Spatial variability of shelf sediments in the STRATAFORM natural laboratory, Northern California

USGS Publications Warehouse

Goff, J.A.; Wheatcroft, R.A.; Lee, H.; Drake, D.E.; Swift, D.J.P.; Fan, S.

2002-01-01

The "Correlation Length Experiment", an intensive box coring effort on the Eel River shelf (Northern California) in the summer of 1997, endeavored to characterize the lateral variability of near-surface shelf sediments over scales of meters to kilometers. Coring focused on two sites, K60 and S60, separated by ??? 15 km along the 60 m isobath. The sites are near the sand-to-mud transition, although K60 is sandier owing to its proximity to the Eel River mouth. Nearly 140 cores were collected on dip and strike lines with core intervals from < 10m to 1 km. Measurements on each core included bulk density computed from gamma-ray attenuation, porosity converted from resistivity measurements, and surficial grain size. Grain size was also measured over the full depth range within a select subset of cores. X-radiograph images were also examined. Semi-variograms were computed for strike, dip, and down-hole directions at each site. The sand-to-mud transition exerts a strong influence on all measurements: on average, bulk density increases and porosity decreases with regional increases in mean grain size. Analysis of bulk density measurements indicates very strong contrasts in the sediment variability at K60 and S60. No coherent bedding is seen at K60; in the strike direction, horizontal variability is "white" (fully uncorrelated) from the smallest scales examined (a few meters) to the largest (8 km), with a variance equal to that seen within the cores. In contrast, coherent bedding exists at S60 related to the preservation of the 1995 flood deposit. A correlatable structure is found in the strike direction with a decorrelation distance of ??? 800 m, and can be related to long-wavelength undulations in the topography and/or thickness of the flood layer or overburden. We hypothesize that the high degree of bulk density variability at K60 is a result of more intense physical reworking of the seabed in the sandier environment. Without significant averaging, the resistivity-based porosity measurements are only marginally correlated to gamma-ray-bulk density measurements, and are largely independent of mean grain size. Furthermore, porosity displays a high degree of incoherent variability at both sites. Porosity, with a much smaller sample volume than bulk density, may therefore resolve small-scale biogenic variability which is filtered out in the bulk density measurement. ?? 2002 Elsevier Science Ltd. All rights reserved.

Cyclic formation and dissociation of methane hydrate within partially water saturated sand

NASA Astrophysics Data System (ADS)

Kneafsey, T. J.; Nakagawa, S.

2010-12-01

For partially water-saturated sediments, laboratory experiments have shown that methane hydrate forms heterogeneously within a sample at the core scale. The heterogeneous distribution of hydrate in combination with grain-scale hydrate location (eg. grain cementing, load bearing, and pore filling), determines the overall mechanical properties of hydrate-bearing sediments including shear strength and seismic properties. For this reason, understanding the heterogeneity of hydrate-bearing sample is essential when the bulk properties of the sample are examined in the laboratory. We present a series of laboratory methane hydrate formation and dissociation experiments with concurrent x-ray CT imaging and low-frequency (near 1 kHz) seismic measurements. The seismic measurements were conducted using a new acoustic resonant bar technique called the Split Hopkinson Resonant Bar method, which allows using a small sediment core (3.75 cm diameter, 7.5 cm length). The experiment was conducted using a jacketed, pre-compacted, fine-grain silica sand sample with a 40% distilled water saturation. Under isotropic confining stress of 6.9 MPa and a temperature 4 oC, the hydrate was formed in the sample by injecting pure methane gas at 5.6 MPa. Once the hydrate formed, it was dissociated by reducing the pore pressure to 2.8 MPa. This cycle was repeated by three times (dissociation test for the third cycle was not done) to examine the resulting changes in the hydrate distribution and seismic signatures. The repeated formation of hydrate resulted in significant changes in its distribution, which resulted in differences in the overall elastic properties of the sample, determined from the seismic measurements. Interestingly, the time intervals between the dissociation and subsequent formation of hydrate affected the rate of hydrate formation, shorter intervals resulting in faster formation. This memory effect, possibly caused by the presence of residual “seed crystals” in the pore water providing nucleation points for hydrate formation, did not result in rapid formation at all locations in the sample. In spite of heterogeneity, observed seismic properties were very similar for the two measurements during dissociation.

Blending foundry sands with soil: Effect on dehydrogenase activity.

PubMed

Dungan, Robert S; Kukier, Urzsula; Lee, Brad

2006-03-15

Each year U.S. foundries landfill several million tons of sand that can no longer be used to make metalcasting molds and cores. A possible use for these materials is as an ingredient in manufactured soils; however, potentially harmful metals and resin binders (used to make cores) may adversely impact the soil microbial community. In this study, the dehydrogenase activity (DHA) of soil amended with molding sand (clay-coated sand known as "green sand") or core sands at 10%, 30%, and 50% (dry wt.) was determined. The green sands were obtained from iron, aluminum, and brass foundries; the core sands were made with phenol-formaldehyde or furfuryl alcohol based resins. Overall, incremental additions of these sands resulted in a decrease in the DHA which lasted throughout the 12-week experimental period. A brass green sand, which contained high concentrations of Cu, Pb, and Zn, severely impacted the DHA. By week 12 no DHA was detected in the 30% and 50% treatments. In contrast, the DHA in soil amended with an aluminum green sand was 2.1 times higher (all blending ratios), on average, at week 4 and 1.4 times greater (30% and 50% treatments only) than the controls by week 12. In core sand-amended soil, the DHA results were similar to soils amended with aluminum and iron green sands. Increased activity in some treatments may be a result of the soil microorganisms utilizing the core resins as a carbon source. The DHA assay is a sensitive indicator of environmental stress caused by foundry sand constituents and may be useful to assess which foundry sands are suitable for beneficial use in the environment.

Inexpensive, easy-to-construct suction coring devices usable from small boats

USGS Publications Warehouse

Onuf, Christopher P.; Chapman, Duane C.; Rizzo, William M.

1996-01-01

Collection of sediment cores in depths of 1-5 m is difficult with traditional sampling gear. Here we describe three suction coring devices constructed with readily available plumbing supplies and parts easily made from acrylic plastic and silicone sealant. The samplers have been used successfully in sediments ranging from coarse sands and shell hash to muds, highly organic deposits, and dense clays. Successful applications have ranged from contaminants analysis, toxicity testing, seagrass mapping, and assessment of sediment-microfloral interactions to sampling the infauna of surf-swept beaches.

Potential for downward leakage to the Floridan Aquifer, Green Swamp area, central Florida

USGS Publications Warehouse

Grubb, H.F.

1977-01-01

A qualitative evaluation of the potential for downward leakage from the surficial sand aquifer to the underlying Floridan aquifer was made for the Green Swamp area (about 870 sq mi) in central Florida. Downward leakage, or recharge, is limited under natural conditions owing to the nearness to land surface of the potentiometric surface of both the sand aquifer and the underlying Floridan aquifer. Continuous cores of the unconsolidated section were obtained at 74 sites in the study area and were evaluated for downward leakage potential based on grain-size distribution. Sand percentage was estimated for each interval or bed from microscopic examination of the core samples. The four maps prepared from this data show sand thickness, clay thickness, relative vertical hydraulic conductivity of the confining beds and the relative potential for downward leakage. About 20 percent (178 sq mi) of the area classified has a relatively good potential for downward leakage; almost 50 percent of the area has a relatively poor potential. (Woodard-USGS)

New Experiences in Dike Construction with Soil-Ash Composites and Fine-Grained Dredged Materials

NASA Astrophysics Data System (ADS)

Duszyński, Remigiusz; Duszyńska, Angelika; Cantré, Stefan

2017-12-01

The supporting structure inside a coastal dike is often made of dredged non-uniform sand with good compaction properties. Due to the shortage of natural construction material for both coastal and river dikes and the surplus of different processed materials, new experiments were made with sand-ash mixtures and fine-grained dredged materials to replace both dike core and dike cover materials resulting in economical, environmentally friendly and sustainable dikes. Ash from EC Gdańsk and dredged sand from the Vistula river were mixed to form an engineering material used for dike construction. The optimum sand-ash composites were applied at a field test site to build a large-scale research dike. Fine-grained dredged materials from Germany were chosen to be applied in a second full-scale research dike in Rostock. All materials were investigated according to the standards for soil mechanical analysis. This includes basic soil properties, mechanical characteristics, such as grain-size distribution, compaction parameters, compressibility, shear strength, and water permeability. In the field, the infiltration of water into the dike body as well as the erosion resistance of the cover material against overflowing water was determined. Results of both laboratory and field testing are discussed in this paper. In conclusion, the mixing of bottom ash with mineral soil, such as relatively uniform dredged sand, fairly improves the geotechnical parameters of the composite, compared to the constituents. Depending on the composite, the materials may be suitable to build a dike core or an erosion-resistant dike cover.

Shipboard magnetic field "noise" reveals shallow heavy mineral sediment concentrations in Chesapeake Bay

USGS Publications Warehouse

Shah, Anjana K.; Vogt, Peter R.; Rosenbaum, Joseph G.; Newell, Wayne L.; Cronin, Thomas M.; Willard, Debra A.; Hagen, Rick A.; Brozena, John; Hofstra, Albert

2012-01-01

Shipboard magnetic field data collected over Chesapeake Bay exhibit low-amplitude, short-wavelength anomalies that most likely indicate shallow concentrations of heavy mineral sediments. Piston core layers and black sand beach samples exhibit enhanced magnetic susceptibilities and carry remanent magnetization, with mineralogical analyses indicating ilmenite and trace magnetite and/or maghemite and hematite. The anomalies are subtle and would be filtered as noise using traditional approaches, but can instead be highlighted using spectral methods, thus providing nearly continuous coverage along survey tracks. The distribution of the anomalies provides constraints on relevant sorting mechanisms. Comparisons to sonar data and previous grab samples show that two of three areas surveyed exhibit short-wavelength anomalies that are clustered over sand-covered areas, suggesting initial sorting through settling mechanisms. This is supported by a correlation between core magnetic susceptibility and grain size. Near the Choptank River, where sediment resuspension is wave-dominated, anomalies show a sharp decrease with seafloor depth that cannot be explained by signal attenuation alone. In Pocomoke Sound, where both tidal currents and wave-action impact sediment resuspension, anomalies show a more gradual decrease with depth. Near the mouth of the bay, where there is a higher influx of sediments from the continental shelf, short-wavelength anomalies are isolated and do not appear to represent heavy mineral sand concentrations. These combined observations suggest the importance of further sorting by erosional processes in certain parts of the bay. Additionally, comparisons of these data to cores sampling pre-Holocene sediments suggest that the sorting of heavy minerals in higher energy, shallow water environments provides a mechanism for correlations between core magnetic susceptibility and sea-level changes.

