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1

Miocene sedimentation in the Sigsbee Abyssal Plain, Gulf of Mexico  

E-print Network

graded Miocene sands with interbedded laminites and mineralogical assemblages of plutonic and volcanic rock fragments from the cored depths of 800-900 meters below the sediment-water interface. This anomalous occurrence of coarse sand and rock... graded Miocene sands with interbedded laminites and mineralogical assemblages of plutonic and volcanic rock fragments from the cored depths of 800-900 meters below the sediment-water interface. This anomalous occurrence of coarse sand and rock...

Kuzela, Robert Christian

2012-06-07

2

Bioturbation, geochemistry and geotechnics of sediments affected by the oxygen minimum zone on the Oman continental slope and abyssal plain, Arabian Sea  

Microsoft Academic Search

We investigate the way the oxygen minimum zone (OMZ) alters interactions between bioturbation and sediment geochemistry, and geotechnical properties. Sediments are compared within and below the OMZ on the Oman continental slope and adjacent abyssal plain during the post monsoonal autumn season. Quantitative measurements were made of Eh and pH, of total organic matter (TOM) and carbonate, of water content

Azra Meadows; Peter S Meadows; Fraser J. C West; John M. H Murray

2000-01-01

3

Food web structure of the benthic community at the Porcupine Abyssal Plain (NE Atlantic): a stable isotope analysis  

Microsoft Academic Search

The deep-sea benthic community at the Porcupine Abyssal Plain (NE Atlantic) is a highly food limited system. The annual input of sedimenting phytodetritus, which reaches the sea floor around May\\/June, is the major input of energy. The relative trophic position of the most abundant components of the benthos (90 species or higher taxonomic groups), including meiofaunal, macrofaunal, and megafaunal organisms,

K. Iken; T. Brey; U. Wand; J. Voigt; P. Junghans

2001-01-01

4

A case of post-depositional aerobic degradation of terrestrial organic matter in turbidite deposits from the Madeira Abyssal Plain  

Microsoft Academic Search

A set of oxidized and unoxidized sediment intervals from the f-turbidite identified in two piston cores from the Madeira Abyssal Plain (MAP) was analyzed for calcium carbonate, total organic carbon (TOC), total nitrogen (TN), stable carbon composition of TOC (?13Ctoc), total hydrolyzable amino acids (THAA), total neutral sugars (TSUG), lignin phenols (LIG), two different lipid biomarkers of marine phytoplankton origin

Fredrick G. Prahl; Gert J. De Lange; Sven Scholten; Gregory L. Cowie

1997-01-01

5

Heavy mineral dispersal patterns of the abyssal plain and Louisiana inner shelf of the Gulf of Mexico  

E-print Network

. , Colorado School of Mines Directed by: Dr. William R. Bryant The Mississippi River system acted as the major source of detrital sediment to the Gulf of. Mexico during both Pleistocene and Holocene times. Sands, silts, and clays from the Mississippi were... provinces are the Sigsbee abyssal plain and the con- tinental shelf of Texas and Louisiana, Because of their proximity to, or available access from, the Mississippi River, both areas derive a considerable amount of sediment from this input source. One...

Moore, Walter Richard

2012-06-07

6

Tectonic evolution of the Perth Abyssal Plain's Quiet Zone, Southeast Indian Ocean  

NASA Astrophysics Data System (ADS)

During the Late Jurassic period, the Greater-Indian plate was torn away from Australia, dissociating East Gondwanaland. The Perth Abyssal Plain (PAP) is the southernmost rift segment along the western Australian margin, and has an onset age of ~136 Ma. New marine magnetic and swath bathymetry data, crossing the entire PAP, were acquired recently on geophysical cruise ss2011v06 aboard the R/V Southern Surveyor. These have lead to the outline of conjugate Indian and Australian M-series isochrons in the east and west PAP, respectively [1]. Yet, most of the PAP was created during the Cretaceous Normal Superchron (CNS, 121-83 Ma), a period of no geomagnetic field reversals, hence no comprehensive tectonic model for the PAP exists . Here we present preliminary findings of an analytic bathymetric and magnetic investigation aimed at elucidating the PAP's quiet zone. Recent discoveries regarding the evolution of the geomagnetic field during the CNS [2] provide new time markers that can be utilized to date the oceanic crust. The magnetic anomaly data exhibit the Q2 anomaly marker (~108 Ma), further constraining the spreading history of the PAP. Together with the ridgelet transform method [3] for automated abyssal hill delineation, we present new constraints on the development of crustal construction processes (spreading location, direction and rates) that took place along the PAP spreading center. References: [1] S.E. Williams, J.M. Whittaker, R. Granot, R.D. Muller (in preparation), New constraints on the seafloor spreading history in the Perth Abyssal Plain. [2] Granot, R., J. Dyment, and Y. Gallet (2012), Geomagnetic field variability during the Cretaceous Normal Superchron, Nature Geoscience, 5(3), 220-223. [3] Downey, N. J. and R. W. Clayton (2007), A ridgelet transform method for constraining tectonic models via abyssal-hill morphology, Geochemistry Geophysics Geosystems, 8, Q03004, doi: 10.1029/2006GC001440.

Ehrlich, Zohar Louis; Granot, Roi; Williams, Simon E.

2013-04-01

7

The Characterization of Organic Matter in Abyssal Sediments, Pore Waters and Sediment Traps  

Microsoft Academic Search

\\u000a Substantial information regarding the history, source and transfer of both carbon and nitrogen to and within the deep sea\\u000a lies in the chemical and isotopic signals of organic materials. Isotopic and chemical characterization of sediment trap samples\\u000a indicate that the captured particulate materials are an organic rich food source for abyssal organisms which become highly\\u000a altered at or just below

Stephen A. Macko

8

STUDY OF ABYSSAL SEAFLOOR ISOLATION OF CONTAMINATED SEDIMENTS CONCLUDED  

EPA Science Inventory

Recognizing the rapidly decreasing availability of disposal sites on land, in 1993 Congress directed the Department of Defense to assess the technical and scientific feasibility of isolating contaminated dredged material on the abyssal seafloor. The Naval Research Laboratory (NRL...

9

High-resolution seismic stratigraphy of the Galicia Bank Region and neighbouring abyssal plains (NW Iberian continental margin)  

Microsoft Academic Search

The high-resolution seismic stratigraphy of the Galicia Bank Region and adjacent deposits of the neighbouring Iberian and Biscay Abyssal Plains was included as part of the geological studies conducted in the area where the oil-tanker Prestige wreck is located. This seismic stratigraphy is characterized by five seismic units (5 to 1, from oldest to youngest) lying above an irregular acoustic

G. Ercilla; S. García-Gil; F. Estrada; E. Gràcia; A. Vizcaino; J. T. Váquez; S. Díaz; F. Vilas; D. Casas; B. Alonso; J. Dañobeitia; M. Farran

2008-01-01

10

Neotectonic morphotructures in the junction zone of the Cape Verde Rise and Cape Verde Abyssal Plain, Central Atlantic  

Microsoft Academic Search

Acoustic profiling carried out with an Edgetech 3300 prophilograph in the junction zone of the Cape Verde Rise, Cape Verde Abyssal Plain, and Grimaldi and Bathymetrists seamounts in the Central Atlantic during Cruise 23 of the R\\/V Akademik Nikolaj Strakhov allowed us to obtain new data on neotectonic deformations in the ocean and to propose their interpretation. It has been

S. G. Skolotnev; S. Yu. Kolodyazhny; N. V. Tsukanov; N. P. Chamov; S. Yu. Sokolov

2009-01-01

11

Export of organic carbon and biominerals derived from 234Th and 210Po at the Porcupine Abyssal Plain  

NASA Astrophysics Data System (ADS)

The simultaneous estimation of particulate organic carbon (POC), particulate inorganic carbon (PIC) and biogenic silica (BSi) export fluxes is key to the study of carbon export due to the hypothesized role of biominerals in the sinking of organic particles. This paper presents of the first attempts to measure downward fluxes of POC, PIC and BSi from the surface ocean using both the 234Th-238U and the 210Po-210Pb disequilibria and drifting sediments trap synchronously at the Porcupine Abyssal Plain in summer 2009. The combined use of the three techniques allowed us to analyze their suitability not only for POC flux estimates, but also as tracers of PIC and BSi fluxes. POC and biomineral/radionuclide ratios were measured in two size fractions to better understand differences between 234Th derived export and 210Po derived export. 210Po derived POC and biomineral fluxes were unexpectedly closer to POC and biomineral fluxes recorded by sediment traps than 234Th derived POC and biomineral fluxes which were higher than obtained from the other two approaches. We suggest that 210Po, because of its biogeochemical behavior, is a better proxy for POC and mineral fluxes than is 234Th in post bloom conditions. The contribution of smaller (1-53 ?m) particles to flux is also considered in order to explain the differences in derived fluxes.

Le Moigne, F. A. C.; Villa-Alfageme, M.; Sanders, R. J.; Marsay, C.; Henson, S.; García-Tenorio, R.

2013-02-01

12

Late Quaternary paleoenvironmental changes revealed by multi-proxy records from the Chukchi Abyssal Plain, western Arctic Ocean  

NASA Astrophysics Data System (ADS)

Late Quaternary paleoenvironmental changes in the western Arctic Ocean are revealed by multi-proxy records of core 03M03 from the Chukchi Abyssal Plain (CAP). Proxy parameters include lithology, grain size fractions, and mineralogy and petrology of ice-rafted detritus (IRD), element contents, biogenic components, ?18O, ?13C and Mg/Ca of planktonic foraminifera Neogloboquadrina pachyderma (sin.) (Nps). Seven IRD (> 250 ?m) peaks are interpreted as marking detrital input by rafting sea ice or icebergs during MIS 3 interstadials and early MIS 1. High MnO, CaO and MgO contents and high Ca/Al and Mg/Al ratios during MIS 3 and MIS 1 correspond to increases in ice-rafted detrital carbonates and the synchronous declines in siliciclastic elements (e.g., Al2O3, Fe2O3). Therefore, these warmer periods were characterized by a high detrital carbonate input entrained in icebergs from the Canadian Arctic Archipelago coeval with an increased input of Mn through rivers and/or coastal erosion. Relatively stable contents of siliciclastic elements and their ratios in the grayish sediment units are interpreted from turbid surface water plumes or nepheloid flows delivered by meltwater and/or brine rejection from ice-sheet margins at the Arctic Ocean periphery. Relatively stable clay- and silt-sized fractions were attributed mainly to sea ice entrainment over glacial-interglacial cycles. High foraminiferal abundances in the brown units during MIS 3 and 1 are related to enhanced calcareous plankton productivity under more open water conditions and/or the incremental input of Atlantic water masses. Relatively high TOC and opal contents in the grayish units of MIS 3 appear to have accumulated by lateral transport of organic matter from the Chukchi shelf to the deep abyssal plain. Lower contents of biogenic material in the brown units probably result from increased dilution by rapid IRD deposition, and from early diagenetic degradation. Depletions in Nps-?18O and -?13C concurrent with high foraminiferal abundances and IRD peaks within the brown units of MIS 3 and 1 are indicative of meltwater pulses, as previously documented across the Arctic Ocean. However, several Nps-?18O and -?13C depletions between the brown units B3 and B2 in MIS 3 could have resulted from enhanced sea ice formation. The Nps-Mg/Ca has the potential to record paleotemperature changes in the Arctic region, but still awaits a better calibration of the Nps-Mg/Ca-temperature relationship with results from core-tops, sediment traps, and plankton tows.

Wang, Rujian; Xiao, Wenshen; März, Christian; Li, Qianyu

2013-09-01

13

Study of abyssal seafloor isolation of contaminated sediments concluded  

SciTech Connect

Recognizing the rapidly decreasing availability of disposal sites on land, in 1993 Congress directed the Department of Defense to assess the technical and scientific feasibility of isolating contaminated dredged material on the abyssal seafloor. The Naval Research Laboratory (NRL) conducted and managed the assessment, which was funded during its first year by the Strategic Environmental Research and Development Program and in the following two years by the Defense Advanced Research Projects Agency. NRL carried out the projects in collaboration with participants from academic institutions and industrial organizations. The seafloor isolation concept is an attractive management option for contaminated dredged material because, if abyssal isolation is feasible and environmentally sound, air, land, or water supplies would not be contaminated. The participants concluded that it is technically and environmentally feasible. In ports where shipping costs are high, abyssal seafloor isolation is a cost-competitive strategy. They also outlined the architecture of a system to monitor conditions at the site and to detect and measure possible leaks of contaminated material.

Valent, P.

1998-12-31

14

Hydrocarbon potential, organic matter diagenesis, sedimentology, and paleoenvironment of upper Mesozoic dark shales, northern Himalayas and Argo abyssal plain  

SciTech Connect

The Late Jurassic was a time favorable for the deposition of black shale-type sediments in shallow environments as known from circum-North Atlantic basins, North Sea, and Himalayan Tethys regions. Locally these shales have excellent hydrocarbon source potential. The site of the Spiti shales in the Thakkola region of north-central Nepal provides the opportunity to study a long-term (Oxfordian-Tithonian) stable, shallow, and oxygen-depleted environment. Strata with calcareous benthic communities show that the environment was not anoxic. Organic geochemical and sedimentological analyses on the Spiti shales (Oxfordian-Valanginian) were done to understand the hydrocarbon potential, organic matter diagenesis, sedimentology, and paleoenvironment of this sequence. The depositional environment changed, driven by tectono-eustatic and climatic events, from an open shelf (approximately 250 m) with low amounts of detrital input and rich macrofossil communities to an extremely shallow, partly continental environment with intercalations of quartzose channel fill, silty shales, rare lumachelle layers, and coal seams. Paleocurrents suggest a north-facing continental margin bordering the Tethys Sea. The organic matter changed from marine (Jurassic) to terrestrial in the Cretaceous. Analysis of coeval strata, deposited in the deep-marine environment off the northern Indian shelf (contiguous with the present-day Argo abyssal plain), demonstrates the changing shallow to deep-water hydrocarbon potential. It reflects the more advanced organic matter maturation of the onshore material due to Himalayan tectonics and allows tracing the transport of the organic matter.

Thurow, J.; Gibling, M.

1989-03-01

15

The Ionian Abyssal Plain - closure of a remnant Mesozoic oceanic domain: subbottom structures, deep deformation and the Calabrian subduction zone  

NASA Astrophysics Data System (ADS)

The Ionian Abyssal Plain (IAP), located in the Central Mediterranean area is a deep triangular shaped basin, surrounded by the Calabrian subduction zone to the NW, the Mediterranean Ridge to the NE and the Medina Ridges to the South. Available heat flow measurements show very low values under the Ionian Abyssal plain, suggesing a very old age of 180-200 Ma for the basin. The Bouguer gravity anomaly map shows only a strong positive anomaly in this region and the depth of the Moho is around 16 to 18 km corresponding to high refraction velocities of 8.1-8.2 km/s. The Ionian basin is interpreted as one of the oldest basins in the Mediterranean area, and is thought to represent a remnant part of the Mesozoic Tethyan ocean. Due to the complex relative motions of microplates and blocks, currently, the oceanic lithosphere of the Ionian basin is being simultaneously consumed by subduction to the NE beneath the Hellenic system and to the NW beneath Calabria. We present the most relevant lines of the Archimede multi-channel seismic cruise (1997, R/V Le Nadir) crossing the Ionian Abyssal Plain and the Calabrian subduction zone. Interpretation of this seismic dataset is based on correlation with published seismic data and with ESP results. Beneath the IAP, we identify a thick sedimentary cover (> 5km) from the Jurassic to the Plio-Quaternary in age, which overlies the oceanic basement. The Pre-Messinian sequences are affected by a set of NE/SW striking compressional faults with some syn-tectonic basins NW of these faults. These features are interpreted as a re-activated set of normal faults, possibly formed during rifting and/or subsequent accretion of oceanic crust. The orientation of the subbottom structures and the thickness of the Messinian deposits in the south-eastern part of the IAP may be linked with the presence of these faults and their activity through time. On the Calabrian side of the IAP, the Post-Messinian sequences are accreted to the Calabrian wedge. The weak rheology of the Messinian salts acts as the décollement level in the frontal part of the wedge. Repeated imbricate thrusting within in the Calabrian wedge allows the thickening of the Messinian sediments from 1200 m beneath the IAP to 2400 m 30 km away from the deformation front. A major tectonic structure is imaged east of the Malta Escarpment by the Archimede profiles, it offsets the top Pre-Messinian deposits by 0.5 - 1 sTWT increasing from S to N. This N150°E oriented lithospheric fault is interpreted as a tear fault (“STEP” fault) which has allowed the roll-back of the Ionian slab. The activity of these faults and the Calabrian and Mediterranean subduction zones have been reconstructed through time to reach the present-day physiology of the remnant Ionian basin. The analysis of their activity will allow a better understanding of the closure of the Ionian domain.

Gallais, F.; Gutscher, M.; Graindorge, D.; Klaeschen, D.

2010-12-01

16

Organic matter accumulation, sulfate reduction, and methane generation in a turbidite sequence on the Iberia Abyssal Plain  

SciTech Connect

Organic matter can be transferred and redeposited from continental margins to the deep-sea by turbidity currents and slumps. An opportunity to investigate the consequences of turbidite deposition on sediment organic matter was provided by a transect of four closely spaced drill sites sampled during ODP Leg 149 in a Pliocene-Pleistocene distal turbidite sequence on the landward edge of the Iberia Abyssal Plain. Organic carbon concentrations average ca 0.7% in sediments from Sites 897 and 898 and ca 0.4% at Sites 899 and 900. Headspace concentrations of interstitial methane exceed 100,000 ppm in sediments from Sites 897 and 898 but are essentially zero in those from Sites 899 and 900. Methane concentrations do not rise until interstitial sulfate concentrations are virtually depleted, suggesting the presence of deep in situ methanogenic bacterial activity at Sites 897 and 898 and its absence at Sites 899 and 900. Two factors associated with the turbidity flows that created the sedimentary sequence evidently influenced post-depositional diagenesis at these sites. The principal factor is that the rapidly deposited turbidite sequences at Sites 897 and 898 protected organic matter from oxic, early degradation and thereby permitted anoxic, later degradation to proceed. In contrast, organic matter in the more slowly deposited turbidites at Sites 899 and 900 was oxidized soon after deposition and was therefore not available for later microbial utilization. A lesser factor is that the turbidity flows may have obtained their entrained organic matter from different environments and consequently delivered organic matter with different characteristics.

Meyers, P.A.; Silliman, J.E. (Univ. of Michigan, Ann Arbor, MI (United States)); Shaw, T.J. (Univ. of South Carolina, Columbia, SC (United States))

1996-01-01

17

Organic matter accumulation, sulfate reduction, and methane generation in a turbidite sequence on the Iberia Abyssal Plain  

SciTech Connect

Organic matter can be transferred and redeposited from continental margins to the deep-sea by turbidity currents and slumps. An opportunity to investigate the consequences of turbidite deposition on sediment organic matter was provided by a transect of four closely spaced drill sites sampled during ODP Leg 149 in a Pliocene-Pleistocene distal turbidite sequence on the landward edge of the Iberia Abyssal Plain. Organic carbon concentrations average ca 0.7% in sediments from Sites 897 and 898 and ca 0.4% at Sites 899 and 900. Headspace concentrations of interstitial methane exceed 100,000 ppm in sediments from Sites 897 and 898 but are essentially zero in those from Sites 899 and 900. Methane concentrations do not rise until interstitial sulfate concentrations are virtually depleted, suggesting the presence of deep in situ methanogenic bacterial activity at Sites 897 and 898 and its absence at Sites 899 and 900. Two factors associated with the turbidity flows that created the sedimentary sequence evidently influenced post-depositional diagenesis at these sites. The principal factor is that the rapidly deposited turbidite sequences at Sites 897 and 898 protected organic matter from oxic, early degradation and thereby permitted anoxic, later degradation to proceed. In contrast, organic matter in the more slowly deposited turbidites at Sites 899 and 900 was oxidized soon after deposition and was therefore not available for later microbial utilization. A lesser factor is that the turbidity flows may have obtained their entrained organic matter from different environments and consequently delivered organic matter with different characteristics.

Meyers, P.A.; Silliman, J.E. [Univ. of Michigan, Ann Arbor, MI (United States); Shaw, T.J. [Univ. of South Carolina, Columbia, SC (United States)

1996-12-31

18

Neotectonic morphotructures in the junction zone of the Cape Verde Rise and Cape Verde Abyssal Plain, Central Atlantic  

Microsoft Academic Search

Acoustic profiling carried out with an Edgetech 3300 prophilograph in the junction zone of the Cape Verde Rise, Cape Verde\\u000a Abyssal Plain, and Grimaldi and Bathymetrists seamounts in the Central Atlantic during Cruise 23 of the R\\/V Akademik Nikolaj Strakhov allowed us to obtain new data on neotectonic deformations in the ocean and to propose their interpretation. It has been

S. G. Skolotnev; S. Yu. Kolodyazhny; N. V. Tsukanov; N. P. Chamov; S. Yu. Sokolov

2009-01-01

19

The peridotite ridge province in the southern Iberia Abyssal Plain: Seismic constraints revisited  

NASA Astrophysics Data System (ADS)

west Iberia margin has become the type example of a magma-starved margin in which extension during breakup led to the exhumation of mantle rocks apparently over a broad area. Much of our understanding of this process is based on geophysical and drilling data from the southern Iberia Abyssal Plain, where the seaward part of the region of exhumed mantle is composed of a series of margin-parallel basement ridges. Here we analyze wide-angle and normal-incidence seismic data from a series of intersecting profiles across this peridotite ridge province and develop a three-dimensional picture of its structure. Using these seismic data, we infer a location and age (magnetic anomaly M1; 125-127 Ma) of first-formed oceanic crust in this region that are consistent with Ocean Drilling Program data and data from the conjugate margin. We infer that the peridotite ridge province is about 70 km wide with strong serpentinization (>75%) at the top of the basement reducing to much lower degrees (< 25%) around 2 km below. We map the geometry of some prominent reflectors on the landward margin of the peridotite ridge province that likely represent detachment faults and show that one of these has a domal structure similar to that of detachment faults at slow to ultraslow spreading mid-ocean ridges.

Minshull, T. A.; Dean, S. M.; Whitmarsh, R. B.

2014-03-01

20

Seismicity and seismotectonics of the diffusive Iberian/African plate boundary: Horseshoe Abyssal Plain and Gorringe Bank  

NASA Astrophysics Data System (ADS)

In the area to the west of the Gibraltar Arc the plate boundary between Africa and Iberia is poorly defined. The deformation in the area is forced by the slow NW-SE convergence of 4 mm/yr between the oceanic domains of Iberia/Eurasia and Africa and is accommodated over a 200 km broad tectonically-active deformation zone. The region, however, is also characterized by large earthquakes and tsunamis, such as the 1969 Mw=7.9 Horseshoe Abyssal Plain earthquake and the November 1, 1755 Great Lisbon earthquake with an estimated magnitude of Mw~8.5. The exact location of the source of the 1755 Lisbon earthquake is still unknown. Recent work may suggest that the event occurred in the vicinity of the Horseshoe fault, an oblique thrust fault. However, estimates of tsunami arrival times suggested a source near the Gorringe Bank, a ~180 km-long and ~70 km-wide ridge that has a relieve of ~5000 m. Deep Sea Drilling (DSDP) and rock samples indicated that the bank is mainly composed of serpentinized peridotites with gabbroic intrusions, perhaps being created by overthrusting of the Horseshoe Abyssal Plain onto the Tagus Abyssal Plain in NW direction. Further, the Horseshoe Abyssal Plain is marked by the presence of compressive structures with a roughly NE-SW orientation and E-W trending, segmented, crustal-scale, strike slip faults that extend from the Gorringe Bank to the Gibraltar Arc in the eastern Gulf of Cadiz, which were called "South West Iberian Margin" or SWIM faults. The fault system may mark a developing Eurasia-Africa plate boundary. Two local seismic networks were operated in the area. First, a network of 14 ocean-bottom seismometers (OBS) was operated between April and October 2012 in the vicinity of the Horseshoe fault between 10°W to 11°W, and 35°50'N to 36°10'N. From October 2013 to March 2014 a second network of 15 OBS monitored seismicity at the Gorringe Bank. Both networks benefitted from seismic stations operated in Portugal. The first network provided in the order of 100 locale earthquakes occurring with the network. Most earthquakes in the Horseshoe occurred at a depth of 40-60 km, either in oceanic or unroofed continental mantle. The large source depth of events observed in the Horseshoe Abyssal Plain supports the idea that large catastrophic earthquakes, like the Great Lisbon earthquake of 1755, may indeed occur in the area.

Grevemeyer, Ingo; Lange, Dietrich; Matias, Luis

2014-05-01

21

Temporal changes (1989-1999) in deep-sea metazoan meiofaunal assemblages on the Porcupine Abyssal Plain, NE Atlantic  

NASA Astrophysics Data System (ADS)

Trends among major metazoan meiofaunal taxa were investigated based on 56 deployments of a multicorer at 10 time points over a period of 11 years (1989-1999) at the Porcupine Abyssal Plain Sustained Observatory site (PAP-SO: 48°50'N 16°30'W, 4850 m depth). This area is characterised by a strong seasonality in the deposition of organic matter to the seafloor and by the massive increase in the density of holothurian species since 1996, the so-called ' Amperima event'. Total meiofaunal densities ranged from 346 to 1074 ind.×10 cm -2 and showed a significant increase with time when time was represented by cruises, years and the ' Amperima period' (1996-1999) vs. the pre- Amperima period (1989-1994). This pattern was driven mainly by the nematodes, which were the dominant taxon (˜90% of total abundance). The third most abundant group, the polychaetes, also increased significantly in abundance over the time series, while the ostracods showed a significant decrease. Most other taxa, including the second-ranked group, the copepods (harpacticoids and nauplii), did not exhibit significant temporal changes in abundance. Ordination of taxon composition showed a shift from the pre- Amperima to the Amperima periods, a trend supported by the significant correlation between the x-ordinate and time. The majority (52-75%) of meiofaunal animals inhabited the top 2 cm of the 5 cm sediment cores analysed. There were significant increases in the proportion of total meiofauna, nematodes and copepods (but not polychaetes) inhabiting the 0-1 cm layer over time (represented by cruises) and between the pre- Amperima and Amperima periods in the case of copepods and polychaetes. During the intensively sampled period (1996-1997), there were indications of seasonal changes in the vertical distribution patterns of total meiofauna and nematodes within the sediment. We discuss the potential link between temporal variations in organic matter flux to the seafloor and meiofaunal populations, considering both qualitative and quantitative changes in fluxes and how they may be linked to climate variations.

Kalogeropoulou, V.; Bett, B. J.; Gooday, A. J.; Lampadariou, N.; Martinez Arbizu, P.; Vanreusel, A.

2010-08-01

22

Fate of corrosion products released from stainless steel in marine sediments and seawater. Part 4: Hatteras abyssal red clay  

SciTech Connect

A study in which neutron-activated 347 stainless steel was exposed to surficial sediment from a site in the Hatteras Abyssal Plain of the Northwest Atlantic Ocean is described. This sediment consists of approx. 20% CaCO/sub 3/, which could lead to the formation of calcareous scale on the metal surface and reduce the corrosion rate. The distribution of indigenous metals among different chemical fractions shows that extractable Cr, Mn, Fe, Co, and Zn were associated with amorphous Mn and Fe oxides. Most of the remaining extractable Cr, and about a third of the extractable Cu appear to have been weakly complexed. Major fractions (25 to 36%) of extractable Mn, Co and Ni were present as adsorbed cations. Organic complexation appears to account for a large amount of extractable Fe, Ni, Cu and Zn. Neutron-activated 347 stainless steel specimens were exposed to sediment slurry under aerobic and non-oxygenated conditions for a period of 94 days. The redox potential measurements for air-sparged and N/sub 2/, CO/sub 2/-sparged sediment slurries were +410 and +60 mv, respectively. The presence of 0/sub 2/ produced increased amounts of corrosion products. Chemical extraction showed that relatively labile substances constituted about 84% of the /sup 60/Co activity released in aerated sediment. Relatively labile substances constitute about 82% of the total /sup 60/Co activity released under non-oxygenated conditions. A large fraction of /sup 60/Co which was in the soluble or easily dissolved forms under non-oxygenated conditions appears to have been more strongly adsorbed to the sediment under aerated conditions.

Schmidt, R.L.

1982-07-01

23

Connections between climate, food limitation, and carbon cycling in abyssal sediment communities  

PubMed Central

Diverse faunal groups inhabit deep-sea sediments over much of Earth's surface, but our understanding of how interannual-scale climate variation alters sediment community components and biogeochemical processes remains limited. The vast majority of deep-sea communities depend on a particulate organic carbon food supply that sinks from photosynthetically active surface waters. Variations in food supply depend, in part, on surface climate conditions. Proposed ocean iron fertilization efforts are also intended to alter surface production and carbon export from surface waters. Understanding the ecology of the abyssal sediment community and constituent metazoan macrofauna is important because they influence carbon and nutrient cycle processes at the seafloor through remineralization, bioturbation, and burial of the sunken material. Results from a 10-year study in the abyssal NE Pacific found that climate-driven variations in food availability were linked to total metazoan macrofauna abundance, phyla composition, rank-abundance distributions, and remineralization over seasonal and interannual scales. The long-term analysis suggests that broad biogeographic patterns in deep-sea macrofauna community structure can change over contemporary timescales with changes in surface ocean conditions and provides significant evidence that sediment community parameters can be estimated from atmospheric and upper-ocean conditions. These apparent links between climate, the upper ocean, and deep-sea biogeochemistry need to be considered in determining the long-term carbon storage capacity of the ocean. PMID:18974223

Ruhl, Henry A.; Ellena, Jacob A.; Smith, Kenneth L.

2008-01-01

24

Paenibacillus abyssi sp. nov., isolated from an abyssal sediment sample from the Indian Ocean.  

PubMed

A Gram-positive, rod-shaped bacterium, designated strain SCSIO N0306(T), was isolated from an abyssal sediment sample collected from the Indian Ocean. The isolate was found to grow optimally at 0-2 % (w/v) NaCl, pH 7.0 and 30 °C. Comparative analysis of the 16S rRNA gene sequence showed that the isolate SCSIO N0306(T) belongs phylogenetically to the genus Paenibacillus, and to be most closely related to P. algorifonticola XJ259(T) (with 95.47 % sequence similarity), sharing less than 95.0 % sequence similarity with all other taxa of this genus. Chemotaxonomic analysis revealed MK-7 as the major isoprenoid quinone, the DNA G+C content was determined to be 45.5 mol%, and anteiso-C15:0, C16:0, and iso-C15:0 were identified as the major fatty acids. On the basis of this polyphasic taxonomic data, isolate SCSIO N0306(T) is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus abyssi sp. nov. is proposed. The type strain is SCSIO N0306(T) (= DSM 26238(T) = CGMCC 1.12987(T)). PMID:25249446

Huang, Xiao-Fang; Wang, Fa-Zuo; Zhang, Wei; Li, Jie; Ling, Juan; Yang, Jian; Dong, Jun-De; Tian, Xin-Peng

2014-12-01

25

Do bottom mixed layers influence 234Th dynamics in the abyssal near-bottom water column?  

Microsoft Academic Search

Dynamics of the natural radioactive particle tracer 234Th (half-life: 24.1 days) within the abyssal water column up to 1000m above bottom and within surface sediments of the northeast Atlantic (Porcupine Abyssal Plain; depth: ?4845m) were investigated. Distributions of transmissometer voltages and potential temperature indicated a subdivision of the near-bottom water column into a benthic mixed layer (BML; thickness: ?10–65m) and

Robert Turnewitsch; Barbara M Springer

2001-01-01

26

Diatom flux reflects water-mass conditions on the southern Northwind Abyssal Plain, Arctic Ocean  

NASA Astrophysics Data System (ADS)

We studied time-series fluxes of diatom particles and their relationship to hydrographic variations from 4 October 2010 through 18 September 2012 using bottom-tethered sediment trap moorings deployed at Station NAP (75° N, 162° W; 1975 m water depth) in the western Arctic Ocean. We observed clear maxima of the diatom valve flux in November-December of both 2010 and 2011, and in August 2011. Diatoms in samples were categorized into 98 taxa. The diatom flux maxima were characterized by many resting spores in November-December and by the sea ice-associated diatom Fossula arctica in August 2011. These assemblages along with abundant clay minerals in the samples suggest a significant influence of shelf-origin materials transported by mesoscale eddies, which developed along the Chukchi Sea shelf break. In contrast, the fluxes of total mass and diatoms were reduced in summer 2012. We hypothesize that this suppression reflects the influx of oligotrophic water originating from the central Canada Basin. A physical oceanographic model demonstrated that oligotrophic surface water from the Beaufort Gyre was supplied to Station NAP from December 2011 to early half of 2012.

Onodera, J.; Watanabe, E.; Harada, N.; Honda, M. C.

2014-10-01

27

Temporal and depth-related differences in prokaryotic communities in abyssal sediments associated with particulate organic carbon flux  

NASA Astrophysics Data System (ADS)

Particulate organic carbon (POC) flux is hypothesized to be the most important parameter influencing activity and biomass of prokaryotic and faunal communities in the abyssal seafloor, but there is little evidence of POC-related changes in community composition of prokaryotes. This hypothesis was tested by 16S rRNA-gene-based analysis of prokaryotic DNA and RNA extracted from abyssal seafloor sediments during periods of low and high POC flux. Fingerprint analysis of prokaryotic communities indicated that approximately 50% of the phylotypes were identical at each sediment horizon, regardless of the temporal variations in POC flux. However, phylotypes were also detected that represented a relatively dynamic component of these communities and were probably strongly influenced by the prevalent POC flux regime. These patterns were also detected in deeper sediment horizons. DNA- and RNA-based community profiles differed, although both approaches had similar community dynamics. Crenarchaeota showed the strongest shift in community composition in response to availability of labile POC, indicating that POC flux may have a more pronounced impact on crenarchaeal communities than on bacterial communities. The high number of phylotypes common to each sample time suggests that both standing stock and active prokaryotic communities are stable.

Moeseneder, M. M.; Smith, K. L.; Ruhl, H. A.; Jones, D. O. B.; Witte, U.; Prosser, J. I.

2012-12-01

28

Anomalous Heat Flow and Basement Depth in the Newfoundland Basin Ocean-Continent Transiton Compared With the Iberia Abyssal Plain Conjugate  

NASA Astrophysics Data System (ADS)

A total of 30 new heat flow stations were taken in the Newfoundland Basin, in conjunction with seismic reflection and refraction profiles of the SCREECH and MARIPROBE programs, in order to constrain its lithospheric thermal structure. This was the first use of a new heat flow probe that allows high resolution sampling from up to 48 thermistors over a 4-6-m long sensor string, although only 24 sensors were used for these measurements. Data were taken at three multi-penetration sites: HF1 (12 stations) on oceanic crust seaward of magnetic anomaly M0 along Line 1 (SE of Flemish Cap); and HF2 (12 stations) and HF3 (8 stations) on Line 3 (NW of the Newfoundland Seamounts) on thin oceanic crust landward of the J-anomaly (HF2) and on thin continental crust within the ocean-continent transition (HF3). Temperature gradients are linear at all sites except within the uppermost 1 m at site HF2, where there is evidence for recent variations in bottom water temperature. Average thermal conductivity is very uniform at 0.88±0.8 W/m-K (HF1 and HF2) and 0.85±0.4 W/m-K (HF3). Mean heat flow values are similar at HF1 (57.5±2.1 mW/m2) and HF3 (58.4±2.7 mW/m2) and lower at HF2 (49.5±1.0 mW/m2). Values of heat flow versus sediment-corrected basement depth are consistent with the lithospheric thermal model GDH1 of Stein and Stein (1992) and the expected age at HF2 (130 Ma), but they are 20-50 my younger than expected for HF1 and HF3. In comparison to plots of heat flow and basement depth for the Iberia Abyssal Plain, the Newfoundland Basin shows a significant anomaly in both basement depth (~500-800 m shallower) and heat flow (5-18 mW/m2 higher). The heat flow results indicate that differences in basement depth between these conjugate basins are compensated by significant differences in lithospheric thermal structure and not by differences in shallow crustal structure. The recent discovery of lower Albian diabase sills beneath the Newfoundland Basin at ODP Site 1276, might indicate lithosphere ~15-20 my younger than expected. But this age difference would only result in differences of <200 m in basement depth and ~5 mW/m2 in heat flow, which are less than our observations require.

Louden, K.; Lau, H.

2004-05-01

29

North Atlantic Deep Water and Antarctic Bottom Water variability during the last 200 ka recorded in an abyssal sediment core off South Africa  

Microsoft Academic Search

Benthic ?13C values (F. wuellerstorfi), kaolinite\\/chlorite ratios and sortable silt median grain sizes in sediments of a core from the abyssal Agulhas Basin record the varying impact of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) during the last 200ka. The data indicate that NADW influence decreased during glacials and increased during interglacials, in concert with the global

S. Krueger; D. C. Leuschner; W. Ehrmann; G. Schmiedl; A. Mackensen

30

Retention of Riverine Sediment and Nutrient Loads by Coastal Plain  

E-print Network

accumulated a very large amount of material compared to their annual river loads of sediment (median among floodplain inundation retained greater proportions of riverine loads of nitrogen and phosphorus, but systemsRetention of Riverine Sediment and Nutrient Loads by Coastal Plain Floodplains Gregory B. Noe

31

Geochemical indicators of subsidence in sediment, Terrebonne coastal plain, Louisiana  

SciTech Connect

Sediments comprising the Terrebonne Coastal Plain consist primarily of clays, silts, and peats that fill the depressions between alluvial ridges created by former Mississippi River courses. These sediments are subsiding at variable rates. Depositional history, sedimentation rates, and environment of deposition affect both the types and abundances of diagenetic products found in deltaic sediments. Early diagenesis influences the geotechnical properties of these coastal plain deposits and their local subsidence rates. Diagenetic mineralogy and elemental geochemistry therefore offer clues to understanding some of the variability associated with subsidence in the lower deltaic plain. Results show that diagenetic minerals consist of carbonates (siderite, calcite, dolomite, and rhodochrosite), iron sulfides, vivianite, and iron oxides. In general, siderite and other carbonates as well as pyrite are higher in the fine-grained swamp and lacustrine clays of the upper/middle deltaic plain environments where sediment compaction and subsidence rates are considerably lower than rapidly deposited lower delta and marine deposits. Prodelta clays, for example, contain fewer varieties and lower abundances of diagenetic inclusions than their freshwater fine-grained counterparts. Oxidized sediments of well-drained swamp and natural levee deposits that contain goethite, iron oxides, manganese oxides, and carbonates are stabilized early in their depositional history and therefore do not lend themselves to rapid volume reduction associated with dewatering and compaction. Elemental concentrations can also be interpreted to reflect relative diagenetic activity in the sediments. These preliminary results indicate that close examination of diagenetic mineralogical and geochemical features can provide valuable information concerning the subsidence history of delta plain areas.

Bailey, A.M. (Univ. of Southwestern Louisiana, Lafayette (USA)); Roberts, H.H. (Louisiana State Univ., Baton Rouge (USA))

1990-09-01

32

Turbidite pathways in Cascadia Basin and Tufts abyssal plain, Part A, Astoria Channel, Blanco Valley, and Gorda Basin  

USGS Publications Warehouse

This open-file report was prepared in support of the USGS Earthquake Hazards of Cascadia Project. The primary objective of this phase of the project is to determine recurrence intervals of turbidites in Cascadia basin-floor channel systems and evaluate implications of this event record for the paleoseismic history of the Cascadia subduction zone. The purpose of this study is to determine whether the canyon/channel systems themselves are blocked or deformed in such a way that the downstream turbidite stratigraphy might be biased. To accomplish this investigation approximately 7500 kilometers of pre-existing 3.5 KHz seismic data were evaluated to determine the direction and extent of the Astoria Channel/pathway system, which originates at the base of the Astoria Fan. Additionally, distribution and thickness of turbidite sediment sequences were determined along each identified pathway. Bathymetery and distance were used to determine gradients along the main pathway axis and for each of the secondary pathways that feed into it. Channel pathways were identified on the basis of channel phyisiography, where visible at the seafloor, subbottom channel configuration, and acoustic packets of sediments that might represent turbidite deposits. A principal result of this study is that the Astoria Channel/pathway extends continuously from the base of the Astoria Fan southward along the base of the continental slope through the Blanco Valley, then heads southwestward through the Gorda Basin and into the region of the Escanaba Trough. Additionally it was determined that the Astoria Channel is filled and basically buried for it's full length south of 44 degrees latitude. The 44 North Slump, as defined by Goldfinger (1999, see Map 3 ref.), may have been instrumental in blocking the pathway and thus contributed to the filling of the channel/pathway. Sheets 1 and 2 show the Astoria and secondary turbidite pathways highlighted in blue. Ship survey tracklines are shown for the area studied; they are time and date coded, and color keyed to each ship ID data base listed at the bottom of each sheet. The first letter in the cruise ID is an abbreviation letter for the ship name, the following numbers represent the consecutive cruise number of that year, followed by the year number. The letters at the end of the ID represent the survey area, ie. NC- northern California, NP- north Pacific. Locations of selected sample seismic sections illustrated on sheets 3-5 also are shown. Scales for each of the sheets are the same as for sheets 3-5, which allows for overlaying of track data onto the interpretations shown on Maps A-C. Sheets 3 (MAP A), 4 (MAP B), and 5 (MAP C) show channel pathway location, bathymetric depth based on the USGS COW data base (Ca/Or/Wa), pathway morphology, and thickness of turbidite sediment fill at various locations. The interpreted turbidite sediments are color highlighted on the selected seismic sections to differentiate them from the typical deep sea sediments below and to the side of the turbidite pathways. Thickness of sediment fill, in meters, is shown along major pathways in white circular highlights. The data and interpretations rest on a background of USGS GLORIA side scan sonar imagery (1984) to illustrate the relationship of pathway position to sub sea features. Channel distance points are plotted along channel centerlines at 20,000 m intervals. These points begin at the start of each interpreted channel pathway. A bathymetric depth was assigned to each distance point. These data points were then used to construct channel gradient curves for the Astoria, Eel, Bear Valley, and Mendocino channel pathways. These gradients are plotted on sheet 6 of this report and illustrate the similarities and differences between each of the pathways. Sheet 7 shows various views of the Mendocino/Mattole Canyon heads as an example of useful derivative information of the Seabeam bathymetric data. These views illustrate that the Mendocino pathway probably was directed from it's canyon mouth, to the northwest at an earlier time, but was divert

Wolf, Stephen C.; Hamer, Michael R.

1999-01-01

33

Sediment deformation and plate tectonics in the Gulf of Oman  

Microsoft Academic Search

The continental margin off the Makran coast of Iran and Pakistan is an excellent example of active deformation of sediments at a compressive plate boundary. Seismic reflection profiles across the margin suggest that relatively flat-lying sediments from the Oman abyssal plain are being scraped off the Arabian plate and accreted onto the Eurasian plate in a series of tightly folded

R. S. White; K. Klitgord

1976-01-01

34

Iodine diagenesis in pelagic deep-sea sediments  

Microsoft Academic Search

Nineteen sediment cores from the Madeira, Seine, Tagus and Nares Abyssal Plains and the Alboran Sea have been used to evaluate the speciation, fluxes and diagenesis of iodine in the deep sea. The sediments have surficial molar I\\/C ratios of 10-30 × 10 -4 in excess of previous reported values for planktonic material (~1 × 10 -4 ). Solid phase

H. A. Kennedy; H. Elderfield

1987-01-01

35

Seasonal controls on sediment delivery in a small coastal plain watershed, North Carolina, USA  

E-print Network

years showing that soil erosion is much more rapid and extensive in the Coastal Plain than previouslySeasonal controls on sediment delivery in a small coastal plain watershed, North Carolina, USA the harvesting of crops and mowing of drainage ditches in late autumn, conditions are favorable to soil erosion

Lecce, Scott A.

36

Sediment deposition in the flood plain of Stemple Creek Watershed, northern California  

Microsoft Academic Search

Over the past 150 years, major land use changes have occurred in the Stemple Creek Watershed in northern California that have caused erosion to move soils from the upland to the flood plain, stream channels, and the bay. The purpose of this study is to document the recent (1954 to present) sediment deposition patterns in the flood plain area adjacent

Jerry C Ritchie; Vernon L Finney; Kenneth J Oster; Carole A Ritchie

2004-01-01

37

Sediment deposition in the flood plain of Stemple Creek Watershed, northern California  

NASA Astrophysics Data System (ADS)

Over the past 150 years, major land use changes have occurred in the Stemple Creek Watershed in northern California that have caused erosion to move soils from the upland to the flood plain, stream channels, and the bay. The purpose of this study is to document the recent (1954 to present) sediment deposition patterns in the flood plain area adjacent to Stemple Creek using the 137Cesium technique. Sediment deposition ranged from 0.26 to 1.84 cm year -1 for the period from 1964 to 2002 with an average of 0.85±0.41 cm year -1. Sediment deposition rates were higher for the 1954 to 1964 period with a range of 0.31-3.50 cm year -1 and an average of 1.29±1.04 cm year -1. These data indicate that sediment deposition in the flood plain has decreased since the middle 1950s, probably related to reduction in row crop agriculture and an increase in pasturelands. This study shows that the flood plains in the Stemple Creek Watershed are a significant sink for the soils being eroded from the upland area. Given the significance of the flood plain for trapping eroded materials before they reach the stream channels or the bay, efforts need to be made to manage these flood plain areas to insure that they do not change and become a source rather than a sink for eroded materials as improved management practices on the upland areas reduce sediment input to the flood plain.

Ritchie, Jerry C.; Finney, Vernon L.; Oster, Kenneth J.; Ritchie, Carole A.

2004-08-01

38

Exchanges of sediment between the flood plain and channel of the Amazon River in Brazil  

USGS Publications Warehouse

Sediment transport through the Brazilian sector of the Amazon River valley, a distance of 2010 km, involves exchanges between the channel and the flood plain that in each direction exceed the annual flux of sediment out of the river at O??bidos (???1200 Mt yr-1). The exchanges occur through bank erosion, bar deposition, settling from diffuse overbank flow, and sedimentation in flood-plain channels. We estimated the magnitude of these exchanges for each of 10 reaches of the valley, and combined them with calculations of sediment transport into and out of the reaches based on sediment sampling and flow records to define a sediment budget for each reach. Residuals in the sediment budget of a reach include errors of estimation and erosion or deposition within the channel. The annual supply of sediment entering the channel from bank erosion was estimated to average 1570 Mt yr-1 (1.3 ?? the O??bidos flux) and the amount transferred from channel transport to the bars (380 Mt yr-1) and the flood plain (460 Mt yr-1 in channelized flow; 1230 Mt yr-1 in diffuse overbank flow) totaled 2070 Mt yr-1 (1.7 ?? the O??bidos flux). Thus, deposition on the bars and flood plain exceeded bank erosion by 500 Mt yr-1 over a 10-16 yr period. Sampling and calculation of sediment loads in the channel indicate a net accumulation in the valley floor of approximately 200 Mt yr-1 over 16 yr, crudely validating the process-based calculations of the sediment budget, which in turn illuminate the physical controls on each exchange process. Another 300-400 Mt yr-1 are deposited in a delta plain downstream of O??bidos. The components of the sediment budget reflect hydrologie characteristics of the valley floor and geomorphic characteristics of the channel and flood plain, which in turn are influenced by tectonic features of the Amazon structural trough.

Dunne, T.; Mertes, L.A.K.; Meade, R.H.; Richey, J.E.; Forsberg, B.R.

1998-01-01

39

Use of mining-contaminated sediment tracers to investigate the timing and rates of historical flood plain sedimentation  

Microsoft Academic Search

Changes in land use practices following European settlement in the 1830s produced accelerated sedimentation on virtually all valley floors in the Blue River Watershed, Wisconsin. The contamination of sediments by Pb and Zn mining allowed us to calculate cross-valley rates of flood plain sedimentation for three time periods: the pre-mining period (1830–1900), the mining period (1900–1920), and the post-mining period

Scott A. Lecce; Robert T. Pavlowsky

2001-01-01

40

A census of abyssal polychaetes  

NASA Astrophysics Data System (ADS)

As part of the Census of Marine Life's programme of summarising existing knowledge of the oceans, records of all polychaete species collected below 2000 m have been collated from the literature. A total of 3633 records was assembled into a database, revealing that 768 species, 358 of which were new to science, have been reported from the deep sea over the past 200 years. The limitations of the dataset are also discussed. Most of the records were obtained from between 2000 m, the upper depth range of the study, and 4000 m. Analyses of the distribution of records with time reveals that the majority of records were added in the 1960s to early 1980s, coincidental with the introduction of new collecting technologies. However, following this period there was a gap between the collecting of samples and the publication of taxonomic results. To reduce this time lag we are encouraging the use of the world-wide web with new tools and protocols to bring together taxonomists working on different sample sets and allow them to share and compare taxonomic data. As this is the first collation of abyssal polychaetes, the records were analysed to determine whether there is a distinct hadal fauna and whether the fauna of individual trenches was distinctive or a subset of the abyssal plain fauna. The results suggest that the hadal fauna contains few endemic species and that the majority are elements of the abyssal fauna that have extended their bathymetric range.

Paterson, Gordon L. J.; Glover, Adrian G.; Barrio Froján, Christopher R. S.; Whitaker, Amoret; Budaeva, Nataliya; Chimonides, Jim; Doner, Stacy

2009-09-01

41

The Role of Lateral Fluid Flow in Off-Axis, Oceanic Hydrothermal Systems Under Abyssal Sedimentation Conditions  

NASA Astrophysics Data System (ADS)

Off-axis hydrothermal circulation is significant to the thermal and chemical evolution of the oceanic crust, to the chemical evolution of the oceans, and potentially to a deep biosphere within the upper crust. These off-axis hydrothermal systems are impacted by the type and distribution of sediment because sufficiently thick and contiguous sediment cover will limit the exchange of fluid between the ocean and the crust. It has been suggested that in off-axis settings lateral transport between sediment-poor regions, through the high permeability lavas, is the dominant geometry of fluid convection in igneous crust underlying thick sediment. To aid in understanding the role of sediment cover on seafloor hydrothermal systems, a numerical model of pelagic supply, post-depositional down-slope sediment redistribution (following [1]), and crustal hydrogeology has been developed. Synthetic seafloor bathymetry representative of crust formed at different spreading rates [2] is used as the initial bathymetry and seamounts are added randomly with a size and frequency distribution representative of the global ocean [3]. Other sedimentation variables are the diffusivity of sediment, the pelagic sediment supply rate and the sediment hydrological properties. From this, the model predicts the changing distribution of potential hydrothermal fluid recharge and discharge sites in response to sedimentation. These results are coupled with a two-dimensional model of fluid and heat transport to evaluate the conditions under which lateral fluid flow in the igneous oceanic crust are consistent with the global data set of seafloor heat flow measurements. Preliminary results suggest that, of the parameters investigated, the spatial density of model-predicted outcrops is most sensitive to the rate of pelagic sediment supply. In areas with lower than average seamount abundances crustal spreading rate is also important to the distribution of outcrops, with more outcrops predicted on crust formed at slow-spreading ridges. The model-predicted separation distance between potential fluid recharge and discharge sites is generally lower than previously estimated [4] implying that pressure gradients driving lateral fluid flow may be higher than predicted and upper crustal permeability may be lower than previously predicted. Results of this modeling will be presented, and the influences of the rate and nature of sedimentation on off-axis hydrothermal circulation will be discussed. [1] Webb and Jordan, JGR 2001, v106, p 30,433; [2] Goff and Jordan, JGR 1988, v93, p 13,589; [3] Hillier and Watts, Geophysical Research Letters 2007, v34, doi:10.1029/2007GL029874; [4] Fisher and Becker, Nature 2000, v403 p 71.

Anderson, B. W.; Coogan, L. A.; Gillis, K. M.

2010-12-01

42

Factors influencing the abundance and metabolic capacities of microorganisms in Eastern Coastal Plain sediments  

Microsoft Academic Search

The abundance and metabolic capacities of microorganisms residing in 49 sediment samples from 4 boreholes in Atlantic Coastal Plain sediments were examined. Radiolabeled time-course experiments assessing in situ mirobial capacities were initiated within 30 min of core recovery. Acetate (1-14C- and3H-) incorporation into lipids, microbial colony forming units, and nutrient limitations were examined in aliquots of subsurface sediments. Water-saturated sands

T. J. Phelps; S. M. Pfiffner; K. A. Sargent; D. C. White

1994-01-01

43

The role of outcrop-to-outcrop fluid flow in off-axis oceanic hydrothermal systems under abyssal sedimentation conditions  

NASA Astrophysics Data System (ADS)

It has been proposed that ridge flank hydrothermal circulation by outcrop-to-outcrop (lateral) flow may be the dominant mode of oceanic hydrothermal circulation globally. In this model, the upper igneous crust is an aquifer overlain by low permeability sediments, and aquifer-ocean fluid exchange occurs through basement outcrops. Thermally induced pressure gradients drive fluid laterally from recharge outcrops to discharge outcrops. To test the global applicability of outcrop-to-outcrop flow, models of synthetic basement bathymetry representative of crust formed at different spreading rates, pelagic sediment supply and post depositional transport, and sediment hydraulic impedance are used to quantify the time-varying distribution of sediment and basement outcrops globally. Results suggest that basement outcrops may be 40-50% closer together than previously estimated. The modeled sediment and outcrop results are coupled with a two-dimensional model of outcrop-to-outcrop fluid flow and heat exchange in a vertically isothermal crustal aquifer to predict the spatial distributions of seafloor heat flow within the simulation region under this mode of hydrothermal circulation. It is found that both the time-varying average and standard deviation of modeled seafloor heat flow required by outcrop-to-outcrop flow simultaneously fit the global heat flow data if the average aquifer permeability decreases from ˜10-9 m2 to ˜10-11 m2 over the duration of the global heat flow deficit (to ˜65 Myr). This permeability range is consistent with other estimates of upper crustal permeability on comparable spatial scales, and supports the proposition that outcrop-to-outcrop fluid flow may be the dominant mode of off-axis hydrothermal circulation globally.

Anderson, B. W.; Coogan, L. A.; Gillis, K. M.

2012-05-01

44

Monsoon sedimentation on the 'abandoned' tide-influenced Ganges-Brahmaputra delta plain  

NASA Astrophysics Data System (ADS)

Annual sediment delivery by the Ganges and Brahmaputra rivers to the Bengal margin has kept pace with sea level rise since the mid Holocene, sustaining subaerial growth of the delta. However, the Sundarbans region of the tidal delta is disconnected from major distributary sources of sediment and is often thought to be sediment starved, eroding, and susceptible to the meter of sea level rise predicted for the 21st century. Despite these assumptions, direct sedimentation measurements on the tidal delta plain reveal widespread mean annualized accretion rates of ˜1.1 cm yr-1, although heterogeneous depositional patterns indicate that topography and internal creek networks influence local sediment distribution. Short-lived radioisotope inventories (7Be: t1/2 = 53.3 days) measured on the freshly accumulated sediments indicate that about ½ of the mass deposited on the lower delta was sourced directly from the seasonal flood pulse of the river; the remaining ½ is derived from older (?1 yr) reworked sediments. Net sedimentation on this part of the delta traps ˜10% of annual Ganges-Brahmaputra sediment load, with accretion rates roughly equivalent to the mean regional rate of relative sea-level rise (RSLR) of ˜1.0 cm yr-1. If these sedimentation rates are representative of longer-term trends and subsidence rates remain stable over the next century, the lower delta plain may continue to maintain its elevation and stability despite documented mangrove retreat around its seaward edges.

Rogers, Kimberly G.; Goodbred, Steven L.; Mondal, Dhiman R.

2013-10-01

45

Sedimentation Dynamics in Sweet Hall Marsh, a Tidal Freshwater Marsh of Coastal Plain Virginia  

NASA Astrophysics Data System (ADS)

Sedimentation rates were measured from May 1998 to March 1999 at Sweet Hall Marsh, a tidal freshwater marsh in the Coastal Plain of Virginia using various techniques (sediment catch plates, triangular survey method, Be-7 distribution). Rates of sedimentation vary spatially and temporally in the marsh. Sedimentation rates are generally greatest adjacent to a tidal creek and decrease progressively farther into the marsh. Differences in rates of sedimentation are greatest spatially during the summer and are least during the winter. Accuracy of rates calculated depend on the methods used to measure sedimentation. A combination of methods likely provides the most accurate trends of sedimentation change. The organic content of marsh sediment may influence marsh stability indirectly and also varies spatially and temporally. Organic content generally increases farther away from sediment sources in the marsh; increased organic content in interior parts of Sweet Hall Marsh may promote increased rates of respiration and thus greater loss of total sediment fraction. Organic content seems to correlate with decreased carbon/nitrogen ratios and increased respiration rates. The general evolution of Sweet Hall Marsh was described using evidence obtained from vibracoring and carbon-14 dating. Along with stratigraphic evidence, organic content of marsh sediment was analyzed with depth to depict the history of the marsh.

