showed the hyporheic zone dominated by silt and clay with hydraulic conductivity range from 10-4∼10-8 m/s. The groundwater flowing into the river with very low gradient and it shows that the Citarum River is a gaining stream. The groundwater modeling shows direct seepage of groundwater into the Citarum River is only 186 l/s, very small compared to the total discharge of the river. Total dissolved ions of the groundwater ranged from 200 to 480 ppm while the river water range from 200 to 2,000 ppm. Based on solute transport modeling it indicates dissolved ions dispersion of the Citarum River into groundwater may occur in some areas such as Bojongsoang-Dayeuh Kolot and Nanjung. This situation would increase the dissolved ions in groundwater in the region due to the contribution of the Citarum River. The results of the research can be a reference for further studies related to the mechanism of transport of the pollutants in the groundwater around the Citarum River.

Increased oil production and reserves from improved completion techniques in the Bluebell field, Uinta Basin, Utah. Tenth quarterly technical progress report, January 1, 1996--March 31, 1996. Revised

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allison, M.L.

1996-05-13

The objective of this project is to increase oil production and reserves in the Uinta Basin by demonstrating improved completion techniques. Low productivity of Uinta Basin will is caused by gross production intervals of several thousand feet that contain perforated thief zones, water-bearing zones, and unperforated oil- bearing intervals. Geologic and engineering characterization and computer simulation of the Green River and Wasatch Formations in the Bluefell field will determine reservoir heterogeneities related to fractures and depositional trends. This will be followed by techniques based on the reservoir characterization. Transfer of the project results will be an ongoing component of themore » project. Data (net pay thickness, porosity, and water saturation) of more than 100 individuals beds in he lower Green River and Wasatch Formations were used to generate geostatistical realization (numerical- representation) of the reservoir properties. The data set was derived from the Michelle Ute and Malnar Pike demonstration wells and 22 other wells in a 20 (52 km{sup 2}) square-mile area. Beds were studied independently of each other. Principles of sequential Gaussian simulations were used to generate geostatistical realizations of the beds.« less

Occurrence and availability of ground water in the Athens region, northeastern Georgia

USGS Publications Warehouse

Radtke, D.B.; Cressler, C.W.; Perlman, H.A.; Blanchard, H.E.; McFadden, K.W.; Brooks, Rebekah

1986-01-01

A study was conducted to assess the occurrence and availability of groundwater in the crystalline rocks of the Piedmont area in northeastern Georgia and to determine whether groundwater is a viable alternative or supplemental source for industrial, public and private supplies. The area is underlain by a variety of metamorphic and igneous rocks. The quantity of water that a rock unit can supply to wells is determined by the number, capacity, and interconnection of the secondary openings. Of an estimated 10,000 successful wells drilled in the Athens Region, 972 wells are reported by drilling contractors to supply from 20 to 300 gal/min. Studies of well sites revealed that high yielding wells can be developed only where the water bearing units have undergone significant increases in secondary permeability. This occurs mainly in association with (1) contact zones between rock units of contrasting character, (2) contact zones within multilayered rock units, (3) fault zones, (4) stress-relief fractures, and (5) shear zones. Groundwater may be a viable alternative or supplemental source for industrial, public, and private supplies in much of the Athens Region. In 1980, groundwater made up 38% (18 million gal/day) of the total water used in the area. Yields of 20 to more than 200 gal/min are obtained from wells throughout most of the region, and the water is generally of good chemical quality and is suitable for drinking and many other uses. Concentrations of dissolved constituents are fairly consistent throughout the area. Except for iron, manganese, and fluoride, dissolved constituents rarely exceed drinking water standards. (Lantz-PTT)

Chemical and Hydrologic Data From the Cement Creek and Upper Animas River Confluence and Mixing Zone, Silverton, Colorado, September 1997

USGS Publications Warehouse

Schemel, Laurence E.; Cox, Marisa H.

2007-01-01

Cement Creek, an acidic tributary, discharges into the circum-neutral Animas River (pH>7) in Silverton, Colorado located in the high-elevation San Juan Mountains. Mixing of Animas River water with acidic metal rich Cement Creek water raises water pH and produces metal precipitates. This report presents selected anion, cation, chloride, and sulfate data along with hydrologic data highlighting the mixing of these streams during the low-flow period in late summer 1997.

Characterization of aquifer heterogeneity using Cyclostratigraphy and geophysical methods in the upper part of the Karstic Biscayne Aquifer, Southeastern Florida

USGS Publications Warehouse

Cunningham, Kevin J.; Carlson, Janine L.; Wingard, G. Lynn; Robinson, Edward; Wacker, Michael A.

2004-01-01

This report identifies and characterizes candidate ground-water flow zones in the upper part of the shallow, eogenetic karst limestone of the Biscayne aquifer in the Lake Belt area of north-central Miami-Dade County using cyclostratigraphy, ground-penetrating radar (GPR), borehole geophysical logs, and continuously drilled cores. About 60 miles of GPR profiles were used to calculate depths to shallow geologic contacts and hydrogeologic units, image karst features, and produce qualitative views of the porosity distribution. Descriptions of the lithology, rock fabrics, and cyclostratigraphy, and interpretation of depositional environments of 50 test coreholes were linked to the geophysical interpretations to provide an accurate hydrogeologic framework. Molluscan and benthic foraminiferal paleontologic constraints guided interpretation of depositional environments represented by rockfabric facies. Digital borehole images were used to characterize and quantify large-scale vuggy porosity. Preliminary heat-pulse flowmeter data were coupled with the digital borehole image data to identify candidate ground-water flow zones. Combined results show that the porosity and permeability of the karst limestone of the Biscayne aquifer have a highly heterogeneous and anisotropic distribution that is mostly related to secondary porosity overprinting vertical stacking of rock-fabric facies within high-frequency cycles (HFCs). This distribution of porosity produces a dual-porosity system consisting of diffuse-carbonate and conduit flow zones. The nonuniform ground-water flow in the upper part of the Biscayne aquifer is mostly localized through secondary permeability, the result of solution-enlarged carbonate grains, depositional textures, bedding planes, cracks, root molds, and paleokarst surfaces. Many of the resulting pore types are classified as touching vugs. GPR, borehole geophysical logs, and whole-core analyses show that there is an empirical relation between formation porosity, permeability, formation electrical conductivity, and GPR reflection amplitudes? as porosity and permeability increase, formation electrical conductivity increases and reflection amplitude decreases. This relation was observed throughout the entire vertical and lateral section of the upper part of the Biscayne aquifer in the study area. Further, upward-shallowing brackish- or freshwatercapped cycles of the upper part of the Fort Thompson Formation show low-amplitude reflections near their base that correspond to relatively higher porosity and permeability. This distribution is related to a systematic vertical stacking of rock-fabric facies within the cycle. Inferred flow characteristics of the porosity distribution within the upper part of the Biscayne aquifer were used to identify four ground-water flow classes, with each characterized by a discrete pore system that affects vertical and horizontal groundwater flow: (1) a low-permeability peat, muck, and marl ground-water flow class; (2) a horizontal conduit ground-water flow class; (3) a leaky, low-permeability ground-water flow class; and (4) a diffuse-carbonate ground-water flow class. At the top of the Biscayne aquifer, peat, muck, and marl can combine to form a relatively low-permeability layer of Holocene sediment that water moves through slowly. Most horizontal conduit flow is inferred to occur along touching vugs in portions of the following rock-fabric facies: (1) touchingvug pelecypod floatstone and rudstone, (2) sandy touching-vug pelecypod floatstone and rudstone, (3) vuggy wackestone and packstone, (4) laminated peloid grainstone and packstone, (5) peloid grainstone and packstone, and (6) peloid wackestone and packstone. Gastropod floatstone and rudstone, mudstone and wackestone, and pedogenic limestone rock-fabric facies are the main hosts for leaky, low-permeability units. This study provides evidence that the limestone that spans the base of the Miami Limestone and top of the Fort Thompson

Partial tooth gear bearings

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

2010-01-01

A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.

Where do arc magmas differentiate? A seismic and geochemical search for active, deep crustal MASH zones

NASA Astrophysics Data System (ADS)

Pu, X.; Delph, J. R.; Shimizu, K.; Rasmussen, D. J.; Ratschbacher, B. C.

2017-12-01

Deep zones of mixing, assimilation, storage, and homogenization (MASH) are thought to be one of the primary locations where primitive arc magmas stall, interact with crustal material, and differentiate. Support for deep crustal MASH zones is found in exposed crustal sections, where mafic-ultramafic lithologies occur in the lower crust. However, geophysical observations of active deep MASH zones are rare, and their ubiquity is difficult to assess solely based on geochemistry. Using a multidisciplinary approach, we investigate the role of deep crustal processing by investigating two contrasting arcs: the Central Volcanic Zone (CVZ) of the Andes, characterized by thick crust ( 60 km) and large volume silicic eruptions that extend into the back arc, and the Cascadia arc, characterized by thinner crust ( 40 km) and less evolved eruptions. In the southern Puna region of the CVZ, shear-wave velocities in the uppermost mantle are slow ( 3.9 km/s) compared to the minimum expected shear velocity for melt-free mantle lithosphere ( 4.2 km/s). This is consistent with the presence of a melt-bearing MASH zone near the crust-mantle transition. Sr isotopes indicate the magmas interacted with continental crust, and elevated Dy/Yb ratios suggest this process occurred in the garnet stability field (> 1 GPa). Major element signatures (e.g., ASI vs. SiO2) also suggest contribution from partial melting of the lower crust. The signature of lower crustal differentiation (high Dy/Yb) is also observed in the nearby ignimbrites from Cerro Galan, despite the presence of a large slow velocity body at depths too shallow for garnet stability, suggesting that the geochemical signatures of deep MASH zones may be retained regardless of whether magmas stall at shallower depths. Similarly elevated Dy/Yb ratios and slow shear-wave velocities in the upper mantle are common in the CVZ, implying deep MASH zones are pervasive there. A similar approach is applied to Cascadia, where seismic and geochemical signatures of lower crustal processing are weaker than those in the CVZ. The strongest evidence for a deep MASH zone is found at Rainier, where upper mantle velocities are slow and slightly elevated Dy/Yb ratios in evolved melts indicate differentiation in the presence of garnet. Our results suggest deep MASH zones are more common in the CVZ than Cascadia.

Redox-influenced seismic properties of upper-mantle olivine

NASA Astrophysics Data System (ADS)

Cline, C. J., II; Faul, U. H.; David, E. C.; Berry, A. J.; Jackson, I.

2018-03-01

Lateral variations of seismic wave speeds and attenuation (dissipation of strain energy) in the Earth’s upper mantle have the potential to map key characteristics such as temperature, major-element composition, melt fraction and water content. The inversion of these data into meaningful representations of physical properties requires a robust understanding of the micromechanical processes that affect the propagation of seismic waves. Structurally bound water (hydroxyl) is believed to affect seismic properties but this has yet to be experimentally quantified. Here we present a comprehensive low-frequency forced-oscillation assessment of the seismic properties of olivine as a function of water content within the under-saturated regime that is relevant to the Earth’s interior. Our results demonstrate that wave speeds and attenuation are in fact strikingly insensitive to water content. Rather, the redox conditions imposed by the choice of metal sleeving, and the associated defect chemistry, appear to have a substantial influence on the seismic properties. These findings suggest that elevated water contents are not responsible for low-velocity or high-attenuation structures in the upper mantle. Instead, the high attenuation observed in hydrous and oxidized regions of the upper mantle (such as above subduction zones) may reflect the prevailing oxygen fugacity. In addition, these data provide no support for the hypothesis whereby a sharp lithosphere–asthenosphere boundary is explained by enhanced grain boundary sliding in the presence of water.

Soil salinization in different natural zones of intermontane depressions in Tuva

NASA Astrophysics Data System (ADS)

Chernousenko, G. I.; Kurbatskaya, S. S.

2017-11-01

Soil salinization features in semidesert, dry steppe, and chernozemic steppe zones within intermontane depressions in the central part of the Tuva Republic are discussed. Chernozems, chestnut soils, and brown desert-steppe soils of these zones are usually nonsaline. However, salinization of these zonal soils is possible in the case of the presence of salt-bearing parent materials (usually, the derivatives of Devonian deposits). In different natural zones of the intermontane depressions, salt-affected soils are mainly allocated to endorheic lake basins, where they are formed in places of discharge of mineral groundwater, and to river valleys. The composition and content of salts in the natural waters are dictated by the local hydrogeological conditions. The total content of dissolved solids in lake water varies from 1 to 370 g/L; the water is usually of the sulfate-chloride or chloride-sulfate salinity type; in some cases, soda-sulfate water is present. Soil salinity around the lakes is usually of the chloride-sulfate-sodium type; gypsum is often present in the profiles. Chloride salinization rarely predominates in this part of Tuva, because chlorides are easily leached off from the mainly coarse-textured soils. In some cases, the predominance of magnesium over sodium is observed in the composition of dissolved salts, which may be indicative of the cryogenic transformation of soil salts. Soda-saline soils are present in all the considered natural zones on minor areas. It is hardly possible to make unambiguous statements about the dominance of the particular type of salinity in the given natural zones. Zonal salinity patterns are weakly expressed in salinization of hydromorphic soils. However, a tendency for more frequent occurrence of soda-saline soils in steppe landscapes and chloride-sulfate salinization (often, with participation of gypsum) in the dry steppe and semidesert landscapes is observed.

Changing palaeoenvironments and tetrapod populations in the Daptocephalus Assemblage Zone (Karoo Basin, South Africa) indicate early onset of the Permo-Triassic mass extinction

NASA Astrophysics Data System (ADS)

Viglietti, Pia A.; Smith, Roger M. H.; Rubidge, Bruce S.

2018-02-01

Important palaeoenvironmental differences are identified during deposition of the latest Permian Daptocephalus Assemblage Zone (DaAZ) of the South African Beaufort Group (Karoo Supergoup), which is also divided into a Lower and Upper subzone. A lacustrine floodplain facies association showing evidence for higher water tables and subaqueous conditions on the floodplains is present in Lower DaAZ. The change to well-drained floodplain facies association in the Upper DaAZ is coincident with a faunal turnover as evidenced by the last appearance of the dicynodont Dicynodon lacerticeps, the therocephalian Theriognathus microps, the cynodont Procynosuchus delaharpeae, and first appearance of the dicynodont Lystrosaurus maccaigi within the Ripplemead member. Considering the well documented 3-phased extinction of Karoo tetrapods during the Permo-Triassic Mass Extinction (PTME), the facies transition between the Lower and Upper DaAZ represents earlier than previously documented palaeoenvironmental changes associated with the onset of this major global biotic crisis.

Neogene biostratigraphy and paleoenvironments of Enewetak Atoll, equatorial Pacific Ocean

USGS Publications Warehouse

Cronin, T. M.; Bybell, L.M.; Brouwers, E.M.; Gibson, T.G.; Margerum, R.; Poore, R.Z.

1991-01-01

Micropaleontologic analyses of Neogene sediments from Enewetak Atoll, Marshall Islands, provide data on the age of lagoonal deposits, stratigraphic disconformities and the paleoenvironmental and subsidence history of the atoll. Benthic foraminifers, planktic foraminifers, calcareous nannofossils and ostracodes were studied from six boreholes, the deepest penetrating 1605 feet below the lagoon floor into upper Oligocene strata. The Oligocene-Miocene boundary occurs at about 1200 ft below the lagoon floor. The early and middle Miocene is characterized by brief periods of deposition and numerous hiatuses. Ostracodes and benthic foraminifers indicate a shallow-marine reefal environment with occasional brackish water conditions. Upper Miocene and lower Pliocene deposits placed in calcareous nannofossil Zones NN9-15 and in planktic foraminifer Zones N16-19 contain species-rich benthic microfaunas which indicate alternating reefal and brackish water mangrove environments. The upper Pliocene contains at least two major depositional hiatuses that coincide with a major faunal turnover in benthic foraminiferal and ostracode assemblages. The Quaternary is characterized by benthic microfaunas similar to those of modern atoll lagoons and is punctuated by at least 11 disconformities which signify periods of low sea level. Atoll subsidence rates during the last 10 Ma averaged 30 to 40 m/m.y. ?? 1991 Elsevier Science Publishers B.V. All rights reserved.

Wetland use and feeding by lesser scaup during spring migration across the upper Midwest, USA

USGS Publications Warehouse

Anteau, M.J.; Afton, A.D.

2009-01-01

Low food availability and forage quality and concomitant decreased lipid reserves of lesser scaup (Aythya affinis; hereafter scaup) during spring migration in the upper Midwest may partially explain reductions in the continental population of scaup. In springs 20042005, we examined wetland use and feeding activity of scaup on 356 randomly-selected wetlands within 6 regions in Iowa, Minnesota, and North Dakota. We examined wetland characteristics that favor high scaup use in 286 of these wetlands. We found that probabilities of wetland use and feeding by scaup increased with turbidity up to 45 and 30 NTU, respectively, but then declined at higher turbidity levels. Wetland use was positively correlated with size of open-water zone and amphipod densities, but was not correlated with chironomid densities. Feeding increased with amphipod density up to 26 m-3 and then declined at higher amphipod densities; scaup seemingly forage most efficiently at amphipod densities above 26 m -3. Wetland use was higher in North Dakota than in southern Minnesota and Iowa. Our results indicate that effective wetland restoration efforts to benefit scaup require maintaining abundant populations of amphipods (generally near 26 m-3 landscape geometric mean) in wetlands with large (> 500 m diameter) open-water zones throughout the upper Midwest, but especially within Iowa and southern Minnesota.

A preliminary assessment of sources of nitrate in springwaters, Suwannee River basin, Florida

USGS Publications Warehouse

Katz, B.G.; Hornsby, H.D.

1998-01-01

A cooperative study between the Suwannee River Water Management District (SRWMD) and the U.S. Geological Survey (USGS) is evaluating sources of nitrate in water from selected springs and zones in the Upper Floridan aquifer in the Suwannee River Basin. A multi-tracer approach, which consists of the analysis of water samples for naturally occurring chemical and isotopic indicators, is being used to better understand sources and chronology of nitrate contamination in the middle Suwannee River region. In July and August 1997, water samples were collected and analyzed from six springs and two wells for major ions, nutrients, and dissolved organic carbon. These water samples also were analyzed for environmental isotopes [18O/16O, D/H, 13C/12C, 15N/14N] to determine sources of water and nitrate. Chlorofluorocarbons (CCl3F, CCl2F2, and C2Cl3F3) and tritium (3H) were analyzed to assess the apparent ages (residence time) of springwaters and water from the Upper Floridan aquifer. Delta 15N-NO3 values in water from the six springs range from 3.94 per mil (Little River Springs) to 8.39 per mil (Lafayette Blue Spring). The range of values indicates that nitrate in the sampled springwaters most likely originates from a mixture of inorganic (fertilizers) and organic (animal wastes) sources, although the higher delta 15N-NO3 value for Lafayette Blue Spring indicates that an organic source of nitrogen is likely at this site. Water samples from the two wells sampled in Lafayette County have high delta 15N-NO3 values of 10.98 and 12.1 per mil, indicating the likelihood of an organic source of nitrate. These two wells are located near dairy and poultry farms, where leachate from animal wastes may contribute nitrate to ground water. Based on analysis of chlorofluorocarbons in ground water, the mean residence time of water in springs ranges from about 12 to 25 years. Chlorofluorocarbons-modeled recharge dates for water samples from the two shallow zones in the Upper Floridan aquifer range from 1985 to 1989.

Lateral variations of thermo-rheological structure in SE Tibet

NASA Astrophysics Data System (ADS)

Jiang, X.; Gong, W.

2017-12-01

The structure and geodynamics in SE Tibet is important to developing a full understanding of tectonic evolution of the Tibetan plateau. To investigate the lithospheric structure and deformation, we present thermo-rheological models for two transects across SE Tibet. The thermal models are determined by the heat flow and P-wave velocity models. Based on thermal models, the rheological models are constructed in the weak and strong cases where the lower crust is felsic or mafic granulite and the lithospheric mantle is wet or dry peridotite. The thermal models show an obvious high-temperature anomaly within the lithosphere beneath the Chuandian block. Strong lateral heterogeneity is present in the rheological modeling and corresponds to variations of thermal models. The Chuandian block demonstrates a lower level of lithospheric strength than its neighboring regions, which is in accord with the seismogenic layer distribution. Combining with a joint analysis of SKS splitting and GPS data, the crust and mantle is decoupled at a depth below the topmost mantle in SE Tibet. The strong crust beneath the South China plate and Indochina block has two brittle load-bearing layers in the crust, indicating the system is mechanically coupled. The crust beneath the Emeishan igneous province also has two brittle load-bearing layers, but the brittle deformation is restricted to the topmost 10 km of the upper and lower crust. In contrast, only one brittle load-bearing layer resides in the upper crust with the lower crust contributing little to the lithospheric strength at the location where low-velocity-high-conductivity zones have been recognized within the crust in the Chuandian block. This indicates that the crust beneath the Chuandian block becomes decoupled, as evidenced by the crustal anisotropy pattern.

New data on microbiota of the Middle Volgian substage in the Loino Section (Kirov oblast)

NASA Astrophysics Data System (ADS)

Ustinova, M. A.; Tesakova, E. M.

2017-05-01

The calcareous nannoplankton was established for the first time in Upper Volgian deposits of the Loino Section (Kirov oblast). Here, single coccolites of representatives of genus Watznaueria of wide stratigraphic and geographic distributions dominate. Representatives of genus Zuegrhabdotus are less common, whereas species of genus Polypodorhabdus are rare. The taxonomic composition of the calcareous nannoplankton assemblage does not allow us to distinguish the nannoplankton zone in the Loino Section, but it gives us an idea about its distribution at the Volgian Stage in the Russian Plate. As corresponding microfauna, foraminifers, assigned to the Lenticulina infravolgaensis-Saracenaria pravoslavlevi Zone, and ostracods were identified to substantiate the age of host deposits. The ostracod assemblage is assigned to the Macrodentina (Polydentina) subtriangularis Beds established on the Volga River left bank in deposits corresponding to the ammonite zones Panderi and Virgatus assigned to the middle Volgian substage. On the basis of ostracods, the warm-water well-aerating environment of the upper sublittoral (as deep as 50 m) was reconstructed.

A deep crustal fluid channel into the San Andreas Fault system near Parkfield, California

USGS Publications Warehouse

Becken, M.; Ritter, O.; Park, S.K.; Bedrosian, P.A.; Weckmann, U.; Weber, M.

2008-01-01

Magnetotelluric (MT) data from 66 sites along a 45-km-long profile across the San Andreas Fault (SAF) were inverted to obtain the 2-D electrical resistivity structure of the crust near the San Andreas Fault Observatory at Depth (SAFOD). The most intriguing feature of the resistivity model is a steeply dipping upper crustal high-conductivity zone flanking the seismically defined SAF to the NE, that widens into the lower crust and appears to be connected to a broad conductivity anomaly in the upper mantle. Hypothesis tests of the inversion model suggest that upper and lower crustal and upper-mantle anomalies may be interconnected. We speculate that the high conductivities are caused by fluids and may represent a deep-rooted channel for crustal and/or mantle fluid ascent. Based on the chemical analysis of well waters, it was previously suggested that fluids can enter the brittle regime of the SAF system from the lower crust and mantle. At high pressures, these fluids can contribute to fault-weakening at seismogenic depths. These geochemical studies predicted the existence of a deep fluid source and a permeable pathway through the crust. Our resistivity model images a conductive pathway, which penetrates the entire crust, in agreement with the geochemical interpretation. However, the resistivity model also shows that the upper crustal branch of the high-conductivity zone is located NE of the seismically defined SAF, suggesting that the SAF does not itself act as a major fluid pathway. This interpretation is supported by both, the location of the upper crustal high-conductivity zone and recent studies within the SAFOD main hole, which indicate that pore pressures within the core of the SAF zone are not anomalously high, that mantle-derived fluids are minor constituents to the fault-zone fluid composition and that both the volume of mantle fluids and the fluid pressure increase to the NE of the SAF. We further infer from the MT model that the resistive Salinian block basement to the SW of the SAFOD represents an isolated body, being 5-8km wide and reaching to depths >7km, in agreement with aeromagnetic data. This body is separated from a massive block of Salinian crust farther to the SW. The NE terminus of resistive Salinian crust has a spatial relationship with a near-vertical zone of increased seismic reflectivity ???15km SW of the SAF and likely represents a deep-reaching fault zone. ?? 2008 The Authors Journal compilation ?? 2008 RAS.

Badenian planktonic foraminifera as climate proxies at the southern margin of the Central Paratethys (Ugljevik, Bosnia and Herzegovina)

NASA Astrophysics Data System (ADS)

Theobalt, D.; Mandic, O.

2012-04-01

Badenian transgression is well exposed in the open coal pit Bogutovo Selo near Ugljevik in NE Bosnia and Herzegovina, located at the southern margin of the Pannonian Basin. Middle Miocene marine sediments superpose Late Oligocene lignite bearing lacustrine deposits. The studied succession is about 62 m thick and includes the uppermost part of the lake deposits, comprising clays, sands and coal seams, followed by marine sediments. These consist mainly of gray marls, which show some intercalations of thin, dark clay layers, volcanic ash layers and fossiliferous beds as well as carbonate bodies of different thicknesses. The presence of Orbulina suturalis allows a biostratigraphic correlation of the marine transgression horizon with the upper part of the Lower Badenian. 28 planktonic foraminiferal assemblages were investigated using quantitative analysis to evaluate the climate development during the initial marine flooding by the Paratethys Sea. Further on the samples were statistically treated to find out if there are significant differences in assemblages from the marine sediments deposited before and after the initial Serravallian cooling event coinciding with the onset of the Middle Badenian (Wielician) Salinity Crisis. 17 planktonic foraminiferal species were grouped by their palaeoclimatic significance into cool (Globigerina bulloides, G. praebulloides, G. diplostoma, G. concinna, G. tarchanensis, G. falconensis, Turborotalita quinqueloba), temperate (Globorotalia bykovae, G. transsylvanica, G. peripheroronda, Globoturborotalita woodi), warm-temperate (Globigerinella regularis, Tenuitellinata angustiumbilicata) and warm indicators (Globigerinoides trilobus, G. quadrilobatus, Orbulina suturalis, Globoquadrina cf. altispira). The counts were performed mainly on generic level. Upper Lower Badenian (Upper Lagenidae Zone) is represented in the marly succession in the lower part of the section, where the foraminiferal assemblages indicate warmer conditions with high percentages of warm water indicators. A distinct cooling is shown in the uppermost passage of the lower part, which is followed by a 13 m thick carbonate platform of Wielician age. This transition corresponds to the gradual shift from Greenhouse into Icehouse climate after the late Middle Miocene Climatic Optimum. The superposing marly deposits of the late Wielician age (Earliest Serravallian) contain planktonic foraminiferal assemblages that indicate cooler conditions. The general percentage of cool water indicators is much higher than in the lower Badenian sediments.

Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2007

USGS Publications Warehouse

Ortiz, A.G.

2008-01-01

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2007. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 39.50 inches for west-central Florida (from October 2006 through September 2007) was 13.42 inches below the historical cumulative average of 52.92 inches (Southwest Florida Water Management District, 2007). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period September 17-21, 2007. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2008). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal high water-level condition.

Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2008

USGS Publications Warehouse

Ortiz, Anita G.

2009-01-01

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2008. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 50.63 inches for west-central Florida (from October 2007 through September 2008) was 2.26 inches below the historical cumulative average of 52.89 inches (Southwest Florida Water Management District, 2008). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period September 15-19, 2008. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2009). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal high water-level condition.

Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2008

USGS Publications Warehouse

Ortiz, A.G.

2008-01-01

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2008. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 46.95 inches for west-central Florida (from June 2007 through May 2008) was 5.83 inches below the historical cumulative average of 52.78 inches (Southwest Florida Water Management District, 2008). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 19-23, 2008. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2008). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2007

USGS Publications Warehouse

Ortiz, A.G.

2008-01-01

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2007. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 41.21 inches for west-central Florida (from June 2006 through May 2007) was 11.63 inches below the historical cumulative average of 52.84 inches (Southwest Florida Water Management District, 2007). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 21-25, 2007. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2007). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

Variation in the diel vertical distributions of larvae and transforming stages of oceanic fishes across the tropical and equatorial Atlantic

NASA Astrophysics Data System (ADS)

Olivar, M. Pilar; Contreras, Tabit; Hulley, P. Alexander; Emelianov, Mikhail; López-Pérez, Cristina; Tuset, Víctor; Castellón, Arturo

2018-01-01

The vertical distributions of early developmental stages of oceanic fishes were investigated across the tropical and equatorial Atlantic, from oligotrophic waters close to the Brazilian coast to more productive waters close to the Mauritanian Upwelling Region. Stratification of the water column was observed throughout the study region. Fishes were caught with a MOCNESS-1 net with mouth area of 1 m2 at 11 stations. Each station was sampled both during the day and at night within a single 24-h period. The investigation covered both larvae and transforming stages from the surface to 800 m depth. Distribution patterns were analysed, and weighted mean depths for the larvae and transforming stages of each species were calculated for day and night conditions. Forty-seven different species were found. The highest number of species occurred in the three stations south of Cape Verde Islands, characterized by a mixture of South Atlantic Central Water (SACW) and Eastern North Atlantic Central Water (ENACW). There was a marked drop in species richness in the three stations closer to the African upwelling, dominated by ENACW. The highest abundances occurred in the families Myctophidae, Sternoptychidae, Gonostomatidae and Phosichthyidae. Day and night vertical distributions of larvae and transforming stages showed contrasting patterns, both in the depths of the main concentration layers in the water column, and in the diel migration patterns (where these were observed). Larvae generally showed a preference for the upper mixed layer (ca. 0-50 m) and upper thermocline (ca. 50-100 m), except for sternoptychids, which were also abundant in the lower thermocline layer (100-200 m) and even extended into the mesopelagic zone (down to 500 m). Transforming stages showed a more widespread distribution, with main concentrations in the mesopelagic zone (200-800 m). Larvae showed peak concentrations in the more illuminated and zooplankton-rich upper mixed layers during the day and a wider distribution through the upper 100 m during the night. For most species, transforming stages were concentrated in the mesopelagic layers both day and night, although in some species (Diaphus cf. vanhoeffeni and Vinciguerria nimbaria), the transforming stages displayed vertical migration into the upper 100 m at night, in a manner similar to their adult stages.

Metamorphic and tectonic evolution of Ceuta peninsula (Internal Rif): new interpretation in the framework of arc and back arc evolution

NASA Astrophysics Data System (ADS)

Homonnay, Emmanuelle; Lardeaux, Jean-Marc; Corsini, Michel; Cenki-Tok, Bénédicte; Bosch, Delphine; Munch, Philippe; Romagny, Adrien; Ouazzani-Touhami, Mohamed

2016-04-01

In the last twenty years, various geophysical investigations have established that the Western Mediterranean opened in a subduction context as a back arc domain. In the Alboran basin the dip of the subduction plane is eastwards or southeastwards depending of considered models. If the geological records of back-arc opening are well-known, the arc-related tectonic and petrologic evolutions are still poorly documented. In order to decipher these markers, we focalised structural, petrological and thermo-chronological studies on the Ceuta peninsula located in the Rif belt, on the western part of the Gibraltar arc to the North of Morocco. The present-day tectonic pile is constituted by: (1) the upper Ceuta unit, composed of High Pressure and High Temperature metapelites retromorphosed under Amphibolite-facies condition, with Ultra-High Pressure relicts, and pyrigarnite and spinel bearing peridotites boudins at its base, (2) the lower Monte Hacho unit, with orthogneisses metamorphosed under Amphibolite-facies conditions. Structural analysis indicates a polyphase tectonic evolution: (1) an earlier deformation phase only observed in the UHP metapelites and characterized by a steep S1 foliation plane, (2) a main deformation phase associated to a pervasive gently dipping S2 foliation plane bearing a L2 stretching lineation and synschistose folds whose axes are parallel to L2 and (3) a late deformation phase which developed S3 foliation plane and L3 stretching lineation coeval with development of narrow normal ductile shear zones. A zone of increasing deformation, several dozen meters wide, is identified as a major ductile shear zone involving the peridotitic lenses at the base of the metapelites of the Ceuta unit and overlaying this upper unit on top of the orthogneisses of the Monte Hacho lower unit. The attitude of mylonitic foliation and stretching and mineral lineations as well as the numerous shear sense indicators observed in the shear zone are consistent with a thrusting toward the NE. Furthermore, biotite-sillimanite bearing S2 foliation affecting the whole of crustal rocks is contemporaneous with the movement on this main ductile thrusting. We combined garnet-biotite and GASP thermo-barometers with thermodynamic modelling (Theriak-Domino) in order to constrain pressure and temperature conditions of D2 and D3 tectono-metamorphic events. P-T conditions of D2 deformation are in the range 7-10kbar and 770-820°C and are compatible with syn-tectonic partial melting. D3 deformation event occurred at 1-7kbar and 400-550°C. These metamorphic conditions reflect abnormally high geothermal gradients during both shortening and thinning and are clearly compatible with the thermal evolution recognized in continental arcs. Preliminary U-Th-Pb (monazite, zircon and xenotime) and previous Ar39/Ar40 (micas) analyses, furnished similar ages around 21 Ma for D2 and D3 events, suggesting a very fast transition from arc to back-arc dynamics.

Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2006

USGS Publications Warehouse

Ortiz, A.G.

2007-01-01

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2006. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 46.06 inches for west-central Florida (from October 2005 through September 2006) was 6.91 inches below the historical cumulative average of 52.97 inches (Southwest Florida Water Management District, 2006). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during September 18-22, 2006. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman, 2007). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal high water-level condition.

Potentiometric surface of the Upper Floridan aquifer, west-central Florida, September 2005

USGS Publications Warehouse

Ortiz, A.G.

2006-01-01

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public-supply, domestic use, irrigation, and brackish-water desalination in coastal communities (Southwest Florida Water Management District, 2000).This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2005. The potentiometric surface is an imaginary surface, connecting points of equal altitude to which water will rise in tightly cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 55.19 inches for west-central Florida (from October 2004 through September 2005) was 2.00 inches above the historical cumulative average of 53.19 inches (Southwest Florida Water Management District, 2005). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District.This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period September 19-23, 2005. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Altamonte Springs, Florida (Kinnaman, 2006). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a "snapshot" of conditions at a specific time, nor do they necessarily coincide with the seasonal high water-level condition.

Hydrogen-bearing iron peroxide and the origin of ultralow-velocity zones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jin; Hu, Qingyang; Young Kim, Duck

Ultralow-velocity zones (ULVZs) at Earth’s core–mantle boundary region have important implications for the chemical composition and thermal structure of our planet, but their origin has long been debated1,2,3. Hydrogen-bearing iron peroxide (FeO2Hx) in the pyrite-type crystal structure was recently found to be stable under the conditions of the lowermost mantle4,5,6. Using high-pressure experiments and theoretical calculations, we find that iron peroxide with a varying amount of hydrogen has a high density and high Poisson ratio as well as extremely low sound velocities consistent with ULVZs. Here we also report a reaction between iron and water at 86 gigapascals and 2,200more » kelvin that produces FeO2Hx. This would provide a mechanism for generating the observed volume occupied by ULVZs through the reaction of about one-tenth the mass of Earth’s ocean water in subducted hydrous minerals with the effectively unlimited reservoir of iron in Earth’s core. Unlike other candidates for the composition of ULVZs7,8,9,10,11,12, FeO2Hx synthesized from the superoxidation of iron by water would not require an extra transportation mechanism to migrate to the core–mantle boundary. These dense FeO2Hx-rich domains would be expected to form directly in the core–mantle boundary region and their properties would provide an explanation for the many enigmatic seismic features that are observed in ULVZs.« less

Taxonomic and compositional differences of ground-dwelling arthropods in riparian habitats in Glen Canyon, Arizona, USA

USGS Publications Warehouse

Ralston, Barbara; Cobb, Neil S.; Brantley, Sandra L.; Higgins, Jacob; Yackulic, Charles B.

2017-01-01

The disturbance history, plant species composition, productivity, and structural complexity of a site can exert bottom-up controls on arthropod diversity, abundance, and trophic structure. Regulation alters the hydrology and disturbance regimes of rivers and affects riparian habitats by changing plant quality parameters. Fifty years of regulation along the Colorado River downstream of Glen Canyon Dam has created a no-analog, postdam “lower” riparian zone close to the water's edge that includes tamarisk (Tamarix sp.), a nonnative riparian shrub. At the same time, the predam “upper” facultative riparian zone has persisted several meters above the current flood stage. In summer 2009, we used pitfall traps within these 2 riparian zones that differ in plant composition, productivity, and disturbance frequency to test for differences in arthropod community (Hymenoptera, Arachnida, and Coleoptera) structure. Arthropod community structure differed substantially between the 2 zones. Arthropod abundance and species richness was highest in the predam upper riparian zone, even though there was a greater amount of standing plant biomass in the postdam lower riparian zone. Omnivore abundance was proportionately greater in the upper riparian zone and was associated with lower estimated productivity values. Predators and detritivores were proportionately greater in the postdam lower riparian zone. In this case, river regulation may create habitats that support species of spiders and carabid beetles, but few other species that are exclusive to this zone. The combined richness found in both zones suggests a small increase in total richness and functional diversity for the Glen Canyon reach of the Colorado River.