Seismic reflection and vibracoring studies of the continental shelf offshore central and western Long Island, New York

USGS Publications Warehouse

Kelly, W.M.; Albanese, J.R.; Coch, N.K.; Harsch, A.A.

1999-01-01

The ridge-and-swale topography on the continental shelf south of Fire Island, New York, is characterized by northeast-trending linear shoals that are shore attached and shore oblique on the inner shelf and isolated and shore parallel on the middle shelf. High-resolution seismic reflection profiles show that the ridges and swales occur independent of, and are not controlled by, the presence of internal structures (for example, filled tidal inlet channels, paleobarrier strata) or underlying structure (for example, high-relief Cretaceous unconformity). Grab samples of surficial sediments on the shelf south of Fire Island average 98% sand. Locally, benthic fauna increase silt and clay content through fecal pellet production or increase the content of gravel-size material by contribution of their fragmented shell remains. Surficial sand on the ridges is unimodal at 0.33 mm (medium sand, about 50 mesh), and surficial sand in troughs is bimodal at 0.33 mm and 0.15 mm (fine sand, about 100 mesh). In addition to seismic studies, 26 vibracores were recovered from the continental shelf in state and federal waters from south of Rockaway and Long Beaches, Long Island, New York. Stratigraphic and sedimentological data gleaned from these cores were used to outline the geologic framework in the study area. A variety of sedimentary features were noted in the cores, including burrow-mottled sections of sand in a finer silty-sand, rhythmic lamination of sand and silty-sand that reflect cyclic changes in sediment transport, layers of shell hash and shells that probably represent tempestites, and changes from dark color to light color in the sediments that probably represent changes in the oxidation-reduction conditions in the area with time. The stratigraphic units identified are an upper, generally oxidized, nearshore facies, an underlying fine- to medium-sand and silty-clay unit considered to be an estuarine facies, and a lower, coarse-grained deeply oxidized, cross-laminated pre-Holocene unit. Grain-size analysis shows that medium- to fine-grained sand makes up most (68-99%) of the surficial sediments. Gravel exists in trace amounts up to 19%. Silt ranges between 3% and 42% and clay ranges from 1% to 10%.The ridge-and-swale topography on the continental shelf south of Fire Island, New York, is characterized by northeast-trending linear shoals that are shore attached and shore oblique on the inner shelf and isolated and shore parallel on the middle shelf. High-resolution seismic reflection profiles show that the ridges and swales occur independent of, and are not controlled by, the presence of internal structures (for example, filled tidal inlet channels, paleobarrier strata) or underlying structure (for example, high-relief Cretaceous unconformity). Grab samples of surficial sediments on the shelf south of Fire Island average 98% sand. Locally, benthic fauna increase silt and clay content through fecal pellet production or increase the content of gravel-size material by contribution of their fragmented shell remains. Surficial sand on the ridges is unimodal at 0.33 mm (medium sand, about 50 mesh), and surficial sand in troughts is bimodal at 0.33 mm and 0.15 mm (fine sand, about 100 mesh). In addition to seismic studies, 26 vibracores were recovered from the continental shelf in state and federal waters from south of Rockaway and Long Beaches, Long Island, New York. Stratigraphic and sedimentological data gleaned from these cores were used to outline the geologic framework in the study area. A variety of sedimentary features were noted in the cores, including burrow-mottled sections of sand in a finer silty-sand, rhythmic lamination of sand and silty-sand that reflect cyclic changes in sediment transport, layers of shell hash and shells that probably represent tempestites, and changes from dark color to light color in the sediments that probably represent changes in the oxidation-reduction conditions in the area with time. The stratigraphic un

Re-Evaluating the Geological Evidence for Late Holocene Marine Incursion Events along the Guerrero Seismic Gap on the Pacific Coast of Mexico

PubMed Central

Bianchette, Thomas A.

2016-01-01

Despite the large number of tsunamis that impact Mexico’s Pacific coast, stratigraphic studies focusing on geological impacts are scanty, making it difficult to assess the long-term risks for this vulnerable region. Surface samples and six cores were taken from Laguna Mitla near Acapulco to examine sedimentological and geochemical evidence for marine incursion events. Sediment cores collected from behind the beach barrier are dominated by intercalated layers of peat and inorganic sediments, mostly silt and clay, with little or no sand. Sand- and shell-rich clastic layers with high levels of sulfur, calcium, and strontium only occur adjacent to the relict beach ridge remnants near the center of the lagoon. With the exception of one thin fine sand layer, the absence of sand in the near-shore cores and the predominance of the terrigenous element titanium in the inorganic layers, evidently eroded from the surrounding hillslopes, suggests that these large-grained intervals do not represent episodic marine incursions, but rather were likely formed by the erosion and redeposition of older marine deposits derived from the beach ridge remnants when water levels were high. These results do not support the occurrence of a large tsunami event at Laguna Mitla during the Late Holocene. PMID:27571270

Re-Evaluating the Geological Evidence for Late Holocene Marine Incursion Events along the Guerrero Seismic Gap on the Pacific Coast of Mexico.

PubMed

Bianchette, Thomas A; McCloskey, Terrence A; Liu, Kam-Biu

2016-01-01

Despite the large number of tsunamis that impact Mexico's Pacific coast, stratigraphic studies focusing on geological impacts are scanty, making it difficult to assess the long-term risks for this vulnerable region. Surface samples and six cores were taken from Laguna Mitla near Acapulco to examine sedimentological and geochemical evidence for marine incursion events. Sediment cores collected from behind the beach barrier are dominated by intercalated layers of peat and inorganic sediments, mostly silt and clay, with little or no sand. Sand- and shell-rich clastic layers with high levels of sulfur, calcium, and strontium only occur adjacent to the relict beach ridge remnants near the center of the lagoon. With the exception of one thin fine sand layer, the absence of sand in the near-shore cores and the predominance of the terrigenous element titanium in the inorganic layers, evidently eroded from the surrounding hillslopes, suggests that these large-grained intervals do not represent episodic marine incursions, but rather were likely formed by the erosion and redeposition of older marine deposits derived from the beach ridge remnants when water levels were high. These results do not support the occurrence of a large tsunami event at Laguna Mitla during the Late Holocene.

Clean and Secure Energy from Domestic Oil Shale and Oil Sands Resources

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

Spinti, Jennifer; Birgenheier, Lauren; Deo, Milind

This report summarizes the significant findings from the Clean and Secure Energy from Domestic Oil Shale and Oil Sands Resources program sponsored by the Department of Energy through the National Energy Technology Laboratory. There were four principle areas of research; Environmental, legal, and policy issues related to development of oil shale and oil sands resources; Economic and environmental assessment of domestic unconventional fuels industry; Basin-scale assessment of conventional and unconventional fuel development impacts; and Liquid fuel production by in situ thermal processing of oil shale Multiple research projects were conducted in each area and the results have been communicated viamore » sponsored conferences, conference presentations, invited talks, interviews with the media, numerous topical reports, journal publications, and a book that summarizes much of the oil shale research relating to Utah’s Uinta Basin. In addition, a repository of materials related to oil shale and oil sands has been created within the University of Utah’s Institutional Repository, including the materials generated during this research program. Below is a listing of all topical and progress reports generated by this project and submitted to the Office of Science and Technical Information (OSTI). A listing of all peer-reviewed publications generated as a result of this project is included at the end of this report; Geomechanical and Fluid Transport Properties 1 (December, 2015); Validation Results for Core-Scale Oil Shale Pyrolysis (February, 2015); and Rates and Mechanisms of Oil Shale Pyrolysis: A Chemical Structure Approach (November, 2014); Policy Issues Associated With Using Simulation to Assess Environmental Impacts (November, 2014); Policy Analysis of the Canadian Oil Sands Experience (September, 2013); V-UQ of Generation 1 Simulator with AMSO Experimental Data (August, 2013); Lands with Wilderness Characteristics, Resource Management Plan Constraints, and Land Exchanges (March, 2012); Conjunctive Surface and Groundwater Management in Utah: Implications for Oil Shale and Oil Sands Development (May, 2012); Development of CFD-Based Simulation Tools for In Situ Thermal Processing of Oil Shale/Sands (February, 2012); Core-Based Integrated Sedimentologic, Stratigraphic, and Geochemical Analysis of the Oil Shale Bearing Green River Formation, Uinta Basin, Utah (April, 2011); Atomistic Modeling of Oil Shale Kerogens and Asphaltenes Along with their Interactions with the Inorganic Mineral Matrix (April, 2011); Pore Scale Analysis of Oil Shale/Sands Pyrolysis (March, 2011); Land and Resource Management Issues Relevant to Deploying In-Situ Thermal Technologies (January, 2011); Policy Analysis of Produced Water Issues Associated with In-Situ Thermal Technologies (January, 2011); and Policy Analysis of Water Availability and Use Issues for Domestic Oil Shale and Oil Sands Development (March, 2010)« less

Sediment data collected in 2013 from the northern Chandeleur Islands, Louisiana

USGS Publications Warehouse

Buster, Noreen A.; Kelso, Kyle W.; Bernier, Julie C.; Flocks, James G.; Miselis, Jennifer L.; DeWitt, Nancy T.

2014-01-01

This data series serves as an archive of sediment data collected in July 2013 from the Chandeleur Islands sand berm and adjacent barrier-island environments. Data products include descriptive core logs, core photographs and x-radiographs, results of sediment grain-size analyses, sample location maps, and Geographic Information System data files with accompanying formal Federal Geographic Data Committee metadata.

Physical property changes in hydrate-bearing sediment due to depressurization and subsequent repressurization

USGS Publications Warehouse

Waite, W.F.; Kneafsey, T.J.; Winters, W.J.; Mason, D.H.