Constantine, J. A.; Neubauer, S. C.; Anderson, I. C.; Johnson, G. H.

2001-05-01

46

Biogenic structures in modern slope to deep-sea sediments in the sulu sea basin (Philippines)  

Microsoft Academic Search

Wetzel, A., 1983. Biogenic structures in modern slope to deep~sea sediments in the Sulu Sea Basin (Philippines). Palaeogeogr., Palaeoclimatol., Palaeoecol., 42: 285--304. Slowly accumulated slope and rise sediments (5--20 cm\\/1000 yr) are totally biotur- bated as compared to only 10--30% in rapidly deposited abyssal plain sediments (100-- 200 cm\\/1000 yr). In contrast to a decrease in degree of bioturbation, biogenic

ANDREAS WETZEL

1983-01-01

47

Distributions, sources, and ecological risks of hexachlorocyclohexanes in the sediments from Haihe Plain, Northern China.  

PubMed

The levels of hexachlorocyclohexanes (HCHs) in the sediments from Haihe Plain, China, were measured by a gas chromatograph with a (63)Ni microelectron capture detector. The spatial distributions, possible sources, and potential ecological risks of these compounds were analyzed. The residual level of total HCHs was 33.84 ± 173.37 ng g(-1) dry weight (d.w.) with ranges of 0.13 ~ 1,107.41 ng g(-1) d.w. Much higher ?HCH contents were found in the lower reaches of some rivers and in the mouth of the main stream receiving tributaries. The predominance of ?-HCH (36%) in the sediments was similar to that in the soils from Haihe Plain. The high percentages of ?-HCH (23-41%) could be detected at 25% of the sampling sites in the seven river systems. There were statistically significant positive relationships between the contents of HCHs and total organic carbon. Lindane was identified as the primary source of HCHs in the sediments, and it seemed that recent illegal lindane inputs still existed in some areas in Haihe Plain, as indicated by the ?-/?-HCH and ?-/(? + ?)-HCH ratios. Severe potential ecological risks of ?-HCH to benthic organisms at some sampling sites were found based on the consensus-based sediment quality guidelines. PMID:23054791

Xu, Fu-Liu; Kong, Xiang-Zhen; He, Wei; Qin, Ning; Zhu, Ying; Tao, Shu

2013-04-01

48

Aliphatic and polycyclic aromatic hydrocarbons in Black Sea sediments  

Microsoft Academic Search

Concentrations of aliphatic hydrocarbons (AHC) in sediments of the Black Sea ranged from 153,000 ng g?1 dw near the mouth of the Danube River to about 10,000 ng g?1 dw in abyssal plain sediments. Compound distributions were dominated by long-chain n-alkanes except at the Danube station where a significant petrogenic component with an unresolved complex mixture was also present. Polycyclic

Stuart G. Wakeham

1996-01-01

49

Large-scale patterns in biodiversity of microbial eukaryotes from the abyssal sea floor  

PubMed Central

Eukaryotic microbial life at abyssal depths remains “uncharted territory” in eukaryotic microbiology. No phylogenetic surveys have focused on the largest benthic environment on this planet, the abyssal plains. Moreover, knowledge of the spatial patterns of deep-sea community structure is scanty, and what little is known originates primarily from morphology-based studies of foraminiferans. Here we report on the great phylogenetic diversity of microbial eukaryotic communities of all 3 abyssal plains of the southeastern Atlantic Ocean---the Angola, Cape, and Guinea Abyssal Plains---from depths of 5,000 m. A high percentage of retrieved clones had no close representatives in genetic databases. Many clones were affiliated with parasitic species. Furthermore, differences between the communities of the Cape Abyssal Plain and the other 2 abyssal plains point to environmental gradients apparently shaping community structure at the landscape level. On a regional scale, local species diversity showed much less variation. Our study provides insight into the community composition of microbial eukaryotes on larger scales from the wide abyssal sea floor realm and marks a direction for more detailed future studies aimed at improving our understanding of deep-sea microbes at the community and ecosystem levels, as well as the ecological principles at play. PMID:20007768

Scheckenbach, Frank; Hausmann, Klaus; Wylezich, Claudia; Weitere, Markus; Arndt, Hartmut

2009-01-01

50

A raised OIS 3 sea level recorded in coastal sediments, southern Changjiang delta plain, China  

NASA Astrophysics Data System (ADS)

The distribution of marine-influenced oxygen isotope stage (OIS) 5 to OIS 1 sediments was examined in several late Quaternary boreholes from the southern Changjiang (Yangtze) delta plain, China, using different dating methods including OSL, U-series, AMS 14C and paleomagnetism. Results demonstrate that coastal and estuarine deposition during OIS 5 and OIS 3 occurred throughout the study area. However, Holocene transgressive sediments were absent on the Taihu block. The burial depth of intertidal to subtidal sediment deposited during OIS 5e records 30-80 m subsidence caused by sediment compaction and tectonic movement since that time. However, coastal sediments formed during the late phase of OIS 3 were buried to a depth of ca. 6-15 m in the Taihu Lake area, while the burial depth increased eastward to ca. 45-60 m on the coastal plain. This phenomenon, combined with the distribution of Holocene marine strata, indicates at least 25-30 m uplift of the Taihu block since the end of OIS 3. We suggest that this uplift was mainly caused by the differential subsidence due to substantial amount of post-glacial deposition by the Changjiang and Huanghe Rivers on the continental shelf of east China marginal sea.

Wang, Zhanghua; Jones, Brian G.; Chen, Ting; Zhao, Baocheng; Zhan, Qing

2013-05-01

51

Crystallization of abyssal tholeiites  

Microsoft Academic Search

In some abyssal tholeiite magmas having a relatively high content of olivine component, olivine is the first mineral to crystallize. In others having a relatively high content of plagioclase component, plagioclase is the first mineral to crystallize. The rooks of these two groups are called OL- and PL-tholeiites respectively. Continued crystallization drives the residual liquids to the cotectic curve between

Fumiko Shido; Akiho Miyashiro; Maurice Ewing

1971-01-01

52

Occurrence of arsenic in sediment pore waters in the central Kanto Plain, Japan  

NASA Astrophysics Data System (ADS)

The Kanto Plain is known as the largest plain in Japan, where marine sediments are widely developed because of cyclic iteration of global sea-level changes even 50 km or more inland from the present shoreline. In this area, dependence on groundwater for water requirements is relatively high; in particular, around 40 % of the municipal water supply is dependent on groundwater. Arsenic levels greater than that permitted by the environmental standards of Japan have been detected in groundwater in this area. Therefore, to evaluate occurrences of arsenic and other related elements in pore waters contained in natural sediment layers, we measured the levels of various inorganic chemical substances such as arsenic (As), iron (Fe), and sulfur (S) and major dissolved ions such as sulfate (SO42-), calcium (Ca2+), and sodium (Na+). Pore waters were collected from sediment samples that were obtained by a drilling from the river bottom down to 44 m depth; pore water samples were obtained immediately after extraction of sediments. The sedimentary facies in the vertical profile are continental, transitional, and marine, including two aquifers. The upper aquifer (15-20 m) contains fine to medium sand, whereas the lower aquifer (37-44 m) contains medium to coarse and gravelly sand. Arsenic and other inorganic elements were measured by an inductively coupled plasma mass spectrometer (ICP/MS) and an inductively coupled plasma atomic emission spectrometer (ICP/AES), and major dissolved ions were measured by an ion chromatograph analyzer. The total content of chemical elements was measured by X-ray fluorescence analysis using solid sediment samples. We obtained the following results. The arsenic concentrations in pore waters in marine silt and clay sediments (approximately 0.04 mg/L) were about five times higher than that in continental sediments (approximately 0.008 mg/L). The highest concentration of arsenic (0.074 mg/L) was detected at a depth of 13 m, which is immediately above the upper aquifer. Visual observations confirmed that this level is under oxidizing conditions. Thus, it regards that arsenic was adsorbed to iron hydroxide in the sediments. On the other hand, in the top part of the section, from the river bottom to a depth of approximately 3 m, arsenic concentrations in the pore waters were clearly high and decreased gradually and continuously with depth. This is considered to be the result of anthropogenic impact on the river.

Hachinohe, Shoichi; Hamamoto, Hideki; Ishiyama, Takashi; Hossain, Sushmita; Oguchi, Chiaki T.

2014-05-01

53

Sedimentation along the Eastern Chenier Plain Coast: Down Drift Impact of a Delta Complex Shift  

NASA Technical Reports Server (NTRS)

The Mississippi River Chenier Plain is a shore parallel landform (down-drift from the Atchafalaya distributary of the Mississippi River) consisting of an alternating series of transgressive sand-shell ridges and regressive, progradational mudflats. The late 1940s shift of 1/3 of the flow of the Mississippi to the newly developing Atchafalaya delta complex to the west has resulted in injection of the river waters and suspended sediment into the westward flowing currents of the coastal current system. This has reactivated the dormant processes of mud accumulation along this coast. These environmental circumstances have provided the opportunity to: (1) investigate the depositional processes of the prograding, fine grained, mud flat facies of the open Chenier main coast and (2) to test the hypothesis that the impacts of the frequent cold front passages of fall, winter and spring exceed those of the occasional and more localized hurricane in shaping the coast and powering the dominant sedimentary processes. We conducted field investigations with the benefit of multi - scale, time series environmental surveillance by remote sensing systems, including airborne and satellite sensors. These systems provided invaluable new information on areal geomorphic patterns and the behavior of the coastal waters. This is a classic case of weather impacting inner shelf waters and sediments and causing the development of a new landform. It is clear that mud flats of the eastern chenier plain are prograding seaward, as well as progressively growing in a westerly direction.

Huh, Oscar K.; Walker, Nan D.; Moeller, Christopher

2001-01-01

54

Valley and interfluve sediments in the Southern Ganga plains, India: Exploring facies and magnetic signatures  

NASA Astrophysics Data System (ADS)

The western Ganga Plains of India show narrow, incised valleys that contain the major Himalayan-sourced rivers, separated by broad interfluves traversed by small plains-fed rivers. From analysis of four cores and outcrop sections to 50 m sub-surface, this geomorphic setting appears to be of Late Quaternary antiquity. A major river (paleo-Ganga) has been located near its present position since at least 26 ka BP, with indications of southward migration between 11 and 6 ka. Valley fill cores show repeated cycles of valley aggradation in response to Late Quaternary climatic oscillations, in accord with simulation models of drainage-basin response to climate change, and reflect interplay of discharge and sediment supply. Floodplain sediments within the valley fill show a generally weakly magnetic signature and only modest pedogenic activity. The valley margin records a major discontinuity that marks reduction of discharge in the Ganga River during the Last Glacial Maximum, when monsoonal precipitation was greatly reduced and lakes and eolian dunes occupied areas distant from the main channel. The lacustrine facies show marked magnetic enhancement, probably reflecting bacterial action and the availability of organic matter. The interfluve record yields no indication of major-river activity during the past 100 ka. Instead, the near-continuous activity of small plains-fed rivers generated cycles of alluviation and pedogenesis, the latter yielding strong magnetic signatures. Enhanced magnetic signatures are apparent in both valley and interfluve Holocene records, possibly linked to increased monsoonal strength, warmer conditions and enhanced rates of pedogenesis.

Sinha, R.; Bhattacharjee, P. S.; Sangode, S. J.; Gibling, M. R.; Tandon, S. K.; Jain, M.; Godfrey-Smith, D.

2007-10-01

55

The Surface of Venus is Saturated With Ancient Impact Structures, and its Plains are Marine Sediments  

NASA Astrophysics Data System (ADS)

Conventional interpretations of Venus are forced to fit dubious pre-Magellan conjectures that the planet is as active internally as Earth and preserves no ancient surface features. Plate tectonics obviously does not operate, so it is commonly assumed that the surface must record other endogenic processes, mostly unique to Venus. Imaginative systems of hundreds of tiny to huge rising and sinking plumes and diapirs are invoked. That much of the surface in fact is saturated with overlapping large circular depressions with the morphology of impact structures is obscured by postulating plume origins for selected structures and disregarding the rest. Typical structures are rimmed circular depressions, often multiring, with lobate debris aprons; central peaks are common. Marine-sedimentation features are overlooked because dogma deems the plains to be basalt flows despite their lack of source volcanoes and fissures. The unearthly close correlation between geoid and topography at long to moderate wavelengths requires, in conventional terms, dynamic maintenance of topography by up and down plumes of long-sustained precise shapes and buoyancy. A venusian upper mantle much stronger than that of Earth, because it is cooler or poorer in volatiles, is not considered. (The unearthly large so-called volcanoes and tessera plateaus often are related to rimmed circular depressions and likely are products of impact fluidization and melting.) Plains-saturating impact structures (mostly more obvious in altimetry than backscatter) with diameters of hundreds of km are superimposed as cookie-cutter bites, are variably smoothed and smeared by apparent submarine impact and erosion, and are differentially buried by sediments compacted into them. Marine- sedimentation evidence includes this compaction; long sinuous channels and distributaries with turbidite- channel characteristics and turbidite-like lobate flows (Jones and Pickering, JGSL 2003); radar-smooth surfaces and laminated aspect in lander images; and widespread minor structures with neither terrestrial volcanic analogues nor plausible volcanic explanations. Broad tracts of polygonal reticulations 100 m to 5 km in diameter have dimensional and geometric terrestrial analogues in the polygonal faulting shown by 3-D reflection-seismic surveys of dewatered fine-grained sediments in marine basins. Impact-comminuted basaltic crust may dominate the fine sediment. Vast numbers of small low so-called shield volcanoes have geometric analogues in terrestrial mud volcanoes, not magmatic constructs. Less than half of the 1000 small misnamed pristine craters, the only venusian craters accepted by all as of impact origin, in fact are pristine. The rest are variably eroded, their craters partly filled by sediments that often display polygonal faulting, and their aprons partly covered by sediments of surrounding plains. All gradations are displayed between these structures and the more modified but otherwise similar structures from which they are arbitrarily and inconsistently separated. Lunar analogy dates the thousands of large venusian craters, 300-2000 km in rim diameter, as older than 3.8 Ga. Marine sedimentation began before late-stage accretion was complete. The nominally pristine craters are commonly assumed to be younger than 1 Ga but may go back to 3.8 Ga. Venusian oceans persisted long after that, without stillstands sufficient for development of global shorelines and shelves, before complete greenhouse evaporation, deep desiccation, and top-down metamorphism of sediments.

Hamilton, W. B.

2009-05-01

56

Sulfur isotopic trends and pathways of iron sulfide formation in upper Holocene sediments of the anoxic Black Sea  

Microsoft Academic Search

Down-core trends for extents of iron sulfidation in upper Holocene microlaminated deposits of the Black Sea abyssal plain imply that most of the pyrite in these sediments is formed in the sulfidic water column and\\/or very close to the sediment-water interface. Sulfur isotopic data for pyrite within microlaminated muds from two localities in the deep basin show striking uniformity between

Timothy W. Lyons

1997-01-01

57

Geochemical Fractionations and Mobility of Arsenic, Lead and Cadmium in Sediments of the Kanto Plain, Japan.  

NASA Astrophysics Data System (ADS)

Lowland alluvial and floodplain sediment play a major role in transferring heavy metals and other elements to groundwater through sediment water interaction in changing environmental conditions. However identification of geochemical forms of toxic elements such as arsenic (As), lead (Pb) and cadmium (Cd) requires risk assessment of sediment and subsequent groundwater pollution. A four steps sequential extraction procedure was applied to characterize the geochemical fractionations of As, Pb and Cd for 44 sediment samples including one peat sample from middle basin area of the Nakagawa river in the central Kanto plain. The studied sediment profile extended from the bottom of the river to 44 m depth; sediment samples were collected at 1m intervals from a bored core. The existing sedimentary facies in vertical profile are continental, transitional and marine. There are two aquifers in vertical profile; the upper aquifer (15-20m) contains fine to medium sand whereas medium to coarse sand and gravelly sand contain in lower aquifer (37-44m). The total As and Pb contents were measured by the X-Ray Fluorescence analysis which ranged from 4 to 23 mg/kg of As and 10 to 27 mg/kg of Pb in sediment profile. The three trace elements and major heavy metals were determined by ICP/MS and ICP/AES, and major ions were measured by an ion chromatograph. The marine sediment is mainly Ca-SO4 type. The Geochemical analysis showed the order of mobility trends to be As > Pb > Cd for all the steps. The geochemical fractionations order was determined to be Fe-Mn oxide bound > carbonate bound > ion exchangeable > water soluble for As and Pb whereas the order for Cd is carbonate bound > Fe-Mn oxide bound > ion exchangeable > water soluble. The mobility tendency of Pb and Cd showed high in fine silty sediment of marine environment than for those from continental and transitional environments. In the case of As, the potential mobility is very high (>60%) in the riverbed sediments and clayey silt sediment at 13m depth which is just above the upper aquifer. This potential mobility may pose a threat to upper aquifer and riverbed aquatic system. The overall geochemical analysis revealed that the dissolution of Fe-Mn oxide is the most effective mechanism for As, Pb in groundwater however the mobility of Cd is mainly carbonate bound. In the present study, the pollution level is much below from leaching environmental standards (0.01 mg/L) for all three elements and the total content is within the natural abundance of As, Pb and Cd in sediment. The potential mobility of these elements in oxidized fine silty sediment and the possible further effect to the aquifer suggest that shallow groundwater abstraction should be restricted to protect seasonal groundwater fluctuation. Moreover marine sediment containing high total toxic element contents and mobility tendency at changing oxidation and reduction environments requires proper management when sediments are excavated for construction purpose.

Hossain, Sushmita; Oguchi, Chiaki T.; Hachinohe, Shoichi; Ishiyama, Takashi; Hamamoto, Hideki

2014-05-01

58

Source-To-Sink Perspectives On The Mississippi River System, Miocene To Present, Mountain To Abyss  

NASA Astrophysics Data System (ADS)

. The objective of this study is to present a synthesis of the Mississippi River source-to-sink system, from montane source to abyssal sink, to elucidate specific geomorphic components and boundaries in the system, controls on mass transfer, and resultant geomorphic and statigraphic development. The Mississippi River source-to-sink system constitutes one of the largest sources, conduits, and depocenters of sediment on Earth, extending from elevations of 3.7 km in the Rocky Mountains to the Gulf of Mexico abyssal plain. Despite being one of the most intensely studied fluvial-marine systems in the world, comprehensive understanding and management of the system's resources remain a challenge. The system is valuable in many ways: it provides navigation and water to the heart of North America, and sustains extensive marine fisheries. The river has built a delta that is home to millions of people and yet is subsiding rapidly. Ancestral Mississippi fluvial-marine deposits continue to yield high-value petroleum resources to exploration. To address the range of temporal and spatial scales over which the system has developed and continues to evolve, we will focus on three geological time spans that display contrasting geologic forcing and response: Miocene, Pleistocene, and late Holocene. The present configuration of source, conduit, and sink were established during the Miocene epoch, when tectonics (via the uplifting southern Rockies, and later the rejuvenated Appalachians) and climate (wet in the east and dry in the west) provided abundant water and sediment to prograde the shelf margin and initiate deep-sea fan growth. Pleistocene continental glaciation, eustasy, and catastrophic drainage events further sculpted the alluvial valley, and extended the shelf margin, and fan. Studies of Modern processes and Holocene delta development have provided keys to both the delta's past and future evolution, in terms of cyclic autogenic lobe-switching, mass-transport events, storm-driven sediment delivery to canyon heads, and allogenic/anthropogenic controls on sediment supply and subsidence.

Bentley, S. J.; Blum, M. D.

2013-12-01

59

Organochlorine Pesticide Concentrations in Sediment and Amphibian Tissue in Playa Wetlands in the Southern High Plains, USA  

Microsoft Academic Search

Playa wetlands are critical habitat for wildlife in the Southern High Plains (SHP), a region dominated by agriculture. Little\\u000a information on pesticide levels exists for playas, and thus we measured organochlorine pesticide concentrations in sediment\\u000a and amphibians collected from playas in cropland and grassland watersheds. Heptachlor, ?- and ?-BHC, ?-chlordane, and dieldrin\\u000a were detected in sediment and\\/or tissue samples, typically

Louise S. Venne; Todd A. Anderson; Baohong Zhang; Loren M. Smith; Scott T. McMurry

2008-01-01

60

Thematic Mapper analysis to identify geomorphologic and sediment texture of El Tineh plain, north-western coast of Sinai, Egypt  

Microsoft Academic Search

Thematic Mapper data combined with field inspection are successfully applied to detect a wide variety of texture analysis of sediments and geomorphologic variability along the coastal plain of El Tineh bay at the north-western part of Sinai. Processing techniques used in this study include: image enhancement, principal component analysis (PCA), TM band ratios and supervised classification. The analysis of colour

K. H. M. DEWIDAR; O. E. Frihy

2003-01-01

61

Assessing the accuracy of thermoluminescence for dating baked sediments beneath late Quaternary lava flows, Snake River Plain, Idaho  

Microsoft Academic Search

Baked sediments beneath lava flows on the Snake River Plain, Idaho, with independent age control by either C-14 or K\\/Ar dating were analyzed to evaluate the accuracy of the thermoluminescence (TL) technique. The age of flows ranges from approx. 2 to 100 ka and multiple TL analyses by the total bleach method yielded ages that overlap at one sigma with

Steven L. Forman; James Pierson; R. P. Smith; W. R. Hackett; G. Valentine

1994-01-01

62

Thermal, chemical, and mass-transport processes induced in abyssal sediments by the emplacement of nuclear waste: experimental and modeling results  

SciTech Connect

This paper discusses heat and mass transport studies of marine red clay sediments being considered as a nuclear waste isolation medium. Numerical models indicate that for a maximum allowable sediment/canister interface temperature of 200 to 250/sup 0/C, the sediment can absorb about 1.5 kW initial power from waste in a 3 m long by 0.3 m dia canister buried 30 m in the sediment. Fluid displacement due to convection is found to be less than 1 m. Laboratory studies of the geochemical effects induced by heating sediment/seawater mixtures indicate that the canister and waste form must be designed to resist a hot, acid (pH 3 to 4) oxidizing environment. Since the thermally altered sediment volume of about 5.5 m/sup 3/ is small relative to the sediment volume overlying the canister, the acid and oxidizing conditions are not anticipated to effect the properties of the far field. Using sorption coefficient correlations, the migration of four nuclides /sup 239/Pu, /sup 137/Cs, /sup 129/I, and /sup 99/Tc were computer for a canister buried 30 m deep in a 60 m thick red clay sediment layer. It was found that the /sup 239/Pu and /sup 137/Cs are essentially completely contained in the sediments, while /sup 129/I and /sup 99/Tc broke through the 30 m of sediment in about 5000 years. The resultant peak injection rates of 4.6 x 10/sup -5/ ..mu..Ci/year-m/sup 2/ for /sup 129/I and 1.6 x 10/sup -2/ ..mu..Ci/year-m/sup 2/ for /sup 99/Tc were less than the natural radioactive flux of /sup 226/Ra (3.5 to 8.8 x 10/sup -4/ ..mu..Ci/year-m/sup 2/) and /sup 222/Rn (0.26 to 0.88 ..mu..Ci/year-m/sup 2/).

McVey, D.F.; Erickson, K.L.; Seyfried, W.

1980-01-01

63

Trends in nutrient and sediment retention in Great Plains reservoirs (USA).  

PubMed

Reservoirs are artificial ecosystems with physical, chemical, and biological transitional characteristics between rivers and lakes. Greater water retention time in reservoirs provides conditions for cycling materials inputs from upstream waters through sedimentation, biological assimilation and other biogeochemical processes. We investigated the effects of reservoirs on the water quantity and quality in the Great Plains (Kansas, USA), an area where little is known about these dominant hydrologic features. We analyzed a 30-year time-series of discharge, total phosphorus (TP), nitrate (NO3(-)), and total suspended solids (TSS) from six reservoirs and estimated overall removal efficiencies from upstream to downstream, testing correlations among retention, discharge, and time. In general, mean removal of TP (42-74%), TSS (0-93%), and NO3(-) (11-56%) from upstream to downstream did not change over 30 years. TP retention was associated with TSS removal, suggesting that nutrient substantial portion of P was adsorbed to solids. Our results indicated that reservoirs had the effect of lowering variance in the water quality parameters and that these reservoirs are not getting more or less nutrient-rich over time. We found no evidence of temporal changes in the yearly mean upstream and downstream discharges. The ratio upstream/downstream discharge was analyzed because it allowed us to assess how much contribution of additional unsampled tributaries may have biased our ability to calculate retention. Nutrient and sediment removal was less affected by hydraulic residence time than expected. Our study demonstrates that reservoirs can play a role in the removal and processing of nutrient and sediments, which has repercussions when valuing their ecological services and designing watershed management plans. PMID:24061791

Cunha, Davi Gasparini Fernandes; do Carmo Calijuri, Maria; Dodds, Walter Kennedy

2014-02-01

64

Geostatistical modeling of the spatial distribution of sediment oxygen demand within a Coastal Plain blackwater watershed  

PubMed Central

Blackwater streams are found throughout the Coastal Plain of the southeastern United States and are characterized by a series of instream floodplain swamps that play a critical role in determining the water quality of these systems. Within the state of Georgia, many of these streams are listed in violation of the state’s dissolved oxygen (DO) standard. Previous work has shown that sediment oxygen demand (SOD) is elevated in instream floodplain swamps and due to these areas of intense oxygen demand, these locations play a major role in determining the oxygen balance of the watershed as a whole. This work also showed SOD rates to be positively correlated with the concentration of total organic carbon. This study builds on previous work by using geostatistics and Sequential Gaussian Simulation to investigate the patchiness and distribution of total organic carbon (TOC) at the reach scale. This was achieved by interpolating TOC observations and simulated SOD rates based on a linear regression. Additionally, this study identifies areas within the stream system prone to high SOD at representative 3rd and 5th order locations. Results show that SOD was spatially correlated with the differences in distribution of TOC at both locations and that these differences in distribution are likely a result of the differing hydrologic regime and watershed position. Mapping of floodplain soils at the watershed scale shows that areas of organic sediment are widespread and become more prevalent in higher order streams. DO dynamics within blackwater systems are a complicated mix of natural and anthropogenic influences, but this paper illustrates the importance of instream swamps in enhancing SOD at the watershed scale. Moreover, our study illustrates the influence of instream swamps on oxygen demand while providing support that many of these systems are naturally low in DO. PMID:20938491

Todd, M. Jason; Lowrance, R. Richard; Goovaerts, Pierre; Vellidis, George; Pringle, Catherine M.

2010-01-01

65

Assessing the accuracy of thermoluminescence for dating baked sediments beneath late Quaternary lava flows, Snake River Plain, Idaho  

Microsoft Academic Search

Baked sediments beneath lava flows on the Snake River Plain, Idaho, with independent age control by either ¹⁴C or K\\/Ar dating were analyzed to evaluate the accuracy of the thermoluminescence (TL) technique. The age of flows ranges from â¼2 to 100 ka and multiple TL analyses by the total bleach method yielded ages that overlap at one sigma with independent

Steven L. Forman; James Pierson; G. Valentine; W. R. Hackett

1994-01-01

66

Pathways for arsenic from sediments to groundwater to streams: biogeochemical processes in the Inner Coastal Plain, New Jersey, USA.  

PubMed

The Cretaceous and Tertiary sediments that underlie the Inner Coastal Plain of New Jersey contain the arsenic-rich mineral glauconite. Streambed sediments in two Inner Coastal Plain streams (Crosswicks and Raccoon Creeks) that traverse these glauconitic deposits are enriched in arsenic (15-25mg/kg), and groundwater discharging to the streams contains elevated levels of arsenic (>80?g/L at a site on Crosswicks Creek) with arsenite generally the dominant species. Low dissolved oxygen, low or undetectable levels of nitrate and sulfate, detectable sulfide concentrations, and high concentrations of iron and dissolved organic carbon (DOC) in the groundwater indicate that reducing environments are present beneath the streambeds and that microbial activity, fueled by the DOC, is involved in releasing arsenic and iron from the geologic materials. In groundwater with the highest arsenic concentrations at Crosswicks Creek, arsenic respiratory reductase gene (arrA) indicated the presence of arsenic-reducing microbes. From extracted DNA, 16s rRNA gene sequences indicate the microbial community may include arsenic-reducing bacteria that have not yet been described. Once in the stream, iron is oxidized and precipitates as hydroxide coatings on the sediments. Arsenite also is oxidized and co-precipitates with or is sorbed to the iron hydroxides. Consequently, dissolved arsenic concentrations are lower in streamwater than in the groundwater, but the arsenic contributed by groundwater becomes part of the arsenic load in the stream when sediments are suspended during high flow. A strong positive relation between concentrations of arsenic and DOC in the groundwater samples indicates that any process-natural or anthropogenic-that increases the organic carbon concentration in the groundwater could stimulate microbial activity and thus increase the amount of arsenic that is released from the geologic materials. PMID:20580401

Barringer, Julia L; Mumford, Adam; Young, Lily Y; Reilly, Pamela A; Bonin, Jennifer L; Rosman, Robert

2010-11-01

67

Pathways for arsenic from sediments to groundwater to streams: Biogeochemical processes in the Inner Coastal Plain, New Jersey, USA  

USGS Publications Warehouse

The Cretaceous and Tertiary sediments that underlie the Inner Coastal Plain of New Jersey contain the arsenic-rich mineral glauconite. Streambed sediments in two Inner Coastal Plain streams (Crosswicks and Raccoon Creeks) that traverse these glauconitic deposits are enriched in arsenic (15–25 mg/kg), and groundwater discharging to the streams contains elevated levels of arsenic (>80 ?g/L at a site on Crosswicks Creek) with arsenite generally the dominant species. Low dissolved oxygen, low or undetectable levels of nitrate and sulfate, detectable sulfide concentrations, and high concentrations of iron and dissolved organic carbon (DOC) in the groundwater indicate that reducing environments are present beneath the streambeds and that microbial activity, fueled by the DOC, is involved in releasing arsenic and iron from the geologic materials. In groundwater with the highest arsenic concentrations at Crosswicks Creek, arsenic respiratory reductase gene (arrA) indicated the presence of arsenic-reducing microbes. From extracted DNA, 16s rRNA gene sequences indicate the microbial community may include arsenic-reducing bacteria that have not yet been described. Once in the stream, iron is oxidized and precipitates as hydroxide coatings on the sediments. Arsenite also is oxidized and co-precipitates with or is sorbed to the iron hydroxides. Consequently, dissolved arsenic concentrations are lower in streamwater than in the groundwater, but the arsenic contributed by groundwater becomes part of the arsenic load in the stream when sediments are suspended during high flow. A strong positive relation between concentrations of arsenic and DOC in the groundwater samples indicates that any process—natural or anthropogenic—that increases the organic carbon concentration in the groundwater could stimulate microbial activity and thus increase the amount of arsenic that is released from the geologic materials.

Barringer, Julia L.; Mumford, Adam; Young, Lily Y.; Reilly, Pamela A.; Bonin, Jennifer L.; Rosman, Robert

2010-01-01

68

Sediment-Basalt Architecture, Pliocene and Pleistocene Eastern and Central Snake River Plain  

Microsoft Academic Search

This presentation is a synthesis of known stratigraphic studies of the Pliocene, Pleistocene and Holocene basalts and interbedded sedimentary beds on the Eastern Snake River Plain (ESRP). This information is important for understanding the post-caldera tectonic evolution of the ESRP, especially for tracking patterns of volcanic eruption and changes in topography. Geophysical surveys and existing well logs indicate the depth

C. M. Helm-Clark; P. K. Link

2006-01-01

69

Productivity of ephemeral headwater riparian forests impacted by sedimentation in the southeastern United States coastal plain.  

PubMed

Riparian forests serve an essential function in improving water quality through the filtering of sediments and nutrients from surface runoff. However, little is known about the impact of sediment deposition on productivity of riparian forests. Sediment inputs may act as a subsidy to forest productivity by providing additional nutrients for plant uptake or may act as a stress by creating anoxic soil conditions. This study determined how sediment deposition affected riparian forests along ephemeral headwater streams at Ft. Benning, Georgia, USA. Above- and belowground productivity, leaf-area index (LAI), and standing crop biomass for fine roots, shrubs, and trees were compared along a gradient of present sedimentation rates in 17 riparian forests. Annual litterfall production was determined from monthly collections using 0.25- m(2) traps; woody biomass was determined from annual diameter at breast height (DBH) measurements using species-specific allometric equations; fine root productivity was determined using sequential coring; LAI was measured by expanding specific leaf area by annual litterfall production; and shrub biomass was determined using species-specific biomass equations based on height and root collar diameter. Significant declines in litterfall, woody biomass production, fine root production, LAI, and shrub biomass were found with as little as 0.1 to 0.4 cm yr(-2) sedimentation. We conclude that the levels of sedimentation in this study do not subsidize growth in ephemeral headwater riparian forests but instead create a stress similar to that found under flooded conditions. PMID:19329685

Jolley, Rachel L; Lockaby, B Graeme; Cavalcanti, Guadalupe G

2009-01-01

70

Organic carbon cycling in abyssal benthic food chains: numerical simulations of bioenhancement by sewage sludge  

NASA Astrophysics Data System (ADS)

The hypothetical bioenhancement of the endemic benthic biota on an oligotrophic abyssal plain by organic carbon has been investigated with mathematical simulation experiments. First, the responses of the biomass and respiration to seasonal variations in the rain of organic carbon (POC) have been simulated in a simplified benthic assemblage (sediment organic carbon, sediment-dwelling heterotrophs (bacteria, meiofauna, macrofauna and detritus feeding megafauna) and predatory megafauna), with no added organic matter. These calculations were based on measured standing stocks and respiration in the central North Pacific (5.8 km depth, 31°N Lat.×159°W Long.). The dynamic relationships in this natural "oligotrophic" food chain were then subjected to added inputs of organic carbon presumed to be in sewage sludge. Two examples are presented: a modest but continuous input of organic carbon (100 mg C m -2 d -1) and a year-long pulse of the same intensity. The continuous input forced the biomass and community respiration to steadily increase until they reached steady state in 15 years at values similar to those found on a typical continental shelf. The pulse exhibited the same pattern, but biomass and respiration returned to levels found under natural oligotrophic conditions several years after cessation of intensified carbon loading. The responses of the sediment community to added organic matter were validated using information from a deep-ocean sewage disposal site (DWD106) off the coast of New Jersey. The models are also used to illustrate an approach for estimating possible transfers of potentially toxic contaminants, such as total polycyclic aromatic hydrocarbons (tPAHs), in lipid-rich eggs. In the future it will be necessary to validate model results with deep-ocean in situ experiments.

Rowe, Gilbert T.

1998-05-01

71

Arsenic in sediments, groundwater, and streamwater of a glauconitic Coastal Plain terrain, New Jersey, USA-Chemical " fingerprints" for geogenic and anthropogenic sources  

USGS Publications Warehouse

Glauconite-bearing deposits are found worldwide, but As levels have been determined for relatively few. The As content of glauconites in sediments of the Inner Coastal Plain of New Jersey can exceed 100mg/kg, and total As concentrations (up to 5.95??g/L) found historically and recently in streamwaters exceed the State standard. In a major watershed of the Inner Coastal Plain, chemical " fingerprints" were developed for streambed sediments and groundwater to identify contributions of As to the watershed from geologic and anthropogenic sources. The fingerprint for streambed sediments, which included Be, Cr, Fe and V, indicated that As was predominantly of geologic origin. High concentrations of dissolved organic C, nutrients (and Cl-) in shallow groundwater indicated anthropogenic inputs that provided an environment where microbial activity released As from minerals to groundwater discharging to the stream. Particulates in streamwater during high flow constituted most of the As load; the chemical patterns for these particulates resembled the geologic fingerprint of the streambed sediments. The As/Cr ratio of these suspended particles likely indicates they derived not only from runoff, but from groundwater inputs, because As contributed by groundwater is sequestered on streambed sediments. Agricultural inputs of As were not clearly identified, although chemical characteristics of some sediments indicated vehicle-related inputs of metals. Sediment sampling during dry and wet years showed that, under differing hydrologic conditions, local anthropogenic fingerprints could be obscured but the geologic fingerprint, indicating glauconitic sediments as an As source, was robust. ?? 2011.

Barringer, J.L.; Reilly, P.A.; Eberl, D.D.; Blum, A.E.; Bonin, J.L.; Rosman, R.; Hirst, B.; Alebus, M.; Cenno, K.; Gorska, M.

2011-01-01

72

Evaluation of natural radioactivity in soil, sediment and water samples of Niger Delta (Biseni) flood plain lakes, Nigeria.  

PubMed

This paper presents the findings of a baseline study undertaken to evaluate the natural radioactivity levels in soil, sediment and water samples in four flood plain lakes of the Niger Delta using a hyper pure germanium (HPGe) detector. The activity profile of radionuclides shows low activity across the study area. The mean activity level of the natural radionuclides (226)Ra, (232)Th and (40)K is 20 ± 3, 20 ± 3 and 180 ± 50 Bq kg(-1), respectively. These values are well within values reported elsewhere in the country and in other countries with similar environments. The study also examined some radiation hazard indices. The mean values obtained are, 76 ± 14 Bq kg(-1), 30 ± 5.5 ?Gy h(-1), 37 ± 6.8 ?Sv y(-1), 0.17 and 0.23 for Radium Equivalent Activity (Ra(eq)), Absorbed Dose Rates (D), Annual Effective Dose Rates (E(ff) Dose), External Hazard Index (H(ex)) and Internal Hazard Index (H(in)) respectively. All the health hazard indices are well below their recommended limits. The soil and sediments from the study area provide no excessive exposures for inhabitants and can be used as construction materials without posing any significant radiological threat to the population. The water is radiologically safe for domestic and industrial use. The paper recommends further studies to estimate internal and external doses from other suspected radiological sources to the population of the Biseni kingdom. PMID:21514983

Agbalagba, E O; Onoja, R A

2011-07-01

73

Iodine diagenesis in pelagic deep-sea sediments  

NASA Astrophysics Data System (ADS)

Nineteen sediment cores from the Madeira, Seine, Tagus and Nares Abyssal Plains and the Alboran Sea have been used to evaluate the speciation, fluxes and diagenesis of iodine in the deep sea. The sediments have surficial molar I/C ratios of 10-30 × 10 -4 in excess of previous reported values for planktonic material (~1 × 10 -4). Solid phase I contents decrease exponentially with depth corresponding to decomposition rate constants of 5-260 × 10 -6 yr -1 which vary with the carbon accumulation rate. Iodine species in the pore waters follow a vertical sequence of four zones: 1. a zone of I - production where total dissolved iodine (?I) concentrations initially increase at the seawater-sediment interface; 2. a zone of I - oxidation where interconversion of I - to IO -3 occurs; 3. a zone of IO -3 reduction where interconversion of IO -3 back to I - occurs which corresponds to the suboxic part of the sediment column; and 4. a further zone of I - production which is confined to the lower anoxic part of the sediment column. Benthic ?I fluxes in the Madeira Abyssal Plain measured from shipboard incubation experiments and calculated from porewater gradients are similar, averaging 0.55 and 0.36 × 10 -8 ?mol cm -2 sec -, respectively. In the surface sediment the observed I enrichment results from a quasi-closed cycle for iodine initially involving release of I - from decomposing marine organic matter followed by rapid removal onto organic matter at the sediment-seawater interface where I/C regeneration ratios of up to 200 × 10 -4 are found, lodate reduction occurs during suboxic diagenesis, after denitrification and before MnO 2 reduction, consistent with the sequence of reactions predicted from the free energy yields for organic matter oxidation. There is some further I - production in the anoxic section of sediments but at much smaller rates than occur during the interfacial diagenetic cycling.

Kennedy, H. A.; Elderfield, H.

1987-09-01

74

Saprolite formation beneath Coastal Plain sediments near Washington, D.C.  

USGS Publications Warehouse

Three lines of evidence indicate that this buried weathering profile (saprolite) has formed in the subsurface and is post-Miocene in age. The post-Miocene age for the subsurface saprolite profile shows that not all saprolite beneath Cretaceous sediment is pre-Cretaceous in age. These observations have important implications for the interpretation of age of the exposed Piedmont saprolite. -from Authors

Pavich, M.J.; Obermeier, S.F.

1985-01-01

75

Nile delta: extreme case of sediment entrapment on a delta plain and consequent coastal land loss  

Microsoft Academic Search

Accelerated erosion of Egypt's Nile delta coast during this century has generally been attributed to construction of two dams at Aswan, entrapment of sediment in Lake Nasser behind the High Dam, and effects of barrages and river control structures on River Nile deposition below Aswan. Also considered important are natural factors, including delta subsidence, rising sea level and strong coastal

Daniel Jean Stanley

1996-01-01

76

Effects of agricultural tillage and sediment accumulation on emergent plant communities in playa wetlands of the U.S. High Plains.  

PubMed

Identifying community assembly filters is a primary ecological aim. The High Plains, a 30 million ha short-grass eco-region, is intensely cultivated. Cultivation disturbance, including plowing and eroded soil deposition down-slope of plowing, influences plant composition in depressional wetlands, such as playas, within croplands. We evaluated influences of wetland cultivation and sediment deposition on plant composition in playas embedded within croplands (46 plowed and 32 unplowed) and native grasslands (79) across 6 High Plains' states. Sediment accumulation ranged from 7 to 78 cm in cropland and 1 to 35 cm in grassland playas. Deeper sediments and plowing each decreased wetland plant richness, 28% and 70% respectively in cropland wetlands. Sediment depth reduced richness 37% in small grasslands playas while it increased richness 22% in larger ones, suggesting moderate disturbance increased richness when there were nearby propagule sources. Sediment depth was unrelated to species richness in plowed wetlands, probably because plowing was a strong disturbance. Plowing removed perennial plants from vegetation communities. Sediment accumulation also influenced species composition in cropland playas, e.g., probability of Eleocharis atropurpurea increased with sediment depth, while probability of Panicum capillare decreased. In grassland playas, observed lighter sediment depths did not influence species composition after accounting for wetland area. Sediment accumulation and plowing shift wetland plant communities toward annual species and decrease habitat connectivity for wetland-dependent organisms in cropland playas over 39,000 and 23,400 ha respectively. Conservation practices lessening sediment accumulation include short-grass buffer strips surrounding wetlands. Further, wetland tillage, allowed under federal agricultural conservation programs, should be eliminated. PMID:23500104

O'Connell, Jessica L; Johnson, Lacrecia A; Daniel, Dale W; McMurry, Scott T; Smith, Loren M; Haukos, David A

2013-05-15

77

Geochemistry of core sediments from the Middle Tagus alluvial plain (Portugal) since the last glacial: using background determination methods to outline environmental changes  

Microsoft Academic Search

This work deals with the geochemistry of the sediments from the Santarém-Entre Valas (SEV) borehole, in the middle Tagus alluvial\\u000a plain in Portugal. Methods for background determination were used, notably the concentration–length and cumulative frequency\\u000a methods. Both methods were in excellent agreement for the elements of interest, namely Au, As, Fe, U, Cu, Pb, Zn, Co, and\\u000a Cr. With these

T. M. Azevêdo; M. A. Gonçalves

2009-01-01

78

Comparison and correlation of physical properties from the plain and slope sediments in the Ulleung Basin, East Sea (Sea of Japan)  

Microsoft Academic Search

High-resolution profiles (chirp sonar, 2–7kHz) acquired from the Ulleung Basin, East Sea (Sea of Japan) revealed several discrete echo types, suggesting deposits formed mainly by mass flow processes. The Ulleung Basin plain sediments are characterized by turbidite\\/hemipelagic deposits, while slide, slump, and debrite deposits are mainly found in the slope area. Rock fall deposits also appear near the Ulleung Island.

G. Y Kim; D. C Kim

2001-01-01

79

Black carbon's long trip to the abyssal plain  

NASA Astrophysics Data System (ADS)

Black carbon, or soot, is the second most important anthropogenic driver of global climate change, taking a backseat only to carbon dioxide. Whether from wood in a cookstove, coal in a power plant, or trees charred by a wildfire, black carbon is produced by the incomplete combustion of organic matter. Once it gets into the environment, black carbon lowers the albedo when it settles on land, increasing warming and enhancing snow and ice melt. In the atmosphere, black carbon both helps and inhibits the formation of clouds.

Schultz, Colin

2014-08-01

80

Algal pigments in Southern Ocean abyssal foraminiferans indicate pelagobenthic coupling  

NASA Astrophysics Data System (ADS)

The cytoplasm of four species of abyssal benthic foraminiferans from the Southern Ocean (around 51°S; 12°W and 50°S; 39°W) was analysed by High Performance Liquid Chromatography (HPLC) and found to contain large concentrations of algal pigments and their degradation products. The composition of the algal pigments in the foraminiferan cytoplasm reflected the plankton community at the surface. Some foraminiferans contained high ratios of chlorophyll a/degraded pigments because they were feeding on fresher phytodetritus. Other foraminiferans contained only degraded pigments which shows that they utilized degraded phytodetritus. The concentration of algal pigment and corresponding degradation products in the foraminiferan cytoplasm is much higher than in the surrounding sediment. It shows that the foraminiferans collect a diluted and sparse food resource and concentrate it as they build up their cytoplasm. This ability contributes to the understanding of the great quantitative success of foraminiferans in the deep sea. Benthic foraminiferans are a food source for many abyssal metazoans. They form a link between the degraded food resources, phytodetritus, back to the active metazoan food chains.

Cedhagen, Tomas; Cheah, Wee; Bracher, Astrid; Lejzerowicz, Franck

2014-10-01

81

Chemistry of bottom sediments from the Cal-Sag channel and the Des Plaines and Illinois Rivers between Joliet and Havana, Illinois  

SciTech Connect

Cores were taken in 28 actual or proposed maintenance-dredging areas. Sixty-one core samples were analyzed to provide a data base for subsequent studies of the suitability of the potential dredged material for reclamation of abandoned surface-mined land bordering the Illinois Waterway. Samples were composited over 2-ft depth increments, up to a maximum 8-ft depth where possible. Parameters determined for each sample were: volatile solids, flash point, polyaromatic hydrocarbons (PAHs), base/neutral organic compounds, pH, total phosphorus, total phenols, oil and grease, polychlorinated biphenyls (PCBs), cyanide, arsenic, barium, cadmium, chromium, copper, lead, mercury, zinc, silver, nickel, selenium, and sulfide. Results showed PCBs to be higher in the Cal-Sag Channel sediments (..mu..=7.0 mg/kg) than in the Des Plaines River (..mu..=1.6 mg/kg), or Illinois River (..mu..=0.5 mg/kg) sediments. Concentrations of metals including arsenic, barium, cadmium, copper, lead, nickel, and silver were higher in the Des Plaines River samples than in the Cal-Sag Channel or Illinois River samples. Illinois River sediments were, generally, the least contaminated in terms of the measured parameters. Leach tests for arsenic, chromium, copper, lead, nickel, and zinc indicated low leachate-metal concentrations relative to total metal concentrations; thus, these metals exist in relatively insoluble solid states in the sediments.

Harrison, W.; Kucera, E.T.; Tome, C.; Van Loon, L.S.; Van Luik, A.

1981-02-01

82

Census of Marine Life: Census of the Diversity of Abyssal Marine Life  

NSDL National Science Digital Library

A field project of the multi-national Census of Marine Life, the Census of the Diversity of Abyssal Marine Life (CeDAMar) was created to document "actual species diversity of abyssal plains as a basis for global change research and for a better understanding of historical causes and actual ecological factors regulating biodiversity." This site provides Deep-Sea researchers with a forum for discussion and information-sharing. Specifically, this forum allows "researchers to exchange experiences and results from the Projects united under the umbrella of CeDAMar." Additionally, this site links to relevant Projects, Articles, News, FAQ, and Web links, and provides a search engine for locating specific information about CeDAMar.

83

Arsenic in New Jersey Coastal Plain streams, sediments, and shallow groundwater: effects from different geologic sources and anthropogenic inputs on biogeochemical and physical mobilization processes  

USGS Publications Warehouse

Arsenic (As) concentrations in New Jersey Coastal Plain streams generally exceed the State Surface Water Quality Standard (0.017 micrograms per liter (µg/L)), but concentrations seldom exceed 1 µg/L in filtered stream-water samples, regardless of geologic contributions or anthropogenic inputs. Nevertheless, As concentrations in unfiltered stream water indicate substantial variation because of particle inputs from soils and sediments with differing As contents, and because of discharges from groundwater of widely varying chemistry. In the Inner Coastal Plain, streams draining to lower reaches of the Delaware River traverse As-rich glauconitic sediments of marine origin in which As contents typically are about 20 milligrams per kilogram (mg/kg) or greater. In some of these sedimentary units, As concentrations exceed the New Jersey drinking-water maximum contaminant level (5 µg/L) in shallow groundwater that discharges to streams. Microbes, fueled by organic carbon beneath the streambed, reduce iron (Fe) and As, releasing As and Fe into solution in the shallow groundwater from geologic materials that likely include (in addition to glauconite) other phyllosilicates, apatite, and siderite. When the groundwater discharges to the stream, the dissolved Fe and As are oxidized, the Fe precipitates as a hydroxide, and the As sorbs or co-precipitates with the Fe. Because of the oxidation/precipitation process, dissolved As concentrations measured in filtered stream waters of the Inner Coastal Plain are about 1 µg/L, but the total As concentrations (and loads) are greater, substantially amplified by As-bearing suspended sediment in stormflows. In the Outer Coastal Plain, streams draining to the Atlantic Ocean traverse quartz-rich sediments of mainly deltaic origin where the As content generally is low ( With a history of agriculture in the New Jersey Coastal Plain, anthropogenic inputs of As, such as residues from former pesticide applications in soils, can amplify any geogenic As in runoff. Such inputs contribute to an increased total As load to a stream at high stages of flow. As a result of yet another anthropogenic influence, microbes that reduce and mobilize As beneath the streambeds are stimulated by inputs of dissolved organic carbon (DOC). Although DOC is naturally occurring, anthropogenic contributions from wastewater inputs may deliver increased levels of DOC to subsurface soils and ultimately groundwater. Arsenic concentrations may increase with the increases in pH of groundwater and stream water in developed areas receiving wastewater inputs, as As mobilization caused by pH-controlled sorption and desorption reactions are likely to occur in waters of neutral or alkaline pH (for example, Nimick and others, 1998; Barringer and others, 2007b). Because of the difference in As content of the geologic materials in the two sub-provinces of the Coastal Plain, the amount of As that is mobile in groundwater and stream water is, potentially, substantially greater in the Inner Coastal Plain than in the Outer Coastal Plain. In turn, streams within the Inner and Outer Coastal Plain can receive substantially more As in groundwater discharge from developed areas than from environments where DOC appears to be of natural origin.

Barringer, Julia L.; Reilly, Pamela A.; Eberl, Dennis D.; Mumford, Adam C.; Benzel, William M.; Szabo, Zoltan; Shourds, Jennifer L.; Young, Lily Y.

2013-01-01

84

Ocean science: Links between surface and abyss  

NASA Astrophysics Data System (ADS)

The global ocean overturning circulation relies on dense deep waters being mixed back up to the surface. An observational analysis shows that turbulent mixing in the abyss around Antarctica varies with the strength of surface eddies and thus probably also wind speeds.

Maccready, Parker

2014-08-01

85

Response of Late Cretaceous migrating deltaic facies systems to sea level, tectonics, and sediment supply changes, New Jersey Coastal Plain, U.S.A.  

USGS Publications Warehouse

Paleogeographic, isopach, and deltaic lithofacies mapping of thirteen depositional sequences establish a 35 myr high resolution (> 1 Myr) record of Late Cretaceous wave- and tide-influenced deltaic sedimentation. We integrate sequences defined on the basis of lithologic, biostratigraphic, and Sr-isotope stratigraphy from cores with geophysical log data from 28 wells to further develop and extend methods and calibrations of well-log recognition of sequences and facies variations. This study reveals the northeastward migration of depocenters from the Cenomanian (ca. 98 Ma) through the earliest Danian (ca. 64 Ma) and documents five primary phases of paleodeltaic evolution in response to long-term eustatic changes, variations in sediment supply, the location of two long-lived fluvial axes, and thermoflexural basement subsidence: (1) Cenomanian-early Turonian deltaic facies exhibit marine and nonmarine facies and are concentrated in the central coastal plain; (2) high sediment rates, low sea level, and high accommodation rates in the northern coastal plain resulted in thick, marginal to nonmarine mixed-influenced deltaic facies during the Turonign-Coniacian; (3) comparatively low sediment rates and high long-term sea level in the Santonian resulted in a sediment-starved margin with low deltaic influence; (4) well-developed Campanian deltaic sequences expand to the north and exhibit wave reworking and longshore transport of sands, and (5) low sedimentation rates and high long-term sea level during the Maastrichtian resulted in the deposition of a sediment-starved glauconitic shelf. Our study illustrates the widely known variability of mixed-influence deltaic systems, but also documents the relative stability of deltaic facies systems on the 106-107 yr scale, with long periods of cyclically repeating systems tracts controlled by eustasy. Results from the Late Cretaceous further show that although eustasy provides the template for sequences globally, regional tectonics (rates of subsidence and accommodation), changes in sediment supply, proximity to sediment input, and flexural subsidence from depocenter loading determines the regional to local preservation and facies expression of sequences. Copyright ?? 2008, SEPM (Society for Sedimentary Geology).

Kulpecz, A. A.; Miller, K. G.; Sugarman, P. J.; Browning, J. V.

2008-01-01

86

28. STROMATOLITES WITH COCCOID AND FILAMENTOUS BLUE-GREEN ALGAE OF MESSINIAN AGE FROM SITE 374IONIAN ABYSSAL PLAINi  

Microsoft Academic Search

Microfossils interpreted as coccoid and filamentous blue-green algae are found within disrupted stromatolitic laminae of Messinian age in Core 17 from Site 374, central Ionian Abyssal Plain, Mediterranean Sea (35°50.87'N; 18°11.78'E, depth 4078 m). The coccoids are morphologically similar to members of the living Aphanocapsa in size and habit while the filaments, though rarer than the coccoids, morphologically resemble empty

87

Environmental factors affecting distribution and abundance of bacteria, fungi and protozoa in subsurface sediments of the Upper Atlantic Coastal Plain, USA  

SciTech Connect

Exploratory statistical analyses of microbiological, hydrological and geochemical data for samples from four boreholes drilled into Upper Atlantic Coastal Plain sediments near the Savannah River Site, SC, showed highly significant correlations between bacterial abundance (AODC and CFU) and hydraulic conductivity (K). Sediment texture variables (% sand (S), % silt, % clay (C), and S/C) were strongly interrelated with K and, therefore, also correlated with bacterial abundance. AODC did not correlate with the concentrations of dissolved inorganic nitrogen (DIN) or dissolved organic carbon (DOC) in pore water. CFU also did not correlate with DIN, but a negative relationship was found between the CFU and DOC for sandy sediments, suggesting that microbial activity may control pore water DOC concentration. In some, but not all boreholes, AODC and CFU correlated negatively with pore water concentrations of metals and positively with pH. Protozoan abundance correlated strongly with AODC and CFU in the two boreholes closest to the recharge areas for their major aquifers. It also correlated with sediment texture variables, but not with K. Fungal abundance did not correlate with the abundance of other microbial types when data from individual boreholes were considered; however it did correlate with both bacterial and protozoan abundance when data from all four boreholes were combined. There was no relationship between fungal abundance and either K or sediment texture.

Levine, S.N.; Ghiorse, W.C.