Hydrogeologic framework of the middle San Pedro watershed, southeastern Arizona

USGS Publications Warehouse

Dickinson, Jesse; Kennedy, Jeffrey R.; Pool, D.R.; Cordova, Jeffrey T.; Parker, John T.; Macy, J.P.; Thomas, Blakemore

2010-01-01

Water managers in rural Arizona are under increasing pressure to provide sustainable supplies of water despite rapid population growth and demands for environmental protection. This report describes the results of a study of the hydrogeologic framework of the middle San Pedro watershed. The components of this report include: (1) a description of the geologic setting and depositional history of basin fill sediments that form the primary aquifer system, (2) updated bedrock altitudes underlying basin fill sediments calculated using a subsurface density model of gravity data, (3) delineation of hydrogeologic units in the basin fill using lithologic descriptions in driller's logs and models of airborne electrical resistivity data, (4) a digital three-dimensional (3D) hydrogeologic framework model (HFM) that represents spatial extents and thicknesses of the hydrogeologic units (HGUs), and (5) description of the hydrologic properties of the HGUs. The lithologic interpretations based on geophysical data and unit thickness and extent of the HGUs included in the HFM define potential configurations of hydraulic zones and parameters that can be incorporated in groundwater-flow models. The hydrogeologic framework comprises permeable and impermeable stratigraphic units: (1) bedrock, (2) sedimentary rocks predating basin-and-range deformation, (3) lower basin fill, (4) upper basin fill, and (5) stream alluvium. The bedrock unit includes Proterozoic to Cretaceous crystalline rocks, sedimentary rocks, and limestone that are relatively impermeable and poor aquifers, except for saturated portions of limestone. The pre-basin-and-range sediments underlie the lower basin fill but are relatively impermeable owing to cementation. However, they may be an important water-bearing unit where fractured. Alluvium of the lower basin fill, the main water-bearing unit, was deposited in the structural trough between the uplifted ridges of bedrock and (or) pre-basin-and-range sediments. Alluvium of the upper basin fill may be more permeable than the lower basin fill, but it is generally unsaturated in the study area. The lower basin fill stratigraphic unit was delineated into three HGUs on the basis of lithologic descriptions in driller?s logs and one-dimensional (1D) electrical models of airborne transient electromagnetic (TEM) surveys. The interbedded lower basin fill (ILBF) HGU represents an upper sequence having resistivity values between 5 and 40 ohm-m identified as interbedded sand, gravel, and clay in driller?s logs. Below this upper sequence, fine-grained lower basin fill (FLBF) HGU represents a thick silt and clay sequence having resistivity values between 5 and 20 ohm-m. Within the coarse-grained lower basin fill (CLBF) HGU, which underlies the silt and clay of the FLBF, the resistivity values on logs and 1D models increase to several hundred ohm-m and are highly variable within sand and gravel layers. These sequences match distinct resistivity and lithologic layers identified by geophysical logs in the adjacent Sierra Vista subwatershed, suggesting that these sequences are laterally continuous within both the Benson and Sierra Vista subwatersheds in the Upper San Pedro Basin. A subsurface density model based on gravity data was constructed to identify the top of bedrock and structures that may affect regional groundwater flow. The subsurface density model contains six layers having uniform density values, which are assigned on the basis of geophysical logs. The density values for the layers range between 1.65 g/cm3 for unsaturated sediments near the land surface and 2.67 g/cm3 for bedrock. Major features include three subbasins within the study area, the Huachuca City subbasin, the Tombstone subbasin, and the Benson subbasin, which have no expression in surface topography or lithology. Bedrock altitudes from the subsurface density model defined top altitudes of the bedrock HGU. The HFM includes the following HGUs in ascending stratigr

Single crystal neutron diffraction of hydrous wadsleyite and the reason of sensitivity difference for hydration between upper and lower mantle transition zones

NASA Astrophysics Data System (ADS)

Purevjav, N.; Okuchi, T.; Tomioka, N.; Wang, X.; Hoffmann, C.

2016-12-01

Evidences from seismological and mineralogical studies increasingly indicates that water has been transported from the oceans into the Earth's deep mantle, where the mantle transition zone is believed to be the largest reservoir of this transported water. Wadsleyite and ringwoodite are the major constituents and the most important host minerals absorbing this type of water in the transition zone. These minerals are capable of storing the entire mass of the oceans as a hidden reservoirs. In order to understand the effects of such water on the physical properties and chemical evolution of the Earth's interior, it is essential to determine where in the crystal structure the hydration occurs, and which chemical bonds are altered and weakened after hydration. Here we show the result of a neutron single-crystal Laue diffraction study of hydrous wadsleyite. A crystal of homogenously-hydrated wadsleyite involving 1.4 wt. % of H2O was synthesized by our recently-established slow cooling method, which was an effective way to grow high quality large single crystals [1]. By analyzing this crystal using pulsed neutron beam, we demonstrated that the hydrogen atoms exchange only with Mg2+ at the one of the specific octahedron sites (M3) in wadsleyite. We also determined hydrogen's bonding distances and bonding angle. The results unambiguously demonstrated the unique mechanism of hydrogen incorporation into the wadsleyite crystal structure. We previously found that the hydrogen atoms exchanged with both Mg2+ and Si4+ sites simultaneously in the crystal structure of hydrous ringwoodite [2]. Therefore, the current results show that hydration mechanisms are qualitatively different between the upper and the lower transition zones in the wet mantle. The difference is a vital clue towards understanding why these mantle transition zone minerals show different sensitivity for water in their softening behaviors. In addition, we demonstrated that maximum water concentration in wadsleyite is strictly constrained by its full capacity into M3 site. Also, by this study we demonstrated that single-crystal neutron diffraction is a useful tool for quantitative analysis of H2O concentrations in nominally anhydrous minerals. [1] Okuchi et al., Amer. Miner., 2015; [2] Purevjav et al., Geophys. Res. Lett., 2014.

Hydrogeology and water quality of the Floridan aquifer system and effects of Lower Floridan aquifer pumping on the Upper Floridan aquifer at Fort Stewart, Georgia

USGS Publications Warehouse

Clarke, John S.; Cherry, Gregory C.; Gonthier, Gerard

2011-01-01

Test drilling, field investigations, and digital modeling were completed at Fort Stewart, GA, during 2009?2010, to assess the geologic, hydraulic, and water-quality characteristics of the Floridan aquifer system and evaluate the effect of Lower Floridan aquifer (LFA) pumping on the Upper Floridan aquifer (UFA). This work was performed pursuant to the Georgia Environmental Protection Division interim permitting strategy for new wells completed in the LFA that requires simulation to (1) quantify pumping-induced aquifer leakage from the UFA to LFA, and (2) identify the equivalent rate of UFA pumping that would produce the same maximum drawdown in the UFA that anticipated pumping from LFA well would induce. Field investigation activities included (1) constructing a 1,300-foot (ft) test boring and well completed in the LFA (well 33P028), (2) constructing an observation well in the UFA (well 33P029), (3) collecting drill cuttings and borehole geophysical logs, (4) collecting core samples for analysis of vertical hydraulic conductivity and porosity, (5) conducting flowmeter and packer tests in the open borehole within the UFA and LFA, (6) collecting depth-integrated water samples to assess basic ionic chemistry of various water-bearing zones, and (7) conducting aquifer tests in new LFA and UFA wells to determine hydraulic properties and assess interaquifer leakage. Using data collected at the site and in nearby areas, model simulation was used to assess the effects of LFA pumping on the UFA. Borehole-geophysical and flowmeter data indicate the LFA at Fort Stewart consists of limestone and dolomitic limestone between depths of 912 and 1,250 ft. Flowmeter data indicate the presence of three permeable zones at depth intervals of 912-947, 1,090-1,139, and 1,211?1,250 ft. LFA well 33P028 received 50 percent of the pumped volume from the uppermost permeable zone, and about 18 and 32 percent of the pumped volume from the middle and lowest permeable zones, respectively. Chemical constituent concentrations increased with depth, and water from all permeable zones contained sulfate at concentrations that exceeded the U.S. Environmental Protection Agency secondary maximum contaminant level of 250 milligrams per liter. A 72-hour aquifer test pumped LFA well 33P028 at 740 gallons per minute (gal/min), producing about 39 ft of drawdown in the pumped well and about 0.4 foot in nearby UFA well 33P029. Simulation using the U.S. Geological Survey finite-difference code MODFLOW was used to determine long-term, steady-state flow in the Floridan aquifer system, assuming the LFA well was pumped continuously at a rate of 740 gal/min. Simulated steady-state drawdown in the LFA was identical to that observed in pumped LFA well 33P028 at the end of the 72-hour test, with values larger than 1 ft extending 4.4 square miles symmetrically around the pumped well. Simulated steady-state drawdown in the UFA resulting from pumping in LFA well 33P028 exceeded 1 ft within a 1.4-square-mile circular area, and maximum drawdown in the UFA was 1.1 ft. Leakage from the UFA through the Lower Floridan confining unit contributed about 98 percent of the water to the well; lateral flow from specified-head model boundaries contributed about 2 percent. About 80 percent of the water supplied to LFA well 33P028 originated from within 1 mile of the well, and 49 percent was derived from within 0.5 mile of the well. Vertical hydraulic gradients and vertical leakage are progressively higher near the LFA pumped well which results in a correspondingly higher contribution of water from the UFA to the pumped well at distances closer to the pumped well. Simulated pumping-induced interaquifer leakage from the UFA to the LFA totaled 725 gal/min (1.04 million gallons per day), whereas simulated pumping at 205 gal/min (0.3 million gallons per day) from UFA well 33P029 produced the equivalent maximum drawdown as pumping LFA well 33P028 at 740 gal/min during the aquifer test. This equivalent pumpin

Quantification of BMPs Selection and Spatial Placement Impact on Water Quality Controlling Plans in Lower Bear River Watershed, Utah

NASA Astrophysics Data System (ADS)

Salha, A. A.; Stevens, D. K.

2016-12-01

The aim of the watershed-management program in Box Elder County, Utah set by Utah Division of Water Quality (UDEQ) is to evaluate the effectiveness and spatial placement of the implemented best-management practices (BMP) for controlling nonpoint-source contamination at watershed scale. The need to evaluate the performance of BMPs would help future policy and program decisions making as desired end results. The environmental and costs benefits of BMPs in Lower Bear River watershed have seldom been measured beyond field experiments. Yet, implemented practices have rarely been evaluated at the watershed scale where the combined effects of variable soils, climatic conditions, topography and land use/covers and management conditions may significantly change anticipated results and reductions loads. Such evaluation requires distributed watershed models that are necessary for quantifying and reproducing the movement of water, sediments and nutrients. Soil and Water Assessment Tool (SWAT) model is selected as a watershed level tool to identify contaminant nonpoint sources (critical zones) and areas of high pollution risks. Water quality concerns have been documented and are primarily attributed to high phosphorus and total suspended sediment concentrations caused by agricultural and farming practices (required load is 460 kg/day of total phosphorus based on 0.075 mg/l and an average of total suspended solids of 90 mg/l). Input data such as digital elevation model (DEM), land use/Land cover (LULC), soils, and climate data for 10 years (2000-2010) is utilized along with observed water quality at the watershed outlet (USGS) and some discrete monitoring points within the watershed. Statistical and spatial analysis of scenarios of management practices (BMP's) are not implemented (before implementation), during implementation, and after BMP's have been studied to determine whether water quality of the two main water bodies has improved as required by the LBMR watershed's TMDL and if the BMPs are cost-effectively targeting the critical zones.

Challenges of using electrical resistivity method to locate karst conduits-A field case in the Inner Bluegrass Region, Kentucky

USGS Publications Warehouse

Zhu, J.; Currens, J.C.; Dinger, J.S.

2011-01-01

Conduits serve as major pathways for groundwater flow in karst aquifers. Locating them from the surface, however, is one of the most challenging tasks in karst research. Geophysical methods are often deployed to help locate voids by mapping variations of physical properties of the subsurface. Conduits can cause significant contrasts of some physical properties that can be detected; other subsurface features such as water-bearing fractures often yield similar contrasts, which are difficult to distinguish from the effects of the conduits. This study used electrical resistivity method to search for an unmapped karst conduit that recharges Royal Spring in the Inner Bluegrass karst region, Kentucky, USA. Three types of resistivity techniques (surface 2D survey, quasi-3D survey, and time-lapse survey) were used to map and characterize resistivity anomalies. Some of the major anomalies were selected as drilling targets to verify the existence of the conduits. Drilling near an anomaly identified by an electrical resistivity profile resulted in successful penetration of a major water-filled conduit. The drilling results also suggest that, in this study area, low resistivity anomalies in general are associated with water-bearing features. However, differences in the anomaly signals between the water-filled conduit and other water-bearing features such as water-filled fracture zones were undistinguishable. The electrical resistivity method is useful in conduit detection by providing potential drilling targets. Knowledge of geology and hydrogeology about the site and professional judgment also played important roles in locating the major conduit. ?? 2011 Elsevier B.V.

An Integrated Watershed and Receiving Water Model for Fecal Coliform Fate and Transport in Sinclair and Dyes Inlets, Puget Sound, WA

DTIC Science & Technology

2009-12-01

xix USLE Universal Soil Loss Equation UV Ultraviolet UZSN Upper Zone Nominal Storage WA-DOE Washington State Department of Ecology WA-DOH...Effective Impervious Area IMPLND Impervious Land Cover INFILT Interflow Inflow Parameter (related to infiltration capacity of the soil ) INSUR...within Watershed (#/Km) SCCWRP Southern California Coastal Water Research Project SCS Soil Conservation Service SGA Shellfish Growing Area SPAWAR

Two-axis tracker for solar panels and the like

DOEpatents

Liao, Henry H.

2013-04-16

A tracker including an outer post having elongated bore and a lower end mounted on a sub-structure, an inner pole rotatably received in the elongated bore, a lower bearing in the bore adjacent a lower end of the outer post and attached thereto to be constrained from lateral movement and mounted on the sub-structure such that a lower end of the inner pole rests on and is supported by the lower bearing, an upper bearing near an upper end of the outer post, a circumferential drive supported on the outer post for rotating the inner pole relative to the outer post, such that substantially a full weight of a load on the inner pole is directly transmitted to the sub-structure and lateral force and torque leverage are placed on a full length of the outer post by way of the upper and lower bearing.

Arsenic migration to deep groundwater in Bangladesh influenced by adsorption and water demand

NASA Astrophysics Data System (ADS)

Radloff, K. A.; Zheng, Y.; Michael, H. A.; Stute, M.; Bostick, B. C.; Mihajlov, I.; Bounds, M.; Huq, M. R.; Choudhury, I.; Rahman, M. W.; Schlosser, P.; Ahmed, K. M.; van Geen, A.

2011-11-01

The consumption of shallow groundwater with elevated concentrations of arsenic is causing widespread disease in many parts of South and Southeast Asia. In the Bengal Basin, a growing reliance on groundwater sourced below 150-m depth--where arsenic concentrations tend to be lower--has reduced exposure. Groundwater flow simulations have suggested that these deep waters are at risk of contamination due to replenishment with high-arsenic groundwater from above, even when deep water pumping is restricted to domestic use. However, these simulations have neglected the influence of sediment adsorption on arsenic migration. Here, we inject arsenic-bearing groundwater into a deep aquifer zone in Bangladesh, and monitor the reduction in arsenic levels over time following stepwise withdrawal of the water. Arsenic concentrations in the injected water declined by 70% after 24h in the deep aquifer zone, owing to adsorption on sediments; concentrations of a co-injected inert tracer remain unchanged. We incorporate the experimentally determined adsorption properties of sands in the deep aquifer zone into a groundwater flow and transport model covering the Bengal Basin. Simulations using present and future scenarios of water-use suggest that arsenic adsorption significantly retards transport, thereby extending the area over which deep groundwater can be used with low risk of arsenic contamination. Risks are considerably lower when deep water is pumped for domestic use alone. Some areas remain vulnerable to arsenic intrusion, however, and we suggest that these be prioritized for monitoring.

Early Permian transgressive-regressive cycles: Sequence stratigraphic reappraisal of the coal-bearing Barakar Formation, Raniganj Basin, India

NASA Astrophysics Data System (ADS)

Bhattacharya, Biplab; Bhattacharjee, Joyeeta; Bandyopadhyay, Sandip; Banerjee, Sudipto; Adhikari, Kalyan

2018-03-01

The present research is an attempt to assess the Barakar Formation of the Raniganj Gondwana Basin, India, in the frame of fluvio-marine (estuarine) depositional systems using sequence stratigraphic elements. Analysis of predominant facies associations signify deposition in three sub-environments: (i) a river-dominated bay-head delta zone in the inner estuary, with transition from braided fluvial channels (FA-B1) to tide-affected meandering fluvial channels and flood plains (FA-B2) in the basal part of the succession; (ii) a mixed energy central basin zone, which consists of transitional fluvio-tidal channels (FA-B2), tidal flats, associated with tidal channels and bars (FA-B3) in the middle-upper part of the succession; and (iii) a wave-dominated outer estuary (coastal) zone (FA-B4 with FA-B3) in the upper part of the succession. Stacked progradational (P1, P2)-retrogradational (R1, R2) successions attest to one major base level fluctuation, leading to distinct transgressive-regressive (T-R) cycles with development of initial falling stage systems tract (FSST), followed by lowstand systems tract (LST) and successive transgressive systems tracts (TST-1 and TST-2). Shift in the depositional regime from regressive to transgressive estuarine system in the early Permian Barakar Formation is attributed to change in accommodation space caused by mutual interactions of (i) base level fluctuations in response to climatic amelioration and (ii) basinal tectonisms (exhumation/sagging) related to post-glacial isostatic adjustments in the riftogenic Gondwana basins.

A regional classification scheme for estimating reference water quality in streams using land-use-adjusted spatial regression-tree analysis

USGS Publications Warehouse

Robertson, Dale M.; Saad, D.A.; Heisey, D.M.

2006-01-01

Various approaches are used to subdivide large areas into regions containing streams that have similar reference or background water quality and that respond similarly to different factors. For many applications, such as establishing reference conditions, it is preferable to use physical characteristics that are not affected by human activities to delineate these regions. However, most approaches, such as ecoregion classifications, rely on land use to delineate regions or have difficulties compensating for the effects of land use. Land use not only directly affects water quality, but it is often correlated with the factors used to define the regions. In this article, we describe modifications to SPARTA (spatial regression-tree analysis), a relatively new approach applied to water-quality and environmental characteristic data to delineate zones with similar factors affecting water quality. In this modified approach, land-use-adjusted (residualized) water quality and environmental characteristics are computed for each site. Regression-tree analysis is applied to the residualized data to determine the most statistically important environmental characteristics describing the distribution of a specific water-quality constituent. Geographic information for small basins throughout the study area is then used to subdivide the area into relatively homogeneous environmental water-quality zones. For each zone, commonly used approaches are subsequently used to define its reference water quality and how its water quality responds to changes in land use. SPARTA is used to delineate zones of similar reference concentrations of total phosphorus and suspended sediment throughout the upper Midwestern part of the United States. ?? 2006 Springer Science+Business Media, Inc.

Non-seagrass meadow sedimentary facies of the Pontinian Islands, Tyrrhenian Sea: A modern example of mixed carbonate siliciclastic sedimentation

NASA Astrophysics Data System (ADS)

Brandano, Marco; Civitelli, Giacomo

2007-10-01

The soft bottom of the Mediterranean continental shelf is characterized by a heterozoan skeletal assemblage ( sensu [James, N.P., 1997. The cool-water carbonate depositional realm. In: James, N.P., Clarke, J. (Eds), Cool-water Carbonates. Spec. Publ. Soc. Sediment. Geol., vol. 56, pp.1-20.]). Although the contemporary presence of terrigenous and skeletal carbonate sediments has been well established [Tortora, P., 1996. Depositional and erosional coastal processes during the last postglacial sea-level rise: an example from the Central Tyrrhenian continental shelf (Italy). J. Sed. Res. 66, 391-405.; Fornós, J.J., Ahr, W.M., 1997. Temperate carbonates on a modern, low-energy, isolated ramp: the Balearic Platform, Spain. Journal of Sedimentary Research , 67, 364-373.; Fornós, J.J., Ahr, W.M., 2006. Present-day temperate carbonate sedimentation on the Balearic Platform, western Mediterranean: compositional and textural variation along a low-energy isolated ramp. In: Pedley, H.M., Carannante, G. (Eds.) 2006, Cool-water Carbonates: Depositional Systems and Palaeoenvironmental Controls. Geological Society, London, Special Publications, 255, pp. 121-135], the interactions between carbonate and terrigenous-siliciclastic sedimentation has not been documented well enough. A total of 33 surface sediment samples from the Pontinian shelf (Tyrrhenian Sea, central Mediterranean) have been analysed. Sampling stations range from 15 to 250 mwd (meter water depth) and are located along five transects (PonzaW, PonzaNW, Ponza NE, Ponza E, Zannone), plus four samples collected around Palmarola Island. Sectors colonized by seagrass meadows have not been sampled. A total of 6 sedimentary facies (F) and 10 microfacies (mf) have been recognized by using component analyses, grain size percentage, sorting, carbonate content and authigenic mineralization rate. These facies and microfacies represent the Pontian Islands shelf sedimentation, in the interval between the upper infralittoral and the epibathyal zones that represent shelf-break and upper slope sedimentation. The Maerl facies (F4a,b; mf4a,b) and the skeletal sands (F2a,b; mf2a1, mf2a2, mf2b) fall within the circalittoral zone. The circalittoral zone in the water depth interval between 82 m and 112 m display relict facies (F6, mf6). Finally facies F5 (Siliciclastic sands) includes subfacies F5b (mf5b), located in the circalittoral zone at depths of 49 to 101 mwd and restricted to the western and eastern sectors of Ponza, and subfacies F5a in the upper infralittoral zone (15 mwd/25 mwd) where erosional processes prevail. Carbonate content analyses indicate that maximum carbonate production on the Pontinian shelf took place in the 60-80 mwd interval. Facies F4 (Maerl) represents the environment characterized by the highest carbonate production rates. In the Pontian area siliciclastic-carbonate mixing took place in the infralittoral zone and in the lower circalittoral zone. In the infralittoral zone erosional processes on the rocky shoreline produced lithoclasts and vulcanoclastic deposits that were reworked by wave-induced near-shore currents. In the lower circalittoral zone the prolific production by photic biota (red algae) ends, while skeletal remains of the aphotic environment mixes with planktonic sediments characterized by low carbonate values. Sand (63 μm-2 mm) is the dominant grain size class, however gravel-dominated facies (F4 Maerl) are present in water depths (50 to 112 mwd) which are significantly below the storm wave base. Glauconite mineralization appears on the Pontinian shelf from 50 mwd and increases in abundance along the deeper bathymetries. The compositional characteristics of relict facies F6 shows the concurrence of biota assemblages of the infralittoral and circalittoral zones, likely representing the record of the last Holocene transgressive event (18 ky) and expressed by the overlapping of components of different environments.

Evaluation of the Field Water-bearing Potential Using Geophysical Methods

NASA Astrophysics Data System (ADS)

Avxhiu, R. B.; Nenaj, S. S.

2002-12-01

There are about 16 villages and the center of the district itself, Bilishti, in the Devolli field with a developed agricultural economy. The actual demand for drink and irrigation water has been considerably increased. As the existing irrigation system is damaged and outdated, it is necessary to have an evaluation of the water-bearing potential of the Quaternary formations of the Devolli Field. These formations are composed of various layers such as clay, sandy clay, sand, coarse-grained sand and gravels. Electrical soundings in a grid of 500 x 500 m and 250 x 250 m have been carried out in an area of 100 km2 to evaluate the water-bearing-potential. Their location along with the geological map is shown in Fig.1. Their interpretation shows that the Quaternary formations thickness varies from some meters to 150 m at the center of the valley. It is shown in Fig.2. It has been made possible to distinguish different layers of various composition and non-homogeneous thickness composing the Quaternary formations, (Figs.3,4,5) but we have been mostly focused on the water-bearing coarse-grained sands and gravels, of higher thickness and consistency. This may help to plan an effective grid of holes to take out water. The history of the Devolli River beds formation during the Quaternary period is treated in this poster as well. This information has been obtained both from the traces of the river beds (which have often changed) and electrical soundings.(Fig.6) We can conclude that the results of the electrical soundings show that there are some waterbearing layers at different hypsometric levels. Two of them are the most important: (Figs.3.4) 1. The uppermost Upper Quaternary sand-gravel formations. 2. The deeper (but almost of the same composition) layer of the Q1 - Q2 formations. The poster is composed of the explanatory text and six illustrating figures,

Y-12 Groundwater Protection Program Groundwater and Surface Water Sampling and Analysis Plan for Calendar Year 2004

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elvado Environmental LLC for the Environmental Compliance Department ES&H Division, Y-12 National Security Complex Oak Ridge, Tennessee

2003-09-30

This plan provides a description of the groundwater and surface water quality monitoring activities planned for calendar year (CY) 2004 at the U.S. Department of Energy (DOE) Y-12 National Security Complex that will be managed by the Y-12 Groundwater Protection Program (GWPP). Groundwater and surface water monitoring performed by the GWPP during CY 2004 will be in accordance with the following requirements of DOE Order 5400.1: (1) to maintain surveillance of existing and potential groundwater contamination sources; (2) to provide for the early detection of groundwater contamination and determine the quality of groundwater and surface water where contaminants are mostmore » likely to migrate beyond the Oak Ridge Reservation property line; (3) to identify and characterize long-term trends in groundwater quality at Y-12; and (4) to provide data to support decisions concerning the management and protection of groundwater resources. Groundwater and surface water monitoring during CY 2004 will be performed primarily in three hydrogeologic regimes at Y-12: the Bear Creek Hydrogeologic Regime (Bear Creek Regime), the Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime), and the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime). The Bear Creek and East Fork regimes are located in Bear Creek Valley, and the Chestnut Ridge Regime is located south of Y-12 (Figure A.1). Additional surface water monitoring will be performed north of Pine Ridge, along the boundary of the Oak Ridge Reservation (Figure A.1). Modifications to the CY 2004 monitoring program may be necessary during implementation. Changes in programmatic requirements may alter the analytes specified for selected monitoring wells, or wells could be added or removed from the planned monitoring network. All modifications to the monitoring program will be approved by the Y-12 GWPP manager and documented as addenda to this sampling and analysis plan.« less

Y-12 Groundwater Protection Program Groundwater and Surface Water Sampling and Analysis Plan for Calendar Year 2005

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2004-09-30

This plan provides a description of the groundwater and surface water quality monitoring activities planned for calendar year (CY) 2005 at the U.S. Department of Energy (DOE) Y-12 National Security Complex (Y-12) that will be managed by the Y-12 Groundwater Protection Program (GWPP). Groundwater and surface water monitoring performed by the GWPP during CY 2005 will be in accordance with DOE Order 540.1 requirements and the following goals: (1) to maintain surveillance of existing and potential groundwater contamination sources; (2) to provide for the early detection of groundwater contamination and determine the quality of groundwater and surface water where contaminantsmore » are most likely to migrate beyond the Oak Ridge Reservation property line; (3) to identify and characterize long-term trends in groundwater quality at Y-12; and (4) to provide data to support decisions concerning the management and protection of groundwater resources. Groundwater and surface water monitoring during CY 2005 will be performed primarily in three hydrogeologic regimes at Y-12: the Bear Creek Hydrogeologic Regime (Bear Creek Regime), the Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime), and the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime). The Bear Creek and East Fork regimes are located in Bear Creek Valley, and the Chestnut Ridge Regime is located south of Y-12 (Figure A.1). Additional surface water monitoring will be performed north of Pine Ridge, along the boundary of the Oak Ridge Reservation (Figure A.1). Modifications to the CY 2005 monitoring program may be necessary during implementation. Changes in programmatic requirements may alter the analytes specified for selected monitoring wells or may add or remove wells from the planned monitoring network. All modifications to the monitoring program will be approved by the Y-12 GWPP manager and documented as addenda to this sampling and analysis plan.« less

Imaging groundwater infiltration dynamics in the karst vadose zone with long-term ERT monitoring

NASA Astrophysics Data System (ADS)

Watlet, Arnaud; Kaufmann, Olivier; Triantafyllou, Antoine; Poulain, Amaël; Chambers, Jonathan E.; Meldrum, Philip I.; Wilkinson, Paul B.; Hallet, Vincent; Quinif, Yves; Van Ruymbeke, Michel; Van Camp, Michel

2018-03-01

Water infiltration and recharge processes in karst systems are complex and difficult to measure with conventional hydrological methods. In particular, temporarily saturated groundwater reservoirs hosted in the vadose zone can play a buffering role in water infiltration. This results from the pronounced porosity and permeability contrasts created by local karstification processes of carbonate rocks. Analyses of time-lapse 2-D geoelectrical imaging over a period of 3 years at the Rochefort Cave Laboratory (RCL) site in south Belgium highlight variable hydrodynamics in a karst vadose zone. This represents the first long-term and permanently installed electrical resistivity tomography (ERT) monitoring in a karst landscape. The collected data were compared to conventional hydrological measurements (drip discharge monitoring, soil moisture and water conductivity data sets) and a detailed structural analysis of the local geological structures providing a thorough understanding of the groundwater infiltration. Seasonal changes affect all the imaged areas leading to increases in resistivity in spring and summer attributed to enhanced evapotranspiration, whereas winter is characterised by a general decrease in resistivity associated with a groundwater recharge of the vadose zone. Three types of hydrological dynamics, corresponding to areas with distinct lithological and structural features, could be identified via changes in resistivity: (D1) upper conductive layers, associated with clay-rich soil and epikarst, showing the highest variability related to weather conditions; (D2) deeper and more resistive limestone areas, characterised by variable degrees of porosity and clay contents, hence showing more diffuse seasonal variations; and (D3) a conductive fractured zone associated with damped seasonal dynamics, while showing a great variability similar to that of the upper layers in response to rainfall events. This study provides detailed images of the sources of drip discharge spots traditionally monitored in caves and aims to support modelling approaches of karst hydrological processes.

Water movement through thick unsaturated zones overlying the central High Plains aquifer, southwestern Kansas, 2000-2001

USGS Publications Warehouse

McMahon, Peter B.; Dennehy, K.F.; Michel, R.L.; Sophocleous, M.A.; Ellett, K.M.; Hurlbut, D.B.

2003-01-01

The role of irrigation as a driving force for water and chemical movement to the central High Plains aquifer is uncertain because of the thick unsaturated zone overlying the aquifer. Water potentials and profiles of tritium, chloride, nitrate, and pesticide concentrations were used to evaluate water movement through thick unsaturated zones overlying the central High Plains aquifer at three sites in southwestern Kansas. One site was located in rangeland and two sites were located in areas dominated by irrigated agriculture. In 2000?2001, the depth to water at the rangeland site was 50 meters and the depth to water at the irrigated sites was about 45.4 meters. Irrigation at the study sites began in 1955?56. Measurements of matric potential and volumetric water content indicate wetter conditions existed in the deep unsaturated zone at the irrigated sites than at the rangeland site. Total water potentials in the unsaturated zone at the irrigated sites systematically decreased with depth to the water table, indicating a potential existed for downward water movement from the unsaturated zone to the water table at those sites. At the rangeland site, total water potentials in the deep unsaturated zone indicate small or no potential existed for downward water movement to the water table. Postbomb tritium was not detected below a depth of 1.9 meters in the unsaturated zone or in ground water at the rangeland site. In contrast, postbomb tritium was detected throughout most of the unsaturated zone and in ground water at both irrigated sites. These results indicate post-1953 water moved deeper in the unsaturated zone at the irrigated sites than at the rangeland site. The depth of the interface between prebomb and postbomb tritium and a tritium mass-balance method were used to estimate water fluxes in the unsaturated zone at each site. The average water fluxes at the rangeland site were 5.4 and 4.4 millimeters per year for the two methods, which are similar to the average water flux (5.1 millimeters per year) estimated using a chloride mass-balance method. Tritium profiles in the unsaturated zone at the irrigated sites were complicated by the presence of tritium-depleted intervals separating upper and lower zones containing postbomb tritium. If the interface between prebomb and postbomb tritium was at the top of the tritium-depleted interval and postbomb tritium detected beneath that interval was from the declining water table in the area, then the average water flux at the irrigated sites was estimated to be 21 to 54 millimeters per year. If postbomb tritium detected beneath the tritium-depleted interval was from bypass or preferential water movement through the local unsaturated zone instead of the declining water table, then the minimum water flux at the irrigated sites was estimated to be 106 to 116 millimeters per year. In either case, water fluxes at the irrigated sites were at least 4 to 12 times larger than the flux at the rangeland site, indicating irrigation was an important driving force for water movement through the unsaturated zone. The presence of postbomb tritium and large nitrate and total pesticide concentrations (24 milligrams per liter as nitrogen and 0.923 microgram per liter, respectively) in ground water at the irrigated sites indicates irrigation water also was an important driving force for chemical movement to the water table. The persistence of a downward hydraulic gradient from the deep unsaturated zone to the water table at the irrigated sites, in addition to large nitrate and atrazine concentrations in deep soil water (34 milligrams per liter as nitrogen and 0.79 microgram per liter, respectively), indicate that the deep unsaturated zone will be a source of nitrate and atrazine to the aquifer in the future.

Behavioral decisions for managing social distance and aggression in captive polar bears (Ursus maritimus).

PubMed

Renner, Michael J; Kelly, Aislinn L

2006-01-01

The polar bear (Ursus maritimus) in most zoos attracts high levels of public attention and can play an important role in conservation education. Polar bears in the wild are typically solitary; bears in captivity often house socially. This study reported behavioral evidence on how bears manage this situation and whether proximity leads to aggression. The study recorded location and behavior once per minute for 106 hr for 2 female polar bears at the Philadelphia Zoo; the samples represented all times of day bears spent in the enclosure (off-exhibit time spent in separate, indoor dens). When changing locations, 1 bear more frequently moved away from the other, effecting a net increase in interindividual distance. When either bear moved into an adjacent zone, 1 typically moved away. The bears occupied the same enclosure zone for a low proportion of time; proximity did not routinely lead to overt aggression. These data indicate polar bears make behavioral decisions, minimizing aggression, to manage social distance and that enclosure designers for solitary species--to facilitate social avoidance--should consider using topographical complexity and multiple pathways throughout.

Hydrogeologic atlas of aquifers in Indiana

USGS Publications Warehouse

Fenelon, Joseph M.; Bobay, K.E.; Greeman, T.K.; Hoover, M.E.; Cohen, D.A.; Fowler, K.K.; Woodfield, M.C.; and Durbin, J. M.

1994-01-01

Aquifers in 12 water-management basins of Indiana are identified in a series of 104 hydrogeologic sections and 12 maps that show the thickness and configuration of aquifers. The vertical distribution of water-bearing units and a generalized potentiometric profile are shown along 3,500 miles of section lines that were constructed from drillers' logs of more than 4,200 wells. The horizontal scale of the sections is 1:125,000. Maps of aquifers showing the areal distribution of each aquifer type were drawn at a scale of 1:500,000. Unconsolidated aquifers are the most widely used aquifers in Indiana and include surficial, buried, and discontinuous layers of sand and gravel. Most of the surficial sand and gravel is in large outwash plains in northern Indiana and along the major rivers. Buried sand and gravel aquifers are interbedded with till deposits in much of the northern two-thirds of Indiana. Discontinuous sand and gravel deposits are present as isolated lenses, primarily in glaciated areas. The bedrock aquifers generally have lower yields than most of the sand and gravel aquifers; however, bedrock aquifers are areally widespread and are an important source of water. Bedrock aquifer types consist of carbonates; sandstones; complexly interbedded sandstones, siltstones, shales, limestones, and coals; and an upper weathered zone in low permeability rock. Carbonate aquifers underlie about one-half of Indiana and are the most productive of the bedrock aquifers. The other principal bedrock aquifer type, sandstone, underlies large areas in the southwestern one-fifth of Indiana. No aquifer is known to be present in the southeastern corner of Indiana.

Geochemistry and diagenesis of Miocene lacustrine siliceous sedimentary and pyroclastic rocks, Mytilinii basin, Samos Island, Greece

USGS Publications Warehouse

Stamatakis, M.G.; Hein, J.R.; Magganas, A.C.

1989-01-01

A Late Miocene non-marine stratigraphic sequence composed of limestone, opal-CT-bearing limestone, porcelanite, marlstone, diatomaceous marlstone, dolomite, and tuffite crops out on eastern Samos Island. This lacustrine sequence is subdivided into the Hora Beds and the underlying Pythagorion Formation. The Hora Beds is overlain by the clastic Mytilinii series which contains Turolian (Late Miocene) mammalian fossils. The lacustrine sequence contains volcanic glass and the silica polymorphs opal-A, opal-CT, and quartz. Volcanic glass predominantly occurs in tuffaceous rocks from the lower and upper parts of the lacustrine sequence. Opal-A (diatom frustules) is confined to layers in the upper part of the Hora Beds. Beds rich in opal-CT underlie those containing opal-A. The occurrence of opal-CT is extensive, encompassing the lower Hora Beds and the sedimentary rocks and tuffs of the Pythagorion Formation. A transition zone between the opal-A and opal-CT zones is identified by X-ray diffraction patterns that are intermediate between those of opal-CT and opal-A, perhaps due to a mixture of the two polymorphs. Diagenesis was not advanced enough for opal-CT to transform to quartz or for volcanic glass to transform to opal-C. Based on geochemical and mineralogical data, we suggest that the rate of diagenetic transformation of opal-A to opal-CT was mainly controlled by the chemistry of pore fluids. Pore fluids were characterized by high salinity, moderately high alkalinity, and high magnesium ion activity. These pore fluid characteristics are indicated by the presence of evaporitic salts (halite, sylvite, niter), high boron content in biogenic silica, and by dolomite in both the opal-A and opal-CT-bearing beds. The absence of authigenic K-feldspar, borosilicates, and zeolites also support these pore fluid characteristics. Additional factors that influenced the rate of silica diagenesis were host rock lithology and the relatively high heat flow in the Aegean region from Miocene to Holocene. ?? 1989.

Brown bear-human interactions associated with deer hunting on Kodiak Island

USGS Publications Warehouse

Barnes, Victor G.

1994-01-01

I compared distribution and range of brown bears (Ursus arctos middendorffi) with temporal and spatial distribution of Sitka black-tailed deer (Odocoileus hemionus sitkensis) hunting activity on westside Kodiak Island, Alaska, to examine impacts of deer hunting on bears. Mean number of bears that annually ranged ≤5 km from the coast, >5 km inland from the coast, or in both areas was 10, 8, and 11, respectively. Bears that exclusively or seasonally occupied the coast zone were usually classed as having moderate or high potential to interact with hunters because most hunter access and effort (>95%) was via the coast. Bears that ranged exclusively inland were considered unlikely to encounter hunters. Animals that ranged in both zones often (39%) moved inland during fall (Oct-Dec) and most bears (70%) denned in the inland zone. Females that denned near the coast entered dens later (x̄ = 22 Nov) than females that denned inland (x̄ = 12 Nov). Two radio-collared bears were known to raid deer-hunting camps and 9 other marked bears were observed by hunters or were located <200 m from hunting camps. Deer-hunter surveys revealed that more than two-thirds of the deer harvest occurred during October-November. About half of the hunters observed at least 1 bear during their hunt. Seven to 21% of the respondents reported having a threatening encounter with a bear and 5-26% reported losing deer meat to bears. Human-induced mortality to radio-collared bears occurred more often near the coast (5) than inland (3); 7 bears were harvested by sport hunters and 1 was killed (nonsport) in a Native village. Deer hunters killed 2 unmarked females in defense of life or property situations in the study area. High bear densities and concentrated deer-hunting activity combine to make conflicts unavoidable. Adverse impacts to bears can be minimized by maintaining low levels of human activity in inland areas and improving hunter awareness of bear ecology and behavior.