2008-01-01

Physical property measurements of sediment cores containing natural gas hydrate are typically performed on material exposed, at least briefly, to non-in situ conditions during recovery. To examine the effects of a brief excursion from the gas-hydrate stability field, as can occur when pressure cores are transferred to pressurized storage vessels, we measured physical properties on laboratory-formed sand packs containing methane hydrate and methane pore gas. After depressurizing samples to atmospheric pressure, we repressurized them into the methane-hydrate stability field and remeasured their physical properties. Thermal conductivity, shear strength, acoustic compressional and shear wave amplitudes, and speeds of the original and depressurized/repressurized samples are compared. X– ray computed tomography images track how the gas-hydrate distribution changes in the hydrate-cemented sands owing to the depressurizaton/repressurization process. Because depressurization-induced property changes can be substantial and are not easily predicted, particularly in water-saturated, hydrate-bearing sediment, maintaining pressure and temperature conditions throughout the core recovery and measurement process is critical for using laboratory measurements to estimate in situ properties.

Physical property changes in hydrate-bearing sediment due to depressurization and subsequent repressurization

USGS Publications Warehouse

Waite, W.F.; Kneafsey, T.J.; Winters, W.J.; Mason, D.H.

2008-01-01

Physical property measurements of sediment cores containing natural gas hydrate are typically performed on material exposed, at least briefly, to non-in situ conditions during recovery. To examine the effects of a brief excursion from the gas-hydrate stability field, as can occur when pressure cores are transferred to pressurized storage vessels, we measured physical properties on laboratory-formed sand packs containing methane hydrate and methane pore gas. After depressurizing samples to atmospheric pressure, we repressurized them into the methane-hydrate stability field and remeasured their physical properties. Thermal conductivity, shear strength, acoustic compressional and shear wave amplitudes, and speeds of the original and depressurized/repressurized samples are compared. X-ray computed tomography images track how the gas-hydrate distribution changes in the hydrate-cemented sands owing to the depressurizaton/repressurization process. Because depressurization-induced property changes can be substantial and are not easily predicted, particularly in water-saturated, hydrate-bearing sediment, maintaining pressure and temperature conditions throughout the core recovery and measurement process is critical for using laboratory measurements to estimate in situ properties.

Heat-resistant agent used for control sand of steam huff and puff heavy oil well

NASA Astrophysics Data System (ADS)

Zhang, F. S.; Liu, G. L.; Lu, Y. J.; Xiong, X. C.; Ma, J. H.; Su, H. M.

2018-01-01

Heat-resistant agent containing hydroxymethyl group was synthesized from coal tar, which has similar structure with phenolic resin and could improve the heat resistance of phenolic resin sand control agent. The results showed that the heat resistance of the sand control agent was improved by adding 10% to 30% heat-resistant agent, after 280°C high temperature treatment for 7d, the compressive strength of consolidated core was increased to more than 5MPa. The compressive strength of consolidation core was not decreased after immersion in formation water, crude oil, acid or alkaline medium, which showed good resistance to medium immersion. The sand control agent had small core damage and the core permeability damage ratio of sand control agent consolidation was only 18.7%.

Sedimentary controls on modern sand grain coat formation

NASA Astrophysics Data System (ADS)

Dowey, Patrick J.; Worden, Richard H.; Utley, James; Hodgson, David M.

2017-05-01

Coated sand grains can influence reservoir quality evolution during sandstone diagenesis. Porosity can be reduced and fluid flow restricted where grain coats encroach into pore space. Conversely pore-lining grain coats can restrict the growth of pore-filling quartz cement in deeply buried sandstones, and thus can result in unusually high porosity in deeply buried sandstones. Being able to predict the distribution of coated sand grains within petroleum reservoirs is thus important to help find good reservoir quality. Here we report a modern analogue study of 12 sediment cores from the Anllóns Estuary, Galicia, NW Spain, collected from a range of sub-environments, to help develop an understanding of the occurrence and distribution of coated grains. The cores were described for grain size, bioturbation and sedimentary structures, and then sub-sampled for electron and light microscopy, laser granulometry, and X-ray diffraction analysis. The Anllóns Estuary is sand-dominated with intertidal sand flats and saltmarsh environments at the margins; there is a shallowing/fining-upwards trend in the estuary-fill succession. Grain coats are present in nearly every sample analysed; they are between 1 μm and 100 μm thick and typically lack internal organisation. The extent of grain coat coverage can exceed 25% in some samples with coverage highest in the top 20 cm of cores. Samples from muddy intertidal flat and the muddy saltmarsh environments, close to the margins of the estuary, have the highest coat coverage (mean coat coverage of 20.2% and 21.3%, respectively). The lowest mean coat coverage occurs in the sandy saltmarsh (10.4%), beyond the upper tidal limit and sandy intertidal flat environments (8.4%), close to the main estuary channel. Mean coat coverage correlates with the concentration of clay fraction. The primary controls on the distribution of fine-grained sediment, and therefore grain coat distribution, are primary sediment transport and deposition processes that concentrate the clay fraction in the sediment towards the margins of the estuary. Bioturbation and clay illuviation/mechanical infiltration are secondary processes that may redistribute fine-grained sediment and produce grain coats. Here we have shown that detrital grain coats are more likely in marginal environments of ancient estuary-fills, which are typically found in the fining-upward part of progradational successions.

Environmental implications of the use of sulfidic back-bay sediments for dune reconstruction — Lessons learned post Hurricane Sandy

USGS Publications Warehouse

Plumlee, Geoffrey S.; Benzel, William M.; Hoefen, Todd M.; Hageman, Philip L.; Morman, Suzette A.; Reilly, Timothy J.; Adams, Monique; Berry, Cyrus J.; Fischer, Jeffrey; Fisher, Irene

2016-01-01

Some barrier-island dunes damaged or destroyed by Hurricane Sandy's storm surges in October 2012 have been reconstructed using sediments dredged from back bays. These sand-, clay-, and iron sulfide-rich sediments were used to make berm-like cores for the reconstructed dunes, which were then covered by beach sand. In November 2013, we sampled and analyzed partially weathered materials collected from the cores of reconstructed dunes. There are generally low levels of metal toxicants in the reconstructed dune materials. However oxidation of reactive iron sulfides by percolating rainwater produces acid-sulfate pore waters, which evaporate during dry periods to produce efflorescent gypsum and sodium jarosite salts. The results suggest use of sulfidic sediments in dune reconstruction has both drawbacks (e.g., potential to generate acid runoff from dune cores following rainfall, enhanced corrosion of steel bulwarks) and possible benefits (e.g., efflorescent salts may enhance structural integrity).

UT-GOM2-1: Prospecting, Drilling and Sampling a Coarse-Grained Hydrate Reservoir in Green Canyon 955, the Deepwater Gulf of Mexico

NASA Astrophysics Data System (ADS)

Flemings, P. B.; Phillips, S. C.

2017-12-01

In May 2017, a science team led by the University of Texas-Austin conducted drilling and coring operations from the Helix Q4000 targeting gas hydrates in sand-rich reservoirs in the Green Canyon 955 block in the northern Gulf of Mexico. The UT-GOM2-1 expedition goals were to 1) test two configurations of pressure coring devices to assess relative performance with respect to recovery and quality of samples and 2) gather sufficient samples to allow laboratories throughout the US to investigate a range of outstanding science questions related to the origin and nature of gas hydrate-bearing sands. In the first well (UT-GOM2-1-H002), 1 of the 8 cores were recovered under pressure with 34% recovery. In the second well (UT-GOM2-1-H005), 12 of 13 cores were recovered under pressure with 77% recovery. The pressure cores were imaged and logged under pressure. Samples were degassed both shipboard and dockside to interpret hydrate concentration and gas composition. Samples for microbiological and porewater analysis were taken from the depressurized samples. 21 3 ft pressure cores were returned to the University of Texas for storage, distribution, and further analysis. Preliminary analyses document that the hydrate-bearing interval is composed of two interbedded (cm to m thickness) facies. Lithofacies II is composed of sandy silt and has trough cross bedding whereas Lithofacies III is composed of clayey silt and no bedforms are observed. Lithofacies II has low density (1.7 to 1.9 g/cc) and high velocity (3000-3250 m/s) beds whereas Lithofacies 3 has high density ( 1.9-2.1g/cc) and low velocity ( 1700 m/s). Quantitative degassing was used to determine that Lithofacies II contains high hydrate saturation (66-87%) and Lithofacies III contains moderate saturation ( 18-30%). Gas samples were analyzed periodically in each experiment and were composed of primarily methane with an average of 94 ppm ethane and detectable, but not quantifiable, propane. The core data will provide a foundation for scientific exploration by the greater hydrate research community.

Seabed texture and composition changes offshore of Port Royal Sound, South Carolina before and after the dredging for beach nourishment

NASA Astrophysics Data System (ADS)

Xu, Kehui; Sanger, Denise; Riekerk, George; Crowe, Stacie; Van Dolah, Robert F.; Wren, P. Ansley; Ma, Yanxia

2014-08-01

Beach nourishment has been a strategy widely used to slow down coastal erosion in many beaches around the world. The dredging of sand at the borrow site, however, can have complicated physical, geological and ecological impacts. Our current knowledge is insufficient to make accurate predictions of sediment infilling in many dredging pits due to lack of detailed sediment data. Two sites in the sandy shoal southeast of Port Royal Sound (PRS) of South Carolina, USA, were sampled 8 times from April 2010 to March 2013; one site (defined as 'borrow site') was 2 km offshore and used as the dredging site for beach nourishment of nearby Hilton Head Island in Beaufort County, South Carolina, and the other site (defined as 'reference site') was 10 km offshore and not directly impacted by the dredging. A total of 184 surficial sediment samples were collected randomly at two sites during 8 sampling periods. Most sediments were fine sand, with an average grain size of 2.3 phi and an organic matter content less than 2%. After the dredging in December 2011-January 2012, sediments at the borrow site became finer, changing from 1.0 phi to 2.3 phi, and carbonate content decreased from 10% to 4%; changes in mud content and organic matter were small. Compared with the reference site, the borrow site experienced larger variations in mud and carbonate content. An additional 228 sub-samples were gathered from small cores collected at 5 fixed stations in the borrow site and 1 fixed station at the reference site 0, 3, 6, 9, and 12 months after the dredging; these down-core sub-samples were divided into 1-cm slices and analyzed using a laser diffraction particle size analyzer. Most cores were uniform vertically and consisted of fine sand with well to moderately well sorting and nearly symmetrical averaged skewness. Based on the analysis of grain size populations, 2 phi- and 3 phi-sized sediments were the most dynamic sand fractions in PRS. Mud deposition on shoals offshore of PRS presumably happens when offshore mud transport is prevalent and there is a following rapid sand accumulation to bury the mud. However, in this borrow site there was very little accumulation of mud. This will allow the site to be used in future nourishment projects presuming no accumulation of mud occurs in the future.