1990-12-31

88

Environmental factors affecting distribution and abundance of bacteria, fungi and protozoa in subsurface sediments of the Upper Atlantic Coastal Plain, USA  

SciTech Connect

Exploratory statistical analyses of microbiological, hydrological and geochemical data for samples from four boreholes drilled into Upper Atlantic Coastal Plain sediments near the Savannah River Site, SC, showed highly significant correlations between bacterial abundance (AODC and CFU) and hydraulic conductivity (K). Sediment texture variables (% sand (S), % silt, % clay (C), and S/C) were strongly interrelated with K and, therefore, also correlated with bacterial abundance. AODC did not correlate with the concentrations of dissolved inorganic nitrogen (DIN) or dissolved organic carbon (DOC) in pore water. CFU also did not correlate with DIN, but a negative relationship was found between the CFU and DOC for sandy sediments, suggesting that microbial activity may control pore water DOC concentration. In some, but not all boreholes, AODC and CFU correlated negatively with pore water concentrations of metals and positively with pH. Protozoan abundance correlated strongly with AODC and CFU in the two boreholes closest to the recharge areas for their major aquifers. It also correlated with sediment texture variables, but not with K. Fungal abundance did not correlate with the abundance of other microbial types when data from individual boreholes were considered; however it did correlate with both bacterial and protozoan abundance when data from all four boreholes were combined. There was no relationship between fungal abundance and either K or sediment texture.

Levine, S.N.; Ghiorse, W.C.

1990-01-01

89

Dredged material isolation on the abyssal seafloor: A feasibility study. Final report  

SciTech Connect

This report is the result of an examination of the feasibility of isolating contaminated dredged material on the abyssal seafloor. The focus is on the technical and environmental factors that constrain the considerations of feasibility. A thorough conceptual design of a dredging to abyssal deposition system is analyzed with regard to each subsystem and to the entire operational concept. These subsystems include: (1) a low leakage dredge, (2) equipment for material handling and loading into geosynthetic fabric containers (GFCs), (3) the barge for transport and navigation, and (4) the subsystem for releasing the GFCs to sink to the abyssal seafloor isolation site. Particular consideration is given to the exclusion of dredged material from the ocean`s productive zone in the upper 1000 m. New theoretical models and previous empirical results are used to predict GFC motion through the water column and response to impact on the abyssal seafloor, including the case of potential release of contaminated, turbid water at impact. A geochemical model of the temporal and spatial evolution of the post-deposition geochemistry of the water column, the GFC contents and the sediments below is developed and analyzed; the results show that release of metals into the ocean waters would be insignificant. A model of the biological impacts of the introduction of dredged material in the abyssal environment is used to infer that: (1) biological diversity in the vicinity of the deposition site will be diminished, (2) biomass will be increased by dominance of a few fast growing, opportunistic benthic species, and (3) concentrations of trace elements and organic contaminant.

Valent, P.J.; Young, D.K.

1997-12-01

90

Iunconsistencies in Accumulation Rates of Black Sea Sediments Inferred from Records of Laminae and 210Pb  

NASA Astrophysics Data System (ADS)

Recently-published estimates for the age of the unit 1-unit 2 contact in Black Sea sediments based on accelerator mass spectrometry (AMS) 14C measurements [Jones, 1990; Calvert et al., 1991] appear to be older than those based on the previously published chronology based on lamina couplets [Degens et al., 1980; Hay, 1988] by a factor of 2 to 3. To help reconcile the differences, we compare sediment accumulation rates based on the 210Pb method with estimates based on lamina counts for two cores from the Black Sea abyssal plain. Accumulation rates estimated using the 210Pb technique have varied little over the last 150 years from the averages of 55 and 50 g m-2 yr-1 at stations in the western and eastern basins, respectively. These values are about a factor of 2 lower than accumulation rates derived by counting lamina couplets over the dated intervals. Close examination of the laminae suggests that the discrepancy exists both because it is difficult to count the very fine laminae and because a complete couplet is not deposited every year. In order to provide a useful stratigraphic horizon for future investigators studying sedimentary records of the Black Sea, we estimate the age of a distinct black marker horizon which can be easily identified across the entire abyssal plain to be 150±8 years (deposited in 1838±8 A.D.).

Crusius, J.; Anderson, R. F.

1992-04-01

91

A 200,000-year record of late Quaternary Aeolian sedimentation on the Southern High Plains and nearby Pecos River Valley, USA  

NASA Astrophysics Data System (ADS)

Presently stabilized Southern High Plains (SHP) dune systems have been repeatedly re-activated during the past 200,000 years, providing an archive of environmental and related climatic change for the late Quaternary. Our data set of 38 optically dated samples from four different localities identifies eolian activity from late-middle Pleistocene to the historic period. Oldest eolian sediments are from the Blackwater Draw Formation and indicate accretion during late-middle to late Pleistocene. Younger sediments dating from the later Pleistocene through the Holocene are found in the Muleshoe, Lea-Yoakum, Mescalero, and Monahans dunes that overlie the Blackwater Draw Formation. Muleshoe dunes accreted during the Late Pleistocene between 31 ± 3 and 27 ± 2 ka, while Holocene deposition transpired 7.5 ± 0.4, 4.0 ± 0.7 ka through 3.6 ± 0.4 ka, and between 1.3 ± 0.2 and 1.1 ± 0.1 ka. A period of dune building for Lea-Yoakum dune sediments occurred during the late Pleistocene (48 ± 5 ka), and the later Holocene (3.6 ± 0.4 ka). Mescalero and Monahans dunes were accreting during the later Pleistocene between 29 ± 3 and 22 ± 2 ka followed by a sequence of eolian sand deposited ca. 15 ka. Holocene eolian sedimentation for the Mescalero and Monahans dunes occurred 7.5 ± 0.8, 5.1 ± 0.5, 4.3 ± 0.4, and 2.0 ± 0.3 ka. Historic eolian deposition is identifiable in the dune chronology with multiple optical age estimates overlapping established drought events recorded ca. 1890, 1910, 1920, and during the 1930's when the North American "Dust Bowl" transpired. These Quaternary eolian deposits mantling the Southern High Plains are an important component of the surficial material of the region and provide a rich archive of past climatic change.

Rich, J.; Stokes, S.

2011-03-01

92

Diversity of Thiosulfate-Oxidizing Bacteria from Marine Sediments and Hydrothermal Vents†  

PubMed Central

Species diversity, phylogenetic affiliations, and environmental occurrence patterns of thiosulfate-oxidizing marine bacteria were investigated by using new isolates from serially diluted continental slope and deep-sea abyssal plain sediments collected off the coast of New England and strains cultured previously from Galapagos hydrothermal vent samples. The most frequently obtained new isolates, mostly from 103- and 104-fold dilutions of the continental slope sediment, oxidized thiosulfate to sulfate and fell into a distinct phylogenetic cluster of marine alpha-Proteobacteria. Phylogenetically and physiologically, these sediment strains resembled the sulfate-producing thiosulfate oxidizers from the Galapagos hydrothermal vents while showing habitat-related differences in growth temperature, rate and extent of thiosulfate utilization, and carbon substrate patterns. The abyssal deep-sea sediments yielded predominantly base-producing thiosulfate-oxidizing isolates related to Antarctic marine Psychroflexus species and other cold-water marine strains of the Cytophaga-Flavobacterium-Bacteroides phylum, in addition to gamma-proteobacterial isolates of the genera Pseudoalteromonas and Halomonas-Deleya. Bacterial thiosulfate oxidation is found in a wide phylogenetic spectrum of Flavobacteria and Proteobacteria. PMID:10919760

Teske, A.; Brinkhoff, T.; Muyzer, G.; Moser, D. P.; Rethmeier, J.; Jannasch, H. W.

2000-01-01

93

Maintenance of abyssal benthic foraminifera under high pressure and low temperature: some preliminary results  

NASA Astrophysics Data System (ADS)

Abyssal benthic foraminifera have been maintained alive for periods of several weeks under laboratory simulated deep-sea conditions of high pressure and low temperature. In separate experiments, bacterial-sized fluorescent microspheres and three species of microalgae were supplied as food particles. Subsequent light and electron microscopy showed that the algae had been ingested by several foraminiferal species. Furthermore, the fine structure of the foraminiferal cytoplasm was well-preserved which indicates, along with the ingestion of algal food, that they had remained in a viable condition during the incubation. Other observations indicate that abyssal benthic foraminifera ingest naturally occurring photosynthetic cells carried to the deep-sea bed by rapidly sedimenting aggregates. The ability to keep foraminifera originating from depths exceeding 4000 m alive in the laboratory paves the way for the experimental investigation of some important issues in deep-sea biology and palaeoceanography.

Turley, C. M.; Gooday, A. J.; Green, J. C.

1993-04-01

94

Estimates of historic, present, and future rates of surface displacement due to hydrodynamic autocompaction of Holocene sediments in the Louisiana delta plain  

NASA Astrophysics Data System (ADS)

Subsidence and resulting rapid relative sea level rise and wetland loss in Louisiana have been attributed to natural geologic (isostatic sediment loading, faulting, sediment compaction, dewatering) and human (subsurface fluid withdrawal, salt mining) processes, but we lack quantitative estimates of the relative contributions of each factor, and their role in future subsidence is largely unknown. Such information is critical for ongoing regional-scale wetland restoration plans. We attempt to isolate the component of subsidence attributable to compaction (gravity-driven reduction in porosity and resulting surface displacement) of sediments deposited above the Lower Wisconsin unconformity (<~18 k.y.) in the delta region. One-dimensional, multi-lithology compaction models based on Darcy flow and Terzaghi effective stress principles are solved using a finite difference technique, allowing calculations of cumulative sedimentation and surface displacement, as well as historic, present, and future (in the absence of further loading) rates of vertical surface displacement. Detailed modeling of the USGS/LGS P-1-90 boring (47 m recovered, 13 radiocarbon dates), at the LUMCON facility in Cocodrie, revealed relationships among sediment type, geotechnical parameters, depositional rate, time, and compaction rate. Results indicate that, regardless of variations in depositional history, present rates of surface displacement can be constrained by two end-member stratigraphic models: 100% sand and 100% mud. Shallow (0-200 m) borehole data from the U.S. Army Corps of Engineers have been used to interpolate a regional isopach of Holocene sediments for the Mississippi River alluvial valley and adjacent delta plain and to extend lithologic generalizations (topstratum/substratum) and suitable geotechnical parameters from the USGS boring. Regional-scale analysis allows comprehensive testing of the hypothesis that higher subsidence rates in the alluvial valley can be attributed to compaction of thicker Holocene deposits.

Meckel, T. A.; ten Brink, U.; Williams, S.

2005-05-01

95

Abyssal food limitation, ecosystem structure and climate change.  

PubMed

The abyssal seafloor covers more than 50% of the Earth and is postulated to be both a reservoir of biodiversity and a source of important ecosystem services. We show that ecosystem structure and function in the abyss are strongly modulated by the quantity and quality of detrital food material sinking from the surface ocean. Climate change and human activities (e.g. successful ocean fertilization) will alter patterns of sinking food flux to the deep ocean, substantially impacting the structure, function and biodiversity of abyssal ecosystems. Abyssal ecosystem response thus must be considered in assessments of the environmental impacts of global warming and ocean fertilization. PMID:18584909

Smith, Craig R; De Leo, Fabio C; Bernardino, Angelo F; Sweetman, Andrew K; Arbizu, Pedro Martinez

2008-09-01

96

Results of analyses performed on soil adjacent to penetrators emplaced into sediments at McCook, Nebraska, January 1976. [simulated penetration into wind-deposited sediments on Martian plains  

NASA Technical Reports Server (NTRS)

During 1976 several penetrators (full and 0.58 scale) were dropped into a test site McCook, Nebraska. The McCook site was selected because it simulated penetration into wind-deposited sediments (silts and sands) on Martian plains. The physical and chemical modifications found in the sediment after the penetrators' impact are described. Laboratory analyses have shown mineralogical and elemental changes are produced in the sediment next to the penetrator. Optical microscopy studies of material next to the skin of the penetrator revealed a layer of glassy material about 75 microns thick. Elemental analysis of a 0-1-mm layer of sediment next to the penetrator revealed increased concentrations for Cr, Fe, Ni, Mo, and reduced concentrations for Mg, Al Si, P, K, and Ca. The Cr, Fe, Ni, and Mo were in fragments abraded from the penetrator. Mineralogical changes occurring in the sediment next to the penetrator included the introduction of micron-size grains of alpha iron and several hydrated iron oxide minerals. The newly formed silicate minerals include metastable phases of silica (cristobalite, lechatelierite, and opal). The glassy material was mostly opal which formed when the host minerals (mica, calcite, and clay) decomposed. In summary, contaminants introduced by the penetrator occur up to 2 mm away from the penetrator's skin. Although volatile elements do migrate and new minerals are formed during the destruction of host minerals in the sediment, no changes were observed beyond the 2-mm distance. The analyses indicate 0.58-scale penetrators do effectively simulate full-scale testing for soil modification effects.

Blanchard, M.; Bunch, T.; Davis, A.; Kyte, F.; Shade, H.; Erlichman, J.; Polkowski, G.

1977-01-01

97

Extreme 2002: Mission to the Abyss  

NSDL National Science Digital Library

This is the expedition page of the 2002 Mission to the Abyss. Developed by the University of Delaware Graduate College of Marine Studies, the site highlights the mission and crew, seafloor geology, creature features, and high-tech tools used in the study. This interactive website allows students to explore the submersible Alvin, find out how hydrothermal vents form, define the deep ocean, study plate tectonics, and meet hydrothermal vent organisms. The site includes extreme experiments, including: compression of a fluid vs. a gas, rising under pressure, my cup shrinks, soda squeeze, and plant pressure.

2010-03-15

98

Distributions, sources, and ecological risks of DDT-related contaminants in water, suspended particulate matter, and sediments from Haihe Plain, Northern China.  

PubMed

The residual levels of dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDXs, including p,p'-DDT, DDD, and DDE) in water, suspended particulate matter (SPM), and sediments from major rivers, lakes, and reservoirs in Haihe Plain were measured with a gas chromatograph equipped with a (63)Ni microelectron capture detector. In the fall of 2004, the contents of the total DDXs in the water and SPM were 0.29 ± 0.69 ng L(-1) and 423.13 ± 577.85 ng g(-1) dry wt., respectively. In the spring of 2005, the total DDXs were 0.36 ± 0.91 ng L(-1) for water and 35.93 ± 62.65 ng g(-1) dry wt. for SPM. The average concentration of DDXs for sediments was 7.10 ± 7.57 ng g(-1) dry wt. during the two seasons. The Eastern-Hebei-Province Coastland River System was the most polluted, which was mainly attributable to the extensive use of DDT pesticide and dicofol in that system. Recent DDT inputs still occur in some regions, as indicated by DDT/(DDD + DDE) > 1 at 29-36 % of the sites for water and 55-61 % of the sites for SPM. The potential ecological risks of DDT in the water were assessed using a species sensitivity distribution model. Only shrimp and crabs were found to have potentially affected fraction values of 1.63 × 10(-3) to 2.27 × 10(-4), with probabilities beyond the hazardous concentration for 5 % of species (HC5) values of 1.90-2.56 %, suggesting only slight risks. DDXs in the sediments of some sites were also of potential risk to benthic organism based on consensus-based sediment quality guidelines. PMID:22580748

Wang, Yan; He, Wei; Qin, Ning; He, Qi-Shuang; Kong, Xiang-Zhen; Tao, Shu; Xu, Fu-Liu

2013-02-01

99

Eukaryotic Richness in the Abyss: Insights from Pyrotag Sequencing  

PubMed Central

Background The deep sea floor is considered one of the most diverse ecosystems on Earth. Recent environmental DNA surveys based on clone libraries of rRNA genes confirm this observation and reveal a high diversity of eukaryotes present in deep-sea sediment samples. However, environmental clone-library surveys yield only a modest number of sequences with which to evaluate the diversity of abyssal eukaryotes. Methodology/Principal Findings Here, we examined the richness of eukaryotic DNA in deep Arctic and Southern Ocean samples using massively parallel sequencing of the 18S ribosomal RNA (rRNA) V9 hypervariable region. In very small volumes of sediments, ranging from 0.35 to 0.7 g, we recovered up to 7,499 unique sequences per sample. By clustering sequences having up to 3 differences, we observed from 942 to 1756 Operational Taxonomic Units (OTUs) per sample. Taxonomic analyses of these OTUs showed that DNA of all major groups of eukaryotes is represented at the deep-sea floor. The dinoflagellates, cercozoans, ciliates, and euglenozoans predominate, contributing to 17%, 16%, 10%, and 8% of all assigned OTUs, respectively. Interestingly, many sequences represent photosynthetic taxa or are similar to those reported from the environmental surveys of surface waters. Moreover, each sample contained from 31 to 71 different metazoan OTUs despite the small sample volume collected. This indicates that a significant faction of the eukaryotic DNA sequences likely do not belong to living organisms, but represent either free, extracellular DNA or remains and resting stages of planktonic species. Conclusions/Significance In view of our study, the deep-sea floor appears as a global DNA repository, which preserves genetic information about organisms living in the sediment, as well as in the water column above it. This information can be used for future monitoring of past and present environmental changes. PMID:21483744

Pawlowski, Jan; Christen, Richard; Lecroq, Beatrice; Bachar, Dipankar; Shahbazkia, Hamid Reza; Amaral-Zettler, Linda; Guillou, Laure

2011-01-01

100

Mercury in bottom sediments of the Amur River, its flood-plain lakes and estuary, Eastern Siberia.  

PubMed

Mercury (Hg) is an element of a special concern in the Amur River basin, where numerous cinnabar deposits and manifestations have been prospected. Moreover, the territory is under heavy anthropogenic pressure due to intensive economic development that includes activities accompanied by noticeable emissions of Hg to the environment through poor waste management practices and accidental emergency discharges. Yet, information on Hg distribution and behavior in this region is scarce and inadequate. In order to evaluate Hg levels and fate in this vast territory, surveys of river, lake, and estuarine bottom sediments, as integral indicators of environmental status, were carried out in 1990, 1991, 1997, and 2004. The results showed the following: (1) stagnation of the Russian economy in the 1990s has resulted in a noticeable decrease of the Hg content in the Amur River sediments to the basin pristine level of about 0.05 mg kg(-1); (2) Hg distribution in the sediment depth proves the element redox-dependent behavior; (3) in some cases, Hg enrichment may be related to the long-term anthropogenic emission; (4) Hg concentration in bottom sediments was found to increase in the following order-the Amur River mouth, the estuary, and the Sea of Okhotsk, showing the weakly non-conservative Hg behavior during estuarine water mixing. PMID:19629736

Kot, Fyodor S; Bakanov, Konstantin G; Goryachev, Nikolay A

2010-09-01

101

Carbonate and siliciclastic deposits on slope and abyssal floor Adjacent to southwestern Florida platform  

SciTech Connect

Three distinct carbonate deposits have been identified on the slope and adjacent sea floor of the Southwestern Florida platform: (1) reef talus, recognized by shape and location, found on the upper slope of the Yucatan Channel and also east of the Marquesas Keys; (2) hemipelagic sediments, with complex sigmoidoblique bed forms, filling the intervening gap between the channel and Keys and forming two lobes on the floor of the northern Florida Straits; and (3) turbidite deposits, with chaotic internal bed forms, covering siliciclastic Mississippi fan sediments at the base of the canyons in the Florida escarpment. The source of the talus, eroded and transported during the many storms which frequent the region, is the reef complexes which have formed on the platform rim. The sediment of the other two deposits is of foraminiferal tests, produced in nutrient-rich waters at the shelf edge. Geophysical, geochemical, and sedimentological data suggest that the spatial relationships of these deposits are related to sea level variations. During extreme lowstands, with much of the shelf exposed, the dominant sedimentation is siliciclastic deposition on the abyssal floor, and slope talus development at the edge of the shelf. During a subsequent rise in sea level, after carbonate production on the shelf is initiated, sediment is transported southward to the head of the canyons and funneled to the abyssal floor. Subsequent rising sea level shifts the axis of transport farther on the shelf, bypassing the canyons and funneling the sediment through breaks in the carbonate reef-banks at the southern edge of the platform. At the sites of both the hemipelagic and the turbidite deposition, high-resolution seismic data indicate that at least three cycles of deposition have occurred.

Holmes, C.W.

1983-03-01

102

Modern alluvial fan and deltaic sedimentation in a foreland tectonic setting: the Lower Mesopotamian Plain and the Arabian Gulf  

NASA Astrophysics Data System (ADS)

The Arabo-Persian Gulf, generally considered as a classical carbonate basin, in fact also includes important terrigenous systems whose nature and geometry are related closely to the tectonic framework. The Gulf is bordered along its northeastern periphery by an active alpine system which constitutes a major source of both siliceous and calcareous detritus. There are four types of terrigenous discharge which are classified according to their structural relationships. Numerous alluvial fans terminate ephemeral consequent streams draining the flanks of anticlines forming the external parts of the Zagros Mountain belt. Alluvial-fan deltas studied in detail in southeastern Iran terminate semi-permanent streams which flow along major synclinal axis. They are composed mainly of fine carbonate detritus, part of which accumulates as spectacular marine mud banks. Two major types of delta occur. Relatively small marine deltas, associated with permanent antecedent streams which cross the Zagros fold system, are scattered along the Persian shoreline. The other is the a major deltaic complex which is associated with the Tigris-Euphrates Rivers. This system has prograded along the main axis of the Gulf, the resulting Mesopotamian Plain filling at least half of the original basin which, in early Quaternary times, extended from Hormuz to Syria.

Baltzer, Frédéric; Purser, Bruce H.

1990-05-01

103

Long-term change in benthopelagic fish abundance in the abyssal northeast Pacific Ocean.  

PubMed

Food web structure, particularly the relative importance of bottom-up and top-down control of animal abundances, is poorly known for the Earth's largest habitats: the abyssal plains. A unique 15-yr time series of climate, productivity, particulate flux, and abundance of primary consumers (primarily echinoderms) and secondary consumers (fish) was examined to elucidate the response of trophic levels to temporal variation in one another. Towed camera sled deployments in the abyssal northeast Pacific (4100 m water depth) showed that annual mean numbers of the dominant fish genus (Coryphaenoides spp.) more than doubled over the period 1989-2004. Coryphaenoides spp. abundance was significantly correlated with total abundance of mobile epibenthic megafauna (echinoderms), with changes in fish abundance lagging behind changes in the echinoderms. Direct correlations between surface climate and fish abundances, and particulate organic carbon (POC) flux and fish abundances, were insignificant, which may be related to the varied response of the potential prey taxa to climate and POC flux. This study provides a rare opportunity to study the long-term dynamics of an unexploited marine fish population and suggests a dominant role for bottom-up control in this system. PMID:16602284

Bailey, D M; Ruhl, H A; Smith, K L

2006-03-01

104

Analysis of the community structure of abyssal kinetoplastids revealed similar communities at larger spatial scales  

PubMed Central

Knowledge of the spatial scales of diversity is necessary to evaluate the mechanisms driving biodiversity and biogeography in the vast but poorly understood deep sea. The community structure of kinetoplastids, an important group of microbial eukaryotes belonging to the Euglenozoa, from all abyssal plains of the South Atlantic and two areas of the eastern Mediterranean was studied using partial small subunit ribosomal DNA gene clone libraries. A total of 1364 clones from 10 different regions were retrieved. The analysis revealed statistically not distinguishable communities from both the South-East Atlantic (Angola and Guinea Basin) and the South-West Atlantic (Angola and Brazil Basin) at spatial scales of 1000–3000?km, whereas all other communities were significantly differentiated from one another. It seems likely that multiple processes operate at the same time to shape communities of deep-sea kinetoplastids. Nevertheless, constant and homogenous environmental conditions over large spatial scales at abyssal depths, together with high dispersal capabilities of microbial eukaryotes, maintain best the results of statistically indistinguishable communities at larger spatial scales. PMID:22071346

Salani, Faezeh Shah; Arndt, Hartmut; Hausmann, Klaus; Nitsche, Frank; Scheckenbach, Frank

2012-01-01

105

Survival Of Magnetic Paleoclimatic Signals From Shallow To Deep Water Marine Redoxomorphic Sediments Across The Northwest Iberian Continental Margin  

NASA Astrophysics Data System (ADS)

The magnetic properties of marine sediments on the North Atlantic Iberian continental Margin are strongly dependent on the organic matter input to the sediments and the onset of reductive diagenesis. An onshore-offshore gradient in the intensity of early diagenesis was recently described for the Ría de Vigo, matched by similar patterns in the adjacent rias of Pontevedra and Muros. In the ria environments of NW Iberia, early diagenetic dissolution of magnetic minerals can lead to magnetite half-lives of a few decades, and virtually obliterates any paleoenvironmental signal carried by magnetic minerals, rendering magnetic properties especially useful for the study of early diagenesis dynamics. Early diagenesis has also been identified in sediments of the adjacent continental shelf and deeper environments of the Galician Bank and Iberian Abyssal Plain. However, in these settings, slower dissolution of magnetic minerals allows the preservation of paleoclimatic signatures on different temporal scales. For instance, magnetic properties of continental shelf sediments reveal periods of enhanced rainfall and continental sediment input to the shelf, coincident with the Roman Warm Period and Medieval Climatic Optimum. On the contrary, cold periods are associated with less detrital input. Furthermore, levels of intensified diagenesis are also recorded during cold periods, which have been interpreted as periods of intensified coastal upwelling probably related to long-term North Atlantic Oscillation positive state. At the Galician Bank and Iberian Abyssal Plain sediments early diagenesis is also pervasive, although a paleoceanographic record of changes in the concentration of magnetic minerals transported by water masses flowing from the Portuguese Margin can still be identified. In addition to the progressive dissolution of magnetic minerals with depth, bulk magnetic properties in these deep marine settings show strong dependence on the pelagic carbonate sedimentation and low-magnetic turbiditic sediments that originate in the Galician Bank. Thin levels of highly magnetic sediments have been identified as Heinrich events, which provide an easily identifiable chronostratigraphic marker and a very fast and cost-effective tool for core correlation on a regional scale. These case-studies on the magnetic properties of sediments from the NW Iberian Margin provide examples of the range of applications of environmental magnetism in marine sediments with variable degrees of early diagenetic alteration of their magnetic mineral assemblage.

Mohamed Falcon, K. J.; Rey, D.; Rubio, B.

2013-05-01

106

Scientific requirements for an abyssal benthic laboratory  

NASA Astrophysics Data System (ADS)

For over thirty years man has studied "outer space" and installed satellites which watch the surface of the Earth. The great depths of the world ocean are, however, practically unknown and there is an urgent need to put abyssal benthic laboratories into "inner space" in order to study basic phenomena of interest to marine science and climatology as well as man's impact on the oceans. In view of the numerous problems related to global change, as a first step emphasis should first be on the role of the oceans and their inherent processes, which are the focus of such international programmes as the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS). Multi-disciplinary registration of key events at selected key sites investigating the variability in time and space are of the utmost importance. The same methods and techniques must be used for the study of human impacts on the deep oceans caused by mining of metalliferous resources and by waste disposal as well as in basic studies. However, the investigation of the inner space of our planet has certain requirements. As long-term and large-scale investigations become more and more important, development of automized systems, largely independent from research vessels will be required. This will demand high capacities of energy for all technical functions as well as high storage capacities for data and samples. As a consequence the needs for two different—although overlapping—functional approaches are defined for future deep-sea deployments. (A) A system for long-term registration of the natural variability and long-term monitoring of human impacts: (B) A system for short-term observations and short-time experimentations. This report summarizes their technological demands. The envisioned interdisciplinary technology should deliver information on physical, biological and geochemical processes and their variabilities in the deep oceans. The prospected systems need to have the ability for real time video observation, data transfer and experimental manipulation, as well as sensing and sampling facilities with large storage capacities for long-term deployments. Prospective costs of the described multipurpose abyssal benthic laboratory will presumably exceed the funds for deep-sea research of a single country. A joint European effort could solve this problem and help to manifest a leading role for European marine science in international deep-sea and global change research.

Thiel, H.; Kirstein, K.-O.; Luth, C.; Luth, U.; Luther, G.; Meyer-Reil, L.-A.; Pfannkuche, O.; Weydert, M.

1994-03-01

107

A late Quaternary loess-paleosol pedosedimentary sequence at Monte Netto (northern Italy): loess sedimentation, soil formation and tectonics in the central Po Plain.  

NASA Astrophysics Data System (ADS)

In the area of the Po Plain south of Brescia several isolated hills are present (Castenedolo hill, Ciliverghe hill, and Monte Netto), corresponding to the top of Late Quaternary anticlines. The Castenedolo and Ciliverghe area was widely explored in the last decades and thick sequences of pedosediments furnished detailed archives for the evolution of this part of the Po Plain. A new thick and complex loess-paleosol sequence, resting upon fluvial and fluvioglacial deposits exposed in a clay pit at the top of the Monte Netto hill is being studied in great detail. The Monte Netto is a large flat hill, gently undulated at its top, and the clay pit was opened close to the centre of the anticline, where fluvial and fluvioglacial deposits are deformed. This succession, probably of middle Pleistocene age, is buried by a loess-paleosol sequence 2 to 7 m thick; the depth of the loess is related to its physiographic position, i.e. it becomes thicker going away from the top of the anticline. Furthermore, the upper pedosediments are faulted by bending-moment structures, developed during fold amplification and allow to date some of the latest movements of the anticline. A geopedological, sedimentological and micropedological investigation of the whole extension of the quarry shows a distinctive difference between the loess-paleosol sequence at the top of the anticline and the one placed at its southern fringe (150 m away). On the top of the anticline a deeply weathered red paleosols developed in loess underneath a weakly weathered loess. In this soil also a small lithic assemblage dating to the Middle Palaeolithic was found. The pedosedimentary sequence at the southern fringe of the anticline consists of several loess layers showing different degrees of weathering. According to OSL dating, the upper part of the sequence was formed in the Upper Pleistocene, when most of the loess at the margins of the Po Plain was deposited. A tentative model of the exposed profiles involves the burial of the anticline by loess layers since the Middle Pleistocene and their successive weathering (and probably truncation) during subsequent interglacials and interstadials. These events probably correspond to the number of loess-paleosol couplets identified in the outer part of the anticline. In this sense the light weathered horizons could represent buried paleosols. Furthermore, the highly rubfied paleosols at the top of the anticline should be regarded as a polygenetic soil or as a vetusol, developed near the surface for a long time since the Middle Pleistocene. The on-going geopedological, geoarchaeological and seismic analyses will permit to define the time and steps of development of the Monte Netto hill and help to clarify the climatic and tectonic context during which these sediments where deposited, deformed, and weathered.

Trombino, Luca; Zerboni, Andrea; Livio, Franz; Berlusconi, Andrea; Michetti, Alessandro M.; Spötl, Christoph; Rodnight, Helena

2013-04-01

108

Cross-equatorial flow through an abyssal channel under the complete Coriolis force: Two-dimensional solutions  

NASA Astrophysics Data System (ADS)

The component of the Coriolis force due to the locally horizontal component of the Earth's rotation vector is commonly neglected, under the so-called traditional approximation. We investigate the role of this "non-traditional" component of the Coriolis force in cross-equatorial flow of abyssal ocean currents. We focus on the Antarctic Bottom Water (AABW), which crosses from the southern to the northern hemisphere through the Ceara abyssal plain in the western Atlantic ocean. The bathymetry in this region resembles a northwestward channel, connecting the Brazil Basin in the south to the Guyana Basin in the north. South of the equator, the AABW leans against the western continental rise, consistent with a northward flow in approximate geostrophic balance. The AABW then crosses to the other side of the abyssal channel as it crosses the equator, and flows into the northern hemisphere leaning towards the east against the Mid-Atlantic Ridge. The non-traditional component of the Coriolis force is strongest close to the equator. The traditional component vanishes at the equator, being proportional to the locally vertical component of the Earth's rotation vector. The weak stratification of the abyssal ocean, and subsequent small internal deformation radius, defines a relatively short characteristic horizontal lengthscale that tends to make non-traditional effects more prominent. Additionally, the steep gradients of the channel bathymetry induce large vertical velocities, which are linked to zonal accelerations by the non-traditional components of the Coriolis force. We therefore expect non-traditional effects to play a substantial role in cross-equatorial transport of the AABW. We present asymptotic steady solutions for non-traditional shallow water flow through an idealised abyssal channel, oriented at an oblique angle to the equator. The current enters from the south, leaning up against the western side of the channel in approximate geostrophic balance, and crosses the channel as it crosses the equator. The "non-traditional" contribution to the planetary angular momentum must be balanced by stronger westward flow in the channel, which leads to an increased transport in a northwestward channel, and a reduced transport in a northeastward channel. Our results suggest that as much as 10-30% of the cross-equatorial flow of the AABW may be attributed to the non-traditional components of the Coriolis force.

Stewart, A. L.; Dellar, P. J.

109

Abyssal ostracods from the South and Equatorial Atlantic Ocean: Biological and paleoceanographic implications  

USGS Publications Warehouse

We report the distribution of ostracods from ???5000 m depth from the Southeast and Equatorial Atlantic Ocean recovered from the uppermost 10 cm of minimally disturbed sediments taken by multiple-corer during the R/V Meteor DIVA2 expedition M63.2. Five cores yielded the following major deep-sea genera: Krithe, Henryhowella, Poseidonamicus, Legitimocythere, Pseudobosquetina, and Pennyella. All genera are widely distributed in abyssal depths in the world's oceans and common in Cenozoic deep-sea sediments. The total number of ostracod specimens is higher and ostracod shell preservation is better near the sediment-water interface, especially at the 0-1 cm core depths. Core slices from ???5 to 10 cm were barren or yielded a few poorly preserved specimens. The DIVA2 cores show that deep-sea ostracod species inhabit corrosive bottom water near the carbonate compensation depth (CCD) even though their calcareous valves are rarely preserved as fossils in sediment cores due to postmortem dissolution. Their occurrence at great water depths may partially explain the well-known global distributions of major deep-sea taxa in the world's oceans, although further expeditions using minimal-disturbance sampling devices are needed to fill geographic gaps. ?? 2008 Elsevier Ltd. All rights reserved.

Yasuhara, M.; Cronin, T. M.; Martinez, Arbizu, P.

2008-01-01

110

Abyssal circulation of the southeastern Pacific and some geological implications  

Microsoft Academic Search

The abyssal circulation of the Pacific Ocean east of the East Pacific Rise is deduced from hydrographic data, supported by a few direct current measurements. Two main flow paths are recognized: across the Chile Rise into the Chile Basin, and thence northward into the Peru Basin and Panama Basin: and eastward across the East Pacific Rise into the Guatemala Basin

Peter Lonsdale

1976-01-01

111

Sediment transport and fan deposition in the Gulf of Alaska: Effects of transform motion on deep sea sedimentation  

SciTech Connect

GLORIA side-scan sonar images and two channel seismic profiles recently collected in the Gulf of Alaska reveal a major site of late Miocene to Recent terrigenous sediment accumulation on the oceanic plate adjacent to the Fairweather-Queen Charlotte transform and the Yakutat Terrane. Sediment moving across this margin has formed several large channel dominated fan systems that blanket the entire gulf and spill westward onto the Tufts Abyssal Plain. The Surveyor Fan, fed by the glaciers of the Yakutat Terrane and insulated from transform sediment source offset by the Terrane, has maintained a single channel course over the entire life of the fan. The Chirikov and Baranof fans receive their sediment supply from glaciofluvial point sources along the SE Alaska margin, separated from the fans by an active transform. The fans show a southward younging of channel ages consistent with the sense of plate motion. Early (late Miocene) deposition within the gulf was limited to the structural basin between the continental margin and the Kodiak-Bowie seamount chain. The geometry of these early depositional systems is poorly known, but available data suggest their channels were oriented NW-SE. Subsequent establishment of a depositional slope between the margin and the seamount chain, coupled with the filling of the basin, led to a reorganization into SW-NE channel systems. The fan bodies of the Gulf of Alaska are members of a distinct class of fans that are characterized by long distributary channels which persist to near the fan limits. This type of fan morphology is most often attributed to a predominantly fine-grained sediment supply. This is difficult to reconcile with the obvious proximal glacial source for much of the sediment supplied to these fans.

Stevenson, A.J.; Bruns, T.R.; Carlson, P.R. (Geological Survey, Palo Alto, CA (USA)); Dobson, M.R. (Univ. of College of Wales, Aberystwyth (Wales))

1990-06-01

112

Geology of Atlantic Coastal Plain  

SciTech Connect

The Atlantic Coastal Plain developed landward of a hinge zone on slowly subsiding continental crust during the postrift phase of the opening of the Atlantic Ocean. Generally, a wedge of marine and non-marine sediments reaches 2000m thickness near the Atlantic Coastline. Variations in deposition along strike in the coastal plain was controlled by tectonic movement of basins and structural highs which from north to south include the Raritan Embayment, South New Jersey High, Chesapeake-Delaware Basin, Norfolk Arch, Albemarle Embayment, Cape Fear Arch, Southeast Georgia Embayment and South Florida Basin. Postrift sedimentation was initiated during late Jurassic and early Cretaceous time adjacent to the faulted hinge zone which separates thicker unstretched continental crust beneath the coastal plain from thinner stretched crust beneath the outer Atlantic margin. Continental clastic and deltaic sediments were deposited in onlapping sequence from Long Island to northern Florida. During this time carbonate deposition was initiated in the South Florida Basin. Marine deposition of terrigenous sands, silts and clays occurred along the coastal plain in late Cenomanian time. Shallow carbonate deposition continued in Florida. Transgressive and regressive marine deposition was dominant in the coastal plain during late Cretaceous and Paleogene time. Deposition during the Neogene was affected by numerous changes in sea level and consequently it is stratigraphically incomplete and irregularly distributed. Many units lack precise biostratigraphic resolution.

Olsson, R.K.; Gohn, G.S.

1985-01-01

113

Abyssal recipes II: energetics of tidal and wind mixing  

Microsoft Academic Search

Without deep mixing, the ocean would turn, within a few thousand years, into a stagnant pool of cold salty water with equilibrium maintained locally by near-surface mixing and with very weak convectively driven surface-intensified circulation. (This result follows from Sandström’s theorem for a fluid heated and cooled at the surface.) In this context we revisit the 1966 “Abyssal Recipes”, which

Walter Munk; Carl Wunsch

1998-01-01

114

Feeding Preferences of Abyssal Macrofauna Inferred from In Situ Pulse Chase Experiments  

PubMed Central

Climatic fluctuations may significantly alter the taxonomic and biochemical composition of phytoplankton blooms and subsequently phytodetritus, the food source for the majority of deep-sea communities. To examine the response of abyssal benthic communities to different food resources we simulated a food sedimentation event containing diatoms and coccolithophorids at Station M in the NE Pacific. In one set of experiments we measured incorporation of diatomC and coccoN into the macrofauna using isotopically enriched 13C-diatoms and 15N-coccolithophores. In a second experiment we measured incorporation of C and N from dual-labelled (13C and 15N) diatoms. The second experiment was repeated 2 months later to assess the effect of seasonality. The simulated food pulses represented additions of 650 – 800 mg C m?2 and 120 mg N m?2 to the seafloor. In all cases rapid incorporation of tracer was observed within 4 days, with between 20% and 52% of the macrofauna displaying evidence of enrichment. However, incorporation levels of both diatomC and coccoN were low (<0.05% and 0.005% of the added C and N). Incorporation of labelled diatoms was similar during both June and September suggesting that the community was not food limited during either period. We found no evidence for selective ingestion of the different food types in the metazoan fauna suggesting that macrofauna do not have strong preferences for diatom vs. coccolithophore dominated phytodetrital pulses. C?N ratios from both experiments suggest that the metazoan macrofauna community appear to have higher C demands and/or assimilation efficiencies compared to N. Concomitantly, the foraminifera preferentially selected for diatomN over coccoN, and we suggest that this may be related to foraminiferal requirements for intracellular nitrate. These experiments provide evidence that abyssal faunal feeding strategies are in part driven by an organism's internal stoichiometric budgets and biochemical requirements. PMID:24303022

Jeffreys, Rachel M.; Burke, Ciara; Jamieson, Alan J.; Narayanaswamy, Bhavani E.; Ruhl, Henry A.; Smith, Kenneth L.; Witte, Ursula

2013-01-01

115

Plain Language  

Cancer.gov

The Plain Writing Act of 2010 requires federal agencies to write "clear Government communication that the public can understand and use." President Obama also emphasized the importance of establishing "a system of transparency, public participation, and collaboration" in his January 21, 2009, Memorandum on Transparency and Open Government.

116

A hydrodynamically modified, abyssal isopod fauna  

NASA Astrophysics Data System (ADS)

At the High Energy Benthic Boundary Layer Experiment (HEBBLE) site (4820 m depth in the western North Atlantic) periods of strong currents and sediment erosion alternate with periods of weak flow and massive deposition. We investigated the impact of this atypical hydrodynamic environment on the isopod fauna by testing for a difference in composition between the HEBBLE site and a tranquil location, the Deep Ocean Mining Environmental Study (DOMES) site A ( ca. 5000 m) in the equatorial Pacific. Epifaunal isopods were significantly less abundant at the HEBBLE site than at the comparison site despite significantly greater total isopod numbers at the HEBBLE site. We suggest that the hydrodynamic regime puts epifaunal isopods at risk, making them rare at the HEBBLE site.

Thistle, David; Wilson, George D. F.

1987-01-01

117

Sexual biochemistry in the deep sea – the link between phytoplankton and abyssal holothurians.  

E-print Network

??Holothurians play an important role in carbon cycling. They dominate the abyssal oceanic megabenthos, reworking large amounts of organic matter. Holothurians require essential organic nutrients,… (more)

Smith, Tania

2008-01-01

118

Reproductive patterns of the abyssal asteroid Styracaster elongatus from the N.E. Atlantic Ocean  

NASA Astrophysics Data System (ADS)

We analysed the reproductive biology of the asteroid species Styracaster elongatus based on time-series samples from a 5000-m-deep site on the Porcupine Abyssal Plain (N.E. Atlantic). The ratio of males to females, the gonadosomatic index (GI), and pyloric caecum index (PCI) were determined and the results were corroborated by histological examination of the gonads. Fecundity and oocyte-size distribution were determined by histological and image analyses. Styracaster elongatus is a gonochoric asteroid and the ratio of males to females was not significantly different throughout the year. Oogenesis was asynchronous. The previtellogenic oocytes grew to a size of ˜230 ?m before undergoing vitellogenesis. Maximum oocyte size was ˜620 ?m. The ovary volume was mainly occupied by small previtellogenic oocytes (100-150 ?m) at any one time. Mean GI was 6.38±3.30 for females and 9.04±4.1 for males. Mean PCI was 7.44±1.66 for females and 7.66±1.46 for males. Mean fecundity was 16,373±5988 oocites per female. There were no seasonal variations in GI and fecundity. There was evidence of a pyiloric caecum seasonal development for females and males. For S. elongatus there is no direct relationship among seasonal primary production at the surface and production of vitellogenic oocytes. Nevertheless, this species takes advantage of the pulse of phytodetritus to the seabed by increasing the storage of nutrients in the pyloric caecum in order to maintain a constant production of eggs and sperm.

Benítez-Villalobos, Francisco; Díaz-Martínez, Julia P.

2010-01-01

119

Sedimental Reasons  

NSDL National Science Digital Library

Visitors to this site can view satellite imagery and read an account of how remote sensing was employed to evaluate the extent of flooding and sediment load in rivers on the coastal plain of North Carolina as a result of Hurricane Floyd in September, 1999. This feature is part of NASA's Earth Observatory, a publication that focuses on Earth's climate and environmental change.

120

Meiofauna communities along an abyssal depth gradient in the Drake Passage  

NASA Astrophysics Data System (ADS)

Meiofauna standing stocks and community structure are reported for the first time for abyssal soft-sediment samples in Antarctic waters. At seven stations within a depth range of 2274-5194 m a total of 128 sediment cores were retrieved with a multiple corer (MUC) on board of the R.V. Polarstern during the ANDEEP-1 cruise (ANT XIX/3). The metazoan meiofauna (defined by a lower size limit of 40 ?m) was identified and counted, and one core per station was preserved for CPE, C/N, TOM and grain size analyses. Meiofauna densities are in the range of 2731 Ind./10 cm 2 at 2290 m depth and 75 Ind./10 cm 2 at 3597 m depth, with nematodes being the dominant group at all stations. Nematodes account for 84-94% followed by copepods with 2-8% of the total meiofauna. Other frequent taxa found at each station are kinorhynchs, loriciferans, tantulocarids, ostracods and tardigrades. There is a general tendency of decreasing abundances of metazoan meiofauna with increasing depth, but not all higher level taxa displayed this pattern. In addition, a tendency of decreasing higher taxon density with increasing depth was observed. Standing stocks are higher than the average found at similar depths in other oceans.

Gutzmann, E.; Martínez Arbizu, P.; Rose, A.; Veit-Köhler, G.

2004-07-01

121

Suspended sediment sources and tributary effects in the lower reaches of a coastal plain stream as indicated by radionuclides, Loco Bayou, Texas  

Microsoft Academic Search

Characterizing the dynamics of fluvial sediment sources over space and time is often critical in identifying human impacts on fluvial systems. Upland interfluve and subsoil sources of suspended sediment at Loco Bayou, Texas, were distinguished using 226Ra\\/ 232Th, 226Ra\\/ 230Th and, 228Ra\\/ 232Th. Source contributions were apportioned at three stations during within-bank and flood flows. 137Cs and 210Pb xs (excess

K. M. Yeager; P. H. Santschi; J. D. Phillips; B. E. Herbert

2005-01-01

122

2005 Nature Publishing Group In situ Os isotopes in abyssal peridotites bridge the  

E-print Network

). However, the osmium isotopic compositions of abyssal peridotites and MORB do not appear on the possibility of osmium contamination by sea water5 . Here we present a detailed study of magmatic sulphides (the main carrier of osmium) in abyssal peridotites and show that the 187 Os/188 Os ratio

Demouchy, Sylvie

123

Carbon dioxide release from the North Pacific abyss during the last deglaciation  

E-print Network

LETTERS Carbon dioxide release from the North Pacific abyss during the last deglaciation Eric D , John R. Southon6 & Roger Francois1 Atmospheric carbon dioxide concentrations were significantly lower dioxide occupied the North Pacific abyss during the Last Glacial Maximum. Despite an inferred increase

Gilli, Adrian

124

Mobility of authigenic rhenium, silver, and selenium during postdepositional oxidation in marine sediments  

USGS Publications Warehouse

Sedimentary records of redox-sensitive trace elements hold significant potential as indicators of paleoceanographic environmental conditions. Records of Re can reveal the intensity of past reducing conditions in sediments at the time of deposition, whereas records of Ag may record the magnitude of past diatom fluxes to the seafloor. Confidence in paleoenvironmental reconstruction from records of either metal, however, requires it to have experienced negligible redistribution since deposition. This study examines diagenetic rearrangements of Re and Ag that occur in response to exposure to bottom-water O2 in environments of low sedimentation rate, including Madeira Abyssal Plain turbidites and eastern Mediterranean basin sapropels. Authigenic Re was remobilized quantitatively by oxidation but poorly retained by the underlying sediments. All records are consistent with previous work demonstrating that only a limited reimmobilization of Re occurs preferentially in Corg-rich, reducing sediments. Silver was also mobilized quantitatively by oxidation, but it was subsequently immobilized more efficiently in all cases as sharp peaks immediately into anoxic conditions below active oxidation fronts, and these peaks remain immobile in anoxic conditions during long-term burial. Comparison of Ag, S, and Se records from various cores suggests that Ag is likely to have been immobilized as a selenide, a mechanism previously proposed for Hg in similar situations (Mercone et al., 1999). Coexisting narrow peaks of Ag and Hg with Se offer a means of assessing whether oxidative burndown has ever occurred at the top of Corg- and sulfide-rich sedimentary units. Although these results suggest that caution must be used when inferring paleoenvironmental information from records of Ag and Re in cores with low sediment accumulation rates (?1), they should not affect the promise that authigenic Ag and Re records hold for paleoenvironmental reconstruction in sediments with higher accumulation rates and where anoxic conditions have been maintained continuously.

Crusius, John; Thomson, John

2003-01-01

125

Mobile megafaunal activity monitored with a time-lapse camera in the abyssal North Pacific  

NASA Astrophysics Data System (ADS)

Epibenthic megafauna comprise a large fraction of the deep-sea benthic biomass and are considered important in bioturbation and sediment mineralization processes. However, the sparse and often patchy distribution of these animals makes them difficult to study on meaningful spatial and temporal scales. We used a new time-lapse camera system to measure the movements of mobile megafauna over a 3-month period across a 20 m 2 area of the abyssal sea floor in the eastern North Pacific. This free-vehicle camera system consisted of a time-lapse camera mounted in a tripod frame with a field marker, time releases and flotation assembly. Time-lapse photographs of the sea floor were taken hourly from March to June 1991 at a station off the central California coast (34°50'N, 123°00'W) at a depth of 4100 m. Megafaunal density reached a peak in April, immediately preceding inceased fluxes of particulate organic carbon (POC) and chlorophyll a measured in sediment traps at 50 m above bottom. Mobile megafauna were numerically dominated by the holothuroids, Abyssocucumis abyssorum, Peniagone vitrea and Elpidia minutissima. The total area traversed by the megafauna each day was estimated by summing the distance traveled between hourly photographs multiplied by the body width of each animal. Area traversed by the megafauna reached a peak in early May following the peak in faunal density and preceding the peak in POC flux in mid-May. The mobile megafauna traversed 88% of the 20 m 2 area of the sea floor over the 3-month period. Estimates of oxygen consumption for the dominant mobile megafauna revealed that these animals would consume only 1.6% of the particulate organic carbon flux entering the benthic boundary layer. However, the extensive area traversed by the mobile megafauna in a 3-month interval suggests that these animals are important as modifiers of the surface sediment, either through mixing or repackaging of material.

Smith, K. L.; Kaufmann, R. S.; Wakefield, W. W.

1993-11-01

126

The Late Pliocene Eltanin Impact: Documentation From Sediment Core Analyses  

NASA Technical Reports Server (NTRS)

The expeditions ANT-XII/4 (1995) and ANT-XVIII/5a (2001) of the RV POLARSTERN collected extensive bathymetric and seismic data sets as well as sediment cores from an area in the Bellingshausen Sea (eastern Pacific Southern Ocean) that allow the first comprehensive geoscientific documentation of an asteroid impact into a deep ocean (approx. 5 km) basin, named the Eltanin impact. Impact deposits have now been recovered from a total of more than 20 sediment cores collected in an area covering about 80,000 km2. Combined biomagnetostratigraphic dating places the impact event into the earliest Matuyama Chron, a period of enhanced climate variability. Sediment texture analyses and studies of sediment composition including grain size and microfossil distribution reveal the pattern of impact- related sediment disturbance and the sedimentary processes immediately following the impact event. The pattern is complicated by the San Martin Seamounts (approx. 57.5 S, 91 W), a large topographic elevation that rises up to 3000 m above the surrounding abyssal plain in the area affected by the Eltanin impact. The impact ripped up sediments as old as Eocene and probably Paleocene that have been redeposited in a chaotic assemblage. This is followed by a sequence sedimented from a turbulent flow at the sea floor, overprinted by fall-out of airborne meteoritic ejecta that settled trough the water column. Grain size distribution reveals the timing and interaction of the different sedimentary processes. The gathered estimate of ejecta mass deposited over the studied area, composed of shock-melted asteroidal material and unmelted meteorites including fragments up to 2.5 cm in diameter, point to an Eltanin asteroid larger than the 1 km in diameter size originally suggested as a minimum based on the ANT-XII/4 results. This places the energy released by the impact at the threshold of those considered to cause environmental disturbance at a global scale and it makes the impact a likely transport mechanism explaining the presence of extinct Cenozoic microfossils in the transantarctic Sirius Unit. Although a crater structure representing Eltanin ground zero has not been discovered, the distribution pattern of sediment disturbance and ejecta deposits now allows to better determine the central target area north of the San Martin Seamounts.

Gersonde, R.; Kyte, F.; Flores, J. A.; Becquey, S.

2002-01-01

127

Late-Holocene flooding and drought in the Northern Great Plains, USA, reconstructed from tree rings, lake sediments and ancient shorelines  

Microsoft Academic Search

During the AD 1990s the Waubay Lakes complex in eastern South Dakota experienced historically unprecedented high water levels. Property damage from this flooding led to an examination of the occurrence of past pluvial episodes and their relation to climate. A 1000-year hydroclimate reconstruction was developed from local bur oak (Quercus macrocarpa) tree-ring records and lake-sediment cores. Analysis of lake shoreline

M. D. Shapley; W. C. Johnson; D. R. Engstrom; W. R. Osterkamp

2005-01-01

128

Another Nail in the Coffin of the Glacial-Age Isolated Abyssal Reservoir Scenario  

NASA Astrophysics Data System (ADS)

Radiocarbon-age differences were determined for coexisting G. sacculifer-mixed benthic-foraminifera pairs from six glacial-age samples from an equatorial Pacific core at 4.4 km water depth. The results range from 1.6 to 2.8 kyrs and average 2.2 kyrs. Age differences based on P. obliquiloculata, N. dutertrei and G. tumida range from 0.1 to 1.5 kyrs and average 0.8 kyrs. Although the data set is certainly imperfect, as the sedimentation rate for this core averages only 2 cm kyr-1, biases resulting from bioturbation are to be expected. Despite these inadequacies, the results appear to eliminate the possibility that the demise of a salt-stabilized glacial-age isolated abyssal reservoir can be called upon to explain the 15 percent drop in surface ocean and atmospheric 14C to C ratio during the Mystery Interval (17.5 to 14.5 kyr). If the 14C to C decline were to be explained in this way, the expected benthic-planktic age difference would have to be at least 5 kyrs.

Broecker, W. S.; Clark, E. H.

2009-12-01

129

Active diagenetic formation of metal-rich layers in N. E. Atlantic sediments  

SciTech Connect

Sediment cores from the Porcupine Abyssal Plain exhibit an indurated layer 0.5-3 cm thick at depths of approximately 50 cm. This is some 15-20 cm below the glacial/Holocene transition as interpreted by radiocarbon dating and the palaeontological criteria of Ruddiman and McIntyre (1981). The layer is forming currently at the oxic/post-oxic boundary in the sediments, as revealed by pore water data: O{sub 2} and NO{sub 3}{sup {minus}} are present in solution above the layer, while Fe{sup 2+}, Mn{sup 2+}, PO{sub 4}{sup 3{minus}} and NH{sub 4}{plus} are present in solution below, and all these species show concentration gradients indicating fluxes into the layer. These data are consistent with the hypothesis for the initiation and sustained formation of such layers proposed by Wilson et al. (1986a,b). The elements Mn, Ni, Co, Fe, P, V, Cu, Zn and U are all enriched to varying degrees in the vicinity of the layer. Some differential stratification of these elements in the vertical, consistent with a redox control, is observed at one site with a 0.5 cm layer, with Mn, Ni and Co above, Fe, P, V and Cu in the layer, and U below. At another site the metal-rich layer had higher Fe and P concentrations and is more indurated. Here all enrichments except Co are contained within a single layer sample, 3 cm thick.

Wallace, H.E.; Thomson, J.; Wilson, T.R.S.; Weaver, P.P.E.; Higgs, N.C.; Hydes, D.J. (Institute of Oceanographic Sciences, Surrey (England))

1988-06-01

130

Active diagenetic formation of metal-rich layers in N. E. Atlantic sediments  

NASA Astrophysics Data System (ADS)

Sediment cores from the Porcupine Abyssal Plain exhibit an indurated layer 0.5-3 cm thick at depths of approximately 50 cm. This is some 15-20 cm below the glacial/Holocene transition as interpreted by radiocarbon dating and the palaeontological criteria of RUDDIMAN and MCINTYRE (1981). The layer is forming currently at the oxic/post-oxic boundary in the sediments, as revealed by pore water data: O 2 and NO -3 are present in solution above the layer, while Fe 2+, Mn 2+, PO 3-4 and NH +4 are present in solution below, and all these species show concentration gradients indicating fluxes into the layer. These data are consistent with the hypothesis for the initiation and sustained formation of such layers proposed by WILSONet al. (1986a,b). The elements Mn, Ni, Co, Fe, P, V, Cu, Zn and U are all enriched to varying degrees in the vicinity of the layer. Some differential stratification of these elements in the vertical, consistent with a redox control, is observed at one site with a 0.5 cm layer, with Mn, Ni and Co above, Fe, P, V and Cu in the layer, and U below. At another site the metal-rich layer has higher Fe and P concentrations and is more indurated. Here all enrichments except Co are contained within a single layer sample, 3 cm thick.

Wallace, H. E.; Thomson, J.; Wilson, T. R. S.; Weaver, P. P. E.; Higgs, N. C.; Hydes, D. J.