Recent Advances in Hyporheic Zone Science

NASA Astrophysics Data System (ADS)

Hester, E. T.

2017-12-01

The hyporheic zone exists beneath and adjacent to streams and rivers where surface water and groundwater interact. It provides unique habitat for aquatic organisms, can buffer surface water temperatures, and can be highly reactive, processing nutrients and improving water quality. The hyporheic zone is the subject of considerable research and the past year in WRR witnessed important conceptual advances. A key focus was rigorous evaluation of mixing between surface water and groundwater that occurs within hyporheic sediments. Field observations indicate that greater mixing occurs in the hyporheic zone than in deeper groundwater, and this distinction has been explored by recent numerical modeling studies, but more research is needed to fully understand the causes. A commentary this year in WRR proposed that hyporheic mixing is enhanced by a combination of fluctuating boundary conditions and multiscale physical and chemical spatial heterogeneity but confirmation is left to future research. This year also witnessed the boundaries of knowledge pushed back in a number of other key areas. Field quantification of hyporheic exchange and reactions benefited from advances including the use and interpretation of high frequency nutrient sensors, actively heater fiber optic sensors, isotope tracers, and geophysical methods such as electrical resistivity imaging. Conceptual advances were made in understanding the effects of unsteady environmental conditions (e.g., tides and storms) and preferential flow on hyporheic processes. Finally, hyporheic science is being brought increasingly to bear on applied issues such as informing nutrient removal crediting for stream restoration practices, for example in the Chesapeake Bay watershed.

Unraveling signatures of biogeochemical processes and the depositional setting in the molecular composition of pore water DOM across different marine environments

NASA Astrophysics Data System (ADS)

Schmidt, Frauke; Koch, Boris P.; Goldhammer, Tobias; Elvert, Marcus; Witt, Matthias; Lin, Yu-Shih; Wendt, Jenny; Zabel, Matthias; Heuer, Verena B.; Hinrichs, Kai-Uwe

2017-06-01

Dissolved organic matter (DOM) in marine sediment pore waters derives largely from decomposition of particulate organic matter and its composition is influenced by various biogeochemical and oceanographic processes in yet undetermined ways. Here, we determine the molecular inventory of pore water DOM in marine sediments of contrasting depositional regimes with ultrahigh-resolution mass spectrometry and complementary bulk chemical analyses in order to elucidate the factors that shape DOM composition. Our sample sets from the Mediterranean, Marmara and Black Seas covered different sediment depths, ages and a range of marine environments with different (i) organic matter sources, (ii) balances of organic matter production and preservation, and (iii) geochemical conditions in sediment and water column including anoxic, sulfidic and hypersaline conditions. Pore water DOM had a higher molecular formula richness than overlying water with up to 11,295 vs. 2114 different molecular formulas in the mass range of 299-600 Da and covered a broader range of element ratios (H/C = 0.35-2.19, O/C = 0.03-1.19 vs. H/C = 0.56-2.13, O/C = 0.15-1.14). Formula richness was independent of concentrations of DOC and TOC. Near-surface pore water DOM was more similar to water column DOM than to deep pore water DOM from the same core with respect to formula richness and the molecular composition, suggesting exchange at the sediment-water interface. The DOM composition in the deeper sediments was controlled by organic matter source, selective decomposition of specific DOM fractions and early diagenetic molecule transformations. Compounds in pelagic sediment pore waters were predominantly highly unsaturated and N-bearing formulas, whereas oxygen-rich CHO-formulas and aromatic compounds were more abundant in pore water DOM from terrigenous sediments. The increase of S-bearing molecular formulas in the water column and pore waters of the Black Sea and the Mediterranean Discovery Basin was consistent with elevated HS- concentrations reflecting the incorporation of sulfur into biomolecules during early diagenesis. Sulfurization resulted in an increased average molecular mass of DOM and higher formula richness (up to 5899 formulas per sample). In sediments from the methanogenic zone in the Black Sea, the DOM pool was distinctly more reduced than overlying sediments from the sulfate-reducing zone. Bottom and pore water DOM from the Discovery Basin contained the highest abundances of aliphatic compounds in the entire dataset; a large fraction of abundant N-bearing formulas possibly represented peptide and nucleotide formulas suggesting preservation of these molecules in the life inhibiting environment of the Discovery Basin. Our unique data set provides the basis for a comprehensive understanding of the molecular signatures in pore water DOM and the turnover of sedimentary organic matter in marine sediments.

Subsurface injection of treated sewage into a saline-water aquifer at St. Petersburg, Florida - Aquifer pressure buildup

USGS Publications Warehouse

Hickey, J.J.

1984-01-01

The city of St. Petersburg has been testing subsurface injection of treated sewage into the Floridan aquifer as a means of eliminating discharge of sewage to surface waters and as a means of storing treated sewage for future nonpotable reuse. Treated sweage that had a mean chloride concentration of 170 milligrams per liter (mg/l) was injected through a single well for 12 months at a mean rate of 4. 7 multiplied by 10**5 cubic feet per day (ft**3/d). The volume of water injected during the year was 1. 7 multiplied by 10**8 cubic feet. Pressure buildup at the end of one year ranged from less than 0. 1 to as much as 2. 4 pounds per square inch (lb/in**2) in observation wells at the site. Pressure buildup in wells open to the upper part of the injection zone was related to buoyant lift acting on the mixed water in the injection zone in addition to subsurface injection through the injection well. Calculations of the vertical component of pore velocity in the semiconfining bed underlying the shallowest permeable zone of the Floridan aquifer indicate upward movement of native water.

Comparative water relations of adjacent california shrub and grassland communities.

PubMed

Davis, S D; Mooney, H A

1985-07-01

Much of the coastal mountains and foothills of central and southern California are covered by a mosaic of grassland, coastal sage scrub, and evergreen sclerophyllous shrubs (chaparral). In many cases, the borders between adjacent plant communities are stable. The cause of this stability is unknown. The purpose of our study was to examine the water use patterns of representative grasses, herbs, and shrubs across a grassland/chaparrel ecotone and determine the extent to which patterns of water use contribute to ecotone stability. In addition, we examined the effects of seed dispersal and animal herbivory. We found during spring months, when water was not limited, grassland species had a much higher leaf conductance to water vapor diffusion than chaparral plants. As the summer drought progressed, grassland species depleted available soil moisture first, bare zone plants second, and chaparral third, with one chaparral species (Quercus durata) showing no evidence of water stress. Soil moisture depletion patterns with depth and time corresponded to plant water status and root depth. Rabbit herbivory was highest in the chaparral and bare zone as indicated by high densities of rabbit pellets. Dispersal of grassland seeds into the chaparral and bare zone was low. Our results support the hypothesis that grassland species deplete soil moisture in the upper soil horizon early in the drought, preventing the establishment of chaparral seedlings or bare zone herbs. Also, grassland plants are prevented from invading the chaparral because of low seed dispersability and high animal herbivory in these regions.

Expanded record of Quaternary oceanographic change: Amerasian Arctic Ocean

USGS Publications Warehouse

Ishman, S.E.; Polyak, L.V.; Poore, R.Z.

1996-01-01

Four sediment cores collected from the Northwind and Mendeleyev ridges, Arctic Ocean, from 1089 m to 1909 m water depth, provide an oceanographic record extending back into the Matuyama reversed polarity chron. Benthic foraminiferal analyses show four prominent assemblage zones: Bolivina arctica, Cassidulina teretis, Bulimina aculeata, and Oridorsalis tener from the upper Matuyama reversed polarity chronozone through the Brunhes normal polarity chronozone. These assemblage zones represent depth-dependent benthic foraminiferal biofacies changes associated with oceanographic events that occurred in the Amerasian basin at ??? 780 and 300 ka, and indicate oceanographic influence from the North Atlantic. Recognition of these benthic assemblage zones in Arctic cores from the Alpha Ridge indicates that the benthic foraminiferal zonations in intermediate to deep water (>1000 m) Arctic cores may be more useful than preexisting lithostratigraphic zonations and should provide important information pertaining to the Quaternary paleoceanographic evolution of the Arctic Ocean.

Preliminary assessment of injection, storage, and recovery of freshwater in the lower Hawthorn aquifer, Cape Coral, Florida

USGS Publications Warehouse

Quinones-Aponte, Vicente; Wexler, Eliezer J.

1995-01-01

A preliminary assessment of subsurface injection, storage and recovery of fresh canal water was made in the naturally brackish lower Hawthorn aquifer in Cape Coral, southwestern Florida. A digital modeling approach was used for this preliminary assessment, incorporating available data on hydrologic conditions, aquifer properties, and water quality to simulate density-dependent ground-water flow and advective-dispersive transport of a conservative ground-water solute (chloride ion). A baseline simulation was used as reference to compare the effects of changing various operational factors on the recovery efficiency. A recovery efficiency of 64 percent was estimated for the baseline simulation. Based on the model, the recovery efficiency increases if the injection rate and recovery rates are increased and if the ratio of recovery rate to injection rate is increased. Recovery efficiency decreases if the amount of water injected is increased; slightly decreases if the storage time is increased; is not changed significantly if the water is injected to a specific flow zone; increases with successive cycles of injection, storage, and recovery; and decreases if the chloride concentrations in either the injection water or native aquifer water are increased. In everal hypothetical tests, the recovery efficiency fluctuated between 22 and about 100 percent. Two successive cycles could bring the recovery efficiency from 60 to about 80 percent. Interlayer solute mass movement across the upper and lower boundaries seems to be the most important factor affecting the recovery efficiency. A sensitivity analysis was performed applying a technique in which the change in the various factors and the corresponding model responses are normalized so that meaningful comparisons among the responses could be made. The general results from the sensitivity analysis indicated that the permeabilities of the upper and lower flow zones were the most important factors that produced the greatest changes in the relative sensitivity of the recovery efficiency. Almost equally significant changes occurred in the relative sensitivity of the recovery efficiency when all porosity values of the upper and lower flow zones and the leaky confining units and the vertical anisotropy ratio were changed. The advective factors are the most important in the Cape Coral area according to the sensitivity analysis. However, the dispersivity values used in the model were extrapolated from studies conducted at the nearby Lee County Water Treatment Plant, and these values might not be representative of the actual dispersive characteristics of the lower Hawthorn aquifer in the Cape Coral area.

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

USGS Publications Warehouse

Santamarina, J.C.; Dai, Shifeng; Terzariol, M.; Jang, Jeonghwan; Waite, William F.; Winters, William J.; Nagao, J.; Yoneda, J.; Konno, Y.; Fujii, T.; Suzuki, K.

2015-01-01

Natural hydrate-bearing sediments from the Nankai Trough, offshore Japan, were studied using the Pressure Core Characterization Tools (PCCTs) to obtain geomechanical, hydrological, electrical, and biological properties under in situ pressure, temperature, and restored effective stress conditions. Measurement results, combined with index-property data and analytical physics-based models, provide unique insight into hydrate-bearing sediments in situ. Tested cores contain some silty-sands, but are predominantly sandy- and clayey-silts. Hydrate saturations Sh range from 0.15 to 0.74, with significant concentrations in the silty-sands. Wave velocity and flexible-wall permeameter measurements on never-depressurized pressure-core sediments suggest hydrates in the coarser-grained zones, the silty-sands where Sh exceeds 0.4, contribute to soil-skeletal stability and are load-bearing. In the sandy- and clayey-silts, where Sh < 0.4, the state of effective stress and stress history are significant factors determining sediment stiffness. Controlled depressurization tests show that hydrate dissociation occurs too quickly to maintain thermodynamic equilibrium, and pressure–temperature conditions track the hydrate stability boundary in pure-water, rather than that in seawater, in spite of both the in situ pore water and the water used to maintain specimen pore pressure prior to dissociation being saline. Hydrate dissociation accompanied with fines migration caused up to 2.4% vertical strain contraction. The first-ever direct shear measurements on never-depressurized pressure-core specimens show hydrate-bearing sediments have higher sediment strength and peak friction angle than post-dissociation sediments, but the residual friction angle remains the same in both cases. Permeability measurements made before and after hydrate dissociation demonstrate that water permeability increases after dissociation, but the gain is limited by the transition from hydrate saturation before dissociation to gas saturation after dissociation. In a proof-of-concept study, sediment microbial communities were successfully extracted and stored under high-pressure, anoxic conditions. Depressurized samples of these extractions were incubated in air, where microbes exhibited temperature-dependent growth rates.

The distributions of, and relationship between, 3He and nitrate in eddies

NASA Astrophysics Data System (ADS)

Jenkins, W. J.; McGillicuddy, D. J., Jr.; Lott, D. E., III

2008-05-01

We present and discuss the distribution of 3He and its relationship to nutrients in two eddies (cyclone C1 and anticyclone A4) with a view towards examining eddy-related mechanisms whereby nutrients are transported from the upper 200-300 m into the euphotic zone of the Sargasso Sea. The different behavior of these tracers in the euphotic zone results in changes in their distributions and relationships that may provide important clues as to the nature of physical and biological processes involved. The cyclonic eddy (C1) is characterized by substantial 3He excesses within the euphotic zone. The distribution of this excess 3He is strongly suggestive of both past and recent ongoing deep-water injection into the euphotic zone. Crude mass balance calculations suggest that an average of approximately 1.4±0.7 mol m -2 of nitrate has been introduced into the euphotic zone of eddy C1, consistent with the integrated apparent oxygen utilization anomaly in the aphotic zone below. The 3He-NO 3 relationship within the eddy deviates substantially from the linear thermocline trend, suggestive of incomplete drawdown of nutrients and/or substantial mixing between euphotic and aphotic zone waters. Anticyclone (A4) displays a simpler 3He-NO 3 relationship, but is relatively impoverished in euphotic zone excess 3He. We suggest that because of the relatively strong upwelling and lateral divergence of water the residence time of upwelled 3He is relatively short within the euphotic zone of this eddy. An estimate of the recently upwelled nutrient inventory, based on the excess 3He observed in A4's lower euphotic zone, is stoichiometrically consistent with the oxygen maximum observed in the euphotic zone.

Ground-water resources of Flagler County, Florida

USGS Publications Warehouse

Navoy, A.S.; Bradner, L.A.

1987-01-01

Groundwater is the only significant source of potable water in Flagler County. Usable water occurs in the Upper Floridan aquifer, the intermediate population is expected to place stresses on the water resources of the county. Although rainfall averages almost 50 in/yr, most of the water leaves as evapotranspiration and streamflow. Less than 1 in/yr recharge may be occurring to the Upper Floridan aquifer, the highest yielding aquifer. The Upper Floridan aquifer consists of the Avon Park Formation, the Ocala Limestone, and the basal dolomitic limestone of the Hawthorne. Use of the Upper Floridan aquifer for public water supply is limited in most of the county because it contains marginally potable or brackish water. It is used extensively for agricultural irrigation. The intermediate aquifer system consists of thin, discontinues lenses of sand, shell, and limestone between clays overlying the Floridan aquifer system. The intermediate aquifer system is an important part of the public water supply of the county because of the good quality of the water. The intermediate aquifer system has variable yields because of the discontinuous lenses. The surficial aquifer system is composed of sand and shell with varying fractions of finer materials. Well yields are small in the west and central parts of Flagler County, but the surficial aquifer system is an adequate source of domestic supply on the barrier island. A zone of freshwater in the surficial aquifer system is very important in the Hammock area, being the local source of most domestic supply in the area. Changes in hydrologic conditions from the 1950 's include a long-term decline in water levels in the Upper Floridan aquifer coincident with lower-than-average rainfall and a greater seasonal fluctuation of water levels. Chloride concentrations of water in the Upper Floridan aquifer do not appear to have changed significantly, presently ranging from 7 to 3,700 mg/L. Development will place stress on the aquifers and may result in upconing of brackish water in pumping centers and in lateral saltwater intrusion in coastal areas. (Author 's abstract)

Deformation associated to exhumation by detachment faulting of upper mantle rocks in a fossil Ocean Continent Transition: The example of the Totalp unit in SE Switzerland

NASA Astrophysics Data System (ADS)

Picazo, S.; Manatschal, G.; Cannat, M.

2013-12-01

The exhumation of upper mantle rocks along detachment faults is widespread at Mid-Ocean Ridges and at the Ocean-Continent Transition (OCT) of rifted continental margins. Thermo-mechanical models indicate that significant strain softening of the fault rocks in the footwall is required in order to produce such large fault offsets. Our work focuses on deformation textures, and the associated mineralogy in ultramafic rocks sampled in the upper levels of the footwall next to the exhumation fault. We present two OCT examples, the Totalp relict of a paleo-Tethys OCT exposed in SE Switzerland, and the Iberian distal margin (ODP Leg 173 Site 1070). We built a new geological map and a section of the Totalp unit near Davos (SE Switzerland) and interpreted this area as a local exposure of a paleo-seafloor that is formed by an exhumed detachment surface and serpentinized peridotites. The top of the exhumed mantle rocks is made of ophicalcites that resulted from the carbonation of serpentine under static conditions at the seafloor. The ophicalcites preserve depositional contacts with Upper Jurassic to Lower Cretaceous pelagic sediments. These sequences did not exceed prehnite-pumpellyite metamorphic facies conditions, and locally escaped Alpine deformation. Thin mylonitic shear zones as well as foliated amphibole-bearing ultramafic rocks have been mapped. The age of these rocks and the link with the final exhumation history are yet unknown but since amphibole-bearing ultramafic rocks can be found as clasts in cataclasites related to the detachment fault, they pre-date detachment faulting. Our petrostructural study of the exhumed serpentinized rocks also reveals a deformation gradient from cataclasis to gouge formation within 150m in the footwall of the proposed paleo-detachment fault. This deformation postdates serpentinization. It involves a component of plastic deformation of serpentine in the most highly strained intervals that has suffered pronounced grain-size reduction and a polyphase cataclastic overprint.

Slab temperature controls on the Tonga double seismic zone and slab mantle dehydration

PubMed Central

Wei, S. Shawn; Wiens, Douglas A.; van Keken, Peter E.; Cai, Chen

2017-01-01

Double seismic zones are two-layered distributions of intermediate-depth earthquakes that provide insight into the thermomechanical state of subducting slabs. We present new precise hypocenters of intermediate-depth earthquakes in the Tonga subduction zone obtained using data from local island–based, ocean-bottom, and global seismographs. The results show a downdip compressional upper plane and a downdip tensional lower plane with a separation of about 30 km. The double seismic zone in Tonga extends to a depth of about 300 km, deeper than in any other subduction system. This is due to the lower slab temperatures resulting from faster subduction, as indicated by a global trend toward deeper double seismic zones in colder slabs. In addition, a line of high seismicity in the upper plane is observed at a depth of 160 to 280 km, which shallows southward as the convergence rate decreases. Thermal modeling shows that the earthquakes in this “seismic belt” occur at various pressures but at a nearly constant temperature, highlighting the important role of temperature in triggering intermediate-depth earthquakes. This seismic belt may correspond to regions where the subducting mantle first reaches a temperature of ~500°C, implying that metamorphic dehydration of mantle minerals in the slab provides water to enhance faulting. PMID:28097220

Vadose Zone Nitrate Transport Dynamics Resulting from Agricultural Groundwater Banking

NASA Astrophysics Data System (ADS)

Murphy, N. P.; McLaughlin, S.; Dahlke, H. E.

2017-12-01

In recent years, California's increased reliance on groundwater resources to meet agricultural and municipal demands has resulted in significant overdraft and water quality issues. Agricultural groundwater banking (AGB) has emerged as a promising groundwater replenishment opportunity in California; AGB is a form of managed aquifer recharge where farmland is flooded during the winter using excess surface water in order to recharge the underlying groundwater. Suitable farmland that is connected to water delivery systems is available for AGB throughout the Central Valley. However, questions remain how AGB could be implemented on fertilized agricultural fields such that nitrate leaching from the root zone is minimized. Here, we present results from field and soil column studies that investigate the transport dynamics of nitrogen in the root and deeper vadose zone during flooding events. We are specifically interested in estimating how timing and duration of flooding events affect percolation rates, leaching and nitrification/denitrification processes in three soil types within the Central Valley. Laboratory and field measurements include nitrogen (NO3-, NH4+, NO2-, N2O), redox potentials, total organic carbon, dissolved oxygen, moisture content and EC. Soil cores are collected in the field before and after recharge events up to a depth of 4m, while other sensors monitor field conditions continuously. Preliminary results from the three field sites show that significant portions of the applied floodwater (12-62 cm) infiltrated below the root zone: 96.1% (Delhi), 88.6% (Modesto) and 76.8% (Orland). Analysis of the soil cores indicate that 70% of the residual nitrate was flushed from the sandy soil, while the fine sandy loam showed only a 5% loss and in some cores even an increase in soil nitrate (in the upper 20cm). Column experiments support these trends and indicate that increases in soil nitrate in the upper root zone might be due to organic nitrogen mineralization and nitrification, facilitated by the added water. The next step will be to use field and laboratory data for the parameterization of the HP1 (Coupled Hydrus-1D and PHREEQC) model to develop an understanding of nitrogen transport in differing soil textures, and develop best management practices for future AGB projects.

Fault-related fluid flow, Beech Mountain thrust sheet, Blue Ridge Province, Tennessee-North Carolina

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waggoner, W.K.; Mora, C.I.

1992-01-01

The latest proterozoic Beech Granite is contained within the Beech Mountain thrust sheet (BMTS), part of a middle-late Paleozoic thrust complex located between Mountain City and Grandfather Mountain windows in the western Blue Ridge of TN-NC. At the base of the BMTS, Beech Granite is juxtaposed against lower Paleozoic carbonate and elastics of the Rome Fm. along the Stone Mountain thrust on the southeaster margin of the Mountain City window. At the top of the BMTS, Beech Granite occurs adjacent to Precambrian mafic rocks of the Pumpkin Patch thrust sheet (PPTS). The Beech Granite is foliated throughout the BMTS withmore » mylonitization and localized cataclasis occurring within thrust zones along the upper and lower margins of the BMTS. Although the degree of mylonitization and cataclasis increases towards the thrusts, blocks of relatively undeformed granite also occur within these fault zones. Mylonites and thrusts are recognized as conduits for fluid movement, but the origin of the fluids and magnitude and effects of fluid migration are not well constrained. This study was undertaken to characterize fluid-rock interaction within the Beech Granite and BMTS. Extensive mobility of some elements/compounds within the thrust zones, and the isotopic and mineralogical differences between the thrust zones and interior of the BMTS indicate that fluid flow was focused within the thrust zones. The wide range of elevated temperatures (400--710 C) indicated by qz-fsp fractionations suggest isotopic disequilibrium. Using a more likely temperature range of 300--400 C for Alleghanian deformation, calculated fluid compositions indicate interactions with a mixture of meteoric-hydrothermal and metamorphic water with delta O-18 = 2.6--7.5[per thousand] for the upper thrust zone and 1.3 to 6.2[per thousand] for the lower thrust zone. These ranges are similar to isotopic data reported for other Blue Ridge thrusts and may represent later periods of meteoric water influx.« less

Role of surface and subsurface processes in scaling N2O emissions along riverine networks

PubMed Central

Marzadri, Alessandra; Dee, Martha M.; Tonina, Daniele; Bellin, Alberto; Tank, Jennifer L.

2017-01-01

Riverine environments, such as streams and rivers, have been reported as sources of the potent greenhouse gas nitrous oxide (N2O) to the atmosphere mainly via microbially mediated denitrification. Our limited understanding of the relative roles of the near-surface streambed sediment (hyporheic zone), benthic, and water column zones in controlling N2O production precludes predictions of N2O emissions along riverine networks. Here, we analyze N2O emissions from streams and rivers worldwide of different sizes, morphology, land cover, biomes, and climatic conditions. We show that the primary source of N2O emissions varies with stream and river size and shifts from the hyporheic–benthic zone in headwater streams to the benthic–water column zone in rivers. This analysis reveals that N2O production is bounded between two N2O emission potentials: the upper N2O emission potential results from production within the benthic–hyporheic zone, and the lower N2O emission potential reflects the production within the benthic–water column zone. By understanding the scaling nature of N2O production along riverine networks, our framework facilitates predictions of riverine N2O emissions globally using widely accessible chemical and hydromorphological datasets and thus, quantifies the effect of human activity and natural processes on N2O production. PMID:28400514

Regional Hydrogeochemistry of a Modern Coastal Mixing Zone

NASA Astrophysics Data System (ADS)

Wicks, Carol M.; Herman, Janet S.

1996-02-01

In west central Florida, groundwater samples were collected along flow paths in the unconfined upper Floridan aquifer that cross the inland, freshwater recharge area and the coastal discharge area. A groundwater flow and solute transport model was used to evaluate groundwater flow and mixing of fresh and saline groundwater along a cross section of the unconfined upper Floridan aquifer. Results show that between 8% and 15% of the fresh and 30-31% of the saline groundwater penetrates to the depth in the flow system where contact with and dissolution of gypsum is likely. The deeply circulating fresh and saline groundwater returns to the near-surface environment discharging CaSO4-rich water to the coastal area where it mixes with fresh CaHCO3 groundwater, resulting in a prediction of calcite precipitation in the modern mixing zone.

From orogenic buildup to extensional unroofing: the evolution of the Adria - Europe collisional zone in the Medvednica Mountains of Croatia

NASA Astrophysics Data System (ADS)

Beniest, Anouk; van Gelder, Inge; Matenco, Liviu; Willingshofer, Ernst; Gruic, Andrea; Tomljenovic, Bruno

2013-04-01

Quantifying the kinematics of the Miocene extension in the Pannonian Basin is of critical importance for understanding the evolution of Adria-Europe collision in particular in the transitional zone from the Alps (Adria the upper plate) to the Dinarides (Adria the lower plate). Recent studies have demonstrated that large-scale extensional unroofing and core-complex formation affected the Europe-Adria contact in the Dinarides during Miocene times. The relationship between this extensional exhumation of Adriatic units and the roughly coeval Miocene extension affecting the Alpine-derived units during their E-ward extrusion into the intra-Carpathians ALCAPA block and the formation of the Pannonian basin is still unknown. One key area situated in the transitional zone is the Medvednica Mountains of Croatia, an area that benefits from already existing and extensive petrological and structural studies. The area of the Medvednica Mountains has been targeted by the means of a field kinematic analysis complemented by low-temperature thermochronology, metamorphic petrology and sedimentological observations. The results demonstrate that two units, reflecting distinct Adriatic paleogeographical positions, make up the structural geometry of the mountains. The upper unit contains Paleozoic mostly fine clastic sequence metamorphosed in sub-greenschist facies, overlain by a proximal Adriatic facies consisting of Triassic shallow water carbonates. The lower unit is made up by a volcanic sequence overlain by gradual deepening Triassic carbonates metamorphosed in greenschist facies that bears a strong resemblance to the Triassic break-up volcanism and subsequent sedimentation affecting the distal Adriatic units observed elsewhere in the Jadar-Kopaonik unit of the Dinarides. The strong contrast between the Middle-Upper Triassic facies suggests large scale thrusting during Cretaceous nappe stacking. Subsequently, the studied area has been affected by significant extensional deformation creating the present-day turtleback geometry. This resulted in the formation of brittle normal faults in both units, locally tilted by the uplift of the mountain core, which indicate mostly NE-SW extension. The lower unit is affected by a pervasive deformation characterized by a wide mylonitic shear zone with stretching lineations indicating consistently top-NE to E sense of shear. The present-day structural geometry of the mountains was established during the Pliocene-Quaternary inversion. The exact ages of nappe-stacking and subsequent extensional exhumation will be clarified by the upcoming low-temperature thermochronology and absolute age dating study. However, available results demonstrate that the extensional geometry and sense of shear is typical for the Miocene extensional exhumation and basin formation that affected the Adria-Europe contact elsewhere in the Dinarids, e.g. Kozara-Prosara-Motajica and Fruska Gora extensional structures. By comparing similar extensional features observed in for instance the Rechnitz and Pohorje extensional structures, the combined study potentially demonstrates that the Miocene mechanism of extension and sense of shear is structurally coherent at the scale of the entire Dinaridic and Alpine margins.

Influence of stretching and density contrasts on the chemical evolution of continental magmas: An example from the Ivrea-Verbano Zone

USGS Publications Warehouse

Sinigoi, S.; Quick, J.E.; Mayer, A.; Budahn, J.

1996-01-01

The southern Ivrea-Verbano Zone of the Italian Western Alps contains a huge mafic complex that intruded high-grade metamorphic rocks while they were resident in the lower crust. Geologic mapping and chemical variations of the igneous body were used to study the evolution of underplated crust. Slivers of crustal rocks (septa) interlayered with igneous mafic rocks are concentrated in a narrow zone deep in the complex (Paragneiss-bearing Belt) and show evidence of advanced degrees of partial melting. Variations of rare-earth-element patterns and Sr isotope composition of the igneous rocks across the sequence are consistent with increasing crustal contamination approaching the septa. Therefore, the Paragneiss-bearing Belt is considered representative of an "assimilation region" where in-situ interaction between mantle- and crust-derived magmas resulted in production of hybrid melts. Buoyancy caused upwards migration of the hybrid melts that incorporated the last septa and were stored at higher levels, feeding the Upper Mafic Complex. Synmagmatic stretching of the assimilation region facilitated mixing and homogenization of melts. Chemical variations of granitoids extracted from the septa show that deep septa are more depleted than shallow ones. This suggests that the first incorporated septa were denser than the later ones, as required by the high density of the first-injected mafic magmas. It is inferred that density contrasts between mafic melts and crustal rocks play a crucial role for the processes of contamination of continental magmas. In thick under- plated crust, the extraction of early felsic/hybrid melts from the lower crust may be required to increase the density of the lower crust and to allow the later mafic magmas to penetrate higher crustal levels.

Effects of historical coal mining and drainage from abandoned mines on streamflow and water quality in Bear Creek, Dauphin County, Pennsylvania-March 1999-December 2002

USGS Publications Warehouse

Chaplin, Jeffrey J.

2005-01-01

More than 100 years of anthracite coal mining has changed surface- and ground-water hydrology and contaminated streams draining the Southern Anthracite Coal Field in east-central Pennsylvania. Bear Creek drains the western prong of the Southern Anthracite Coal Field and is affected by metals in drainage from abandoned mines and streamwater losses. Total Maximum Daily Loads (TMDL) developed for dissolved iron of about 5 lb/d (pounds per day) commonly are exceeded in the reach downstream of mine discharges. Restoration of Bear Creek using aerobic ponds to passively remove iron in abandoned mine drainage is under consideration (2004) by the Dauphin County Conservation District. This report, prepared in cooperation with the Dauphin County Conservation District, evaluates chemical and hydrologic data collected in Bear Creek and its receiving waters prior to implementation of mine-drainage treatment. The data collected represent the type of baseline information needed for documentation of water-quality changes following passive treatment of mine drainage in Pennsylvania and in other similar hydrogeologic settings. Seven surface-water sites on Bear Creek and two mine discharges were monitored for nearly three years to characterize the chemistry and hydrology of the following: (1) Bear Creek upstream of the mine discharges (BC-UMD), (2) water draining from the Lykens-Williamstown Mine Pool at the Lykens Water-Level Tunnel (LWLT) and Lykens Drift (LD) discharges, (3) Bear Creek after mixing with the mine discharges (BC-DMD), and (4) Bear Creek prior to mixing with Wiconisco Creek (BCM). Two sites on Wiconisco Creek, upstream and downstream of Bear Creek (WC-UBC and WC-DBC, respectively), were selected to evaluate changes in streamflow and water quality upon mixing with Bear Creek. During periods of below-normal precipitation, streamwater loss was commonly 100 percent upstream of site BC-UMD (streamflow range = 0 to 9.7 ft3/s (cubic feet per second)) but no loss was detected downstream owing to sustained mine water drainage from the Lykens Water-Level Tunnel (range = 0.41 to 3.7 ft3/s), Lykens Drift (range = 0.40 to 6.1 ft3/s), and diffuse zones of seepage. Collectively, mine water inputs contributed about 84 percent of base flow and 53 percent of stormflow measured in the downstream reach. An option under consideration by the Dauphin County Conservation District for treatment of the discharge from the LWLT requires the source of the discharge to be captured and rerouted downstream, bypassing approximately 1,000 feet of stream channel. Because streamwater loss upstream of the tunnel was commonly 100 percent, rerouting the discharge from the LWLT may extend the reach of Bear Creek that is subject to dryness. Differences in the chemistry of water discharging from the LWLT compared to the LD suggest that the flow path through the Lykens-Williamstown Mine Pool to each mine discharge is unique. The LWLT is marginally alkaline (median net acid neutralizing capacity (ANC) = 9 mg/L (milligrams per liter) as CaCO3; median pH = 5.9), commonly becomes acidic (minimum net ANC = -74 mg/L as CaCO3) at low flow, and may benefit from alkaline amendments prior to passive treatment. Water discharging from the LD provides excess ANC (median net ANC = 123 mg/L as CaCO3; median pH = 6.5) to the downstream reach and is nearly anoxic at its source (median dissolved oxygen = 0.5 mg/L). Low dissolved oxygen water with relatively high ANC and metals concentrations discharging from the LD is characteristic of a deeper flow path and longer residence time within the mine pool than the more acidic, oxygenated water discharging from the LWLT. TMDLs for iron have been developed for dissolved species only. Consequently, distinguishing between dissolved and suspended iron in Bear Creek is important for evaluating water-quality improvement through TMDL attainment. Median total iron concentration increased from 550 mg/L (micrograms per liter) at site BC-UM

Hydrogeology of Middle Canyon, Oquirrh Mountains, Tooele County, Utah

USGS Publications Warehouse

Gates, Joseph Spencer

1963-01-01

Geology and climate are the principal influences affecting the hydrology of Middle Canyon, Tooele County, Utah. Reconnaissance in the canyon indicated that the geologic influences on the hydrology may be localized; water may be leaking through fault and fracture zones or joints in sandstone and through solution openings in limestone of the Oquirrh formation of Pennsylvanian and Permian age. Surficial deposits of Quaternary age serve as the main storage material for ground water in the canyon and transmit water from the upper canyon to springs and drains at the canyon mouth. The upper canyon is a more important storage area than the lower canyon because the surficial deposits are thicker, and any zones of leakage in the underlying bedrock of the upper canyon probably would result in greater leakage than would similar outlets in the lower canyon.The total annual discharge from Middle Canyon, per unit of precipitation, decreased between 1910 and 1939. Similar decreases occurred in Parleys Canyon in the nearby Wasatch Range and in other drainage basins in Utah, and it is likely that most of the decrease in discharge from Middle Canyon and other canyons in Utah is due to a change in climate.Chemical analyses of water showed that the high content of sulfate and other constituents in the water from the Utah Metals tunnel, which drains into Middle Canyon, does not have a significant effect on water quality at the canyon mouth. This suggests that much of the tunnel water is lost from the channel by leakage, probably in the upper canyon, during the dry part of the year.Comparison of the 150 acre-feet of water per square mile of drainage area discharged by Middle Canyon in 1947 with the 623 and 543 acre-feet per square mile discharged in 1948 by City Creek and Mill Creek Canyons, two comparable drainage basins in the nearby Wasatch Range, also suggests that there is leakage in Middle Canyon.A hydrologic budget of the drainage basin results in an estimate that about 3,000 acre-feet of water was unaccounted for in the 1947 water year. This may represent a reasonable estimate of annual leakage from Middle Canyon.The future development of Middle Canyon water can best be planned after additional information is obtained on movement of water through the channel fill. Much of this information could be supplied by test drilling in the channel fill.

Sequence stratigraphic controls on synsedimentary cementation and preservation of dinosaur tracks: Example from the lower Cretaceous, (Upper Albian) Dakota Formation, Southeastern Nebraska, U.S.A.

USGS Publications Warehouse

Phillips, P.L.; Ludvigson, Greg A.; Matthew, Joeckel R.; Gonzalez, Luis A.; Brenner, Richard L.; Witzke, B.J.

2007-01-01

A thin cemented sandstone bed in the Upper Albian Dakota Formation of southeastern Nebraska contains the first dinosaur tracks to be described from the state. Of equal importance to the tracks are stable-isotope (C, O) analyses of cements in the track bed, especially in the context of data derived from generally correlative strata (sandstones and sphaerosiderite-bearing paleosols) in the region. These data provide the framework for interpretations of paleoenvironmental conditions, as well as a novel approach to understanding mechanisms of terrestrial vertebrate track preservation. High minus-cement-porosity (> 47%) and low grain-to-grain contacts (???2.5) in the track bed indicate early (pre-compaction) lithification. Although phreatic cements dominate, the history of cementation within this stratigraphic interval is complex. Cathodoluminescence petrography reveals two distinct calcite zones in the track-bearing horizon and four cement zones in stratigraphically equivalent strata from a nearby section. The earliest calcite cements from both localities are likely coeval because they exhibit identical positive covariant trends (??18O values of - 9.89 to - 6.32??? and ??13C values of - 28.01 to - 19.33??? VPDB) and record mixing of brackish and meteoric groundwaters. All other calcite cements define meteoric calcite lines with ??18O values clustering around - 9.42??? and - 8.21??? VPDB from the track-bearing horizon, and - 7.74???, - 5.81???, and - 3.95??? VPDB from the neighboring section. Distinct meteoric sphaerosiderite lines from roughly correlative paleosols serve as a proxy for locally recharged groundwaters. Back-calculated paleogroundwater ??18O estimates from paleosol sphaerosiderites range from - 7.4 to - 4.2??? SMOW; whereas, meteoric calcite lines from the track horizon are generally more depleted. Differences in cement ??18O values record changes in paleogroundwater recharge areas over time. Early calcite cements indicate mixing of fresh and brackish groundwaters during the syndepositional lithification of the track horizon. Later calcite cements, however, indicate recharge from a larger catchment basin that extended far inland. Therefore, the cements likely record a rise and subsequent fall in relative sea level. We conclude that scrutiny of the cement isotope geochemistry of genetically significant surfaces, especially track beds, can provide new data for interpreting sea level change. ?? 2006 Elsevier B.V. All rights reserved.