29. DEPENDABLE FORDATHSHELL CORE MACHINES IN THE GREY IRON FOUNDRY ...

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

29. DEPENDABLE FORDATH-SHELL CORE MACHINES IN THE GREY IRON FOUNDRY INJECTS SAND INTO A CLOSED CORE BOX. SOME OF THE UNITS HEAT THE CORE BOX TO FIX THE RESINS AS THE CORE REMAINS IN THE BOX, OTHERS MERELY SHAPED THE CORE SAND REQUIRING BAKING OF THE CORES TO HARDEN THEM. - Stockham Pipe & Fittings Company, Grey Iron Foundry, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

Geologic logs of geotechnical cores from the subsurface Sacramento-San Joaquin Delta, California

USGS Publications Warehouse

Maier, Katherine L.; Ponti, Daniel J.; Tinsley, John C.; Gatti, Emma; Pagenkopp, Mark

2014-01-01

This report presents and summarizes descriptive geologic logs of geotechnical cores collected from 2009–12 in the Sacramento–San Joaquin Delta, California, by the California Department of Water Resources. Graphic logs are presented for 1,785.7 ft of retained cores from 56 borehole sites throughout the Sacramento-San Joaquin Delta. Most core sections are from a depth of ~100–200 feet. Cores primarily contain mud, silt, and sand lithologies. Tephra (volcanic ash and pumice), paleosols, and gravels are also documented in some core sections. Geologic observations contained in the core logs in this report provide stratigraphic context for subsequent sampling and data for future chronostratigraphic subsurface correlations.

Large-scale natural gradient tracer test in sand and gravel, Cape Cod, Massachusetts: 3. Hydraulic conductivity variability and calculated macrodispersivities

USGS Publications Warehouse

Hess, Kathryn M.; Wolf, Steven H.; Celia, Michael A.

1992-01-01

Hydraulic conductivity (K) variability in a sand and gravel aquifer on Cape Cod, Massachusetts, was measured and subsequently used in stochastic transport theories to estimate macrodispersivities. Nearly 1500 K measurements were obtained by borehole flowmeter tests and permeameter analyses of cores. The geometric mean for the flowmeter tests (0.11 cm/s) is similar to that estimated from other field tests. The mean for the permeameter tests (0.035 cm/s) is significantly lower, possibly because of compaction of the cores. The variance for the flowmeter (0.24) is also greater than that for the permeameter (0.14). Geostatistical analyses applying negative exponential models with and without nuggets reveal similar spatial correlation structures for the two data sets. Estimated correlation scales range from 2.9 to 8 m in the horizontal and from 0.18 to 0.38 m in the vertical. Estimates of asymptotic longitudinal dispersivity (b.35–0.78 m) are similar in magnitude to that observed in the natural gradient tracer test (0.96 m) previously conducted at this site.

Test well DO-CE 88 at Cambridge, Dorchester County, Maryland

USGS Publications Warehouse

Trapp, Henry; Knobel, LeRoy L.; Meisler, Harold; Leahy, P. Patrick

1984-01-01

Test well DO-CE 88 at Cambridge, Maryland, penetrated 3,299 feet of unconsolidated Quaternary, Tertiary and Cretaceous sediments and bottomed in quartz-monzonite gneiss. The well was drilled to provide data for a study of the aquifer system of the northern Atlantic Coastal Plain. Twenty-one core samples were collected. Six sand zones were tested for aquifer properties and sampled for ground-water chemistry. Point-water heads were measured at seven depths. Environmental heads (which ranged from - 18.33 to + 44.16 feet relative to sea level)indicate an upward component of flow. A temperature log showed a maximum temperature of 41.9 degrees Celsius and a mean temperature gradient of 0.00838 degrees Celsius per foot. The water analyses delineated the freshwater-saltwater transition zone between 2,650 and 3,100 feet. The ground water changes progressively downward from a sodium bicarbonate to a sodium chloride character. Clays in the analyzed core samples belong to the montmorillonite and kaolinite groups, and mean cation exchange capacity ranged from 8.3 to 38.9 milliequivalents per 100 grams. Vertical and horizontal hydraulic conductivities measured in cores ranged from 1.5 x 10 6 to 1.3 feet per day and from 7.3 x 10 -6 to 1.3 feet per day, respectively, but the most permeable sands were not cored. Porosity was 1.5 percent in the quartz monzonite bedrock and ranged from 22.4 to 41 percent in the overlying sediments. Transmissivities from aquifer tests ranged from 25 to 850 feet squared per day; horizontal hydraulic conductivities ranged from.2.5 to 85 feet squared per day, and intrinsic permeabilities ranged from 0.8 to 23 micrometers squared. Fossils identified in core samples include palynomorphs, dinoflagellates, and foraminifers.

Collecting Ground Samples for Balloon-Borne Instruments

NASA Technical Reports Server (NTRS)

Jones, Jack; Zimmerman, Wayne; Wu, Jiunn Jenq

2009-01-01

A proposed system in a gondola containing scientific instruments suspended by a balloon over the surface of the Saturn moon Titan would quickly acquire samples of rock or ice from the ground below. Prototypes of a sample-collecting device that would be a major part of the system have been tested under cryogenic and non-cryogenic conditions on Earth. Systems like this one could also be used in non-cryogenic environments on Earth to collect samples of rock, soil, ice, mud, or other ground material from such inaccessible or hazardous locations as sites of suspected chemical spills or biological contamination. The sample-collecting device would be a harpoonlike device that would be connected to the balloon-borne gondola by a tether long enough to reach the ground. The device would be dropped from the gondola to acquire a sample, then would be reeled back up to the gondola, where the sample would be analyzed by the onboard instruments. Each prototype of the sample-collecting device has a sharp front (lower) end, a hollow core for retaining a sample, a spring for holding the sample in the hollow core, and a rear (upper) annular cavity for retaining liquid sample material. Aerodynamic fins at the rear help to keep the front end pointed downward. In tests, these prototype devices were dropped from various heights and used to gather samples of dry sand, moist sand, cryogenic water ice, and warmer water ice.

Depleted uranium investigation at missile impact sites in White Sands Missile Range

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

Van Etten, D.M.; Purtymun, W.D.

1994-01-01

An investigation for residual depleted uranium was conducted at Pershing missile impact sites on the White Sands Missile Range. Subsurface core soil samples were taken at Chess, Salt Target, and Mine Impact Sites. A sampling pump was installed in a monitoring well at Site 65 where a Pershing earth penetrator was not recovered. Pumping tests and water samples were taken at this site. Chess Site, located in a gypsum flat, was the only location showing elevated levels of depleted uranium in the subsurface soil or perched groundwater. Small fragments can still be found on the surface of the impact sites.more » The seasonal flooding and near surface water has aided in the movement of surface fragments.« less

Leaching characteristics of encapsulated controlled low-strength materials containing arsenic-bearing waste precipitates from refractory gold bioleaching.

PubMed

Bouzalakos, S; Dudeney, A W L; Chan, B K C

2016-07-01

We report on the leaching of heavy elements from cemented waste flowable fill, known as controlled low-strength materials (CLSM), for potential mine backfill application. Semi-dynamic tank leaching tests were carried out on laboratory-scale monoliths cured for 28 days and tested over 64 days of leaching with pure de-ionised water as leachant. Mineral processing waste include flotation tailings from a Spanish nickel-copper sulphide concentrate, and two bioleach neutralisation precipitates (from processing at 35°C and 70°C) from a South African arsenopyrite concentrate. Encapsulated CLSM formulations were evaluated to assess the reduction in leaching by encapsulating a 'hazardous' CLSM core within a layer of relatively 'inert' CLSM. The effect of each bioleach waste in CLSM core and tailings in CLSM encapsulating medium, are assessed in combination and in addition to CLSM with ordinary silica sand. Results show that replacing silica sand with tailings, both as core and encapsulating matrix, significantly reduced leachability of heavy elements, particularly As (from 0.008-0.190 mg/l to 0.008-0.060 mg/l), Ba (from 0.435-1.540 mg/l to 0.050-0.565 mg/l), and Cr (from 0.006-0.458 mg/l to 0.004-0.229 mg/l), to below the 'Dutch List' of groundwater contamination intervention values. Arsenic leaching was inherently high from both bioleach precipitates but was significantly reduced to below guideline values with encapsulation and replacing silica sand with tailings. Tailings proved to be a valuable encapsulating matrix largely owing to small particle size and lower hydraulic conductivity reducing diffusion transport of heavy elements. Field-scale trials would be necessary to prove this concept of encapsulation in terms of scale and construction practicalities, and further geochemical investigation to optimise leaching performance. Nevertheless, this work substantiates the need for alternative backfill techniques for sustainable management of hazardous finely-sized bulk mineral residues. Copyright © 2016 Elsevier Ltd. All rights reserved.

INNOVATIVE MIOR PROCESS UTILIZING INDIGENOUS RESERVOIR CONSTITUENTS

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

D.O. Hitzman; S.A. Bailey

This research program is directed at improving the knowledge of reservoir ecology and developing practical microbial solutions for improving oil production. The goal is to identify indigenous microbial populations which can produce beneficial metabolic products and develop a methodology to stimulate those select microbes with inorganic nutrient amendments to increase oil recovery.This microbial technology has the capability of producing multiple oil releasing agents. The potential of the system will be illustrated and demonstrated by the example of biopolymer production on oil recovery. Research has begun on the program and experimental laboratory work is underway. Polymer-producing cultures have been isolated frommore » produced water samples and initially characterized. Concurrently, a microcosm scale sand-packed column has been designed and developed for testing cultures of interest, including polymer-producing strains. In research that is planned to begin in future work, comparative laboratory studies demonstrating in situ production of microbial products as oil recovery agents will be conducted in sand pack and cores with synthetic and natural field waters at concentrations, flooding rates, and with cultures and conditions representative of oil reservoirs.« less

Examination of core samples from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Effects of retrieval and preservation

USGS Publications Warehouse

Kneafsey, T.J.; Lu, H.; Winters, W.; Boswell, R.; Hunter, R.; Collett, T.S.