1988-06-01

131

Abyssal Peridotites and Mantle Melting Beneath Ocean Ridges  

NASA Astrophysics Data System (ADS)

Studies of abyssal peridotite from ultraslow and slow spreading ridges show significant regional variability; with a strong correlation between the compositions of peridotite averaged by locality and spatially associated MORB reflecting higher degrees of mantle melting near mantle hot spots. Local variability of peridotite compositions, however, is often large, and may equal the regional variability along ocean ridges. The latter is attributed to local melting and melt transport processes such as melt channelization or late-stage melt impregnation in the lithosphere. The observed regional correlation appears only when many samples are averaged to eliminate local and outcrop scale variability. Almost all the peridotites used in these correlations are from transforms, and therefore represent similar thermal and mantle melting histories. Thus, regional differences in mantle composition are preserved. Until recently, little data were available for peridotites away from transforms representing the central mantle environment beneath magmatic segments. This is key, as geophysical and geologic evidence suggest focused melt flow beneath slow spreading ridges. If so, beneath individual magmatic segments there should be a corresponding mantle melting cell in which melt is focused from a broad melting region to a melt transport zone at its mid-point that feeds an overlying crustal magmatic center. High melt fluxes in the transport zone would produce very depleted peridotites stripped of pyroxene by melt-rock reaction during magma ascent. Studies of peridotites far from transforms at ultraslow Gakkel and SW Indian Ridges indicate this is the case: with near-Cpx free intergranular harzburgite and dunite locally abundant in contrast to transform peridotites. Recent mapping of the plutonic foundation of an ancient 35-km long slow spreading ridge segment at the Kane Core Complex also found a narrow 10-km wide zone of focused melt flow through the mantle marked by abundant dunite and spatially associated troctolites. Abyssal peridotite studies show that melts are produced in a geometrically complex melting regime. Not all portions of the source region contribute equally, and the mantle itself is likely multi component, with different components contributing to different degrees depending on the melting regime. A geochemical conundrum, then, is that mantle compositions estimated by inverting MORB provide only a fictive mantle 'source' composition - and not its true composition. Average abyssal peridotite compositions from ultra-slow spreading ridges where little crust is produced are only slightly different than those from slow spreading ridges with normal crustal thickness - suggesting that the average mantle composition could be more depleted than has been thought, and that mantle veins may contribute in greater proportion to melt production than has been believed.

Dick, H. J.; Snow, J. E.; Hellebrand, E.; Shimizu, N.

2005-12-01

132

Saturation of the Internal Tides and Induced Mixing in the Abyssal Ocean  

E-print Network

As part of an ongoing effort to develop a parameterization of wave-induced abyssal mixing, the authors derive an heuristic model for nonlinear wave breaking and energy dissipation associated with internal tides. Then the ...

Bu?hler, Oliver

133

Organic-Carbon Sequestration in Soil/Sediment of the Mississippi River Deltaic Plain - Data; Landscape Distribution, Storage, and Inventory; Accumulation Rates; and Recent Loss, Including a Post-Katrina Preliminary Analysis (Chapter B)  

USGS Publications Warehouse

Soil/sediment of the Mississippi River deltaic plain (MRDP) in southeastern Louisiana is rich in organic carbon (OC). The MRDP contains about 2 percent of all OC in the surface meter of soil/sediment in the Mississippi River Basin (MRB). Environments within the MRDP differ in soil/sediment organic carbon (SOC) accumulation rate, storage, and inventory. The focus of this study was twofold: (1) develop a database for OC and bulk density for MRDP soil/sediment; and (2) estimate SOC storage, inventory, and accumulation rates for the dominant environments (brackish, intermediate, and fresh marsh; natural levee; distributary; backswamp; and swamp) in the MRDP. Comparative studies were conducted to determine which field and laboratory methods result in the most accurate and reproducible bulk-density values for each marsh environment. Sampling methods included push-core, vibracore, peat borer, and Hargis1 sampler. Bulk-density data for cores taken by the 'short push-core method' proved to be more internally consistent than data for samples collected by other methods. Laboratory methods to estimate OC concentration and inorganic-constituent concentration included mass spectrometry, coulometry, and loss-on-ignition. For the sampled MRDP environments, these methods were comparable. SOC storage was calculated for each core with adequate OC and bulk-density data. SOC inventory was calculated using core-specific data from this study and available published and unpublished pedon data linked to SSURGO2 map units. Sample age was estimated using isotopic cesium (137Cs), lead (210Pb), and carbon (14C), elemental Pb, palynomorphs, other stratigraphic markers, and written history. SOC accumulation rates were estimated for each core with adequate age data. Cesium-137 profiles for marsh soil/sediment are the least ambiguous. Levee and distributary 137Cs profiles show the effects of intermittent allochthonous input and/or sediment resuspension. Cesium-137 and 210Pb data gave the most consistent and interpretable information for age estimations of soil/sediment deposited during the 1900s. For several cores, isotopic 14C and 137Cs data allowed the 1963-64 nuclear weapons testing (NWT) peak-activity datum to be placed within a few-centimeter depth interval. In some cores, a too old 14C age (when compared to 137Cs and microstratigraphic-marker data) is the probable result of old carbon bound to clay minerals incorporated into the organic soil/sediment. Elemental Pb coupled with Pb source-function data allowed age estimation for soil/sediment that accumulated during the late 1920s through the 1980s. Exotic pollen (for example, Vigna unguiculata and Alternanthera philoxeroides) and other microstratigraphic indicators (for example, carbon spherules) allowed age estimations for marsh soil/sediment deposited during the settlement of New Orleans (1717-20) through the early 1900s. For this study, MRDP distributary and swamp environments were each represented by only one core, backswamp environment by two cores, all other environments by three or more cores. MRDP core data for the surface meter soil/sediment indicate that (1) coastal marshes, abandoned distributaries, and swamps have regional SOC-storage values >16 kg m-2; (2) swamps and abandoned distributaries have the highest SOC storage values (swamp, 44.8 kg m-2; abandoned distributary, 50.9 kg m-2); (3) fresh-to-brackish marsh environments have the second highest site-specific SOC-storage values; and (4) site-specific marsh SOC storage values decrease as the salinity of the environment increases (fresh-marsh, 36.2 kg m-2; intermediate marsh, 26.2 kg m-2; brackish marsh, 21.5 kg m-2). This inverse relation between salinity and SOC storage is opposite the regional systematic increase in SOC storage with increasing salinity that is evident when SOC storage is mapped by linking pedon data to SSURGO map units (fresh marsh, 47 kg m-2; intermediate marsh, 67 kg m-2; brackish marsh, 75 kg m-2; and salt marsh, 80 kg m-2). MRDP core data for this study also indicate that levees and backswamp have regional SOC-

Markewich, Helaine W.; Buell, Gary R.; Britsch, Louis D.; McGeehin, John P.; Robbins, John A.; Wrenn, John H.; Dillon, Douglas L.; Fries, Terry L.; Morehead, Nancy R.

2007-01-01

134

Methane in water columns and sediments of the north western Sea of Japan  

NASA Astrophysics Data System (ADS)

This paper presents the results of methane measurements in water and sediments, first performed along the north western continental slope and abyssal plain of the Sea of Japan. Methane concentrations in the study area were very low. However, some features of its distribution are revealed. The highest dissolved methane concentrations (10-14 nmol kg-1) are characteristic of the pycnocline layer at a depth of 30-50 m in the northern shallow stations. With increasing depth, the methane is reduced to minimum values (0.5-1.0 nmol kg-1). The greatest variability in methane concentrations was observed in the layers at 0-500 m, which can be explained by the hydrodynamic conditions of the environment on the slope. Methane plumes (1.7 and 1.3 nmol kg-1) on the northern section were recorded at the depth of 1250 and 1495 m, respectively. Plumes (1.2 nmol kg-1) are also observed on near bottom layers at the deepest (more than 3000 m) stations. CH4 concentration in bottom sediments is also low (from 1 nmol kg-1 at 7 cm level to 752 nmol kg-1 at the 53 cm level of the core sediment in the northern part). Reduced sediments in the southern part of the study region have maximal methane concentration for sediment (2549 nmol kg-1) at the horizon 44 cm bsf (below sea floor) with a smell of H2S. These results assume a close relation of CH4 with sediment properties. A few stations with maximum methane (86-101 nmol kg-1) in the surface sediment layer are at the foot of a steep slope. Herewith, the highest abundance of some pericarid species was observed at the points with the highest values of methane concentrations in the surface sediment layer. Weak methane seepage can cause anoxic marine waters. Methane emission from water to the atmosphere is low because its concentration is close to equilibrium in surface water. An improved formula for calculating the methane flux of water into the atmosphere, taking into account high wind speeds, is presented in the paper.

Vereshchagina, Olga F.; Korovitskaya, Elena V.; Mishukova, Galina I.

2013-02-01

135

In situ Os isotopes in abyssal peridotites bridge the isotopic gap between MORBs and their source mantle.  

PubMed

Abyssal peridotites are assumed to represent the mantle residue of mid-ocean-ridge basalts (MORBs). However, the osmium isotopic compositions of abyssal peridotites and MORB do not appear to be in equilibrium, raising questions about the cogenetic relationship between those two reservoirs. However, the cause of this isotopic mismatch is mainly due to a drastic filtering of the data based on the possibility of osmium contamination by sea water. Here we present a detailed study of magmatic sulphides (the main carrier of osmium) in abyssal peridotites and show that the 187Os/188Os ratio of these sulphides is of primary mantle origin and can reach radiogenic values suggesting equilibrium with MORB. Thus, the effect of sea water on the osmium systematics of abyssal peridotites has been overestimated and consequently there is no true osmium isotopic gap between MORBs and abyssal peridotites. PMID:16107845

Alard, Olivier; Luguet, Ambre; Pearson, Norman J; Griffin, William L; Lorand, Jean-Pierre; Gannoun, Abdelmouhcine; Burton, Kevin W; O'Reilly, Suzanne Y

2005-08-18

136

Varieties of Melt-Rock Interactions in Abyssal Peridotites  

NASA Astrophysics Data System (ADS)

Ocean Drilling Program cores of abyssal peridotite from Hess Deep (Leg 147) and near the Kane Fracture Zone (Leg 153) exhibit features suggesting that a variety of melt-rock interaction processes can influence their compositions. Shallow intrusion into peridotite by melt veins can produce small gabbroic intrusives, with local interaction with the host peridotite, leading to local enrichments in peridotite incompatible element budgets and changes in peridotite modes. This process reveals nothing about proposed reactive porous flow or melt-entrapment processes that might be influencing peridotite geochemistry at greater depth. Given the limited extent of our `outcrop' (one core diameter), it is possible that the gabbroic intrusive could be un-sampled, but that the chemical effects could be present in the core and mistaken for some other type of melt-rock reaction. The presence of these gabbroic veins in both suites of drilled peridotites shows that this type of process has demonstrably changed the geochemistry of parts of these cores. Other processes that could influence the geochemistry of these rocks include: 1. Melt-entrapment; the effects this have on the mode of peridotite will depend on the pressure at which the melt is entrapped and crystallizes and on the composition of the melt; if this occurs at shallow levels, then plagioclase will be present and the occurrence of melt-trapping will be obvious, but if it occurs at greater depths, then the melt will crystallize no plagioclase and the process will be cryptic. 2. Reactive porous flow; this process could also be cryptic, because in the absence of a set of samples that clearly represents simple melt-residues, the baseline against which modal and geochemical changes have occurred is lacking. Both suites of peridotites studied show evidence for Na enrichments, but in different styles. The Kane suite is pervasively enriched in Na above the amount that should be present based on fractional melting models, in samples that are distal from shallow gabbroic intrusives. The Hess Deep suite shows local enrichments in Na by a factor of > 30 over baseline Na levels. The causes of these different enrichment styles are being investigated and we are determining abundances of strongly incompatible trace elements in CPX by ion probe to constrain the histories of these suites.

Ross, K.; Elthon, D.

2003-12-01

137

Hydrogeologic framework of the Virginia coastal plain  

USGS Publications Warehouse

This report defines the hydrogeologic framework of the Virginia Coastal Plain and is a product of a comprehensive regional study to define the geology, hydrology, and geochemistry of the northern Atlantic Coastal Plain aquifer system extending from North Carolina to Long Island, New York. The Virginia Coastal Plain consists of an eastward-thickening wedge of generally unconsolidated, interbedded sands and clays, ranging in age from Early Cretaceous to Holocene. These sediments range in thickness from more than 6,000 feet beneath the northeastern part of the Eastern Shore Peninsula to nearly 0 feet along the Fall Line. Eight confined aquifers, eight confining units, and an uppermost water table aquifer are delineated as the hydrogeologic framework of the Coastal Plain sediments in Virginia. The nine regional aquifers, from oldest to youngest, are lower, middle, and upper Potomac, Brightseat, Aquia, Chickahominy-Piney Point, St. Marys-Choptank, Yorktown-Eastover, and Columbia. The Brightseat is a newly identified and correlated aquifer of early Paleoceneage. This study is one of other, similar studies of the Coastal Plain areas in North Carolina, Maryland-Delaware, New Jersey, and Long Island, New York. These combined studies provide a system of hydrogeologic units that can be identified and correlated throughout the northern Atlantic Coastal Plain. Data for this study were collected and analyzed from October 1979 to May 1983. The nine aquifers and eight confining units are identified and delineated by use of geophysical logs, drillers' information, and stratigraphic and paleontologic data. By correlating geophysical logs with hydrologic, stratigraphic, and paleontologic data throughout the Coastal Plain, a comprehensive multilayered framework of aquifers and confining units, each with distinct lithologic properties, was developed. Cross sections show the stratigraphic relationships of aquifers and confining units in the hydrogeologic framework of the Virginia Coastal Plain. Maps show confining-unit thicknesses and altitudes of aquifer tops, provide the basis for assigning aquifers to screened intervals of observation and production wells, and are used for the development of a comprehensive observation-well network in the Virginia Coastal Plain.

Meng, Andrew A., III; Harsh, John F.

1988-01-01

138

PhD position in Experimental Geochemistry MarieCurie Initial Training Network ABYSS (ESR10)  

E-print Network

on March 1, 2014. ABYSS brings together 10 European research groups and 4 partners from the private sector University (Germany) The Instituto Andaluz de Ciencias de la Tierra--a joint research institute between will work on mineral pattern formation in alkaline hydrothermal environments with J.M. GarciaRuiz and C J

Demouchy, Sylvie

139

The role of the geothermal heat flux in driving the abyssal ocean circulation  

NASA Astrophysics Data System (ADS)

The results presented in this paper demonstrate that the geothermal heat flux (GHF) from the solid Earth into the ocean plays a non-negligible role in determining both abyssal stratification and circulation strength. Based upon an ocean data set, we show that the map of upward heat flux at the ocean floor is consistent (within a factor of 2) with the ocean floor age-dependent map of GHF. The observed buoyancy flux above the ocean floor is consistent with previous suggestions that the GHF acts to erode the abyssal stratification and thereby enhances the strength of the abyssal circulation. Idealized numerical simulations are performed using a zonally averaged single-basin model which enables us to address the GHF impact as a function of the depth dependence of diapycnal diffusivity. We show that ignoring this vertical variation leads to an under-prediction of the influence of the GHF on the abyssal circulation. Independent of the diffusivity profile, introduction of the GHF in the model leads to steepening of the Southern Ocean isopycnals and to strengthening of the eddy-induced circulation and the Antarctic bottom water cell. The enhanced circulation ventilates the GHF derived heating to shallow depths, primarily in the Southern Ocean.

Mashayek, A.; Ferrari, R.; Vettoretti, G.; Peltier, W. R.

2013-06-01

140

A large abrupt change in the abyssal water masses of the eastern Mediterranean  

Microsoft Academic Search

In this letter we report observations showing, for the first time, the occurrence of a new, major transformation in the thermohaline cell of the eastern Mediterranean Sea. After 2 decades, during which waters of Aegean origin dominated the abyssal layers of that basin, the Adriatic Sea has returned to represent a major source of Eastern Mediterranean Deep Water (EMDW). The

Angelo Rubino; Dagmar Hainbucher

2007-01-01

141

Warming and Freshening in the Abyssal Southeastern Indian Ocean* GREGORY C. JOHNSON  

E-print Network

Warming and Freshening in the Abyssal Southeastern Indian Ocean* GREGORY C. JOHNSON NOAA. Johnson, NOAA/ Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Bldg. 3, Seattle, WA 98115. E-mail: gregory.c.johnson@noaa.gov 15 OCTOBER 2008 J O H N S O N E T A L . 5351 DOI: 10

Johnson, Gregory C.

142

Noble gas behavior during deformation and serpentinization of abyssal peridotites: St. Peter-St. Paul massif  

Microsoft Academic Search

We present new noble gas (He, Ne, Ar), Sr and Pb isotopic analyses of St. Peter-St. Paul (SPSP) abyssal peridotites sampled in 1998-1999 using the Nautile submersible (IFREMER). The goals of the study were to geochemically characterize both granular and mylonitized peridotites, and to evaluate the effects of mylonitization and serpentinization on rare gas concentrations and isotopic compositions. Samples included

J. Angel Amaya; M. D. Kurz; S. E. Sichel; J. Blusztajn

2010-01-01

143

Flow of grounded abyssal ocean currents along zonally-varying topography in spherical geometry  

NASA Astrophysics Data System (ADS)

Many of the abyssal currents in the oceans, associated with the equatorward motion of deep water masses produced by atmospheric cooling in high latitudes, are organized as mesoscale topographically-steered geostrophically-balanced grounded gravity currents, which flow along sloping continental boundaries. These currents form an important component in the deep "leg" of the meridional overturning circulation in the oceans. The spatial extent of these abyssal currents is hemispheric in scale. This raises the question of the role of planetary sphericity and differential rotation (from the viewpoint of the underlying local geostrophic balance) in determining the large scale kinematic structure of these flows. A steady nonlinear planetary-geostrophic model in spherical coordinates is presented describing the hemispheric-scale meridional flow of grounded abyssal currents on a sloping bottom. The model, which corresponds mathematically to a quasi-linear hyperbolic partial differential equation, can be solved explicitly for a cross-slope isopycnal field that is grounded (i.e., intersects the bottom on the up slope and down slope sides). The solutions possess decreasing abyssal current height in the equatorward direction while maintaining constant meridional mass flux and exhibit westward intensification as they flow toward the equator.

Swaters, G. E.

2013-05-01

144

Impacts of localized mixing and topography on the stationary abyssal circulation  

E-print Network

for the abyssal circulation is extended by introducing pronounced bathymetry in the form of a mid-ocean ridge mixing rates in the deep ocean. Locally enhanced upwelling over a mid-ocean ridge drives a - plume; Mauritzen et al., 2002; Heywood et al., 2002) than in mid-ocean (Kunze and Sanford, 1996), for example

Katsman, Caroline

145

Using Eulerian and Lagrangian Approaches to Investigate Wind-Driven Changes in the Southern Ocean Abyssal Circulation  

NASA Astrophysics Data System (ADS)

This study uses a global ocean eddy-permitting climate model to explore the export of abyssal water from the Southern Ocean and its sensitivity to projected twenty-first-century poleward-intensifying Southern Ocean wind stress. The authors investigate the abyssal flow pathways and transport using a combination of Lagrangian and Eulerian techniques. In an Eulerian format, the equator- and poleward flows within similar abyssal density classes are increased by the wind stress changes, making it difficult to explicitly diagnose changes in the abyssal export in a meridional overturning circulation framework. Lagrangian particle analyses are used to identify the major export pathways of Southern Ocean abyssal waters and reveal an increase in the number of particles exported to the subtropics from source regions around Antarctica in response to the wind forcing. Both the Lagrangian particle and Eulerian analyses identify transients as playing a key role in the abyssal export of water from the Southern Ocean. Wind-driven modifications to the potential energy component of the vorticity balance in the abyss are also found to impact the Southern Ocean barotropic circulation.

Spence, Paul; van Sebille, Erik; Saenko, Oleg; England, Matthew

2014-05-01

146

Biostratigraphy Beneath the CCD: Using Agglutinated Foraminifera to correlate abyssal sediments  

NASA Astrophysics Data System (ADS)

The sub-CCD areas of the ocean constitute the world's largest biotope, populated by diverse faunas of agglutinated foraminifera. A reasonable estimate for the diversity of modern agglutinated foraminifera in the deep ocean is a thousand species. Therefore the potential must exist to use their fossils for the purposes of stratigraphic correlation. In spite of over a hundred years of study on this fossil group, the Mesozoic to Cenozoic foraminiferal biostratigraphy of the sub-CCD areas are still only sparsely studied. One of the main focuses of Felix Gradstein's micropalaeontological reseach has been to improve our understanding of agglutinated foraminifera and their applications for biostratigraphy, especially in the northern hemisphere petroleum-producing basins. Over the past 20 years, quantitative biostratigraphical schemes based on agglutinated foraminifera have now been constructed for the Upper Cretaceous to Cenozoic sequences of the Labrador Margin, North Sea, Norwegian Sea, and Barents Sea. These zonal schemes have been correlated to the standard chronostratigraphy by means of planktonic microfossils, and can be compared to the benthic foraminiferal records obtained from North Atlantic DSDP/ODP sites to establish better correlations to the Geological Timescale, and to assess the utility of agglutinated foraminifera ranges and acmes for stratigraphic correlation. In addition to coining the term "flysch-type" agglutinated foraminifera, Felix Gradstein has pioneered the efforts to establish both local and supra-regional zonations using probabilitic methods to and incorporate these microfossils into standard zonal schemes. Although the stratigraphic ranges of agglutinated foraminifera are long in comparison to planktonic foraminifera and in many cases their total ranges are unknown, their high diversity in the North Atlantic offshore basins and the presence of distinctive acmes improves their value for local (basin-wide) biostratigraphical schemes. Both geographical and palaeobathymetrical differences in the ranges of taxa are observed, for example the ranges of some taxa extend to younger levels in the northern part of the Norwegian Sea. Nevertheless, by examining elements in common between the local zonation schemes, we are now much closer to the ultimate goal of defining a "standard" zonal scheme for sub-CCD biostratigraphy using agglutinated foraminifera.

Kaminski, Michael A.

2010-05-01

147

The Plains City Story  

ERIC Educational Resources Information Center

This case study portrays a contemporary phenomenon that affects many U.S. school districts. Specifically, the authors address the challenges that the superintendent of the Plains City school district faced as a result of a change in the demographic distribution of his district. The gradual development of the pig farming industry in Plains City…

van Olphen, Marcela; Rios, Francisco; Berube, William; Dexter, Robin; McCarthy, Robert

2006-01-01

148

Observation of the abyssal western boundary current in the Philippine Sea  

NASA Astrophysics Data System (ADS)

Mooring observations were conducted from July 16, 2011 to March 30, 2012 east of Mindanao, Philippines (127°2.8'E, 8°0.3'N) to observe the abyssal current at about 5 600 m deep and 500 m above the ocean bottom. Several features were revealed: 1) the observed abyssal current was highly variable with standard deviations of 57.3 mm/s and 34.0 mm/s, larger than the mean values of -31.9 and 16.6 mm/s for the zonal and meridional components, respectively; 2) low-frequency current longer than 6 days exhibited strong seasonal variation, flowing southeastward (mean flow direction of 119.0° clockwise from north) before about October 1, 2011 and northwestward (mean flow direction of 60.5° counter-clockwise from north) thereafter; 3) the high-frequency flow bands were dominated by tidal currents O1, K1, M2, and S2, and near-inertial currents, whose frequencies were higher than the local inertial frequency. The two diurnal tidal constituents were much stronger than the two semidiurnal ones. This study provides for the first time an observational insight into the abyssal western boundary current east of Mindanao based on long-term observations at one site. It is meaningful for further research into the deep and abyssal circulation over the whole Philippine Sea and the 3D structure of the western boundary current system in this region. More observational and high-resolution model studies are needed to examine the spatial structure and temporal variation of the abyssal current over a much larger space and longer period, their relation to the upper-layer circulation, and the underlying dynamics.

Zhai, Fangguo; Wang, Qingye; Hu, Dunxin; Guo, Xiaogang

2014-09-01

149

A comparative study on arsenic and humic substances in alluvial aquifers of Bengal delta plain (NW Bangladesh), Chianan plain (SW Taiwan) and Lanyang plain (NE Taiwan): implication of arsenic mobilization mechanisms.  

PubMed

Humic substances in groundwater and aquifer sediments from the arsenicosis and Blackfoot disease (BFD) affected areas in Bangladesh (Bengal delta plain) and Taiwan (Lanyang plain and Chianan plain) were characterized using fluorescence spectrophotometry and Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the mean concentration of As and relative intensity of fluorescent humic substances are higher in the Chianan plain groundwater than those in the Lanyang plain and Bengal delta plain groundwater. The mean As concentrations in Bengal delta plain, Chianan plain, and Lanyang plain are 50.65 ?g/l (2.8-170.8 ?g/l, n=20), 393 ?g/l (9-704 ?g/l, n=5), and 104.5 ?g/l (2.51-543 ?g/l, n = 6), respectively. Average concentrations and relative fluorescent intensity of humic substances in groundwater are 25.381 QSU (quinine standard unit) and 17.78 in the Bengal delta plain, 184.032 QSU and 128.41 in the Chianan plain, and 77.56 QSU and 53.43 in the Lanyang plain. Moreover, FT-IR analysis shows that the humic substances extracted from the Chianan plain groundwater contain phenolic, alkanes, aromatic ring and amine groups, which tend to form metal carbon bonds with As and other trace elements. By contrast, the spectra show that humic substances are largely absent from sediments and groundwater in the Bengal delta plain and Lanyang plain. The data suggest that the reductive dissolution of As-adsorbed Mn oxyhydroxides is the most probable mechanism for mobilization of As in the Bengal delta plain. However, in the Chianan plain and Lanyang plain, microbially mediated reductive dissolution of As-adsorbed amorphous/crystalline Fe oxyhydroxides in organic-rich sediments is the primary mechanism for releasing As to groundwater. High levels of As and humic substances possibly play a critical role in causing the unique BFD in the Chianan plain of SW Taiwan. PMID:20706862

Selim Reza, A H M; Jean, Jiin-Shuh; Yang, Huai-Jen; Lee, Ming-Kuo; Hsu, Hua-Fen; Liu, Chia-Chuan; Lee, Yao-Chang; Bundschuh, Jochen; Lin, Kao-Hong; Lee, Chi-Yu

2011-06-01

150

Early India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies in the Perth Abyssal Plain  

E-print Network

Early India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies the early spreading history between India and Australia during the Mesozoic breakup of Gondwana. However from Australia with Greater India during initial breakup at ~130 Ma, then rifted from India following

Granot, Roi

151

Geology, geochemistry, and tectonostratigraphic relations of the crystalline basement beneath the coastal plain of New Jersey and contiguous areas  

USGS Publications Warehouse

Coastal plain sediments are underlain by pre-Mesozoic crystalline rocks. The inner coastal plain is underlain by schist that is correlated with the Potomac Terrane, as well as by mafic rocks probably equivalent to the Wilmington or Bel Air-Rising Sun terranes. The northern and central outer coastal plain is underlain by metasedimentary rocks similar to the Brompton-Cameron Terrane. Rocks beneath the southern coastal plain probably correlate with those of the Chopawamsic and Roanoke Rapids terranes.

Volkert, Richard A.; Drake, Avery Ala, Jr.; Sugarman, Peter J.

1996-01-01

152

The Plains of Venus  

NASA Astrophysics Data System (ADS)

Volcanic plains units of various types comprise at least 80% of the surface of Venus. Though devoid of topographic splendor and, therefore often overlooked, these plains units house a spectacular array of volcanic, tectonic, and impact features. Here I propose that the plains hold the keys to understanding the resurfacing history of Venus and resolving the global stratigraphy debate. The quasi-random distribution of impact craters and the small number that have been conspicuously modified from the outside by plains-forming volcanism have led some to propose that Venus was catastrophically resurfaced around 725×375 Ma with little volcanism since. Challenges, however, hinge on interpretations of certain morphological characteristics of impact craters: For instance, Venusian impact craters exhibit either radar dark (smooth) floor deposits or bright, blocky floors. Bright floor craters (BFC) are typically 100-400 m deeper than dark floor craters (DFC). Furthermore, all 58 impact craters with ephemeral bright ejecta rays and/or distal parabolic ejecta patterns have bright floor deposits. This suggests that BFCs are younger, on average, than DFCs. These observations suggest that DFCs could be partially filled with lava during plains emplacement and, therefore, are not strictly younger than the plains units as widely held. Because the DFC group comprises ~80% of the total crater population on Venus the recalculated emplacement age of the plains would be ~145 Ma if DFCs are indeed volcanically modified during plains formation. Improved image and topographic data are required to measure stratigraphic and morphometric relationships and resolve this issue. Plains units are also home to an abundant and diverse set of volcanic features including steep-sided domes, shield fields, isolated volcanoes, collapse features and lava channels, some of which extend for 1000s of kilometers. The inferred viscosity range of plains-forming lavas, therefore, is immense, ranging from the extremely fluid flows (i.e., channel formers), to viscous, possibly felsic lavas of steep-sided domes. Wrinkle ridges deform many plains units and this has been taken to indicate that these ridges essentially form an early stratigraphic marker that limits subsequent volcanism to a minimum. However, subtle backscatter variations within many ridged plains units suggest (but do not prove) that some plains volcanism continued well after local ridge deformation ended. Furthermore, many of volcanic sources show little, if any, indications of tectonic modification and detailed analyses have concluded that resurfacing rates could be similar to those on Earth. Improving constraints on the rates and styles of volcanism within the plains could lend valuable insights into the evolution of Venus's internal heat budget and the transition from thin-lid to thick-lid tectonic regimes. Improved spatial and radiometric resolution of radar images would greatly improve abilities to construct the complex local stratigraphy of ridged plains. Constraining the resurfacing history of Venus is central to understanding how Earth-sized planets evolve and whether or not their evolutionary pathways lead to habitability. This goal can only be adequately addressed if broad coverage is added to the implementation strategies of any future mapping missions to Venus.

Sharpton, V. L.

2013-12-01

153

Magnetochemical Features in Recent Marine Sediments Across the Galician Atlantic Margin and their Stratigraphic Significance  

NASA Astrophysics Data System (ADS)

A significant part of the sedimentary magnetochemical signal in the marine realm is controlled by the variability of detrital inputs; especially ice-rafted debris (IRD), fall-outs from nepheloid layers (NL) and wind blow-outs; which have been widely reported in the scientific literature. Their magnetic properties have been commonly and quite successfully used to establish the stratigraphic correlation of cores from a given location, or more intently, as proxies that document climatically forced events. Soon after deposition, the balance between oxygen diffusion from oxic bottom waters into the sediment; sea bed remobilization by benthic organisms and currents; primary productivity; and sediment accumulation rates will determine the degree of alteration of these detrital signals during redoxomorphic diagenesis and subsequently, the degree and conditions of preservation of their detritally-based environmental information (mostly held by magnetite) and the addition of new information during the authigenesis of magnetically-interesting minerals (chiefly goethite, greigite and pyrite). The correct interpretation of the magnetochemical properties and their environmental significance depends on our ability to asses the intensity and nature of magnetic-sensitive early-diagenetic processes resulting from changes in the sediment accumulation rates and on the palaeoceanographic conditions affecting productivity through time. Much of the changes that took place over the last 30 ky in the different depositional and diagenetic realms of the Galician Continental Margin -spanning from high productivity low depth Rías, storm swept continent shelf, and down slope turbiditic aprons, and abyssal plain- can be assessed estimating the concentration and half life of magnetite; which is respectivelly controlled by detrital forcements and the balance between C/S and the site sedimentation rate. This paper will deal with the magnetochemical expression of these changes in the depositional and/or diagenetic environment from the point of view of the enviromagnetism, solid-phase geochemistry, with the additional support of radiometric dating and scanning electron microscopy texture analysis; and of how these information have been used to reconstruct the Late Pleistocene to Holocene sedimentation history across the Galician Atlantic Margin.

Rey, D.

2007-12-01

154

A glimpse into the deep of the Antarctic Polar Front - Diversity and abundance of abyssal molluscs  

NASA Astrophysics Data System (ADS)

Our knowledge of the biodiversity and distribution patterns of benthic deep-sea faunas is still limited, with large parts of the world's abyss unexplored, lacking ?-taxonomic data across oceans basins and especially of biogeographic transition zones between oceans. The Antarctic Polar Frontal Zone has been discussed as major biogeographic barrier hindering faunal exchange between Subantarctic and Antarctic provinces and conserving high rates of endemism in the Southern Ocean benthos. In the present study we report first, exploratory ?-taxonomy on the malacofauna sampled by means of an epibenthic sledge from four bathyal respectively abyssal stations (2732-4327 m depth) in the vicinity of the Antarctic Polar Front during the SYSTCO II expedition (SYSTem COupling in the Southern Ocean, RV Polarstern cruise ANT XXVIII/3). We identified 58 distinct molluscan taxa based on external morphology ('morphospecies'); of the 33 taxa successfully assigned to described species 94% were previously reported from the Southern Ocean, but 24% exhibit distribution ranges crossing the Polar Front. One North Atlantic scaphopod is reported for the first time in Antarctic waters. Our study supports that the Antarctic Polar Front does not serve as effective barrier preventing gene flow in deep-sea molluscs. The present dataset shows the general characteristics of deep-sea sampling: patchiness in distribution and a high degree of singletons. Overall molluscan abundances were generally low ranging between 3.60 and 24.65 ind./1000 m², but in comparison with equatorial and subtropic abyssal basins, gastropod species richness and abundance were reaching high values similar to high Antarctic stations. Comparison between high productivity and low productivity zones along the Polar Front suggests increased abundances and species richness in high productivity zones. Intensified sampling is needed, however, to outweigh stochastic errors and to evaluate the influence of carbon flux as driving factor to faunal composition and abundances of abyssal molluscs.

Jörger, K. M.; Schrödl, M.; Schwabe, E.; Würzberg, L.

2014-10-01

155

Tracing anthropogenic nutrient inputs to coastal plain ponds using stable Wayne Daniel1  

E-print Network

sediments. An evaluation of two coastal plain ponds, one affected by nutrient pollution (Duck Pond), and one and are habitats of many extremely rare plant species for such a small unit area. The water level of a coastal, 2008 #12;Abstract Coastal plain ponds harbor some of the worlds rarest plant species. Consequently

Vallino, Joseph J.

156

Abyssal Scavenging Communities attracted to Sargassum and fish in the Sargasso Sea  

NASA Astrophysics Data System (ADS)

Deep-sea communities rely on epipelagic surface production as a primary source of energy and food. The flux of phytodetritus drives many abyssal ecological processes but the flux of large particles such as nekton carcasses, macroalgae, and wood may also be important. Recent baited camera experiments noted that some abyssal fish consumed spinach and phytoplankton placed on the seafloor. To evaluate if fish or other scavengers would consume natural plant or macroalgal material falling to the deep-sea floor we conducted camera experiments using Sargassum or mackerel bait in the Sargasso Sea. A benthic community of invertebrates was attracted to Sargassum, which naturally falls to the seafloor in this area. In five instances it was observed that an isopod Bathyopsurus sp. removed a piece of Sargassum from the main clump and left the field of view with it. An ophiuroid is also observed handling a piece of Sargassum. The group of scavengers attracted to mackerel bait was very different and was dominated by large ophidiid fish. In contrast to studies elsewhere in the abyssal North Atlantic, only a small number of rattails are observed, which could be related to water depth or an ichthyofaunal zonal change between oligotrophic and eutrophic regions.

Fleury, Aharon G.; Drazen, Jeffrey C.

2013-02-01

157

Neogene paleogeography of western Snake River plain, Idaho and Oregon  

Microsoft Academic Search

Analysis of Miocene through Pleistocene siliciclastic and volcaniclastic sequences in the western Snake River Plain of Idaho and Oregon allows detailed paleogeographic reconstruction of sedimentation associated with the development of a rapidly subsiding continental basin. Extensional tectonism was accompanied by voluminous outpourings of basaltic and silicic volcanic material. These in turn were reworked basinward by marginal alluvial fan-braided stream networks

M. L. Porter; L. T. Middleton

1984-01-01

158

Flood Plain Management.  

E-print Network

or a major part of flood protection works and subsidized the use of the flood plain. Boulding (2) suggests that we need an entirely new philosophy for flood control, which may involve treating the river not as an enemy to be conquered but as a... of a more intensive utilization of flood lain acre- age. Studies indicate that flood plain encroachment oc- curs because of 1) ignorance of the flood hazard, 2) an- ticipation of further Federal protection, and 3) profitabil- ity to the private...

McNeely, John G.; Lacewell, Ronald D.

1976-01-01

159

Northern Plains Crater  

NASA Technical Reports Server (NTRS)

19 December 2004 Most craters on the martian northern lowland plains are filled and many of them are buried just beneath the surface, or are mostly buried. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example, in which only the crater's raised rim still pokes out above the surrounding plains. This crater is located near 46.2oN, 257.7oW. The image covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

2004-01-01

160

Plains Tectonics on Venus  

NASA Technical Reports Server (NTRS)

Tectonic deformation in the plains of Venus is pervasive, with virtually every area of the planet showing evidence for faulting or fracturing. This deformation can be classified into three general categories, defined by the intensity and areal extent of the surface deformation: distributed deformation, concentrated deformation, and local fracture patterns.

Banerdt, W. B.; McGill, G. E.; Zuber, M. T.

1996-01-01

161

ROLE OF LAND USE AND BMPS IN REDUCING THE EFFECT OF EXTREME MAGNITUDE EVENTS ON SEDIMENT AND POLLUTANT TRANSPORT IN THE SE US COASTAL PLAIN AND MISSISSIPPI ALLUVIAL VALLEY  

EPA Science Inventory

Suspended sediment is a major non-point source pollutant of surface waters. Best management practices (BMPs) and current landuse decisions may not be sufficient to protect water quality in a changing climate, as a result of a loss of efficiency at reducing suspended sedimen...

162

Abyssal peridotites reveal the near-chondritic Fe isotopic composition of the Earth  

NASA Astrophysics Data System (ADS)

Terrestrial oceanic and continental basalts are enriched by approximately +0.1‰ in 56Fe/54Fe ratio relative to primitive, undifferentiated meteorites (chondrites). The ?56Fe values of terrestrial basalts are also distinct from those of basalts from Mars and asteroid Vesta, which have chondritic Fe isotopic compositions. The processes responsible for the isotopic enrichment of terrestrial basalts are debated, in part because the Fe isotopic composition of the mantle source of terrestrial basalts is unknown. Here we report Fe isotopic measurements of abyssal peridotites, which are the residues of limited melting at oceanic ridges and are thus the best proxies for the composition of the convective portion of the mantle. Our data show that abyssal peridotites have a mean ?56Fe value of +0.010±0.007‰ (relative to IRMM-014), which is indistinguishable from chondrites. After correcting this data for seafloor weathering and mantle melting, we estimate the average Fe isotopic composition of the terrestrial mantle to be ?56Fe=+0.025±0.025‰, which is also indistinguishable from chondrites, within current analytical precision. We determine that the maximum shift in ?56Fe for peridotite residues during partial mantle melting is 0.01‰. Our results argue against isotopic fractionation during core-mantle differentiation or iron vaporization during the Moon-forming giant impact, because both processes would yield a bulk mantle ?56Fe value that is non-chondritic. In addition, our results suggest that disproportionation of mantle Fe2+-Fe3+ in perovskite and Fe0 metal and segregation of metal to the core could not have been a driver for Fe isotopic fractionation in the silicate mantle. Instead, the different iron isotopic compositions of abyssal peridotites and MORBs support mounting evidence for iron isotopic fractionation of melts but not residues during the formation of oceanic and continental crust.

Craddock, Paul R.; Warren, Jessica M.; Dauphas, Nicolas

2013-03-01

163

Exhuming Platy Plains  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-377, 31 May 2003

The vast plains of Mars located south of Cerberus and the Elysium volcanoes have a platy, textured surface thought to have formed by floods of thick mud or, more likely, very fluid lava. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows that the platy plain--which is the darker surface covering most of the northern two-thirds of this picture--is being exhumed from beneath a brighter material. The small ridges in the bright material are yardangs, a landform created by wind erosion. Wind is slowly eroding the bright material away, revealing the darker, platy surface below. This area is located near 4.3oN, 208.5oW. Sunlight illuminates the scene from the left/lower left.

2003-01-01

164

The geomorphology of the Mississippi River chenier plain  

USGS Publications Warehouse

The chenier plain of the Mississippi River is a shore-parallel zone of alternating transgressive clastic ridges separated by progradational mudflats. The term chenier is derived from the cajun term chene for oak, the tree species that colonizes the crests of the higher ridges. The Mississippi River chenier plain stretches 200 km from Sabine Pass, Texas, to Southwest Point, Louisiana and ranges between 20 and 30 km wide, with elevations of 2-6 m. The timing and the process of formation could be re-evaluated in the light of new chronostratigraphic findings in the Mississippi River delta plain. The stratigraphic relationship between the Teche and Lafourche delta complexes and Ship Shoal offshore indicates that these delta complexes belong to different delta plains that developed at different sealevels. It appears that the Teche delta complex is associated with the late Holocene delta plain which developed 7000 to 3000 yrs B.P. when sealevel stood 5-6 m lower than present. A regional transgression occurred between approximately 3000 BP and 2500 yrs B.P., leading to the transgressive submergence of the late Holocene delta plain, producing the regional Teche shoreline. The timing of this transgression conforms to the age of the most landward ridge in the chenier plain, the Little Chenier-Little Pecan Island trend, which dates at about 2500 yrs B.P. This ridge trend was originally interpreted as representing the Teche delta complex switching event with the landward Holocene/Pleistocene contact representing the high stand shoreline. The implication of this new interpretation is that the Little Chenier-Little Pecan Island trend represents the high stand shoreline, a continuation of the Teche shoreline separating the late Holocene and Recent delta plains, and that the Holocene/Pleistocene contact represents the leading edge of the marshes transgressing onto the Prairie Terrace. Significant mudflat progradation seems to require a westerly position of the Mississippi River, but the numerous different forms and ages of cheniers do not correspond well to the timing of major delta complex switching. Progradation of the chenier plain appears to be associated with building of the Recent delta plain and not the Teche complex of the late Holocene delta plain. The occurrence of individual ridges appears to be primarily tied to delta lobe switching within the Lafourche complex and variations in sediment supply from local rivers. The recent development of the Atchafalaya delta complex to the west is the closest position of an active distributary to the chenier plain since sealevel stabilization; a new episode of rapid mudflat progradation is thus taking place. ?? 1989.

Penland, S.; Suter, J. R.

1989-01-01

165

Rapid bioturbation in equatorial Pacific sediments: evidence from excess 234Th measurements  

Microsoft Academic Search

In order to evaluate bioturbation in equatorial Pacific sediments, profiles of excess 234Th were measured in cores collected during November and December 1992, at six abyssal sites along the JGOFS Equatorial Pacific 140°W transect, from 5°S to 9°N. Excess 234Th (half-life=24.1 days) was detected at all sites. Mean inventories ranged from a low of 0.25 dpm cm?2 at 9°N, to

R. H. Pope; D. J. Demaster; C. R. Smith; H. Seltmann

1996-01-01

166

Major Elements Budget Between Abyssal Peridotite And Seawater During The Serpentinization  

NASA Astrophysics Data System (ADS)

Water-Rock Interaction is one of the most hot-debated issues among geologists, geophysicists, as well as geochemists. Abyssal peridotites recovered from the seafloor are often greatly affected or alterated by seawater in the form of serpentinization. The alteration to the peridotites makes it difficult to do the straightforward analysis for its primary composition as it was settled in the upper mantle, which confine the usage of these rare direct samples from the mantle in the scientific study, such as mantle dynamics, mantle composition and crust-mantle interaction. Besides, It was revealed recently that the serpentinization of abyssal peridotites may give birth to the hydrothermal activity. The elements migration during the serpentinization may perform a great role on the chemical composition of the hydrothermal fluid, which can support a hidden chemosynthetic ecosystem in the abyssal seabed. The research work focused on the major elements behavior during the serpentinization by studying the partially serpentinized samples of abyssal peridotite from Southwest Indian Ridge. The primary mineral assemblage of peridotite is olivine (Mg2SiO4), orthopyroxene (Mg2Si2O6), clinopyroxene (CaMgSi2O6) and spinel ((Mg,Fe)(Al,Cr)2O4). The major chemical composition are usually as SiO2 (30~45wt.%), MgO (20~45 wt.%), FeO and Fe2O3 (total 5~15 wt.%). Besides there are very few MnO, CaO, Al2O3, Cr2O3, NiO, Na2O, K2O and H2O. While on the other hand the serpentinized peridotite shows a more complicated mineral assemblage, besides the primary minerals there are more alteration minerals, such as serpentine (Mg3[Si2O5](OH)4), magnetite (Fe3O4), talc (Mg3[Si4O10](OH)2), brucite (Mg(OH)2), tremolite (Ca2Mg5[Si8O22](OH)2), chromite (FeCr2O4), chlorite ((Mg,Fe)6[(Si,Al)4O10](OH)8), and other accessary minerals like native metals, sulfides, clay minerals and hornblende. According to the EMPA analysis, the serpentinized sample shows the chemical composition as SiO2(~40 wt.%), MgO(~30 wt.%), total FeO(~7 wt.%), Al2O3(~1 wt.%), MnO(~0.4 wt.%), Cr2O3(~0.3 wt.%), NiO(~0.2 wt.%), CaO(~0.2 wt.%), and very few TiO2, Na2O and K2O. The overall percentages for all the elements mentioned above are usually around 80wt.%, about 20% less than full percent, which indicates the volatile matters in the altered samples. Based on the preliminary study, we get the general picture for the major elements behavior during the alteration. Taking the abyssal peridotite for example, it gains large quantities of H and O in the form of H2O, and other volatile elements like F, Cl, B from the seawater during serpentinization. It may also get additional Na, K, Mg from the seawater as shown from the standardized concentration in primary minerals as well as altered minerals. It loses Fe, Al, Ca, Si during the serpentinization seen from the EMPA mapping results. The element Mn, Cr and Ni are relatively immobile during the alteration. To get more precise deduction as to the element budget during the alteration process, much more sensitive analytical instruments like LA-ICP-MS are needed. And more work need to be done to get the quantitive estimation for transferring rate of each element.

Yu, X.; Dong, Y.; Li, X.; Chu, F.

2012-12-01

167

Infuence of Underground Water on Hidromorphic Soils in a Protected Area of Aluvial Plain in Middle Part of Danube Basin  

Microsoft Academic Search

The soil genesis in the inundations of big rivers is closely associated with fluvial sedimentation. According to quantity and origin of deposite, the aluvial plain is consisted of folowing morphological forms: costal, central and near the terrace part. The objects of this work are hidromorphic soils of aluvial plains un the area of midle Danube basin. The pedological and hidrological

Ljiljana Nesi; Sasa Pekec; Petar Ivanisevic; Milivoj Beli

2010-01-01

168

Transport of typhoon-induced submarine sediment-laden flows off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

Since 2006, southern Taiwan experienced destructive typhoons and earthquakes which triggered large scale submarine landslides and turbidity currents and devastated many submarine cables off southwestern Taiwan. Most of cable breakages were located in the Gaoping (GPSC) and Fangliao (FLSC) submarine canyons which indicate submarine canyon is an important pathway for underwater gravity flows that induced by natural hazards. A series of investigations were conducted before and after Morakot typhoon, the sub-bottom profiler and core analysis results revealed the GPSC and FLSC may play different roles in transport sediment from coastal seas to the abyssal ocean during the typhoon invaded period. Off southwestern Taiwan, the GPSC and FLSC are incising from continental shelf to deep sea floor and both of them transport considerable amounts of sediment to the South China Sea. GPSC is directly connected to the Gaoping River on land. The hyperpycnal flows, formed during Typhoon Morakot, delivered coarse sands, gravels and branches of trees into GPSC and deposited at the upper reach. On the contrary, the FLSC, which is smaller, younger and confined to the slope, does not associate with any river on land. A series of turbidites and debrites, which composed by coarse slates, fractal shells, wood fragments and fresh leaves, were observed in cores collected from the head of FLSC through Gaoping slope to the lower reach of GPSC. It implies the torrential rains induced landslides at the southernmost Central Mountain Range may directly delivered large amount of slate fragments through narrow Gaoping shelf into the deep sea. Furthermore, according to Water Resources Agency's groundwater level monitoring data, during Typhoon Morakot, the groundwater level raised significantly at the coastal area of Pingtung Plain. The increased groundwater pressure may lead to high flux of submarine groundwater discharge and induced liquefaction on seafloor. From sub-bottom profiles, the liquefaction structures and chaotic deposits were found widely spread off southwestern Taiwan and we suggest it may highly related to the anomalous submarine groundwater discharge incident. Our results reveal the extreme weather induced catastrophic events (e.g. torrential rains, floods, stormy waves… etc.) can generate devastating sediment-laden flows both in the Gaoping and Fangliao Submarine Canyons and provide an efficient way for delivering organic carbon into the deep sea.

Su, C.; Cheng, Y.

2012-12-01

169

EDITORIAL -BASED ON MIR INVESTIGATIONS IN LAKE GENEVA Into the abyss of Lake Geneva: the elemo interdisciplinary field  

E-print Network

EDITORIAL - BASED ON MIR INVESTIGATIONS IN LAKE GENEVA Into the abyss of Lake Geneva: the elemo deep water dives in Lake Geneva. Research teams from several environmental science institutes, both of Lake Geneva. Using the MIRs allowed the scientists to see and precisely select the sites where

Gilli, Adrian

170

"First" abyssal record of Stenosemus exaratus (G.O. Sars, 1878) (Mollusca, Polyplacophora) in the North-Atlantic Ocean.  

PubMed

The first proven abyssal record of Stenosemus exaratus (G.O. Sars, 1878) is presented on the basis of an ROV study in the Irish Sea. For the first time in situ images of the species and data on the environmental parameters are provided. PMID:23794838

Allcock, Louise; Schwabe, Enrico

2013-01-01

171

Lipid, sterols and fatty acids of abyssal polychaetes, crustaceans, and a cnidarian from the northeast Pacific Ocean: food web implications  

Microsoft Academic Search

The lipid, sterol, and fatty acid compositions of the abyssal anemone Bathyphellia aus- tralis, the 3 polychaetes Laetmonice sp., Paradiopatra sp. and Travisia sp., 3 crustaceans (Munidopsis sp. and 2 lysianassid amphipods), and an unidentified caridean shrimp were determined from a site in the northeast Pacific Ocean. Lipid composition was dominated by phospholipids in most species. However, energy storage lipids

Jeffrey C. Drazen; Charles F. Phleger; Michaela A. Guest; Peter D. Nichols

2008-01-01

172

High Plains Regional Climate Center  

NSDL National Science Digital Library

The mission of the High Plains Regional Climate Center is to increase the use and availability of climate data in the High Plains region. This site contains a variety of climatic and hydrologic data from High Plains research projects. Data types include automated weather data, interactive climate summary maps, historical weather data, and an interactive climate atlas. Research projects include Nebraska soil moisture, crop phenology, and wind energy on the High Plains. This website also features relevant publications and a variety of weather and climate links.

Resources, School O.; Lincoln, University O.

173

Wet coastal plain tundra  

SciTech Connect

This years's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSW of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 43'W; Barrow Quadrangle, USGS, reflect an increase in breeding species of 31% over the 5-year average, while breeding density was up 22%. Ten species increased and only 4 decreased. There was a total of 17 species; 61.5 territorial males or females (171/km/sup 2/, 69/100 acres).

Myers, J.P.; McCaffery, B.J.; Pitelka, F.A.

1980-01-01

174

Plenty on the Plains  

NSDL National Science Digital Library

In this activity, learners compare the ways of life of Plains Native Americans who hunted and moved frequently to follow the buffalo herds, and Native Americans who farmed and lived in more permanent villages along the river valleys. As they learn about different ways of life, learners also explore the benefits of trading. Learners act out a trading scenario, in which they make and trade goods including wristbands and popcorn snacks. This activity is featured on pp.23-24 of the "One With the Earth: Native Americans and the Natural World" multidisciplinary unit of study for kindergarten through third grade.

Indianapolis, The C.

2014-04-30

175

Devil-Streaked Plain  

NASA Technical Reports Server (NTRS)

19 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark streaks on a plain south of the giant impact basin, Hellas Planitia. The streaks map the routes traveled by dozens of individual southern spring and early summer dust devils.

Location near: 68.4oS, 296.1oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

2006-01-01

176

Regional variation of total microbial biomass in sediments of the deep Arabian Sea  

NASA Astrophysics Data System (ADS)

Eight different sites from 2300 to 4420 m water depth in the Arabian Sea were sampled for a biochemical quantification of phospholipid concentrations in the sediments. This method serves as a measure of microbial biomass in marine sediments comprising all small-sized organisms, including bacteria, fungi, protozoa and metazoa. Phospholipid concentrations can be converted to carbon units as an estimate of total microbial biomass in the sediments. The average phospholipid concentrations in the surface sediments (0-1 cm) of the 4 abyssal sites ranged from 7 nmol cm -3 at the southern site (SAST, 10°N 65°E, 4425 m) to 29 nmol cm -3 at the western site (WAST, 16°N 60°E, 4045 m). The high values detected at the abyssal station WAST exceeded those in the literature for other abyssal sites and were comparable to values from the upper continental slope of the NE-Atlantic and the Arctic. At the four continental slope sites in the Arabian Sea, average phospholipid concentrations ranged from 9 to 53 nmol cm -3 with the maximum values at stations A (2314 m) and D (3142 m) close to the Omani coast. Records of particulate organic carbon flux to the deep sea are available for four of the investigated locations, allowing a test of the hypothesis that the standing stock of benthic microorganisms in the deep sea is controlled by substrate availability, i.e. particle sedimentation. Total microbial biomass in the surface sediments of the Arabian Sea was positively correlated with sedimentation rates, consistent with previous studies of other oceans. The use of the measurement of phospholipid concentrations as a proxy for input of particulate organic matter is discussed.

Boetius, Antje; Lochte, Karin

2000-01-01

177

The Kansas Plains  

E-print Network

The Kansas Plains An Exhibit from the Kansas Collection UNIVERSITY OF KANSAS LIBRARIES T R A V E L L I N G ACROSS KANSAS f r o m e a s t to west , one is a w a r e of a t rans i t ion f r o m the ta l l g r a s s P r a i r i e P l a i n... s with wooded val leys to the f lat , t r e e l e s s , ar id High P l a i n s of w e s t e r n K a n s a s . Wal ter P r e s c o t t Webb in The G r e a t P l a i n s explains the c h a r a c t e r i s t i c s of the plains environment and the f l o r a l...

Zimmerman, Karen P.

1973-01-01

178

Denitrification in Agriculturally Influenced Coastal Plain Streams  

NASA Astrophysics Data System (ADS)

Agricultural runoff from coastal plain watersheds contributes nitrogen to downstream estuarine and coastal waters. Nitrogen fuels eutrophication, which has resulted in increased algal biomass, hypoxia, and fish kills in the Neuse River Estuary, North Carolina. Denitrification is the sole mechanism of permanent nitrogen removal along the riverine to estuarine continuum, but its contribution to nitrogen attenuation in this system is not well understood. Denitrification rates measured seasonally in stream bed sediments were variable but showed a distinct spring maximum, which was likely associated with rising temperatures and added nitrogen from fertilizer application (0-150 umol N m-2 h-1 during the summer, fall and winter and 150-300 umol N m-2 h-1 in the spring). Reach-scale uptake experiments showed the potential for 65-98% retention of the watershed DIN load in ephemeral drainage ditches. Results indicated that nitrogen retention was high despite low hyporheic exchange that is typically associated with channelized streams with low gradients, straight channels and homogenous stream bed sediments. Comparison of direct denitrification rate measurements to reach scale uptake rates and a watershed mass balance showed considerable potential for nitrogen removal via denitrification in agricultural stream sediments.

McMillan, S. K.; Ensign, S. H.; Thompson, S. P.; Paerl, H. W.; Piehler, M. F.

2005-05-01

179

Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean.  

PubMed

The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (~4,000-m depth). Here we show that previous findings of food deficits are now punctuated by large episodic surpluses of particulate organic carbon reaching the sea floor, which meet utilization. Changing surface ocean conditions are translated to the deep ocean, where decadal peaks in supply, remineralization, and sequestration of organic carbon have broad implications for global carbon budget projections. PMID:24218565

Smith, Kenneth L; Ruhl, Henry A; Kahru, Mati; Huffard, Christine L; Sherman, Alana D

2013-12-01

180

Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean  

PubMed Central

The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (?4,000-m depth). Here we show that previous findings of food deficits are now punctuated by large episodic surpluses of particulate organic carbon reaching the sea floor, which meet utilization. Changing surface ocean conditions are translated to the deep ocean, where decadal peaks in supply, remineralization, and sequestration of organic carbon have broad implications for global carbon budget projections. PMID:24218565

Smith, Kenneth L.; Ruhl, Henry A.; Kahru, Mati; Huffard, Christine L.; Sherman, Alana D.