Geological, petrogical and geochemical characteristics of granitoid rocks in Burma: with special reference to the associated WSn mineralization and their tectonic setting

NASA Astrophysics Data System (ADS)

Zaw, Khin

The granitoid rocks in Burma extend over a distance of 1450 km from Putao, Kachin State in the north, through Mogok, Kyaukse, Yamethin and Pyinmana in the Mandalay Division, to Tavoy and Mergui areas, Tenasserim Division, in the south. The Burmese granitoids can be subdivided into three N-S trending, major belts viz. western granitoid belt, central graniotoid belt and eastern granitoid belt. The Upper Cretaceous-Lower Eocene western belt granitoids are characterized by high-level intrusions associated with porphyry Cu(Au) related, younger volcanics; these plutonic and volcanic rocks are thought to have been emplaced as a magmatic-volcanic arc (inner magmatic-volcanic arc) above an east-dipping, but westwardly migrating, subduction zone related to the prolonged plate convergence which occurred during Upper Mesozoic and Cenozoic. The central granitoid belt is characterized by mesozonal, Mostly Upper Cretaceous to Lower Eocene plutons associated with abundant pegmalites and aplites, numerous vein-type W-Sn deposits and rare co-magmatic volcanics. The country rocks are structurally deformed, metamorphic rocks of greenschist to upper amphibolite facies ranging in age as early as Upper Precambrian to Upper Paleozoic and locally of fossiliferous, metaclastic rocks (Mid Jurassic to Lower Cretaceous). Available K/Ar radiometric data indicate significant and possibly widespread thermal disturbances in the central granitoid belt during the Tertiary (mostly Miocence). In this study, the distribution, lithological, textural and structural characteristics of the central belt granitoids are reviewed, and their mineralogical, petrological, and geochemical features are presented. A brief description of W-Sn ore veins associated with these granitoid plutons is also reported. Present geological, petrological and geochemical evidences demonstrate that the W-Sn related, central belt granitoids are mostly granodiorite and granite which are commonly transformed into granitoid gneisses. These central belt granitoids were formed from a calc-alkaline magma derived from a source of continental, sialic materials. Highly potassiccharacters and high initial Sr 87/Sr 86 ratios (0.717±0.002) and Rb/Sr ratios (0.40-33.10) with an average value of 6.70, further corroborate their derivation from a well established continental, sialic basement. Although future chemical and isotopic investigations would be desirable, none of the present evidence argues the interpretation that the granitoid magma was generated by the re-melting of the regionally metamorphosed country rocks. The close association of W-Sn bearing quartz veins and the granitoid rocks also suggests that the metals were derived from the same crustal sources as their host granitoids. The central belt granitoids are considered to have been emplaced during the continent-arc collision of inferred Upper Triassic-Jurassic magmatic-volcanic arc with the continental foreland to the east at the early stage of westward migration of the east-dipping subduction zone to the west. The W-Sn related, central belt granitoids of Upper Mesozoic-Lower Eocene are notably different from those of mainly Triassic granitoids from northern Thailand and Permo-Triassic granites of the Malay Peninsula, and thus the central belt granitoids were emplaced in a uniquely distinct geologic and tetonic setting in the SE Asian region. Major element data for the central belt granitoids, which are associated with W-Sn mineralization lie within the field of Sn-mineralizing granites from New England in Na-K-Ca plot (Juniper and Kleeman, J. Geochem. Explor.11, 321-333, 1979), but largely outside the field on SiO 2CaO +_MgO + FeONa 2O + K 2O + Al 2O 3 plot. Trace element abundances of the central belt granitoid rocks suggest that the Sn content of the granitoids alone should be used with great caution to discriminate the W-Sn bearing (mineralized) granitoid plutons from the W-Sn poor (barren) plutons in search for the W-Sn deposits in Burma, but trace element data show the tendency for granitoid plutons which bear W-Sn mineralization to be comparatively more enriched in Be, Bi, Cu, Mo, Pb, Sn, Y, and Zn, but less depleted in Ba and Zr than those plutons in which no W-Sn occurrences are recorded. The eastern belt granitoids are still largely unknown but characterized by medium to coarsely porphyritic textures and country rocks of regionally metamorphosed, turbiditic sediments of Chaung Magyi Group (Upper Precambrian). This eastern granitoid belt lies immediately to the north of mostly Triassic granitoids in northern Thailand, and the Sn-W bearing, mesozonal, Permo-Triassic, Main Range granitoids in the western part of the Malay Peninsula. The latter granitoid swere considered to have been emplaced during continental collision, but geologic and tectonic information for the eastern belt grantoids in Burma are still incomplete to confirm this contention. Alternatively, present available geologic evidences cannot rule out the possibility that the eastern belt granitoids were emplaced in a continental margin above an eastward subducting ocean floor during the Lower Paleozoic. According to the criteria given by Chappell and White ( Pacific Geol.8, 173-174, 1974), the porphyry Cu(Au)-related, western granitoid belt plutons have I-type characteristics, whereas the W-Sn related, central granitoid belt contains both the hornblende-bearing I-type granitoids as older intrusive phases and the W-Sn bearing, S-type granitoids as younger plutonic phases. The eastern belt granitoids cannot be classified as being of either I- or S-type, as petrochemical data are still lacking.

Geology and Mineral Deposits of the Snow Camp-Saxapahaw Area, Central North Carolina

USGS Publications Warehouse

Schmidt, Robert G.; Gumiel, Pablo; Payas, Alba

2006-01-01

The Snow Camp-Saxapahaw study area, in the Carolina slate belt in the Southeastern United States, is notable for large zones of high-sulfidation alteration in arc-related metavolcanic rocks. The area has potential for additional significant pyrophyllite and related aluminosilicate refractory mineral deposits and may have potential for small- to medium-size gold deposits also associated with the high-sulfidation hydrothermal systems. The Carolina slate belt is an elongate zone of mostly low-grade metamorphic rocks of Neoproterozoic to early Paleozoic age that extends from northeastern Georgia to southern Virginia. It is dominated by volcanic rocks but locally consists of fine-grained epiclastic sedimentary rocks. Plutons and subvolcanic bodies have intruded the rocks of the Carolina slate belt in many places and have been important in controlling the metamorphism and in localizing hydrothermal alteration. The Snow Camp-Saxapahaw area is mostly underlain by volcanic and volcaniclastic rocks and lesser amounts of intrusive shallow plutons. The volcanic rocks range in composition from basalt to rhyolite; however andesites, dacites, and rhyodacites are the most abundant. The intrusive bodies are largely granite and quartz monzonite; gabbroic bodies also are common. It was possible to establish the relative ages of only part of these rocks. Two northeast-trending fault zones and fractures divide the map area into three structural blocks; the central block was tilted down to the southwest to form a grabenlike structure. Most of the hydrothermally altered rocks and all of the intensely altered zones are confined to the downdropped block, which we think may have been calderalike in origin. A major volcanic unit, the Reedy Branch Tuff, is limited to the southwestern part of the graben and may be the youngest volcanic rock in the area. Layered rocks record one or more strong folding events, but the diversity of rock types, lack of recognizable stratigraphic markers, and uneven distribution of outcrops prevented comprehensive structural studies. Except for a few late plutons and dikes, all of the rocks of the area have been metamorphosed in middle to upper greenschist facies, and contact aureoles were recognized around some of the plutons. Several relatively small bodies of granitic rock contain plagioclase grains in which primary oscillatory zoning was unaffected by metamorphism. These were interpreted to be post-metamorphic. We think that there were three separate stages of hydrothermal alteration in the complex volcanic terrane in the area. The oldest, an area of at least 8.5 square miles (22 square kilometers), was subjected to an intense hydrothermal alteration, ranging from peripheral zones of quartz-sericite-paragonite through a patchy marginal zone of pyrophyllite, andalusite, and other high-alumina minerals, to almost totally silicified core zones. The second event resulted in large areas of weak to moderate sericitic and propylitic alteration recognizable only in the Reedy Branch Tuff. The last event was related to post-metamorphic plutons. All of the pyrophyllite-andalusite deposits and perhaps most of the gold and silver mineralization can be related to the first period of hydrothermal alteration. The subsequent metamorphism did not produce significant changes in mineral species in the zones of most intense hydrothermal alteration. Gold- and silver-bearing sulfide minerals in fracture zones along the southeastern margin of the graben may also have been deposited during this earliest alteration stage. No metallic mineralization appears to have occurred during the second event. A group of molybdenum-bearing greisenlike bodies formed during the emplacement of the youngest plutons during the post-metamorphic event. One gold-bearing sulfide zone occurs in the exocontact of one such porphyritic stock. Significant amounts of pyrophyllite-andalusite-bearing rock have been extracted from the Snow Camp Mine and from

Spatial data for Eurycea salamander habitats associated With three aquifers in south-central Texas

USGS Publications Warehouse

Heitmuller, Franklin T.; Reece, Brian D.

2006-01-01

Eurycea salamander taxa comprise 12 known species that inhabit springs and caves in south-central Texas. Many of these are threatened or endangered species, and some are found only at one location. A number of the neotenic salamanders might be at risk from habitat loss associated with declines in ground-water levels. Eurycea salamander habitats are associated with three aquifers in south-central Texas: (1) the Edwards-Trinity (Plateau) aquifer, (2) the Edwards (Balcones Fault Zone) aquifer, and (3) the Trinity aquifer. The Edwards (Balcones fault zone) aquifer is commonly separated into three segments: from southwest to northeast, the San Antonio segment, the Barton Springs segment, and the northern segment. The Trinity aquifer south of the Colorado River can be divided into three permeable zones, the upper, middle, and lower zone. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, developed this report (geodatabase) to aggregate the spatial data necessary to assess the potential effects of ground-water declines on known Eurycea habitat locations in south-central Texas. The geodatabase provides information about spring habitats, spring flow, cave habitats, aquifers, and projected water levels.

Time domain reflectometry measurements of solute transport across a soil layer boundary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nissen, H.H.; Moldrup, P.; Kachanoski, R.G.

2000-02-01

The mechanisms governing solute transport through layered soil are not fully understood. Solute transport at, above, and beyond the interface between two soil layers during quasi-steady-state soil water movement was investigated using time domain reflectometry (TDR). A 0.26-m sandy loam layer was packed on top of a 1.35-m fine sand layer in a soil column. Soil water content ({theta}) and bulk soil electrical conductivity (EC{sub b}) were measured by 50 horizontal and 2 vertical TDR probes. A new TDR calibration method that gives a detailed relationship between apparent relative dielectric permittivity (K{sub s}) and {theta} was applied. Two replicate solutemore » transport experiments were conducted adding a conservative tracer (CCl) to the surface as a short pulse. The convective lognormal transfer function model (CLT) was fitted to the TDR-measured time integral-normalized resident concentration breakthrough curves (BTCs). The BTCs and the average solute-transport velocities showed preferential flow occurred across the layer boundary. A nonlinear decrease in TDR-measured {theta} in the upper soil toward the soil layer boundary suggests the existence of a 0.10-m zone where water is confined towards fingered flow, creating lateral variations in the area-averaged water flux above the layer boundary. A comparison of the time integral-normalized flux concentration measured by vertical and horizontal TDR probes at the layer boundary also indicates a nonuniform solute transport. The solute dispersivity remained constant in the upper soil layer, but increased nonlinearly (and further down, linearly) with depth in the lower layer, implying convective-dispersive solute transport in the upper soil, a transition zone just below the boundary, and stochastic-convective solute transport in the remaining part of the lower soil.« less

The Galicia-Ossa-Morena Zone: Proposal for a new zone of the Iberian Massif. Variscan implications

NASA Astrophysics Data System (ADS)

Arenas, Ricardo; Díez Fernández, Rubén; Rubio Pascual, Francisco J.; Sánchez Martínez, Sonia; Martín Parra, Luis Miguel; Matas, Jerónimo; González del Tánago, José; Jiménez-Díaz, Alberto; Fuenlabrada, Jose M.; Andonaegui, Pilar; Garcia-Casco, Antonio

2016-06-01

Correlation of a group of allochthonous terranes (referred to as basal, ophiolitic and upper units) exposed in the NW and SW of the Iberian Massif, is used to propose a new geotectonic zone in the southern branch of the Variscan Orogen: the Galicia-Ossa-Morena Zone. Recent advances in SW Iberia identify most of the former Ossa-Morena Zone as another allochthonous complex of the Iberian Massif, the Ossa-Morena Complex, equivalent to the Cabo Ortegal, Órdenes, Malpica-Tui, Bragança and Morais complexes described in NW Iberia. The new geotectonic zone and its counterparts along the rest of the Variscan Orogen constitute an Internal Variscan Zone with ophiolites and units affected by high-P metamorphism. The Galicia-Ossa-Morena Zone includes a Variscan suture and pieces of continental crust bearing the imprint of Ediacaran-Cambrian events related to the activity of peri-Gondwanan magmatic arcs (Cadomian orogenesis). In the Iberian Massif, the general structure of this geotectonic zone represents a duplication of the Gondwanan platform, the outboard sections being juxtaposed on top of domains located closer to the mainland before amalgamation. This interpretation offers an explanation that overcomes some issues regarding the differences between the stratigraphic and paleontological record of the central and southern sections of the Iberian Massif. Also, equivalent structural relationships between other major geotectonic domains of the rest of the Variscan Orogen are consistent with our interpretation and allow suspecting similar configurations along strike of the orogen. A number of issues may be put forward in this respect that potentially open new lines of thinking about the architecture of the Variscan Orogen.

Carbon Mobility at Subduction Interfaces via Deformation-Enhanced Fluid Infiltration: Evidence from the Swiss/Italian Alps

NASA Astrophysics Data System (ADS)

Jaeckel, K. P.; Bebout, G. E.; Angiboust, S.

2016-12-01

The interplay between fluid flow and deformation along subduction interfaces, and the extent to which deformation-enhanced fluid infiltration can drive decarbonation and carbonate dissolution, remain poorly understood. Recent work on HP/UHP decarbonation in W. Alps suites has indicated that, in intact volumes of metasediment, metabasalt, and ophicarbonate away from major shear zones and with few veins, carbonate is largely retained to 80-90 km depths (Cook-Kollars et al., 2014; Collins et al., 2015; Chem. Geol.). Yet uncertain is whether forearc fluid infiltration focused in intensely sheared and fractured zones could result in greater mobilization of C from subducting sections, in quantities sufficient to impact subduction zone C cycling. Lower-plate rocks at Arosa and Dent Blanche interface exposures (Bachmann et al., 2009, JGR; Angiboust et al., 2015, G3) are primarily calc-schist intercalated with meta-ultramafic and metamafic schist and contain carbonate-bearing veins of varying abundance and texture. At some localities, these sections contain blocks of carbonate, metabasalt, and upper-plate gneiss. Strongly deformed veins concordant with the foliation parallel to the thrust interface commonly contain carbonate and quartz. In highly sheared regions in the Arosa Zone, δ18O(VSMOW) values of some host-rocks and veins are shifted from +20 ± 2‰, values observed regionally for the Schistes Lustres, to values of +11 to +13‰. These shifts can be explained by interaction with externally-derived H2O-rich fluids with δ18O of +9 to +11‰. Smaller datasets for Dent Blanche localities hint at similar δ18O shifts. Most of these rocks contain little evidence of C release by decarbonation reactions. Evidence exists for local-scale dissolution of carbonate, during pressure solution, and carbonate-bearing veins reflect C mobility in fluids. Ongoing work assesses whether volumes of carbonate removed in some regions balance with those precipitated nearby in veins and pressure shadows.

Assessment of the hydrogeology and water quality in a near-shore well field, Sarasota, Florida

USGS Publications Warehouse

Broska, J.C.; Knochenmus, L.A.

1996-01-01

The city of Sarasota, Florida, operates a downtown well field that pumps mineralized water from ground water sources to supply a reverse osmosis plant. Because of the close proximity of the well field to Sarasota Bay and the high sulfate and chloride concentrations of ground-water supplies, a growing concern exists about the possibility of lateral movement of saltwater in a landward direction (intrusion) and vertical movement of relict sea water (upconing). In 1992, the U.S. Geological Survey began a 3-year study to evaluate the hydraulic characteristics and water quality of ground-water resources within the downtown well field and the surrounding 235-square-mile study area. Delineation of the hydrogeology of the study area was based on water- quality data, aquifer test data, and extensive borehole geophysical surveys (including gamma, caliper, temperature, electrical resistivity, and flow meter logs) from the six existing production wells and from a corehole drilled as part of the study, as well as from published and unpublished reports on file at the U.S. Geological Survey, the Southwest Florida Water Management District, and consultant's reports. Water-quality data were examined for spatial and temporal trends that might relate to the mechanism for observed water-quality changes. Water quality in the study area appears to be dependent upon several mechanisms, including upconing of higher salinity water from deeper zones within the aquifer system, interbore-hole flow between zones of varying water quality through improperly cased and corroded wells, migration of highly mineralized waters through structural deformities, and the presence of unflushed relict seawater. A numerical ground-water flow model was developed as an interpretative tool where field-derived hydrologic characteristics could be tested. The conceptual model consisted of seven layers to represent the multilayered aquifer systems underlying the study area. Particle tracking was utilized to delineate the travel path of water as it enters the model area under a set of given conditions. Within the model area, simulated flow in the intermediate aquifer system originates primarily from the northwestern boundary. Simulated flow in the Upper Floridan aquifer originates in lower model layers (deeper flow zones) and ultimately can be traced to the southeastern and northwestern boundaries. Volumetric budgets calculated from numerical simulation of a hypothetical well field indicate that the area of contribution to the well field changes seasonally. Although ground-water flow patterns change with wet and dry seasons, most water enters the well-field flow system through lower parts of the Upper Floridan aquifer from a southeastern direction. Moreover, particle tracking indicated that ground-water flow paths with strictly lateral pathlines in model layers correspond to the intermediate aquifer system, whereas particles traced through model layers corresponding to the Upper Floridan aquifer had components of vertical and lateral flow.

Niche partitioning of marine group I Crenarchaeota in the euphotic and upper mesopelagic zones of the East China Sea.

PubMed

Hu, Anyi; Jiao, Nianzhi; Zhang, Rui; Yang, Zao

2011-11-01

Marine group I Crenarchaeota (MGI) represents a ubiquitous and numerically predominant microbial population in marine environments. An understanding of the spatial dynamics of MGI and its controlling mechanisms is essential for an understanding of the role of MGI in energy and element cycling in the ocean. In the present study, we investigated the diversity and abundance of MGI in the East China Sea (ECS) by analysis of crenarchaeal 16S rRNA gene, the ammonia monooxygenase gene amoA, and the biotin carboxylase gene accA. Quantitative PCR analyses revealed that these genes were higher in abundance in the mesopelagic than in the euphotic zone. In addition, the crenarchaeal amoA gene was positively correlated with the copy number of the MGI 16S rRNA gene, suggesting that most of the MGI in the ECS are nitrifiers. Furthermore, the ratios of crenarchaeal accA to amoA or to MGI 16S rRNA genes increased from the euphotic to the mesopelagic zone, suggesting that the role of MGI in carbon cycling may change from the epipelagic to the mesopelagic zones. Denaturing gradient gel electrophoretic profiling of the 16S rRNA genes revealed depth partitioning in MGI community structures. Clone libraries of the crenarchaeal amoA and accA genes showed both "shallow" and "deep" groups, and their relative abundances varied in the water column. Ecotype simulation analysis revealed that MGI in the upper ocean could diverge into special ecotypes associated with depth to adapt to the light gradient across the water column. Overall, our results showed niche partitioning of the MGI population and suggested a shift in their ecological functions between the euphotic and mesopelagic zones of the ECS.

Partitioning of H2O on high pressure phase transformation of olivine

NASA Astrophysics Data System (ADS)

Inoue, T.; Wada, T.; Sasaki, R.; Irifune, T.; Yurimoto, H.

2003-12-01

Water is the most abundant volatile component on the Earth's surface, and it has been supplied to the Earth's interiors by subducted slab. Water influences the physical properties and melting temperature of minerals. Olivine is the most abundant mineral in the mantle, and it is clarified that the high-pressure polymorphs of olivine, wadsleyite and ringwoodite, can contain 3wt% of H2O in their crystal structures (e.g. Inoue et al., 1995, 1998). However, the partitioning of H2O among these minerals has not been clarified yet except for olivine-wadsleyite transformation (Chen et al., 2003). We have determined the partitioning of H2O between wadsleyite and ringwoodite and between ringwoodite and perovskite, and clarified the distribution of H2O among upper mantle, mantle transition zone and lower mantle. High-pressure experiments were conducted by MA-8 type (Kawai-type) high-pressure apparatus in Ehime University, and the chemical compositions were determined by EPMA. The water contents of minerals were measured by SIMS in Tokyo Institute of Technology. We succeeded to synthesize large (approximately 50 μ m) coexisting crystals of wadsleyite and ringwoodite, and of ringwoodite and perovskite, and we could clarify the partitioning of H2O between those coexisting minerals. The partition coefficients between wadsleyite and ringwoodite and between ringwoodite and perovskite were about 2 and about 10 or more, respectively. We (Chen et al., 2003) have already determined that the partition coefficients between wadsleyite and olivine is about 5, so the partitioning among upper mantle, 410-520km and 520-660km of mantle transition zone, and lower mantle are 4:20:10:1. Thus the mantle transition zone should be a strong water reservoir in the Earth's interiors.

Differential Distributions of Synechococcus Subgroups Across the California Current System

PubMed Central

Paerl, Ryan W.; Johnson, Kenneth S.; Welsh, Rory M.; Worden, Alexandra Z.; Chavez, Francisco P.; Zehr, Jonathan P.

2011-01-01

Synechococcus is an abundant marine cyanobacterial genus composed of different populations that vary physiologically. Synechococcus narB gene sequences (encoding for nitrate reductase in cyanobacteria) obtained previously from isolates and the environment (e.g., North Pacific Gyre Station ALOHA, Hawaii or Monterey Bay, CA, USA) were used to develop quantitative PCR (qPCR) assays. These qPCR assays were used to quantify populations from specific narB phylogenetic clades across the California Current System (CCS), a region composed of dynamic zones between a coastal-upwelling zone and the oligotrophic Pacific Ocean. Targeted populations (narB subgroups) had different biogeographic patterns across the CCS, which appear to be driven by environmental conditions. Subgroups C_C1, D_C1, and D_C2 were abundant in coastal-upwelling to coastal-transition zone waters with relatively high to intermediate ammonium, nitrate, and chl. a concentrations. Subgroups A_C1 and F_C1 were most abundant in coastal-transition zone waters with intermediate nutrient concentrations. E_O1 and G_O1 were most abundant at different depths of oligotrophic open-ocean waters (either in the upper mixed layer or just below). E_O1, A_C1, and F_C1 distributions differed from other narB subgroups and likely possess unique ecologies enabling them to be most abundant in waters between coastal and open-ocean waters. Different CCS zones possessed distinct Synechococcus communities. Core California current water possessed low numbers of narB subgroups relative to counted Synechococcus cells, and coastal-transition waters contained high abundances of Synechococcus cells and total number of narB subgroups. The presented biogeographic data provides insight on the distributions and ecologies of Synechococcus present in an eastern boundary current system. PMID:21833315

Biostratigraphy and paleoecology of the Burdigalian-Serravallian sediments in Wadi Sudr (Gulf of Suez, Egypt): comparison with the Central Paratethys evolution

NASA Astrophysics Data System (ADS)

Ied, Ibrahim M.; Holcová, Katarína; Abd-Elshafy, Ezzat

2011-06-01

Two main Miocene facies were recorded in the Gulf of Suez area: a deep marine and a coastal facies. The analysed sections in the Wadi Sudr area belong to the marine facies. The Lower Miocene (Burdigalian) is represented by coastal, shallow marine sediments, rich in coral, algae, gastropods and large pectinids followed by Langhian open marine sediments and Serravallian lagoonal carbonates. The open marine sediments contain well preserved planktonic and benthic foraminifers and abundant ostracods. The parts of the sections containing foraminifers have been correlated with three planktonic foraminiferal zones (Praeorbulina glomerosa Zone, Orbulina Zone and Globorotalia praemenardii-Globorotalia peripheroronda Zone). Two benthic ecozones were defined (Heterolepa dutemplei-Laevidentalina elegans Zone and Bolivina compressa-Elphidium spp. Zone). Two cycles of sea-level changes can be distinguished and correlated with global sea-level cycles Bur5/Lan1 and Ser1. The first (Langhian) cycle culminated in open marine sublittoral to upper bathyal well aerated sediments. The second (Serravallian) cycle was shallower, littoral suboxic sediments were overlaid by euryhaline carbonates. The studied foraminifera-bearing sediments can be correlated with the lower and Middle Badenian of the Central Paratethys. Though the area of the Gulf of Suez and the Central Paratethys were situated in different climatic zones, and influenced by different tectonic events, the main paleoenvironmental events (sea-level changes, oxygen decrease, salinity changes) are comparable. This correspondence shows that the decisive factors triggering these events were global climatic events.

Simulated effects of groundwater withdrawals from aquifers in Ocean County and vicinity, New Jersey

USGS Publications Warehouse

Cauller, Stephen J.; Voronin, Lois M.; Chepiga, Mary M.

2016-10-21

Rapid population growth since the 1930s in Ocean County and vicinity, New Jersey, has placed increasing demands upon the area’s freshwater resources. To examine effects of groundwater withdrawals, a three-dimensional groundwater-flow model was developed to simulate the groundwater-flow systems of five area aquifers: the unconfined Kirkwood-Cohansey aquifer system and Vincentown aquifer, and three confined aquifers— the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, and the Piney Point aquifer. The influence of withdrawals is evaluated by using transient groundwater-flow model simulations that incorporate three withdrawal schemes. These are (1) no-withdrawal conditions; (2) 2000–03 withdrawal conditions, using reported monthly withdrawals at all production wells from January 2000 through December 2003; and (3) maximum-allocation withdrawal conditions using the maximum withdrawal allowed by New Jersey Department of Environmental Protection permits at each well. Particle tracking analysis, using results from model simulations, delineated particle flow paths from production wells to the point of recharge, and estimated particle travel times.Compared with no-withdrawal conditions, 2000–03 withdrawal conditions reduced the amount of groundwater flow out of the Kirkwood-Cohansey aquifer system into streams, increased the net flow of water into other layers, reduced net flow into or out of storage, and reduced flow from the Kirkwood-Cohansey aquifer system to constant head cells.Freshwater discharging to the Barnegat Bay-Little Egg Harbor estuary from streams and groundwater is essential to maintaining the ecology of the bay. Examination of selected stress periods indicates that simulated base flow in streams flowing into the Barnegat Bay-Little Egg Harbor estuary is reduced by as much as 49 cubic feet per second for 2000 to 2003 withdrawal conditions when compared with no-withdrawal conditions.In the three confined aquifers, water levels during periods of low recharge and high withdrawals, and high recharge and low withdrawals, were examined to determine seasonal effects on the confined flow systems. The simulated potentiometric surface of the Rio Grande water-bearing zone and the Atlantic City 800-foot sand during selected stress periods indicates substantial declines from no-withdrawal conditions to 2000–03 conditions as a result of groundwater withdrawals. Cones of depression in Toms River Township, Seaside Heights and Seaside Park Boroughs, and Barnegat Light Borough developed in the potentiometric surface of the Piney Point aquifer in response to withdrawals.Maximum-allocation withdrawals decreased flow out of the Kirkwood-Cohansey aquifer system to constant head cells, increased flow out of the aquifer system to adjacent and lower layers, and reduced groundwater discharge to streams when compared with 2000–03 withdrawal conditions. Increases in withdrawals from the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, and the Piney Point aquifer result in an increase in simulated net groundwater flow into these aquifers. Base-flow reduction from 2000–03 conditions to maximum-allocation conditions of 25 to 29 cubic feet per second in all streams draining to the Barnegat Bay-Little Egg Harbor also is indicated. Potentiometric surfaces of the Rio Grande water-bearing zone, Atlantic City 800-foot sand, and the Piney Point aquifer during two stress periods of simulated maximum-allocation withdrawal conditions indicated the expansion of several cones of depression developed during 2000–03 withdrawals.Simulation of average 2000–03 withdrawal conditions indicated the extent to which the groundwater-flow system is susceptible to potential saltwater intrusion into near-shore wells. Travel time from recharge to discharge location ranged from 11 to approximately 50,700 years in near-shore Kirkwood-Cohansey aquifer system wells. Those in Seaside Heights Borough, in Island Beach State Park (Berkeley Township), and in Ship Bottom Borough have particle travel times from 140 to 12,000 years and flow paths that originated under Barnegat Bay or the Atlantic Ocean from the simulation of average maximum-allocation withdrawal conditions.Travel time along flow paths to wells screened in the Rio Grande water-bearing zone and the Atlantic City 800-foot sand from recharge to discharge point ranged from nearly 530 years to greater than 3.73 million years from the simulation of average 2000–03 withdrawal conditions. Particle tracking indicated that most wells screened in these aquifers derived a large part of their recharge from the Oswego River Basin, with a small portion of flow originating either beneath Barnegat Bay or to the east beneath the Atlantic Ocean. Travel time along flow paths that start beneath either Barnegat Bay or the Atlantic Ocean ranged from 2,300 to approximately 134,000 years from the simulation of average maximum-allocation withdrawal conditions."

BOREAS TF-4 CO2 and CH4 Soil Profile Data from the SSA

NASA Technical Reports Server (NTRS)

Striegl, Robert; Wickland, Kimberly; Hall, Forrest G. (Editor); Conrad, Sara (Editor)

2000-01-01

The BOReal Ecosystem-Atmosphere Study Tower Flux (BOREAS TF-4) team measured distributions of carbon dioxide (CO2) and methane (CH4) concentrations for the upper 5 m of soil and unsaturated zone at the mature stand, upper 6 m at the 20-year-old stand, and the upper 1 m at the 8-year-old stand and clear cut area at the BOREAS Southern Study Area (SSA) during August 1993 to March 1995. Particle size and carbon content of the unsaturated deposits, precipitation, soil temperature and moisture, carbon and oxygen isotopes of soil CO2, and soil water chemistry are also presented. The data are stored in tabular ASCII files.

Geohydrology and water quality of the Inyan Kara, Minnelusa, and Madison aquifers of the northern Black Hills, South Dakota and Wyoming, and Bear Lodge Mountains, Wyoming

USGS Publications Warehouse

Kyllonen, D.P.; Peter, K.D.

1987-01-01

The Inyan Kara, Minnelusa, and Madison aquifers are the principal sources of ground water in the northern Black Hills, South Dakota and Wyoming, and Bear Lodge Mountains, Wyoming. The aquifers are exposed in the Bear Lodge Mountains and the Black Hills and are about 3,000 to 5,000 ft below the land surface in the northeast corner of the study area. The direction of groundwater movement is from the outcrop area toward central South Dakota. Recharge is by infiltration of precipitation and streamflow is by springs and well withdrawals. All three aquifers yield water to flowing wells in some part of the area. Measured and reported well yields in each of the three aquifers exceed 100 gal/min (gpm). A well open to the Minnelusa Formation and the upper part of the Madison Limestone yielded more than 2 ,000 gpm. Water from the Inyan Kara aquifer may require treatment for gross alpha radiation, iron, manganese, sulfate, and hardness before use in public water systems. Water from the Minnelusa aquifer in the northern one-half of the study area may require treatment for sulfate and hardness before use in public water systems. Water from the Madison aquifer in the northern one-half of the study area may require treatment of fluoride, gross alpha radiation, sulfate, and hardness before use in public water systems. Water from the Minnelusa and Madison aquifers in the southern one-half of the study area, though very hard (more than 180 mg/L hardness as calcium carbonate), is suitable for public water systems and irrigation. Flow between the Minnelusa and the Inyan Kara aquifers appears to be insignificant, based on the results of a digital model results. The model indicated there may be significant recharge to the Minnelusa and Madison aquifers by leakage between these two aquifers and perhaps deeper aquifers. (Author 's abstract)

Simulated effects of alternative withdrawal strategies on groundwater flow in the unconfined Kirkwood-Cohansey aquifer system, the Rio Grande water-bearing zone, and the Atlantic City 800-foot sand in the Great Egg Harbor and Mullica River Basins, New Jersey

USGS Publications Warehouse

Pope, Daryll A.; Carleton, Glen B.; Buxton, Debra E.; Walker, Richard L.; Shourds, Jennifer L.; Reilly, Pamela A.

2012-01-01

Groundwater is essential for water supply and plays a critical role in maintaining the environmental health of freshwater and estuarine ecosystems in the Atlantic Coastal basins of New Jersey. The unconfined Kirkwood-Cohansey aquifer system and the confined Atlantic City 800-foot sand are major sources of groundwater in the area, and each faces different water-supply concerns. The U.S. Geological Survey (USGS), in cooperation with the New Jersey Department of Environmental Protection (NJDEP), conducted a study to simulate the effects of withdrawals in the Kirkwood-Cohansey aquifer system, the Atlantic City 800-foot sand, and the Rio Grande water-bearing zone and to evaluate potential scenarios. The study area encompasses Atlantic County and parts of Burlington, Camden, Gloucester, Ocean, Cape May, and Cumberland Counties. The major hydrogeologic units affecting water supply in the study area are the surficial Kirkwood-Cohansey aquifer system, a thick diatomaceous clay confining unit in the upper part of Kirkwood Formation; the Rio Grande water-bearing zone; and the Atlantic City 800-foot sand of the Kirkwood Formation. Hydrogeologic data from 18 aquifer tests and specific capacity data from 230 wells were analyzed to provide horizontal hydraulic conductivity of the aquifers. Groundwater withdrawals are greatest from the Kirkwood-Cohansey aquifer system, and 65 percent of the water is used for public supply. Groundwater withdrawals from the Atlantic City 800-foot sand are about half those from the Kirkwood-Cohansey aquifer system. Ninety-five percent of the withdrawals from the Atlantic City 800-foot sand is used for public supply. Data from six streamgaging stations and 51 low-flow partial record sites were used to estimate base flow in the area. Base flow ranges from 60 to 92 percent of streamflow. A groundwater flow model of the Kirkwood-Cohansey aquifer system, the Rio Grande water-bearing zone, and the Atlantic City 800-foot sand was developed and calibrated using water-level data from 148 wells and base-flow data from 22 gaging or low-flow partial record stations. The Kirkwood-Cohansey aquifer system within the Great Egg Harbor River and the Mullica River Basins was simulated on a monthly basis from 1998 through 2006. An existing regional model of the New Jersey Coastal Plain was revised to provide boundary conditions for the Great Egg Harbor and Mullica River Basin model (referred to as the Great Egg-Mullica model). In the Great Egg-Mullica model, monthly groundwater recharge rates used in the model ranged from 10-15 inches per year in 2001 to 20-25 inches per year in 2005. The mean-absolute error for 10 of the 14 long-term hydrographs used in model calibration was less than 5 ft. Groundwater flow budgets for the Great Egg-Mullica model calibration periods, May 2005 and September 2006, and for the entire model calibration period 1998 to 2006, showed that nearly 70 percent of the water entering the Atlantic City 800-foot sand came from the horizontal connection with the Kirkwood-Cohansey aquifer system in updip areas. The groundwater flow model was used to simulate scenarios under three possible conditions: average 1998 to 2006 withdrawals (Average scenario), full-allocation withdrawals (Full Allocation scenario), and projected 2050-demand withdrawals (2050 Demand scenario). Withdrawals in the Full Allocation scenario are nearly twice the withdrawals from the Average scenario, primarily because of the potential for large agricultural withdrawals if all allocations are used. Withdrawals for the 2050 Demand scenario are about 50 percent greater than those for the Average scenario, primarily due to expected increases in withdrawals for public supply. Monthly base-flow depletion criteria were determined using the Low-Flow Margin method, currently under consideration by NJDEP, to estimate available water on an annual basis at the Hydrologic Unit Code 11 (HUC11) level and to determine whether a water-supply deficit exists. Simulations of various groundwater-withdrawal scenarios were made using the calibrated model, and results were compared with baseline conditions (no withdrawals) to determine where and when base-flow deficits may be occurring and may be expected to occur in the future. Scenarios were simulated to assess base-flow depletion that could occur from different groundwater-withdrawal situations. In the Average scenario, deficits occurred in 7 of the 14 subbasins. In the Full Allocation scenario, deficits occurred in 11 of the subbasins. In the 2050 Demand scenario, deficits occurred in 9 of the 14 subbasins. The largest deficits occurred in the Absecon Creek subbasin because the base-flow depletion criteria for this subbasin is small due to the surface-water diversions that are already occurring there and because existing groundwater withdrawals in the subbasin have resulted in base-flow depletion under current (1998-2006) conditions. Three adjusted scenarios, variations of the Average, Full Allocation, and 2050 Demand scenarios, were simulated; for the adjusted scenarios, the withdrawals were modified in stages with the intent to successively eliminate or minimize the base-flow deficits. Modifications included shifting withdrawals to a deeper part of the Kirkwood-Cohansey aquifer system, implementing seasonal conjunctive use of shallow and deep aquifers, and specifying reductions in withdrawals within a HUC11 subbasin in deficit. The adjusted scenarios are intended to show the relative effectiveness of each of the three approaches in reducing the deficits. Most of the deficits under the Average, Full Allocation, and 2050 Demand scenarios were eliminated by reductions in withdrawals or allocations. Shifting withdrawals to a deeper part of the Kirkwood-Cohansey aquifer system or seasonal conjunctive use did not eliminate deficits for any subbasin. Reductions in withdrawals accounted for more than 95 percent of the total reduction of deficits in all but one subbasin.