2011-01-01

Collecting and preserving undamaged core samples containing gas hydrates from depth is difficult because of the pressure and temperature changes encountered upon retrieval. Hydrate-bearing core samples were collected at the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well in February 2007. Coring was performed while using a custom oil-based drilling mud, and the cores were retrieved by a wireline. The samples were characterized and subsampled at the surface under ambient winter arctic conditions. Samples thought to be hydrate bearing were preserved either by immersion in liquid nitrogen (LN), or by storage under methane pressure at ambient arctic conditions, and later depressurized and immersed in LN. Eleven core samples from hydrate-bearing zones were scanned using x-ray computed tomography to examine core structure and homogeneity. Features observed include radial fractures, spalling-type fractures, and reduced density near the periphery. These features were induced during sample collection, handling, and preservation. Isotopic analysis of the methane from hydrate in an initially LN-preserved core and a pressure-preserved core indicate that secondary hydrate formation occurred throughout the pressurized core, whereas none occurred in the LN-preserved core, however no hydrate was found near the periphery of the LN-preserved core. To replicate some aspects of the preservation methods, natural and laboratory-made saturated porous media samples were frozen in a variety of ways, with radial fractures observed in some LN-frozen sands, and needle-like ice crystals forming in slowly frozen clay-rich sediments. Suggestions for hydrate-bearing core preservation are presented.

Experimental and Numerical Observations of Hydrate Reformation during Depressurization in a Core-Scale Reactor

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

Seol, Yongkoo; Myshakin, Evgeniy

2011-01-01

Gas hydrate has been predicted to reform around a wellbore during depressurization-based gas production from gas hydrate-bearing reservoirs. This process has an adverse effect on gas production rates and it requires time and sometimes special measures to resume gas flow to producing wells. Due to lack of applicable field data, laboratory scale experiments remain a valuable source of information to study hydrate reformation. In this work, we report laboratory experiments and complementary numerical simulations executed to investigate the hydrate reformation phenomenon. Gas production from a pressure vessel filled with hydrate-bearing sand was induced by depressurization with and without heat fluxmore » through the boundaries. Hydrate decomposition was monitored with a medical X-ray CT scanner and pressure and temperature measurements. CT images of the hydrate-bearing sample were processed to provide 3-dimensional data of heterogeneous porosity and phase saturations suitable for numerical simulations. In the experiments, gas hydrate reformation was observed only in the case of no-heat supply from surroundings, a finding consistent with numerical simulation. By allowing gas production on either side of the core, numerical simulations showed that initial hydrate distribution patterns affect gas distribution and flow inside the sample. This is a direct consequence of the heterogeneous pore network resulting in varying hydraulic properties of the hydrate-bearing sediment.« less

Improvement of core drill methods

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

Gatz, J.L.

1975-07-01

This report documents results of a program to evaluate effectiveness of more or less conventional subsurface samplers in obtaining representative and undisturbed samples of noncohesive alluvial materials containing large quantities of gravels and cobbles. This is the first phase of a research program to improve core drill methods. Samplers evaluated consisted of the Lawrence Livermore Laboratory membrane sampler, 4-in. Denison sampler, 6-in. Dension sampler, 5-in. Modified Denison sampler, and 3-in. thinwall drive tube. Small representative samples were obtained with the Dension samplers; no undisturbed samples were obtained. The field work was accomplished in the Rhodes Canyon area, White Sands Misslemore » Range, New Mexico.« less

Hydroacoustic signatures of Colorado Riverbed sediments in Marble and Grand Canyons using multibeam sonar

USGS Publications Warehouse

Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matthew; Tusso, Robert B.; Rubin, David M.

2015-01-01

Characterizing the large-scale sedimentary make-up of heterogeneous riverbeds (Nelson et al., 2014), which consist of a patchwork of sediment types over small scales (less than one to several tens of meters) (Dietrich and Smith, 1984) requires high resolution measurements of sediment grain size. Capturing such variability with conventional physical (e.g. grabs, cores, and dredges) or underwater photographic sampling (Rubin et al., 2007; Buscombe et al., 2014a) would be prohibitively costly and time-consuming. However, characterizing bed sediments using high-frequency (several hundred kilohertz) acoustic backscatter from swath-mapping systems has the potential to provide near complete coverage of the bed (Brown and Blondel, 2009; Brown et al., 2011; Snellen et al., 2013), at resolutions down to a few centimeters, which photographic sampling could not practically achieve within the same time and with the same positional accuracy. In shallow water, the physics of high frequency scattering of sound are relatively poorly understood, therefore acoustic sediment classification are almost always statistical (Snellen et al., 2013). Many such methods proposed to date are designed for characterizing large areas of seabed (Brown and Blondel, 2009; Brown et al., 2011) at relatively poor resolution (tens of meters to several hundred meters) and therefore rely on aggregation of data over scales much larger than the typical scales of sediment patchiness on heterogeneous riverbeds. In response to this need, Buscombe et al. (2014b, 2014c) developed a new statistical method for acoustic sediment classification based on spectral analysis of backscatter. This method is both continuous in coverage and of sufficient resolution (order meter or less) to characterize sediment variability on patchy riverbeds. Here, we apply these methods to multibeam echosounder (MBES) data collected from the bed of the Colorado River in Marble and Grand Canyons. Sediment dynamics on the Colorado River in Grand Canyon National Park have been studied for several decades (e.g. Howard and Dolan, 1981; Rubin et al., 2002). Particular focus has been given to sandbars in large eddies downstream of tributary debris fans (Schmidt, 1990) because they are considered valuable resources by stakeholders and managers. Due to the severe limitations in sand supply imposed by Glen Canyon Dam (Howard and Dolan, 1981; Topping et al., 2000; Hazel et al., 2006), understanding the effectiveness of sandbar management practices, such as controlled floods (Rubin et al. 2002; Topping et al., 2006; Hazel et al., 2010), and the long-term fate of sand in Grand Canyon over decadal timescales, requires construction of accurate sand budgets, which involves detailed monitoring of influx, efflux and changes in sand storage (Topping et al., 2000; Topping et al., 2010; Grams et al., 2013) and assessments of uncertainties in sand-budget calculations (Grams et al., 2013). In order to estimate the sand budget, it is necessary to estimate what component of observed morphological changes is sand and what component is coarser. Grams et al. (2013) classified sand and coarse substrates using topographic roughness derived from digital elevation models, but the classification skill was estimated to be only 60-70%. In addition, sand bedforms had to be delineated manually, and validation was based on grain-size observations with positional uncertainties up to tens of meters. Because the morphology of the Colorado riverbed in Grand Canyon is mapped - to a large extent - using MBES (Kaplinski et al., 2009), the primary motivation for the present study is to examine how uncertainties in sand budgets can be constrained by producing maps of surface sediment types using the completely automated methods of Buscombe et al (2014b, 2014c) based on statistical analysis of MBES acoustic backscatter.

Deepwater Gulf of Mexico turbidites -- Compaction effects on porosity and permeability

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

Ostermeier, R.M.

1995-06-01

The deepwater Gulf of Mexico is now a major area of activity for the US oil industry. Compaction causes particular concern because most prospective deepwater reservoirs are highly geo-pressured and many have limited aquifer support; water injection may also be problematic. To address some of the issues associated with compaction, the authors initiated a special core-analysis program to study compaction effects on turbidite sand porosity and permeability specifically. This program also addressed a number of subsidiary but no less important issues, such as sample characterization and quality, sample preparation, and test procedures. These issues are particularly pertinent, because Gulf ofmore » Mexico turbidites are generally unconsolidated, loose sands, and are thus susceptible to a whole array of potentially serious core-disturbing processes. One key result of the special core analysis program is that turbidite compressibilities exhibit large variations in both magnitude and stress dependence. These variations correlate with creep response in the laboratory measurements. The effects of compaction on permeability are significant. To eliminate complicating effects caused by fines movement, the authors made oil flow measurements at initial water saturation. The measurements indicate compaction reduces permeability four to five times more than porosity on a relative basis.« less

Sedimentary Framework of an Inner Continental Shelf Sand-Ridge System, West-Central Florida

NASA Astrophysics Data System (ADS)

Locker, S. D.; Hine, A. C.; Wright, A. K.; Duncan, D. S.

2002-12-01

The west-central Florida inner continental shelf is a dynamic environment subject to current flows on a variety of temporal and spatial scales. A site survey program, undertaken in support of the Office of Naval Research's Mine Burial prediction program, is focused on the sedimentary framework and sediment accumulation patterns in 10-18 meters water depth. Our specific goals are to image the shallow subsurface and to monitor changes in bedform distribution patterns that coincide with physical processes studies ongoing in the area. Methods of study include side-scan sonar imaging, boomer and chirp subbottom profiling, and sedimentary facies analysis using surface sediment sampling and vibracoring. A well-defined sand-ridge system was imaged, trending oblique to the west-Florida coastline. The side-scan clearly shows that there is extensive three-dimensional structure within these large-scale NW-SE trending sedimentary bedforms. The sand ridges commonly are approximately 1 km wide and 4-8 km in length. The characteristics of these ridges are distinctly different than the sand ridges in < 8 m water that we have previously studied. Ridges in the offshore area tend to be thicker, have a flatter morphology, and exhibit fewer smaller-scale sand waves. Sand-ridge thickness ranges 2-3 meters, and typically consists of fining upward medium to fine quartz sand facies with occasional centimeter-scale coarser-grained carbonate-rich intervals. Time series investigations tracking the shift in position of the sand ridge margins have found undetectable net annual movement. However significant resuspension and bedform development accompanies high-energy events such as winter cold front passage. Thus the large-scale bedforms (sand ridges) are in a state of dynamic equilibrium with the average annual hydrodynamic regime. Repeated field surveys will focus on monitoring small-scale sedimentological and stratal framework changes that will be integrated with the quantitative process studies.