2013-01-01

181

Policy, law, and public opposition: the prospects for abyssal ocean waste disposal in the United States  

NASA Astrophysics Data System (ADS)

The ocean is one of several media available for the disposal of society's wastes. Recently, its use for this purpose has been curtailed sharply. In this paper, we describe the potential role of the ocean in an economically optimal multimedia waste disposal framework, review international agreements and U.S. laws regulating ocean disposal, and discuss the role of public perceptions and environmental agendas in present policies governing ocean disposal. Our focus is on the disposal in the abyssal ocean of wastes such as sewage sludge. We conclude that while the U.S. ban on ocean waste disposal may be reasonable in view of uncertainties about environmental costs, the effective ban on limited disposal for research purposes is more difficult to justify. A restoration of public trust in government institutions and in the waste management industry is a likely prerequisite for the relaxation of public opposition to any change in the present prohibitions.

Kite-Powell, Hauke L.; Hoagland, Porter; Jin, Di

1998-05-01

182

Asthma: in plain language.  

PubMed

The Community Asthma Program was designed to increase awareness of asthma among urban residents and to bring more people into available care. Educational sessions with patients indicated that many adults struggle with the complicated demands of managing a chronic disease. At the same time, however, a good deal of the written materials meant to provide information and assistance instead make inappropriate demands on the average adult reader. The project team members developed a glossary of asthma terms to improve communication between patients and providers and to help patients understand the materials commonly used in neighborhood health centers. We report on the development of the glossary and describe formative research activities, initial dissemination efforts, and an interim evaluation. Health literacy, included in the goals and objectives for Healthy People 2010, can be improved when health materials are written in plain language and designed for the existing skills of the average U.S. adult reader. PMID:15228789

Rudd, Rima E; Zobel, Emily K; Fanta, Christopher H; Surkan, Pamela; Rodriguez-Louis, Jacqueline; Valderrama, Yvette; Daltroy, Lawren H

2004-07-01

183

The Interior Lowland Plains Unit of Mars: Evidence for a Possible Mud Ocean and Induced Tectonic Deformation  

NASA Technical Reports Server (NTRS)

We conclude from MOC and MOLA data that the northern plains of Mars were infilled by a sediment-rich, mud ocean. Evidence for subsidence within the north polar basin and reversed channel-floor gradients are consistent with tectonic deformation due to the sediment load.

Tanaka, K. L.; Banerdt, W. B.

2000-01-01

184

Ages of Lunar Light Plains  

NASA Astrophysics Data System (ADS)

Light plains are characterized by their relative smoothness and lower crater densities (compared to the highlands), and their occurrence as crater fills. They also exhibit highland-like characteristics, such as high albedos (in comparison to mare basalts) and their geological and stratigraphic setting. Despite the long history of investigating light plains, there are still numerous open questions concerning their mode of emplacement, their mineralogical composition, their ages, and their origin. We dated 16 light plains with crater size-frequency distribution (CSFD) measurements. All dated regions were previously identified as light plains in the geologic maps [1-5] and either mapped as smooth light plains (Ip) or light plains with undulatory surfaces (INp). The studied light plains occur both inside and outside the South Pole-Aitken (SPA) basin within a latitudinal band between ~-36° and ~-75°. In particular, we investigated the following smooth light plains: Janssen (40.82°E, -44.96°; Ip [1]), Nishina (-170.8°E, -44.57°; Ip [2]), South of Nishina (Ip [2]), Obruchev (162.43°E, -38.67°; Ip [2]), Oresme (169.22°E, -42.61°, Ip [2]), Schrödinger (132.93°E, -74.73°; Ip [3]), Nearch (39.01°E, -58.58°; Ip [3]), Nasmyth (-56.39°E, -50.49°; Ip [3]), Manzinus (26.37°E, -67.51°; Ip [3]), Klaproth (-26.26°E, -69.85°; Ip [3]), Phocylides (-57.31°E, -52.79°, Ip [3]), Buffon (-133.53°E, -40.64°; Ip [4]), Roche (136.54°E, -42.37°; Ip [5]). We also dated the following light plains with undulatory surfaces: Koch (150.33°E, -42.13°; INp [2]), Garavito (156.78°E, -47.21°; INp [2]), Eötvös (134.43°E, -35.61°; INp [5]). Our CSFD measurements resulted in absolute model ages of 3.71 to 4.02 Ga for all investigated light plains, thus confirming the Imbrian and/or Nectarian ages of the geologic maps [1-5]. We only dated three INp light plains, but they appear to have ages that are close to the upper limit, i.e., 3.96-4.02 Ga. However, further CSFDs of INp light plains are necessary to corroborate this preliminary observation. In general, our new absolute model ages are similar to model ages derived for light plains north of Mare Frigoris (3.65-4.0 Ga) [6], light plains within the SPA basin (3.43-3.81 Ga) [7], and light plains in the surroundings of the Orientale and Imbrium basins (3.8-4.3 Ga) [8]. The ages are not only similar, but also show similar ranges. While our model ages vary by about 300 Ma, model ages of [6,7] exhibit ranges of ~350 Ma and ~380 Ma, respectively. Ages of [8] show a somewhat wider range of ~500 Ma. From this wide range in ages it has been concluded that a formation of the light plains by a single event (i.e., Orientale or Imbrium) is unlikely [6-8]. References: [1] Wilhelms and McCauley (1971), USGS I-703; [2] Stuart-Alexander (1978), USGS I-1047; [3] Wilhelms et al. (1979), USGS I-1162; [4] Scott et al. (1977), USGS I-1034; [5] Wilhelms and El-Baz (1977), USGS I-948; [6] Köhler et al. (2000), LPSC 31, #1822; [7] Thiessen et al. (2012), LPSC 43, #2060; [8] Neukum (1977b), Moon 17, 383-393.

Hiesinger, Harald; Howes van der Bogert, Carolyn; Thiessen, Fiona; Robinson, Mark

2013-04-01

185

Aerosols Over Yellow Sea Sediments  

NASA Technical Reports Server (NTRS)

This SeaWiFS image shows complex phytoplankton distribution patterns in the Bohai and Yellow seas. A wide band of brownish water along the coast north and south of the mouth of the Yangtze River indicates a heavy load of suspended sediment. The air over eastern central China and the Yellow Sea is thick with aerosols. Farther north over the Manchurian Plain and Greater Khingan Range, the air is much clearer.

2002-01-01

186

Sediment flux and the Anthropocene.  

PubMed

Data and computer simulations are reviewed to help better define the timing and magnitude of human influence on sediment flux--the Anthropocene epoch. Impacts on the Earth surface processes are not spatially or temporally homogeneous. Human influences on this sediment flux have a secondary effect on floodplain and delta-plain functions and sediment dispersal into the coastal ocean. Human impact on sediment production began 3000 years ago but accelerated more widely 1000 years ago. By the sixteenth century, societies were already engineering their environment. Early twentieth century mechanization has led to global signals of increased sediment flux in most large rivers. By the 1950s, this sediment disturbance signal reversed for many rivers owing to the proliferation of dams, and sediment load reduction below pristine conditions is the dominant signal today. A delta subsidence signal began in the 1930s and is now a dominant signal in terms of sea level for many coastal environments, overwhelming even the global warming imprint on sea level. Humans have engineered how most water and sediment are discharged into the coastal ocean. Hyperpycnal flow events have become more common for some rivers, and less common for other rivers. Bottom trawling is now widespread, suggesting that even continental shelves have received a significant but as yet quantified Anthropocene impact. The Anthropocene attains the level of a geological climate event, such as that seen in the transition between the Pleistocene and the Holocene. PMID:21282156

Syvitski, James P M; Kettner, Albert

2011-03-13

187

Southern Ocean abyssal heat uptake in fine and coarse resolution climate model simulations  

NASA Astrophysics Data System (ADS)

The recently observed warming of Antarctic Bottom Water (AABW) represents an important component of accumulated sea level rise and global ocean heat uptake. Yet in simulations of greenhouse warming with coarse resolution climate models (which parameterize ocean eddies), Southern Ocean heat uptake dominantly occurs within near-surface waters, which are subsequently transported northward and subducted at mid-latitudes. Here, we examine the response of the abyssal Southern Ocean to greenhouse forcing within a global climate model run with a fine resolution (eddy-resolving) ocean component, which more faithfully simulates AABW formation than its coarse resolution counterparts. We argue that AABW warming may play a more important role in Southern Ocean heat uptake than is suggested by the CMIP5 ensemble of coarse resolution models. We examine the heat uptake in the Southern Ocean using the Community Climate System Model version 3.5 (CCSM 3.5). The model was run at two resolutions in the ocean and sea ice components: coarse (1 degree), which is a standard resolution of many CMIP5 models, and fine (.1 degree), in which sea ice and AABW is formed more realistically. The atmosphere and land components were fixed throughout at .5 degrees resolution. Each version was forced identically with a 1% ramping of CO2 for 150 years. The fine resolution simulation produces more dense water in the control climate, which sinks to a more realistic depth. We attribute this to the improved simulation of sea ice formation regions granted by increasing the ocean model resolution. The reduction of AABW formation as the climate warms leads to a larger response at depth at fine resolution; below 2000 meters, the fine resolution simulation takes up two orders of magnitude more heat than at coarse resolution. We further propose a framework to weigh the amount of heat taken up at depth in the Southern Ocean by the timescale at which it is sequestered, giving more value to heating of regions with long ventilation timescales. Using this framework, the degree of deep ocean heating emerges as a key difference between fine and course resolution, and an important component of the total heat sequestered in the Southern Ocean. Our work suggests that realistic abyssal ocean heat uptake may be an important component missing from many standard resolution models, and may play an important role in the observed decrease in sea surface temperatures around Antarctica in recent decades.

Newsom, E. R.; Singh, H.; Bitz, C. M.

2013-12-01

188

Suspended particulate loads and transports in the nepheloid layer of the abyssal Atlantic Ocean  

USGS Publications Warehouse

Vertical profiles of light scattering from over 1000 L-DGO nephelometer stations in the Atlantic Ocean have been used to calculate mass concentrations of suspended particles based on a calibration from the western North American Basin. From these data are plotted the distributions of particulate concentrations at clear water and in the more turbid near-bottom water. Clear water is the broad minimum in concentration and light scattering that occurs at varying mid-depths in the water column. Concentrations at clear water are as much as one-to-two orders of magnitude lower than those in surface water but still reflect a similar geographic distribution: relatively higher concentrations at ocean margins, especially underneath upwelling areas, and the lowest concentrations underneath central gyre areas. These distributions within the clear water reflect surface-water biogenic productivity, lateral injection of particles from shelf areas and surface circulation patterns and require that the combination of downward vertical and horizontal transport processes of particles retain this pattern throughout the upper water column. Below clear water, the distribution of standing crops of suspended particulate concentrations in the lower water column are presented. The integration of mass of all particles per unit area (gross particulate standing crop) reflects a relative distribution similar to that at the surface and at clear water levels, superimposed on which is the strong imprint of boundary currents along the western margins of the Atlantic. Reducing the gross particulate standing crop by the integral of the concentration of clear water yields a net particulate standing crop. The distribution of this reflects primarily the interaction of circulating abyssal waters with the ocean bottom, i.e. a strong nepheloid layer which is coincident with western boundary currents and which diminishes in intensity equatorward. The resuspended particulate loads in the nepheloid layer of the basins west of the Mid-Atlantic Ridge, resulting from interaction of abyssal currents with the bottom, range from ??? 2 ?? 106 tons in the equatorial Guyana Basin to ??? 50 ?? 106 tons in the North American Basin. The total resuspended particulate load in the western basins (111 ?? 106 tons) is almost an order of magnitude greater than that in the basins east of the Mid-Atlantic Ridge (13 ?? 106 tons). The net northward flux of resuspended particles carried in the AABW drops from ??? 8 ?? 106 tons/year between the southern and northern ends of the Brazil Basin and remains ??? 1 ?? 106 tons/year across the Guyana Basin. ?? 1977.

Biscaye, P.E.; Eittreim, S.L.

1977-01-01

189

Structure and evolution of the abyssal jet in the Vema Channel of the South Atlantic  

NASA Astrophysics Data System (ADS)

The Vema Channel represents the only major conduit through which the deepest and coldest (<0.2 °C potential temperature) Antarctic Bottom Water (AABW) flows from the Argentine into the Brazil Basin. From 2003 to 2007 two current meter moorings were present on each side of the Vema Sill, close to the narrowest spot of the Vema Channel. The data from the moorings are compared with earlier current and temperature observations. On average the maximum current core lies ˜100 m above the bottom of the sill with a mean northward speed of 0.3 m s-1. Farther up in the water column where Lower Circumpolar Deep Water and North Atlantic Deep Water prevail, one finds a level of sluggish currents with a southward tendency in the sub-centimeter-per-second range. The lower boundary of a layer of 'no' motion was observed at ˜3700 m depth where the mean potential temperature amounts to 1.5 °C. The evolution of the abyssal warming phenomenon over the last decades with notable fluctuations at the choke point between the Argentine and the Brazil Basin differs from the more stable attitude of deep horizontal currents. Starting with CTD observations in 1972 we find a steady increase of temperatures of the coldest AABW in the Vema Channel. This general trend of rising abyssal potential temperatures of almost 2 mKelvin per year is based on mostly annual CTD observations. The overall warming trend is fully compatible with our three-year moored temperature series in agreement with earlier records with high temporal resolution. Distinct frequently fluctuating horizontal current shear between the western and eastern sides of the Vema Sill may be explained by two different catchment areas for AABW at the mouth of the Vema Channel. One pathway originates at the American continental rise and advects bottom water in form of the deep western boundary current. A second pathway is supplied by an eastern boundary current along the Mid Atlantic Ridge in the Argentine Basin. Both source waters merge at the channel entrance, mix, and their respective strengths can alternate within the sill area.

Zenk, Walter; Visbeck, Martin

2013-01-01

190

Genetic and Morphological Divergences in the Cosmopolitan Deep-Sea Amphipod Eurythenes gryllus Reveal a Diverse Abyss and a Bipolar Species  

PubMed Central

Eurythenes gryllus is one of the most widespread amphipod species, occurring in every ocean with a depth range covering the bathyal, abyssal and hadal zones. Previous studies, however, indicated the existence of several genetically and morphologically divergent lineages, questioning the assumption of its cosmopolitan and eurybathic distribution. For the first time, its genetic diversity was explored at the global scale (Arctic, Atlantic, Pacific and Southern oceans) by analyzing nuclear (28S rDNA) and mitochondrial (COI, 16S rDNA) sequence data using various species delimitation methods in a phylogeographic context. Nine putative species-level clades were identified within E. gryllus. A clear distinction was observed between samples collected at bathyal versus abyssal depths, with a genetic break occurring around 3,000 m. Two bathyal and two abyssal lineages showed a widespread distribution, while five other abyssal lineages each seemed to be restricted to a single ocean basin. The observed higher diversity in the abyss compared to the bathyal zone stands in contrast to the depth-differentiation hypothesis. Our results indicate that, despite the more uniform environment of the abyss and its presumed lack of obvious isolating barriers, abyssal populations might be more likely to show population differentiation and undergo speciation events than previously assumed. Potential factors influencing species’ origins and distributions, such as hydrostatic pressure, are discussed. In addition, morphological findings coincided with the molecular clades. Of all specimens available for examination, those of the bipolar bathyal clade seemed the most similar to the ‘true’ E. gryllus. We present the first molecular evidence for a bipolar distribution in a macro-benthic deep-sea organism. PMID:24086322

Havermans, Charlotte; Sonet, Gontran; d'Udekem d'Acoz, Cedric; Nagy, Zoltan T.; Martin, Patrick; Brix, Saskia; Riehl, Torben; Agrawal, Shobhit; Held, Christoph

2013-01-01

191

Genetic and morphological divergences in the cosmopolitan deep-sea amphipod Eurythenes gryllus reveal a diverse abyss and a bipolar species.  

PubMed

Eurythenes gryllus is one of the most widespread amphipod species, occurring in every ocean with a depth range covering the bathyal, abyssal and hadal zones. Previous studies, however, indicated the existence of several genetically and morphologically divergent lineages, questioning the assumption of its cosmopolitan and eurybathic distribution. For the first time, its genetic diversity was explored at the global scale (Arctic, Atlantic, Pacific and Southern oceans) by analyzing nuclear (28S rDNA) and mitochondrial (COI, 16S rDNA) sequence data using various species delimitation methods in a phylogeographic context. Nine putative species-level clades were identified within E. gryllus. A clear distinction was observed between samples collected at bathyal versus abyssal depths, with a genetic break occurring around 3,000 m. Two bathyal and two abyssal lineages showed a widespread distribution, while five other abyssal lineages each seemed to be restricted to a single ocean basin. The observed higher diversity in the abyss compared to the bathyal zone stands in contrast to the depth-differentiation hypothesis. Our results indicate that, despite the more uniform environment of the abyss and its presumed lack of obvious isolating barriers, abyssal populations might be more likely to show population differentiation and undergo speciation events than previously assumed. Potential factors influencing species' origins and distributions, such as hydrostatic pressure, are discussed. In addition, morphological findings coincided with the molecular clades. Of all specimens available for examination, those of the bipolar bathyal clade seemed the most similar to the 'true' E. gryllus. We present the first molecular evidence for a bipolar distribution in a macro-benthic deep-sea organism. PMID:24086322

Havermans, Charlotte; Sonet, Gontran; d'Udekem d'Acoz, Cédric; Nagy, Zoltán T; Martin, Patrick; Brix, Saskia; Riehl, Torben; Agrawal, Shobhit; Held, Christoph

2013-01-01

192

Seismic character of the BSR in the Ulleung Basin plain, East Sea (Japan Sea)  

Microsoft Academic Search

A bottom simulating reflector (BSR) was identified in multichannel seismic reflection profiles collected in the Ulleung Basin\\u000a plain, East Sea (Japan Sea). The BSR, occurring in densely stratified sediments, is observed very close to the boundary between\\u000a two sequences interpreted as low-energy turbidites\\/hemipelagic sediments and mass-transport deposits. The essential characteristics\\u000a of the BSR include its cross-cutting relationship to strata at

Han-Joon Kim; Gwang Hoon Lee; Hyeong-Tae Jou; Sang Hoon Lee; Dong-Geun Yoo; Nam-Hyung Koo; Gap-Sik Jeong; Bong-Chool Suk

2010-01-01

193

Mineralogy of the mid-ocean-ridge basalt source from neodymium isotopic composition of abyssal peridotites.  

PubMed

Inferring the melting process at mid-ocean ridges, and the physical conditions under which melting takes place, usually relies on the assumption of compositional similarity between all mid-ocean-ridge basalt sources. Models of mantle melting therefore tend to be restricted to those that consider the presence of only one lithology in the mantle, peridotite. Evidence from xenoliths and peridotite massifs show that after peridotite, pyroxenite and eclogite are the most abundant rock types in the mantle. But at mid-ocean ridges, where most of the melting takes place, and in ophiolites, pyroxenite is rarely found. Here we present neodymium isotopic compositions of abyssal peridotites to investigate whether peridotite can indeed be the sole source for mid-ocean-ridge basalts. By comparing the isotopic compositions of basalts and peridotites at two segments of the southwest Indian ridge, we show that a component other than peridotite is required to explain the low end of the (143)Nd/(144)Nd variations of the basalts. This component is likely to have a lower melting temperature than peridotite, such as pyroxenite or eclogite, which could explain why it is not observed at mid-ocean ridges. PMID:12097907

Salters, Vincent J M; Dick, Henry J B

2002-07-01

194

Evaluation of abyssal meiobenthos in the eastern central Pacific (Clarion-Clipperton fracture zone)  

NASA Astrophysics Data System (ADS)

Meiobenthos were sampled from 17 stations in the abyssal deep-sea system of the central Pacific centered around 14°N, 130°W at depths 4960-5154m, during the Nixo 47 R/V Jean Charcot cruise. Meiofaunal density range from 45-89 ind. 10cm 2. Predominant taxa are nematodes (84-100%) and copepods (0-10%). Rotifera, Polychaeta, and Acarina also occur. Nematodes are uniformly distributed spatially with 45 species or so; Monhysteridae is the dominant taxon, and Syringolaimus sp. (Ironidae) co-occurs faithfully. Low biomass (0.4-70.6?g 10cm 2) are attributed to supposed dwarfism of metazoan meiofauna and very high proportion (60-80%) of juveniles and pre-adult forms. The majority of protozoans and metazoans are detritus- or deposit-feeders; in addition symbiotic associations, coprophagy and gardening activities are frequent. In such an oligotrophic environment, low food supply may limit meiofaunal abundance, biomass and maturation, and to a lesser extent species richness.

Renaud-Mornant, Jeanne; Gourbault, Nicole

195

Human Responses to Middle Holocene (Altithermal) Climates on the North American Great Plains  

Microsoft Academic Search

The climate of the Great Plains during the middle Holocene varied considerably, but overall it was marked by a north–south gradient of increasingly warmer and drier conditions, with a reduction in effective moisture, surface water, and resource abundance, and an increase in resource patchiness, sediment weathering, erosion, and aeolian activity. Pronounced drought conditions were most evident on the Southern High

David J. Meltzer

1999-01-01

196

Freshwater and marine coupling in estuaries of the Mississippi River deltaic plain  

Microsoft Academic Search

The estuaries of Louisiana's Mississippi River deltaic plain (MRDP) exhibit sharp physical and biological contrasts due to their different successional stages in delta development. The Atchafalaya- Fourleague Bay complex is a young deltaic system with high freshwater and sediment inputs. The area has been undergoing rapid land building since 1973. The Barataria Basin estuary occupies a deltaic land mass which

CHRISTOPHER J. MADDEN; JOHN W. DAY; JOHN M. RANDALL

1988-01-01

197

Relationship of structural development and Cenozoic sedimentation, northern Gulf of Mexico  

SciTech Connect

Development of structure in the northern Gulf of Mexico, mainly listric faulting and salt features, is directly related to Cenozoic sedimentation. Essentially all oil and gas production in this region occurs in structural features resulting from faulting and/or salt movement. A thick section of continental shallow-water sediments rimming the entire Gulf of Mexico was deposited during overall Gulf subsidence in Mesozoic time. Very little sedimentation took place in the central Gulf, so that, at the close of the Mesozoic the central Gulf probably was of abyssal depths. Cenozoic sedimentation surpassed the rate of subsidence causing sediments to prograde across the Mesozoic shelf margin, with greatest deposition occurring gulfward of this margin. These depocenters or areas of thickest sedimentation prograded gulfward throughout time (in response to sediment supply) and migrated northeastward from south Texas to south Louisiana. Listric or growth faults that formed contemporaneously with deposition are a common structural feature developed during Cenozoic sedimentation. These features are apparently caused by differential loading of higher density sandstones on prodelta shales near the shelf margin. In those areas underlain by thicker salt, such as the Miocene and younger depocenters, there is greater involvement of salt in growth-fault development. Salt features, the other major type of producing structure, are developed by salt movement as a direct response to Cenozoic sediment loading. Initiation of salt movement is believed to be due to differential loading of prograding sediments. Further salt movement and structural development are completely dependent on continued sedimentation.

Humphris, C.C. Jr.

1985-02-01

198

Late Pleistocene marine transgression of North Slope coastal plain  

SciTech Connect

Two late Pleistocene marine transgressions of contrasting character are recorded by deposits of the Arctic coastal plain. Deposits of the oldest trangression extend from Harrison Bay west to near Barrow and contain a fauna that documents interglacial conditions. Five thermoluminescence (TL) dates on the marine deposits average 127 Ka and indicate a correlation with oxygen isotope stage 5e. Sedimentary structures characteristic of the swash zone occur at altitudes within the commonly accepted range (6 not equal 4m) for eustatic high sea level at that time, showing that this part of the coastal plain has been tectonically stable for the past 125,000 years. Deposits of the youngest transgression are glaciomarine sediments that contain ice-rafted erratics of Canadian provenance. They compose the flaxman member of the Gubik Formation and occur locally along the Beaufort Sea coast and inland to altitudes of about 7 m. TL dates on these sediments suggest that the Flaxman transgression occurred between 70 and 80 ka and is correlative with deposits dated to this interval that are exposed near sea level on the North Carolina coastal plain. However, the deep-sea oxygen-isotope record is commonly interpreted to indicate that sea level was below its modern position at that time. The present altitude of the Flaxman deposits cannot be attributed to tectonism because their distribution includes the part of the coastal plain determined to be tectonically stable for the past 125 ka. Isostatic depression and subsequent elevation are unlikely considering the correlative deposits of North Carolina. This paradox could be explained if enormous volumes of floating glacial ice were produced by the rapid breakup of a large part of the Laurentide ice sheet, and recent work indeed suggests that the Hudson Bay lowlands were ice free at this time.

Carter, L.D.

1985-04-01

199

Sediment Setback  

E-print Network

the sediment problem. Vegetation protects the soil from damage, and vegeta- tion and soil work together to maintain a nutrient balance. It also acts as a filter to remove sediment from run-off, preventing the sediment from entering lakes and rivers... the sediment problem. Vegetation protects the soil from damage, and vegeta- tion and soil work together to maintain a nutrient balance. It also acts as a filter to remove sediment from run-off, preventing the sediment from entering lakes and rivers...

Crawford, Amanda

2005-01-01

200

Two abyssal sites in the Southern Ocean influenced by different organic matter inputs: Environmental characterization and preliminary observations on the benthic foraminifera  

NASA Astrophysics Data System (ADS)

The abundance and diversity of the deep-sea benthos are intimately linked to inputs of organic matter from the euphotic zone. However, it is often difficult to isolate the influence of surface productivity on benthic ecosystems from other environmental factors. To this end, two abyssal sites (˜4200 m water depth) located under contrasting productivity regimes around the Crozet Plateau, in the Indian Ocean sector of the Southern Ocean, were sampled during the austral summer of 2004/2005. One site (M5), east of the Crozet Isles, was located beneath an area where there was an enduring seasonal phytoplankton bloom. The second site (M6) was located in an oligotrophic high-nutrient low-chlorophyll (HNLC) region to the south of the islands. Organic fluxes to the seafloor at these sites are thought to reflect the overlying productivities, so that the benthic environment to the east of the islands was more eutrophic than at the southerly station. All other environmental variables were similar at the two sites, which are located just 460 km apart. The concentrations of chlorophyll- a and total organic carbon in the surficial sediments were significantly greater at the relatively eutrophic site, east of the islands (M5), than at the southerly site (M6). Total nitrogen, however, was similar at both sites. Significantly higher phytopigment concentrations were observed in the surficial sediments at the eutrophic site; in particular, the concentration of chlorophyll- a was 3 times greater than at the southern site, although the freshness of the labile component, as measured by chlorophyll- a to pheophorbide ratio, was not different between sites. These results confirm that fluxes of organic matter to the seafloor were higher at the site located beneath the bloom region. This was reflected in the abundance and diversity of live (stained) and dead benthic foraminifera (>125 ?m), which were greater at the eutrophic site. The species composition of the dead foraminiferal assemblages were similar at both sites, however, and were dominated by Nuttallides umbonifera, Pullenia bulloides, and Melonis pompiloides. An exception was the "phytodetritus species" Epistominella exigua, which was more abundant at the eutrophic site, indicating a larger seasonal component to the export under the bloom region. Differences in the organic matter input regimes at the two sites appear to influence the abundance and diversity, but not the overall species composition, of the foraminiferal assemblages.

Hughes, J. A.; Smith, T.; Chaillan, F.; Bett, B. J.; Billett, D. S. M.; Boorman, B.; Fisher, E. H.; Frenz, M.; Wolff, G. A.

2007-09-01

201

Spatial and temporal variations in the grain-size characteristics of historical flood plain deposits, Blue River, Wisconsin, USA  

Microsoft Academic Search

This study examined vertical, lateral, and downstream variations in the grain-size characteristics of historical (post-1830) overbank deposits in a watershed that has experienced high rates of accelerated flood plain sedimentation. More than 800 samples were collected from 53 cores along nine flood plain transects. Overbank deposits exhibit a coarsening-upward sequence attributed to historical changes in the sand content of source

Scott A. Lecce; Robert T. Pavlowsky

2004-01-01

202

Population genetic structure of the abyssal grenadier (Coryphaenoides armatus) around the mid-Atlantic ridge  

NASA Astrophysics Data System (ADS)

Understanding the factors that affect the levels and distribution of genetic diversity in oceanic and deep sea environments is a central focus in marine population genetics. Whilst it has been considered that the oceans represent a homogenous environment that would facilitate dispersal and minimise population structure, it is now clear that topographical features and current patterns can influence the extent of spatial gene flow and promote significant population genetic divergence even at local scales. Here we examine patterns of population genetic structure among N. Atlantic populations of the cosmopolitan abyssal grenadier Coryphaenoides armatus in relation to two hypothesised barriers to gene flow-the mid-Atlantic Ridge and the Charlie-Gibbs Fracture Zone/Sub-Polar Front. A suite of microsatellite markers were developed to examine the spatial pattern of allelic variation among 210 individuals from ten sampling locations encompassing sites east and west of the MAR and north and south of the CGFZ, plus a geographically distinct sample of individuals from the Crozet Islands in the Indian Ocean. Considerable genetic diversity was detected among individuals (na=5-13 and HO=0.46-0.69 across populations) but with an overall lack of genetic divergence between populations. Pairwise estimates of divergence among NE Atlantic samples were small and non-significant (max FST=0.04) and Structure-based Bayesian analysis of genetic clusters returned no distinct population structure. The only indication of genetic structure was between the Atlantic and Indian Oceans, with FST estimates of ca. 0.05. Patterns of genetic diversity and divergence are discussed in relation to what has been resolved in Coryphaenoides congeners, and what is known about the life history and ecology of C. armatus.

Ritchie, H.; Cousins, N. J.; Cregeen, S. J.; Piertney, S. B.

2013-12-01

203

62 FR 3152 - Plain English Disclosure  

Federal Register 2010, 2011, 2012, 2013

...229, 230, and 239 Plain English Disclosure; Proposed Rules Federal Register...1044] RIN 3235-AG88 Plain English Disclosure AGENCY: Securities and Exchange Commission...federal securities laws is full and fair disclosure, but investors must be able to...

1997-01-21

204

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2010 CFR

... RAILROAD LOCOMOTIVE SAFETY STANDARDS Safety Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not be cracked to the extent that it will leak...

2010-10-01

205

Aquatic Sediments.  

ERIC Educational Resources Information Center

Presents a literature review of aquatic sediments and its effect upon water quality, covering publications of 1976-77. This review includes: (1) sediment water interchange; (2) chemical and physical characterization; and (3) heavy water in sediments. A list of 129 references is also presented. (HM)

Sanville, W. D.; And Others

1978-01-01

206

AQUATIC SEDIMENTS  

EPA Science Inventory

One hundred seventeen literature references in the area of freshwater sediments were abstracted and synthesized to produce a review of sediment-related research for the period November, 1975 through October, 1976. Research areas covered included sediment-water interchange, sampli...

207

Serratotantulus chertoprudae gen. et sp. n. (Crustacea, Tantulocarida, Basipodellidae): A new tantulocaridan from the abyssal depths of the Indian Ocean.  

PubMed

A single tantulus larva was found at the abyssal depth of the Indian Ocean attached to a harpacticoid host of the family Cletodidae. It represents a new genus and species of Tantulocarida, family Basipodellidae. Its ultrastructure was studied with SEM. This genus can be easily distinguished from the other genera of Basipodellidae by the pore pattern, bilobed oral disk with strong longitudinal ridges and the posterior projection of the cephalic shield. A morphological analysis of two related families Basipodellidae and Deothertridae shows that they represent polyphyletic taxa and need further revision. PMID:21669851

Savchenko, Alexandra S; Kolbasov, Gregory A

2009-08-01

208

Numerical analysis of how sedimentation and redistribution of surficial sediments affects salt diapirism  

NASA Astrophysics Data System (ADS)

Two-dimensional finite-element models are used to study how sedimentation and redistribution of sediments on the upper surface affects the development of subsurface salt diapirs. A rising diapir creates a bulge flanked by topographic lows in a generally accumulating sedimentary pile. We find that the rate at which this topography is flattened by erosion and redeposition controls the style of diapirism. This is because the redistribution of material from topographic highs to flanking lows is equivalent to changing the effective forces acting on the salt. Redistributing a potential topography modulates diapiric growth rate. The main effects of including surficial sediment redistribution in numerical models of diapirism are: (1) diapirs grow 10-100 times faster; (2) diapirs may rise above their level of neutral buoyancy and extrude; (3) diapirs assume "finger" or "stock" like shapes rather than "mushroom" or balloon-on-string shapes; (4) layers in the surrounding sediments remain nearly horizontal and only steepen sharply near the diapir. In effect, the rate of redistribution of surficial overburden strongly controls the mode of diapirism. Sediment redistribution (referred to as erosion for brevity) is modeled using a one dimensional diffusion equation. We show the results of two different erosion rates: infinitely slow (no erosion) and extremely fast (which redistributes surficial sediments but does not remove them from the system). We show that the shapes of model diapirs rising beneath surfaces subjected to rapid erosion simulate salt diapirs in the Gulf of Mexico. Columnar diapirs indicate rapid deposition on the shelf and plug-like diapirs slow sedimentation on the abyssal plane. Diapirs rising beneath surfaces with negligible erosion have the "mushroom" shapes interpreted for salt diapirs in central Iran.

Poliakov, A. N. B.; van Balen, R.; Podladchikov, Yu; Daudre, B.; Cloetingh, S.; Talbot, C.

1993-11-01

209

Lava Flow on Coastal Plain  

USGS Multimedia Gallery

Lava flows remain active within the Royal Gardens subdivision and onto the coastal plain below. The number of surface flows has decreased however, due in part to a probable decrease in activity related to the ongoing deflation of Pu`u `? `?, and because the new lava tube branch...

2010-06-18

210

White Plains MetARs  

NSDL National Science Digital Library

In this activity, students use METeorological Aerodome Reports (METARs) to view changes in temperature, dew point, air pressure, sky condition, wind, and visibility at White Plains, New York. After studying the reports, they answer a series of questions related to radiation and insolation, radiative balance, and meteorological processes.

Kluge, Steve

211

Development of benthic biological monitoring criteria for disposal of low-level radioactive waste in the abyssal deep sea. Final report  

SciTech Connect

In order to develop recommendations for monitoring low-level radioactive waste dumpsites in the abyss, the report attempts a synthesis of information from three overlapping topical areas. First, U.S. Regulations governing the dumping and monitoring of wastes in the ocean are interpreted in a deep-sea context. Second, significant attention is given to experiences obtained from past dumping of low-level radioactive wastes in marine environments, both shallow-water and deep-sea. Third, the report attempts to apply the monitoring Requirements and conceptual approaches selected to the abyssal seafloor, based on present understandings of the deep-sea ecosystem.

Smith, C.R.; Present, T.M.C.; Jumars, P.A.

1988-09-01

212

Intensity of pelagic-benthic coupling in different regions along the Antarctic Polar Front - Clues from abyssal megafauna  

NASA Astrophysics Data System (ADS)

The zone surrounding the Antarctic Polar Front is a region characterized by elevated seasonal primary production. Studies on the implications for the fauna inhabiting the underlying deep-sea floor, however, are rare. The present study focuses on the abundance of megafaunal organisms caught by means of an Agassiz Trawl during the SYSTem COupling in the Southern Ocean II (SYSTCO II) expedition (RV Polarstern cruise ANT XXVIII/3). Biomass estimates in terms of volume as well as species richness of echinoderms were additionally taken into account. Abyssal stations (ca. 4000 m depth) located in three different regions along the Antarctic Polar Front characterized by different primary production regimes and oceanographic features were sampled. One shallower station (337 m depth) was used as reference station. Highest megafaunal abundances were found at the shallow station (147 individuals per 1000 m2). Megafaunal abundances were low to moderate at the abyssal stations (7.2-23.5 individuals per 1000 m2) with the exception of the region northwest of South Georgia, where distinctly higher abundances were found (up to 119.7 individuals per 1000 m2). The same pattern was observed for biomass estimates. At the other regions, magnitude of megafaunal abundances and echinoderm biomasses were found not to be linked to the surface levels of primary production. This indicates that strong pelagic-benthic coupling likely occurs only downstream of South Georgia. Echinoderm species richness does not appear to be directly related to the environmental conditions as it does not differ statistically between the considered areas.

Würzberg, Laura; Zinkann, Ann-Christine; Brandt, Angelika; Janussen, Dorte; Bohn, Jens M.; Schwabe, Enrico

2014-10-01

213

High-precision provenance determination using detrital-zircon ages and petrography of Quaternary sands on the eastern Snake River Plain, Idaho  

Microsoft Academic Search

The Big Lost trough is an upper Pliocene to Holocene sedimentary basin containing volcanic sills in the northeastern Snake River Plain, Idaho. The basin receives sediment primarily from Basin and Range fluvial systems of the Big Lost River, Little Lost River, and Birch Creek. The Big Lost trough contains a >200-m-thick succession of lacustrine, fluvial, eolian, and playa sediments, recording

J. K. Geslin; P. K. Link; C. M. Fanning

1999-01-01

214

Lead and osmium isotopic constraints on the oceanic mantle from single abyssal peridotite sulfides  

NASA Astrophysics Data System (ADS)

Single sulfides from abyssal peridotites have been analyzed for Pb and Re-Os to constrain the evolution of oceanic mantle composition. These represent the first analyses of Pb and Os isotopic compositions in the same sulfide grain. The sulfides are from Gakkel and Southwest Indian ridge peridotites, occur at <0.1% modal abundances, and contain 0.001-0.4 ppm Re, 0.003-5 ppm Os, and 0.12-12 ppm Pb. Sulfide Pb isotopic compositions extend from depleted (e.g., 206Pb/204Pb=17.0) to enriched (19.6), covering a larger range than associated basalts. The Os isotopic range of sulfides is more restricted, but extends from depleted (187Os/188Os=0.116) to enriched (0.150). Pb and Os concentrations and isotopic compositions co-vary, with correlation coefficients of 0.76-0.94. Both Pb and Re-Os isotopic data follow ?2 Ga isochrons, with isotopic compositions varying down to small (?1 km) length-scales and some sulfides containing supra-chondritic 187Re/188Os and 187Os/188Os. These observations are best explained by long-term recycling of oceanic lithosphere combined with melt extraction and refertilization at ancient ocean ridges, rather than a specific event at 2 Ga. The concentration of Pb in sulfides indicates that they host <4% of the mantle Pb budget. A re-evaluation of the mass balance of Pb in peridotites indicates that most mantle Pb is stored in silicate phases. The Pb partition coefficient between sulfide melt and silicate melt is estimated to be ?3, based on the correlation of Pb-Os concentrations in this study and measured Os partition coefficients from the literature. These observations indicate that sulfides do not exert a strong control on the fractionation of Pb during mantle melting, but they can be used to constrain mantle Pb isotopic composition. Sulfides in this study, combined with literature data for Pb isotopes in peridotite whole rocks and pyroxene separates, provide evidence for ultra-depleted mantle, as 24% of peridotites are unradiogenic (i.e., 207Pb/204Pb <15.440 and 206Pb/204Pb <17.726), compared to only 3% of ridge basalts. This suggests that the mantle contains volumetrically significant reservoirs of ultra-depleted material, probably derived from recycled oceanic lithospheric mantle. These depleted reservoirs contribute in only small amounts to oceanic crust generation, both due to a limited ability to melt and to the dilution of any melt by more enriched melts during crust formation.

Warren, J. M.; Shirey, S. B.

2012-12-01

215

Young Craters on Smooth Plains  

NASA Technical Reports Server (NTRS)

Young craters (the largest of which is about 100 kilometers in diameter) superposed on smooth plains. Larger young craters have central peaks, flat floors, terraced walls, radial ejecta deposits, and surrounding fields of secondary craters. Smooth plains have well-developed ridges extending NW and NE. This image (FDS 167), acquired during the spacecraft's first encounter with Mercury, is located approximately 60 degrees N, 175 degrees W.

The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

Image Credit: NASA/JPL/Northwestern University

1974-01-01

216

Suspended-sediment and fresh-water discharges in the Ob and Yenisey rivers, 1960-1988  

Microsoft Academic Search

Of the world's great rivers, the Ob and Yenisey rank among the largest suppliers of fresh water and among the smallest suppliers of suspended sediment to the coastal ocean. Sediment in the middle reaches of the rivers is mobilized from bordering terraces and exchanged between channels and flood plains. Sediment in the lower reaches of these great rivers is deposited

R. H. Meade; N. N. Bobrovitskaya; V. I. Babkin

2000-01-01

217

Groundwater in the Great Plains  

E-print Network

7 The importance of conservation 7 What is Groundwater? The Hydrologic Cycle 8 Groundwater flow patterns 9 Saturated and unsaturated zones 9 Aquifers 10 Sole source aquifers 10 Water wells 12 Groundwater Quality Contamination and pollution, measuring... The High Plains Aquifer 22 Population served by groundwater 23 Competing uses for a limited resource 23 Groundwater declines 24 Contamination and Health Issues Water Testing 26 Regulatory Standards, Treatment Options 27 Table of Contents 3 Public...

Jensen, R.

2003-01-01

218

Relationship between the parent material and the soil, in plain and mountainous areas  

NASA Astrophysics Data System (ADS)

One of the most important tasks of the soil is the nutrition of plants. This function is determinated by those parts of the geological media on what is the soil situated and from what the soil was formed (those two can be different). Soil can be formed definitely just from sediment, so it is more proper to speak about parent material than parent rock. Soil forming sediment is defined as the loose sediment on the surface, which is the upper layer of near-surface rocks in flat and hilly regions, and it is the upper layer of the sediment-ensemble situated on the undisturbed bedrock in mountainous areas. Considering its origin, these sediments could be autochthon or allochton. Soil forming is determinated, besides other factors (climate, elevation, vegetation, etc.), by the parent material, which has a crucial influence on the type, quality and fertility of soils through its mineral composition, physical and chemical characteristics. Agrogeological processes happen in the superficial loose sediments in mountainous areas, but the underlying solid rock (where on the surface or close to it, there is solid rock), has an effect on them. The plain and hilly regions covered by thick loose sediment and the areas build up by solid rock and covered with thinner loose sediment in mountainous areas should be searched separately. In plain areas the near-surface formations have to be studied as a whole down to the saturated zone, but at least to 10 m. In regions of mountain and mountain fronts, the thickness, the composition and genetics of the young unconsolidated sediments situated above the older solid rocks have a vital importance, and also the relations among the soils, soil forming sediments and the base rocks have to be understood.

Kerek, Barbara; Kuti, Laszlo; Dobos, Timea; Vatai, Jozsef; Szentpetery, Ildiko

2013-04-01

219

A revision of the bathyal and abyssal necrophage genus Cyclocaris Stebbing, 1888 (Crustacea: Amphipoda: Cyclocaridae) with the addition of two new species from the Atlantic Ocean.  

PubMed

Two new species of the deep-sea scavenging genus Cyclocaris (Crustacea: Amphipoda) are described from bathyal and abyssal depths in the North and tropical Atlantic Ocean, bringing the total number of species in the genus to four. An account of all four species is given and an updated key to the genus Cyclocaris is provided. PMID:24870690

Horton, Tammy; Thurston, Michael H

2014-01-01

220

Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions to Global Heat and Sea Level Rise Budgets*  

E-print Network

Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions of recent warming of these regions in global heat and sea level budgets. The authors 1) compute warming produces a 0.053 (60.017) mm yr21 increase in global average sea level and the deep warming south

Johnson, Gregory C.

221

History of plains resurfacing in the Scandia region of Mars  

USGS Publications Warehouse

We present a preliminary photogeologic map of the Scandia region of Mars with the objective of reconstructing its resurfacing history. The Scandia region includes the lower section of the regional lowland slope of Vastitas Borealis extending about 500–1800 km away from Alba Mons into the Scandia sub-basin below ?4800 m elevation. Twenty mapped geologic units express the diverse stratigraphy of the region. We particularly focus on the materials making up the Vastitas Borealis plains and its Scandia sub-region, where erosional processes have obscured stratigraphic relations and made the reconstruction of the resurfacing history particularly challenging. Geologic mapping implicates the deposition, erosion, and deformation/degradation of geologic units predominantly during Late Hesperian and Early Amazonian time (~3.6–3.3 Ga). During this time, Alba Mons was active, outflow channels were debouching sediments into the northern plains, and basal ice layers of the north polar plateau were accumulating. We identify zones of regional tectonic contraction and extension as well as gradation and mantling. Depressions and scarps within these zones indicate collapse and gradation of Scandia outcrops and surfaces at scales of meters to hundreds of meters. We find that Scandia Tholi display concentric ridges, rugged peaks, irregular depressions, and moats that suggest uplift and tilting of layered plains material by diapirs and extrusion, erosion, and deflation of viscous, sedimentary slurries as previously suggested. These appear to be long-lived features that both pre-date and post-date impact craters. Mesa-forming features may have similar origins and occur along the southern margin of the Scandia region, including near the Phoenix Mars Lander site. Distinctive lobate materials associated with local impact craters suggest impact-induced mobilization of surface materials. We suggest that the formation of the Scandia region features potentially resulted from crustal heating related to Alba Mons volcanism, which acted upon a sequence of lavas, outflow channel sediments, and polar ice deposits centered within the Scandia region. These volatile-enriched sediments may have been in a state of partial volatile melt, resulting in the mobilization of deeply buried ancient materials and their ascent and emergence as sediment and mud breccia diapirs to form tholi features. Similar subsurface instabilities proximal to Alba Mons may have led to surface disruption, as suggested by local and regional scarps, mesas, moats, and knob fields.

Tanaka, Kenneth L.; Fortezzo, Corey M.; Hayward, Rosalyn K.; Rodriguez, J. Alexis P.; Skinner, James A.

2011-01-01

222

Subsurface geology and geothermal prospects in the Nampa-Caldwell area of the western Snake River Plain, Idaho  

Microsoft Academic Search

Subsurface geological and geophysical data show a 2100-m-thick sequence of interbedded basalt and sediment lie beneath the Idaho Group sediments in the Nampa-Caldwell area of the western Snake River Plain. Numerous faults in the subsurface define a central horst that divides the subsurface into separate basins. Overlying the basalt section are widespread sandstone aquifers that can be expected to yeild

S. H. Wood; J. C. Mitchell; J. Anderson

1980-01-01

223

Middle and upper jurassic depositional environments at outer shelf and slope of Baltimore Canyon Trough  

Microsoft Academic Search

New CDP data acquired in the Baltimore Canyon Trough during project LASE made it possible to map a continuous Jurassic sedimentary sequence from the continental margin to the abyssal plain without interruption by basement structures. Intense carbonate sedimentation is inferred at the outer shelf during the Middle and Late Jurassic. Carbonate sedimentation probably started during the Middle Jurassic with a

L. A. Gamboa; P. L. Stoffa; M. Truchan

1985-01-01

224

A qualitative assessment of the influence of bioturbation in Lake Baikal sediments  

NASA Astrophysics Data System (ADS)

The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing, was assessed by studying the actual vertical distribution of benthic animals in continuous accumulation zones selected by seismic survey (Vydrino Shoulder, Posolskoe Bank, Continent Ridge). To assess the influence of the bioturbation, animals were extracted from short cores and identified at the relevant taxonomic level. The faunal distribution is examined in parallel with the bioturbation tracks observed in thin section. Oligochaeta, Nematoda, Ostracoda, Copepoda, Gammaridae, Chironomidae and Hydrachnidia were found inhabiting the sediment. Among them, only oligochaete worms were assumed to have a significant impact on sediment mixing because of their "conveyor belt" feeding. The other two most abundantly sampled groups, nematods and copepods, belong to the interstitial fauna that has no significant impact on the vertical displacement of sediment particles and do not ingest the sediment. The presence of a benthic fauna as deep as 15 cm in the sediment indicates that the possibility of sediment disturbance by invertebrate activity cannot be dismissed in Lake Baikal. The effect of biological mixing is more limited in the deepest stations because the number of potential bioturbators is reduced, qualitatively as well as quantitatively. Located in the abyssal zone, Continent and Vydrino (but outside turbidites) deep stations appear to be most promising sediment records for tracking climate signal at high resolution.

Martin, Patrick; Boes, Xavier; Goddeeris, Boudewijn; Fagel, Nathalie

2005-04-01

225

Lacustrine carbonates of the northern Great Plains of Canada  

NASA Astrophysics Data System (ADS)

The northern Great Plains of western Canada, a vast region stretching from the Precambrian Shield east of Winnipeg, Manitoba, westward for some 1600 km to the foothills of the Rocky Mountains, contains literally millions of lakes and wetlands. Although often characterized as a saline, Na-SO4 system, in fact the wide range of water chemistries exhibited by the lakes results in an unusually large diversity of sediment composition. Despite a long history of limnogeological study, it is only recently that the spectrum of carbonate minerals and sedimentological processes in these lakes has been realized. About 30 species of carbonate minerals have been reported from the modern and Holocene sediment of about 50 basins in the region. The ubiquity of detrital calcite and dolomite is a legacy of the carbonate bedrock and carbonate-rich glacial sediments. Elevated salinities of the lakes, together with high alkalinities, productivity, and pH values, act in concert to create thermodynamically saturated or supersaturated conditions with respect to many carbonate minerals. The most common non-detrital components are Mg-calcite, aragonite and non-stoichiometric dolomite. Many of the basins whose brines have very high Mg/Ca ratios also contain hydromagnesite, magnesite, and nesquehonite. Although not common, sodium carbonates, including trona, natron and nahcolite, also occur in some of the hypersaline lakes. Because of their great range of formative conditions, carbonates have been the workhorse for much of the physical and geochemical paleolimnology in the Canadian Great Plains. However, the often-difficult task of distinguishing endogenic lacustrine carbonates from allogenic and authigenic minerals has limited the use of carbonate stratigraphy in the region. Despite this problem, the carbonates have been useful in deciphering (i) past changes in hydrology and drainage basin characteristics, (ii) lake level and water column stratification fluctuations, and (iii) water chemistry and salinity variations.

Last, Fawn M.; Last, William M.

2012-11-01

226

Petrological, magnetic and chemical properties of basalt dredged from an abyssal hill in the North-east pacific  

USGS Publications Warehouse

OVER the years, samples of basalt from the oceanic crust have been taken mainly from seamounts, fracture zones and ridge and rise crests1-6, and rarely from the vast fields of abyssal hills which cover a large part of the deep-sea floor. The basalt sampled from the deeper regions of the oceanic crust (for example, on fault scarps) is a distinct variety of tholeiitic basalt, while alkali basalt is restricted to the volcanic edifices4. Oceanic tholeiitic basalt differs from alkali basalt and continental tholeiite chiefly in having a relatively low percentage of K2O (0.2 weight per cent)4. Some authors have speculated that this type of tholeiitic basalt is the major extrusion from the upper mantle and constitutes the predominant rock type in the upper oceanic crust. ?? 1969 Nature Publishing Group.

Luyendyk, B. P.; Engel, C. G.

1969-01-01

227

Planetary stations and Abyssal Benthic Laboratories: An overview of parallel approaches for long-term investigation in extreme environments  

NASA Technical Reports Server (NTRS)

In spite of the apparent great differences between deep ocean and space environment, significant similarities can be recognized when considering the possible solutions and technologies enabling the development of remote automatic stations supporting the execution of scientific activities. In this sense it is believed that mutual benefits shall be derived from the exchange of experiences and results between people and organizations involved in research and engineering activities for hostile environments, such as space, deep sea, and polar areas. A significant example of possible technology transfer and common systematic approach is given, which describes in some detail how the solutions and the enabling technologies identified for an Abyssal Benthic Laboratory can be applied for the case of a lunar or planetary station.

Dipippo, S.; Prendin, W.; Gasparoni, F.

1994-01-01

228

Lunar Smooth Plains Identification and Classification  

NASA Astrophysics Data System (ADS)

Smooth plains are widespread on the Moon and have diverse origins. The maria comprise the majority of the smooth plains and are volcanic in origin. Highland smooth plains are patchy, and tend to fill large craters and basins; their origins have eluded unambiguous classification. Prior to the Apollo 16 mission, many workers thought that highland plains were volcanic, possibly more silicic than the maria. However, as the Apollo 16 samples are mostly impact breccias, the highland smooth plains were re-interpreted basin impact ejecta, most likely from the Imbrium and possibly Orientale basins. Conversely, some known non-mare volcanic units, such as the Apennine Bench Formation, contain light plains. These interpretations do not rule out alternate origins for a subset of highland smooth plains, including impact melt or volcanic origins (effusive or pyroclastic). We developed an algorithm to identify smooth plains using topographic parameters from the WAC Global Lunar Digital Terrain Model (DTM) (GLD100), sampled at 333 m/pixel. We classify the smooth plains using the Clementine UVVIS FeO map and photometrically corrected Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) images. Terrain with slopes less than 2° (1 km baseline) and standard deviation of slope less than 0.75° (1 km x 1 km box, n=9) are defined as smooth plains. Highland smooth plains are distinguished from basaltic smooth plains using the following criteria: LROC WAC 643 nm normalized reflectance > 0.056, LROC WAC 321 nm / 415 nm ratio < 0.74, and Clementine FeO < 12 wt.% (excluding Clementine non-coverage areas). The remaining smooth plains are classified as maria and are subdivided into two classes: LROC WAC 321 nm / 415 nm ratio > 0.77 is termed blue maria and a ratio ? 0.77 is termed red maria. The automatic classification was limited to the 87% of the Moon covered by photometrically normalized WAC data (60°S to 60°N). The differences between the maria and highland smooth plains deposits were more ambiguous in regions where the Clementine data had gores and albedo of the maria was elevated (i.e. Mare Frigoris and eastern Imbrium basin). For example, Schickard crater hosts a mare deposit that was covered by Orientale basin ejecta. However the cryptomare in Schickard crater were successfully classified and cratering after basin ejecta emplacement can be seen to have excavated the mare material. Known impact melt deposits, such as the melt pool adjacent to King crater, are resolved as highlands smooth plains. Classified Smooth Plains Distribution;

Boyd, A. K.; Robinson, M. S.; Mahanti, P.; Lawrence, S. J.; Spudis, P.; Jolliff, B. L.

2012-12-01

229

Wet coastal plain tundra III  

SciTech Connect

This year's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSE of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 38'W; Barrow Quadrangle, USGS reflect a decrease in the total number of species breeding. However, total breeding density rose by 82%. Lapland Longspurs (up 105%) accounted for half of this increase while the rest was spread among many species. There was a total of 8 species; 40.5 territorial males or females (162/km/sup 2/, 66/100 acres).

Myers, J.P.; Gellman, S.T.; Pitelka, F.A.