Physical-Biological Coupling in the Western South China Sea: The Response of Phytoplankton Community to a Mesoscale Cyclonic Eddy

PubMed Central

Wang, Lei; Huang, Bangqin; Chiang, Kuo-Ping; Liu, Xin; Chen, Bingzhang; Xie, Yuyuan; Xu, Yanping; Hu, Jianyu; Dai, Minhan

2016-01-01

It is widely recognized that the mesoscale eddies play an important part in the biogeochemical cycle in ocean ecosystem, especially in the oligotrophic tropical zones. So here a heterogeneous cyclonic eddy in its flourishing stage was detected using remote sensing and in situ biogeochemical observation in the western South China Sea (SCS) in early September, 2007. The high-performance liquid chromatography method was used to identify the photosynthetic pigments. And the CHEMical TAXonomy (CHEMTAX) was applied to calculate the contribution of nine phytoplankton groups to the total chlorophyll a (TChl a) biomass. The deep chlorophyll a maximum layer (DCML) was raised to form a dome structure in the eddy center while there was no distinct enhancement for TChl a biomass. The integrated TChl a concentration in the upper 100 m water column was also constant from the eddy center to the surrounding water outside the eddy. However the TChl a biomass in the surface layer (at 5 m) in the eddy center was promoted 2.6-fold compared to the biomass outside the eddy (p < 0.001). Thus, the slight enhancement of TChl a biomass of euphotic zone integration within the eddy was mainly from the phytoplankton in the upper mixed zone rather than the DCML. The phytoplankton community was primarily contributed by diatoms, prasinophytes, and Synechococcus at the DCML within the eddy, while less was contributed by haptophytes_8 and Prochlorococcus. The TChl a biomass for most of the phytoplankton groups increased at the surface layer in the eddy center under the effect of nutrient pumping. The doming isopycnal within the eddy supplied nutrients gently into the upper mixing layer, and there was remarkable enhancement in phytoplankton biomass at the surface layer with 10.5% TChl a biomass of water column in eddy center and 3.7% at reference stations. So the slight increasing in the water column integrated phytoplankton biomass might be attributed to the stimulated phytoplankton biomass at the surface layer. PMID:27088991

Final Scientific/Technical Report: Characterizing the Response of the Cascadia Margin Gas Hydrate Reservoir to Bottom Water Warming Along the Upper Continental Slope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solomon, Evan A.; Johnson, H. Paul; Salmi, Marie

The objective of this project is to understand the response of the WA margin gas hydrate system to contemporary warming of bottom water along the upper continental slope. Through pre-cruise analysis and modeling of archive and recent geophysical and oceanographic data, we (1) inventoried bottom simulating reflectors along the WA margin and defined the upper limit of gas hydrate stability, (2) refined margin-wide estimates of heat flow and geothermal gradients, (3) characterized decadal scale temporal variations of bottom water temperatures at the upper continental slope of the Washington margin, and (4) used numerical simulations to provide quantitative estimates of howmore » the shallow boundary of methane hydrate stability responds to modern environmental change. These pre-cruise results provided the context for a systematic geophysical and geochemical survey of methane seepage along the upper continental slope from 48° to 46°N during a 10-day field program on the R/V Thompson from October 10-19, 2014. This systematic inventory of methane emissions along this climate-sensitive margin corridor and comprehensive sediment and water column sampling program provided data and samples for Phase 3 of this project that focused on determining fluid and methane sources (deep-source vs. shallow; microbial, thermogenic, gas hydrate dissociation) within the sediment, and how they relate to contemporary intermediate water warming. During the 2014 research expedition, we sampled nine seep sites between ~470 and 520 m water depth, within the zone of predicted methane hydrate retreat over the past 40 years. We imaged 22 bubble plumes with heights commonly rising to ~300 meters below sea level with one reaching near the sea surface. We collected 22 gravity cores and 20 CTD/hydrocasts from the 9 seeps and at background locations (no acoustic evidence of seepage) within the depth interval of predicted downslope retreat of the methane hydrate stability zone. Approximately 300 pore water samples were extracted from the gravity cores, and the pore water was analyzed for a comprehensive suite of solutes, gases, and stable isotope ratios. This comprehensive geochemical dataset was used to characterize the fluid and gas source(s) at each of the seep sites surveyed. The primary results of this project are: 1) Bottom simulating reflector-derived heat flow values decrease from 95 mW/m2 10 km east of the deformation front to ~60 mW/m2 60 km landward of the deformation front, with anomalously low values of ~25 mW/m2 on a prominent mid-margin terrace off central Washington. 2) The temperature of the incoming sediment/ocean crust interface at the deformation front ranges between 164-179 oC off central Washington, and the 350 oC isotherm at the top of the subducting ocean crust occurs 95 km landward of the deformation front. Differences between BSR-derived heat flow and modeled conductive heat flow suggest mean upward fluid flow rates of 0.4 cm/yr across the margin, with local regions (e.g. fault zones) exhibiting fluid flow rates up to 3.5 cm/yr. 3) A compilation of 2122 high-resolution CTD, glider, and Argo float temperature profiles spanning the upper continental slope of the Washington margin from the years 1968 to 2013 show a long-term warming trend that ranges from 0.006-0.008 oC/yr. Based on this long-term bottom water warming, we developed a 2-D thermal model to simulate the change in sediment temperature distribution over this period, along with the downslope retreat of the methane hydrate stability field. Over the 43 years of the simulation, the thermal disturbance propagated 30 m into the sediment column, causing the base of the methane hydrate stability field to shoal ~13 m and to move ~1 km downslope. 4) A preliminary analysis of seafloor observations and mid-water column acoustic data to detect bubble plumes was used to characterize the depth distribution of seeps along the Cascadia margin. These results indicate high bubble plume densities along the continental shelf at water depths <180 m and at the upper limit of methane hydrate stability along the Washington margin. 5) The majority of the seeps cored during the 2014 research expedition on the R/V Thompson contained abundant authigenic carbonate indicating that they are locations of long-lived seepage rather than emergent seep systems related to methane hydrate dissociation. Despite the evidence for enhanced methane seepage at the upper limit of methane hydrate stability along the Washington margin, we found no unequivocal evidence for active methane hydrate dissociation as a source of fluid and gas at the seeps surveyed. The pore fluid and bottom water chemistry shows that the seeps are fed by a variety of fluid and methane sources, but that methane hydrate dissociation, if occurring, is not widespread and is only a minor source (below the detection limit of our methods). Collectively, these results provide a significant advance in our understanding of the thermal structure of the Cascadia subduction zone and the fluid and methane sources feeding seeps along the upper continental slope of the Washington-sector of the Cascadia margin. Though we did not find unequivocal evidence for methane hydrate dissociation as a source of water and methane at the upper pressure-temperature limit of methane hydrate stability at present, continued warming of North Pacific Intermediate Water in the future has the potential to impact the methane hydrate reservoir in sediments at greater depths along the slope. Thus, this study provides a strong foundation and the necessary characterization of the background state of seepage at the upper limit of methane hydrate stability for future investigations of this important process.« less

ARSENIC IN DRINKING WATER SUPPLY WELLS: A MULTI ...

EPA Pesticide Factsheets

Studies have indicated that arsenic concentrations greater than the new U.S. Environmental Protection Agency (EPA) maximum contaminant level (MCL) concentration of 10 micrograms per liter (µg/L) occur in numerous aquifers around the United States. One such aquifer is the Central Oklahoma aquifer, which supplies drinking water to numerous communities in central Oklahoma. Concentrations as high as 230 µg/L have been reported in some drinking water supply wells from this aquifer. The city of Norman, like most other affected cities, is actively seeking a cost-effective solution to the arsenic problem. Only six of the city’s 32 wells exceeded the old MCL of 50 µg/L. With implementation of the new MCL this year, 18 of the 32 wells exceed the allowable concentration of arsenic. Arsenic-bearing shaly sandstones appear to be the source of the arsenic. It may be possible to isolate these arsenic-bearing zones from water supply wells, enabling production of water that complies with drinking water standards. It is hypothesized that geologic mapping together with detailed hydrogeochemical investigations will yield correlations which predict high arsenic occurrence for the siting of new drinking water production wells. More data and methods to assess the specific distribution, speciation, and mode of transport of arsenic in aquifers are needed to improve our predictions for arsenic occurrence in water supply wells. Research is also needed to assess whether we can ret

Structure of the Sumatra wedge affected by the 26th December 2004 :Effects of the lower plate volcanic ridges.

NASA Astrophysics Data System (ADS)

Rangin, C.; Sibuet, J. C.; Lin, J. Y.; Le Pichon, X.

2009-04-01

Detailed swath-bathymetry, coupled with echo-sounder data were collected offshore the northern tip of Sumatra over the rupture area of the 26th December 2004 Mw=9.2 earthquake during the Sumatra aftershock cruise. 20 ocean bottom seismometers were also deployed in the northern Sumatra area., and more than 1000 events were identified during the 12 days recording period. We mapped recently active steeply dipping thrust fault zone within the western termination of the Sunda accreted wedge. Main N10°W trending out of sequence thrust fault zones with a discrete westward vergency and some component of dextral strike-slip motion were continuously mapped within the wedge, on the basis of bathymetry and low frequency sounder profiles. The interplate boundary does not appear to extend into the frontal part of the wedge but most probably merges in its central part along these major faults, the Lower and Upper Splay Faults. After relocation, the seismicity shows different pattern in each side of this Upper Splay Fault. East of this boundary, beneath the Aceh basin, the earthquake depths ranged from 30 to 60 km allow us to illustrate the subducted plate. In the western part, the aftershock distribution is strongly influenced by the N-S orientated oceanic fracture zones. Two clusters of earthquakes between 10 and 50 km in depth trending along N-S direction are observed in the lower wedge that we interpret to be reactive fracture zones. The lower wedge is interpreted as the northern prolongation below the wedge of the lower plate NS oceanic fracture zone ridges affected by NS trending left lateral strike-slip faults. This wedge outer ridge is in the process of being transferred to the upper plate. On the other hand the central ridge is interpreted as possible stacked volcanic ridge slivers already incorporated into the upper plate along the subduction buttress (the inner ridge of the wedge). We propose that the tectonic interaction of the volcanic Indian Ocean fracture ridges of the subducted plate with the leading edge of the upper Sunda plate subduction zone is an active tectonic transfer process of oceanic material to the upper plate. The proposed emergence of the interplate boundary into the middle part of the wedge along the Lower Splay Fault, could have favoured the formation of the giant Sumatra tsunami at moderate water depth. This docking and temporary stacking of these volcanic ridges before their subduction at depth, is favoured by the strong oblique convergence that prevails up to the Bengal basin into the north.

Stable isotope evidence for the Bottom Convective Layer homogeneity in the Black Sea

PubMed Central

2014-01-01

The Black Sea is the largest euxinic basin on the Earth. The anoxic zone consists of the upper part water mass stratified by density, and the lower water mass homogenized relative to density (depth >1750 m), named the Bottom Convective Layer. To assess homogeneity and possible exchange of matter across the upper and lower boundaries of the Bottom Convective Layer, new data on stable isotope composition of S, O and H were obtained. Samples were collected in August 2008 and March 2009 from two stations located in the eastern central part of the Black Sea. Distribution of δ18O and δD values of water for the entire water column did not vary seasonally. Appreciable differences were marked for δD value variation in the picnocline area (water depth 200-400 m) and in the BCL 5 m above the bottom that might be caused by penetration of intrusions with elevated portion of shelf modified Mediterranean Water. Observed linear relationship between δ18O (or δD) and salinity indicates that mixing water and salt occurs at the same time, and the deep water of the Black Sea has two end members: the high-salinity Mediterranean seawater and freshwater input. In the Bottom Convective Layer, the average δ34S (H2S) was -40.6 ± 0.5‰ and did not vary seasonally. At the bottom (depth > 2000 m), 34S depletion down to –41.0‰ was observed. Our δ34S (SO4) data are by 2-3‰ higher than those measured previously for the Bottom Convective Layer. Sulfate from the aerobic zone with δ34S (SO4) = +21‰ corresponds to ocean water sulfate and that has not been subjected to sulfate reduction. Average δ34S (SO4) values for depths > 1250 m were found to be +23.0 ± 0.2‰ (1σ). Sulfur isotope composition of sulfate does not change in the Bottom Convective Layer and on its upper and lower boundaries, and does not depend on the season of observation. PMID:24739078

Electrical resistivity and porosity structure of the upper Biscayne Aquifer in Miami-Dade County, Florida

NASA Astrophysics Data System (ADS)

Whitman, Dean; Yeboah-Forson, Albert

2015-12-01

Square array electrical soundings were made at 13 sites in the Biscayne Aquifer distributed between 1 and 20 km from the shoreline. These soundings were modeled to investigate how resistivity varies spatially and with depth in the upper 15 m of the aquifer. Porosity was estimated from the modeled formation resistivity and observed pore fluid resistivity with Archie's Law. The models were used to interpolate resistivity and porosity surfaces at -2, -5, -8, and -15 m elevations. Modeled resistivity in the unsaturated zone is generally higher than 300 Ω m with the resistivity at sites with thick unsaturated zones greater than 1000 Ω m. Resistivity in the saturated zone ranges from 30 to 320 Ω m. At many sites in the western portions of the study area, resistivity is constant or increases with depth whereas sites in the center of the Atlantic Coastal Ridge exhibit a distinct low resistivity zone (ρ < 45 Ω m) at elevations ranging between -5 and -10 m. At one site near the shore of Biscayne Bay, the resistivity is less than 10 Ω m at -5 m elevation reflecting the presence of salt water in the aquifer. The estimated porosity ranges between 14% and 71% with modal values near 25%. The porosity structure varies both with depth and spatially. Western sites exhibit a high porosity zone at shallow depths best expressed in a NE-SW trending zone of 40-50% porosity situated near the western margin of the Atlantic Coastal Ridge. This zone roughly corresponds in depth with the Q5 chronostratigraphic unit of the Miami Fm. which constitutes the upper flow unit of the Biscayne Aquifer. The highest porosity (>50%) is seen at elevations below -5 m at sites in the center of the Atlantic Coastal Ridge and likely corresponds to solution features. The general NE-SW trend of the resistivity and porosity structure suggests a causal connection with the Pleistocene paleogeography and sedimentary environments.

Development of a large volume of eruptible mush in the upper Wooley Creek batholith, Klamath Mountains, California: evidence from bulk rock, mineral analyses and textural observations

NASA Astrophysics Data System (ADS)

Coint, N.; Barnes, C. G.; Barnes, M. A.; Yoshinobu, A. S.

2012-12-01

The modalities of development of large volumes of mush in the middle to upper crust capable of erupting have been debated over the past few years. The existence of crystal-rich ignimbrites in the volcanic record indicate that eruptive products do not necessarily correspond to evacuation of the residual magma but that the mush itself can be drained during eruptive events. In this study we present a plutonic example of a large magma batch that evolved by fractional crystallization at a hundred km3 scale: the upper zone of the Wooley Creek batholith (WCb). The WCb is an intrusive complex emplaced over less than 3 m.y. (Kevin Chamberlain, personal communication). The upper zone grades upward from quartz diorite (53 wt% SiO2) to granite (70 wt% SiO2). Hornblende from the central and upper zone have rare earth element patterns that are parallel to one another and with REE concentrations and negative Eu anomalies that decrease from core to rim. The similarities of hornblende REE patterns throughout both the central and upper zones of the system (160 km2 of exposed area) suggest that hornblende crystallized from a magma batch of fairly homogeneous composition. Thus, upward changes in bulk composition between rocks at the bottom and the top of this unit result from varying mineral proportions, with more subhedral plagioclase and hornblende at the bottom and more anhedral to euhedral quartz and interstitial to poikilitic K-feldspar at the top. Two possible explanations are considered: 1) more felsic batches of magma were emplaced at the top of the system and more mafic ones were restricted to the bottom, 2) the upper zone acquired its upward compositional zoning through melt percolation, with the less dense felsic melt ponding at the roof of the system. In the first case, the similarity of hornblende REE patterns throughout the upper zone cannot be explained. Therefore, we favor the second explanation, which is also supported by the lack of sharp contacts in the upper zone. Individual magma batches in the central zone contain hornblende of similar composition as in the upper zone and are interpreted as a preserved part of the feeder system of the latter. Therefore the magma in both the central and upper WCb was already fairly homogeneous when it arrived at the level of emplacement. Dacitic to rhyodacitic roof dikes with30-40% phenocrysts of hornblende and plagioclase with compositions similar to those found in the central and upper zones indicate that the mush was once eruptible. The presence of quartz phenocrysts, which are only found in the uppermost portion of the upper zone, show that 'eruption' occurred after the development of the broad zoning of the upper zone and after more evolved melt had collected at the top of an underlying mush. This study introduces new tools to study magmatic reservoir evolution. The combination of bulk rock and mineral data allows assessment of the extent of mineral-melt separation and identification of the composition of a potential parental magma(s). These data can ideally be used to delimit the size of magma batches and constrain the scale of their chemical/physical connectivity.

Petrophysics of Lower Silurian sandstones and integration with the tectonic-stratigraphic framework, Appalachian basin, United States

USGS Publications Warehouse

Castle, J.W.; Byrnes, A.P.

2005-01-01

Petrophysical properties were determined for six facies in Lower Silurian sandstones of the Appalachian basin: fluvial, estuarine, upper shoreface, lower shoreface, tidal channel, and tidal flat. Fluvial sandstones have the highest permeability for a given porosity and exhibit a wide range of porosity (2-18%) and permeability (0.002-450 md). With a transition-zone thickness of only 1-6 m (3-20 ft), fluvial sandstones with permeability greater than 5 md have irreducible water saturation (Siw) less than 20%, typical of many gas reservoirs. Upper shoreface sandstones exhibit good reservoir properties with high porosity (10-21%), high permeability (3-250 md), and low S iw (<20%). Lower shoreface sandstones, which are finer grained, have lower porosity (4-12%), lower permeability (0.0007-4 md), thicker transition zones (6-180 m [20-600 ft]), and higher S iw. In the tidal-channel, tidal-flat, and estuarine facies, low porosity (average < 6%), low permeability (average < 0.02 md), and small pore throats result in large transition zones (30-200 m; 100-650 ft) and high water saturations. The most favorable reservoir petrophysical properties and the best estimated production from the Lower Silurian sandstones are associated with fluvial and upper shoreface facies of incised-valley fills, which we interpret to have formed predominantly in areas of structural recesses that evolved from promontories along a collisional margin during the Taconic orogeny. Although the total thickness of the sandstone may not be as great in these areas, reservoir quality is better than in adjacent structural salients, which is attributed to higher energy depositional processes and shallower maximum burial depth in the recesses than in the salients. Copyright ??2005. The American Association of Petroleum Geologists. All rights reserved.

Imaging Water in Deformed Quartzites: Examples from Caledonian and Himalayan Shear Zones

NASA Astrophysics Data System (ADS)

Kronenberg, Andreas; Ashley, Kyle; Hasnan, Hasnor; Holyoke, Caleb; Jezek, Lynna; Law, Richard; Thomas, Jay

2016-04-01

Infrared IR measurements of OH absorption bands due to water in deformed quartz grains have been collected from major shear zones of the Caledonian and Himalayan orogens. Mean intragranular water contents were determined from the magnitude of the broad OH absorption at 3400 cm-1 as a function of structural position, averaging over multiple grains, using an IR microscope coupled to a conventional FTIR spectrometer with apertures of 50-100 μm. Images of water content were generated by scanning areas of up to 4 mm2 of individual specimens with a 10 μm synchrotron-generated IR beam and contouring OH absorptions. Water contents vary with structural level relative to the central cores of shear zones and they vary at the grain scale corresponding to deformation and recrystallization microstructures. Gradients in quartz water content expressed over structural distances of 10 to 400 m from the centers of the Moine Thrust (Stack of Glencoul, NW Scotland), the Main Central Thrust (Sutlej valley of NW India), and the South Tibetan Detachment System (Rongbuk valley north of Mount Everest) indicate that these shear zones functioned as fluid conduits. However, the gradients differ substantially: in some cases, enhanced fluid fluxes appear to have increased quartz water contents, while in others, they served to decrease water contents. Water contents of Moine thrust quartzites appear to have been reduced during shear at greenschist facies by processes of regime II BLG/SGR dislocation creep. Intragranular water contents of the protolith 70 m below the central fault core are large (4078 ± 247 ppm, H/106 Si) while mylonites within 5 mm of the Moine hanging wall rocks have water contents of only 1570 (± 229) ppm. Water contents between these extremes vary systematically with structural level and correlate inversely with the extent of dynamic recrystallization (20 to 100%). Quartz intragranular water contents of Himalayan thrust and low-angle detachment zones sheared at upper amphibolite conditions by regime III GBM creep show varying trends with structural level. Water contents increase toward the Lhotse detachment of the Rongbuk valley, reaching 11,350 (± 1095) ppm, whereas they decrease toward the Main Central Thrust exposed in the western part of the Sutlej valley to values as low as 170 (± 25) ppm. Maps of intragranular water content correspond to populations of fluid inclusions, which depend on the history of deformation and dynamic recrystallization. Increases in water content require the introduction of secondary fluid inclusions, generally by brittle microcracking followed by crack healing and processes of inclusion redistribution documented in milky quartz experiments. Decreases in water content result from dynamic recrystallization, as mobile grain boundaries sweep through wet porphyroclasts, leaving behind dry recrystallized grains. Intragranular water contents throughout greenschist mylonites of the Moine thrust are comparable to those of quartz weakened by water in laboratory experiments. However, water contents of upper amphibolite mylonites of the Main Central Thrust are far below those required for water weakening at experimental strain rates and offer challenges to our understanding of quartz rheology.

Archean sedimentation and tectonics in southern Africa

NASA Technical Reports Server (NTRS)

Kidd, W. S. F.

1984-01-01

Sequences in the Barberton Mountain Land greenstone belt (southern Africa) were examined to determine the nature of the sedimentary rocks, their tectonic implications, and their bearing on the present large-scale structural condition of the belt. Also assessed was whether there was evidence for a significant component of shallow-water-deposited sedimentary rocks in the parent materials of the Limpopo belt. The nature of a largehigh strain zone on the southern margin of the central Limpopo belt was examined.

The Marysville, Montana Geothermal Project

NASA Technical Reports Server (NTRS)

Mcspadden, W. R.; Stewart, D. H.; Kuwada, J. T.

1974-01-01

Drilling the first geothermal well in Montana presented many challenges, not only in securing materials and planning strategies for drilling the wildcat well but also in addressing the environmental, legal, and institutional issues raised by the request for permission to explore a resource which lacked legal definition. The Marysville Geothermal Project was to investigate a dry hot rock heat anomaly. The well was drilled to a total depth of 6790 feet and many fractured water bearing zones were encountered below 1800 feet.

Herbicide and nitrate variation in alluvium underlying a cornfield at a site in Iowa County, Iowa

USGS Publications Warehouse

Kalkhoff, S.J.; Detroy, M.G.; Cherryholmes, K.; Kuzniar, R.L.

1992-01-01

A hydrologic investigation to determine vertical and seasonal variation of atrazine, alachlor, cyanazine, and nitrate at one location and to relate the variation to ground-water movement in the Iowa River alluvium was conducted in Iowa County, Iowa, from March 1986 to December 1987. Water samples were collected at discrete intervals through the alluvial sequence from the soil zone to the base of the aquifer. Alachlor, atrazine, and cyanazine were detected most frequently in the soil zone but also were present in the upper part of the alluvial aquifer. Alachlor was detected sporadically, whereas, atrazine, cyanazine, and nitrate were present throughout the year. In the alluvial aquifer, the herbicides generally were not detected during 1986 and were present in detectable concentrations for only a short period of time in the upper 1.6 meters of the aquifer during 1987. Nitrate was present throughout the alluvium and was stratified in the alluvial aquifer. The largest nitrate concentrations were detected in the middle part of the aquifer. Nitrate concentrations were variable only in the upper 2 meters of the aquifer. Vertical movement of herbicides and nitrate in the soil correlated with precipitation and degree of saturation. A clay layer retarded vertical movement of atrazine but not nitrate from the soil layer to the aquifer. Vertical movement could not account for the chemical variation in the alluvial aquifer.

Tectonic and regional metamorphic implications of the discovery of Middle Ordovician conodonts in cover rocks east of the Green Mountain massif, Vermont

USGS Publications Warehouse

Ratcliffe, N.M.; Harris, A.G.; Walsh, G.J.

1999-01-01

Middle Ordovician (late Arenigian - early Caradocian) conodonts were recovered from a dolostone lens in carbonaceous schist 30 m below the base of the Pinney Hollow Formation in the Eastern Cover sequence near West Bridgewater, Vermont. These are the first reported fossils from the metamorphic cover sequence rocks east of the Green Mountain, Berkshire, and Housatonic massifs of western New England. The conodonts are recrystallized, coated with graphitic matter, thermally altered to a color alteration index (CAI) of at least 5, and tectonically deformed. The faunule is nearly monospecific, consisting of abundant Periodon aculeatus Hadding? and rare Protopanderodus. The preponderance of Periodon and the absence of warm, shallow-water species characteristic of the North American Midcontinent Conodont Province suggest a slope or basin depositional setting. The conodont-bearing carbonaceous schist is traceable 3 km southeast to the Plymouth area, where it had been designated the uppermost member of the Plymouth Formation, previously regarded as Early Cambrian in age. The age and structural position of the carbonaceous schist above dolostones of the Plymouth Formation but below the Pinney Hollow Formation (upper Proterozoic and Lower Cambrian?) suggest that this unit may be correlative or time transgressive with the Ira Formation, which underlies the Taconic allochthons in the Vermont Valley. Such a correlation supports the concept of placing the western limit of the root zone of the Taconic allochthons beneath the Pinney Hollow Formation. An approximate absolute age assignment for the conodont-bearing rock is between 470 and 454 Ma. This suggests that dynamothermal metamorphism during the Taconian orogeny on the east flank of the Green Mountains was younger than early Caradocian, which is in accord with the middle Caradocian age of the Ira Formation west of the Green Mountain massif.

Evaluating Bangestan reservoirs and targeting productive zones in Dezful embayment of Iran

NASA Astrophysics Data System (ADS)

Nasseri, Aynur; Jafar Mohammadzadeh, Mohammad; HashemTabatabaee, Seyyed

2016-12-01

A progressive stepwise procedure was adopted to evaluate the main reservoirs of the Bangestan group in a southwestern oil field of Iran. In order to identify productive zones, the results of lithofacies and well tops correlation were assessed using well log and core data. Accordingly the resulting zonation based on lithofacies revealed inaccurate results. Therefore, in order to limit the uncertainty of zonation, well tops correlations were considered. For this purpose, boundaries of reservoirs were precisely defined and well logs correlation was carried out based on geological information and full set logs. The resulting well tops correlation indicates the presence of several reservoirs such as Ilam and Sarvak formations, and each of these has several zones. Among them, the Ilam formation is recognized as the best reservoir in the field and the Sarvak formation in the second priority for oil production. Due to changes in the facies trend of the Sarvak formation, more than Ilam, the Sarvak formation was mostly considered in this study. Subsequently the Ilam formation was divided into four zones, among them (Ilam-Upper, Ilam- Main, Ilam-Poor) were identified as the oil reservoir units. Similarly, the Sarvak formation was also divided into 11 units, where the Sarvak-L2b unit was identified as the oil-bearing reservoir in the formation. Furthermore, in order to contribute for better analysis of the depositional environment and to improve the understanding of its lateral and vertical variations, 3D modeling of reservoir units was established, which lead to limit the uncertainty in evaluation. Based on the well correlation results, deep and thickness maps, porosity, water saturation and the hydrocarbon column assessments were prepared, in addition the distribution of petrophysical parameters was also evaluated. Finally, an oil reserve estimation was carried out based on volumetric estimation and its corresponding distribution maps in different reservoir units of the formation were presented. This study indicates that the consecutive sequential approach to the problem, by self controlling the process, lead to the detection of the Sarvak-L2b unit as one of the productive zones in the field. This zone also indicates favorable conditions for high productivity in central areas of the field where the reservoir has a high quality for production.

Optimization of Remediation Conditions using Vadose Zone Monitoring Technology

NASA Astrophysics Data System (ADS)

Dahan, O.; Mandelbaum, R.; Ronen, Z.

2010-12-01

Success of in-situ bio-remediation of the vadose zone depends mainly on the ability to change and control hydrological, physical and chemical conditions of subsurface. These manipulations enables the development of specific, indigenous, pollutants degrading bacteria or set the environmental conditions for seeded bacteria. As such, the remediation efficiency is dependent on the ability to implement optimal hydraulic and chemical conditions in deep sections of the vadose zone. Enhanced bioremediation of the vadose zone is achieved under field conditions through infiltration of water enriched with chemical additives. Yet, water percolation and solute transport in unsaturated conditions is a complex process and application of water with specific chemical conditions near land surface dose not necessarily result in promoting of desired chemical and hydraulic conditions in deeper sections of the vadose zone. A newly developed vadose-zone monitoring system (VMS) allows continuous monitoring of the hydrological and chemical properties of the percolating water along deep sections of the vadose zone. Implementation of the VMS at sites that undergoes active remediation provides real time information on the chemical and hydrological conditions in the vadose zone as the remediation process progresses. Manipulating subsurface conditions for optimal biodegradation of hydrocarbons is demonstrated through enhanced bio-remediation of the vadose zone at a site that has been contaminated with gasoline products in Tel Aviv. The vadose zone at the site is composed of 6 m clay layer overlying a sandy formation extending to the water table at depth of 20 m bls. The upper 5 m of contaminated soil were removed for ex-situ treatment, and the remaining 15 m vadose zone is treated in-situ through enhanced bioremedaition. Underground drip irrigation system was installed below the surface on the bottom of the excavation. Oxygen and nutrients releasing powder (EHCO, Adventus) was spread below the irrigation system to enrich the percolating water. The vadose zone monitoring system that was installed at the site allowed accurate monitoring of the wetting cycles, including: (1) wetting front propagation velocities, (2) temporal variation of the sediment water content, (2) chemical composition of the percolating water, (3) isotopic composition of BTEX compounds, (4) variations in nutrient concentration, and (5) variations in the vadose zone redox potential. Preliminary results showed that the wetting front crossed the entire vadose zone in four days reaching maximum water content values of 12 to 18 %. Temporal variation in the sediment BTEX concentrations indicated significant reduction in highly soluble and mobile compounds such as MTBE. Yet the chemical composition of the water samples through the first sampling campaign indicated that the limiting factor for biodegradation at the first wetting cycle was insufficient nitrogen. Results from each wetting cycles were used to improve the following wetting cycles in order to optimize the vadose zone conditions for microbial activity while minimizing leaching of contaminants to the groundwater.

Fluid flow and water-rock interaction in the East Rift Zone of Kilauea Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Conrad, Mark E.; Thomas, Donald M.; Flexser, Steven; Vennemann, Torsten W.

1997-07-01

The East Rift Zone of Kilauea Volcano in Hawaii represents a major area of geothermal activity. Fluid inclusion and stable isotope analyses of secondary hydrothermal minerals in core samples from three scientific observation holes (SOH) drilled into the rift zone indicate that the geothermal system is dominated by meteoric waters to depths of as much as 1500 m below sea level. Calculated δ18O and δD values for fluids on the north side of the rift zone indicate that the deep meteoric fluids may be derived from precipitation on the upper slopes of Mauna Loa Volcano. In the interior of the rift zone, recharge is dominated by seawater mixed with local meteoric water. Water/rock ratios in the rift area are approximately 2, but strongly 18O-enriched fluids in the deeper parts of the SOH-2 and SOH-4 drill holes (on the north side of the rift) indicate that the fluids underwent extensive interaction with rocks prior to reaching this part of the rift zone. Marine carbonates at the subaerial to submarine transition (between 1700 and 1780 m depth) in SOH-4 have not fully equilibrated with the fluids, suggesting that the onset of hydrothermal activity in this area was relatively recent (<2000 years). This may represent increased volcanic activity along the rift after the end of the Ai La'au phase of eruptive activity at the Kilauea summit approximately 1000 years ago, or it may reflect progressive evolution of the hydrothermal system in response to southward migration of intrusive activity within the rift.

Regional changes and global connections: monitoring climate variability and change in the western United States

Treesearch

Henry F. Diaz

2004-01-01

Mountain ecosystems of the Western United States are complex and include cold desert biomes, such as those found in Nevada; subpolar biomes found in the upper treeline zone; and tundra ecosystems, occurring above timberline. Many studies (for example, Thompson 2000) suggest that high-elevation environments, comprising glaciers, snow, permafrost, water, and the...

Relationships among benthic green macroalgae, infaunal invertebrates, and dissolved sulfides in sediment pore waters, Yaquina Estuary, Oregon, USA

EPA Science Inventory

Relatively high abundances of benthic green macroalgae (Ulva spp.) have been measured in Yaquina Estuary on the central coast of the State of Oregon, USA. Band transects (30 meters in width) from the lower to the upper intertidal zone were established at two sites (Idaho Point a...

Growth of early continental crust by water-present eclogite melting in subduction zones

NASA Astrophysics Data System (ADS)

Laurie, A.; Stevens, G.

2011-12-01

The geochemistry of well preserved Paleo- to Meso-Archaean Tonalite-Trondhjemite-Granodiorite (TTG) suite rocks, such as the ca 3.45 Ga trondhjemites from the Barberton greenstone belt in South Africa, provides insight into the origins of Earth's early felsic continental crust. This is particularly well demonstrated by the high-Al2O3 variety of these magmas, such as the Barberton rocks, where the geochemistry requires that they are formed by high pressure (HP) melting of a garnet-rich metamafic source. This has been interpreted as evidence for the formation of these magmas by anatexis of the upper portions of slabs within Archaean subduction zones. Most of the experimental data relevant to Archaean TTG genesis has been generated by studies of fluid-absent melting of metabasaltic sources. However, water drives arc magmatism within Phanerozoic subduction zones and thus, understanding the behaviour of water in Archaean subduction zones, may have considerable value for understanding the genesis of these TTG magmas. Consequently, this study investigates the role of HP water-present melting of an eclogite-facies starting material, in the production of high-Al2O3 type TTG melts. Water-saturated partial melting experiments were conducted between 1.9 and 3.0GPa; and, 870°C and 900°C. The melting reaction is characterized by the breakdown of sodic Cpx, together with Qtz and H2O, to form melt in conjunction with a less sodic Cpx: Qtz + Cpx1 + Grt1 + H2O = Melt + Cpx2 + Grt2. In many of the experimental run products, melt segregated efficiently from residual crystals, allowing for the measurement of a full range of trace elements via Laser Ablation Inductively Coupled Plasma Mass Spectroscopy. The experimental glasses produced by this study have the compositions of peraluminous trondhjemites; and they are light rare earth element, Zr and Sr enriched; and heavy rare earth element, Y and Nb depleted. The compositions of the experimental glasses are similar to high-Al2O3 type Archaean TTG rocks in general and similar to the Barberton trondhjemites in particular. Additionally, due to Cpx being a major reactant, Ni and Cr contents of the glasses are high and match those of high-Al2O3 type TTG compositions. This challenges the notion that this aspect of TTG geochemistry indicates interaction of the magma with the mantle wedge. Consequently, we propose that water-present melting of an eclogitic source is a viable mechanism for the genesis of Paleo- to Meso-Archaean felsic continental crust. Importantly, this mechanism of TTG formation involves the upper surface of the subducting slab acting as an anatectic capture site for metamorphic fluid which evolved from cooler domains slightly deeper within the hydrated upper portion of the slab. This explains both TTG genesis and the lack of characteristic products of mantle wedge metasomatism, such as andesites, concurrent with TTG magmatism of this type during the Paleo- to Meso-Archaean. Cooling of the upper mantle by only a small amount towards to end of the Archaean Eon acted to "turn off" water-present melting of the slab, allowing water to metasomatise the mantle wedge and induce calc-alkaline magmatism in association with volcanic arcs.

Sound velocity of 23 Å phase (a new Al-bearing hydrous Mg-silicate) to 14 GPa

NASA Astrophysics Data System (ADS)

Cai, N.; Chen, T.; Qi, X.; Inoue, T.; Li, B.

2016-12-01

Dense hydrous phases are believed to play an important role in transporting water back into the deep interior of the Earth. Recently, a new Al-bearing hydrous Mg-silicate named 23 Å phase (ideal composition Mg11Al2Si4O16(OH)12) was reported (Cai et al., 2015), which could be a very important hydrous phase in subducting slab. Here for the first time we measured the compressional and shear wave velocities of this new hydrous phase under mantle pressures. The sample was synthesized at 10 GPa and 1000 ºC using the chemical mixture of stoichiometric as starting materials. The recovered sample was then crushed into fine powder and hot pressed at 10 GPa and 900 ºC for 3 hours. X-ray diffraction, density measurement, and SEM characterization indicated that the specimen is nearly a pure phase, 20 µm in grain size, with a bulk density of 3.004 g/cm3. The acoustic measurements were conducted in a 1000-ton uniaxial split-cylinder multi-anvil apparatus using ultrasonic interferometry techniques (Li et al., 1996) up to 14 GPa at room temperature. The pressures were determined in situ by using alumina buffer rod as a pressure marker (Wang et al., 2015). A dual-mode piezoelectric transducer enables us to measure P and S wave travel times simultaneously, which in turn allows for a precise determination of the sound velocities and elastic bulk and shear moduli at high pressures. Preliminary results suggest that the velocities, (especially for S wave) of this 23 Å phase are slower than that of phase A and most of the mantle minerals. These results may have important implications for understanding some localized low velocity zones in subduction zones. Cai, N., T. Inoue, K. Fujino, H. Ohfuji and H. Yurimoto (2015) A Possible New Al-bearing Hydrous Mg-silicate (23 Å phase) in the Deep Upper Mantle. Am Mineral. 100: 2330-2335. Li, B., I. Jackson, T. Gasparik, and R. C. Liebermann (1996), Elastic wave velocity measurement in multianvil apparatus to 10 GPa using ultrasonic interferometry, Phys. Earth Planet. Inter., 98,79-91. Wang, X., T. Chen, X. Qi, Y. Zou, J. Kung, T. Yu, Y. Wang, R. C. Liebermann and B. Li (2015), Acoustic travel time gauges for in-situ determination of pressure and temperature in multi-anvil apparatus, J. Appl. Phys., 118, 065901.