Dynamics of sediments along with their core properties in the Monastir-Bekalta coastline (Tunisia, Central Mediterranean)

NASA Astrophysics Data System (ADS)

Khiari, Nouha; Atoui, Abdelfattah; Khalil, Nadia; Charef, Abdelkrim; Aleya, Lotfi

2017-10-01

The authors report on two campaigns of high-resolution samplings along the shores of Monastir Bay in Tunisia: the first being a study of sediment dynamics, grain size and mineral composition in surface sediment, and the second, eight months later, using four sediment cores to study grain-size distribution in bottom sediments. Particle size analysis of superficial sediment shows that the sand in shallow depths is characterized by S-shaped curves, indicating a certain degree of agitation, possible transport by rip currents near the bottom and hyperbolic curves illustrating heterogeneity of sand stock. The sediments settle in a relatively calm environment. Along the bay shore (from 0 to 2 m depth), the bottom is covered by medium sand. Sediment transport is noted along the coast; from north to south and from south to north, caused by longshore drift and a rip current in the middle of the bay. These two currents are generated by wind and swell, especially by north to northeast waves which transport the finest sediment. Particle size analysis of bottom sediment indicates a mean grain size ranging from coarse to very fine sands while vertical distribution of grain size tends to decrease from surface to depth. The increase in particle size of sediment cores may be due to the coexistence of terrigenous inputs along with the sedimentary transit parallel to the coast due to the effect of longshore drift. Mineralogical analysis shows that Monastir's coastal sands and bottom sediment are composed of quartz, calcite, magnesium calcite, aragonite and hematite. The existence of a low energy zone with potential to accumulate pollutants indicates that managerial action is necessary to help preserve Monastir Bay.

Geologic controls on regional and local erosion rates of three northern Gulf of Mexico barrier-island systems

USGS Publications Warehouse

Twitchell, David C.; Flocks, James G.; Pendleton, Elizabeth; Baldwin, Wayne E.

2013-01-01

The stratigraphy of sections of three barrier island systems in the northeastern Gulf of Mexico (Apalachicola, Mississippi, and Chandeleur) have been mapped using geophysical and coring techniques to assess the influence of geologic variations in barrier lithosomes and adjoining inner shelf deposits on long-term rates of shoreline change at regional and local scales. Regional scale was addressed by comparing average geologic characteristics of the three areas with mean shoreline-change rates for each area. Regionally, differences in sand volume contained within the part of the barrier lithosome above sea level, sand volume on the inner shelf, and to a lesser extent, sediment grain size correlate with shoreline change rates. Larger sand volumes and coarser grain sizes are found where erosion rates are lower. Local scale was addressed by comparing alongshore variations in barrier island and inner shelf geology with alongshore variations in shoreline change. Locally, long-term shoreline change rates are highest directly shoreward of paleovalleys exposed on the inner shelf. While geology is not the sole explanation for observed differences in shoreline change along these three coastal regions, it is a significant contributor to change variability.

From Pore to Core: Do Engineered Nanoparticles Violate Upscaling Assumptions? A Microtomographic Investigation

NASA Astrophysics Data System (ADS)

Molnar, I. L.; O'Carroll, D. M.; Gerhard, J.; Willson, C. S.

2014-12-01

The recent success in using Synchrotron X-ray Computed Microtomography (SXCMT) for the quantification of nanoparticle concentrations within real, three-dimensional pore networks [1] has opened up new opportunities for collecting experimental data of pore-scale flow and transport processes. One opportunity is coupling SXCMT with nanoparticle/soil transport experiments to provide unique insights into how pore-scale processes influence transport at larger scales. Understanding these processes is a key step in accurately upscaling micron-scale phenomena to the continuum-scale. Upscaling phenomena from the micron-scale to the continuum-scale typically involves the assumption that the pore space is well mixed. Using this 'well mixed assumption' it is implicitly assumed that the distribution of nanoparticles within the pore does not affect its retention by soil grains. This assumption enables the use of volume-averaged parameters in calculating transport and retention rates. However, in some scenarios, the well mixed assumption will likely be violated by processes such as deposition and diffusion. These processes can alter the distribution of the nanoparticles in the pore space and impact retention behaviour, leading to discrepancies between theoretical predictions and experimental observations. This work investigates the well mixed assumption by employing SXCMT to experimentally examine pore-scale mixing of silver nanoparticles during transport through sand packed columns. Silver nanoparticles were flushed through three different sands to examine the impact of grain distribution and nanoparticle retention rates on mixing: uniform silica (low retention), well graded silica sand (low retention) and uniform iron oxide coated silica sand (high retention). The SXCMT data identified diffusion-limited retention as responsible for violations of the well mixed assumption. A mathematical description of the diffusion-limited retention process was created and compared to the experimental data at the pore and column-scale. The mathematical description accurately predicted trends observed within the SXCMT-datasets such as concentration gradients away from grain surfaces and also accurately predicted total retention of nanoparticles at the column scale. 1. ES&T 2014, 48, (2), 1114-1122.

Radiocarbon dating of silica sinter deposits in shallow drill cores from the Upper Geyser Basin, Yellowstone National Park

USGS Publications Warehouse

Lowenstern, Jacob B.; Hurwitz, Shaul; McGeehin, John

2016-01-01

To explore the timing of hydrothermal activity at the Upper Geyser Basin (UGB) in Yellowstone National Park, we obtained seven new accelerator mass spectrometry (AMS) radiocarbon 14C ages of carbonaceous material trapped within siliceous sinter. Five samples came from depths of 15–152 cm within the Y-1 well, and two samples were from well Y-7 (depths of 24 cm and 122 cm). These two wells, at Black Sand and Biscuit Basins, respectively, were drilled in 1967 as part of a scientific drilling program by the U.S. Geological Survey (White et al., 1975). Even with samples as small as 15 g, we obtained sufficient carbonaceous material (a mixture of thermophilic mats, pollen, and charcoal) for the 14C analyses. Apparent time of deposition ranged from 3775 ± 25 and 2910 ± 30 14C years BP at the top of the cores to about 8000 years BP at the bottom. The dates are consistent with variable rates of sinter formation at individual sites within the UGB over the Holocene. On a basin-wide scale, though, these and other existing 14C dates hint that hydrothermal activity at the UGB may have been continuous throughout the Holocene.

Variations in barrier-island evolution at millennial and decadal time scales related to underlying geology, Onslow Beach, NC USA

NASA Astrophysics Data System (ADS)

Yu, W.; Hood, D.; Browne, R.; Rodriguez, A. B.

2010-12-01

Located midway between Cape Fear and Cape Lookout, North Carolina, Onslow Beach is a 12 km-long barrier island, which historically had transgressive and stable profiles on the southern and northern ends, respectively. The northern half of the island has well-developed dunes in front of maritime forest. The southern half is low-lying and is characterized by washover fans infringing on salt marsh. By studying the underlying barrier lithology and structure, we will determine the evolution of the island at millennial time scales and in turn address whether the along-beach variations in barrier morphology and the historical shoreline-movement trends are related to the underlying geology. We collected 33 vibracores along 7 cross-shore transects spaced equally along Onslow Beach. Variations in topography were measured along these transects using an RTK-GPS. Cores collected from southern transects revealed multiple marsh-overwash sequences overlying estuarine deposits or a highly compacted unit typically composed of gray clay or brown medium to fine grained sand, possibly of Pleistocene age. The contact between this Pleistocene unit and the overlying estuarine deposits or thin peat layer represents the initial inundation of the area in response to Holocene sea-level rise. The elevation of this contact decreases towards the north along the island to a point where our coring methods could not penetrate deep enough to sample it (>4.0 m below the surface). In addition, marsh deposits sampled in the north below the island, which range from 30-120cm, were commonly found to be thicker than the marsh deposits sampled in the south, which range from 10-30 cm. These thick back-barrier units in the north preserve paleo overwash events as fining-upward sequences and likely accreted and were preserved due to the large accommodation space that the deep Pleistocene surface provided. The stratigraphy of the northern cores indicates a less stable Island in the past dominated by overwash. These thick sandy overwash sediments could have served as a localized source for sand that contributed to this part of the barrier becoming more stable than the southern part of the barrier as the rate of sea-level rise decreased. The cores from the highly erosive southern end of the island suggest a persistent unstable island continually dominated by overwash processes and a transgressing shoreline. These data suggests that the Pleistocene surface had a great influence on the transgressive history and contrasting morphologies on either ends of the island. Carbon dating of the Pleistocene and marsh units in future research will constrain when the island formed and the rate of change in depositional environments.

A remediation performance model for enhanced metabolic reductive dechlorination of chloroethenes in fractured clay till

NASA Astrophysics Data System (ADS)

Manoli, Gabriele; Chambon, Julie C.; Bjerg, Poul L.; Scheutz, Charlotte; Binning, Philip J.; Broholm, Mette M.

2012-04-01

A numerical model of metabolic reductive dechlorination is used to describe the performance of enhanced bioremediation in fractured clay till. The model is developed to simulate field observations of a full scale bioremediation scheme in a fractured clay till and thereby to assess remediation efficiency and timeframe. A relatively simple approach is used to link the fermentation of the electron donor soybean oil to the sequential dechlorination of trichloroethene (TCE) while considering redox conditions and the heterogeneous clay till system (clay till matrix, fractures and sand stringers). The model is tested on lab batch experiments and applied to describe sediment core samples from a TCE-contaminated site. Model simulations compare favorably to field observations and demonstrate that dechlorination may be limited to narrow bioactive zones in the clay matrix around fractures and sand stringers. Field scale simulations show that the injected donor is expected to be depleted after 5 years, and that without donor re-injection contaminant rebound will occur in the high permeability zones and the mass removal will stall at 18%. Long remediation timeframes, if dechlorination is limited to narrow bioactive zones, and the need for additional donor injections to maintain dechlorination activity may limit the efficiency of ERD in low-permeability media. Future work should address the dynamics of the bioactive zones, which is essential to understand for predictions of long term mass removal.