1980-01-01

230

Coastal morphodynamics and Chenier-Plain evolution in southwestern Louisiana, USA: A geomorphic model  

NASA Astrophysics Data System (ADS)

Using 28 topographic profiles, air-photo interpretation, and historical shoreline-change data, coastal processes were evaluated along the Chenier Plain to explain the occurrence, distribution, and geomorphic hierarchy of primary landforms, and existing hypotheses regarding Chenier-Plain evolution were reconsidered. The Chenier Plain of SW Louisiana, classified as a low-profile, microtidal, storm-dominated coast, is located west and downdrift of the Mississippi River deltaic plain. This Late-Holocene, marginal-deltaic environment is 200 km long and up to 30 km wide, and is composed primarily of mud deposits capped by marsh interspersed with thin sand- and shell-rich ridges ("cheniers") that have elevations of up to 4 m. In this study, the term "ridge" is used as a morphologic term for a narrow, linear or curvilinear topographic high that consists of sand and shelly material accumulated by waves and other physical coastal processes. Thus, most ridges in the Chenier Plain represent relict open-Gulf shorelines. On the basis of past movement trends of individual shorelines, ridges may be further classified as transgressive, regressive, or laterally accreted. Geomorphic zones that contain two or more regressive, transgressive, or laterally accreted ridges are termed complexes. Consequently, we further refine the Chenier-Plain definition by Otvos and Price [Otvos, E.G. and Price, W.A., 1979. Problems of chenier genesis and terminology—an overview. Marine Geology, 31: 251-263] and define Chenier Plain as containing at least two or more chenier complexes. Based on these definitions, a geomorphic hierarchy of landforms was refined relative to dominant process for the Louisiana Chenier Plain. The Chenier Plain is defined as a first-order feature (5000 km 2) composed of three second-order features (30 to 300 km 2): chenier complex, beach-ridge complex, and spit complex. Individual ridges of each complex type were further separated into third-order features: chenier, beach ridge, and spit. To understand the long-term evolution of a coastal depositional system, primary process-response mechanisms and patterns found along the modern Chenier-Plain coast were first identified, especially tidal-inlet processes associated with the Sabine, Calcasieu, and Mermentau Rivers. Tidal prism ( ?) and quantity of littoral transport ( Mtotal) are the most important factors controlling inlet stability. Greater discharge and/or tidal prism increase the ability of river and estuarine systems to interrupt longshore sediment transport, maintain and naturally stabilize tidal entrances, and promote updrift deposition. Thus, prior to human modification and stabilization efforts, the Mermentau River entrance would be classified as wave-dominated, Sabine Pass as tide-dominated, and Calcasieu Pass as tide-dominated to occasionally mixed. Hoyt [Hoyt, J.H., 1969. Chenier versus barrier, genetic and stratigraphic distinction. Am. Assoc. Petrol. Geol. Bull., 53: 299-306] presented the first detailed depositional model for chenier genesis and mudflat progradation, which he attributed to changes in Mississippi River flow direction (i.e., delta switching) caused by upstream channel avulsion. However, Hoyt's model oversimplifies Chenier-Plain evolution because it omits ridges created by other means. Thus, the geologic evolution of the Chenier Plain is more complicated than channel avulsions of the Mississippi River, and it involved not only chenier ridges (i.e., transgressive), but also ridges that are genetically tied to regression (beach ridges) and lateral accretion (recurved spits). A six-stage geomorphic process-response model was developed to describe Chenier-Plain evolution primarily as a function of: (i) the balance between sediment supply and energy dissipation associated with Mississippi River channel avulsions, (ii) local sediment reworking and lateral transport, (iii) tidal-entrance dynamics, and (iv) possibly higher-than-present stands of Holocene sea level. Consequently, the geneses of three different ridge types (transgressive, reg

McBride, Randolph A.; Taylor, Matthew J.; Byrnes, Mark R.

2007-08-01

231

Reservoir sedimentation  

SciTech Connect

Research on reservoir sedimentation in recent years has been aimed mainly at water resources projects in developing countries. These countries, especially in Africa, often have to cope with long droughts, flash floods and severe erosion problems. Large reservoir capacities are required to capture water provided by flash floods so as to ensure the supply of water in periods of drought. The problem arising however is that these floods, due to their tremendous stream power, carry enormous volumes of sediment which, due to the size of reservoirs, are virtually deposited into the reservoir basin, leading to fast deterioration of a costly investment. Accurate forecasting of reservoir behaviour is therefore of the utmost importance. The point of view in this book is that of the water resources engineer who predicts the effect of sediment deposition on a reservoir and its immediate environment. Practical procedures to estimate sediment yield, calculate sediment profiles and assess the influence sediment retention has on the river downstream of a reservoir are presented. Preventative measures are also discussed. The approach adopted in this book is through illustrating theory with examples. The recent theory presented regards processes involved in the deposition of sediment in reservoirs.

Annandale, G.W.

1987-01-01

232

Late Quaternary (Weichselian) alluvial history and neotectonic control on fluvial landscape development in the southern Körös plain, Hungary  

Microsoft Academic Search

Four drill cores and a clay pit section have been examined in the southern part of the Körös plain to understand the history and controls on alluvial sedimentation for the last ~40ka. Four facies groups were identified, such as channel, channel margin, floodplain and floodbasin with seven distinctive facies. Magnetic susceptibility and mineralogy have further characterized the sedimentary facies indicating

Annamária Nádor; Rajiv Sinha; Árpád Magyari; Sampat K. Tandon; Zsófia Medzihradszky; Zoltán Unger; Ashish Singh

2011-01-01

233

Seismic expression and geological significane of a lacustrine delta in neogene deposits of the western Snake River Plain, Idaho  

Microsoft Academic Search

Lacustrine deposits in rift basin environments and groundwater resources in lacustrine sediments have become major petroleum targets and methods are needed to identify facies of permeable strata within thick sections of impermeable mud rocks characteristic of these deposits. High-resolution seismic reflection profiles and well data from the western Snake River plain basin are used to identify a buried lacustrine delta

Wood

1994-01-01

234

Disequilibria in the uranium decay series in sedimentary deposits at Allen's cave, nullarbor plain, Australia: Implications for dose rate determinations  

Microsoft Academic Search

Disequilibrium in the uranium decay series can cause a time-dependent variation in the radiation dose received by deposited sediments. In luminescence and ESR dating studies, the observation of disequilibrium usually requires modelling of the variation in dose rate as a function of burial time. In this paper, we report on radionuclide data collected from Allen's Cave on the Nullarbor Plain,

Jon M. Olley; Richard G. Roberts; Andrew S. Murray

1997-01-01

235

Sources of recently deposited sediments in playa wetlands  

Microsoft Academic Search

There are more than 20,000 playa wetlands in the Southern High Plains of Texas and New Mexico. Playas with cropland watersheds\\u000a have lost most of their basin volume due to sedimentation, and they have lost more volume than playas with rangeland watersheds.\\u000a To determine the source (wind vs. water transport) of sedimentation in playas and develop management recommendations to lessen

Hong-Ren Luo; Loren M. Smith; David A. Haukos; B. L. Allen

1999-01-01

236

Rates of Microbial Metabolism in Deep Coastal Plain Aquifers  

PubMed Central

Rates of microbial metabolism in deep anaerobic aquifers of the Atlantic coastal plain of South Carolina were investigated by both microbiological and geochemical techniques. Rates of [2-14C]acetate and [U-14C]glucose oxidation as well as geochemical evidence indicated that metabolic rates were faster in the sandy sediments composing the aquifers than in the clayey sediments of the confining layers. In the sandy aquifer sediments, estimates of the rates of CO2 production (millimoles of CO2 per liter per year) based on the oxidation of [2-14C] acetate were 9.4 × 10?3 to 2.4 × 10?1 for the Black Creek aquifer, 1.1 × 10?2 for the Middendorf aquifer, and <7 × 10?5 for the Cape Fear aquifer. These estimates were at least 2 orders of magnitude lower than previously published estimates that were based on the accumulation of CO2 in laboratory incubations of similar deep subsurface sediments. In contrast, geochemical modeling of groundwater chemistry changes along aquifer flowpaths gave rate estimates that ranged from 10?4 to 10?6 mmol of CO2 per liter per year. The age of these sediments (ca. 80 million years) and their organic carbon content suggest that average rates of CO2 production could have been no more than 10?4 mmol per liter per year. Thus, laboratory incubations may greatly overestimate the in situ rates of microbial metabolism in deep subsurface environments. This has important implications for the use of laboratory incubations in attempts to estimate biorestoration capacities of deep aquifers. The rate estimates from geochemical modeling indicate that deep aquifers are among the most oligotrophic aquatic environments in which there is ongoing microbial metabolism. PMID:16348227

Chapelle, Francis H.; Lovley, Derek R.

1990-01-01

237

Correlation of Miocene sequences and hydrogeologic units, New Jersey Coastal Plain  

Microsoft Academic Search

We have developed a Miocene sequence stratigraphic framework using data from recently drilled boreholes in the New Jersey Coastal Plain. Sequences are shallowing upward, unconformity-bounded units; fine-grained shelf and prodelta sediments grade upward to delta front and shallow-marine sands, corresponding to confining bed—aquifer couplets. By dating Miocene sequences using Sr-isotope stratigraphy, and mapping with borehole data and geophysical logs, we

Peter J. Sugarman; Kenneth G. Miller

1997-01-01

238

Climatic Variations in the East European Plain During the Last Millennium: State of the Art  

Microsoft Academic Search

\\u000a High resolution last millennium reconstructions of annual, summer, winter temperature and sum of annual precipitation for\\u000a the East European Plain based on the historical data, palynology, tree-ring analyses, borehole temperature measurements and\\u000a lake sediments are discussed. The first multiproxy quantitative reconstruction of these parameters takes into account mostly\\u000a historical and palynological records of suffice length and quality. It shows the

Vladimir Klimenko; Olga Solomina

239

Carrisa Plains PV power plant performance  

Microsoft Academic Search

The authors summarize the performance of the world's largest PV (photovoltaic) power plant (the one at Carrisa Plains, California) for 1984-1989. Although the plant has high availability, energy production efficiency has declined at the rate of 8-12% per year since 1986. Based on the data, it is difficult to provide a thorough explanation for the steady decline in Carrisa Plains

Howard J. Wenger; Christina Jennings; J. J. Iannucci

1990-01-01

240

Ohio Conservation Plan: Plains gartersnake, Thamnophis radix  

Microsoft Academic Search

This plan outlines strategies and methods used in an ongoing study initiated in 1999 to restore a selfsustaining population of the Plains gartersnake (Thamnophis radix) in Ohio. Restoring a self-sustaining population would require increases in the current population to where the ratios of T. radix to T. sirtalis are approximately 1:1 in multiple locations in Killdeer Plains Wildlife Area (KPWA).

Norman Reichenbach; M. Barrie; K. Becka; G. Burghardt; S. Butterworth; C. Caldwell; F. Dierkes; P. Johantgen; K. Stanford; D. Wynn

2010-01-01

241

Texas South Plains Spring-Planted Oats  

E-print Network

Texas South Plains Spring-Planted Oats Suggestions for Late-Season Small Forage Production When.746.6101, ctrostle@ag.tamu.edu #12;Past Several Years Oats planted in late winter for "catch up" small grains forage expected Up to 50,000 acres per year in TX High Plains Oat forage yields look very good, but seldom grazed

Mukhtar, Saqib

242

A model of early diagenetic processes from the shelf to abyssal depths  

NASA Astrophysics Data System (ADS)

We present a numerical model of sedimentary early diagenetic processes that includes oxic and anoxic mineralization. The model belongs to the new wave of early diagenesis models that account for depth-dependent bioturbation and porosity profiles; it can be used both for calculating steady-state conditions and transient simulation. It was developed to reproduce the cycling of carbon, oxygen, and nitrogen along the ocean margin; it resolves the sediment-depth profiles of carbon, oxygen, nitrate, ammonium, and other reduced substances. Organic carbon is modeled as two degradable fractions with different first-order degradation rates and nitrogen:carbon ratios, to account for the decreasing reactivity and N/C ratio of the organic matter with depth into the sediment. The consumption of oxygen and nitrate as terminal electron acceptors is explicitly modeled, and mineralization is limited both by carbon (first order kinetics) and by oxidant availability (Michaelis-Menten type kinetics). Nitrification and oxic mineralization are decoupled, which allows the description of ammonium profiles. Mineralization processes using other oxidants (manganese oxides, iron oxides, sulphate) are lumped into one process, where degradation is only carbon limited; the terminal electron acceptors are not explicitly modeled, only the production of reduced substances is described. These substances are in part permanently removed (e.g., pyrite formation below the bioturbation zone) and partly diffuse towards the oxic layer where they react with oxygen. The values of several parameters were constrained using literature-derived relationships. The model was calibrated on a dataset obtained from the literature, which relates the magnitude of the different pathways to total organic carbon mineralization. The influence of carbon flux, bioturbation, sedimentation rate, bottomwater concentrations of oxygen, and nitrate and carbon degradability on the different mineralization pathways is examined. The relative contribution of the oxic mineralization in the model is significantly depressed under high organic flux, under low bottomwater oxygen conditions and when the bioturbation increases; higher carbon degradability has only a small positive effect, while sedimentation rate is relatively unimportant. Denitrification is mainly influenced by the nitrate concentration in the overlying bottomwater.

Soetaert, Karline; Herman, Peter M. J.; Middelburg, Jack J.

1996-03-01

243

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

2005-01-01

244

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains Co{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) activities have focused on developing information on deployment issues to support Task 5 activities by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) activities have focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) has included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 (Modeling and Phase II Action Plans) activities have focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman

2004-07-01

245

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

2004-10-01

246

Oxygen thermobarometry of abyssal spinel peridotites: The redox state and C-O-H volatile composition of the Earth's sub-oceanic upper mantle  

Microsoft Academic Search

The authors have applied the spinel peridotite oxygen barometer to abyssal spinel peridotites from the mid-Atlantic, central Indian, southwest Indian and American-Antarctic ocean ridge systems. The results indicate that the oxygen fugacity (F{sub Oâ}) of the suboceanic mantle is on average 0.9 {plus minus}0.7 (n = 33; {plus minus} 1sd) log units below the Fayalite-Magnetite-Quartz (FMQ) f{sub Oâ} buffer, in

L. T. Bryndzia; B. J. Wood

1990-01-01

247

Flood Plain Lakes Along the Elbe River - a Forgotten Risk  

NASA Astrophysics Data System (ADS)

Flood Plain Lakes Along the Elbe River - a Forgotten Risk Introduction: Along the German part of the Elbe River, more than 1000 "side structures" form potential sinks of contaminated sediment. They are mostly remains of previous river courses which have been cut off by natural causes or anthropogenic alterations of the river (oxbow lakes), or are floodplain lakes that were formed during high water conditions. These water bodies sometimes have a small opening towards the Elbe, or are hydrodynamically connected only in situations of high discharges. High discharges in the Elbe River, however, are mainly responsible for transporting historic contaminants along with suspended matter from former historic sources in the middle Elbe downstream. As these may settle when the current dies down at the end of a high discharge period, side structures have been under suspicion to have accumulated contaminated material over the last decades. Until this study was conducted, nothing was known about erodibility and contamination of sediment in these lakes even though they could have a large impact on the Elbe River itself: A preliminary investigation showed that the total surface of side structures in the Elbe floodplain adds up to about 50 km2. In case that deposited sediment is contaminated and only the upper 20 cm are prone to resuspension and transport during flooding, 10 Mio m3 of contaminated sediment could potentially be added to the contaminant load during a high water event. This study was carried out to evaluate the risk from these side structures for the environmental quality of the Elbe River. Methods: 15 side structures were investigated. Sediment cores were taken on 1 to 3 locations per water body in order to obtain the following information: • Depth of sediment layer • Erodibility of surface sediment, measured immediately after sampling - using the "Gust Microcosm", • Eroded mass at over-critical shear stress, measured in the lab by eroding a sediment core for one hour and collecting the suspended sediment matter. • Chemical contamination • Ecotoxicological effects Results and Discussion All side structures that were sampled exceeded the national quality guidelines for sediments which have been set by the International Commission for the Protection of the Elbe. In some cases very high concentrations were reached such as 1300 µg/kg dw for p,p-DDD, up to 61 mg/kg for Hg and 39 mg/kg for Cd. Erodibility varied a lot with critical shear stresses of less than 1 cm/s to more than 2 cm/s. Ecotoxicological data were also very different between side structures and sampling locations, but partly indicating very high inhibitions. Methanol extracts of sediments on all locations were screened using the luminescence bacteria test with Vibrio fischeri. Selected sediemt samples were tested applying the sediment contact test with Arthrobacter globiformes and the algae growth inhibition test with Pseudokirchneriella subcapitata. An integrated evaluation of all information led to a classification of 7 sites out of 15 to be of high risk, 7 to be of medium risk and only one site to be of low risk for the environmental quality of the Elbe River.

Heise, Susanne

2014-05-01

248

High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth  

NASA Astrophysics Data System (ADS)

Microbes control the decomposition of organic matter inmarine sediments. Decomposition, in turn, contributes to oceanic nutrient regeneration and influences the preservation of organic carbon. Generally, rates of benthic decomposition decline with increasing water depth, although given the vast extent of the abyss, deep-sea sediments are quantitatively important for the global carbon cycle. However, the deepest regions of the ocean have remained virtually unexplored. Here, we present observations of microbial activity in sediments at Challenger Deep in the Mariana Trench in the central west Pacific, which at almost 11,000m depth represents the deepest oceanic site on Earth. We used an autonomous micro-profiling system to assess benthic oxygen consumption rates. We show that although the presence of macrofauna is restricted at Challenger Deep, rates of biological consumption of oxygen are high, exceeding rates at a nearby 6,000-m-deep site by a factor of two. Consistently, analyses of sediments collected from the two sites reveal higher concentrations of microbial cells at Challenger Deep. Furthermore, analyses of sediment 210Pb profiles reveal relatively high sediment deposition in the trench. We conclude that the elevated deposition of organic matter at Challenger Deep maintains intensified microbial activity at the extreme pressures that characterize this environment.

Glud, Ronnie N.; Wenzhöfer, Frank; Middelboe, Mathias; Oguri, Kazumasa; Turnewitsch, Robert; Canfield, Donald E.; Kitazato, Hiroshi

2013-04-01

249

CORN BELT PLAIN RIVER AND STREAMS PROJECT - 3 BIOCRITERIA PRODUCTS  

EPA Science Inventory

This effort resulted in eight products, as follows: 1) Development of Index of Biotic Integrity Expectations for the Ecoregions of Indiana I. Central Corn Belt Plain; 2) Ibid. II. Huron-Erie Lake Plain; 3) Ibid III. Northern Indiana Till Plain; 4) Ibid .IV.Eastern Corn Belt Plain...

250

Flood information for flood-plain planning  

USGS Publications Warehouse

Floods are natural and normal phenomena. They are catastrophic simply because man occupies the flood plain, the highwater channel of a river. Man occupies flood plains because it is convenient and profitable to do so, but he must purchase his occupancy at a price-either sustain flood damage, or provide flood-control facilities. Although large sums of money have been, and are being, spent for flood control, flood damage continues to mount. However, neither complete flood control nor abandonment of the flood plain is practicable. Flood plains are a valuable resource and will continue to be occupied, but the nature and degree of occupancy should be compatible with the risk involved and with the degree of protection that is practicable to provide. It is primarily to meet the needs for defining the risk that the flood-inundation maps of the U.S. Geological Survey are prepared.

Bue, Conrad D.

1967-01-01

251

Targeting the Plains of Venus from Orbit  

NASA Astrophysics Data System (ADS)

Lowland plains house a spectacular array of poorly understood volcanic, tectonic, and impact features that are key to settling the continuing global stratigraphy debate and resolving how the only other accessible Earth-sized planet has evolved.

Sharpton, V. L.

2014-05-01

252

Plain Language Thesauruses | accrualnet.cancer.gov  

Cancer.gov

These resources offer plain language equivalents to medical terms, phrases, and references frequently used in clinical trials. They are helpful when developing informed consent forms and other patient information text.

253

Hidden in Plain Sight: Girls and ADHD  

MedlinePLUS

... Issues Listen Hidden in Plain Sight: Girls and ADHD Article Body Scotty’s parents and teachers could see ... to adopt authoritarian discipline styles Help for Your ADHD Daughter For parents, it is important not to ...

254

Acidalia and Chryse Plains, Mars  

NASA Technical Reports Server (NTRS)

Somewhere down there sits the Mars Pathfinder lander and Sojourner rover. This Mars Global Surveyor Mars Orbiter Camera view of the red planet shows the region that includes Ares Vallis and the Chryse Plains upon which both Mars Pathfinder and the Viking 1 landed in 1997 and 1976, respectively. Acidalia Planitia is the dark surface that dominates the center left. The Pathfinder site is immediately south of Acidalia, just left of center in this view. Also shown--the north polar cap is at the top, and Arabia Terra and Sinus Meridiani are to the right. The bluish-white features are clouds. This is a color composite of 9 red and 9 blue image strips taken by the Mars Global Surveyor Mars Orbiter Camera on 9 successive orbits from pole-to-pole during the calibration phase of the mission in March 1999. The color is computer-enhanced and is not shown as it would actually appear to the human eye.

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

1999-01-01

255

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership characterization work is nearing completion, and most remaining efforts are related to finalizing work products. Task 2 (Technology Deployment) has developed a Topical Report entitled ''Deployment Issues Related to Geologic CO{sub 2} Sequestration in the PCOR Partnership Region''. Task 3 (Public Outreach) has developed an informational Public Television program entitled ''Nature in the Balance'', about CO{sub 2} sequestration. The program was completed and aired on Prairie Public Television in this quarter. Task 4 (Sources, Sinks, and Infrastructure) efforts are nearing completion, and data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation are being incorporated into a series of topical reports. The expansion of the Decision Support System Geographic Information System database has continued with the development of a ''save bookmark'' feature that allows users to save a map from the system easily. A feature that allows users to develop a report that summarizes CO{sub 2} sequestration parameters was also developed. Task 5 (Modeling and Phase II Action Plans) focused on screening and qualitatively assessing sequestration options and developing economic estimates for important regional CO{sub 2} sequestration strategies.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Lisa S. Botnen

2005-07-01

256

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) and provided information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 2 efforts also included preparation of a draft topical report entitled ''Deployment Issues Related to Geologic CO{sub 2} Sequestration in the PCOR Partnership Region'', which is nearing completion. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. The video will be completed and aired on Prairie Public Television in the next quarter. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. The addition of the Canadian province of Alberta to the PCOR Partnership region expanded the decision support system (DSS) geographic information system database. Task 5 screened and qualitatively assessed sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

2005-04-01

257

Mapping Titan’s Undifferentiated Plains (“Blandlands”) to infer their origin  

NASA Astrophysics Data System (ADS)

The undifferentiated plains first mapped by Lopes et al. (2010, Icarus, 205) are vast expanses of terrains that appear bland in Cassini RADAR Synthetic Aperture Radar images, hence the designation “blandlands”. While the interpretation of several other geologic units on Titan, such as dunes and well-preserved impact craters, has been relatively straightforward, the origin of the “blandlands” has remained mysterious. SAR images show that the “blandlands” are mostly found at mid-latitudes and appear relatively featureless at radar wavelengths, with no significant topographic variations. Their gradational boundaries and paucity of features in SAR data make geologic interpretation particularly challenging. We have mapped the distribution of these terrains using SAR swaths up to T92 (July 2013), which cover > 50% of Titan’s surface. We compared SAR images with their de-noised counterparts, the topography using the SARTopo method (Stiles et al., 2009, Icarus 202) and, where possible, the response from radiometry. We examined and evaluated different formation mechanisms. Plains may be sedimentary in origin, resulting from fluvial or lacustrine deposition or accumulation of photolysis products created in the upper atmosphere. Alternatively, the plains may be cryovolcanic, consisting of overlapping flows of low relief, obscured by accumulation of sediments. In this paper, we use SAR, radiometry, and SARTopo data to examine the characteristics of the plains and compare them with other geologic units. The results from our analysis suggest that the sedimentary origin is the most likely, and that plain materials are similar or the same as dune materials. Plains occur mostly at mid-latitudes, while dunes occur mostly at low latitudes. This may be a result of wind patterns, decrease in sand supply, or changes in properties of sand, perhaps moisture content, all of which would inhibit the formation of large dunes.

Lopes, Rosaly M.; Malaska, Michael J.; Schoenfeld, Ashley M.; LeGall, Alice; Hayes, Alexander G.; Birch, Samuel P.; Solomonidou, Anezina

2014-11-01

258

Sediment fingerprinting to determine the source of suspended sediment in a southern Piedmont stream.  

PubMed

Thousands of stream miles in the southern Piedmont region are impaired because of high levels of suspended sediment. It is unclear if the source is upland erosion from agricultural sources or bank erosion of historic sediment deposited in the flood plains between 1830 and 1930 when cotton farming was extensive. The objective of this study was to determine the source of high stream suspended sediment concentrations in a typical southern Piedmont watershed using sediment fingerprinting techniques. Twenty-one potential tracers were tested for their ability to discriminate between sources, conservative behavior, and lack of redundancy. Tracer concentrations were determined in potential sediment sources (forests, pastures, row crop fields, stream banks, and unpaved roads and construction sites), and suspended sediment samples collected from the stream and analyzed using mixing models. Results indicated that 137Cs and 15N were the best tracers to discriminate potential sediment sources in this watershed. The delta15N values showed distinct signatures in all the potential suspended sediment sources, and delta15N was a unique tracer to differentiate stream bank soil from upland subsurface soils, such as soil from construction sites, unpaved roads, ditches, and field gullies. Mixing models showed that about 60% of the stream suspended sediment originated from eroding stream banks, 23 to 30% from upland subsoil sources (e.g., construction sites and unpaved roads), and about 10 to 15% from pastures. The results may be applicable to other watersheds in the Piedmont depending on the extent of urbanization occurring in these watersheds. Better understanding of the sources of fine sediment has practical implications on the type of sediment control measures to be adopted. Investment of resources in improving water quality should consider the factors causing stream bank erosion and erosion from unpaved roads and construction sites to water quality impairment. PMID:20830921

Mukundan, R; Radcliffe, D E; Ritchie, J C; Risse, L M; McKinley, R A

2010-01-01

259

Observations of polarized seismoacoustic T waves at and beneath the seafloor in the abyssal Pacific ocean.  

PubMed

Combined seismic and hydrophone observations show that the traditional T wave propagates as a seismoacoustic polarized interface wave (Ti) coupled to the seafloor. Seismoacoustic Ti waves propagating at the sound speed of water are routinely observed over megameter distances at the deep (4979 m) seafloor Hawaii-2 Observatory (H2O) between Hawaii and California, even though the seafloor site is within a shadow zone for acoustic wave propagation. Ti has also been observed on seismometers 225 km SSW of Oahu at the OSN1 site at the seafloor and within an ODP borehole into the basalt basement. Analyses of timing, apparent velocity, energy, and polarization of these interface waves are presented. At low frequency (< approximately 5 Hz) Ti propagates dominantly in the sediments and is consistent with higher-mode Rayleigh waves. At higher frequencies the observed Ti waves dominantly propagate acoustically with characteristics suggesting local scattering. The observation of Ti from an earthquake in Guatemala at OSN1, whose path is blocked by the Island of Hawaii, is consistent with scattering from the vicinity of the Cross Seamount. PMID:17225389

Butler, Rhett

2006-12-01

260

Sedimentation and depositional environments of the Barremian-Cenomanian Debre Libanose Sandstone, Blue Nile (Abay) Basin, Ethiopia  

Microsoft Academic Search

Exploration of oil and gas deposits in the Blue Nile Basin targeted the Debre Libanose Sandstone as a reservoir objective. The unit was deposited in broad alluvial plains, and shows some elements of the Platte type braided river sedimentation in the lower and middle succession. The braided river sedimentation is dominated by single storey and multistorey amalgamated sandstone bodies, and

A. Wolela

2009-01-01

261

Age determinations and Earth-based multispectral observations of lunar light plains  

NASA Technical Reports Server (NTRS)

The history of light plains still remains doubtful, but there are good arguments - mainly obtained by age determinations and supported by multispectral observations - for an endogenic (magmatic) instead of an (exclusively) impact related origin. Light plains are characterized by smooth areas with an albedo lower than the surrounding highlands (12 - 13 percent), but significantly higher than maria (5 - 6 percent). Before Apollo 16 a volcanic source has been supposed, but analysis of returned samples (highly brecciated and metamorphosed rocks) favored an impact ejecta related origin. Among the currently discussed models are formation by ejecta sedimentation from multi-ringed basins, formation by secondary and tertiary cratering action of ballistically ejected material during the formation of multi-ringed basins, in situ formation by impact melt of large events, and premare (crypto-) volcanism basalts covered by a thin ejecta cover; younger impacts penetrated the ejecta surface to create the dark haloed craters. To find arguments in favor or against these ideas the chronology of light plains is of major importance. Obviously a genetic relationship between the evolution of light plains and the basin forming impacts can be possible only if the events of emplacement features happened simultaneously.

Koehler, U.; Jaumann, R.; Neukum, G.

1993-01-01

262

Light Plains in the South-Pole Aitken Basin: Surface Ages and Mineralogical Composition  

NASA Astrophysics Data System (ADS)

We studied light plains in the north-eastern South-Pole Aitken basin to investigate their origin, ages, and mineralogical composition. Light plains, also known as the Cayley Formation, occur on the near- and farside of the Moon. Due to their smooth texture, lower crater densities, and occurrence as crater fills, they were thought to be of volcanic origin [e.g., 1]. However, Apollo 16 samples of light plains deposits were in fact highly brecciated rocks [2]. Therefore, the Imbrium and Orientale impacts were thought to have formed light plains because they reshaped the surface thousands of kilometers from their impact sites. Subsequent studies revealed varying surface ages of light plains [e.g., 3] and different mineralogical compositions, which are in some cases more highland-like and in others more mare-like. Hence, an origin solely from the Imbrium and/or Orientale impacts is unlikely. Thus, the question whether light plains formed due to large impacts or regional cratering, or through endogenic processes remains open. We performed crater size-frequency measurements [e.g., 4] on Lunar Reconnaissance Orbiter Wide Angle Camera images and obtained absolute model ages between 3.43 and 3.81 Ga. We observed neither a distinctive peak of light plains ages nor clustering of similar ages in any specific regions of the studied area. Due to the fact that the derived ages vary as much as 380 Ma, an origin by a single event seems unlikely. Moreover, some ages even post-date the Imbrium and Orientale impacts, and thus an origin related to those impacts is not likely. Examination of multispectral data from Clementine [5] shows that the Ti abundances vary between 0.2 and 3 wt % and Fe abundances between 12.5 and 19 wt %. We observed a regional difference in distribution: light plains units within the Apollo basin have lower Fe and Ti values and are more highland-like, whereas light plains outside the Apollo basin show higher Fe and Ti values and are more mare-like. Furthermore, M3 spectra from small impact craters on light plains show characteristic absorption bands for pyroxene. We conclude that light plains are unlikely to have formed by the Imbrium and Orientale impacts due to the range of surface ages and the compositional differences. Nevertheless, these impacts together with secondary cratering and sedimentation from regional and local impacts may have played an important role in forming these plains. An endogenic origin can still not be excluded due to the mare-like composition of some light plains. [1] Wilhelms D.E. (1970) Astrogeol. Stud. Ann. Prog. Report, 13-28. [2] Young J.W. (1972) NASA Apollo 16 Prelim. Sci. Rep., 5-1-5-6. [3] Neukum, G. (1977) The Moon 17, 383-393. [4] Neukum G. et al. (1975) The Moon 12, 201-229. [5] Lucey P.G. et al. (2000) J. Geophys. Res. 105, 20,297-20,305.

Thiessen, F.; Hiesinger, H.; van der Bogert, C. H.; Pasckert, J. H.; Robinson, M. S.

2012-04-01

263

Effects of Late Cretaceous and Cenozoic faulting on the geology and hydrology of the coastal plain near the Savannah River, Georgia and South Carolina  

USGS Publications Warehouse

Geologic and hydrologic investigations by the U.S. Geological Survey have defined stratigraphic and hydraulic anomalies suggestive of faulting within Coastal Plain sediments between the Ogeechee River in east-central Georgia and the Edisto River in west-central South Carolina. Examination of borehole cuttings, cores, and geophysical logs from test wells indicate that Triassic rocks and Upper Cretaceous and lower Tertiary Coastal Plain sediments near the Barnwell-Allendale County line near Millett, South Carolina, are offset by a northeast-trending fault downthrown to the northwest. The location of this suspected Coastal Plain fault generally coincides with the location of an inferred fault in basement rocks as interpreted from aeromagnetic surveys. Apparent vertical offsets range from about 700 feet at the base of Upper Cretaceous sediments to about 20 feet in strata of Late Eocene age. As a result, the Upper Cretaceous Middendorf Formation which directly overlies crystalline and Triassic rocks updip (northwest) of this fault, is absent immediately downdip of the fault. The thickness of Tipper Cretaceous sediments is also sharply reduced from about 700 feet to about 180 feet across the fault. Sediments of the basal Coastal Plain aquifer are largely truncated by uplifted Triassic rocks at the fault near Millett, South Carolina. Lateral ground-water flow near the Savannah River Is consequently disrupted updip of the fault and ground water is transferred vertically into overlying sediments and possibly into the Savannah River. At several locations, abrupt changes in potentiometric head occur across this fault. Computed transmissivity of the basal Coastal Plain aquifer is also radically reduced downdip of the fault, sharply reversing a downdip trend of rapidly increasing aquifer transmissivity. Other anomalous potentiometric data along a northeast-trending line between Statesboro, Georgia, and Fairfax, South Carolina, suggest the possibility of similar faulting in correlative geologic units. The location of the suspected fault near Statesboro, Georgia, generally coincides with the eastward extension of the Gulf Trough, a regional potentiometric anomaly in central Georgia.

Faye, R.E.; Prowell, D.C.

1982-01-01

264

DOT WEB PAGES (plain text) 1 DOT WWW Pages --Plain Text Copy June 15, 2014  

E-print Network

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6 DOT publications: scientific papers, popular-science descriptions, management documents 11 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.2 DOT popular-science descriptionsDOT WEB PAGES (plain text) 1 DOT WWW Pages -- Plain Text Copy ­ June 15, 2014 http://www.staff.science

Rutten, Rob

265

NW/Plains StatesNW/Plains States Regional AcademicRegional Academic  

E-print Network

Environmental HealthCommunity Environmental Health Assessments (PACEAssessments (PACE--EH)EH) ·· CommunicationCommunicationBased on 4 communication competencies for environmental health professionalsenvironmental healthNW/Plains StatesNW/Plains States Regional AcademicRegional Academic Environmental Public HealthEnvironmental

266

Sediment Sources and Storage in the Chesapeake Bay Watershed  

NASA Astrophysics Data System (ADS)

Physically and chemically, sediment is a pollutant of concern in many waterbodies. In the Chesapeake Bay, sediment is having an adverse effect on the living resources and habitat of the Chesapeake Bay and its watershed. Identifying significant sources of watershed sediment is important in reducing sediment loads. In the Chesapeake Bay, several approaches were used to understand the sources, transport, and storage of watershed-derived sediment. From 1985 through 2001, the U.S. Geological Survey collected suspended sediment at 35 stations draining portions of the 103,000 km2 Chesapeake Bay. Of the 35 sites, 4 of the 6 highest sediment yields were in the Conestoga River Basin, Pennsylvania, which drains to the Susquehanna River. In the Susquehanna River Basin (43,600 km2), erosion rates were determined using atmospheric 10Be at 92 river outlets and confirmed that the highest rates of erosion were in the Conestoga River Basin. In three small watersheds draining to the Chesapeake Bay -- the Pocomoke River (157 km2), Little Conestoga Creek (68.1 km2), and Mattawoman Creek (92.8 km2) -- sediment sources were identified using a sediment-source identification approach. In this approach, the sources of fine-grained suspended sediment in transport can be established by comparing physical and chemical properties of the suspended sediment to potential sources. In this study, suspended sediment (< 0.062 mm) collected during storm runoff was compared to upland sediment sources (cropland, construction sites, and forest) and channel corridor sources (channel banks and bed) using radionuclides (210Pb, 137Cs), stable isotopes (13C, 15N), and total C, N, and P. Preliminary results are available for two of the three watersheds. In the Pocomoke River watershed, which drains the Coastal Plain physiographic province, ditch beds which were dug to drain cropland were a significant source of sediment. In the Little Conestoga Creek watershed, which drains the Piedmont physiographic province, river banks and cropland were significant sources.

Gellis, A. C.; Landwehr, J. M.; Pavich, M.; Hupp, C. R.; Ritchie, J. C.

2006-05-01

267

Do abyssal scavengers use phytodetritus as a food resource? Video and biochemical evidence from the Atlantic and Mediterranean  

NASA Astrophysics Data System (ADS)

Deep-sea benthic communities derive their energetic requirements from overlying surface water production, which is deposited at the seafloor as phytodetritus. Benthic invertebrates are the primary consumers of this food source, with deep-sea fish at the top of the trophic hierarchy. Recently, we demonstrated with the use of baited cameras that macrourid fish rapidly respond to and feed vigorously on large plant food falls mimicked by spinach ( Jeffreys et al., 2010). Since higher plant remains are scarce in the deep-sea, with the exception of canyons, where terrestrial material has been observed, these results led us to ask if a more commonly documented plant material i.e. phytodetritus might form a food source for deep-sea fish and mobile scavenging megafauna. We simulated a phytodetritus dump at the seafloor in two contrasting environments (1) the NE Atlantic where carpets of phytodetritus have been previously observed and (2) the oligotrophic western Mediterranean, where the deposition of phytodetritus at the seafloor is a rare occurrence. We recorded the response of the scavenging fauna using an in situ benthic lander equipped with baited time-lapse cameras. In the NE Atlantic at 3000 m, abyssal macrourids and cusk-eels were observed ingesting the phytodetritus. The phytodetrital patch was significantly diminished within 2 h. Abundance estimates calculated from first arrival times of macrourids at the phytodetrital patch in the Atlantic corresponded with abundance estimates from video-transect indicating that fish were attracted to the scent of phytodetrital bait. In contrast to this, in the western Mediterranean at 2800 m a single macrourid was observed investigating the phytodetrital patch but did not feed from it. The phytodetrital patch was significantly diminished within 6.5 h as a result of mainly invertebrate activity. At 1900 m, Lepidion lepidion was observed near the lander and the bait, but did not feed. The phytodetrital patch remained intact until the end of the experiment. In the deployments in the Mediterranean abundance estimates from first arrival times at the bait, corrected for their body size, were lower than estimates obtained from video-transects and trawl catches. This suggests that the Mediterranean fish were not readily attracted to this food source. In contrast, invertebrates in the Balearic Sea were observed ingesting the phytodetritus bait despite the rare occurrence of phytodetritus dumps in the Mediterranean. Stable isotope values of the fish at both study sites, set within the context of the benthic food web, did not demonstrate a strong trophic link to phytodetritus. Fatty acid profiles of these fish indicated a strong link between their lipid pool and primary producers i.e. phytoplankton, which may be attributed to trophic transfer. The usefulness of fatty acid biomarkers in ascertaining deep-sea fish diets is discussed. Our study suggests that the abyssal grenadier C. armatus on the Atlantic Iberian margin is attracted to phytodetritus. However the exact contribution of this food source to the diet of macrourids in this area remains unresolved.

Jeffreys, Rachel M.; Lavaleye, Marc S. S.; Bergman, Magda J. N.; Duineveld, Gerard C. A.; Witbaard, Rob

2011-04-01

268

Serpentinization of abyssal peridotites from the MARK area, Mid-Atlantic Ridge: Sulfur geochemistry and reaction modeling  

USGS Publications Warehouse

The opaque mineralogy and the contents and isotope compositions of sulfur in serpentinized peridotites from the MARK (Mid-Atlantic Ridge, Kane Fracture Zone) area were examined to understand the conditions of serpentinization and evaluate this process as a sink for seawater sulfur. The serpentinites contain a sulfur-rich secondary mineral assemblage and have high sulfur contents (up to 1 wt.%) and elevated ??34Ssulfide (3.7 to 12.7???). Geochemical reaction modeling indicates that seawater-peridotite interaction at 300 to 400??C alone cannot account for both the high sulfur contents and high ??34Ssulfide. These require a multistage reaction with leaching of sulfide from subjacent gabbro during higher temperature (???400??C) reactions with seawater and subsequent deposition of sulfide during serpentinization of peridotite at ???300??C. Serpentinization produces highly reducing conditions and significant amounts of H2 and results in the partial reduction of seawater carbonate to methane. The latter is documented by formation of carbonate veins enriched in 13C (up to 4.5???) at temperatures above 250??C. Although different processes produce variable sulfur isotope effects in other oceanic serpentinites, sulfur is consistently added to abyssal peridotites during serpentinization. Data for serpentinites drilled and dredged from oceanic crust and from ophiolites indicate that oceanic peridotites are a sink for up to 0.4 to 6.0 ?? 1012 g seawater S yr-1. This is comparable to sulfur exchange that occurs in hydrothermal systems in mafic oceanic crust at midocean ridges and on ridge flanks and amounts to 2 to 30% of the riverine sulfate source and sedimentary sulfide sink in the oceans. The high concentrations and modified isotope compositions of sulfur in serpentinites could be important for mantle metasomatism during subduction of crust generated at slow spreading rates. ?? 2003 Elsevier Science Ltd.

Alt, J.C.; Shanks, W. C., III

2003-01-01

269

The Processes Surrounding Channel Evolution following a Partial Dam Removal on the Coastal Plain of Virginia Kristen M. Cannatelli, University of Virginia  

E-print Network

of Virginia The physical changes to a newly forming river in a slow draining reservoir following partial dam that is applicable to draining reservoirs on the coastal plain where there is high cohesive sediment content. A partial dam breach on tributary of the James River (VA) has led to slow draining of the reservoir. Data

Curran, Joanna C.

270

Preliminary geological interpretation and lithologic log of the exploratory geothermal test well (INEL-1), Idaho National Enginering Laboratory, eastern Snake River Plain, Idaho  

Microsoft Academic Search

A 10,365 ft (3159 m) geothermal test well was drilled in the spring of 1979 at the Idaho National Engineering Laboratory, eastern Snake River Plain, Idaho. The majority of rock types encountered in the borehole are of volcanic origin. An upper section above 2445 ft (745 m) consists of basaltic lava flows and interbedded sediments of alluvial, lacustrine, and volcanic

D. J. Doherty; L. A. McBroome; M. A. Kuntz

1979-01-01

271

Geomicrobiology of Archaeal Communities Isolated from an Off-axis Abyssal Hill Fault Scarp on the East Pacific Rise Flank at 9° 27'N  

NASA Astrophysics Data System (ADS)

Although heat flow studies suggest that ~70% of the hydrothermal heat loss in the oceans occurs in the abyssal hill terrain on the flanks of mid-ocean ridges, very few off-axis hydrothermal sites have been discovered. In May 2002, sedimentary blowout structures of probable hydrothermal origin were discovered along East Pacific Rise at 9° 27'N on an off-axis abyssal hill bounded by a fault scarp covered with orange-brown microbial flocculations. Recovered samples of these flocculations have presented an opportunity to study the unknown nature and role of thermophilic and hyperthermophilic microbial communities on the ridge flanks. Furthermore, the archaeal communities that we have identified in the samples are useful "microbial tracers" which can be used to locate off-axis areas of moderate-to-high temperature fluid flow (>50° C). In this study, we used molecular techniques to isolate, amplify, and sequence community archaeal RNA sequences from fault scarp flocculations collected with a slurp pump system mounted in the Alvin basket. Molecular phylogenies based on 16S rRNA were constructed. Phylogenetic relationships of isolated clones were used to infer temperature preferences of archaeal communities. We identified 12 clones that clustered within thermophilic or hyperthermophilic clades within Archaea suggesting that moderately high temperature fluid (>50° C) exited the seafloor along this abyssal hill fault scarp. Our studies also suggest that these communities mediate the formation of Fe-sulfide mineral phases. Analysis of the samples with an Environmental Scanning Electron Microscope (ESEM) and X-ray energy dispersive analysis (EDS) revealed unique iron sulfide mineral phases with anomalously low Fe/S ratios in direct association with microbial communities.

Ehrhardt, C. J.; Haymon, R.; Holden, P.; Lamontagne, M.

2003-12-01

272

North-south compression, active uplift, and abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean  

NASA Astrophysics Data System (ADS)

This article presents near N-S compression, active uplift tectonism, and the consequent abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean. The mantle peridotite ridge is about 80 km long, 25 km wide, 3800 m high, and of near E-W direction. The ridge flanks are extremely steep with sub-vertical scarps of about 2000 m of relative height. The Flandrian wave-cut and the 14C datings for the carbonaceous algae of the Saint Peter and Saint Paul Rock indicate active uplift of 1.5 mm/year. The tectonic factures shows conjugated system of N-S compression tending slightly to NW-ES. Close to the peridotite ridge, the earthquakes with near N-S compression focal mechanism take place. The southern half of the peridotite ridge is constituted by undeformed peridotite. The existence of corrugation morphology indicates that the mantle rocks are originated from old megamullion. On the other hand, the northern half is composed of strongly deformed mylonitic peridotite suggesting that the ultramafic rocks are possibly originated from sub-crustal abyssal mantle of old transform fault. The mylonite structure is intensely perturbed indicating the tectonic events which disturbed the original parallel structure. The Saint Paul transform fault zone is characterized by E-W trend right lateral movement and the near N-S compression is unlikely. Therefore, an unusual local geotectonic process is expected. This tectonism was originated from the plate boundary jump at about 8 Ma, caused by the emergence of a new ridge segment, and the new transform fault is oblique to the relative plate movement. This angular discrepancy causes the compression perpendicular to the oblique transform fault, of near N-S direction, which squeeze out the sub-crustal abyssal mantle up to sea level. Therefore, the peridotite Ridge is considered to be a pressure ridge of the strike-slip movement of the Saint Paul transform fault.

Motoki, A.; Sichel, S. E.; Campos, T. F.; Motoki, K. F.; Szatmari, P.; Poseidon-Colmeia

2013-05-01

273

Reproduction among protobranch bivalves of the family Nuculidae from sublittoral, bathyal, and abyssal depths off the New England coast of North America  

NASA Astrophysics Data System (ADS)

Protobranch bivalve species of the family Nuculidae pass through either a planktonic lecithotrophic larval stage or a direct non-planktonic development. Oogenesis of the three sublittoral species examined is synchronous. Deposition of egg masses by Nucula delphinodonta and spawning by Nucula annulata and Nucula proxima occur only during summer months. Among the four bathyal and abyssal species, Ennucula similis, Ennucula granulosa, Deminucula atacellana, and Brevinucula verrilli, oogenesis is asynchronous and there is no discernable pattern of periodicity of spawning. Absence of periodicity in reproduction in these deep-sea species is confirmed by examination of individuals from dredge samples taken at different times of the year. The median apparent fecundity among both sublittoral and deep-sea species is directly related to size (i.e. shell length) and age. Among the Nuculidae the median apparent fecundity is greater among sublittoral than bathyal and abyssal species. The geographic distribution of a species depends on its capacity to disperse. The dispersal of the planktonic lecithotrophic larvae of the sublittoral species N. annulata and N. proxima is limited to the continental shelf of the northwestern Atlantic by inshore bottom circulation and because these very small planktonic larvae (<2.5 mm) lack the capacity to move vertically upward through the water column into the offshore currents. On the other hand, the bathyal and abyssal species having lecithotrophic larvae have a very wide amphi-Atlantic distribution extending from 60°N to 40°S latitude along the North and South American coasts and from 55°N to ca. 19°S from off Europe southwards to the coast of West Africa as a consequence of dispersal by planktonic lecithotrophic larvae along the seafloor. The amphi-Atlantic dispersal must occur stepwise between deep-sea populations (e.g., off Greenland). Such a geographic distribution indicates a widespread dispersal and is supported by the genetic similarity that has been described between North American and western European populations of D. atacellana.

Scheltema, Rudolf S.; Williams, Isabelle P.

2009-09-01

274

Heat flow in the Piedmont and Atlantic Coastal Plain of the southeastern United States  

NASA Astrophysics Data System (ADS)

Seventy-four new heat flow values have been determined at sites from New Jersey to Georgia, mostly in the Piedmont and Atlantic Coastal Plain provinces. Relatively high heat flows are characteristic of synmetamorphic and postmetamorphic granites exposed in the Piedmont and occurring in the basement beneath the sediments of the Atlantic Coastal Plain. The Piedmont heat flow and heat generation values, determined in granites, metagranites, and one Slate Belt site, lie in a belt approximately parallel to major structural trends in the Appalachians. These values fall on or near the regression line: q(mW/m2) = 29.8 ± 1.5(mW/m2) + 7.8(km) ± 0.475A(?W/m3) (R = 0.97477). It is proposed that the occurrence of a thrust fault that truncates granites at a depth, D, of 7.8 km is directly responsible for this linear relation in the eastern Piedmont. Basement core from beneath the sediments of the Atlantic Coastal Plain was recovered at ten sites. Results from five of these sites plus one site in the Baltimore Gabbro define a second linear relation with a slope (D = 8.0±0.380 km; R = 0.99550) approximately parallel to the Piedmont relation, but with an intercept of 48.2±0.8 mW/m2. These two relations may represent different heat flow provinces in the southeastern United States or the linear relations may simply be a consequence of differences in the thicknesses of the upper heat-producing layer at least as far east as postmetamorphic granites sampled under the Coastal Plain.

Costain, J. K.; Speer, J. A.; Glover, L., III; Perry, L.; Dashevsky, S.; McKinney, M.

1986-02-01

275

Fire Cycles on the Northern Great Plains and Their Relation to Prairie Drought  

NASA Astrophysics Data System (ADS)

Drought is a naturally occurring, recurrent phenomenon that has historically gripped large regions of the United States, often with catastrophic consequences. Human insight into the duration, frequency, and dynamics of drought is largely limited to short-term observation. For example, the "Dust Bowl" of the 1930's in the central plains is one of the most vivid cases of prolonged drought in the USA and yet it persisted for less than a decade. To circumnavigate this limited perspective, we employed a paleoenvironmental approach to better characterize landscape response to prairie droughts and specifically document fire response to droughts. Two long sediment cores were collected from Kettle and Brush lakes in the Northern Great Plains (NGP) and age-depth models were developed for the cores by fitting locally weighted loess curves to AMS radiocarbon dates. The cores were continuously sub-sampled at high resolution (1 cm) for particulate charcoal, pollen, sediment mineralogy, and loss-on-ignition. In contrast to recent human observation, spectral and wavelet analyses reveal that multi-decadal to centennial drought cycles have persisted on the northern plains for much of the last ca. 10,000 years, though there were intervals where the cycles were muted, further compounding the dynamics of climate on the plains. In the latest Holocene interval, 160-year fire and drought cycles are clearly denoted. Fires are more common during the wet phases of the drought cycles because moist conditions foster increased grass productivity, resulting in greater fuel loads. In contrast, forbs expanded during the drier periods, limiting fuel loads which resulted in less fire. The charcoal data reveal three general Holocene fire intervals on the NGP associated with millennial-scale changes in climate. In general, the incidence of fire was greater in the early- and late-Holocene with less fire during the warm dry mid-Holocene.

Brown, K. J.; Clark, J. S.; Grimm, E. C.; Donovan, J. J.; Mueller, P.

2004-12-01

276

Environmental changes in the central Po Plain (northern Italy) due to fluvial modifications and anthropogenic activities  

NASA Astrophysics Data System (ADS)

The fluvial environment of the central Po Plain, the largest plain in Italy, is discussed in this paper. Bounded by the mountain chains of the Alps and the Apennines, this plain is a link between the Mediterranean environment and the cultural and continental influences of both western and eastern Europe. In the past decades, economic development has been responsible for many changes in the fluvial environment of the area. This paper discusses the changes in fluvial dynamics that started from Late Pleistocene and Early Holocene due to distinct climatic changes. The discussion is based on geomorphological, pedological, and archaeological evidences and radiocarbon dating. In the northern foothills, Late Pleistocene palaeochannels indicate several cases of underfit streams among the northern tributaries of the River Po. On the other hand, on the southern side of the Po Plain, no geomorphological evidence of similar discharge reduction has been found. Here, stratigraphic sections, together with archaeological remains buried under the fluvial deposits, show a reduction in the size of fluvial sediments after the 10th millennium BC. During the Holocene, fluvial sedimentation became finer, and was characterised by minor fluctuations in the rate of deposition, probably related to short and less intense climatic fluctuations. Given the high rate of population growth and the development of human activities since the Neolithic Age, human influence on fluvial dynamics, especially since the Roman Age, prevailed over other factors (i.e., climate, tectonics, vegetation, etc.). During the Holocene, the most important changes in the Po Plain were not modifications in water discharge but in sediment. From the 1st to 3rd Century AD, land grants to war veterans caused almost complete deforestation, generalised soil erosion, and maximum progradation of the River Po delta. At present, land abandonment in the mountainous region has led to reafforestation. Artificial channel control in the mountain sector of the basins and in-channel gravel extraction (now illegal but very intense in the 1960s and 1970s) are causing erosion along the rivers and along large sectors of the Adriatic coast. These changes are comparable with those occurring in basins of other Mediterranean rivers.

Marchetti, Mauro

2002-05-01

277

Project HOTSPOT: Borehole geophysics log interpretation from the Snake River Plain, Idaho  

NASA Astrophysics Data System (ADS)

The Snake River Plain (SRP), Idaho, hosts potential geothermal resources due to elevated groundwater temperatures associated with the thermal anomaly Yellowstone-Snake River hotspot. Project HOTSPOT has coordinated international institutions and organizations to understand subsurface stratigraphy and assess geothermal potential. Over 5.9km of core were drilled from three boreholes within the SRP in an attempt to acquire continuous core documenting the volcanic and sedimentary record of the hotspot: (1) Kimama, (2) Kimberely, and (3) Mountain Home. The most eastern drill hole is Kimama located along the central volcanic axis of the SRP and documents basaltic volcanism. The Kimberely drill hole was selected to document continuous volcanism when analysed in conjunction with the Kimama drill hole and is located near the margin of the plain. The Mountain Home drill hole is located along the western plain and documents older basalts overlain by sediment. A suite of ground and borehole geophysical surveys were carried out within the SRP between 2010 and 2012. The borehole geophysics logs included gamma ray (spectral and natural), neutron hydrogen index, electrical resistivity, magnetic susceptibility, ultrasonic borehole televiewer imaging, full waveform sonic, and vertical seismic profile. The borehole geophysics logs were qualitatively assessed through visual interpretation of lithological horizons and quantitatively through physical property specialized software and digital signal processing automated filtering process to identify step functions and high frequency anomalies. Preliminary results were published by Schmitt et al. (2012), Potter et al. (2012), and Shervais et al. (2013). The results are continuously being enhanced as more information is qualitatively and quantitatively delineated from the borehole geophysics logs. Each drill hole encounters three principal units: massive basalt flows, rhyolite, and sediments. Basalt has a low to moderate porosity and is low in the natural gamma ray isotopes uranium, thorium, and potassium, while rhyolites produce high total gamma ray responses. Sediment interbeds become apparent as the radioactivity associated with fine grained minerals is significantly higher than that of the host rock (e.g. basalt) due to high hydrogen concentration within the crystal structure of clays. Basalt lacks conductive minerals and results in high resistivity but moderate magnetic susceptibility. The sediments on the other hand are highly conductive and have a low magnetic susceptibility. The basalt and rhyolite units are relatively massive except for fractures which become apparent in the ultrasonic borehole televiewer. Signal is lost in soft sediments resulting in dark regions when full amplitude is displayed for the ultrasonic borehole televiewer. The massive basalt shows short P- and S-wave travel times and therefore a high sonic velocity, while the sediments display only P-wave first arrivals.

Lee, M. D.; Schmitt, D. R.; Chen, X.; Shervais, J. W.; Liberty, L. M.; Potter, K. E.; Kessler, J. A.

2013-12-01

278

Late Middle Pleistocene deposits at Norton Farm on the West Sussex coastal plain, southern England  

NASA Astrophysics Data System (ADS)

The coastal plain of West Sussex, southern England, is internationally important because of the sequence of discrete high-sea-level events preserved at various elevations across it. New evidence is presented from a site at Norton Farm, near Chichester, on the Lower Coastal Plain, where Pleistocene marine sands, fining upwards into silts, occur between 5.3 m and 9.1 m OD. The sequence reflects a regressive tendency at the transition from an interglacial to a cold stage. The marine sands have yielded foraminifera, ostracods and molluscs that indicate a declining marine influence through the sequence, culminating in a tidal mudflat, strongly weathered in places. Cool-climate foraminifera (including Elphidium clavatum, Cassidulina reniformis and Elphidium albiumbilicatum) and ostracods have been recovered from the marine sands. Some species with an apparent preference for warmer water conditions, however, are also present. Freshwater taxa washed into the terminal marine sediments include some cold climate indicators, such as Pisidium stewarti and P. obtusale lapponicum. Additional evidence for cool climatic conditions during the deposition of the upper part of the marine sequence is provided by the lack of tree taxa in the pollen record and by features of the micromorphology. The marine sediments probably began accumulating during OIS 7, a conclusion based on their elevation, on amino acid ratios from shells, but especially on vertebrate evidence, particularly the presence of a small form of horse, together with a large, distinctive, form of northern vole (Microtus oeconomus). The occurrence of cool climate indicators in these marine sediments may demonstrate a lag between the climatic deterioration and the expected glacio-eustatic fall in relative sea-level. This evidence appears to support the conclusions drawn from the study of coral terraces in Barbados. Such a scenario would provide the conditions necessary for the emplacement of the large erratic boulders reported from the Lower Coastal Plain of West Sussex.

Bates, Martin R.; Bates, C. Richard; Gibbard, Philip L.; MacPhail, Richard I.; Owen, Frederick J.; Parfitt, Simon A.; Preece, Richard C.; Roberts, Mark B.; Robinson, J. Eric; Whittaker, John E.; Wilkinson, Keith N.

2000-01-01

279

Predicting reservoir sedimentation  

E-print Network

Sediments accumulate in reservoirs and significantly decrease storage capacity. Predicting sedimentation is an important consideration in the design of new reservoir projects and in the management of existing reservoirs. Sedimentation rates may vary...