Concentration of Natural Gas Hydrate Beneath the Permafrost Zone: Implications for Geochemical and Hydrologic Investigations

NASA Astrophysics Data System (ADS)

Uchida, T.; Waseda, A.; Namikawa, T.

2004-12-01

Gas hydrates are ice-like solids made of water molecules containing various gas molecules. The geological evaluations have suggested worldwide methane contents of gas hydrate beneath deep sea floors as well as permafrost-related zones to about twice the total reserves of conventional and unconventional hydrocarbon. Scientific and economic interests are increasing in gas hydrate as a new energy resource and a potential greenhouse gas. In 1998 and 2002 Mallik wells were drilled in the Canadian Arctic that clarified the characteristics of gas hydrate-dominant layers at depths from 890 to 1110 m beneath the permafrost zone. Continuous downhole well log data, anomalies of chloride contents in pore waters, core temperature depression as well as visible gas hydrates have confirmed the highly saturated pore-space hydrate as intergranular pore filling within sandy layers, whose saturations are higher than 70% in pore volume. Muddy sediments scarcely contain gas hydrate. The Nankai Trough runs along the Japanese Island, where forearc basins and accretionary prisms developed extensively and BSRs (bottom simulating reflectors) have been recognized widely. The METI Nankai Trough wells in 2000 also revealed the presence of pore-space hydrate filling intergranular pore of sandy layers. It is remarked that there are many similar features in appearance and characteristics between the Mallik and Nankai Trough areas with observations of well-interconnected and highly saturated pore-space hydrate. It is necessary for evaluating subsurface fluid flow behaviors to know both porosity and permeability of gas hydrate-bearing sandy sediments, and measurements of water permeability for them indicate that highly saturated sands may have permeability of a few millidarcies. Subsequent analyses in sedimentology and geochemistry performed on gas hydrate-bearing sands revealed important geologic and sedimentologic controls on the formation and concentration of gas hydrate. It is suggested that the distribution of a porous and coarser-grained sandy sediments is one of the most important factors to control the occurrence of gas hydrates, as well as physicochemical conditions.

Recent (2008-10) concentrations and isotopic compositions of nitrate and concentrations of wastewater compounds in the Barton Springs zone, south-central Texas, and their potential relation to urban development in the contributing zone

USGS Publications Warehouse

Mahler, Barbara J.; Musgrove, MaryLynn; Herrington, Chris; Sample, Thomas L.

2011-01-01

During 2008–10, the U.S. Geological Survey, in cooperation with the City of Austin, the City of Dripping Springs, the Barton Springs/Edwards Aquifer Conservation District, the Lower Colorado River Authority, Hays County, and Travis County, collected and analyzed water samples from five streams (Barton, Williamson, Slaughter, Bear, and Onion Creeks), two groundwater wells (Marbridge well [YD–58–50–704] and Buda well [LR–58–58–403]), and the main orifice of Barton Springs in Austin, Texas, with the objective of characterizing concentrations and isotopic compositions of nitrate and concentrations of wastewater compounds in the Barton Springs zone. The Barton Springs zone is in south-central Texas, an area undergoing rapid growth in population and in land area affected by development, with associated increases in wastewater generation. Over a period of 17 months, during which the hydrologic conditions transitioned from dry to wet, samples were collected routinely from the streams, wells, and spring and, in response to storms, from the streams and spring; some or all samples were analyzed for nitrate, nitrogen and oxygen isotopes of nitrate, and waste­water compounds. The median nitrate concentrations in routine samples from all sites were higher in samples collected during the wet period than in samples collected during the dry period, with the greatest difference for stream samples (0.05 milligram per liter during the dry period to 0.96 milligram per liter for the wet period). Nitrate concentrations in recent (2008–10) samples were elevated relative to concentrations in historical (1990–2008) samples from streams and from Barton Springs under medium- and high-flow conditions. Recent nitrate concentrations were higher than historical concentrations at the Marbridge well but the reverse was true at the Buda well. The elevated concentrations likely are related to the cessation of dry conditions coupled with increased nitrogen loading in the contributing watersheds. An isotopic composition of nitrate (delta nitrogen–15) greater than 8 per mil in many of the samples indicated there was a contribution of nitrate with a biogenic (human and or animal waste, or both) origin. Wastewater compounds measured in routine samples were detected infrequently (3 percent of cases), and concentrations were very low (less than the method reporting level in most cases). There was no correlation between nitrate concentrations and the frequency of detection of wastewater compounds, indicating that wastewater compounds might be undergoing removal during such processes as infiltration through soil. Three potential sources of biogenic nitrate to the contributing zone were considered: septic systems, land application of treated wastewater, and domesticated dogs and cats. During 2001–10, the estimated densities of septic systems and domesticated dogs and cats (number per acre) increased in the watersheds of all five creeks, and the rate of land application of treated wastewater (gallons per day per acre) increased in the watersheds of Barton, Bear, and Onion Creeks. Considering the timing and location of the increases in the three sources, septic systems were considered a likely source of increased nitrate to Bear Creek; land application of treated wastewater a likely source to Barton, Bear, and Onion Creeks; and domestic dogs and cats a potential source principally to Williamson Creek. The results of this investigation indicate that baseline water quality, in terms of nitrate, has shifted upward between 2001 and 2010, even without any direct discharges of treated wastewater to the creeks.

The benthic fauna from the lower Maastrichtian chalk of Kronsmoor (Saturn quarry, northern Germany): composition and palaeoecologic implications

NASA Astrophysics Data System (ADS)

Engelke, Julia; Linnert, Christian; Mutterlose, Jörg; Wilmsen, Markus

2017-04-01

The Saturn quarry near Kronsmoor (northern Germany) offers an undisturbed section of upper Campanian to lower Maastrichtian chalks. The target interval of the DFG project "Biodiversity and plankton-benthos coupling: an integrated ecosystem analysis from the Late Cretaceous Chalk" is focused on the lower Maastrichtian Belemnella obtusa Zone to mid-Belemnella sumensis Zone, i.e. to the uppermost Kronsmoor and lowermost Hemmoor formations. In this interval, a conspicuous increase in macrofossil abundance without apparent lithofacies changes has been observed and the project intends to integrate planktic, benthic and geochemical proxies for a comprehensive understanding of the Chalk Sea ecosystem. The aim of this study is the analysis of the benthic community. In a first step, the benthic body fossils of the c. 25-m-thick section were semi-quantitatively studied based on a collection of more than 1,000 specimens. Two successive benthic macrofossil assemblages were recognised: the lower interval (upper part of the Kronsmoor Formation, B. obtusa Zone) is characterized by low abundances, only about 100 macroinvertebrates were collected, mostly irregular and regular echinoids, brachiopods and crinoids. The upper interval (B. sumensis Zone) shows an eight times higher macroinvertebrate abundance and a conspicuous dominance of brachiopods, increasing from only 30 to over 500 specimens. In order to quantify the observed qualitative palaeoecological changes, 33 bulk samples of about 6 kg each were retrieved in a distance of c. 0.75 m. The bulk samples were frozen and thawed, washed and sieved in different sizes. The fraction 500 μm-1 mm and >1 mm were picked, sorted and counted. A diverse assemblage of bryozoans, foraminifers, shell fragments of brachiopods and bivalves, spines and test fragments of different echinoid taxa, parts of asteroids and ophiuroids, sponge debris, crinoids and small serpulids, is present. Reduced abundances in the lower part and generally higher abundances in the upper part are recognised. The palaeoecological analysis of both datasets indicates different guilds, of which epifaunal suspension feeders (fixo-sessile and libero-sessile guilds), comprising c. 50 % of the fauna in the lower interval, increase to a dominance of c. 80 % in the upper interval, including a considerable proportion of rhynchonelliform brachiopods. The palaeoecological data of benthic communities at Kronsmoor are indicative of increased nutrient availability during the early Maastrichtian. However, in the absence of any evidence of increased productivity in the overlying photic zone (calcareous nannofossil data), a lateral input (upwelling) of nutrient-rich waters onto the shelf to fuel the benthic ecosystem has to be considered. This view is supported by records of contemporaneous changes in latest Cretaceous ocean circulation that followed the latest Campanian cooling event, inclusive of a southward spread of waters of intermediate depth from high-latitudes.

Geophysical characteristics of the hydrothermal systems of Kilauea volcano, Hawaii

USGS Publications Warehouse

Kauahikaua, J.

1993-01-01

Clues to the overall structure of Kilauea volcano can be obtained from spatial studies of gravity, magnetic, and seismic velocity variations. The rift zones and summit are underlain by dense, magnetic, high P-wave-velocity rocks at depths of about 2 km less. The gravity and seismic velocity studies indicate that the rift structures are broad, extending farther to the north than to the south of the surface features. The magnetic data give more definition to the rift structures by allowing separation into a narrow, highly-magnetized, shallow zone and broad, flanking, magnetic lows. The patterns of gravity, magnetic variations, and seismicity document the southward migration of the upper cast rift zone. Regional, hydrologic features of Kilauea can be determined from resistivity and self-potential studies. High-level groundwater exists beneath Kilauea summit to elevations of +800 m within a triangular area bounded by the west edge of the upper southwest rift zone, the east edge of the upper east rift zone, and the Koa'c fault system. High-level groundwater is present within the east rift zone beyond the triangular summit area. Self-potential mapping shows that areas of local heat produce local fluid circulation in the unconfined aquifer (water table). The dynamics of Kilauea eruptions are responsible for both the source of heat and the fracture permeability of the hydrothermal system. Shallow seismicity and surface deformation indicate that magma is intruding and that fractures are forming beneath the rift zones and summit area. Magma supply estimates are used to calculate the rate of heat input to Kilauea's hydrothermal systems. Heat flows of 370-820 mW/m2 are calculated from deep wells within the lower east rift zone. The estimated heat input rate for Kilauea of 9 gigawatts (GW) is at least 25 times higher than the conductive heat loss as estimated from the heat flow in wells extrapolated over the area of the summit caldera and rift zones. Heat must be dissipated by another mechanism, or the heat input rate estimates are much too high. ?? 1993.

Fracture properties from tight reservoir outcrop analogues with application to geothermal exploration

NASA Astrophysics Data System (ADS)

Philipp, Sonja L.; Reyer, Dorothea; Afsar, Filiz; Bauer, Johanna F.; Meier, Silke; Reinecker, John

2015-04-01

In geothermal reservoirs, similar to other tight reservoirs, fluid flow may be intensely affected by fracture systems, in particular those associated with fault zones. When active (slipping) the fault core, that is, the inner part of a fault zone, which commonly consists of breccia or gouge, can suddenly develop high permeability. Fault cores of inactive fault zones, however, may have low permeabilities and even act as flow barriers. In the outer part of a fault zone, the damage zone, permeability depends mainly on the fracture properties, that is, the geometry (orientation, aperture, density, connectivity, etc.) of the fault-associated fracture system. Mineral vein networks in damage zones of deeply eroded fault zones in palaeogeothermal fields demonstrate their permeability. In geothermal exploration, particularly for hydrothermal reservoirs, the orientation of fault zones in relation to the current stress field as well as their internal structure, in particular the properties of the associated fracture system, must be known as accurately as possible for wellpath planning and reservoir engineering. Here we present results of detailed field studies and numerical models of fault zones and associated fracture systems in palaeogeo¬thermal fields and host rocks for geothermal reservoirs from various stratigraphies, lithologies and tectonic settings: (1) 74 fault zones in three coastal sections of Upper Triassic and Lower Jurassic age (mudstones and limestone-marl alternations) in the Bristol Channel Basin, UK. (2) 58 fault zones in 22 outcrops from Upper Carboniferous to Upper Cretaceous in the Northwest German Basin (siliciclastic, carbonate and volcanic rocks); and (3) 16 fault zones in 9 outcrops in Lower Permian to Middle Triassic (mainly sandstone and limestone) in the Upper Rhine Graben shoulders. Whereas (1) represent palaeogeothermal fields with mineral veins, (2) and (3) are outcrop analogues of reservoir horizons from geothermal exploration. In the study areas of palaeo¬geothermal fields in the Bristol Channel (1), all mineral veins, most of which are extension fractures, are of calcite. They are clearly associated with the faults and indicate that geothermal water was transported along the then-active faults into the host rocks with evidence of injection as hydrofractures. Layers with contrasting mechanical properties (in particular, stiffnesses), however, acted as stress barriers and lead to fracture arrest. Along some faults, veins propagated through the barriers along faults to shallower levels. In the Northwest German Basin (2) there are pronounced differences between normal-fault zones in carbonate and clastic rocks. Only in carbonate rocks clear damage zones occur, characterized by increased fracture frequencies and high amounts of fractures with large apertures. On the Upper Rhine Graben shoulders (3) damage zones in Triassic Muschelkalk limestones are well developed; fault cores are narrow and comprise breccia, clay smear, host rock lenses and mineralization. A large fault zone in Triassic Bunter sandstone shows a clearly developed fault core with fault gouge, slip zones, deformation bands and host rock lenses, a transition zone with mostly disturbed layering and highest fracture frequency, and a damage zone. The latter damage zone is compared to the damage zone of a large Bunter sandstone fault zone currently explored for geothermal energy production. The numerical models focus on stress field development, fracture propagation and associated permeability changes. These studies contribute to the understanding of the hydromechanical behaviour of fault zones and related fluid transport in fractured reservoirs complementing predictions based on geophysical measurements. Eventually we aim at classifying and quantifying fracture system properties in fault zones to improve exploration and exploitation of geothermal reservoirs. Acknowledgements The authors appreciate the support of 'Niedersächsisches Ministerium für Wissen¬schaft und Kultur' and 'Baker Hughes' within the gebo research project (http://www.gebo-nds.de), the Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit (BMU; FKZ: 0325302, AuGE) and the Deutsche Forschungsgemeinschaft. GeoEnergy GmbH, Karlsruhe, is thanked for explorational data.

Mechanisms Leading to Co-Existence of Gas Hydrate in Ocean Sediments [Part 1 of 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryant, Steven; Juanes, Ruben

In this project we have sought to explain the co-existence of gas and hydrate phases in sediments within the gas hydrate stability zone. We have focused on the gas/brine interface at the scale of individual grains in the sediment. The capillary forces associated with a gas/brine interface play a dominant role in many processes that occur in the pores of sediments and sedimentary rocks. The mechanical forces associated with the same interface can lead to fracture initiation and propagation in hydrate-bearing sediments. Thus the unifying theme of the research reported here is that pore scale phenomena are key to understandingmore » large scale phenomena in hydrate-bearing sediments whenever a free gas phase is present. Our analysis of pore-scale phenomena in this project has delineated three regimes that govern processes in which the gas phase pressure is increasing: fracturing, capillary fingering and viscous fingering. These regimes are characterized by different morphology of the region invaded by the gas. On the other hand when the gas phase pressure is decreasing, the corresponding regimes are capillary fingering and compaction. In this project, we studied all these regimes except compaction. Many processes of interest in hydrate-bearing sediments can be better understood when placed in the context of the appropriate regime. For example, hydrate formation in sub-permafrost sediments falls in the capillary fingering regime, whereas gas invasion into ocean sediments is likely to fall into the fracturing regime. Our research provides insight into the mechanisms by which gas reservoirs are converted to hydrate as the base of the gas hydrate stability zone descends through the reservoir. If the reservoir was no longer being charged, then variation in grain size distribution within the reservoir explain hydrate saturation profiles such as that at Mt. Elbert, where sand-rich intervals containing little hydrate are interspersed between intervals containing large hydrate saturations. Large volumes (of order one pore volume) of gaseous and aqueous phases must be transported into the gas hydrate stability zone. The driver for this transport is the pressure sink induced by a reduction in occupied pore volume that accompanies the formation of hydrate from gas and water. Pore-scale imbibition models and bed-scale multiphase flow models indicate that the rate-limiting step in converting gas to hydrate is the supply of water to the hydrate stability zone. Moreover, the water supply rate is controlled by capillarity-driven flux for conditions typical of the Alaska North Slope. A meter-scale laboratory experiment confirms that significant volumes of fluid phases move into the hydrate stability zone and that capillarity is essential for the water flux. The model shows that without capillarity-driven flux, large saturations of hydrate cannot form. The observations of thick zones of large saturation at Mallik and Mt Elbert thus suggest that the primary control on these systems is the rate of transport of gaseous and aqueous phases, driven by the pressure sink at the base of the gas hydrate stability zone. A key finding of our project is the elucidation of ?capillary fracturing? as a dominant gas transport mechanism in low-permeability media. We initially investigate this phenomenon by means of grain-scale simulations in which we extended a discrete element mechanics code (PFC, by Itasca) to incorporate the dynamics of first single-phase and then multiphase flow. A reductionist model on a square lattice allows us to determine some of the fundamental dependencies of the mode of gas invasion (capillary fingering, viscous fingering, and fracturing) on the parameters of the system. We then show that the morphology of the gas-invaded region exerts a fundamental control on the fabric of methane hydrate formation, and on the overpressures caused by methane hydrate dissociation. We demonstrate the existence of the different invasion regimes by means of controlled laboratory experiments in a radial cell. We collapse the behavior in the form of a phase diagram fully characterized by two dimensionless groups: a modified capillary number and a ?fracturing number? that reflects the balance between the pressure forces that act to open conduits in the granular pack, and frictional forces that resist it. We use all this small-scale knowledge to propose simple mechanistic models of gas migration and hydrate formation at the geologic bed scale. We propose that methane transport in lake and oceanic sediments is controlled by dynamic conduits, which dilate and release gas as the falling hydrostatic pressure reduces the effective stress below the tensile strength of the sediments. We test our model against a four-month record of hydrostatic load and methane flux in Upper Mystic Lake, Mass., USA, and show that it captures the complex episodicity of methane ebullition. Our quantitative conceptualization opens the door to integrated modeling of methane transport to constrain global methane release from lakes and other methane-rich sediment systems, and to assess its climate feedbacks.« less

Mechanisms Leading to Co-Existence of Gas Hydrate in Ocean Sediments [Part 2 of 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryant, Steven; Juanes, Ruben

In this project we have sought to explain the co-existence of gas and hydrate phases in sediments within the gas hydrate stability zone. We have focused on the gas/brine interface at the scale of individual grains in the sediment. The capillary forces associated with a gas/brine interface play a dominant role in many processes that occur in the pores of sediments and sedimentary rocks. The mechanical forces associated with the same interface can lead to fracture initiation and propagation in hydrate-bearing sediments. Thus the unifying theme of the research reported here is that pore scale phenomena are key to understandingmore » large scale phenomena in hydrate-bearing sediments whenever a free gas phase is present. Our analysis of pore-scale phenomena in this project has delineated three regimes that govern processes in which the gas phase pressure is increasing: fracturing, capillary fingering and viscous fingering. These regimes are characterized by different morphology of the region invaded by the gas. On the other hand when the gas phase pressure is decreasing, the corresponding regimes are capillary fingering and compaction. In this project, we studied all these regimes except compaction. Many processes of interest in hydrate-bearing sediments can be better understood when placed in the context of the appropriate regime. For example, hydrate formation in sub-permafrost sediments falls in the capillary fingering regime, whereas gas invasion into ocean sediments is likely to fall into the fracturing regime. Our research provides insight into the mechanisms by which gas reservoirs are converted to hydrate as the base of the gas hydrate stability zone descends through the reservoir. If the reservoir was no longer being charged, then variation in grain size distribution within the reservoir explain hydrate saturation profiles such as that at Mt. Elbert, where sand-rich intervals containing little hydrate are interspersed between intervals containing large hydrate saturations. Large volumes (of order one pore volume) of gaseous and aqueous phases must be transported into the gas hydrate stability zone. The driver for this transport is the pressure sink induced by a reduction in occupied pore volume that accompanies the formation of hydrate from gas and water. Pore-scale imbibition models and bed-scale multiphase flow models indicate that the rate-limiting step in converting gas to hydrate is the supply of water to the hydrate stability zone. Moreover, the water supply rate is controlled by capillarity-driven flux for conditions typical of the Alaska North Slope. A meter-scale laboratory experiment confirms that significant volumes of fluid phases move into the hydrate stability zone and that capillarity is essential for the water flux. The model shows that without capillarity-driven flux, large saturations of hydrate cannot form. The observations of thick zones of large saturation at Mallik and Mt Elbert thus suggest that the primary control on these systems is the rate of transport of gaseous and aqueous phases, driven by the pressure sink at the base of the gas hydrate stability zone. A key finding of our project is the elucidation of ?capillary fracturing? as a dominant gas transport mechanism in low-permeability media. We initially investigate this phenomenon by means of grain-scale simulations in which we extended a discrete element mechanics code (PFC, by Itasca) to incorporate the dynamics of first singlephase and then multiphase flow. A reductionist model on a square lattice allows us to determine some of the fundamental dependencies of the mode of gas invasion (capillary fingering, viscous fingering, and fracturing) on the parameters of the system. We then show that the morphology of the gas-invaded region exerts a fundamental control on the fabric of methane hydrate formation, and on the overpressures caused by methane hydrate dissociation. We demonstrate the existence of the different invasion regimes by means of controlled laboratory experiments in a radial cell. We collapse the behavior in the form of a phase diagram fully characterized by two dimensionless groups: a modified capillary number and a ?fracturing number? that reflects the balance between the pressure forces that act to open conduits in the granular pack, and frictional forces that resist it. We use all this small-scale knowledge to propose simple mechanistic models of gas migration and hydrate formation at the geologic bed scale. We propose that methane transport in lake and oceanic sediments is controlled by dynamic conduits, which dilate and release gas as the falling hydrostatic pressure reduces the effective stress below the tensile strength of the sediments. We test our model against a four-month record of hydrostatic load and methane flux in Upper Mystic Lake, Mass., USA, and show that it captures the complex episodicity of methane ebullition. Our quantitative conceptualization opens the door to integrated modeling of methane transport to constrain global methane release from lakes and other methane-rich sediment systems, and to assess its climate feedbacks.« less

Potential for ground-water contamination from movement of wastewater through the unsaturated zone, upper Mojave River Basin, California

USGS Publications Warehouse

Umari, A.M.; Martin, P.M.; Schroeder, R.A.; Duell, L.F.; Fay, R.G.

1993-01-01

Septic-tank wastewater disposed in 30-foot-deep seepage pits (dry wells) at 46,000 residences is estimated to equal 18 percent of the natural recharge to the sole-source aquifer in the rapidly developing upper Mojave River Basin (Victor Valley) in the high desert northeast of Los Angeles. Vertical rates of movement of the wastewater wetting front through the unsaturated zone at three newly occupied residences ranged from 0.07 to 1.0 foot per day. These rates translate to traveltimes of several months to several years for the wastewater wetting front to reach the water table and imply that wastewater from many disposal systems already has reached the water table, which averages about 150 feet below land surface in the Victor Valley. As wastewater percolates from seepage pits into the adjacent unsaturated zone, the nitrogen present in reduced form is rapidly converted to nitrate. Analyses on soil-core extracts and soil moisturefrom suction lysimeters installed beneath the seepage pits at eight residences showed that nitrate concentrations and nitrate/ chloride ratios generally become lower with increasing depth. The intervals of greatest decline seemed to coincide with finer soil texture or were near the water table. Nitrate-reducing bacteria were tested for and found to be present in soil cores from two residences. Sparse nitrogen-15 data from suction lysimeters at one of these residences, where thenitrate concentration decreased by about one-half at a depth of 200 feet, indicate that the nitrate decline was accompanied by nitrogen-15 enrichment in the residual nitrate with an isotope-separation factor of about -10 permil. Despite the potential input of abundant nitrogen with the domestic wastewater recharge, nitrate concentrations in the area's ground water are generally low. The absence of high nitrate concentrations in the ground water is consistent with the existence of denitrification, a microbial nitrogen-removal mechanism, as wastewater moves through the thick unsaturated zone and mixes with the ground water. The observed low nitrate concentrations also could be explained by a dilution by vertical mixing in the saturated zone and retention of the wastewater in the unsaturated zone. Results of a single-cell mixing model that allows nitrate from wastewater to be mixedinstantaneously with the underlying ground water suggest that measurable increases in nitrate concentration should be expected within 5 to 10 years after wastewater reaches the water table if the mixing depth is less than 100 feet. Although high fecal-coliform densities were measured in wastewater from septic tanks and seepage pits, removal of these enteric bacteria in the unsaturated zone is very effective, as was indicated by their absence in soil only a few feet from the seepage pits. In testing for organic priority pollutants in wastewater, 17 of 85 compounds were detected. Most compounds detected were present in low concentrations, except at one residence where the concentration of three compounds exceeded 100 micrograms per liter. These high concentrations may be a consequence of disposal practices unique to this residence. Extractable organic priority pollutants were not found in any soil cores taken adjacent to seepage pits and, therefore, are not of concern.

Exploratory drilling and aquifer testing at the Kipahulu District, Haleakala National Park, Maui, Hawaii

USGS Publications Warehouse

Souza, W.R.

1983-01-01

An exploratory well, located at 388 feet above sea level in Kipahulu Valley on Maui, Hawaii, was completed and tested in October 1980. The 410-foot well penetrates a series of very dense basaltic lava flows of the Hana Formation. At an elevation of 10 feet above mean sea level, the well penetrated a water-bearing zone of permeable basaltic rock. Water from this zone had a head of about 76 feet above sea level. In October of 1980, the well was pump tested for 9 hours at various discharge rates up to 350 gallons per minute with a maximum drawdown of about 12 feet. Based on the test data, the well should produce water at a rate of 200 gallons per minute with a drawdown of less than 3 feet. The water level in the well was continuously monitored from October 1980 to mid-November 1981, during which period a maximum decline of 20 feet was recorded. Water level fluctuations in the well can be correlated to the flow in nearby Palikea Stream. The long-term water level in the well should stabilize at about 75 feet above sea level. Water quality was excellent. The total dissolved-solids content was 49 milligrams per liter and the chloride content was 4.2 milligrams per liter. (USGS)

Fast ground-water mixing and basal recharge in an unconfined, alluvial aquifer, Konza LTER Site, Northeastern Kansas

USGS Publications Warehouse

Macpherson, G.L.; Sophocleous, M.

2004-01-01

Ground-water chemistry and water levels at three levels in a well nest were monitored biweekly for two and a half years in a shallow unconfined floodplain aquifer in order to study the dynamics of such shallow aquifers. The aquifer, in northeastern Kansas, consists of high porosity, low hydraulic conductivity fine-grained sediments dominated by silt and bounded by fractured limestone and shale bedrock. Results show that the aquifer underwent chemical stratification followed by homogenization three times during the study period. The length of time between maximum stratification and complete homogenization was 3-5 months. The chemical parameters most useful for demonstrating the mixing trends were dissolved nitrate and sulfate. Higher nitrate concentrations were typical of unsaturated zone water and were sourced from fertilizer applied to the cultivated fields on the floodplain. Variations in sulfate concentrations are attributed to dissolution of rare gypsum in limestone bedrock and variable evapoconcentration in the unsaturated zone. The mixing of three chemically different waters (entrained, unsaturated-zone water; water entering the base of the floodplain aquifer; and water in residence before each mixing event) was simulated. The resident water component for each mixing event was a fixed composition based on measured water chemistry in the intermediate part of the aquifer. The entrained water composition was calculated using a measured composition of the shallow part of the aquifer and measurements of soil-water content in the unsaturated zone. The incoming basal water composition and the fractions of each mixing component were fitted to match the measured chemistry at the three levels in the aquifer. A conceptual model for this site explains: (1) rapid water-level rises, (2) water-chemistry changes at all levels in the aquifer coincident with the water-level rises, (3) low measured hydraulic conductivity of the valley fill and apparent lack of preferential flow pathways, (4) minuscule amounts of unsaturated-zone recharge, and (5) dissolved oxygen peaks in the saturated zone lagging water-level peaks. We postulate that rainfall enters fractures in bedrock adjacent to the floodplain. This recharge water moves rapidly through the fractured bedrock into the base of the floodplain aquifer. The recharge event through the bedrock causes a rapid rise in water level in the floodplain aquifer, and the chemistry of the deepest water in the floodplain aquifer changes at that time. The rising water also entrains slow-moving, nitrate-rich, unsaturated-zone water, altering the chemistry of water in the shallow part of the aquifer. Vertical chemical stratification in the aquifer is thus created by the change in water chemistry in the upper and lower parts of the saturated zone. As the water level begins to decline, the aquifer undergoes mixing that eventually results in homogeneous water chemistry. The rise in water level from the recharge event also displaces gas from the unsaturated zone that is then replaced as the water level declines following the recharge event. This new, oxygen-rich vadose-zone air equilibrates rapidly with saturated-zone water, resulting in a dissolved oxygen pulse in the ground water that peaks one-half to 2 months after the water-level peak. This oxygen pulse subsequently declines over a period of 2-6 months. ?? 2003 Elsevier B.V. All rights reserved.

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas

USGS Publications Warehouse

Clark, Allan K.; Golab, James A.; Morris, Robert R.

2016-11-28

During 2014–16, the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, documented the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas. The Edwards and Trinity aquifers are major sources of water for agriculture, industry, and urban and rural communities in south-central Texas. Both the Edwards and Trinity are classified as major aquifers by the State of Texas.The purpose of this report is to present the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Tex. The report includes a detailed 1:24,000-scale hydrostratigraphic map, names, and descriptions of the geology and hydrostratigraphic units (HSUs) in the study area.The scope of the report is focused on geologic framework and hydrostratigraphy of the outcrops and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Tex. In addition, parts of the adjacent upper confining unit to the Edwards aquifer are included.The study area, approximately 866 square miles, is within the outcrops of the Edwards and Trinity aquifers and overlying confining units (Washita, Eagle Ford, Austin, and Taylor Groups) in northern Bexar and Comal Counties, Tex. The rocks within the study area are sedimentary and range in age from Early to Late Cretaceous. The Miocene-age Balcones fault zone is the primary structural feature within the study area. The fault zone is an extensional system of faults that generally trends southwest to northeast in south-central Texas. The faults have normal throw, are en echelon, and are mostly downthrown to the southeast.The Early Cretaceous Edwards Group rocks were deposited in an open marine to supratidal flats environment during two marine transgressions. The Edwards Group is composed of the Kainer and Person Formations. Following tectonic uplift, subaerial exposure, and erosion near the end of Early Cretaceous time, the area of present-day south-central Texas was again submerged during the Late Cretaceous by a marine transgression resulting in deposition of the Georgetown Formation of the Washita Group.The Early Cretaceous Edwards Group, which overlies the Trinity Group, is composed of mudstone to boundstone, dolomitic limestone, argillaceous limestone, evaporite, shale, and chert. The Kainer Formation is subdivided into (bottom to top) the basal nodular, dolomitic, Kirschberg Evaporite, and grainstone members. The Person Formation is subdivided into (bottom to top) the regional dense, leached and collapsed (undivided), and cyclic and marine (undivided) members.Hydrostratigraphically the rocks exposed in the study area represent a section of the upper confining unit to the Edwards aquifer, the Edwards aquifer, the upper zone of the Trinity aquifer, and the middle zone of the Trinity aquifer. The Pecan Gap Formation (Taylor Group), Austin Group, Eagle Ford Group, Buda Limestone, and Del Rio Clay are generally considered to be the upper confining unit to the Edwards aquifer.The Edwards aquifer was subdivided into HSUs I to VIII. The Georgetown Formation of the Washita Group contains HSU I. The Person Formation of the Edwards Group contains HSUs II (cyclic and marine members [Kpcm], undivided), III (leached and collapsed members [Kplc,] undivided), and IV (regional dense member [Kprd]), and the Kainer Formation of the Edwards Group contains HSUs V (grainstone member [Kkg]), VI (Kirschberg Evaporite Member [Kkke]), VII (dolomitic member [Kkd]), and VIII (basal nodular member [Kkbn]).The Trinity aquifer is separated into upper, middle, and lower aquifer units (hereinafter referred to as “zones”). The upper zone of the Trinity aquifer is in the upper member of the Glen Rose Limestone. The middle zone of the Trinity aquifer is formed in the lower member of the Glen Rose Limestone, Hensell Sand, and Cow Creek Limestone. The regionally extensive Hammett Shale forms a confining unit between the middle and lower zones of the Trinity aquifer. The lower zone of the Trinity aquifer consists of the Sligo and Hosston Formations, which do not crop out in the study area.The upper zone of the Trinity aquifer is subdivided into five informal HSUs (top to bottom): cavernous, Camp Bullis, upper evaporite, fossiliferous, and lower evaporite. The middle zone of the Trinity aquifer is composed of the (top to bottom) Bulverde, Little Blanco, Twin Sisters, Doeppenschmidt, Rust, Honey Creek, Hensell, and Cow Creek HSUs. The underlying Hammett HSU is a regional confining unit between the middle and lower zones of the Trinity aquifer. The lower zone of the Trinity aquifer is not exposed in the study area.Groundwater recharge and flow paths in the study area are influenced not only by the hydrostratigraphic characteristics of the individual HSUs but also by faults and fractures and geologic structure. Faulting associated with the Balcones fault zone (1) might affect groundwater flow paths by forming a barrier to flow that results in water moving parallel to the fault plane, (2) might affect groundwater flow paths by increasing flow across the fault because of fracturing and juxtaposing porous and permeable units, or (3) might have no effect on the groundwater flow paths.The hydrologic connection between the Edwards and Trinity aquifers and the various HSUs is complex. The complexity of the aquifer system is a combination of the original depositional history, bioturbation, primary and secondary porosity, diagenesis, and fracturing of the area from faulting. All of these factors have resulted in development of modified porosity, permeability, and transmissivity within and between the aquifers. Faulting produced highly fractured areas that have allowed for rapid infiltration of water and subsequently formed solutionally enhanced fractures, bedding planes, channels, and caves that are highly permeable and transmissive. The juxtaposition resulting from faulting has resulted in areas of interconnectedness between the Edwards and Trinity aquifers and the various HSUs that form the aquifers.

Iron Isotope Fractionation in the Bushveld Igneous Complex Provide Insight into Fractional Crystallization

NASA Astrophysics Data System (ADS)

Rios, K. L.; Feineman, M. D.; Bybee, G. M.

2016-12-01

Dated at 2.056 Ga and encompassing an estimated 65,000 km2 in surface area and 650,000 km3 in volume the Bushveld Igneous Complex in South Africa contains the largest and most unique layered mafic intrusion in the world. It contains 80-90% of the world's minable platinum group elements. Scientists are interested in understanding the origin of this intrusion due to its massive size, unique assemblage of minerals, and strongly zoned stratigraphy. Iron isotopes may help us to understand the roles of partial mantle melting and fractional crystallization in magma genesis and differentiation. For example, it may be possible to determine what role fractional crystallization of oxides and sulfides played in the formation of the Rustenburg Layered Suite (RLS) by comparing δ56Fe in samples from the Lower, Critical, Main and Upper Zones. The use of MC-ICPMS has made it more routine to study the fractionation of stable iron isotopes in natural systems; however, this technique has only been applied in a few studies of the RLS, mostly restricted to the Upper Main and Upper Zones. In this study δ56Fe was determined in Upper Zone magnetite, Critical Zone chromitite and Critical Zone sulfides using MC-ICP-MS. Previous research has shown that early crystallizing mafic phases incorporate the lighter 54Fe isotope leaving a residual magma with a higher δ56Fe value. Therefore, if the Upper Zone magma represents a high-degree differentiate of the parental Bushveld magma, then magmas from the Upper Zone would be expected to have a higher δ56Fe than magmas contributing to the Lower, Critical and Main Zones. The results of this experiment were indeed consistent with this hypothesis. The δ56Fe values recorded for the three sample types were: magnetite 0.19 ±0.03‰; sulfides -0.45 ±0.03‰ to -0.81 ±0.03‰; and chromitite 0.03 ±0.05‰. The sulfides of the Critical Zone are isotopically lighter than would be predicted based on equilibrium sulfide-melt fractionation, if the parental melt of the Critical Zone were in equilibrium with previously published whole rock data for Upper Zone. This is consistent with interpretations of the Upper Zone as a high degree differentiate of the Bushveld Parental Magma.

Geologic setting, sedimentary architecture, and paragenesis of the Mesoproterozoic sediment-hosted Sheep Creek Cu-Co-Ag deposit, Helena embayment, Montana

USGS Publications Warehouse

Graham, Garth; Hitzman, Murray W.; Zieg, Jerry

2012-01-01

The northern margin of the Helena Embayment contains extensive syngenetic to diagenetic massive pyrite horizons that extend over 25 km along the Volcano Valley-Buttress fault zone and extend up to 8 km basinward (south) within the Mesoproterozoic Newland Formation. The Sheep Creek Cu-Co deposit occurs within a structural block along a bend in the fault system, where replacement-style chalcopyrite mineralization is spatially associated mostly with the two stratigraphically lowest massive pyrite zones. These mineralized pyritic horizons are intercalated with debris flows derived from synsedimentary movement along the Volcano Valley-Buttress fault zone. Cominco American Inc. delineated a geologic resource of 4.5 Mt at 2.5% Cu and 0.1% Co in the upper sulfide zone and 4 Mt at 4% Cu within the lower sulfide zone. More recently, Tintina Resources Inc. has delineated an inferred resource of 8.48 Mt at 2.96% Cu, 0.12% Co, and 16.4 g/t Ag in the upper sulfide zone. The more intact upper sulfide zone displays significant thickness variations along strike thought to represent formation in at least three separate subbasins. The largest accumulation of mineralized sulfide in the upper zone occurs as an N-S–trending body that thickens southward from the generally E trending Volcano Valley Fault and probably occupies a paleograben controlled by normal faults in the hanging wall of the Volcano Valley Fault. Early microcrystalline to framboidal pyrite was accompanied by abundant and local barite deposition in the upper and lower sulfide zones, respectively. The sulfide bodies underwent intense (lower sulfide zone) to localized (upper sulfide zone) recrystallization and overprinting by coarser-grained pyrite and minor marcasite that is intergrown with and replaces dolomite. Silicification and paragenetically late chalcopyrite, along with minor tennantite in the upper sulfide zone, replaces fine-grained pyrite, barite, and carbonate. The restriction of chalcopyrite to inferred synsedimentary E- and northerly trending faults and absence of definitive zonation with respect to the Laramide Volcano Valley Fault in the lower sulfide zone suggest a diagenetic age related to basin development for the Sheep Creek Cu-Co-Ag deposit.