Subsurface structures and properties of a medium-scale peatland area by means of hydrogeophysical methods

NASA Astrophysics Data System (ADS)

Altdorff, Daniel; van der Kruk, Jan; Bechtold, Michel; Tiemeyer, Bärbel; Huismann, Sander

2013-04-01

Intact peatlands are natural sinks of climate-relevant atmospheric CO2 and they are able to store high amounts of organic carbon (C). In addition, intact peatlands are increasingly important given positive effects on biodiversity, hydrological processes and corresponding management issues. Nevertheless, large parts of peatlands in populated areas were modified by human activity during the last centuries. In Germany, more than 90% of the peatlands are drained, mainly for agricultural use. Due to the recent recognition of the positive effects of intact peatlands, there are presently several initiatives for re-wetting parts of these peatlands. However, a restoration to nearly natural conditions needs an evaluation of the current situation as well as an assessment of the restoration potential. Therefore, soil properties like peat layer thickness, bulk density and moisture content need to be known. Non-invasive hydrogeophysical methods offer the possibility for a time and cost-effective characterization of peatlands. In this study, we investigated a medium-scale peatland area (approximately 35 ha) of the 3000 ha large 'Großes Moor' peatland. We present apparent conductivity (ECa) values obtained from Electromagnetic Induction (EMI) measurements representative for three investigation depths (approximately 0.25, 0.5, and 1m). We selected zones with dissimilar ECa to identify areas where strong changes in the subsoil properties with depth are expected (i.e. shallow peat soil on top of sand). Within these areas, additional measurements were made using Ground Penetration Radar (GPR) and soil sampling was performed. In total, six 30 m long GPR profiles and corresponding common midpoint (CMP) measurements were recorded. Additionally, 15 soil cores were taken down to a depth of 0.9 m in order to obtain peat thickness, water content, pore water EC, bulk density (BD), as well as C and N content. Each core was divided into several 5 to 20 cm thick layers to obtain information on the vertical variation of these soil properties with depth. Our results indicate that the peat layer is generally characterized by lower BD, higher pore water EC, higher C content, and higher water contents compared to the underlying sand layer. Preliminary EMI results indicate a ECa - C content correlation that decreases with EMI investigation depth from 0.25 to 1 m. Regarding all soil core properties, the strongest contrast occurs at the peat-sand interface. This contrast also clearly appears in some of the GPR results. The EMI apparent conductivities are positively correlated with soil water content and peat thickness obtained from the soil cores. Preliminary GPR results confirm an increased thickness of the upper layer in areas with increased ECa values. The EMI results also reveal clear patterns linked over several fields with different land use history that represent natural structures in the subsurface.

Lake Qinghai Drilling Project: Evolution History of Lake Qinghai and East Asian Monsoon Changes since the Late Miocene

NASA Astrophysics Data System (ADS)

An, Z.; Colman, S.

2007-12-01

As a closed continental lake on the north-east margin of the Tibetan Plateau, Lake Qinghai is sensitive to climate variations as well as the environmental effects of Plateau growth/uplift. Supported by Chinese funding agencies and ICDP, onshore and offshore lake cores were drilled in 2005. We compare our preliminary chronostratigraphic, sedimentologic, and geochemical results with climatic records from the Loess Plateau, South China Sea, Arctic and global oceans, and we discuss the evolution of Lake Qinghai at different time scales since the late Miocene. Lake Qinghai is shown to have intimate linkages with the warm/moist East Asian summer monsoon, the cold/dry East Asian winter monsoon, and the growth/uplift of the Tibetan Plateau. Magnetostratigraphic studies of the onshore drill cores indicate that thick greenish clays were deposited during Late Miocene, suggesting the initial formation of the Qinghai Lake basin. Consistent with proxies from the Loess Plateau and the South China Sea, they imply summer-monsoon strengthening and inland intrusion. These changes may be related to a growth event of the Tibetan Plateau at 10-8 Ma, which led to the uplift of Qinghai Nanshan, formation of faulted lake basins, and enhanced summer monsoon circulation. From 6 to 4.6Ma eolian red clays in the core indicate lake basin dessication, as Loess Plateau dust flux increased with the strengthening of the winter monsoon and coincident with intense Arctic ice rafting at 6-5 Ma. From 4.6 to 3.5 Ma thick greenish clays were deposited as modern Lake Qinghai formed. Significantly increased fluxes of TOC, C/N and total sediment might be related to uplift of Qinghai Nanshan and basin subsidence at that time, and they are coeval with the increasing strength of East Asian monsoon during early Pliocene. At 3.5-2.6 Ma, continued strengthening of the East Asian summer monsoon, inland aridification, and increases in global ice volume suggest another growth event of the Tibetan Plateau. Shallow-water silty clays were deposited in the lake basin at this time. Since 2.6 Ma, deposition in the basin was characterized by shallow-water silty clays, intercalated with layers of loess- like material, eolian sand, gravel, and sand, indicating multiple lake expansion/dessication cycles, presumably at orbital frequencies, reflecting multiple migrations of the East Asian summer monsoon front driven by solar radiation and global ice volume changes over this region. Several previous studies of cores as much as 7m long from the depositional basins of Lake Qinghai have documented monsoon climate and environmental changes at the lake from the deglacial period through the Holocene, which are generally consistent with northern Hemisphere summer insolation and its seasonality changes. A wide variety of proxies have been used, and some cores have been studied at very high temporal resolution, especially for the last several hundred years. Results suggest that solar activity influences decadal regional temperatures, and that it is the East Asian summer monsoon as opposed to the Indian summer monsoon that acts as the dominate moisture source at the decadal scale within the local region. Offshore GLAD800 drill cores obtained in 2005 sampled fine-grained sediments before encountering thick units of sand. The fine-grained sections are 2-3 times longer than previous cores from similar sites. Paleolimnological proxy studies are underway on these cores to extend the young part of the paleoenvironmental record back to significantly before the last glacial maximum.

Understanding Phlebotomus perniciosus abundance in south-east Spain: assessing the role of environmental and anthropic factors.

PubMed

Risueño, José; Muñoz, Clara; Pérez-Cutillas, Pedro; Goyena, Elena; Gonzálvez, Moisés; Ortuño, María; Bernal, Luis Jesús; Ortiz, Juana; Alten, Bulent; Berriatua, Eduardo

2017-04-19

Leishmaniosis is associated with Phlebotomus sand fly vector density, but our knowledge of the environmental framework that regulates highly overdispersed vector abundance distributions is limited. We used a standardized sampling procedure in the bioclimatically diverse Murcia Region in Spain and multilevel regression models for count data to estimate P. perniciosus abundance in relation to environmental and anthropic factors. Twenty-five dog and sheep premises were sampled for sand flies using adhesive and light-attraction traps, from late May to early October 2015. Temperature, relative humidity and other animal- and premise-related data recorded on site and other environmental data were extracted from digital databases using a geographical information system. The relationship between sand fly abundance and explanatory variables was analysed using binomial regression models. The total number of sand flies captured, mostly with light-attraction traps, was 3,644 specimens, including 80% P. perniciosus, the main L. infantum vector in Spain. Abundance varied between and within zones and was positively associated with increasing altitude from 0 to 900 m above sea level, except from 500 to 700 m where it was low. Populations peaked in July and especially during a 3-day heat wave when relative humidity and wind speed plummeted. Regression models indicated that climate and not land use or soil characteristics have the greatest impact on this species density on a large geographical scale. In contrast, micro-environmental factors such as animal building characteristics and husbandry practices affect sand fly population size on a smaller scale. A standardised sampling procedure and statistical analysis for highly overdispersed distributions allow reliable estimation of P. perniciosus abundance and identification of environmental drivers. While climatic variables have the greatest impact at macro-environmental scale, anthropic factors may be determinant at a micro-geographical scale. These finding may be used to elaborate predictive distribution maps useful for vector and pathogen control programs.

A New Critical State Model for Geomechanical Behavior of Methane Hydrate-Bearing Sands

NASA Astrophysics Data System (ADS)

Lin, J. S.; Xing, P.; Rutqvist, J.; Seol, Y.; Choi, J. H.

2014-12-01

Methane hydrate bearing sands behave like sands once the hydrate has dissociated, but could exhibit a substantial increase in the shear strength, stiffness and dilatancy as the degree of hydrate saturation increases. A new critical state model was developed that incorporates the spatially mobilized plane (SMP) concept, which has been proven effective in modeling mechanical behavior of sands. While this new model was built on the basic constructs of the critical state model, important enhancements were introduced. The model adopted the t-stress concept, which defined the normal and shear stress on the SMP, in describing the plastic behavior of the soil. In this connection the versatile Matsuoka-Nakai yield criterion was also employed, which defined the general three dimensional yield behavior. The resulting constitutive law was associated in the t-stress space, but became non-associated in the conventional p-q stress space as it should be for sands. The model also introduced a generalized degree of hydrate saturation concept that was modified from the pioneering work of the Cambridge group. The model gives stress change when the sands are subjected to straining, and/or to hydrate saturation changes. The performance of the model has been found satisfactory using data from laboratory triaxial tests on reconstituted samples and core samples taken from Nankai Trough, Japan. The model has been implemented into FLAC3D. A coupling example with the multiphase flow code, TOUGH+, is presented which simulates the mechanical behavior of a sample when the surrounding temperature has been raised, and the hydrate undergoes state change and no longer resides in the stability zone.

Groundwater Remediation and Alternate Energy at White Sands Test Facility

NASA Technical Reports Server (NTRS)

Fischer, Holger

2008-01-01

White Sands Test Facility Core Capabilities: a) Remote Hazardous Testing of Reactive, Explosive, and Toxic Materials and Fluids; b) Hypergolic Fluids Materials and Systems Testing; c) Oxygen Materials and System Testing; d) Hypervelocity Impact Testing; e)Flight Hardware Processing; and e) Propulsion Testing. There is no impact to any drinking water well. Includes public wells and the NASA supply well. There is no public exposure. Groundwater is several hundred feet below ground. No air or surface water exposure. Plume is moving very slowly to the west. Plume Front Treatment system will stop this westward movement. NASA performs on-going monitoring. More than 200 wells and zones are routinely sampled. Approx. 850 samples are obtained monthly and analyzed for over 300 different hazardous chemicals.

Hardness characteristic of dental porcelain synthesized from Indonesian natural sand

NASA Astrophysics Data System (ADS)

Gunawan, J.; Taufik, D.; Takarini, V.; Hasratiningsih, Z.; Ramelan, A.