Wooten, Stephanie

2012-06-07

280

Externality Effects Associated with Floods and Flood Plain Management.  

National Technical Information Service (NTIS)

The impact of externalities, where social and private costs and benefits differ, on flood plain management is discussed. The primary externality is the concern that occupation of the flood plain leads to greater social costs than benefits. Information is ...

D. Freshwater

1976-01-01

281

18 CFR 801.8 - Flood plain management and protection.  

Code of Federal Regulations, 2013 CFR

...nature for the protection of flood plains subject to frequent flooding. (3) Assist in the study and classification of flood prone lands to ascertain the relative risk of flooding, and establish standards for flood plain management....

2013-04-01

282

18 CFR 801.8 - Flood plain management and protection.  

Code of Federal Regulations, 2011 CFR

...nature for the protection of flood plains subject to frequent flooding. (3) Assist in the study and classification of flood prone lands to ascertain the relative risk of flooding, and establish standards for flood plain management....

2011-04-01

283

18 CFR 801.8 - Flood plain management and protection.  

Code of Federal Regulations, 2012 CFR

...nature for the protection of flood plains subject to frequent flooding. (3) Assist in the study and classification of flood prone lands to ascertain the relative risk of flooding, and establish standards for flood plain management....

2012-04-01

284

18 CFR 801.8 - Flood plain management and protection.  

...nature for the protection of flood plains subject to frequent flooding. (3) Assist in the study and classification of flood prone lands to ascertain the relative risk of flooding, and establish standards for flood plain management....

2014-04-01

285

18 CFR 801.8 - Flood plain management and protection.  

Code of Federal Regulations, 2010 CFR

...false Flood plain management and protection...Conservation of Power and Water Resources SUSQUEHANNA RIVER...8 Flood plain management and protection...essential part of water resources management, the Commission...

2010-04-01

286

Optically stimulated luminescence dating of Southern High Plains archaeological sites  

E-print Network

Optically stimulated luminescence dating of Southern High Plains archaeological sites James K of optically stimulated luminescence (OSL) dating, applying mainly single-grain analyses, was therefore. Keywords: Optically stimulated luminescence; Single-grain resolution; Southern High Plains; Paleoindian

Holliday, Vance T.

287

WESTERN GREAT PLAINS BIG RIVER FLOODPLAIN extent exaggerated for display  

E-print Network

Southern Plains Herbaceous Vegetation SYMPHORICARPOS OCCIDENTALIS TEMPORARILY FLOODED SHRUBLAND ALLIANCE Symphoricarpos occidentalis Shrubland TYPHA (ANGUSTIFOLIA, LATIFOLIA) - (SCHOENOPLECTUS SPP.) SEMIPERMANENTLY

288

DENDROCLIMATIC POTENTIAL IN THE NORTHERN GREAT PLAINS  

Microsoft Academic Search

We evaluate the potential for dcndroclimatological reconstruction in the northern Great Plains of the United States, based on a newly developed network of 23 chronologies of bur oa k (Quercus macrocarpa), ponderosa pine (Pinus ponderosa) and Rocky Mountain juniper (Juniperus scopoulorum) from North Dakota, South Dakota and Iowa. Earliest dates of specimens are AD 1281 for pine, 1597 for juniper,

CAROLYN HUL L SIEG; DAVID MEKO; ARTHUR T. DeGAETANO; WANMEI NI

1996-01-01

289

Agricultural Change Among Great Plains Russian Germans  

Microsoft Academic Search

Russian German farmers who concentrated on the Great Plains in the late nineteenth century brought with them agricultural experience in a subhumid environment. Their diversified operations and use of small grains contrasted sharply with the humid-land agricultural system, emphasizing corn and livestock, dominant among settlers from the Midwest. The need to adopt strategies appropriate to the climate of the Great

Bradley H. Baltensperger

1983-01-01

290

Reading for Young People: The Great Plains.  

ERIC Educational Resources Information Center

One of five annotated bibliographies that describe books about certain regions of the United States, this compilation focuses on books about the Great Plains. The stated purposes of these regional bibliographies are: (1) to introduce young people living in the subject region to books dealing with their cultural heritage, (2) to help young people…

Laughlin, Mildred

291

Geothermal features of Snake River plain, Idaho  

Microsoft Academic Search

The Snake River plain is the track of a hot spot beneath the continental lithosphere. The track has passed through southern Idaho as the continental plate has moved over the hot spot at a rate of about 3.5 cm\\/yr. The present site of the hot spot is Yellowstone Park. As a consequence of the passage, a systematic sequence of geologic

Blackwell

1987-01-01

292

Plains Culture Area. Native American Curriculum Series.  

ERIC Educational Resources Information Center

One in a series of Native American instructional materials, this booklet introduces elementary students to the tribes of the plains culture area, extending from the Rocky Mountains to the Mississippi River and from Texas to Canada. Written in simple language, the booklet begins with a brief description of the region--its extreme climate and the…

Ross, Cathy; Fernandes, Roger

293

Satellite-Based Assessment of Sediment Transport, Distribution and Resuspension Associated with the Atchafalaya River Discharge Plume  

NASA Technical Reports Server (NTRS)

Tbe Atchafalaya River discharges over 80 x 10(exp 6) tons of sediment annually onto the broad shallow continental shelf of central and western Louisiana. Satellite imagery from the NOAA AVHRR and Terra MODIS are used in this paper to quantify suspended sediment concentrations and to assess sediment transport processes along the Louisiana shelf under varying conditions of river discharge and wind forcing. The image data reveal the maim sources of sediment, direction of transport amd regional extent of wind-wave resuspension. The prevailing easterly winds transport much of the suspended sediments westward toward the Chernier Plain in a well-defined mud stream. Westerly flow rates of 25-50 cm/s (21-43 km per day) have been measured, yielding a transit time of about 1.5-2.5 days from the mouth of Atchafalaya Bay to the Chernier Plain. Progradation rates along the Chernier Plain coast reach 50 m per year. The westward-flowing Atchafalaya "mud stream" is rapidly disrupted by westerly winds and northerly winds, which accompany frequent winter storms and less frequent tropical storms or hurricanes. During these events, the coastal current reverses and sediments are rapidly transported out of Atchafalaya Bay and offshore where substantial sedimentary deposits can also be found. Offshore sediment fluxes during storm events, in combination with wind-wave resuspension, can result in surface sediment "plumes" extending 70 km offshore and 150 km alongshore. Field measurements of suspended sediment concentrations, current and wind velocities, and directions are used to assess sediment transport processes on the shelf. These combined processes are extending the pro-delta deposits of the Atchafalaya-Wax Lake delta complex far onto the continental shelf and supplying sediments for a renewal era of progradation along tbe downdrift Chernier Plain coast.

Walker, Nan; Roberts, Harry; Stone, Gregory; Bentley, Samuel; Huh, Oscar; Sheremet, Alexandru; Rouse, Larry; Inoue, Masamichi; Welsh, Susan; Hsu, S. A.

2002-01-01

294

Evolution of radioactive dose rates in fresh sediment deposits along coastal rivers draining Fukushima contamination plume  

NASA Astrophysics Data System (ADS)

Measurement of radioactive dose rates in fine sediment that has recently deposited on channel bed-sand provides a solution to address the lack of continuous river monitoring in Fukushima Prefecture after Fukushima Dai-ichi nuclear power plant (FDNPP) accident. We show that coastal rivers of Eastern Fukushima Prefecture were rapidly supplied with sediment contaminated by radionuclides originating from inland mountain ranges, and that this contaminated material was partly exported by typhoons to the coastal plains as soon as by November 2011. This export was amplified during snowmelt and typhoons in 2012. In 2013, contamination levels measured in sediment found in the upper parts of the catchments were almost systematically lower than the ones measured in nearby soils, whereas their contamination was higher in the coastal plains. We thereby suggest that storage of contaminated sediment in reservoirs and in coastal sections of the river channels now represents the most crucial issue.

Evrard, Olivier; Chartin, Caroline; Onda, Yuichi; Patin, Jeremy; Lepage, Hugo; Lefèvre, Irène; Ayrault, Sophie; Ottlé, Catherine; Bonté, Philippe

2013-10-01

295

Evolution of radioactive dose rates in fresh sediment deposits along coastal rivers draining Fukushima contamination plume  

PubMed Central

Measurement of radioactive dose rates in fine sediment that has recently deposited on channel bed-sand provides a solution to address the lack of continuous river monitoring in Fukushima Prefecture after Fukushima Dai-ichi nuclear power plant (FDNPP) accident. We show that coastal rivers of Eastern Fukushima Prefecture were rapidly supplied with sediment contaminated by radionuclides originating from inland mountain ranges, and that this contaminated material was partly exported by typhoons to the coastal plains as soon as by November 2011. This export was amplified during snowmelt and typhoons in 2012. In 2013, contamination levels measured in sediment found in the upper parts of the catchments were almost systematically lower than the ones measured in nearby soils, whereas their contamination was higher in the coastal plains. We thereby suggest that storage of contaminated sediment in reservoirs and in coastal sections of the river channels now represents the most crucial issue. PMID:24165695

Evrard, Olivier; Chartin, Caroline; Onda, Yuichi; Patin, Jeremy; Lepage, Hugo; Lefevre, Irene; Ayrault, Sophie; Ottle, Catherine; Bonte, Philippe

2013-01-01

296

44 CFR 10.14 - Flood plains and wetlands.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Flood plains and wetlands. 10.14 Section 10.14 Emergency...Procedures § 10.14 Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions of this part...

2011-10-01

297

44 CFR 10.14 - Flood plains and wetlands.  

Code of Federal Regulations, 2012 CFR

...2011-10-01 true Flood plains and wetlands. 10.14 Section 10.14 Emergency...Procedures § 10.14 Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions of this part...

2012-10-01

298

44 CFR 10.14 - Flood plains and wetlands.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Flood plains and wetlands. 10.14 Section 10.14 Emergency...Procedures § 10.14 Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions of this part...

2010-10-01

299

44 CFR 10.14 - Flood plains and wetlands.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Flood plains and wetlands. 10.14 Section 10.14 Emergency...Procedures § 10.14 Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions of this part...

2013-10-01

300

A Study of Haptic Representation of Virtual Plain Wall  

Microsoft Academic Search

The purpose of this study is to develop a haptic representation system of virtual wall. The virtual plain wall s ystem requires functions to represent a haptic sense and a wide plain area. To realize a virtual plain wall, a small wall panel was mounted on a 3-axis manipulator, and a 3-axis force sensor was equipped on the wall panel

P. Weangsima; K. Fujita; T. Honda

2004-01-01

301

49 CFR 215.107 - Defective plain bearing box: General.  

Code of Federal Regulations, 2010 CFR

... § 215.107 Defective plain bearing box: General. A railroad may not place or...the car has— (a) A plain bearing box that does not contain visible free oil; (b) A plain bearing box lid that is missing, broken, or...

2010-10-01

302

Suggested Insecticides for Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas--2008  

E-print Network

This bulletin lists suggested insecticides (by brand name) and application rates for controlling cotton pests found in the High Plains, Rolling Plains and Trans Pecos areas of Texas. This publication should be used in conjunction with publication E...

Siders, Kerry; Baugh, Brant A.; Sansone, Chris; Kerns, David L.

2008-06-10

303

Geophysical Constraints on Sediment Dispersal Systems  

NASA Astrophysics Data System (ADS)

Geophysical and geological approaches were employed to understand sediment dispersal systems and their response to various forcing functions (i.e., sea level fluctuations, tectonic deformation, sediment supply, and climate change). Two end member marine environments were studied; one with high precipitation and sediment discharge (Gulf of Papua, Papua New Guinea) and the other with low precipitation and sediment discharge (Oceanside Littoral Cell). The high-sedimentation rate in the Gulf of Papua (GoP) yields high-fidelity records of Earth history. As part of the NSF Margins Source-to-Sink (S2S) program, we acquired CHIRP and core data across the GoP continental shelf that complemented onshore and offshore research in the region. CHIRP seismic data imaged three Holocene sedimentary lobes. The older Central lobe is downlapped by two younger lobes to the north and south. Sediment analysis showed that the older Central lobe has an elemental signature similar to the younger Northern lobe with both sourced from the Purari River watershed and lobe migration appears to be climatically controlled. The Southern lobe has elemental signatures more consistent with the Fly River watershed. Our results suggest the northern rivers began depositing sediments on the shelf during the Holocene sea level rise in the central region of the GoP and migrated abruptly north at ~2 kybp. Conversely, during the early Holocene transgression, sediments in the Fly drainage system were sequestered onshore infilling accommodation created in the large low-relief coastal plain during the sea level rise. Upon infilling the onshore accommodation, the Fly River delivered sediment to the ocean and formed the Southern lobe. Such differences in onshore storage capacity may introduce a lag between low-gradient rivers (Type I) with a large coastal plain versus high-gradient river systems (Type II) with small coastal plains. The second study site is in the sediment-starved Oceanside Littoral Cell (OCL) of Southern California. Terrestrial Laser scanning was performed seasonally using Light Detection and Ranging (LiDAR) technology to perform time series modeling of sea cliff erosion. We established a repeatable and reliable protocol for efficiently conducting coastal sea cliff mapping. Changes in geomorphology were quantified to determine the forcing mechanisms controlling erosion. Results from our investigations provide insight into "hot spots" of erosion along the coast and the controlling processes. Subaerial and marine erosion are predominantly controlled by precipitation and wave energy, respectively. Beach elevation, a seasonally dependent variable, is the most important physical factor controlling whether a sea cliff is vulnerable to marine-based or subaerial erosion. Due to the heavy coastal development and important state revenue from beach tourism, it is critical to continue this type of time series research to understand fully these relationships. This study provides a baseline from which future change due to the rapid sea level rise (>3 mm/yr) and climate change can be assessed.

Johnstone, Elizabeth Anne Carruthers

304

Land use and conservation reserve program effects on the persistence of playa wetlands in the High Plains.  

PubMed

Watershed cultivation and subsequent soil erosion remains the greatest threat to the service provisioning of playa wetlands in the High Plains. The U.S. Department of Agriculture's (USDA) Conservation Reserve Program (CRP) plants perennial vegetation cover on cultivated lands including playa watersheds, and therefore, the program influences sediment deposition and accumulation in playas. Our objective was to measure the effects of the CRP on sediment deposition by comparing sediment depth and present/historic size characteristics in 258 playas among three High-Plains subregions (northern, central, and southern) and the three dominant watershed types: cropland, CRP, and native grassland. Sediment depth and resultant volume loss for CRP playas were 40% and 57% lower than cropland playas, but 68% and 76% greater than playas in native grassland. Playas in CRP had remaining volumes exceeding those of cropland playas. Grassland playas had nearly three times more original playa volume and 122% greater wetland area than CRP playas. Overall, playas were larger in the south than other subregions. Sediment depth was also three times greater in the south than the north, which resulted in southern playas losing twice as much total volume as northern playas. However, the larger southern playas provide more remaining volume per playa than those in other subregions. The results of this study demonstrate the importance of proper watershed management in preserving playa wetland ecosystem service provisioning in the High Plains. Furthermore, we identify regional differences in playas that may influence management decisions and provide valuable insight to conservation practitioners trying to maximize wetland services with limited resources. PMID:24635683

Daniel, Dale W; Smith, Loren M; Haukos, David A; Johnson, Lacrecia A; McMurry, Scott T

2014-04-15

305

Ancient DNA complements microfossil record in deep-sea subsurface sediments  

PubMed Central

Deep-sea subsurface sediments are the most important archives of marine biodiversity. Until now, these archives were studied mainly using the microfossil record, disregarding large amounts of DNA accumulated on the deep-sea floor. Accessing ancient DNA (aDNA) molecules preserved down-core would offer unique insights into the history of marine biodiversity, including both fossilized and non-fossilized taxa. Here, we recover aDNA of eukaryotic origin across four cores collected at abyssal depths in the South Atlantic, in up to 32.5 thousand-year-old sediment layers. Our study focuses on Foraminifera and Radiolaria, two major groups of marine microfossils also comprising diverse non-fossilized taxa. We describe their assemblages in down-core sediment layers applying both micropalaeontological and environmental DNA sequencing approaches. Short fragments of the foraminiferal and radiolarian small subunit rRNA gene recovered from sedimentary DNA extracts provide evidence that eukaryotic aDNA is preserved in deep-sea sediments encompassing the last glacial maximum. Most aDNA were assigned to non-fossilized taxa that also dominate in molecular studies of modern environments. Our study reveals the potential of aDNA to better document the evolution of past marine ecosystems and opens new horizons for the development of deep-sea palaeogenomics. PMID:23658006

Lejzerowicz, Franck; Esling, Philippe; Majewski, Wojciech; Szczucinski, Witold; Decelle, Johan; Obadia, Cyril; Arbizu, Pedro Martinez; Pawlowski, Jan

2013-01-01

306

Suspended sediment dynamics in the Amazon River of Peru  

NASA Astrophysics Data System (ADS)

The erosion and transport of sediments allow us to understand many activities of significance, such as crust evolution, climate change, uplift rates, continental processes, the biogeochemical cycling of pollutants and nutrients. The Amazon basin of Peru has contrasting physiographic and climatic characteristics between the Andean piedmont and the plains and between the north and south of the basin which is why there are 8 gauging stations located along the principal rivers of the Andean piedmont (Marañón, Huallaga, Ucayali) and the plain (Marañón, Tigre, Napo, Ucayali and Amazon rivers). Since 2003, the ORE-Hybam (IRD-SENAMHI-UNALM) observatory has performed out regular measurements at strategic points of the Amazon basin to understand and model the systems, behavior and long-term dynamics. On the Andean piedmont, the suspended yields are governed by a simple model with a relationship between the river discharge and the sediment concentration. In the plain, the dilution effect of the concentrations can create hysteresis in this relationship on a monthly basis. The Amazon basin of Peru has a sediment yield of 541 *106 t year-1, 70% comes from the southern basin.

Armijos, Elisa; Crave, Alain; Vauchel, Philippe; Fraizy, Pascal; Santini, William; Moquet, Jean-Sèbastien; Arevalo, Nore; Carranza, Jorge; Guyot, Jean-Loup

2013-07-01

307

Detrital carbonate-rich sediments, northwestern Labrador Sea: Implications for ice-sheet dynamics and iceberg rafting (Heinrich) events in the North Atlantic  

Microsoft Academic Search

Much of the bed of the central and eastern sectors of the Laurentide Ice Sheet was underlain by Paleozoic carbonates. We propose that pulses of detrital carbonate-rich sediments in two cores from the northwestern Labrador Sea reflect episodes when an ice stream from the Hudson Strait extended to the shelf break and delivered sediment onto the slope and deep-sea plain.

J. T. Andrews; K. Tedesco

1992-01-01

308

Long-term reworking of volcanic ash deposited in the abyssal ocean based on uranium and thorium isotope measurements  

NASA Astrophysics Data System (ADS)

A red-clay core from north of New Zealand contains a 21 cm-thick layer of the 340 thousand-year old Rangitawa ash. Uranium and thorium isotope measurements on this core show that ash continuously contributes to sediments overlying the ash layer, ranging from ~ 58% immediately above the ash to ~ 8% at the core top. Rather than from an upward bioturbation or subsequent volcanic eruptions, the ash in sediments is most likely sourced from suspended Rangitawa ash in the nepheloid layer that has steadily re-deposited at the core site ever since the Whakamaru super-eruption. We suggest that this lateral transport bears important influence on interpreting marine sediment proxy records.

Wang, Xianfeng; Broecker, Wallace S.

2013-08-01

309

Development of tidal inlet on Mississippi River deltaic plain  

SciTech Connect

Surface sampling and bathymetric surveying in 1981 and charts from 1853 to 1934 are used to formulate the history of Quatre Bayou Pass, a major inlet within the transgressive environment of the Mississippi River deltaic plain. Over this period, land loss processes caused marsh to give way to lakes and bays; therefore, tidal exchange intensified through a break in the coastal barrier. Beach sand was reworked into small tidal deltas. As lakes and bays enlarged further, the tidal prism increased; consequently, both the pass and the sandy tidal deltas increased in size. Over the last century, the increased tidal flow caused Quatre Bayou Pass to have an eight-fold cross-sectional area enlargement and a three-fold ebb-tidal delta volume increase. At present, the throat is 15 m (49 ft) deep and 1.2 km (0.7 mi) wide, while the ebb-tidal delta is comprised of 14.9 by 10/sup 6/ +/- 10% m/sup 3/ of sediment. Concurrent with these developments, recession of the barrier and much of the shoreface proceeded at a rapid rate. Because the ebb-tidal delta had a simultaneous increase in volume, the shoreface in front of the pass remained relatively stable. In other words, bathymetric expression of the ebb-tidal delta did not develop solely through progradation, but was also formed through erosion of the surrounding Gulf bottom. Accordingly, the shoal is termed ebb-tidal delta retreat body.

Howard, P.C.

1983-09-01

310

Hydrology of Salt Wells Creek : a plains stream in southwestern Wyoming  

USGS Publications Warehouse

Development of energy minerals in plains areas of Wyoming is expanding rapidly. Such development may affect water resources and hydrologic relations of the plains; however, little information exists concerning hydrologic processes for these areas. This report summarizes results of a hydrologic study made during 1975-78 of Salt Wells creek, a drainage area of about 500 square miles located southeast of Rock Springs, Wyoming. The area is typical of arid and semiarid plains areas in southwestern Wyoming where mineral development is occurring. Salt Wells Creek is predominately an intermittent stream. Numerous springs in the headwaters cause small perennial flows in some upstream tributaries, but evaporation, freezeup, and seepage deplete these flows so that the middle and lower reaches of the main channel have only intermittent flows. The intermittent nature of streamflow affects water quality. It was observed that a flushing of dissolved solids and suspended sediment occurs during the first flows of a runoff event. A striking feature of the stream is its deeply incised channel. The downcutting is attributed to the cummulative effects of: (1) a change in the relative climate, amounts of annual precipitation occurring as rain and snow, (2) change in base level due to downstream channelization, and (3) changes in land use. Because of the incision, erosion is now expanding to include intervening tributaries. (USGS)

Lowham, H.W.; DeLong, L.L.; Collier, K.R.; Zimmerman, E.A.

1982-01-01

311

Mid-Pliocene to Recent abyssal current flow along the Antarctic Peninsula: Results from ODP Leg 178, Site 1101  

E-print Network

the Weddell Sea Deep Water, for the past 3 Ma. Sediment grain size and magnetic fabric analyses indicate of the circulation circuit and resulting in a transfer of heat, salt and nutrients around the globe. The Antarctic; Pudsey, 2001) which follows the bathymetric contours along the continental shelf and slope, affects

312

Indian Peoples of the Northern Great Plains  

NSDL National Science Digital Library

Created with grant support from the Institute of Museum and Library Services National Leadership Grant Program, this online database highlights the photographic and visual record of current and former Indian groups from the Northern Great Plains. Housed at Montana State University, this particular online collection was designed to provide students, researchers, and the general public with direct access to valuable primary source material on Plains Indian cultures. The general organization of the site's archival materials is by tribe, but there are several themed collections, including one of Blackfeet tipis. The search options are quite impressive, as users can search by subject, date, location, tribe, and artist or photographer, along with further refining each search by looking by the geographical location of where the item is currently held.

1998-01-01

313

High-resolution seismic images of potentially seismogenic structures beneath the northwest Canterbury Plains, New Zealand  

NASA Astrophysics Data System (ADS)

The transpressional boundary between the Australian and Pacific plates in the central South Island of New Zealand comprises the Alpine Fault and a broad region of distributed strain concentrated in the Southern Alps but encompassing regions further to the east, including the northwest Canterbury Plains. Low to moderate levels of seismicity (e.g., 2 > M 5 events since 1974 and 2 > M 4.0 in 2009) and Holocene sediments offset or disrupted along rare exposed active fault segments are evidence for ongoing tectonism in the northwest plains, the surface topography of which is remarkably flat and even. Because the geology underlying the late Quaternary alluvial fan deposits that carpet most of the plains is not established, the detailed tectonic evolution of this region and the potential for larger earthquakes is only poorly understood. To address these issues, we have processed and interpreted high-resolution (2.5 m subsurface sampling interval) seismic data acquired along lines strategically located relative to extensive rock exposures to the north, west, and southwest and rare exposures to the east. Geological information provided by these rock exposures offer important constraints on the interpretation of the seismic data. The processed seismic reflection sections image a variably thick layer of generally undisturbed younger (i.e., < 24 ka) Quaternary alluvial sediments unconformably overlying an older (>59 ka) Quaternary sedimentary sequence that shows evidence of moderate faulting and folding during and subsequent to deposition. These Quaternary units are in unconformable contact with Late Cretaceous-Tertiary interbedded sedimentary and volcanic rocks that are highly faulted, folded, and tilted. The lowest imaged unit is largely reflection-free Permian - Triassic basement rocks. Quaternary-age deformation has affected all the rocks underlying the younger alluvial sediments, and there is evidence for ongoing deformation. Eight primary and numerous secondary faults as well as a major anticlinal fold are revealed on the seismic sections. Folded sedimentary and volcanic units are observed in the hanging walls and footwalls of most faults. Five of the primary faults represent plausible extensions of mapped faults, three of which are active. The major anticlinal fold is the probable continuation of known active structure. A magnitude 7.1 earthquake occurred on 4 September 2010 near the southeastern edge of our study area. This predominantly right-lateral strike-slip event and numerous aftershocks (ten with magnitudes ?5 within one week of the main event) highlight the primary message of our paper: that the generally flat and topographically featureless Canterbury Plains is underlain by a network of active faults that have the potential to generate significant earthquakes.

Dorn, C.; Green, A. G.; Jongens, R.; Carpentier, S.; Kaiser, A. E.; Campbell, F.; Horstmeyer, H.; Campbell, J.; Finnemore, M.; Pettinga, J.

2010-11-01

314

Messages from the Abyss  

NASA Astrophysics Data System (ADS)

VLT Observes Infrared Flares from Black Hole at Galactic Centre [1] Summary An international team of astronomers led by researchers at the Max-Planck Institute for Extraterrestrial Physics (MPE) in Garching (Germany) [2] has discovered powerful infrared flares from the supermassive black hole at the heart of the Milky Way . The signals, rapidly flickering on a scale of minutes, must come from hot gas falling into the black hole, just before it disappears below the "event horizon" of the monster. The new observations strongly suggest that the Galactic Centre black hole rotates rapidly . Never before have scientists been able to study phenomena in the immediate neighbourhood of a black hole in such a detail. The new result is based on observations obtained with the NACO Adaptive Optics instrument on the 8.2-m VLT YEPUN telescope and is published in this week's edition of the research journal Nature. PR Photo 29a/03 : A powerful flare from the black hole at the galactic centre. PR Photo 29b/03 : Light curve of the flare . PR Video 01/03 : A powerful flare from the black hole at the galactic centre . Flashes of light from disappearing matter ESO PR Photo 29a/03 ESO PR Photo 29a/03 [Preview - JPEG: 650 x 400 pix - 118k [Normal - JPEG: 1300 x 800 pix - 370k] ESO PR Video Clip 01/03 [MPEG] ESO PR Video Clip 01/03 [MPEG Video; 29X k] Captions : PR Photo 29a/03 and PR Video Clip 01/03 show the detection of a powerful flare from the centre of the Milky Way galaxy. These and other adaptive optics (AO) images (with resolution 0.040 arcsec in the near-infrared H-band at wavelength 1.65 µm) of the central region of the Milky Way were obtained with the NACO imager on the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory on May 9, 2003. The image covers a sky area of about 1 x 1 arcsec, corresponding to about 45 light-days at the distance of the Galactic Centre. The time (in minutes from the beginning of the data set at 6h59m24s (UT) on May 9, 2003) is shown at the upper right of each image. North is up and East to the left. The position of the 15-year orbiting star S2 (cf. ESO Press Release 17/02 ) is marked by a cross and the astrometric location of the black hole is indicated by a circle. The scene was the usual one in the VLT Control Room at the Paranal Observatory in the early morning of May 9, 2003. Groups of astronomers from different nations were sitting in front of the computer screens, pointing the four giant telescopes in different directions and recording the sparse photons from the remotest corners of the Universe. There were the usual brief exchanges of information, numbers, wavelengths, strange acronyms, but then suddenly something happened at the YEPUN desk.... " What is that star doing there? " exclaimed Rainer Schödel , one of the MPE scientists in the team working with the NACO Adaptive Optics instrument [3] that delivers razor-sharp images. He and Reinhard Genzel, leader of the team and MPE Director, were observing the Milky Way Centre, when they saw the "new" object on the screen in front of them. The astronomers were puzzled and then became excited - something unusual must be going on, there at the centre of our galaxy! And then, a few minutes later, the "star" disappeared from view. Now the scientists had little doubt - they had just witnessed, for the first time, a powerful near-infrared flare from exactly the direction of the supermassive black hole at the heart of the Milky Way , cf. PR Photo 29a/03 and PR Video Clip 01/03 . " We had been looking for infrared emission from that black hole for more than a decade " recalls another team member, Andreas Eckart of the Cologne University. " We were certain that the black hole must be accreting matter from time to time. As this matter falls towards the surface of the black hole, it gets hotter and hotter and starts emitting infrared radiation ". But no such infrared radiation had been seen until that night at the VLT. This was the wonderful moment of breakthrough. Never before had anybody witnessed t

2003-10-01

315

PIPING PLOVER SURVIVAL IN THE GREAT PLAINS  

Microsoft Academic Search

Survival was estimated for the Great Plains population of the threatened\\/en- dangered Piping Plover (Charadrius melodus) from resightings of 352 (214 adult, 138 juvenile) uniquely color-banded individuals in 1984-1990. One hundred one (47.2%) adults and 19 (13.8%) juveniles returned to the North Dakota study site in years after banding. Low return rates of juveniles precluded estimation of survival for that

BRIAN G. ROOT; MARK R. RYAN; PAUL M. MAYER

316

Candidate Mud Volcanoes in the Northern Plains of Mars  

NASA Astrophysics Data System (ADS)

Domes in the the `Borealis back-basin' (centre 76N 160W) on Mars resemble products of mud volcanism (MV) on Earth. Description of domes: Our mapping shows ~30 Early Amazonian domes in the back-basin (~50 x 40 km, height ~300 m). Many have marginal and central peaks (~7 x 5 km, height ~400 m), and moats ~2.5 km wide. Domes are rough at km-scale; some have central depressions; some have annular ridges. Mean rise/run is (0.93±0.22)%. Dome orientations, and alignments of multiple domes, run parallel to the continuation of grabens associated with Alba Patera diking [1]. Distributary channels are found in association with one dome. Aspect-frequency plots for the domes region show significant deviations from randomness. (Detrended) slopes facing S or N are more common than other aspects; local maxima are (S±5°) and (N±5°). N-facing slopes are more abundant than S-facing slopes, so mean S- facing slope must be steeper. A control region at the same latitude shows no comparable anomaly. Interpretation: Many worlds show igneous volcanism, but only Earth has confirmed MV. So, when assessing an extraterrestrial construct, one should assign a high prior probability to igneous volcanism. However, (1) Dome morphologies can be matched with MV in the Caspian Basin and Cadiz Gulf [2], though Martian domes have diameters ~5 times greater. (2) Moat morphometry excludes flexural origin and suggests a collapse origin. Collapse moats are often associated with MV on Earth. (3) Aspect anomalies suggest that near-surface dome material was subject to insolation-driven processing, requiring dome near-surface material to have been partially volatile [3]. (4) Volcanic constructs are rare closer to Alba Patera, inferred to have triggered dome construction. So there must be a major increase in the fusibility of materials in our basin. In the absence of Martian granites, volatile-rich deposits satisfy this requirement. (5) Mars' thick sediment piles permit MV. Crater fill studies suggest that the Scandia and Borealis back- basins contain the greatest thickness of cover in the Northern Plains, making these preferred MV locations [4]. We infer that domes may well result from MV. Outstanding puzzles: We currently lack a compelling mechanism for expulsion in the extensional tectonic setting required for dyking. One possibility is direct triggering of MV through intersection of dyke fluids with a volatile-rich sediment column. OMEGA spectra of domes show no significant differences between dome and non-dome terrain. Band depth methods and linear unmixing models [5] yield compositions uniformly dominated by ferric oxides and pyroxenes. This may be due to recent mantling, or MV may tap a source layer of similar composition to adjacent plains. Implications: Post-Hesperian cover in our study area is too thin for MV; older sediments are probably the source. These may record catastrophic flooding or oceans. Our results have implications for the ease of future drill-rig access to these ancient deposits. There is also a tempting geographic link with young evaporates [6]. [1] K.L.Tanaka (2006), 4th Mars Polar Sci., Abs. #8024. [2]L.Somoza et al. (2003), Mar. Geol. 195, doi:10.1016/S0025-3227(02)00686-2. [3] M.A.Kreslavsky and J.W.Head (2003),GRL 30, doi:10.1029/2003GL017795. [4] D.Buczkowski(2007),JGR-E, doi:10.1029/2006JE002836. [5] J.- P.Combe(2005),PhD thesis, U. Nantes. [6] K.E.Fishbaugh et al.(2007),JGR-E 112, doi:10.1029/2006JE00286.

Kite, E. S.; Hovius, N.; Hillier, J. K.; Besserer, J.

2007-12-01

317

Modeling sediment accumulation in North American playa wetlands in response to climate change, 1940-2100  

USGS Publications Warehouse

Playa wetlands on the west-central Great Plains of North America are vulnerable to sediment infilling from upland agriculture, putting at risk several important ecosystem services as well as essential habitats and food resources of diverse wetland-dependent biota. Climate predictions for this semi-arid area indicate reduced precipitation which may alter rates of erosion, runoff, and sedimentation of playas. We forecasted erosion rates, sediment depths, and resultant playa wetland depths across the west-central Great Plains and examined the relative roles of land use context and projected changes in precipitation in the sedimentation process. We estimated erosion with the Revised Universal Soil Loss Equation (RUSLE) using historic values and downscaled precipitation predictions from three general circulation models and three emissions scenarios. We calibrated RUSLE results using field sediment measurements. RUSLE is appealing for regional scale modeling because it uses climate forecasts with monthly resolution and other widely available values including soil texture, slope and land use. Sediment accumulation rates will continue near historic levels through 2070 and will be sufficient to cause most playas (if not already filled) to fill with sediment within the next 100 years in the absence of mitigation. Land use surrounding the playa, whether grassland or tilled cropland, is more influential in sediment accumulation than climate-driven precipitation change.

Burris, Lucy; Skagen, Susan K.

2013-01-01

318

Simplified Micromechanics of Plain Weave Composites  

NASA Technical Reports Server (NTRS)

A micromechanics based methodology to simulate the complete hygro-thermomechanical behavior of plain weave composites is developed. This methodology is based on micromechanics and the classical laminate theory. The methodology predicts a complete set of thermal, hygral and mechanical properties of plain woven composites, generates necessary data for use in a finite element structural analysis, and predicts stresses all the way from the laminate to the constituent level. This methodology is used in conjunction with a composite mechanics code to analyze and predict the properties/response of a generic graphite/epoxy woven textile composite and a plain weave ceramic composite. The fiber architecture, including the fiber waviness and fiber end distributions through the thickness, is properly accounted for. Predicted results compare reasonably well with those from detailed three-dimensional finite element analyses as well as available experimental data. However, the main advantage of the proposed methodology is its high computational efficiency as compared with three-dimensional finite element analyses.

Mital, Subodh K.; Murthy, Pappu L. N.; Chamis, Christos C.

1996-01-01

319

Flood plain stability of the Peace River, southwestern Florida, since the last glacial lowstand of sea level  

SciTech Connect

The 186 km long Peace River heads in the Central Highlands, dissects marine terraces of the Coastal Lowlands, and flows into the Gulf of Mexico. Between river kms 80 and 137 the gradient is low (0.1 to 0.3 m/km), sinuosity is moderate (1.2 to 1.8), and the flood plain is wide (0.6 to 2.5 km). The flood plain is underlain by a well-sorted fine/very fine-grained quartz sand overbank deposit. This overlies crossbedded and rippled, medium/coarse-grained quartz and phosphatic sand channel deposits, organic-rich loamy sand channel-fill deposits, and/or non-fluvial strata. Radiocarbon dates of organics in channel deposits at two sites 57 km apart indicate that aggradation of the flood plain was in progress by 24,760 [plus minus] 920 (Wauchula) and 21,870 [plus minus] 130 (Arcadia) years B.P. during a lowstand of sea level. Well-developed soils in the overlying fine sand have accumulated 12% and 9% clay respectively, indicating that the flood-plain surface has been stable for a considerable portion of the 22,000 years since deposition began. Between dated sites, soils are developed in nearly identical parent material with less, but varying degrees of development and clay accumulation, suggesting that other portions of the flood plain surface are younger. Because of the very low river gradient, both during lowstands and highstands of sea level, the Peace River cannot easily aggrade or degrade. It slowly reworks its flood-plain sediment resulting in a variety of soil development and surface ages on a single geomorphic surface.

Guccione, M.J. (Univ. of Arkansas, Fayetteville, AR (United States). Geology Dept.)

1993-03-01

320

[Profile nutrient distribution and sedimentary characteristics in typical marshes of Sanjiang Plain].  

PubMed

Profile distribution characteristics of organic carbon (C), total nitrogen (N), total phosphorus (P) and total sulfur (S) were studied in two typical marshes including Carex lasiocarpa marsh and Phragmites australis marsh in the Sanjiang Plain. Sedimentary characteristics of typical mashes were analyzed. The results showed that vertically these soil chemical elements also varied, showing obvious stratification and enrichment. In a soil profile, soil organic C under both vegetation communities gradually decreased; soil total N first increased and then decreased under both; total P under Carex lasiocarpa first decreased and then increased, whereas it decreased with the increasing depth under Carex lasiocarpa; total S was reduced with increasing depth under both marshes. Total N, total P and total S were all strongly correlated with soil organic C (P < 0.01); soil organic C was strongly correlated with bulk density (P < 0.01). Our study also illustrated that the vegetation types had different influences for organic C, total N, total P and total S of the marsh profiles. Environmental 137Cs and 210Pb dating techniques were applied to determine recent sedimentation rates, and the constant rate of supply (CRS) was applied to deduce the age of sediment core, and the results showed that the mean sedimentation rate was 0.33 cm x a(-1), and the sedimentation fluxes ranged 0.03-0.48 g x (cm2 x a)(-1) [Mean = 0.29 g x (cm2 x a) -1]. PMID:25338362

Li, Rui-Li; Chai, Min-Wei; Qiu, Guo-Yu; Shi, Fu-Chen; Sasa, Kaichiro

2014-08-01

321

Distribution and characteristics of arsenic in the geochemical environment of Chianan plain in Taiwan  

NASA Astrophysics Data System (ADS)

Blackfoot disease associated with the direct ingestion of high As content groundwater was first reported in the Chianan plain of southwestern Taiwan. However, both the geochemistry of high As groundwater and the possible As release mechanisms in this area are still poorly defined. The objectives of the study are to characterizes the As-affected groundwater of the Chianan plain by multivariate statistical method and geochemical model, PHREEQC, and to identify the source of As and possible geochemical reactions by chemical, spectroscopic, and microscopic approaches of solid phases. A conceptual geochemical cycling in the Chianan plain will be proposed. The controlling factors of this groundwater quality determined by factor analysis are salinization factor and the As enrichment factor. The latter is based on well correlation between As, reductive potential, organic and inorganic carbon. Si, Al and Fe are the main components of sediment materials. Arsenic concentrations correlate well with S and Fe contents in sediment. The primary Fe minerals are Fe oxy-hydroxides and iron disulfide. According to the results of sequential extraction, >90% of As contents is related to coprecipitation with iron sulfides, amorphous and crystalline Fe oxy-hydroxides, and adsorption of bicarbonate. Two most possible geochemical process of As release to groundwater are reductive dissolution of As-rich Fe oxy-hydroxides and microbial-mediated oxidation of As-bearing Fe sulfide minerals. Under reductive condition, low Eh causes the dissolution of Fe oxy-hydroxides and reduction of sulfate to sulfide. Over-pumping introduces excess dissolved oxygen to first oxidize As-bearing sulfide minerals, release As and then gradually re-precipitated as As-coated Fe minerals. The result provides valuable information for utilization and management of As-affected groundwater resources.

Wang, S. W.; Liu, C. W.; Lai, C. C.; Lin, K. H.

2009-04-01

322

Evolution of the Gulf of Alaska coastal plain: Cape Suckling to Icy Point  

SciTech Connect

The Gulf of Alaska coastline, coastal plain, and adjacent continental margin between Cape Suckling and Icy Point is located on the leading edge of the northwestward moving Pacific Plate. Although dominated by intensive wind and wave erosion, this coastal region is accretionary. This apparent contradiction results from the ongoing combination of aperiodic seismic uplift and long-term tectonic uplift raising new shoreline areas which are immediately attacked by erosion. If the hiatus between episodes of successive uplift is short, then a segment of the uplifted area is preserved as a coastal plain ridge. About one-half of the almost 500 km long coastal area has a ridge cover. Near the Alsek River and west of Cape Yakataga, as many as 20 distinct parallel ridges exist. All are younger than 3000 radiocarbon years old. Approximately 4000 years ago, as eustatic sea level reached present level, there was no coastal plain. Rather, the Pacific Ocean covered a deep, glacially-scoured bedrock shelf and reached directly to the foot of the coast mountains. Rivers draining onto the continental shelf had to fill fiords and shelf basins before a continental shelf sediment wedge developed. Only in the past 2000-3000 years has the wedge projected above sea level. Once this occurred, the combination of seismicity and tectonics began the ridge building process. This combination of processes has produced an extremely young, very dynamic, changing coastline and coastal plain. As evidence of its youthfulness, the two largest ridge complexes adjacent to the coastline were too young to date by radiocarbon methods.

Molnia, B.F.

1985-01-01

323

Sources of suspended-sediment flux in streams of the chesapeake bay watershed: A regional application of the sparrow model  

USGS Publications Warehouse

We describe the sources and transport of fluvial suspended sediment in nontidal streams of the Chesapeake Bay watershed and vicinity. We applied SPAtially Referenced Regressions on Watershed attributes, which spatially correlates estimated mean annual flux of suspended sediment in nontidal streams with sources of suspended sediment and transport factors. According to our model, urban development generates on average the greatest amount of suspended sediment per unit area (3,928 Mg/km2/year), although agriculture is much more widespread and is the greatest overall source of suspended sediment (57 Mg/km2/year). Factors affecting sediment transport from uplands to streams include mean basin slope, reservoirs, physiography, and soil permeability. On average, 59% of upland suspended sediment generated is temporarily stored along large rivers draining the Coastal Plain or in reservoirs throughout the watershed. Applying erosion and sediment controls from agriculture and urban development in areas of the northern Piedmont close to the upper Bay, where the combined effects of watershed characteristics on sediment transport have the greatest influence may be most helpful in mitigating sedimentation in the bay and its tributaries. Stream restoration efforts addressing floodplain and bank stabilization and incision may be more effective in smaller, headwater streams outside of the Coastal Plain. ?? 2010 American Water Resources Association. No claim to original U.S. government works.

Brakebill, J.W.; Ator, S.W.; Schwarz, G.E.

2010-01-01

324

Venus Ovda Regio Stratigraphy and Tectonics: Highlands-Plains Relationships  

NASA Astrophysics Data System (ADS)

The global plains materials of the Venusian lowlands, generally interpreted to be composed of flood basalts, lap onto the equatorial highlands of Western Aphrodite Regio. Systematic geologic mapping of the Ovda region using the Magellan global data (radar images, altimetry and gravity) has revealed that the contacts between highlands and plains have been tilted up toward the highlands after the plains emplacement. Analysis of the western part of Ovda Regio shows that the northern contact occurs at an average radius of 6053.8 km and the mean plains elevation 500 km to the north of the contact is at a radius of 6052.0 km, indicating that the boundary position has changed by nearly 2 km. Volcanic rilles are superposed on the tilted plains surfaces along both the northern and southern boundaries of the Ovda highlands. The local volcanicity that cut the rilles indicates that some local volcanic activity occurred subsequent to the marginal uplift. Models under study include post plains-emplacement uplift of the highlands or relative sinking of the plains. Isostatic mechanisms are likely in either case. Although complex structural models for the plains-highland margin are possible, simple structural models in which plains were emplaced as a nearly level geoidal surface and subsequently the highlands of Ovda were uplifted relative to the plains. Initial mapping is focused on 1:5,000,000 scale and is integrating observations of surface characteristics and geophysical inferences drawn from topography and gravity.

Saunders, R. S.

1996-03-01

325

Fate of sediments delivered to the sea by Asian large rivers: Long-distance transport and formation of remote alongshore clinothems  

Microsoft Academic Search

Recent studies show that the global flux of river-derived sediment reaching the coasts and oceans is about 15-19 x 109 tons per year. New sediment budgets for the major Asian river systems (e.g.,Yellow, Yangtze, Mekong, Ganges-Brahmaputra, etc.) suggest that 30-50% of their sediment load has been retained in the lower channel reaches to form an extensive subaerial delta plain, while

J. P. Liu; Z. Xue; K. Ross; Z. S. Yang; S. Gao

2009-01-01

326

Characteristics and origin of Earth-mounds on the Eastern Snake River Plain, Idaho  

SciTech Connect

Earth-mounds are common features on the Eastern Snake River Plain, Idaho. The mounds are typically round or oval in plan view, <0.5 m in height, and from 8 to 14 m in diameter. They are found on flat and sloped surfaces, and appear less frequently in lowland areas. The mounds have formed on deposits of multiple sedimentary environments. Those studied included alluvial gravel terraces along the Big Lost River (late Pleistocene/early Holocene age), alluvial fan segments on the flanks of the Lost River Range (Bull Lake and Pinedale age equivalents), and loess/slopewash sediments overlying basalt flows. Backhoe trenches were dug to allow characterization of stratigraphy and soil development. Each mound has features unique to the depositional and pedogenic history of the site; however, there are common elements to all mounds that are linked to the history of mound formation. Each mound has a {open_quotes}floor{close_quotes} of a sediment or basement rock of significantly different hydraulic conductivity than the overlying sediment. These paleosurfaces are overlain by finer-grained sediments, typically loess or flood-overbank deposits. Mounds formed in environments where a sufficient thickness of fine-grained sediment held pore water in a system open to the migration to a freezing front. Heaving of the sediment occurred by the growth of ice lenses. Mound formation occurred at the end of the Late Pleistocene or early in the Holocene, and was followed by pedogenesis. Soils in the mounds were subsequently altered by bioturbation, buried by eolian deposition, and eroded by slopewash runoff. These secondary processes played a significant role in maintaining or increasing the mound/intermound relief.

Tullis, J.A.

1995-09-01

327

Silicon flux and distribution of biogenic silica in deep-sea sediments in the western North Pacific Ocean  

NASA Astrophysics Data System (ADS)

We investigated biogenic silica, several biological components, and silicate in pore-water in the abyssal sediment to determine silicon flux of western North Pacific during several cruises. The surficial sediment biogenic silica content was high at high latitudes with the boundary running along the Kuroshio Extension, and maximum values (exceeding 20%) were found in the Oyashio region. In the subtropical region to the south, most stations showed less than 5% biogenic silica content. This distribution pattern reflected primary production and ocean currents in the surface layer very well. Pore-water samples were collected from 4 stations along the east coast of Japan. The highest asymptotic silicic acid concentration (670 ?mol L -1) in pore-water was observed at the junction of Kuroshio and Oyashio, followed by samples from the Oyashio region. It is at the southern station that the lowest value (450 ?mol L -1) was observed, and the primary production is low under the influence of Kuroshio there. The diffusive flux followed the same geographic trend as the asymptotic silicic acid concentrations did, ranging 77-389 mmol m -2 yr -1. Multiple sampling of pore-water was conducted throughout the year at one station at high latitude. The average annual biogenic silica rain flux observed using sediment traps was 373 mmol m -2 yr -1; the diffusive flux and burial flux at the sediment-water interface were 305 and 9 mmol m -2 yr -1, respectively. We concluded that most of the settling silica particles dissolved and diffused at the sediment-water interface and approximately 3% only were preserved in this area. In addition, the obvious time lag observed between the peak rain flux and the maximum diffusive flux suggested that primary production in the surface layer has a great influence on the sedimentation environment of abyssal western North Pacific. These transitions of Si flux at the sediment-water interface were considerably greater in northwestern North Pacific than in southwestern North Pacific. In addition, a station in the Philippine Sea indicated high biogenic silica content because of Ethmodiscus ooze, which are scattered randomly on the sea floor in the subtropical region.

Shibamoto, Yoko; Harada, Koh

2010-02-01

328

Food quality determines sediment community responses to marine vs. terrigenous organic matter in a submarine canyon  

NASA Astrophysics Data System (ADS)

The Whittard canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard canyon testing short term (3-7 day) responses of sediment communities to deposition of nitrogen-rich marine (Thallassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13C and 15N labels were traced into faunal biomass and bulk sediments, and the 13C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest, in the western branch of the Whittard canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0-1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal-bacterial interactions influence benthic C cycling in the Whittard canyon, resulting in differential fates for marine and terrigenous OM.

Hunter, W. R.; Jamieson, A.; Huvenne, V. A. I.; Witte, U.

2012-08-01

329

Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon  

NASA Astrophysics Data System (ADS)

The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3-7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13C and 15N labels were traced into faunal biomass and bulk sediments, and the 13C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0-1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal-bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.

Hunter, W. R.; Jamieson, A.; Huvenne, V. A. I.; Witte, U.

2013-01-01

330

Trace metal distributions in the uppermost sediments of the Black Sea: A metalliferous black shale analog  

SciTech Connect

Box-core sediment samples were collected from a broad range of depositional settings including both oxic and anoxic/sulfidic sites. Within the context of a broader study, a systematic assessment of Mn and Fe distributions was performed for the full spectrum of uppermost Holocene sediment types. Additionally, a representative data set for Ti, Cr, Co, Ni, Cu and Zn was generated with the intent of evaluating the Black Sea Model as a viable analog for metal-rich shales of the stratigraphic record. With only a few noteworthy exceptions, metal concentrations throughout the surficial sediments of the basin occur at levels comparable to or below their average crustal abundancies and their concentrations in several widely used non-metalliferous shale standards. The coccolith-rich, microlaminated sediments of the abyssal floor reveal the highest levels of organic C and are the most likely candidate for a modern black shale within the uppermost sediment layers. Nevertheless, the deposits display, at best, only two fold enrichments in Co, Ni, Cu and Zn relative to crustal distributions and other Black Sea sediment types. The most-anomalous Mn and Fe enrichments found were below the surface layers in two cores from the Bosporus region. These subsurface maxima are believed to record an intersection of the water column Fe-Mn redox-boundary particle maximum with the outer-shelf bottom during a past chemocline shoaling event. Careful down-core and intersite comparisons suggest that coprecipitation with Mn and Fe oxyhydroxides may be important in controlling the distributions of the less abundant metals. Additional mechanistic details will be provided, including an emphasis on redox controls, organic affinities and metal-sulfide precipitation. However, the dramatic enrichments in Ti, Cr, Co, Ni, Cu and Zn reported from ancient metal-rich shales cannot readily be explained by magnitudes of processes currently operating in the modern Black Sea.

Lyons, T.W.; Huston, T.J. (Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Geological Sciences)

1992-01-01

331

Holocene and late glacial palaeoceanography and palaeolimnology of the Black Sea: Changing sediment provenance and basin hydrography over the past 20,000years  

USGS Publications Warehouse

The elemental geochemistry of Late Pleistocene and Holocene sediments of the Black Sea, recovered in box cores from the basin margins and a 5-m gravity core from the central abyssal region of the basin, identifies two terrigenous sediment sources over the last 20. kyrs. One source region includes Anatolia and the southern Caucasus; the second region is the area drained by rivers entering the Black Sea from Eastern Europe. Alkali metal:Al and heavy:light rare-earth element ratios reveal that the relative contribution of the two sources shifted abruptly every few thousand years during the late glacial and early Holocene lacustrine phase of the basin. The shifts in source were coeval with changes in the lake level as determined from the distribution of quartz and the heavy mineral-hosted trace elements Ti and Zr. The geochemistry of the abyssal sediments further recorded a sequence of changes to the geochemistry of the water column following the lacustrine phase, when high salinity Mediterranean water entered the basin beginning 9.3. kyrs BP. Bottom water that had been oxic throughout the lake phase became anoxic at approximately 8.4. kyrs BP, as recorded by the accumulation from the water column of several redox-sensitive trace metals (Mo, Re, U). The accumulation of organic carbon and several trace nutrients (Cd, Cu, Ni, Zn) increased sharply ca. 0.4. kyrs later, at 8.0. kyrs BP, reflecting an increase of primary productivity. Its increase was coeval with a shift in the dinoflagellate ecology from stenohaline to euryhaline assemblages. During this profound environmental change from the lacustrine to the marine phase, the accumulation rate of the lithogenous sediment fraction decreased as much as 10-fold in response to the rise of the water level in the basin from a low stand ca. 9.3. ka to its current level. ?? 2011.

Piper, D.Z.; Calvert, S.E.

2011-01-01

332

Activities about Sediments  

NSDL National Science Digital Library

This series of activities will allow students to learn more about sediments and develop their skills in using a variety of strategies to study our planet. The activities include using a stereomicroscope to view tiny sediment grains, finding their actual sizes by comparing them with the scope's field of view, separating a sediment sample using a set of sieves, and preparing bar graphs representing the grain size distribution of the sediment. The site also includes instructions for a proper lab write-up.

Passow, Michael

333

Impact crater degradation on venusian plains  

NASA Astrophysics Data System (ADS)

In venusian plains, impact craters without extensive low backscatter ejecta deposits are more likely to have low backscatter floors, be embayed by volcanic deposits, and exhibit fractures as compared to craters with extensive low backscatter ejecta. We interpret these trends as evidence of ongoing degradation of low backscatter ejecta by aeolian activity, weathering, and volcanism. Using a crater age sequence based on extent of preservation of low backscatter ejecta, together with Monte Carlo simulations, we find that tectonic activity has extended over a longer time period than volcanism.

Izenberg, N. R.; Arvidson, R. E.; Phillips, R. J.

1994-02-01

334

Environmental perceptions in Great Plains novels  

E-print Network

environment. The physical environment is given a central role in Plains novels, and characters are shown to be aware of the environment's significance in their lives as they establish farms, ranches, and communities in the "untamed" land. When perceptual... is that it offer s an in-depth portrayal of the settlement experiences of one family, and a personal view of man-land relationships that cannot be obtained from nonfiction ac- counts; in this way the novel makes a valuable contribution to a cultural, historical...

Pardee, Celeste Frances

2012-06-07

335

COMPUTATION OF RESERVOIRS SEDIMENTATION  

Microsoft Academic Search

Methods for the computation of sedimentation by suspended sediments and bed load of the projected reservoirs are given, or the first year Of the reservoir operation computation is made according to the balance of sediments computed by the difference between the transport capacity and the hydraulic parameters of the current at the upper pool (transient region) and at the dan

A. V. Karaushev; I. V. Bogoliubova

336

A Sustainable Agro-ecological Solution to Water Shortage in the North China Plain (Huabei Plain)  

Microsoft Academic Search

A highly seasonal rainfall pattern in the agriculturally productive region of Huabei Plain has been widely considered in China as a handicap to maximizing agricultural production. Enhancing this perception is the traditional policy of achieving provincial or regional self-sufficiency in grain production, which underlies China's production quotas. The Chinese government has decided to overcome this perceived handicap in order to

Shu Geng; Yixing Zhou; Minghua Zhang; K. Shawn Smallwood

2001-01-01

337

Sulfur isotope and porewater geochemistry of Florida escarpment seep sediments  

USGS Publications Warehouse

Distributions of porewater constituents, SO4=, NH4+, Cl-, ???CO2, and H2S, solid phase iron, and sulfur concentrations, and the sulfur isotopic composition of dissolved and solid phases were investigated in sediments from abyssal seeps at the base of the Florida escarpment. Despite the apparent similarity of seep sediment porewater chemistry to that of typical marine sediments undergoing early diagenesis, relationships between chemical distributions and isotopic measurements revealed that the distribution of pore fluid constituents was dominated by processes occurring within the platform rather than by in situ microbial processes. Ammonium and sulfate concentrations were linearly correlated with chloride concentrations, indicating that variations in porewater chemistry were controlled by the admixture of seawater and a sulfate depleted brine with a chlorinity of 27.5 ?? 1.9%. and 2.2 ?? 1.3 mM ammonium concentration. At sites dominated by seepage, dissolved sulfate isotopic composition remained near seawater values despite depletion in porewater concentrations. Porewater ???CO2 concentrations were found to be elevated relative to seawater, but not to the extent predicted from the observed sulfate depletion. Sediment solid phase sulfur was predominantly pyrite, at concentrations as high as 20% S by weight. In contrast to typical marine deposits, pyrite concentrations were not related to the quantity of sedimentary organic matter. Pyrite ??34S values ranged from -29%. to + 21%. (CDT). However, only positive ??34S values were observed at sites associated with high pyrite concentrations. Isotopically heavy pyrite was observed at sites with porewater sulfate of seawater-like isotopic composition. Isotopically light pyrite was associated with sites where porewater sulfate exhibited ??34S values greater than those in seawater, indicating the activity of in situ microbial sulfate reduction. Thus, dual sulfide sources are suggested to explain the range in sediment pyrite isotopic composition: a ??34S enriched (+10 to +20%.) source adverted from within the Florida platform, and a lighter 34S depleted component generated in situ from microbial reduction of seawater sulfate. The degree of pyritization of seep sediments was as high as 0.9 and was controlled by pyrite concentrations, which varied over a wider range than did the non-pyrite solid phase iron concentrations. The highest non-sulfide solid phase iron concentrations were observed in sediments that are believed to be at the "front" of the advancing seep fluids (i.e., hemipelagic sediments newly exposed to the seep fluids), indicating that dissolution of hemipelagic background sediment may be the source of at least half of the iron to the highly pyritized seep sediments. Porewater sulfide concentrations were variable, reaching a maximum of 5.7 mM, and were not correlated with the degree of pyritization of the sediments, suggesting that iron was not particularly limiting to pyrite formation. ?? 1993.