Preliminary hydrogeologic investigation of the Maxey Flats radioactive waste burial site, Fleming County, Kentucky

USGS Publications Warehouse

Zehner, Harold H.

1979-01-01

Burial trenches at the Maxey Flats radioactive waste burial site , Fleming County, Ky., cover an area of about 0.03 square mile, and are located on a plateau, about 300 to 400 feet above surrounding valleys. Although surface-water characteristics are known, little information is available regarding the ground-water hydrology of the Maxey Flats area. If transport of radionuclides from the burial site were to occur, water would probably be the principal mechanism of transport by natural means. Most base flow in streams around the burial site is from valley alluvium, and from the mantle of regolith, colluvium, and soil partially covering adjacent hills. Very little base flow is due to ground-water flow from bedrock. Most water in springs is from the mantle, rather than from bedrock. Rock units underlying the Maxey Flats area are, in descending order, the Nancy and Farmers Members of the Borden Formation, Sunbury, Bedford, and Ohio Shales, and upper part of the Crab Orchard Formation. These units are mostly shales, except for the Farmers Member, which is mostly sandstone. Total thickness of the rocks is about 320 feet. All radioactive wastes are buried in the Nancy Member. Most ground-water movement in bedrock probably occurs in fractures. The ground-water system at Maxey Flats is probably unconfined, and recharge occurs by (a) infiltration of rainfall into the mantle, and (b) vertical, unsaturated flow from the saturated regolith on hilltops to saturated zones in the Farmers Member and Ohio Shale. Data are insufficient to determine if saturated zones exist in other rock units. The upper part of the Crab Orchard Formation is probably a hydrologic boundary, with little ground-water flow through the formation. (USGS)

Potentiometric surface of the upper Floridan Aquifer in the St. Johns River Water Management District and vicinity, Florida, May 1994

USGS Publications Warehouse

Schiffer, D.M.; O'Reilly, A. M.; Phelps, G.G.; Bradner, L.A.; Halford, K.J.; Spechler, R.M.

1994-01-01

This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1994. The map is based on water-level measurements made at approximately 1,000 wells and several springs. Data on the map were contoured using 5-foot contour intervals in most areas. The potentiometric surface of this karstic aquifer generally reflects land surface topography. Potentiometric surface highs often correspond to topographic highs, which are areas of surficial recharge to the Upper Floridan aquifer. Springs within topographic lows along with areas of more diffuse upward leakage are natural zones of discharge. Municipal, agricultural, and industrial withdrawals have lowered the potentiometric surface in some areas. The potentiometric surface ranged from 125 feet above sea level in Polk County to 32 feet below sea level in Nassau County. Water levels in May 1994 generally were 0 to 3 feet lower than those measured in May 1993. Water levels in May 1994 in northeast Florida generally were 0 to 3 feet higher than in September 1993, except in the lower St. Johns River basin, where water levels were 0 to 4 feet lower than in September 1993. In the rest of the mapped area, water levels in May 1994 generally were 0 to 4 feet lower than those measured in September 1993.

Factors affecting ground-water exchange and catchment size for Florida lakes in mantled karst terrain

USGS Publications Warehouse

Lee, Terrie Mackin

2002-01-01

In the mantled karst terrain of Florida, the size of the catchment delivering ground-water inflow to lakes is often considerably smaller than the topographically defined drainage basin. The size is determined by a balance of factors that act individually to enhance or diminish the hydraulic connection between the lake and the adjacent surficial aquifer, as well as the hydraulic connection between the surficial aquifer and the deeper limestone aquifer. Factors affecting ground-water exchange and the size of the ground-water catchment for lakes in mantled karst terrain were examined by: (1) reviewing the physical and hydrogeological characteristics of 14 Florida lake basins with available ground-water inflow estimates, and (2) simulating ground-water flow in hypothetical lake basins. Variably-saturated flow modeling was used to simulate a range of physical and hydrogeologic factors observed at the 14 lake basins. These factors included: recharge rate to the surficial aquifer, thickness of the unsaturated zone, size of the topographically defined basin, depth of the lake, thickness of the surficial aquifer, hydraulic conductivity of the geologic units, the location and size of karst subsidence features beneath and onshore of the lake, and the head in the Upper Floridan aquifer. Catchment size and the magnitude of ground-water inflow increased with increases in recharge rate to the surficial aquifer, the size of the topographically defined basin, hydraulic conductivity in the surficial aquifer, the degree of confinement of the deeper Upper Floridan aquifer, and the head in the Upper Floridan aquifer. The catchment size and magnitude of ground-water inflow increased with decreases in the number and size of karst subsidence features in the basin, and the thickness of the unsaturated zone near the lake. Model results, although qualitative, provided insights into: (1) the types of lake basins in mantled karst terrain that have the potential to generate small and large amounts of ground-water inflow, and (2) the location of ground-water catchments that could be managed to safeguard lake water quality. Knowledge of how ground-water catchments are related to lakes could be used by water-resource managers to recommend setback distances for septic tank drain fields, agricultural land uses, and other land-use practices that contribute nutrients and major ions to lakes.

Storage and recycling of water and carbon dioxide in the earth

NASA Technical Reports Server (NTRS)

Wood, Bernard J.

1994-01-01

The stabilities and properties of water- and carbon-bearing phases in the earth have been determined from phase equilibrium measurements, combined with new data on the equations of state of water, carbon dioxide, carbonates and hydrates. The data have then been used to predict the fate of calcite and hydrous phases in subducting oceanic lithosphere. From the compositions of MORB's one can estimate concentrations of water and carbon of around 200 ppm and 80 ppm respectively in the upper mantle. Lower mantle estimates are very uncertain, but 1900 ppm water and 2000 ppm C are plausible concentrations. Measurements of the density of supercritical water to 3 GPa demonstrate that this phase is less compressible than anticipated from the equations of state of Haar et al. or Saul and Wagner and is closer to predictions based on molecular dynamics simulations. Conversely, fugacity measurements on carbon dioxide to 7 GPa show that this fluid is more compressible than predicted from the MRK equation of state. The results imply that hydrates are relatively more stable and carbonates less stable at pressures greater than 5 GPa than would be predicted from simple extrapolation of the low pressure data. Nevertheless, carbonates remain extremely refractory phases within both the upper and lower mantle.

Interpretation of geophysical logs, aquifer tests, and water levels in wells in and near the North Penn Area 7 Superfund site, Upper Gwynedd Township, Montgomery County, Pennsylvania, 2000-02

USGS Publications Warehouse

Senior, Lisa A.; Cinotto, Peter J.; Conger, Randall W.; Bird, Philip H.; Pracht, Karl A.

2005-01-01

Ground water in the vicinity of various industrial facilities in Upper Gwynedd Township and Lansdale Borough, Montgomery County, Pa., is contaminated with various volatile organic compounds (VOCs). The 2-square-mile area was placed on the National Priorities List as the North Penn Area 7 Superfund site by the U.S. Environmental Protection Agency (USEPA) in 1989. The U.S. Geological Survey (USGS) conducted geophysical logging, aquifer testing, water-level monitoring, and streamflow measurements in the vicinity of North Penn Area 7 beginning autumn 2000 to assist the USEPA in developing an understanding of the hydrogeologic framework in the area as part of the USEPA Remedial Investigation. The study area is underlain by Triassic and Jurassic-age sandstones, siltstones, and shales of the Lockatong Formation and the Brunswick Group. Regionally, these rocks strike northeast and dip to the northwest. The sequence of rocks form a fractured-sedimentary-rock aquifer that acts as a set of confined to partially confined layered aquifers of differing permeabilities. The aquifers are recharged by precipitation and discharge to streams and wells. The Wissahickon Creek headwaters are less than 1 mile northeast of the study area, and this stream flows southwest to bisect North Penn Area 7. Ground water is pumped in the vicinity of North Penn Area 7 for industrial use and public supply. The USGS collected geophysical logs for 16 wells that ranged in depth from 50 to 623 feet. Aquifer-interval-isolation testing was done in 9 of the 16 wells, for a total of 30 zones tested. A multiple-well aquifer test was conducted by monitoring the response of 14 wells to pumping a 600-ft deep production well in February and March 2002. In addition, water levels were monitored continuously in three wells in the area and streamflow was measured quarterly at two sites on Wissahickon Creek from December 2000 through September 2002. Geophysical logging identified water-bearing zones associated with high-angle fractures and bedding-plane openings throughout the depth of the boreholes. Heatpulse-flowmeter measurements under nonpumping, ambient conditions indicated that borehole flow, where detected, was in the upward direction in three of the eight wells and in the downward direction in three wells. In two wells, both upward and downward flow were measured. Heatpulse-flowmeter measurements under pumping conditions were used to identify the most productive intervals in wells. Correlation of natural-gamma-ray and single-point-resistance logs indicated that bedding in the area probably strikes about 40 degrees northeast and dips from 6 to 7 degrees northwest. Aquifer intervals isolated by inflatable packers in wells were pumped to test productivity and to collect samples to determine chemical quality of water produced from the interval. Interval-isolation testing confirmed the presence of vertical hydraulic gradients indicated by heatpulse-flowmeter measurements. The specific capacities of isolated intervals ranged over two orders of magnitude, from 0.02 to more than 3.6 gallons per minute per foot. Intervals adjacent to isolated pumped intervals showed little response to pumping the isolated zone. The presence of vertical hydraulic gradients and lack of adjacent-interval response to pumping in isolated intervals indicate a limited degree of vertical hydraulic connection between the aquifer intervals tested. Concentrations of most VOC contaminants generally were highest in well-water samples from the shallowest isolated intervals, with some exceptions. Trichloroethylene, cis-1,2-dichloroethylene, and toluene were the most frequently detected VOCs, with maximum concentrations of greater than 340, 680, and greater than 590 micrograms per liter, respectively. Results of the aquifer test with multiple observation wells showed that water levels in 4 of the 14 wells declined in response to pumping. The four wells that responded to pumping are either along str

High-speed motion picture camera experiments of cavitation in dynamically loaded journal bearings

NASA Technical Reports Server (NTRS)

Jacobson, B. O.; Hamrock, B. J.

1982-01-01

A high-speed camera was used to investigate cavitation in dynamically loaded journal bearings. The length-diameter ratio of the bearing, the speeds of the shaft and bearing, the surface material of the shaft, and the static and dynamic eccentricity of the bearing were varied. The results reveal not only the appearance of gas cavitation, but also the development of previously unsuspected vapor cavitation. It was found that gas cavitation increases with time until, after many hundreds of pressure cycles, there is a constant amount of gas kept in the cavitation zone of the bearing. The gas can have pressures of many times the atmospheric pressure. Vapor cavitation bubbles, on the other hand, collapse at pressures lower than the atmospheric pressure and cannot be transported through a high-pressure zone, nor does the amount of vapor cavitation in a bearing increase with time. Analysis is given to support the experimental findings for both gas and vapor cavitation.

Hydrology of the Upper Capibaribe Basin, Pernambuco, Brazil - A reconnaissance in an Area of Crystalline Rocks

USGS Publications Warehouse

Chada Filho, Luiz Goncalves; Dias Pessoa, Mario; Sinclair, William C.

1966-01-01

The upper Capibaribe basin is the western three-fourths, approximately, of the valley of the river that empties into the Atlantic Ocean at Recife, the capital of the State of Pernambuco, Brazil. It is the part of the drainage basin that is within the Drought Polygon of northeast Brazil, and it totals about 5,400 square kilometers. It receives relatively abundant precipitation in terms of the annual average, yet is regarded as hot subhumid to semiarid because the precipitation is uneven from year to year and place to place. The dependable water supply, therefore, is small. The basin has water, which could be put to better use than at present, but the opportunities for augmenting the usable supply are not great. The streams are intermittent and therefore cannot be expected to fill surface reservoirs and to keep them filled. The ground-water reservoirs have small capacity--quickly filled and quickly drained. A rough estimate based on the records for 1964 suggests that, of 4,700 million cubic meters of precipitation in the upper Capibaribe basin, 2,700 million cubic meters (57 percent) left the basin as runoff and 2,000 million cubic meters {43 percent) went into underground storage or was evaporated or transpired. The bedrock of the upper Capibaribe basin is composed of granite, gneiss, schist, and other varieties of crystalline rocks, which have only insignificant primary permeability. They are permeable mainly where fractured. The principal fracture zones, fortunately, are in the valleys, where water accumulates and can feed into them, but the volume of fractured rock is small in relation to the basin as a whole. A well in a large water-filled fracture zone may yield up to 20,000 liters per hour, but the average well yields less than one-fourth this amount, and some wells yield none. The saprolite, or weathered rock, is many meters thick at some places especially in the eastern half of the upper Capibaribe basin. It contains water locally, but ordinarily will yield only small quantities to wells. The alluvium probably is the most productive aquifer in the basin, but is limited to narrow bands along the rivers that generally are no more than a few hundred meters wide and 5 meters thick. The alluvium contains variable amounts of silty sand capable of yielding small to moderate quantities of water to wells. Wells driven or dug into the alluvium could solve many small water problems. The chemical quality of the water in the upper Capibaribe basin ranges from good to bad and generally presents a major problem that cannot be solved solely by applying geological criteria. Mineralized water is widespread in the area, both in streams and underground, and .the choice of aquifers is small. All known aquifers contain, at one place or another, water that is mineralized, leaving no alternative for a natural supply of good-quality water. Although much of the available water is unsatisfactory for human consumption, it is generally acceptable for animals and therefore meets one of the principal water needs. Some of the ground water could be made potable by diluting it with rainwater, which could be collected during rainy seasons and temporarily stored in cisterns or reservoirs.

Storage of treated sewage effluent and stormwater in a saline aquifer, Pinellas Peninsula, Florida

USGS Publications Warehouse

Rosenshein, J.S.; Hickey, J.J.

1977-01-01

The Pinellas Peninsula, an area of 750 square kilometres (290 square miles) in coastal west-central Florida, is a small hydrogeologic replica of Florida. Most of the Peninsula's water supply is imported from well fields as much as 65 kilometres (40 miles) inland. Stresses on the hydrologic environment of the Peninsula and on adjacent water bodies, resulting from intensive water-resources development and waste discharge, have resulted in marked interest in subsurface storage of waste water (treated effluent and untreated storm water) and in future retrieval of the stored water for nonpotable use. If subsurface storage is approved by regulatory agencies, as much as 265 megalitres per day (70 million gallons a day) of waste water could be stored underground within a few years, and more than 565 megalitres per day (150 million gallons a day) could be stored in about 25 years. This storage would constitute a large resource of nearly fresh water in the saline aquifers underlying about 520 square kilometres (200 square miles) of the Peninsula.The upper 1,060 metres (3,480 feet) of the rock column underlying four test sites on the Pinellas Peninsula have been explored. The rocks consist chiefly of limestone and dolomite. Three moderately to highly transmissive zones, separated by leaky confining beds, (low permeability limestone) from about 225 to 380 metres (740 to 1,250 feet) below mean sea level, have been identified in the lower part of the Floridan aquifer in the Avon Park Limestone. Results of withdrawal and injection tests in Pinellas County indicate that the middle transmissive zone has the highest estimated transmissivity-about 10 times other reported values. The chloride concentration of water in this zone, as well as in the two other transmissive zones in the Avon Park Limestone in Pinellas Peninsula, is about 19,000 milligrams per litre. If subsurface storage is approved and implemented, this middle zone probably would be used for storage of the waste water and the zone would become the most extensively used in Florida for this purpose.

South-Tibetan partially molten batholiths: geophysical characterization and petrological assessment of their origin

NASA Astrophysics Data System (ADS)

Hetényi, G.; Pistone, M.; Nabelek, P. I.; Baumgartner, L. P.

2017-12-01

Zones of partial melt in the middle crust of Lhasa Block, Southern Tibet, have been geophysically observed as seismically reflective "bright spots" in the past 20 years. These batholiths bear important relevance for geodynamics as they serve as the principal observation at depth supporting channel-flow models in the Himalaya-Tibet orogen. Here we assess the spatial abundance of and partial melt volume fraction within these crustal batholiths, and establish lower and upper estimate bounds using a joint geophysical-petrological approach.Geophysical imaging constrains the abundance of partial melt zones to 5.6 km3 per surface-km2 on average (minimum: 3.1 km3/km2, maximum: 7.6 km3/km2 over the mapped area). Physical properties detected by field geophysics and interpreted by laboratory measurements constrain the amount of partial melt to be between 5 and 26 percent.We evaluate the compatibility of these estimates with petrological modeling based on geotherms, crustal bulk rock compositions and water contents consistent with the Lhasa Block. These simulations determine: (a) the physico-chemical conditions of melt generation at the base of the Tibetan crust and its transport and emplacement in the middle crust; (b) the melt percentage produced at the source, transported and emplaced to form the observed "bright spots". Two main mechanisms are considered: (1) melting induced by fluids produced during mineral dehydration reactions in the underthrusting Indian lower crust; (2) dehydration-melting reactions caused by heating within the Tibetan crust. We find that both mechanisms demonstrate first-order match in explaining the formation of the partially molten "bright spots". Thermal modelling shows that the Lhasa Block batholiths have only small amounts of melt and only for geologically short times (<4.5 Myr), if not continuously fed. This, together with their small size compared to the Tibetan Plateau, suggests that these partially molten zones are ephemeral and local features of the geodynamic evolution. Their transience excludes both long-distance and long-lasting channel flow transport in Tibet.

Description of borehole geophysical and geologist logs, Berks Sand Pit Superfund Site, Longswamp Township, Berks County, Pennsylvania

USGS Publications Warehouse

Low, Dennis J.; Conger, Randall W.

2003-01-01

Between October 2002 and January 2003, geophysical logging was conducted in six boreholes at the Berks Sand Pit Superfund Site, Longswamp Township, Berks County, Pa., to determine (1) the waterproducing zones, water-receiving zones, zones of vertical borehole flow, orientation of fractures, and borehole and casing depth; and (2) the hydraulic interconnection between the six boreholes and the site extraction well. The boreholes range in depth from 61 to 270 feet. Geophysical logging included collection of caliper, natural-gamma, single-point-resistance, fluid-temperature, fluid-flow, and acoustic-televiewer logs. Caliper and acoustic-televiewer logs were used to locate fractures, joints, and weathered zones. Inflections on fluid-temperature and single-point-resistance logs indicated possible water-bearing fractures, and flowmeter measurements verified these locations. Single-point-resistance, natural-gamma, and geologist logs provided information on stratigraphy. Flowmeter measurements were conducted while the site extraction well was pumping and when it was inactive to determine the hydraulic connections between the extraction well and the boreholes.Borehole geophysical logging and heatpulse flowmetering indicate active flow in the boreholes. Two of the boreholes are in ground-water discharge areas, two boreholes are in ground-water recharge areas, and one borehole is in an intermediate regime. Flow was not determined in one borehole. Heatpulse flowmetering, in conjunction with the geologist logs, indicates highly weathered zones in the granitic gneiss can be permeable and effective transmitters of water, confirming the presence of a two-tiered ground-water-flow system. The effort to determine a hydraulic connection between the site extraction well and six logged boreholes was not conclusive. Three boreholes showed decreases in depth to water after pumping of the site extraction well; in two boreholes, the depth to water increased. One borehole was cased its entire depth and was not revisited after it was logged by the caliper log. Substantial change in flow rates or direction of borehole flow was not observed in any of the three wells logged with the heatpulse flowmeter when the site extraction well was pumping and when it was inactive.

Hydrogeologic framework, hydrology, and refined conceptual model of groundwater flow for Coastal Plain aquifers at the Standard Chlorine of Delaware, Inc. Superfund Site, New Castle County, Delaware, 2005-12

USGS Publications Warehouse

Brayton, Michael J.; Cruz, Roberto M.; Myers, Luke; Degnan, James R.; Raffensperger, Jeff P.

2015-01-01

The regional hydrogeologic framework indicates that the site is underlain by Coastal Plain sediments of the Columbia, Merchantville, and Potomac Formations. Two primary aquifers underlying the site, the Columbia and the upper Potomac, are separated by the Merchantville Formation confining unit. Local groundwater flow in the surficial (Columbia) aquifer is controlled by topography and generally flows northward and discharges to nearby surface water. Regional flow within the Potomac aquifer is towards the southeast, and is strongly influenced by major water withdrawals locally. Previous investigations at the site indicated that contaminants, primarily benzene and chlorinated benzene compounds, were present in the Columbia aquifer in most locations; however, there were only limited detections in the upper Potomac aquifer as of 2004. From 2005 through 2012, the USGS designed a monitoring network, assisted with exploratory drilling, collected data at monitoring wells, conducted geophysical surveys, evaluated water-level responses in wells during pumping of a production well, and evaluated major aquifer withdrawals. Data collected through these efforts were used to refine the local conceptual flow system. The refined conceptual flow system for the site includes: (a) identification of gaps in confining units in the study area, (b) identification and correlation of multiple water-bearing sand intervals within the upper Potomac Formation, (c) connections between groundwater and surface water, (d) connections between shallow and deeper groundwater, (e) new water-level (or potentiometric surface) maps and inferred flow directions, and (f) identification of major local pumping well influences. The implications of the revised conceptual flow system on the occurrence and movement of site contaminants are that the resulting detection of contaminants in the upper Potomac aquifer at specific well locations can be attributed primarily to either advective lateral transport, direct vertical contaminant transport, or a combination of vertical and lateral movement resulting from changes in water withdrawal rates over time.

Effect of aluminum, zinc, copper, and lead on the acid-base properties of water extracts from soils

NASA Astrophysics Data System (ADS)

Motuzova, G. V.; Makarychev, I. P.; Petrov, M. I.

2013-01-01

The potentiometric titration of water extracts from the upper horizons of taiga-zone soils by salt solutions of heavy metals (Pb, Cu, and Zn) showed that their addition is an additional source of the extract acidity because of the involvement of the metal ions in complexation with water-soluble organic substances (WSOSs). At the addition of 0.01 M water solutions of Al(NO3)3 to water extracts from soils, Al3+ ions are also involved in complexes with WSOSs, which is accompanied by stronger acidification of the extracts from the upper horizon of soddy soils (with a near-neutral reaction) than from the litter of bog-podzolic soil (with a strongly acid reaction). The effect of the Al3+ hydrolysis on the acidity of the extracts is insignificantly low in both cases. A quantitative relationship was revealed between the release of protons and the ratio of free Cu2+ ions to those complexed with WSOSs at the titration of water extracts from soils by a solution of copper salt.

Open Access Discovery of alunite in Cross crater, Terra Sirenum, Mars: Evidence for acidic, sulfurous waters

USGS Publications Warehouse

Ehlmann, Bethany L.; Swayze, Gregg A.; Milliken, Ralph E.; Mustard, John F.; Clark, Roger N.; Murchie, Scott L.; Breit, George N.; Wray, James J.; Gondet, Brigitte; Poulet, Francois; Carter, John; Calvin, Wendy M.; Benzel, William M.; Seelos, Kimberly D.

2016-01-01

Cross crater is a 65 km impact crater, located in the Noachian highlands of the Terra Sirenum region of Mars (30°S, 158°W), which hosts aluminum phyllosilicate deposits first detected by the Observatoire pour la Minéralogie, L’Eau, les Glaces et l’Activitié (OMEGA) imaging spectrometer on Mars Express. Using high-resolution data from the Mars Reconnaissance Orbiter, we examine Cross crater’s basin-filling sedimentary deposits. Visible/shortwave infrared (VSWIR) spectra from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show absorptions diagnostic of alunite. Combining spectral data with high-resolution images, we map a large (10 km × 5 km) alunite-bearing deposit in southwest Cross crater, widespread kaolin-bearing sediments with variable amounts of alunite that are layered in <10 m scale beds, and silica- and/or montmorillonite-bearing deposits that occupy topographically lower, heavily fractured units. The secondary minerals are found at elevations ranging from 700 to 1550 m, forming a discontinuous ring along the crater wall beneath darker capping materials. The mineralogy inside Cross crater is different from that of the surrounding terrains and other martian basins, where Fe/Mg-phyllosilicates and Ca/Mg-sulfates are commonly found. Alunite in Cross crater indicates acidic, sulfurous waters at the time of its formation. Waters in Cross crater were likely supplied by regionally upwelling groundwaters as well as through an inlet valley from a small adjacent depression to the east, perhaps occasionally forming a lake or series of shallow playa lakes in the closed basin. Like nearby Columbus crater, Cross crater exhibits evidence for acid sulfate alteration, but the alteration in Cross is more extensive/complete. The large but localized occurrence of alunite suggests a localized, high-volume source of acidic waters or vapors, possibly supplied by sulfurous (H2S- and/or SO2-bearing) waters in contact with a magmatic source, upwelling steam or fluids through fracture zones. The unique, highly aluminous nature of the Cross crater deposits relative to other martian acid sulfate deposits indicates acid waters, high water throughput during alteration, atypically glassy and/or felsic materials, or a combination of these conditions.

Geohydrology of the central Mesilla Valley, Dona Ana County, New Mexico

USGS Publications Warehouse

Wilson, Clyde A.; White, Robert R.

1984-01-01

Five large-capacity irrigation wells, with depths ranging from 370 to 686 feet, were drilled by the Elephant Butte Irrigation District between 1973 and 1975, in the Mesilla Valley about 7 miles south of Las Cruces, New Mexico. These were the first deep wells in the area, and their installation provided an opportunity to conduct extensive aquifer tests under relatively undisturbed conditions. The deep irrigation wells are perforated in the Santa Fe Group of Miocene to Pleistocene Age. The Santa Fe Group is composed of interfingering and alternating beds of clay, silt, sand, and small gravel. In the area of these wells, the upper part of the saturated zone contains slightly saline water to a depth of about 100 to 175 feet below the water table, underlain by a freshwater zone extending to depths greater than 1,200 feet. As water is pumped from the freshwater zone, leakage occurs from above and below the perforated interval. At one of the irrigation district wells, slightly saline water moved downward because of a lack of confining layers in the aquifer. At three other wells, the surface casing was not set deep enough and slightly saline water moved into the top of the perforations , downward in the casing, and into the freshwater part of the aquifer. (USGS)

Minimum distribution of subsea ice-bearing permafrost on the US Beaufort Sea continental shelf

USGS Publications Warehouse

Brothers, Laura L.; Hart, Patrick E.; Ruppel, Carolyn D.

2012-01-01

Starting in Late Pleistocene time (~19 ka), sea level rise inundated coastal zones worldwide. On some parts of the present-day circum-Arctic continental shelf, this led to flooding and thawing of formerly subaerial permafrost and probable dissociation of associated gas hydrates. Relict permafrost has never been systematically mapped along the 700-km-long U.S. Beaufort Sea continental shelf and is often assumed to extend to ~120 m water depth, the approximate amount of sea level rise since the Late Pleistocene. Here, 5,000 km of multichannel seismic (MCS) data acquired between 1977 and 1992 were examined for high-velocity (>2.3 km s−1) refractions consistent with ice-bearing, coarse-grained sediments. Permafrost refractions were identified along <5% of the tracklines at depths of ~5 to 470 m below the seafloor. The resulting map reveals the minimum extent of subsea ice-bearing permafrost, which does not extend seaward of 30 km offshore or beyond the 20 m isobath.

Well construction, lithology, and geophysical logs for boreholes in Bear Creek Valley near Oak Ridge, Tennessee

USGS Publications Warehouse

Bailey, Z.C.; Hanchar, D.W.

1988-01-01

Twenty-four wells were constructed at nine sites at Bear Creek Valley to provide geologic and hydrologic information. Lithologic samples and suits of geophysical logs were obtained from the deepest boreholes at six of the sites. Two of these boreholes at the base of Chestnut Ridge were completed in the Maynardville Limestone and two were completed in the Nolichucky Shale. Two boreholes along Pine Ridge were completed in the Rome Formation. Zones of similar lithology within a borehole were delineated from rock cutting refined by examination of geophysical logs. The contact between the Maynardville Limestone and Nolichucky Shale was identified in two of the boreholes. Fractures and cavities were readily identifiable on the acoustic-televiewer and caliper logs. Distinct water-bearing intervals were also identified from the temperature, fluid resistance, and resistivity logs. Depths at which the drilling encounterd a thrust were identified in two boreholes in the Rome Formation from both rock cutting and geophysical logs. (USGS)

High-Resolution P'P' Precursor Imaging of Nazca-South America Plate Boundary Zones and Inferences for Transition Zone Temperature and Composition

NASA Astrophysics Data System (ADS)

Gu, Y. J.; Schultz, R.

2013-12-01

Knowledge of upper mantle transition zone stratification and composition is highly dependent on our ability to efficiently extract and properly interpret small seismic arrivals. A promising high-frequency seismic phase group particularly suitable for a global analysis is P'P' precursors, which are capable of resolving mantle structures at vertical and lateral resolution of approximately 5 and 200 km, respectively, owing to their shallow incidence angle and small, quasi-symmetric Fresnel zones. This study presents a simultaneous analysis of SS and P'P' precursors based on deconvolution, Radon transform and depth migration. Our multi-resolution survey of the mantle near Nazca-South America subduction zone reveals both olivine and garnet related transitions at depth below 400 km. We attribute a depressed 660 to thermal variations, whereas compositional variations atop the upper-mantle transition zone are needed to explain the diminished or highly complex reflected/scattered signals from the 410 km discontinuity. We also observe prominent P'P' reflections within the transition zone, especially near the plate boundary zone where anomalously high reflection amplitudes result from a sharp (~10 km thick) mineral phase change resonant with the dominant frequency of the P'P' precursors. Near the base of the upper mantle, the migration of SS precursors shows no evidence of split reflections near the 660-km discontinuity, but potential majorite-ilmenite (590-640 km) and ilmenite-perovskite transitions (740-750 km) are identified based on similarly processed high-frequency P'P' precursors. At nominal mantle temperatures these two phase changes may be seismically indistinguishable, but colder mantle conditions from the descending Nazca plate, the presence of water and variable Fe contents may cause sufficient separation for a reliable analysis. In addition, our preliminary results provide compelling evidence for multiple shallow lower-mantle reflections (at ~800 km) along the elongated plate boundary zones of South America. Slab stagnation at the base of the transition zone could play a key role, though a proper interpretation of this finding would likely entail compositional (rather than strictly thermal) variations in the vicinity of the descending oceanic crust and lithosphere. Overall, the resolution and sensitivity differences between low/intermediate- S and high-frequency P wave reflections are key considerations toward reconciling seismic and mineralogical models of transition zone structure, both at the study location and worldwide.

Lateritic, supergene rare earth element (REE) deposits

USGS Publications Warehouse

Cocker, Mark D.

2014-01-01

Intensive lateritic weathering of bedrock under tropical or sub-tropical climatic conditions can form a variety of secondary, supergene-type deposits. These secondary deposits may range in composition from aluminous bauxites to iron and niobium, and include rare earth elements (REE). Over 250 lateritic deposits of REE are currently known and many have been important sources of REE. In southeastern China, lateritic REE deposits, known as ion-adsorption type deposits, have been the world’s largest source of heavy REE (HREE). The lateritized upper parts of carbonatite intrusions are being investigated for REE in South America, Africa, Asia and Australia, with the Mt. Weld deposit in Australia being brought into production in late 2012. Lateritic REE deposits may be derived from a wide range of primary host rocks, but all have similar laterite and enrichment profiles, and are probably formed under similar climatic conditions. The weathering profile commonly consists of a depleted zone, an enriched zone, and a partially weathered zone which overlie the protolith. Lateritic weathering may commonly extend to depths of 30 to 60 m. REE are mobilized from the breakdown of primary REE-bearing minerals and redeposited in the enriched zone deeper in the weathering horizon as secondary minerals, as colloids, or adsorbed on other secondary minerals. Enrichment of REE may range from 3 to 10 times that of the source lithology; in some instances, enrichment may range up to 100 times.

Evaluation of ground-water quality data from Kentucky

USGS Publications Warehouse

Sprinkle, C.L.; Davis, R.W.; Mull, D.S.

1983-01-01

The report reviews and summarizes 10,578 chemical analyses, from 2,362 wells and springs in Kentucky. These water-quality data were collected prior to September 30, 1981, and are available in computer files of the U.S. Geological Survey. The principal water-bearing rocks in Kentucky were combined into 10 major groups to aid in data summary preparation and general description of the ground-water quality of the State. Ground water in Kentucky is generally fresh near the outcrop of the rocks comprising the aquifer. Slightly saline to briny water occurs at variable depths beneath the freshwater. Preparation of quadrilinear diagrams revealed three principal geochemical processes in the aquifers of Kentucky: (1) mixing of freshwater and saline water in an interface zone; (2) dedolomitization of the Devonian and Silurian and Lower Mississippian carbonate rocks; (3) sodium for calcium exchange in the freshwater sections of many of the sandstone-shale aquifers. A number of errors and deficiencies were found in the data base. The principal deficiencies were: (1) very few complete analyses which included important field measurements; (2) inadequate definition of the chemistry of the freshwater-saline water interface zone throughout much of the State; (3) no analyses of stable isotopes and dissolved gases; (4) fewer than 10 analyses of most trace metals, radionuclides, and man-made organic chemicals; and (5) no data on bacteria in ground water from any aquifer in the State. (USGS)

Effects of bedrock geology on source and flowpath of runoff water in steep unchanneled hollows

NASA Astrophysics Data System (ADS)

Uchida, T.; Asano, Y.; Kosugi, K.; Ohte, N.; Mizuyama, T.

2001-05-01

Simultaneous measurements of runoff, soil pore water pressure and soil temperature were taken to evaluate the spatial and temporal nature of flowpaths and flow sources in steep unchanneled hollows in central Japan. Two small hollows were monitored; one is underlain by granite and one is underlain by Paleozoic shale. In both catchments, tensiometers showed that a saturated area formed in the areas near a spring. The soil temperature suggests that in the small perennially saturated area near the spring, water percolating through the vadose zone mixed with water emerging from the bedrock. During rainstorms, the streamflow varied with the soil pore water pressure on the upper slope; the soil pore water pressure in the area near the spring remained nearly constant._@ Moreover, the spring water temperature was almost the same as the transient groundwater temperature on the upper slope. This indicates that the transient groundwater in the upper slope flowed to the spring via lateral preferential paths in both catchments. During summer rainstorms, the soil-bedrock interface temperature increased as the ground became saturated in the granite hollow, suggesting that both rainwater and shallow soil water had important effects on the formation of transient saturated groundwater on the upper slope. That is, it can be concluded that the contribution of the bedrock groundwater to the streamflow was relatively small in the granite hollow during storm runoff. The area where the bedrock groundwater seeped into the soil mantle did not grow in size as the contributing area for the streamflow extended to the upper hollow in the granite catchment. In contrast, the soil temperature indicated that after heavy rainfall (77.5 mm), bedrock groundwater played an important role in the formation of the transient groundwater in the Paleozoic shale hollow. Consequently, the contribution of the bedrock groundwater to the streamflow was relatively large in the shale hollow after heavy rainfall.

Hydrogeology, chemical quality, and availability of ground water in the Upper Floridan aquifer, Albany area, Georgia

USGS Publications Warehouse

Hicks, D.W.; Gill, H.E.; Longsworth, S.A.

1987-01-01

Large withdrawals of groundwater in the 1500 sq mi Albany area of southwestern Georgia have lowered water levels in deep aquifers as much as 140 ft. This study was conducted to evaluate the development potential of the shallow Upper Floridan aquifer as an alternate source of groundwater, especially for public supply. The Upper Floridan stores and transmits large quantities of water, mainly in a zone of high permeability in the lower part of the aquifer. The transmissivity of the aquifer ranges from < 10,000 sq ft/day northwest of Albany, to as much as 150 ,000 sq ft/day south and southeast of Albany. Twenty-eight years of agricultural and industrial pumping has not produced a long-term decline of the water level in the Upper Floridan; the aquifer system remains at equilibrium. The Upper Floridan yields hard, calcium bicarbonate-type water but concentrations do not exceed State drinking water standards. In most of the study area , contaminants applied to or spilled on the land surface eventually can be expected to percolate through the overburden and reach the aquifer. Thus, it is important that wells be sited away from areas that have been used for the storage and disposal of potential contaminants and, probably to a lesser extent, the application of agricultural chemicals. In the area of greatest development potential east of the Flint River, wells may penetrate major groundwater conduits. By limiting drawdown during well development and during production, the likelihood of causing sinkholes to form can be minimized. Closed depressions, or sinks, throughout the Dougherty Plain probably are unsuitable as well sites, because (1) they are subject to flooding, (2) they collect water from upgradient areas and could concentrate potential contaminants, (3) water probably percolates through their bottoms and could transport contaminants into the aquifer, and (4) the depressions may overlie limestone cavities filled with sand or clay that could interfere with well yield, development, and production. (Author 's abstract)

Assessing the Merit of Soil Moisture as both a Metric and Predictor of Drought for Colorado and the Upper Colorado River Basin Using Land Data Assimilation Models.

NASA Astrophysics Data System (ADS)

Goble, P.; Schumacher, R. S.; Doesken, N.

2015-12-01

Root zone soil moisture (RZSM) is the water in the soil that is within the reach of surface vegetation. When RZSM becomes sufficiently low plants are no longer able to overcome the suction force holding water in the soil. This skews the partitioning of latent and sensible heating in favor of sensible heating, thus warming the surface, and potentially invoking a positive feedback. Findings from Koster et al published in 2004 indicate that not only is there potential for the improvement of seasonal forecasts through tracking RZSM, but also that RZSM feedbacks are strongest in what can be thought of as wet-dry transitional zones. These are zones where surface evaporation rates average high enough to be expected to have an important influence on precipitation, and where available soil moisture is still an important constraint on how much surface evaporation takes place. In the Upper Colorado River Basin and eastern Colorado climate varies rapidly with space due to differences in elevation, and these transitional zones do exist within the domain. This paper focuses on how NASA Land Data Assimilation Modeled RZSM is used to help track drought in the Upper Colorado River Basin and eastern Colorado, and addresses the additive predictive skill RZSM may have on multi-weekly and seasonal timescales across the Upper Colorado River Basin and eastern Colorado during the growing season. Daily modeled soil moisture from three land data assimilation models was correlated with North American Regional Reanalysis temperature data, and precipitation data from rain gauges interpolated using PRISM climatology in order to help answer important questions about the predictive skill of soil moisture, and its value in the drought early warning process. Questions addressed here will be as follows: In what climate regimes within the domain does RZSM have the most predictive power over temperature and precipitation? Do certain predominant soil and vegetation types preferentially strengthen RZSM-atmosphere interaction? How does the behavior of RZSM during the onset of severe droughts within the domain over the last 20 years compare to normal behavior? How much do these answers vary between land surface models given the same forcing inputs?

Convectively driven PCR thermal-cycling

DOEpatents

Benett, William J.; Richards, James B.; Milanovich, Fred P.

2003-07-01

A polymerase chain reaction system provides an upper temperature zone and a lower temperature zone in a fluid sample. Channels set up convection cells in the fluid sample and move the fluid sample repeatedly through the upper and lower temperature zone creating thermal cycling.

Excavation of red squirrel middens by grizzly bears in the whitebark pine zone

USGS Publications Warehouse

Mattson, D.J.; Reinhart, Daniel P.

1997-01-01

Whitebark pine seeds Pinus albicaulis are an important food of grizzly Ursus arctos horribilis bears wherever whitebark pine is abundant in the contiguous United States of America; availability of seeds affects the distribution of bears, and the level of conflict between bears and humans. Almost all of the seeds consumed by bears are excavated from middens where red squirrels Tamiasciurus hudsonicus have cached whitebark pine cones.Relationships among the occupancy of middens by squirrels, the excavation of middens by bears, and site features were investigated in this study. Data were collected from radio-marked bears and from middens located from line transects on two study sites in the Yellowstone ecosystem.Densities of active middens were positively related to lodgepole pine Pinus contorta basal area and negatively related to steepness of slope.The probability that a midden was occupied by a squirrel (i.e. active) was positively related to lodgepole pine basal area in the surrounding stand, size of the midden and size of the whitebark pine cone crop, and negatively related to elevation and to bear excavation during the previous 2-12 months.The probability that a midden had been excavated by a bear during the previous 12 months was positively related to size of the midden, and to whitebark pine basal area and cone crop, and negatively related to nearness of roads and town sites.The influence of midden size on bear use was attributable to a positive relationship with the number of excavated cones. The positive association between bear excavations and whitebark pine basal area or cone crops was attributable to availability of pine seeds.Grizzly bears would benefit from the minimization of roads and other human facilities in the whitebark pine zone and from increases in the availability of whitebark pine seeds, potentially achieved by increasing the numbers of cone-producing whitebark pine trees, especially in lower elevations of the whitebark pine zone where red squirrels are more abundant.

Impact-Facilitated Hydrothermal Alteration in the Rim of Endeavour Crater, Mars

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Schroeder, C.; Farrand, W. H.; Crumpler, L. S.; Yen, A. S.

2017-01-01

Endeavour crater, a Noachian-aged, 22 km diameter impact structure on Meridiani Planum, Mars, has been investigated by the Mars Exploration Rover Opportunuity for over 2000 sols (Mars days). The rocks of the western rim region (oldest to youngest) are: (i) the pre-impact Matijevic fm.; (ii) rim-forming Shoemaker fm. polymict impact breccias; (iii) Grasberg fm., fine-grained sediments draping the lower slopes; and (iv) Burns fm., sulfate-rich sandstones that onlap the Grasberg fm. The rim is segmented and transected by radial fracture zones. Evidence for fluid-mediated alteration includes m-scale detections of phyllosilicates from orbit, and cm-scale variations in rock/soil composition/mineralogy documented by the Opportunity instrument suite. The m-scale phyllosilicate detections include Fe(3+)-Mg and aluminous smectites that occur in patches in the Matijevic and Shoemaker fms. Rock compositions do not reveal substantial differences for smectite-bearing compared to smectite-free rocks. Interpretation: large-scale hydrothermal alteration powered by impact-deposited heat acting on limited water supplies engendered mineralogic transfomations under low water/rock, near-isochemical conditions. The cm-scale alterations, localized in fracture zones, occurred at higher water/rock as evidenced by enhanced Si and Al contents through leaching of more soluble elements, and deposition of Mg, Ni and Mn sulphates and halogen salts in soils. Visible/near infrared reflectance of narrow curvilinear red zones indicate higher nanophase ferric oxide contents and possibly hydration compared to surrounding outcrops. Broad fracture zones on the rim have reflectance features consistent with development of ferric oxide minerals. Interpretation: water fluxing through the fractures in a hydrothermal system resulting from the impact engendered alteration and leaching under high water/rock conditions. Late, localized alteration is documented by Ca-sulfate-rich veins that are not confined to fracture zones; some cross-cut the Grasberg fm. Interpretation: late fluid mobilization of soluble elements, likely in a later alteration event.

Groundwater vulnerability mapping in Guadalajara aquifers system (Western Mexico)

NASA Astrophysics Data System (ADS)

Rizo-Decelis, L. David; Marín, Ana I.; Andreo, Bartolomé

2016-04-01

Groundwater vulnerability mapping is a practical tool to implement strategies for land-use planning and sustainable socioeconomic development coherent with groundwater protection. The objective of vulnerability mapping is to identify the most vulnerable zones of catchment areas and to provide criteria for protecting the groundwater used for drinking water supply. The delineation of protection zones in fractured aquifers is a challenging task due to the heterogeneity and anisotropy of hydraulic conductivities, which makes difficult prediction of groundwater flow organization and flow velocities. Different methods of intrinsic groundwater vulnerability mapping were applied in the Atemajac-Toluquilla groundwater body, an aquifers system that covers around 1300 km2. The aquifer supplies the 30% of urban water resources of the metropolitan area of Guadalajara (Mexico), where over 4.6 million people reside. Study area is located in a complex neotectonic active volcanic region in the Santiago River Basin (Western Mexico), which influences the aquifer system underneath the city. Previous works have defined the flow dynamics and identified the origin of recharge. In addition, the mixture of fresh groundwater with hydrothermal and polluted waters have been estimated. Two main aquifers compose the multilayer system. The upper aquifer is unconfined and consists of sediments and pyroclastic materials. Recharge of this aquifer comes from rainwater and ascending vertical fluids from the lower aquifer. The lower aquifer consists of fractured basalts of Pliocene age. Formerly, the main water source has been the upper unit, which is a porous and unconsolidated unit, which acts as a semi-isotropic aquifer. Intense groundwater usage has resulted in lowering the water table in the upper aquifer. Therefore, the current groundwater extraction is carried out from the deeper aquifer and underlying bedrock units, where fracture flow predominates. Pollution indicators have been reported in some monitoring wells, which have been related to anthropogenic activity. Vulnerability maps were produced using different parametric methods (e.g.: DRASTIC, GOD, DISCO, AVI), then the results are compared and assessed. Since each one of these methods use different number of parameters and weights, relatively different results were obtained, although the results have been evaluated with common cartographic inputs. The comparison between selected methods shows that the GOD method results are more correlated with the other methods and produces vulnerability maps comparable with them. Even though groundwater vulnerability is a critical issue around the world, no protection zones have been delineated in Guadalajara city, one of the biggest in Latin America. The groundwater contamination in the study area poses a serious risk for a large population and the environment. This work aims to propose an approach for groundwater protection cartography, based on the application and the comparison of results from different contamination vulnerability methods. These outcomes may assist water authorities to identify the higher vulnerable zones of the aquifers, in order to improving and adapting the land planning and management according to the protection of the own water resources.

P-wave Velocity Structure Across the Mariana Trench and Implications for Hydration

NASA Astrophysics Data System (ADS)

Eimer, M. O.; Wiens, D.; Lizarralde, D.; Cai, C.

2017-12-01

Estimates of the water flux at subduction zones remain uncertain, particularly the amount of water brought into the trench by the subducting plate. Normal faulting related to the bending of the incoming plate has been proposed to provide pathways for water to hydrate the crust and upper mantle. A passive and active source seismic experiment spanning both the incoming plate and forearc was conducted in 2012 in central Mariana to examine the role of hydration at subduction zones. The active-source component of the survey used the R/V M.G. Langsethairgun array and 68 short period sensors, including suspended hydrophones, deployed on 4 transects. This study at the Mariana trench offers a comparison to related studies of incoming plate hydration in Middle America, where differing thermal structures related to plate age predict different stability fields for hydrous minerals. The forearc structure is also of interest, since Mariana is characterized by large serpentine seamounts and may have a serpentinized mantle wedge. The velocity structure will also be important for the relocation of earthquakes in the incoming plate, since the seismicity can offer a constraint for the depth extent of these bending faults. We examine the P-wave velocity structure along a 400-km long wide-angle refraction transect perpendicular to the trench and spanning both the forearc and incoming plate. Preliminary results indicate a velocity reduction in the crust and uppermost mantle at the bending region of the incoming plate, relative to the plate's structure away from the trench. This reduction suggests that outer-rise faults extend into the upper mantle and may have promoted serpentinization of that material. Mantle Pn refraction phases are not observed in the forearc, consistent with the ambient noise tomography results that show upper-mantle velocities similar to that of the lower crust. The lack of contrast between the upper mantle and crustal velocities from the ambient noise has been interpreted to indicate extensive serpentinization of the shallow mantle wedge.

Chemical, isotopic, and microbiological evidence for denitrification during transport of domestic wastewater through a thick unsaturated zone in the Mojave Desert, San Bernardino County, California

USGS Publications Warehouse

Schroeder, R.A.; Martin, P.M.; Böhlke, J.K.

1993-01-01

Nitrogen in downward-infiltrating wastewater discharged from seepage pits (dry wells) at residences in the upper Mojave River Basin, California represents a significant potential source of nitrate contamination to the underlying ground water. However, increases in nitrate concentration in the ground water have not yet been observed. The low nitrate concentration in the ground water may be the result of lateral dispersion in the unsaturated zone, dilution below the water table, or denitrification of wastewater nitrate in the unsaturated zone. Measured vertical rates indicate that some wastewater has reached the water table beneath communities that are older than 5 to 10 years. As wastewater percolates from seepage pits into the unsaturated zone, reduced nitrogen is converted rapidly to nitrate at shallow depths and the nitrate concentrations commonly decrease with depth. The largest nitrate decreases seem to coincide with increased content of fine-grained sediments or with proximity to the water table. Between lysimeters at 160 and 199 feet at one residence, the decrease in nitrate concentration coincided with a large increase in sulfate, decrease in alkalinity, and increase in 815N in nitrate. Those data are consistent with denitrification by oxidation of iron sulfide to produce ferric oxides; but if such a reaction occurs, it must be in domains that are small in comparison with the sampled volumes because the waters also contain substantial quantities of dissolved oxygen. The predominantly low nitrate concentrations in the area's ground water are consistent with the operation of a nitrogen-removal mechanism, possibly denitrification; however, the reducing capacity of the sediments to maintain denitrification is not known.

Microbial eukaryote diversity in the marine oxygen minimum zone off northern Chile.

PubMed

Parris, Darren J; Ganesh, Sangita; Edgcomb, Virginia P; DeLong, Edward F; Stewart, Frank J

2014-01-01

Molecular surveys are revealing diverse eukaryotic assemblages in oxygen-limited ocean waters. These communities may play pivotal ecological roles through autotrophy, feeding, and a wide range of symbiotic associations with prokaryotes. We used 18S rRNA gene sequencing to provide the first snapshot of pelagic microeukaryotic community structure in two cellular size fractions (0.2-1.6 μm, >1.6 μm) from seven depths through the anoxic oxygen minimum zone (OMZ) off northern Chile. Sequencing of >154,000 amplicons revealed contrasting patterns of phylogenetic diversity across size fractions and depths. Protist and total eukaryote diversity in the >1.6 μm fraction peaked at the chlorophyll maximum in the upper photic zone before declining by ~50% in the OMZ. In contrast, diversity in the 0.2-1.6 μm fraction, though also elevated in the upper photic zone, increased four-fold from the lower oxycline to a maximum at the anoxic OMZ core. Dinoflagellates of the Dinophyceae and endosymbiotic Syndiniales clades dominated the protist assemblage at all depths (~40-70% of sequences). Other protist groups varied with depth, with the anoxic zone community of the larger size fraction enriched in euglenozoan flagellates and acantharean radiolarians (up to 18 and 40% of all sequences, respectively). The OMZ 0.2-1.6 μm fraction was dominated (11-99%) by Syndiniales, which exhibited depth-specific variation in composition and total richness despite uniform oxygen conditions. Metazoan sequences, though confined primarily to the 1.6 μm fraction above the OMZ, were also detected within the anoxic zone where groups such as copepods increased in abundance relative to the oxycline and upper OMZ. These data, compared to those from other low-oxygen sites, reveal variation in OMZ microeukaryote composition, helping to identify clades with potential adaptations to oxygen-depletion.

Microbial eukaryote diversity in the marine oxygen minimum zone off northern Chile

PubMed Central

Parris, Darren J.; Ganesh, Sangita; Edgcomb, Virginia P.; DeLong, Edward F.; Stewart, Frank J.

2014-01-01

Molecular surveys are revealing diverse eukaryotic assemblages in oxygen-limited ocean waters. These communities may play pivotal ecological roles through autotrophy, feeding, and a wide range of symbiotic associations with prokaryotes. We used 18S rRNA gene sequencing to provide the first snapshot of pelagic microeukaryotic community structure in two cellular size fractions (0.2–1.6 μm, >1.6 μm) from seven depths through the anoxic oxygen minimum zone (OMZ) off northern Chile. Sequencing of >154,000 amplicons revealed contrasting patterns of phylogenetic diversity across size fractions and depths. Protist and total eukaryote diversity in the >1.6 μm fraction peaked at the chlorophyll maximum in the upper photic zone before declining by ~50% in the OMZ. In contrast, diversity in the 0.2–1.6 μm fraction, though also elevated in the upper photic zone, increased four-fold from the lower oxycline to a maximum at the anoxic OMZ core. Dinoflagellates of the Dinophyceae and endosymbiotic Syndiniales clades dominated the protist assemblage at all depths (~40–70% of sequences). Other protist groups varied with depth, with the anoxic zone community of the larger size fraction enriched in euglenozoan flagellates and acantharean radiolarians (up to 18 and 40% of all sequences, respectively). The OMZ 0.2–1.6 μm fraction was dominated (11–99%) by Syndiniales, which exhibited depth-specific variation in composition and total richness despite uniform oxygen conditions. Metazoan sequences, though confined primarily to the 1.6 μm fraction above the OMZ, were also detected within the anoxic zone where groups such as copepods increased in abundance relative to the oxycline and upper OMZ. These data, compared to those from other low-oxygen sites, reveal variation in OMZ microeukaryote composition, helping to identify clades with potential adaptations to oxygen-depletion. PMID:25389417

Subduction of hydrated basalt of the oceanic crust: Implications for recycling of water into the upper mantle and continental growth

NASA Technical Reports Server (NTRS)

Rapp, R. P.

1994-01-01

Subduction zones are presently the dominant sites on Earth for recycling and mass transfer between the crust and mantle; they feed hydrated basaltic oceanic crust into the upper mantle, where dehydration reactions release aqueous fluids and/or hydrous melts. The loci for fluid and/or melt generation will be determined by the intersection of dehydration reaction boundaries of primary hydrous minerals within the subducted lithosphere with slab geotherms. For metabasalt of the oceanic crust, amphibole is the dominant hydrous mineral. The dehydration melting solidus, vapor-absent melting phase relationships; and amphibole-out phase boundary for a number of natural metabasalts have been determined experimentally, and the pressure-temperature conditions of each of these appear to be dependent on bulk composition. Whether or not the dehydration of amphibole is a fluid-generating or partial melting reaction depends on a number of factors specific to a given subduction zone, such as age and thickness of the subducting oceanic lithosphere, the rate of convergence, and the maturity of the subduction zone. In general, subduction of young, hot oceanic lithosphere will result in partial melting of metabasalt of the oceanic crust within the garnet stability field; these melts are characteristically high-Al2O3 trondhjemites, tonalites and dacites. The presence of residual garnet during partial melting imparts a distinctive trace element signature (e.g., high La/Yb, high Sr/Y and Cr/Y combined with low Cr and Y contents relative to demonstrably mantle-derived arc magmas). Water in eclogitized, subducted basalt of the oceanic crust is therefore strongly partitioned into melts generated below about 3.5 GPa in 'hot' subduction zones. Although phase equilibria experiments relevant to 'cold' subduction of hydrated natural basalts are underway in a number of high-pressure laboratories, little is known with respect to the stability of more exotic hydrous minerals (e.g., ellenbergite) and the potential for oceanic crust (including metasediments) to transport water deeper into the mantle.

Nutrient transport and transformation beneath an infiltration basin

USGS Publications Warehouse

Sumner, D.M.; Rolston, D.E.; Bradner, L.A.

1998-01-01

Field experiments were conducted to examine nutrient transport and transformation beneath an infiltration basin used for the disposal of treated wastewater. Removal of nitrogen from infiltrating water by denitrification was negligible beneath the basin, probably because of subsurface aeration as a result of daily interruptions in basin loading. Retention of organic nitrogen in the upper 4.6 m of the unsaturated zone (water table depth of approximately 11 m) during basin loading resulted in concentrations of nitrate as much as 10 times that of the applied treated wastewater, following basin 'rest' periods of several weeks, which allowed time for mineralization and nitrification. Approximately 90% of the phosphorus in treated wastewater was removed within the upper 4.6 m of the subsurface, primarily by adsorption reactions, with abundant iron and aluminum oxyhydroxides occurring as soil coatings. A reduction in the flow rate of infiltrating water arriving at the water table may explain the accumulation of relatively coarse (>0.45 ??m), organic forms of nitrogen and phosphorus slightly below the water table. Mineralization and nitrification reactions at this second location of organic nitrogen accumulation contributed to concentrations of nitrate as much as three times that of the applied treated wastewater. Phosphorus, which accumulated below the water table, was immobilized by adsorption or precipitation reactions during basin rest periods.Field experiments were conducted to examine nutrient transport and transformation beneath an infiltration basin used for the disposal of treated wastewater. Removal of nitrogen from infiltrating water by denitrification was negligible beneath the basin, probably because of subsurface aeration as a result of daily interruptions in basin loading. Retention of organic nitrogen in the upper 4.6 m of the unsaturated zone (water table depth of approximately 11 m) during basin loading resulted in concentrations of nitrate as much as 10 times that of the applied treated wastewater, following basin 'rest' periods of several weeks, which allowed time for mineralization and nitrification. Approximately 90% of the phosphorus in treated wastewater was removed within the upper 4.6 m of the subsurface, primarily by adsorption reactions, with abundant iron and aluminum oxyhydroxides occurring as soil coatings. A reduction in the flow rate of infiltrating water arriving at the water table may explain the accumulation of relatively coarse (>0.45 ??m), organic forms of nitrogen and phosphorus slightly below the water table. Mineralization and nitrification reactions at this second location of organic nitrogen accumulation contributed to concentrations of nitrate as much as three times that of the applied treated wastewater. Phosphorus, which accumulated below the water table, was immobilized by adsorption or precipitation reactions during basin rest periods.

Devonian Terrestrial Revolution: the palaeoenvironment of the oldest known tetrapod tracks, Zachełmie Quarry, Poland

NASA Astrophysics Data System (ADS)

Niedźwiedzki, G.

2012-04-01

Numerous trackways and isolated prints with digit impressions, which are similar to the foot anatomy of early tetrapods such as Ichthyostega, were found on the three dolomite bed-surfaces in the lower part of the Wojciechowice Formation exposed in the Zachełmie Quarry in the Holy Cross Mountains (south-central Poland), (Niedźwiedzki et al., 2010). The age of the tetrapod track-bearing strata is well-constrained, but the detailed sedimentology of the lower section with tetrapod ichnites is still under study. The Wojciechowice Formation represent one of the first carbonate stages of a transgressive succession that begins with Early Devonian continental to marginal marine clastics and culminates in the development of a Givetian coral-stromatoporoid carbonate platform. The tetrapod track-bearing complex is composed of grey to reddish, thin- to medium-bedded dolomitic shales and marly dolomite mudstones. These deposits from the tetrapod track-bearing horizon lack definitive marine body fossils, and may have formed in a marginal marine environment, e.g. around a coastal lagoon. Mudcracks, columnar peds, root traces, and microbially induced sedimentary structures were found in three distinct pedotypes of very weakly to weakly developed paleosols (Retallack, 2011). Conodonts of the costatus zone (mid-Eifelian) were found 20 m above the uppermost surface with tetrapod tracks in limestones of the upper Wojciechowice Formation, which contain also brachiopod and crinoidal debris. The overlying Kowala Formation is a marine coral limestone and dolostone. The parts of profile with tetrapod ichnites and invertebrate and conodont fossils contain also records of invertebrate traces. Seven ichnotaxa are distributed among four recognized ichnoassemblages. The recognized ichnocoenoses are typical for the shallow-marine (Cruziana ichnofacies) and land-water transitional (Skolithos/Psilonichnus ichnofacies) carbonate depositional environments. The ichnocoenoses are dominated by trace fossils produced by arthropods (probably crustaceans), a group that can create large and distinctive burrows. The palaeoecological information from the Zachełmie section has direct bearing on the interpretation of environmental aspects of tetrapod emergence and terrestrialization. It should be fully integrated with data from other Devonian tetrapod tracksites. Niedźwiedzki, G., Szrek P., Narkiewicz K., Narkiewicz M. and Ahlberg P.E. 2010. Tetrapod trackways from the early Middle Devonian period of Poland. Nature, 463: 43-48. Retallack, G.J. 2011. Woodland Hypothesis for Devonian Tetrapod Evolution. The Journal of Geology, 119, 3: 235-258

Geological process of the slow earthquakes -A hypothesis from an ancient plate boundary fault rock

NASA Astrophysics Data System (ADS)

Kitamura, Y.; Kimura, G.; Kawabata, K.

2012-12-01

We present an integrated model of the deformation along the subduction plate boundary from the trench to the seismogenic zone. Over years of field based research in the Shimanto Belt accretionary complex, southwest Japan, yielded breaking-through discoveries on plate boundary processes, for example, the first finding of pseudotachylyte in the accretionary prism (Ikesawa et al., 2003). Our aim here is to unveil the geological aspects of slow earthquakes and the related plate boundary processes. Studied tectonic mélanges in the Shimanto Belt are regarded as fossils of plate boundary fault zone in subduction zone. We traced material from different depths along subduction channel using samples from on-land outcrops and ocean drilling cores. As a result, a series of progressive deformation down to the down-dip limit of the seismogenic zone was revealed. Detailed geological survey and structural analyses enabled us to separate superimposed deformation events during subduction. Material involved in the plate boundary deformation is mainly an alternation of sand and mud. As they have different competency and are suffered by simple shear stress field, sandstones break apart in flowing mudstones. We distinguished several stages of these deformations in sandstones and recognized progress in the intensity of deformation with increment of underthrusting. It is also known that the studied Mugi mélange bears pseudotachylyte in its upper bounding fault. Our conclusion illustrates that the subduction channel around the depth of the seismogenic zone forms a thick plate boundary fault zone, where there is a clear segregation in deformation style: a fast and episodic slip at the upper boundary fault and a slow and continuous deformation within the zone. The former fast deformation corresponds to the plate boundary earthquakes and the latter to the slow earthquakes. We further examined numerically whether this plate boundary fault rock is capable of releasing seismic moment enough to fit the observed slow earthquakes. The shallow very low frequent earthquakes (VLFs) are chosen to be modeled and our estimation satisfies the natural data. We emphasize that the plate boundary is not a plane but a zone. Geological setting is a clue for differentiating slow and normal earthquakes. We propose to focus on the three-dimensional fault zone comprising numbers of microfaults as the source of slow earthquakes instead of planar plate boundary. Our results also make an impact on the study of seismic energy balance because we show a possibility to give an absolute value of them from geological approach, which could not have been achieved with seismology.

Ground-water resources and potential hydrologic effects of surface coal mining in the northern Powder River basin, southeastern Montana

USGS Publications Warehouse

Slagle, Steven E.; Lewis, Barney D.; Lee, Roger W.

1985-01-01

The shallow ground-water system in the northern Powder River Basin consists of Upper Cretaceous to Holocene aquifers overlying the Bearpaw Shale--namely, the Fox Hills Sandstone; Hell Creek, Fort Union, and Wasatch Formations; terrace deposits; and alluvium. Ground-water flow above the Bearpaw Shale can be divided into two general flow patterns. An upper flow pattern occurs in aquifers at depths of less than about 200 feet and occurs primarily as localized flow controlled by the surface topography. A lower flow pattern occurs in aquifers at depths from about 200 to 1,200 feet and exhibits a more regional flow, which is generally northward toward the Yellowstone River with significant flow toward the Powder and Tongue Rivers. The chemical quality of water in the shallow ground-water system in the study area varies widely, and most of the ground water does not meet standards for dissolved constituents in public drinking water established by the U.S. Environmental Protection Agency. Water from depths less than 200 feet generally is a sodium sulfate type having an average dissolved-solids concentration of 2,100 milligrams per liter. Sodium bicarbonate water having an average dissolved-solids concentration of 1,400 milligrams per liter is typical from aquifers in the shallow ground-water system at depths between 200 and 1,200 feet. Effects of surface coal mining on the water resources in the northern Powder River Basin are dependent on the stratigraphic location of the mine cut. Where the cut lies above the water-yielding zone, the effects will be minimal. Where the mine cut intersects a water-ielding zone, effects on water levels and flow patterns can be significant locally, but water levels and flow patterns will return to approximate premining conditions after mining ceases. Ground water in and near active and former mines may become more mineralized, owing to the placement of spoil material from the reducing zone in the unsaturated zone where the minerals are subject to oxidation. Regional effects probably will be small because of the limited areal extent of ground-water flow systems where mining is feasible. Results of digital models are presented to illustrate the effects of varying hydraulic properties on water-level changes resulting from mine dewatering. The model simulations were designed to depict maximum-drawdown situations. One simulation indicates that after 20 years of continuous dewatering of an infinite, homogeneous, isotropic aquifer that is 10 feet thick and has an initial potentiometric surface 10 feet above the top of the aquifer, water-level declines greater than 1 foot would generally be limited to within 7.5 miles of the center of the mine excavation; declines greater than 2 feet to within about 6 miles; declines greater than 5 feet to within about 3.7 miles; declines greater than 10 feet to within about 1.7 miles; and declines greater than 15 feet to within 1.2 miles.

The role of recharge zones, discharge zones, springs and tile drainage systems in peneplains of Central European highlands with regard to water quality generation processes

NASA Astrophysics Data System (ADS)

Doležal, František; Kvítek, Tomáš

The hydrogeology, runoff generation and water quality generation in old peneplains of Central Europe built by acid crystalline rocks (such as the Bohemo-Moravian Highland) are described and interpreted in terms of a three-zone concept. The recharge zones are located on flat tops of hills and their soils are mostly permeable. It is mainly through them that the shallow groundwater-bearing formations are loaded with nitrate. The groundwater exfiltrates on the lower parts of slopes (in the so-called transient zone) and in narrow valleys (in the discharge zone), creating dispersed springs and waterlogged areas. In addition, the rapid and shallow flow of perched groundwater down the slope, which takes place during wet periods in the recharge zone and, mainly, in the transient zone, leaches the nitrate from the soil directly to the stream, without necessarily being in contact with the permanent groundwater table of the recharge and the transient zones. Discharge and water quality measurements in the Kopaninský tok experimental catchment (6.7 km 2) were analysed, using a combination of two runoff separation techniques (a digital filter and a simple conceptual model GROUND). Three runoff components were distinguished (direct runoff, interflow and baseflow). There is a weak but significant positive correlation between the stream nitrate concentration on the one hand and either the interflow or the baseflow on the other hand. There is also a weak but significant negative correlation between the stream nitrate concentration on the one hand and either the ratio of direct runoff to total stream flow or the logarithm of this ratio on the other hand, provided that the cases of zero direct runoff are disregarded. A simple mixing model was used to estimate the characteristic nitrate concentrations of individual runoff components. The interflow has the highest characteristic nitrate concentration and is probably the main stream water polluter with nitrate. The baseflow is identified as the likely second main polluter. The differences in water quality between a drainage outlet and a forest spring indicate the importance of a proper nitrogen management in the recharge zones. It is also concluded that the tile drainage and tillage of formerly waterlogged sites, mainly located in transient zones, reduce the opportunity for denitrification of both baseflow and interflow. The ploughed lands in the recharge zones represent an established basis for local agriculture and cannot be easily set aside. Many such lands have been declared as vulnerable to nitrate pollution in order to protect waters against impacts of risky agricultural practices. It is proposed that some waterlogged and drained sites in the transient and discharge zones are set aside rather than the flat ploughed lands on the hill tops. To increase the denitrification, tile drainage runoff from the transient and the discharge zones should be retarded.

Ground-water hydrology of the Willamette basin, Oregon

USGS Publications Warehouse

Conlon, Terrence D.; Wozniak, Karl C.; Woodcock, Douglas; Herrera, Nora B.; Fisher, Bruce J.; Morgan, David S.; Lee, Karl K.; Hinkle, Stephen R.

2005-01-01

The Willamette Basin encompasses a drainage of 12,000 square miles and is home to approximately 70 percent of Oregon's population. Agriculture and population are concentrated in the lowland, a broad, relatively flat area between the Coast and Cascade Ranges. Annual rainfall is high, with about 80 percent of precipitation falling from October through March and less than 5 percent falling in July and August, the peak growing season. Population growth and an increase in cultivation of crops needing irrigation have produced a growing seasonal demand for water. Because many streams are administratively closed to new appropriations in summer, ground water is the most likely source for meeting future water demand. This report describes the current understanding of the regional ground-water flow system, and addresses the effects of ground-water development. This study defines seven regional hydrogeologic units in the Willamette Basin. The highly permeable High Cascade unit consists of young volcanic material found at the surface along the crest of the Cascade Range. Four sedimentary hydrogeologic units fill the lowland between the Cascade and Coast Ranges. Young, highly permeable coarse-grained sediments of the upper sedimentary unit have a limited extent in the floodplains of the major streams and in part of the Portland Basin. Extending over much of the lowland where the upper sedimentary unit does not occur, silts and clays of the Willamette silt unit act as a confining unit. The middle sedimentary unit, consisting of permeable coarse-grained material, occurs beneath the Willamette silt and upper sedimentary units and at the surface as terraces in the lowland. Beneath these units is the lower sedimentary unit, which consists of predominantly fine-grained sediments. In the northern part of the basin, lavas of the Columbia River basalt unit occur at the surface in uplands and beneath the basin-fill sedimentary units. The Columbia River basalt unit contains multiple productive water-bearing zones. A basement confining unit of older marine and volcanic rocks of low permeability underlies the basin and occurs at land surface in the Coast Range and western part of the Cascade Range. Most recharge in the basin is from infiltration of precipitation, and the spatial distribution of recharge mimics the distribution of precipitation, which increases with elevation. Basinwide annual mean recharge is estimated to be 22 inches. Rain and snowmelt easily recharge into the permeable High Cascade unit and discharge within the High Cascade area. Most recharge in the Coast Range and western part of the Cascade Range follows short flowpaths through the upper part of the low permeability material and discharges to streams within the mountains. Consequently, recharge in the Coast and Ranges is not available as lateral ground-water flow into the lowland, where most ground-water use occurs. Within the lowland, annual mean recharge is 16 inches and most recharge occurs from November to April, when rainfall is large and evapotranspiration is small. From May to October recharge is negligible because precipitation is small and evapotranspiration is large. Discharge of ground water is mainly to streams. Ground-water discharge is a relatively large component of flow in streams that drain the High Cascade unit and parts of the Portland Basin where permeable units are at the surface. In streams that do not head in the High Cascade area, streamflow is generally dominated by runoff of precipitation. Ground-water in the permeable units in the lowland discharges to the major streams where there is a good hydraulic connection between aquifers and streams. Ground-water discharge to smaller streams, which flow on the less permeable Willamette silt unit, is small and mostly from the Willamette silt unit. Most ground-water withdrawals occur within the lowland. Irrigation is the largest use of ground water, accounting for 240,000 acre feet of withdrawals, or 81 p

Rapid Dissolution of Soluble Uranyl Phases in Arid, Mine-Impacted Catchments Near Church Rock, NM

DOE Office of Scientific and Technical Information (OSTI.GOV)

deLemos, J.L.; Bostick, B.C.; Quicksall, A.N.

2009-05-14

We tested the hypothesis that runoff of uranium-bearing particles from mining waste disposal areas was a significant mechanism for redistribution of uranium in the northeastern part of the Upper Puerco River watershed (New Mexico). However, our results were not consistent with this hypothesis. Analysis of >100 sediment and suspended sediment samples collected adjacent to and downstream from uranium source areas indicated that uranium levels in the majority of the samples were not elevated above background. Samples collected within 50 m of a known waste disposal site were subjected to detailed geochemical characterization. Uranium in these samples was found to bemore » highly soluble; treatment with synthetic pore water for 24 h caused dissolution of 10-50% of total uranium in the samples. Equilibrium uranium concentrations in pore water were >4.0 mg/L and were sustained in repeated wetting events, effectively depleting soluble uranium from the solid phase. The dissolution rate of uranium appeared to be controlled by solid-phase diffusion of uranium from within uranium-bearing mineral particles. X-ray adsorption spectroscopy indicated the presence of a soluble uranyl silicate, and possibly a uranyl phosphate. These phases were exhausted in transported sediment suggesting that uranium was readily mobilized from sediments in the Upper Puerco watershed and transported in the dissolved load. These results could have significance for uranium risk assessment as well as mining waste management and cleanup efforts.« less

Rapid Dissolution of Soluble Uranyl Phases in Arid, Mine-Impacted Catchments near Church Rock, NM

PubMed Central

DELEMOS, JAMIE L.; BOSTICK, BENJAMIN C.; QUICKSALL, ANDREW N.; LANDIS, JOSHUA D.; GEORGE, CHRISTINE C.; SLAGOWSKI, NAOMI L.; ROCK, TOMMY; BRUGGE, DOUG; LEWIS, JOHNNYE; DURANT, JOHN L.

2008-01-01

We tested the hypothesis that runoff of uranium-bearing particles from mining waste disposal areas was a significant mechanism for redistribution of uranium in the northeastern part of the Upper Puerco River watershed (New Mexico). However, our results were not consistent with this hypothesis. Analysis of >100 sediment and suspended sediment samples collected adjacent to and downstream from uranium source areas indicated that uranium levels in the majority of the samples were not elevated above background. Samples collected within 50 m of a known waste disposal site were subjected to detailed geochemical characterization. Uranium in these samples was found to be highly soluble; treatment with synthetic pore water for 24 h caused dissolution of 10–50% of total uranium in the samples. Equilibrium uranium concentrations in pore water were >4.0 mg/L and were sustained in repeated wetting events, effectively depleting soluble uranium from the solid phase. The dissolution rate of uranium appeared to be controlled by solid-phase diffusion of uranium from within uranium-bearing mineral particles. X-ray adsorption spectroscopy indicated the presence of a soluble uranyl silicate, and possibly a uranyl phosphate. These phases were exhausted in transported sediment suggesting that uranium was readily mobilized from sediments in the Upper Puerco watershed and transported in the dissolved load. These results could have significance for uranium risk assessment as well as mining waste management and cleanup efforts. PMID:18589950

A new reconstruction of the Paleozoic continental margin of southwestern North America: Implications for the nature and timing of continental truncation and the possible role of the Mojave-Sonora megashear

USGS Publications Warehouse

Stevens, C.H.; Stone, P.; Miller, J.S.

2005-01-01

Data bearing on interpretations of the Paleozoic and Mesozoic paleogeography of southwestern North America are important for testing the hypothesis that the Paleozoic miogeocline in this region has been tectonically truncated, and if so, for ascertaining the time of the event and the possible role of the Mojave-Sonora megashear. Here, we present an analysis of existing and new data permitting reconstruction of the Paleozoic continental margin of southwestern North America. Significant new and recent information incorporated into this reconstruction includes (1) spatial distribution of Middle to Upper Devonian continental-margin facies belts, (2) positions of other paleogeographically significant sedimentary boundaries on the Paleozoic continental shelf, (3) distribution of Upper Permian through Upper Triassic plutonic rocks, and (4) evidence that the southern Sierra Nevada and western Mojave Desert are underlain by continental crust. After restoring the geology of western Nevada and California along known and inferred strike-slip faults, we find that the Devonian facies belts and pre-Pennsylvanian sedimentary boundaries define an arcuate, generally south-trending continental margin that appears to be truncated on the southwest. A Pennsylvanian basin, a Permian coral belt, and a belt of Upper Permian to Upper Triassic plutons stretching from Sonora, Mexico, into westernmost central Nevada, cut across the older facies belts, suggesting that truncation of the continental margin occurred in the Pennsylvanian. We postulate that the main truncating structure was a left-lateral transform fault zone that extended from the Mojave-Sonora megashear in northwestern Mexico to the Foothills Suture in California. The Caborca block of northwestern Mexico, where Devonian facies belts and pre-Pennsylvanian sedimentary boundaries like those in California have been identified, is interpreted to represent a missing fragment of the continental margin that underwent ???400 km of left-lateral displacement along this fault zone. If this model is correct, the Mojave-Sonora megashear played a direct role in the Pennsylvanian truncation of the continental margin, and any younger displacement on this fault has been relatively small. ?? 2005 Geological Society of America.

Dielectric properties of water under extreme conditions and transport of carbonates in the deep Earth.

PubMed

Pan, Ding; Spanu, Leonardo; Harrison, Brandon; Sverjensky, Dimitri A; Galli, Giulia

2013-04-23

Water is a major component of fluids in the Earth's mantle, where its properties are substantially different from those at ambient conditions. At the pressures and temperatures of the mantle, experiments on aqueous fluids are challenging, and several fundamental properties of water are poorly known; e.g., its dielectric constant has not been measured. This lack of knowledge of water dielectric properties greatly limits our ability to model water-rock interactions and, in general, our understanding of aqueous fluids below the Earth's crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the Earth's upper mantle, and we predicted the solubility products of carbonate minerals. We found that MgCO3 (magnesite)--insoluble in water under ambient conditions--becomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon. Our results suggest that aqueous carbonates could leave the subducting lithosphere during dehydration reactions and could be injected into the overlying lithosphere. The Earth's deep carbon could possibly be recycled through aqueous transport on a large scale through subduction zones.