Chanton, J. P.; Martens, C. S.; Paull, C. K.; Coston, J. A.

1993-01-01

338

Fossil mollusc-faunas: Their bearing on the Holocene evolution of the Lower Central Plain of Bangkok (Thailand)  

NASA Astrophysics Data System (ADS)

In this work, fossil molluscan assemblages are analyzed in order to reconstruct the evolution of the Northern Gulf of Thailand during the Holocene. The marine sediments (Bangkok Clay Formation) of the Lower Central Plain of Bangkok and the coastal plain of Phetchaburi were sampled at 16 localities, obtaining fossil shells and mangrove peat whose 14C ages range from 9000 to 2000 CYBP. A statistical treatment of abundance data returned four major groups, namely the Dendostrea rosacea association (intertidal mud), the Corbula fortisulcata- Mactra luzonica association (shallow infralittoral sandy mud), the Nuculana mauritiana- Timoclea scabra association (infralittoral sand spit) and the Timoclea scabra- Arcopagia pudica association (infralittoral mud). The data allowed both a stratigraphic correlation along two transects covering all of the Holocene basin and the creation of digitalized maps showing the presumable extension of the Thai paleogulf around the apex of Flandrian transgression event (about 5500 CYBP).

Negri, Mauro Pietro

339

Microbial transformations of arsenic: mobilization from glauconitic sediments to water.  

PubMed

In the Inner Coastal Plain of New Jersey, arsenic (As) is released from glauconitic sediment to carbon- and nutrient-rich shallow groundwater. This As-rich groundwater discharges to a major area stream. We hypothesize that microbes play an active role in the mobilization of As from glauconitic subsurface sediments into groundwater in the Inner Coastal Plain of New Jersey. We have examined the potential impact of microbial activity on the mobilization of arsenic from subsurface sediments into the groundwater at a site on Crosswicks Creek in southern New Jersey. The As contents of sediments 33-90 cm below the streambed were found to range from 15 to 26.4 mg/kg, with siderite forming at depth. Groundwater beneath the streambed contains As at concentrations up to 89 ?g/L. Microcosms developed from site sediments released 23 ?g/L of As, and active microbial reduction of As(V) was observed in microcosms developed from site groundwater. DNA extracted from site sediments was amplified with primers for the 16S rRNA gene and the arsenate respiratory reductase gene, arrA, and indicated the presence of a diverse anaerobic microbial community, as well as the presence of potential arsenic-reducing bacteria. In addition, high iron (Fe) concentrations in groundwater and the presence of iron-reducing microbial genera suggests that Fe reduction in minerals may provide an additional mechanism for release of associated As, while arsenic-reducing microorganisms may serve to enhance the mobility of As in groundwater at this site. PMID:22494492

Mumford, Adam C; Barringer, Julia L; Benzel, William M; Reilly, Pamela A; Young, L Y

2012-06-01

340

Microbial transformations of arsenic: Mobilization from glauconitic sediments to water  

USGS Publications Warehouse

In the Inner Coastal Plain of New Jersey, arsenic (As) is released from glauconitic sediment to carbon- and nutrient-rich shallow groundwater. This As-rich groundwater discharges to a major area stream. We hypothesize that microbes play an active role in the mobilization of As from glauconitic subsurface sediments into groundwater in the Inner Coastal Plain of New Jersey. We have examined the potential impact of microbial activity on the mobilization of arsenic from subsurface sediments into the groundwater at a site on Crosswicks Creek in southern New Jersey. The As contents of sediments 33–90 cm below the streambed were found to range from 15 to 26.4 mg/kg, with siderite forming at depth. Groundwater beneath the streambed contains As at concentrations up to 89 ?g/L. Microcosms developed from site sediments released 23 ?g/L of As, and active microbial reduction of As(V) was observed in microcosms developed from site groundwater. DNA extracted from site sediments was amplified with primers for the 16S rRNA gene and the arsenate respiratory reductase gene, arrA, and indicated the presence of a diverse anaerobic microbial community, as well as the presence of potential arsenic-reducing bacteria. In addition, high iron (Fe) concentrations in groundwater and the presence of iron-reducing microbial genera suggests that Fe reduction in minerals may provide an additional mechanism for release of associated As, while arsenic-reducing microorganisms may serve to enhance the mobility of As in groundwater at this site.

Mumford, Adam C.; Barringer, Julia L.; Benzel, William M.; Reilly, Pamela A.; Young, L.Y.

2012-01-01

341

Distribution and origin of shallow gas in deep-sea sediments of the Ulleung Basin, East Sea (Sea of Japan)  

Microsoft Academic Search

A synthesis of high-resolution (Chirp, 2–7 kHz) subbottom profiles in the Ulleung Basin reveals patchy distribution of shallow\\u000a (<90 m subbottom depth) gassy sediments in the eastern basin plain below 1,800-m water depth. The shallow gases in the sediments\\u000a are associated with acoustic turbidities, columnar acoustic blankings, enhanced reflectors, dome structures, and pockmarks.\\u000a Analyses of gas samples collected from a

S. H. Lee; S. K. Chough

2002-01-01

342

Enigmatic Post-Glacial Degradation and Aggradation of Rivers on the Alberta Plains  

NASA Astrophysics Data System (ADS)

Rivers flowing eastward from the Canadian Rockies across the Alberta plains are situated in narrow flat-bottomed valleys on the order of 50 to 100 m below the plains surface. Post-Laurentide Ice Sheet river history is characterized by (a) incision into the general plains surface following deglaciation, (b) aggradation, soon thereafter, in which up to 25 m of alluvial fill was deposited in the new valleys, and (c) Holocene reincision into the fill, down to depths at least as great as those of the pre-fill valleys. This complicated history probably results from an interplay of (a) isostatic depression/ rebound, which is considered here using a Glacial Isostatic Adjustment model that incorporates the RF2 and RF3 earth models described by Wang et al. (2008) with the ICE4G deglaciation model of Peltier (1994), and (b) variations in sediment flux. The initial incision post-dates the retreat of the Laurentide Ice Sheet eastward across Alberta, ca. 14 ka, and pre-dates the ca. 11 ka alluvial fill. Incision cannot have resulted from general uplift provided by post-glacial isostatic rebound, because rebound was and is generally greater downstream where ice was thicker. Hence river gradients have generally decreased because of rebound. Incision more likely resulted from increased gradients provided by isostatic depression under the center of the ice sheet, relative to the plains gradient that would exist without ice effects. Temporary increased gradients on particular reaches of rivers were provided by the passage across Alberta of the slope of a peripheral bulge on the margin of the isostatic depression. However, some reaches of the rivers have orientations that preclude an obvious connection to bulge gradients. The switch from degradation to aggradation in early post-glacial time was proposed to be a result of decreasing river gradients due to rebound, by Kellerhals and Shaw (1982), but later considered to be a result of influx of paraglacial sediments from the Canadian Rockies by Jackson et al. (1982). Our model confirms that river gradients generally decreased through post-glacial time, favoring increased sediment deposition. However, the subsequent return to degradation cannot be explained by decreasing river gradients, so a pulse of paraglacial sedimentation must have been the primary cause of aggradation. The second episode of incision of rivers was underway by early Holocene time. We agree with Jackson et al. (1982) that the reincision resulted from decline of paraglacial sediment supply into the mountain headwaters of the rivers. Incision was episodic and resulted in a series of terraces, and there is some evidence for minor fill episodes punctuating the general downcutting. There are no obvious reasons for this erratic behavior, which may have resulted from instabilities inherent in the system. Jackson, L., MacDonald, G., Wilson, M., 1982, Canadian Jr. Earth Sci. 19:2219-2231. Kellerhals, R. and Shaw, J., 1982, Alberta Research Council Bulletin 41. Peltier, W., 1994, Science 265:195-201. Wang, H., Wu, P., Van der Wal, 2008, Jr. Geodynamics 46:104-117.

Malowany, K. S.; osborn, G.; Wu, P. P.

2011-12-01

343

Carbon, nitrogen, and phosphorus accumulation in floodplains of Atlantic Coastal Plain rivers, USA  

USGS Publications Warehouse

Net nutrient accumulation rates were measured in riverine floodplains of the Atlantic Coastal Plain in Virginia, Maryland, and Delaware, USA. The floodplains were located in watersheds with different land use and included two sites on the Chickahominy River (urban), one site on the Mattaponi River (forested), and five sites on the Pocomoke River (agricultural). The Pocomoke River floodplains lie along reaches with natural hydrogeomorphology and on reaches with restricted flooding due to channelization and levees. A network of feldspar clay marker horizons was placed on the sediment surface of each floodplain site 3-6 years prior to sampling. Sediment cores were collected from the material deposited over the feldspar clay pads. This overlying sediment was separated from the clay layer and then dried, weighed, and analyzed for its total carbon (C), nitrogen (N), and phosphorus (P) content. Mean C accumulation rates ranged from 61 to 212 g??m-2??yr-1, N accumulation rates ranged from 3.5 to 13.4 g??m -2??yr-1, and P accumulation rates ranged from 0.2 to 4.1 g??m-2??yr-1 among the eight floodplains. Patterns of intersite variation in mineral sediment and P accumulation rates were similar to each other, as was variation in organic sediment and C and N accumulation rates. The greatest sediment and C, N, and P accumulation rates were observed on Chickahominy River floodplains downstream from the growing metropolitan area of Richmond, Virginia. Nutrient accumulation rates were lowest on Pocomoke River floodplains that have been hydraulically disconnected from the main channel by channelization and levees. Sediment P concentrations and P accumulation rates were much greater on the hydraulically connected floodplain immediately downstream of the limit of channelization and dense chicken agriculture of the upper Pocomoke River watershed. These findings indicate that (1) watershed land use has a large effect on sediment and nutrient retention in floodplains, and (2) limiting the hydraulic connectivity between river channels and floodplains minimizes material retention by floodplains in fluvial hydroscapes. ?? 2005 by the Ecological Society of America.

Noe, G. B.; Hupp, C. R.

2005-01-01

344

Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA  

USGS Publications Warehouse

Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the B??lling-Aller??d episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial of both the Brady Soil and the Leonard Paleosol by renewed loess influx probably represents eolian system response that occurred when gradual change toward a drier climate eventually crossed the threshold for eolian activity. Overall, the loess-paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture across the late Pleistocene to Holocene boundary, rather than well-defined climatic episodes corresponding to the B??lling-Aller??d and Younger Dryas episodes in the North Atlantic region. ?? 2008 Elsevier Ltd. All rights reserved.

Mason, J.A.; Miao, X.; Hanson, P.R.; Johnson, W.C.; Jacobs, P.M.; Goble, R.J.

2008-01-01

345

Research perspectives of sediment waves and drifts: Monitors of global change in deepwater circulation  

NASA Astrophysics Data System (ADS)

The purpose of this special section in Paleoceanography is to present interdisciplinary approaches for contributing to the reconstruction of ocean circulation and its response to climate changes. A high-priority objective for understanding the causes and mechanisms of climate change is the monitoring of past ocean circulation and oceanic heat and nutrient transport. Lehman and Keigwin [1992] have shown that cooling, for example, during the younger Dryas event, may have culminated in a cessation of the oceans conveyor circulation. The cooling in the North Atlantic was apparently the result of reduced northward heat transport in the upper water masses of the North Atlantic conveyor belt. In contrast, intervals with a strong surface and deepwater circulation were marked by a high northward heat transport. For the understanding of the causes and the timing of such rapid,highfrequency events, marine records of high deposition ratecores are needed. These cores should provide evidence for changes in abyssal circulation and heat transport, as well as arecord of surface and deepwater characteristics. The sediment drifts of the North Atlantic and in other ocean basins are one of the major targets for the recovery of sediments with high deposition rates (>10 cm/kyr) and for reconstructing the role of both intermediate and deepwater production in the conveyor belt, that is drawing low-latitude heat northward. We stress the need for international programs targeting high deposition rate areas on sediment drifts and sediment waves in order to understand (1) the evolution of the conveyor belt and (2) its dynamics and variability. The North Atlantic, where sediment drifts are concentrated, will provide ideal study areas with time resolutions comparable to those of ice core records but with records linked directly to the record of changing bottom water flow. Therefore one can address the changes in circulation, heat and carbon budget on high and ultrahigh resolution records.

Mienert, J.; Flood, R. D.; Dullo, W. C.

1994-12-01

346

40 CFR 81.149 - Northern Coastal Plain Intrastate Air Quality Control Region.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Northern Coastal Plain Intrastate Air Quality Control...Control Regions § 81.149 Northern Coastal Plain Intrastate Air Quality Control Region. The Northern Coastal Plain Intrastate Air Quality...

2010-07-01

347

40 CFR 81.152 - Southern Coastal Plain Intrastate Air Quality Control Region.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Southern Coastal Plain Intrastate Air Quality Control...Control Regions § 81.152 Southern Coastal Plain Intrastate Air Quality Control Region. The Southern Coastal Plain Intrastate Air Quality...

2010-07-01

348

Constraints on the origin of fractured terrane, Northern Martian plains  

NASA Technical Reports Server (NTRS)

The terrane characterized by giant fracture systems that commonly define crudely polygonal patterns has received much attention because of its potential importance to such diverse problems as the amount and distribution of interstitial volatiles on Mars, the source of the northern plains, and the tectonic evolution of the northern plains. Problems and constraints on proposed models are examined.

Mcgill, George E.

1987-01-01

349

Plains Indians of North America. Grade Level: Fourth.  

ERIC Educational Resources Information Center

This is a fourth-grade teaching unit on the Plains Indians of North America. It is composed of a content outline, statement of unit goals, unit behavioral objectives, initiating activities, developmental activities, closing activities, unit evaluation plan, and a bibliography. The content outline shows that the unit covers the Plains Indian's…

Parker, Beth

350

O Wakaga. Activities for Learning about the Plains Indians.  

ERIC Educational Resources Information Center

A companion to The Mamook Book (ED 214 720), the student activity book teaches about Plains Indian cultures (in particular about Lakota life) through a series of activities such as: coloring panoramas of a Plains tipi encampment and a contemporary reservation; depicting historical and contemporary children; making a mobile; constructing a tipi and…

Brewer, Linda Skinner

351

Stratigraphy of Glen Rose Formation, Gulf coastal plain  

Microsoft Academic Search

Strata of the Glen Rose Formation and equivalent units crop out in a continuous band across the Edwards Plateau, the area of outcrop skirting the Llano uplift, the Lampasas cut plain, north-central Texas, southeastern Oklahoma, and southwestern Arkansas. These rocks dip into the subsurface of the Gulf coastal plain. Although the Glen Rose interval has been studied on outcrop and

Pittman

1989-01-01

352

Boise geothermal system, western Snake River plain, Idaho  

Microsoft Academic Search

The Boise geothermal system lies in an area of high heat flow along the northern margin of the western Snake River plain. Exploratory drilling for petroleum and geothermal water, seismic reflection profiling, and regional gravity data permit construction of a detailed structure section across the western plain. A faulted acoustic basement of volcanic rocks lies at depths of 2400 to

S. H. Wood; W. L. Burnham

1984-01-01

353

Texas High Plains Vegetable & Weed Control Research Program  

E-print Network

Texas High Plains Vegetable & Weed Control Research Program Research Summary Reports 2006 Texas Experiment Station Russell W. Wallace Extension Vegetable & Weed Specialist Alisa K. Petty Research ................................................... 7 RESULTS OF HIGH PLAINS TRIALS 8 Herbicides and Weed Control Evaluation of Firestorm Applied

Mukhtar, Saqib

354

FLOOD-PLAIN DELINEATION IN ICE JAM PRONE REGIONS  

E-print Network

Flood Insurance Program. However, unique causes of flooding, such as ice jams, have riot receivedFLOOD-PLAIN DELINEATION IN ICE JAM PRONE REGIONS By Richard M. Vogel,1 S. M. ASCE and Jery R. Stedinger,2 A. M. ASCE ABSTRACT:Flood-plain delineation in ice jam prone regions is in its infancy .A

Vogel, Richard M.

355

Assessment of sediment yield in a sloping Mediterranean watershed in Cyprus  

NASA Astrophysics Data System (ADS)

In the Mediterranean region, water catchment sediment yield as a result of erosion is higher than in many other regions in Europe due to the climatic conditions, topography, lithology and land-use. Modelling sediment transport is difficult due to intermittent stream flow and highly irregular rainfall conditions in this region. The objective of this study is to quantify sediment yield of a highly sloping Mediterranean environment. This study is conducted in the Peristerona Watershed in Cyprus, which has ephemeral water flow. In the downstream area a series of check dams have been placed across the stream to slow the flow and increase groundwater recharge. The surface area of the watershed, upstream of the check dams, is 103 km2 with elevation changing between 1540 m and 280 m and a mean local slope higher than 40% for the mountainous part and lower than 8% for the plain. The long-term average annual precipitation ranges from 755 mm in the upstream area to 276 mm in the plain. The surface extent of the sediment that was deposited at the most upstream check dam during two seasons was measured with a Differential Global Positioning System. The depth of the sediment was measured with utility poles and bulk density samples from the sediment profile were collected. The sediment had a surface area of 12600 m2 and an average depth of 0.23 m. The mean of the sediment dry bulk density samples was 1.05 t m-3 with a standard deviation of 0.11. Based on these values, area specific sediment yield was computed as 1 t ha-1 per year for the entire catchment area upstream of the check dam, assuming a check dam sediment trap efficiency of 15%. Erosion in the watershed is currently modeled with PESERA using detailed watershed data.

Djuma, Hakan; Bruggeman, Adriana; Camera, Corrado

2014-05-01

356

Iron oxide coatings on sand grains from the Atlantic coastal plain: High-resolution transmission electron microscopy characterization  

NASA Astrophysics Data System (ADS)

Nanoscale characterization of so-called iron oxide coatings on aquifer sands is vital for understanding the fate and transport of naturally occurring and anthropogenic chemical species. These coatings, which typically have a strong reddish color, are commonly assumed to consist primarily of iron oxides and oxyhydroxides. This work shows that the yellowish red to strong brown coatings on sediments from an Atlantic coastal plain aquifer in Virginia are predominantly a mixture of Si- and Al-rich nanophases of variable crystallinity with interspersed smectite and agglomerates of goethite nanoparticles. Clusters of bacterial cells, diatom fossils, sponge spicules, and other trace minerals are also observed.

Penn, R. L.; Zhu, C.; Xu, H.; Veblen, D. R.

2001-09-01

357

Sedimentology, weathering, age and geomorphological significance of Tertiary sediments on the far south coast of New South Wales  

Microsoft Academic Search

The age of the NSW coastal lowland from Tuross to the Victorian border can now be shown to be at least mid?Tertiary. By this time the coastal plain had twice been partially blanketed by terrestrial sediments. Palaeomagnetic determinations on the more recent of these sedimentary accumulations, the Long Beach Formation, reveal a minimum depositional age of Early Miocene. Eustatic influences

J. F. Nott; R. W. Young; M. Idnurm

1991-01-01

358

Constraints from Os-isotope variations on the origin of Lena Trough abyssal peridotites and implications for the composition and evolution of the depleted upper mantle  

NASA Astrophysics Data System (ADS)

The Lena Trough is a highly oblique, sparsely magmatic, ultra-slow spreading center located at the smallest distance between North America and Eurasia in the Arctic basin. Competing models suggest that it is either floored by oceanic mantle abyssal peridotites (APs) exposed by lithospheric necking, or by subcontinental mantle exposed in a still juvenile rift. To distinguish between these hypotheses, we have examined mineral major and trace element and whole rock Os-isotope variations in Lena Trough peridotites. Lena Trough peridotites are predominantly LREE-depleted, similar to other AP suites, and have 187Os/188Os ranging from ?0.118 to 0.130 (Ave.=0.1244). This distribution is nearly identical to that of abyssal peridotites globally. Both the REE patterns and the Os-isotope distribution of the Lena Trough peridotites differ starkly from subcontinental mantle xenoliths sampled at Svalbard adjacent to Lena Trough. This suggests that Lena Trough is a site of oceanic spreading, although mid-ocean ridge volcanism as such has not yet begun. Highly refractory APs from several settings have Os- and Hf-isotope compositions indicating ancient (>1 Ga) melt depletion. Some researchers have proposed that at least some APs do not directly sample the convecting upper mantle source of MORB, but instead sample highly melt-depleted residues either entrained in the convecting mantle or present as a buoyant “slag” floating atop the less-depleted MORB-source mantle. However, ocean island peridotite xenoliths and APs reveal an essentially identical, non-Gaussian distribution of Os-isotopes and also span a similar range in Hf-isotopes. The similar mean and distribution of Os-isotopes between APs and ocean island xenoliths indicate that these two sample types derive from the same heterogeneous mantle reservoir. This similarity is inconsistent with the AP “slag hypothesis” due to the significantly greater depth of origin of ocean island xenoliths with respect to APs. Global correlation between peridotite fertility indices (e.g., whole rock Al2O3, spinel Cr#) and 187Os/188Os in both APs and ocean island xenoliths suggests ancient melting events have played a role in their petrogenesis, with an average age of melt depletion of ?1.5 Ga. However, APs display a much steeper correlation than ocean island xenoliths, but have a similar y-intercept. The contrasting trends can be explained by recent on-ridge melt extraction superimposed on an ancient melt-depletion trend. The average Os-isotope composition of both APs and ocean island xenoliths is distinctly sub-chondritic, and requires significantly greater average melt depletion of the upper mantle (>10%) than suggested by previous inversions of MORB compositions.

Lassiter, J. C.; Byerly, B. L.; Snow, J. E.; Hellebrand, E.

2014-10-01

359

Precipitation Event Size Controls on Long-Term Abundance of Opuntia Polyacantha (Plains Prickly-Pear) in Great Plains Grasslands  

Microsoft Academic Search

Opuntia polyacantha Haw. (plains prickly-pear) is a common cactus in the Great Plains of North America. We used two data sets, from Montana and Colorado, to test the hypothesis that there is a range of precipitation event sizes upon which O. polyacantha specializes. Events smaller than this range (>2 to ?6 mm) do not moisten sufficient soil to be utilized,

William K. Lauenroth; R. L. Dougherty; J. S. Singh

2009-01-01

360

Akkruva Small Shield Plains: Definition of a Significant Regional Plains Unit on Venus  

NASA Astrophysics Data System (ADS)

Continued analysis of the Magellan radar image data for Venus has begun to address fundamental questions regarding the geologic evolution of the surface of the planet (with implications for processes operating within the interior of the planet). The tools of this analysis are geologic mapping and the definition of local and regional stratigraphic relationships between defined geologic units. Of particular interest are units related to the formation and/or resurfacing of the plains terrain, which covers 80% of the surface of Venus. Two quad~ngles in the Niobe Planitia region, V12 (Vellamo Planitia), centered at 37 degrees N and 135 degrees, and Vll (Shimti Tessera), centered at 37 degrees N and 105 degrees, have been mapped as part of the VDAP and Venus Geological Mapping effort. Preliminary mapping results have been reported previously; this abstract expands the description and discussion of a new plains unit defined on the basis of mapping in this region.

Aubele, J. C.

1996-03-01

361

Viking 2 Image of Mars Utopian Plain  

NASA Technical Reports Server (NTRS)

The boulder-strewn field of red rocks reaches to the horizon nearly two miles from Viking 2 on Mars' Utopian Plain. Scientists believe the colors of the Martian surface and sky in this photo represent their true colors. Fine particles of red dust have settled on spacecraft surfaces. The salmon color of the sky is caused by dust particles suspended in the atmosphere. Color calibration charts for the cameras are mounted at three locations on the spacecraft. Note the blue star field and red stripes of the flag. The circular structure at top is the high-gain antenna, pointed toward Earth. Viking 2 landed September 3,1976, some 4600 miles from its twin, Viking 1, which touched down on July 20.

1976-01-01

362

Viking 2 Image of Mars Utopian Plain  

NASA Technical Reports Server (NTRS)

The boulder-strewn field of red rocks reaches to the horizon nearly two miles from Viking 2 on Mars' Utopian Plain. Scientists believe the colors of the Martian surface and sky in this photo represent their true colors. Fine particles of red dust have settled on spacecraft surfaces. The salmon color of the sky is caused by dust particles suspended in the atmosphere. Color calibration charts for the cameras are mounted at three locations on the spacecraft. Note the blue starfield and red stripes of the flag. The circular structure at top is the high-gain antenna, pointed toward Earth. Viking 2 landed September 3, 1976, some 4600 miles from its twin, Viking 1, which touched down on July 20.

1976-01-01

363

First Look at Martian Arctic Plains  

NASA Technical Reports Server (NTRS)

This image, one of the first captured by NASA's Phoenix Mars Lander, shows the vast plains of the northern polar region of Mars. The flat landscape is strewn with tiny pebbles and shows polygonal cracking, a pattern seen widely in Martian high latitudes and also observed in permafrost terrains on Earth. The polygonal cracking is believed to have resulted from seasonal contraction and expansion of surface ice.

Phoenix touched down on the Red Planet at 4:53 p.m. Pacific Time (7:53 Eastern Time), May 25, 2008, in an arctic region called Vastitas Borealis, at 68 degrees north latitude, 234 degrees east longitude.

This image was taken shortly after landing by the spacecraft's Surface Stereo Imager.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

2008-01-01

364

Re-Wilding the Great Plains  

NSDL National Science Digital Library

A new paper published in the journal Nature has proposed re-wilding North America by introducing populations of large animals from Africa related to ones that roamed the Great Plains during the Pleistocene era. This radio broadcast features discussion with one of the architects of this idea about the ecology of America 13,000 years ago; how large mammals interacted with the environment in ways important to biodiversity; how they are thought to have been driven to extinction by humans; and whether re-introduced large animals would fill their ancient niches or become invasive species. There is also discussion about the feasibility of using biotechnology to produce Woolly Mammoths from bone-extracted DNA. The broadcast is 21 minutes in length.

365

Late Holocene paleoecology of the Southern Plains  

NASA Astrophysics Data System (ADS)

Analyses of pollen and land snails from rocksheter sites in the Osage Hills of northeastern Oklahoma indicate that the period 2000-1000 yr B.P. was moister than today. During that time, colonies of the prairie vole Microtus ochrogaster were present in the Texas Panhandle. About 1000 yr B.P. the climate changed to dry conditions that have persisted to the present. Disjunct colonies of small mammals in Texas became extinct at the beginning of the dry episode, thereby establishing the composition of the modern fauna. The climatic model for the origin of the Panhandle Aspect (A.D. 1200-1500) is questioned on the grounds that the Southern Plains experienced a long period of dry climate commencing A.D. 950.

Hall, Stephen A.

1982-05-01

366

Seafloor structure and uppermost sedimentation in the Pigafetta Basin, Magellan Seamount Chain, and East Mariana Basin of the Central-Western Pacific  

NASA Astrophysics Data System (ADS)

We conducted a marine geophysical survey of the Central-Western Pacific seafloor in 2011 aboard the R/V Thomas G. Thompson (TN272). Our survey imaged some of the oldest seafloor on the planet in a region of sparse data coverage. We present new (3.5 kHz) and bathymetry data from the Mesozoic Hawaiian magnetic lineations (Jurassic Quiet Zone) and a transect from the south end of the Pigafetta Basin (PB), west across the Magellan Seamount Chain (MSC) and the East Mariana Basin (EMB) to the Mariana Trench. The Chirp system penetrates the overlying sediment cover to a depth of ~50 meters below seafloor (mbsf). The deepest part of the Chirp record is marked by a strongly reflecting horizon, which occasionally crops out at the seafloor near volcanic peaks or bathymetric highs. Correlation of these data to DSDP/ODP drill sites (801C, 802, 199, 585) enables us to compare seafloor structure and uppermost sedimentation in the Jurassic Quiet Zone (JQZ), Pigafetta Basin, Magellan Seamounts, and the East Mariana Basin. Within the JQZ, and at the southern end of the PB, a 30- to 50-m-thick, acoustically-transparent sediment layer uniformly overlies the strongly reflecting horizon observed at water depths ranging from 4400m-5900m. We interpret this unit to be composed of pelagic abyssal clay and radiolarian oozes ubiquitous in the central-western Pacific. The basal horizon in this region is most likely formed by a layer of chert-porcelanite. In the southeastern PB (161.3 E, 17 N), this horizon reaches the seafloor at a depth of 5650 m and the transparent sediment package is truncated. In the region of the MSC, ~115 km north of drill sites 199 and 585, Chirp data show numerous volcanic peaks and a 50-m-thick sequence of stratified reflections. Volcaniclastics likely contribute to the layering. We first observe the stratified sediment package near 156.7 E, 15 N after a gap in data coverage. The sediment layer thins to the west and onlaps the basal horizon near the base of a seamount. Based on its depth, we interpret the basal horizon in this region of the survey to be formed by interlayered nannochalk, limestone, tuff, and chert. In the EMB, the Chirp data image several small, sediment-filled basins bounded by bathymetric highs formed by both faulting and volcanism. There are also volcanic intrusions visible. Along a broad, sloping bathymetric high centered on 151.9 E, 14.5 N, a ~15-m-thick transparent sediment layer of abyssal clay is observed above a ~35-m-thick stratified section, possibly volcaniclastic turbidites. Based on data from site 802 (~350 km to the south) we interpret the basal horizon in this region to be formed by Miocene tuff. At the western edge of the EMB, <250 km from the base of the Mariana Trench, we observe several normal faults with offsets from 5-45 m. In both the PB and EMB, pelagic clay composes the youngest sediment layers, whereas in the MSC, there is evidence of more recent volcanic activity. Overall, abyssal clay thickness decreases toward the trench, as crustal age decreases. The shipboard Chirp data provides valuable information about seafloor deformation and shallow sedimentation in a region of sparse data.

Mathews, N. J.; Oakley, A. J.; Lizarralde, D.; Tominaga, M.; Tivey, M.; Sager, W. W.

2013-12-01

367

Nomenclature of regional hydrogeologic units of the Southeastern Coastal Plain aquifer system  

USGS Publications Warehouse

Clastic sediments of the Southeastern Coastal Plain aquifer system can be divided into four regional aquifers separated by three regional confining units. The four regional aquifers have been named for major rivers that cut across their outcrop areas and expose the aquifer materials. From youngest to oldest, the aquifers are called the Chickasawhay River, Pearl River, Chattahoochee River, and Black Warrior River aquifers, and the regional confining units separating them are given the same name as the aquifer they overlie. Most of the regional hydrogeologic units are subdivided within each of the four States that comprise the study area. Correlation of regional units is good with hydrogeologic units delineated by a similar regional study to the west and southwest. Because of complexity created by a major geologic structure to the northeast of the study area and dramatic facies change from clastic to carbonate strata to the southeast, correlation of regional hydrogeologic units is poor in these directions. (Author 's abstract)

Miller, J. A.; Renken, R. A.

1988-01-01

368

Salt-dome locations in the Gulf Coastal Plain, South-Central United States  

USGS Publications Warehouse

Information on salt domes in Gulf of Mexico Coastal Plain, south-central United States and the adjacent Continental Shelf were compiled from major published sources, 1973-84. The location of 624 salt domes is shown on a map at a scale of 1:1 ,500,000. A color-coding system was used to show that the occurrence, size, shape, and location of these domes varies among sources. Two tables of additional data accompany the map and include other available information such as: identifying sources, depth to salt and caprock, diameter, volume, name, and uppermost zone of surrounding sediment that is penetrated, as well as the number of matches between sources. The locations of salt domes that penetrate specific zones within the gulf coast regional aquifer system are shown on maps. (USGS)

Beckman, J.D.; Williamson, A.K.

1990-01-01

369

Carbon cycle and the rate of vertical accumulation of peat in the Mississippi River deltaic plain  

SciTech Connect

A large percentage of the annual plant biomass production in interdistributary basins of the Mississippi River delta plain either remains on the marsh in the form of organic-rich sediment (peat) or is lost to the atmosphere as carbon dioxide and methane. Peat is formed due to vertical accretion as the marsh surface is maintained relative to a mean water level. The rate of accretion determined from Cs-137 dating averaged 0.85 cm and 0.95 cm/yr for the fresh and brackish peat deposits respectively. However, increase in water level, obtained from analysis of tide gauge data, was estimated to be in order of 60-1.0 cm/yr. The rapid rate of peat accumulation (254-296 g C/sq m/yr) is attributed to increases in water level due to subsidence resulting from the consolidation of Mississippi River deltaic deposits. 28 references, 5 figures, 1 table.

Delaune, R.D.; Smith, C.J.

1984-10-01

370

Sedimentation History of Lago Guayabal, Puerto Rico, 1913-2001  

USGS Publications Warehouse

The Lago Guayabal dam, located in the municipality of Villalba in southern Puerto Rico, was constructed in 1913 for irrigation of croplands in the southern coastal plains and is owned and operated by the Puerto Rico Electric Power Authority. The reservoir had an original storage capacity of 11.82 million cubic meters and a drainage area upstream of the dam of 112 square kilometers. Sedimentation has reduced the storage capacity to 6.12 million cubic meters in 2001, which represents a storage loss of about 48 percent. However, the actual sediment accumulation in the reservoir during the 88 years is greater, because some sediment removal was conducted between 1940 and 1948 by dredging and sluicing. This report summarizes the historical data from a 1913 land survey and eight bathymetric surveys conducted between 1914 and 2001, and the relation of high sedimentation to agricultural land practices within the Lago Guayabal basin and six major hurricanes which made landfall on the island. The reservoir had an area-normalized sedimentation rate of about 1,863 cubic meters per square kilometer per year between 1913 and 1936 from a 112 square kilometer basin. In 1972, a new dam upstream along the Rio Toa Vaca impounded runoff from 57.5 square kilometers, and sediment transport to Lago Guayabal was reduced. A comparison of bathymetric survey results between 1972 and 2001 indicates an area-normalized sedimentation rate of 1,120 cubic meters per square kilometer per year or about 60 percent of the rate between 1913 and 1936. The significant reduction (almost half) of the sedimentation rate after the Toa Vaca dam was built may indicate that erosion susceptibility of the Rio Toa Vaca watershed is about twice that of the Rio Jacaguas watershed impounded by Lago Guayabal.

Soler-López, Luis R.

2003-01-01

371

Controls on phosphorous mobility in the Potomac River near the Blue Plains wastewater treatment plant  

USGS Publications Warehouse

The Blue Plains wastewater treatment plant is the largest point source of phosphorus in the Potomac River basin, discharging an average of 2 metric tons of phosphorus into the river each day in 1980. An intensive study of the water and sediments in the vicinity of the treatment plant was conducted in 1979-80 in order to characterize the major factors controlling the mobility of effluent-derived phosphorus in the area. The transport of phosphorus near the treatment plant was found to be affected by the circulation regime, by inorganic adsorption reactions with sediments, and by metabolic uptake and release by phytoplankton. The effect of river discharge on the convective transport of phosphorus near the outfall is significantly reduced by a mid-river shoal area, which confines the flow path of the effluent to an embayment on the eastern side of the river for a distance of 4 kilometers below the outfall. This embayment appears to serve as a sediment trap, where protection from bottom scour during high-flow events has permitted fine-grained sediments to accumulate. Measurements of mean residence time indicate that the effluent leaves the embayment area 21? days after being discharged from the outfall. Measurements of the linear decay constant for the removal of dissolved phosphorus from the water column reveal a diurnal cycle corresponding to the metabolic utilization of phosphorus by phytoplankton. This cyclic removal is superimposed on a constant and noncyclic adsorption of phosphorus by inorganic phases. Forty-eight hour average values of the linear decay constant for dissolved phosphorus in the area range from 0.4 to 1.1 per day. Analyses of bottom sediments indicate that approximately 13 percent of the phosphorus discharged between September 1977 and August 1980 has been retained in the embayment. The primary inorganic phase responsible for phosphorus adsorption is amorphous iron (ferric oxy-hydroxides); amorphous aluminum and clay minerals appear to play secondary roles. The accumulation of sorbed phosphorus in the embayment has been promoted by the deposition of fine-grained sediments enriched in ferric oxy-hydroxides. Conversely, the absence of ferric oxy-hydroxides in coarse-grained sediments near the outfall has facilitated the precipitation of the ferrous phosphate mineral vivianite.

Hearn, Paul P.

1985-01-01

372

Remineralization Uptake Sediment Release  

E-print Network

Mortality Egestion Egestion Grazing Mortality Decomp. Silicate Large Phytoplankton Small Phytoplankton Large Sediment Release Photosynthesis Mortality Grazing Grazing Grazing Mortality Mortality Egestion Egestion

NOAA Great Lakes Environmental Research Laboratory, Episodic Events

373

Fluvial sediment in Ohio  

USGS Publications Warehouse

Characteristics of fluvial sediment in Ohio streams and estimates of sediment yield are reported. Results are based on data from several daily record stations and 5 years of intermittent record from a 38-station network. Most of the sediment transported by Ohio streams is in suspension. Mean annual bedload discharge, in percentage of mean annual suspended-sediment discharge, is estimated to be less than 10 percent at all but one of the sediment stations analyzed. Duration analysis shows that about 90 percent of the suspended sediment is discharged during 10 percent of the time. Concentration of suspended sediment averages less than 100 milligrams per liter 75 percent of the time and less than 50 milligrams per liter 50 percent of the time. Suspended sediment in Ohio streams is composed mostly of silt and clay. Sand particle content ranges from 1 to 2 percent in northwestern Ohio to 15 percent in the east and southeast. Sediment yields range from less than 100 tons per square mile per year (35 tonnes per square kilometer per year) in the northwest corner of Ohio to over 500 tons per square mile per year (17,5 tonnes per square kilometer per year) in the southern part, in Todd Fork basin, lower Paint Creek basin, and the Kentucky Bluegrass area. Yield from about 63 percent of Ohio's land area ranges from 100 to 200 tons per square mile per year (35 to 70 tonnes per square kilometer per year).

Anttila, Peter W.; Tobin, Robert L.

1978-01-01

374

Uncertainty Analysis of Reservoir Sedimentation  

Microsoft Academic Search

Significant advances have been made in understanding the importance of the factors involved in reservoir sedimentation. However, predicting the accumulation of sediment in a reservoir is still a complex problem. In estimating reservoir sedimentation and accumulation, a number of uncertainties arise. These are related to quantity of streamflow, sediment load, sediment particle size, and specific weight, trap efficiency, and reservoir

Jose D. Salas; Hyun-Suk Shin

1999-01-01

375

Reservoir Sedimentation Management in Asia  

Microsoft Academic Search

In order to reduce and remove reservoir sedimentation for sustainable use, different sediment control measures have been developed and used in Asia. This paper is to review the reservoir sedimentation status in the Asian nations and also to describe the sedimentation management experience in China, India and Japan. The sedimentation control measures at the Dujiangyan, Three Gorge Project and Tianjiawan

Jian Liu; Bingyi Liu; Kazuo Ashida

376

Correlation of Miocene sequences and hydrogeologic units, New Jersey Coastal Plain  

USGS Publications Warehouse

We have developed a Miocene sequence stratigraphic framework using data from recently drilled boreholes in the New Jersey Coastal Plain. Sequences are shallowing upward, unconformity-bounded units; fine-grained shelf and prodelta sediments grade upward to delta front and shallow-marine sands, corresponding to confining bed-aquifer couplets. By dating Miocene sequences using Sr-isotope stratigraphy, and mapping with borehole data and geophysical logs, we can predict the continuity and effectiveness of the confining beds and aquifers. The following are illustrated on a 90-km basinward dip section: (1) the composite confining bed is comprised of the KwO and lower Kw1a (ca. 23.8-20.5 Ma) sequences downdip at Atlantic City, and the Kw1b, Kw1a and older sequences updip (ca. 69.3-20.6 Ma), and is continuous throughout most of the coastal plain; (2) the major confined aquifer, the Atlantic City 800-foot sand, is comprised of the upper Kw1a and Kw1b sequences (ca. 20.5-20.2 Ma) and is an areally continuous sand that is interconnected with the Kirkwood-Cohansey aquifer system updip of Mays Landing; (3) the confining bed above the Atlantic City 800-foot sand is comprised of the Kw2a, Kw2b, and Kw3 sequences (18.1-13.3 Ma) and is an extensive confining bed that pinches out updip. These sequences and aquifer-confining bed couplets are linked to global sea-level changes evinced by the ??18O record. We conclude that sequence stratigraphy is a powerful tool when applied to regional hydrogeologic problems, although basinal tectonic differences and localized variations in sediment supply can affect aquifer thickness and permeability.

Sugarman, P. J.; Miller, K. G.

1997-01-01

377

Linking the historic 2011 Mississippi River flood to coastal wetland sedimentation  

USGS Publications Warehouse

Wetlands in the Mississippi River deltaic plain are deteriorating in part because levees and control structures starve them of sediment. In Spring of 2011 a record-breaking flood brought discharge on the lower Mississippi River to dangerous levels, forcing managers to divert up to 3500 m3/s-1 of water to the Atchafalaya River Basin. Here we quantify differences between the Mississippi and Atchafalaya River inundation and sediment-plume patterns using field-calibrated satellite data, and assess the impact these outflows had on wetland sedimentation. We characterize hydrodynamics and suspended sediment patterns of the Mississippi River plume using in-situ data collected during the historic flood. We show that the focused, high-momentum jet from the leveed Mississippi delivered sediment far offshore. In contrast, the plume from the Atchafalaya was more diffuse; diverted water inundated a large area; and sediment was trapped within the coastal current. Maximum sedimentation (up to several centimetres) occurred in the Atchafalaya Basin despite the larger sediment load carried by the Mississippi. Minimum accumulation occurred along the shoreline between these river sources. Our findings provide a mechanistic link between river-mouth dynamics and wetland sedimentation patterns that is relevant for plans to restore deltaic wetlands using artificial diversions.

Falcini, Federico; Khan, Nicole S.; Macelloni, Leonardo; Horton, Benjamin P.; Lutken, Carol B.; McKee, Karen L.; Santoleri, Rosalia; Colella, Simone; Li, Chunyan; Volpe, Gianluca; D’Emidio, Marco; Salusti, Alessandro; Jerolmack, Douglas J.

2012-01-01

378

Subsurface Deformation in the Gangetic Plain - First results from the BrahmaSeis multichannel seismic survey on Bangladesh Rivers  

NASA Astrophysics Data System (ADS)

In Bangladesh, the northeastern boundary of the Indian-Asian collision zone is buried under thick delta sediments, delivered in huge volumes by the Ganges-Brahmaputra-Meghna river system. Monsoon-induced erosion provided several tens of meters of Holocene sediments to a subsiding delta plain, and it therefore remains a challenge to reconstruct the plate boundary, fault planes and main deformational styles and phases. While structural investigations with seismic methods on land are particularly difficult in the country, the distinctly elevated water level after the peak monsoon season provided the opportunity of a water seismic survey, utilizing marine seismic equipment and approaches. As part of the BanglaPIRE project, a first multichannel seismic survey had been carried out in September 2011 particularly on the rivers Meghna and Jamuna to find and map indications for subsurface deformation and the associated response of the sediment dispersal system during the late Quaternary development of the Gangetic delta plain. Using a high-resolution 48-channel streamer and a micro GI-Gun with 0.1 L volume, supported by two small diving compressors, continuous airgun profiles were acquired in several daily stretches along both rivers northward to the Indian border. Major challenges were, among others, a lack of navigational fixpoints in a rapidly changing delta and river landscape, the lack of clearly defined strata in a predominantly sandy environment, and the widespread occurrence of large amounts of shallow gas. In the northernmost stretch of the survey, the Dauki Fault, bounding the Shillong Plateau uplift on the southern side, is supposed to be covered by sediment in the slowly subsiding Sylhet Basin. On the Meghna river in central Bangladesh, the westernmost extent of the Indo-Burman Fold Belt was assumed. And on Jamuna, the western extension of the Dauki Fault and its interaction with the main river system is as unclear. The acquired multichannel seismic data, using shot rates on the order of 5 to 8 seconds, were sufficiently dense to achieve a horizontal resolution between 1 and 5 meters, and vertical resolution is on the order of 1 meter. Preliminary processing has revealed several areas, where pronounced deformation can be derived from underlying pre-Holocene strata geometries, revealing anticlines and reflector truncation at the base of the river plain sediments. In particular the Jamuna N-S transect completely images this Holocene base reflector. In the northernmost survey lines on Jamuna, it seems that the assumed position of the Dauki Fault finds it expression in subsurface deformation, an anticline geometry as well as steps in the Holocene base reflector.

Spiess, V.; Schwenk, T.; Palamenghi, L.; Goodbred, S. L.; Steckler, M. S.; Seeber, L.; Petter, A. L.; Akhter, S. H.; Mondal, D.; Khan, S. R.

2012-12-01

379

New chronostratigraphic model for Mississippi River Chenier plain  

SciTech Connect

The chenier plain of the Mississippi River is a shore-parallel zone of alternating transgressive clastic ridges separated by progradational mud flats. The term chenier is derived from the French/Cajun word chene for live oak, the tree species that colonizes the crests of the higher ridges. The Mississippi River chenier plain stretches 200 km from Sabine Pass, Texas, to Southwest Point, Louisiana, and ranges between 20 and 30 km wide, with elevations of 2-6 m. The chenier plain evolved during the Holocene as a sequence of prograding mud flats intermittently reworked into ridges.

Penland, S.; Suter, J.

1989-03-01

380

Timing and formation of Mississippi River chenier plain  

SciTech Connect

The chenier plain of the Mississippi River is a shore-parallel zone of alternating transgressive clastic ridges separated by progradational mud flats. The term chenier is derived from the cajun term chene for live oak, the tree species that colonized the crests of the higher ridges. The Mississippi River chenier plain stretches 200 km from Sabine Pass, Texas, to Southwest Point, Louisiana, and ranges between 20 and 30 km wide, with elevations of 2-6 m. The chenier plain evolved during the Holocene as a sequence of prograding mudflats intermittently reworked into ridges.

Penland, S. (Louisiana Geological Survey, Baton Rouge (USA)); Suter, J.R. (Exxon Production Research, Houston, TX (USA))

1989-09-01

381

An estimation of sediment thickness using Sp converted phases in Kaoping, Taiwan  

NASA Astrophysics Data System (ADS)

The Kaoping area is a triangle alluvial plain, located in the southwestern Taiwan. Accelerograms recorded from 1991 to 2010 by the Taiwan Strong Motion Instrumentation Program (TSMIP) stations are used to study the thickness variations of the Quaternary alluviums beneath Kaoping area by examining the Sp converted phase. Travel-time difference of S and Sp phases is used to estimate the sediment thickness. With highly seismicity activities and dense strong motion array, this technique has been used in Lan-Yang Plain and Chia-Nan Plain. In this study we focus on Kaoping region in order to discuss the underground structures in the study region. The major targets are to determine the location of Chaochou fault and Sp phase is converted from which formation boundary. Results show that the thickness become thicker toward the west in Kaohsiung area, and the thickness become thinner toward east. Details will be presented in this study.

Chuang, M.; Wu, Y.; Wei, J.; Chang, C.

2011-12-01

382

Indications for algae-degrading benthic microbial communities in deep-sea sediments along the Antarctic Polar Front  

NASA Astrophysics Data System (ADS)

Phytoplankton blooms in surface waters of the oceans are known to influence the food web and impact microbial as well as zooplankton communities. Numerous studies have investigated the fate of phytoplankton-derived organic matter in surface waters and shelf sediments, however, little is known about the effect of sinking algal biomass on microbial communities in deep-sea sediments. Here, we analyzed sediments of four regions in the Southern Atlantic Ocean along the Antarctic Polar Front that had different exposures to phytoplankton bloom derived organic matter. We investigated the microbial communities in these sediments using high-throughput sequencing of 16S rRNA molecules to determine microorganisms that were active and catalyzed reporter deposition fluorescence in situ hybridization to infer their abundance and distribution. The sediments along the Antarctic Polar Front harbored microbial communities that were highly diverse and contained microbial clades that seem to preferably occur in regions of high primary productivity. We showed that organisms affiliated with the gammaproteobacterial clade NOR5/OM60, which is known from surface waters and coastal sediments, thrive in the deep-sea. Benthic deep-sea NOR5 were abundant, diverse, distinct from pelagic NOR5 and likely specialized on the degradation of phytoplankton-derived organic matter, occupying a similar niche as their pelagic relatives. Algal detritus seemed to not only fuel the benthic microbial communities of large areas in the deep-sea, but also to influence communities locally, as we found a peak in Flavobacteriaceae-related clades that also include degraders of algal biomass. The results strongly suggest that phytoplankton-derived organic matter was rapidly exported to the deep-sea, nourished distinct benthic microbial communities and seemed to be the main energy source for microbial life in the seafloor of vast abyssal regions along the Antarctic Polar Front.

Emil Ruff, S.; Probandt, David; Zinkann, Ann-Christine; Iversen, Morten H.; Klaas, Christine; Würzberg, Laura; Krombholz, Nicole; Wolf-Gladrow, Dieter; Amann, Rudolf; Knittel, Katrin

2014-10-01

383

Viral Density and Virus-to-Bacterium Ratio in Deep-Sea Sediments of the Eastern Mediterranean  

PubMed Central

Viruses are now recognized as a key component in pelagic systems, but their role in marine sediment has yet to be assessed. In this study bacterial and viral densities were determined at nine deep-sea stations selected from three main sites (i.e., the Sporades Basin, the Cretan Sea, and the Ierapetra Trench at depths of 1,232, 1,840, and 4,235 m, respectively) of the Eastern Mediterranean. The three areas were characterized by different phytopigment and biopolymeric carbon concentrations and by changes in the protein and carbohydrate pools. A gradient of increasing trophic conditions was observed from the Sporades Basin (North Aegean) to the Ierapetra Trench (South Aegean). Viral densities (ranging from 1 × 109 to 2 × 109 viruses ml of sediment?1) were significantly correlated to bacterial densities (n = 9, r2 = 0.647) and reached values up to 3 orders of magnitude higher than those generally reported for the water column. However, the virus-to-bacterium density ratio in deep-sea sediments was about 1 order of magnitude lower (range of 2 to 5, with a modal value of 2.6) than in pelagic environments. Virus density decreased vertically with depth in sediment cores at all stations and was below detection limits at the 10-cm depth of the abyssal sediments of the Ierapetra Trench. Virus density in the sediment apparently reflected a gradient of particle fluxes and trophic conditions, displaying the highest values in the Sporades Basin. The low virus-to-bacterium ratios and their inverse relationship with station depth suggest that the role played by viruses in controlling deep-sea benthic bacterial assemblages and biogeochemical cycles is less relevant than in pelagic systems. PMID:10788350

Danovaro, Roberto; Serresi, Michela

2000-01-01

384

Stream-sediment geochemistry in mining-impacted streams : sediment mobilized by floods in the Coeur d'Alene-Spokane River system, Idaho and Washington  

USGS Publications Warehouse

Environmental problems associated with the dispersion of metal-enriched sediment into the Coeur d'Alene-Spokane River system downstream from the Coeur d'Alene Mining District in northern Idaho have been a cause of litigation since 1903, 18 years after the initiation of mining for lead, zinc, and silver. Although direct dumping of waste materials into the river by active mining operations stopped in 1968, metal-enriched sediment continues to be mobilized during times of high runoff and deposited on valley flood plains and in Coeur d'Alene Lake (Horowitz and others, 1993). To gauge the geographic and temporal variations in the metal contents of flood sediment and to provide constraints on the sources and processes responsible for those variations, we collected samples of suspended sediment and overbank deposits during and after four high-flow events in 1995, 1996, and 1997 in the Coeur d'Alene-Spokane River system with estimated recurrence intervals ranging from 2 to 100 years. Suspended sediment enriched in lead, zinc, silver, antimony, arsenic, cadmium, and copper was detected over a distance of more than 130 mi (the downstream extent of sampling) downstream of the mining district. Strong correlations of all these elements in suspended sediment with each other and with iron and manganese are apparent when samples are grouped by reach (tributaries to the South Fork of the Coeur d'Alene River, the South Fork of the Coeur d'Alene River, the main stem of the Coeur d'Alene River, and the Spokane River). Elemental correlations with iron and manganese, along with observations by scanning electron microscopy, indicate that most of the trace metals are associated with Fe and Mn oxyhydroxide compounds. Changes in elemental correlations by reach suggest that the sources of metal-enriched sediment change along the length of the drainage. Metal contents of suspended sediment generally increase through the mining district along the South Fork of the Coeur d'Alene River, decrease below the confluence of the North and South Forks, and then increase again downstream of the gradient flattening below Cataldo. Metal contents of suspended sediment in the Spokane River below Coeur d'Alene Lake were comparable to those of suspended sediment in the main stem of the Coeur d'Alene River above the lake during the 1997 spring runoff, but with somewhat higher Zn contents. Daily suspended-sediment loads were about 100 times larger in the 1996 flood (50-100-year recurrence interval) than in the smaller 1997 floods (2-5-year recurrence intervals). Significant differences in metal ratios and contents are also apparent between the two flood types. The predominant source of suspended sediment in the larger 1996 flood was previously deposited, metal-enriched flood-plain sediment, identified by its Zn/Pb ratio less than 1. Suspended sediment in the smaller 1997 floods had metal ratios distinct from those of the flood-plain deposits and was primarily derived from metal-enriched sediment stored within the stream channel, identified by a Zn/Pb ratio greater than 1. Sediment deposited during overbank flooding on the immediate streambank or natural levee of the river typically consists of sandy material with metal ratios and contents similar to those of the sandy streambed sediment in the adjacent river reach. Samples of overbank deposits in backlevee marshes collected after the 1996 flood have metal ratios similar to those of peak-flow suspended sediment in the same river reach, but generally lower metal contents.

Box, Stephen E.; Bookstrom, Arthur A.; Ikramuddin, Mohammed

2005-01-01

385

Distribution and preservation of pteropod tests in sediments of the Sigsbee Plain, Gulf of Mexico  

E-print Network

subula Clio pyramidata Cavolinia gibbosa Cavolinia inflexa 2. Tropical Province Limacina trochiformis Ryalocylis striata cavolinia uncinata Clio convexa (Indo-Pacific only) Cavolinia globulosa (Indo-pacific only) 3. Harv-Water Cosmopo... subula Clio pyramidata Cavolinia gibbosa Cavolinia inflexa 2. Tropical Province Limacina trochiformis Ryalocylis striata cavolinia uncinata Clio convexa (Indo-Pacific only) Cavolinia globulosa (Indo-pacific only) 3. Harv-Water Cosmopo...

Pollard, Richard Mark

2012-06-07

386

Trends in nutrient and sediment retention in Great Plains reservoirs (USA)  

E-print Network

river water quality in relation to organic forms of nutrients, bio- chemical oxygen demand (Chung et al Reservoirs are artificial ecosystems with physical, chemical, and biological transitional charac- teristics- chemical processes. We investigated the effects of res- ervoirs on the water quantity and quality

Dodds, Walter

387

Great Plains Wind Energy Transmission Development Project  

SciTech Connect

In fiscal year 2005, the Energy & Environmental Research Center (EERC) received funding from the U.S. Department of Energy (DOE) to undertake a broad array of tasks to either directly or indirectly address the barriers that faced much