2018-02-01

Porcelain has been one of dental biomaterials which can be used to restore tooth structure. Veneer and jacket crown were the examples of dental porcelain restoration. Since wear resistance is related to the strength on its surface, then Vickers Hardness Test of the synthesized porcelain was applied subsequently. If the porcelain hardness number is too high, it should be considered that an abrasion of the opposing teeth could occur. On previous research, dental porcelain had been successfully synthesized from Indonesian natural sand. In this experiment, 5 samples were prepared from a mixture of 65w/o Pangaribuan feldspar, 25w/o Belitung silica, 5w/o Sukabumi kaolinite, and 5w/o potassium salt. This synthesized porcelain samples were invested on 5 cm diameter resin each. A kilogram of load was placed on top of each sample for 10 seconds on 7 different indented areas using ZwickRoell Indentec ZHVμ Micro Vickers. The average hardness number of synthesized dental porcelain made from Indonesian natural sand was 936.06 VHN which was higher than the average hardness number of porcelain restoration. In conclusion of the hardness test, synthesized dental porcelain made from Indonesian natural sand can potentially be used as a core, which shall support hardness and strength of the crown restoration.

Allogenic and Autogenic Signals in the Detrital Zircon U-Pb Record of the Deep-Sea Bengal Fan

NASA Astrophysics Data System (ADS)

Blum, M. D.; Rogers, K. G.; Gleason, J. D.; Najman, Y.

2017-12-01

The Himalayan-sourced Ganges-Brahmaputra river system and the deep-sea Bengal Fan represent Earth's largest sediment-dispersal system. This presentation summarizes a new detrital zircon U-Pb (DZ) provenance record from the Bengal Fan from cores collected during IODP Expedition 354, with coring sites located 1350 km downdip from the shelf margin. Each of our 15 samples were collected from medium- to fine-grained turbidite sand and, based on shipboard biostratigraphic analyses, our samples are late Miocene to late Pleistocene in age. Each sample was analyzed by LA-ICPMS at the Arizona Laserchron facility, with an average of n=270 concordant U-Pb ages per sample. Our goals are to use these data to evaluate the influence of allogenic controls vs. autogenic processes on signal propagation from source-to-sink. At the first order, large-scale sediment transfer to the Bengal Fan clearly records the strong tectonic and climatic forcing associated with the Himalayas and Ganges-Brahmaputra system: after up to 2500 km of river transport, and 1350 km of transport in turbidity currents, the DZ record faithfully represents Himalayan source terrains. The sand-rich turbidite part of the record is nevertheless biased towards glacial periods when rivers extended across the shelf in response to climate-forced sea-level fall, and discharged directly to slope canyons. However, only part of the Bengal Fan DZ record represents either the Ganges or the Brahmaputra, with most samples representing varying degrees of mixing of sediments from the two systems: this mixing, or the lack thereof, represents the signal of autogenic avulsions on the delta plain that result in the two river systems delivering sediment separately to the shelf margin, or together as they do today. Within the allogenic framework established by tectonic processes, the climatic system, and global climate-forced sea-level change, the DZ U-Pb record of sediment mixing or the lack thereof provides a fingerprint of autogenic avulsions on signal transfer from source-to-sink in the world's largest sediment-dispersal system.

Suitability of river delta sediment as proppant, Missouri and Niobrara Rivers, Nebraska and South Dakota, 2015

USGS Publications Warehouse

Zelt, Ronald B.; Hobza, Christopher M.; Burton, Bethany L.; Schaepe, Nathaniel J.; Piatak, Nadine

2017-11-16

Sediment management is a challenge faced by reservoir managers who have several potential options, including dredging, for mitigation of storage capacity lost to sedimentation. As sediment is removed from reservoir storage, potential use of the sediment for socioeconomic or ecological benefit could potentially defray some costs of its removal. Rivers that transport a sandy sediment load will deposit the sand load along a reservoir-headwaters reach where the current of the river slackens progressively as its bed approaches and then descends below the reservoir water level. Given a rare combination of factors, a reservoir deposit of alluvial sand has potential to be suitable for use as proppant for hydraulic fracturing in unconventional oil and gas development. In 2015, the U.S. Geological Survey began a program of researching potential sources of proppant sand from reservoirs, with an initial focus on the Missouri River subbasins that receive sand loads from the Nebraska Sand Hills. This report documents the methods and results of assessments of the suitability of river delta sediment as proppant for a pilot study area in the delta headwaters of Lewis and Clark Lake, Nebraska and South Dakota. Results from surface-geophysical surveys of electrical resistivity guided borings to collect 3.7-meter long cores at 25 sites on delta sandbars using the direct-push method to recover duplicate, 3.8-centimeter-diameter cores in April 2015. In addition, the U.S. Geological Survey collected samples of upstream sand sources in the lower Niobrara River valley.At the laboratory, samples were dried, weighed, washed, dried, and weighed again. Exploratory analysis of natural sand for determining its suitability as a proppant involved application of a modified subset of the standard protocols known as American Petroleum Institute (API) Recommended Practice (RP) 19C. The RP19C methods were not intended for exploration-stage evaluation of raw materials. Results for the washed samples are not directly applicable to evaluations of suitability for use as fracture sand because, except for particle-size distribution, the API-recommended practices for assessing proppant properties (sphericity, roundness, bulk density, and crush resistance) require testing of specific proppant size classes. An optical imaging particle-size analyzer was used to make measurements of particle-size distribution and particle shape. Measured samples were sieved to separate the dominant-size fraction, and the separated subsample was further tested for roundness, sphericity, bulk density, and crush resistance.For the bulk washed samples collected from the Missouri River delta, the geometric mean size averaged 0.27 millimeters (mm), 80 percent of the samples were predominantly sand in the API 40/70 size class, and 17 percent were predominantly sand in the API 70/140 size class. Distributions of geometric mean size among the four sandbar complexes were similar, but samples collected from sandbar complex B were slightly coarser sand than those from the other three complexes. The average geometric mean sizes among the four sandbar complexes ranged only from 0.26 to 0.30 mm. For 22 main-stem sampling locations along the lower Niobrara River, geometric mean size averaged 0.26 mm, an average of 61 percent was sand in the API 40/70 size class, and 28 percent was sand in the API 70/140 size class. Average composition for lower Niobrara River samples was 48 percent medium sand, 37 percent fine sand, and about 7 percent each very fine sand and coarse sand fractions. On average, samples were moderately well sorted.Particle shape and strength were assessed for the dominant-size class of each sample. For proppant strength, crush resistance was tested at a predetermined level of stress (34.5 megapascals [MPa], or 5,000 pounds-force per square inch). To meet the API minimum requirement for proppant, after the crush test not more than 10 percent of the tested sample should be finer than the precrush dominant-size class. For particle shape, all samples surpassed the recommended minimum criteria for sphericity and roundness, with most samples being well-rounded. For proppant strength, of 57 crush-resistance tested Missouri River delta samples of 40/70-sized sand, 23 (40 percent) were interpreted as meeting the minimum criterion at 34.5 MPa, or 5,000 pounds-force per square inch. Of 12 tested samples of 70/140-sized sand, 9 (75 percent) of the Missouri River delta samples had less than 10 percent fines by volume following crush testing, achieving the minimum criterion at 34.5 MPa. Crush resistance for delta samples was strongest at sandbar complex A, where 67 percent of tested samples met the 10-percent fines criterion at the 34.5-MPa threshold. This frequency was higher than was indicated by samples from sandbar complexes B, C, and D that had rates of 50, 46, and 42 percent, respectively. The group of sandbar complex A samples also contained the largest percentages of samples dominated by the API 70/140 size class, which overall had a higher percentage of samples meeting the minimum criterion compared to samples dominated by coarser size classes; however, samples from sandbar complex A that had the API 40/70 size class tested also had a higher rate for meeting the minimum criterion (57 percent) than did samples from sandbar complexes B, C, and D (50, 43, and 40 percent, respectively). For samples collected along the lower Niobrara River, of the 25 tested samples of 40/70-sized sand, 9 samples passed the API minimum criterion at 34.5 MPa, but only 3 samples passed the more-stringent criterion of 8 percent postcrush fines. All four tested samples of 70/140 sand passed the minimum criterion at 34.5 MPa, with postcrush fines percentage of at most 4.1 percent.For two reaches of the lower Niobrara River, where hydraulic sorting was energized artificially by the hydraulic head drop at and immediately downstream from Spencer Dam, suitability of channel deposits for potential use as fracture sand was confirmed by test results. All reach A washed samples were well-rounded and had sphericity scores above 0.65, and samples for 80 percent of sampled locations met the crush-resistance criterion at the 34.5-MPa stress level. A conservative lower-bound estimate of sand volume in the reach A deposits was about 86,000 cubic meters. All reach B samples were well-rounded but sphericity averaged 0.63, a little less than the average for upstream reaches A and SP. All four samples tested passed the crush-resistance test at 34.5 MPa. Of three reach B sandbars, two had no more than 3 percent fines after the crush test, surpassing more stringent criteria for crush resistance that accept a maximum of 6 percent fines following the crush test for the API 70/140 size class.Relative to the crush-resistance test results for the API 40/70 size fraction of two samples of mine output from Loup River settling-basin dredge spoils near Genoa, Nebr., four of five reach A sample locations compared favorably. The four samples had increases in fines composition of 1.6–5.9 percentage points, whereas fines in the two mine-output samples increased by an average 6.8 percentage points.

Coarse-sediment bands on the inner shelf of southern Monterey Bay, California

USGS Publications Warehouse

Hunter, R.E.; Dingler, J.R.; Anima, R.J.; Richmond, B.M.

1988-01-01

Bands of coarse sand that trend parallel to the shore, unlike the approximately shore-normal bands found in many inner shelf areas, occur in southern Monterey Bay at water depths of 10-20 m, less than 1 km from the shore. The bands are 20-100 m wide and alternate with bands of fine sand that are of similar width. The coarse-sand bands are as much as 1 m lower than the adjacent fine-sand bands, which have margins inclined at angles of about 20??. The mean grain sizes of the coarse and fine sand are in the range of 0.354-1.0 mm and 0.125-0.354 mm, respectively. Wave ripples that average about 1 m in spacing always occur in the coarse-sand bands. Over a period of 3 yrs, the individual bands moved irregularly and changed in shape, as demonstrated by repeated sidescan sonar surveys and by the monitoring of rods jetted into the sea floor. However, the overall pattern and distribution of the bands remained essentially unchanged. Cores, 0.5-1.0 m long, taken in coarse-sand bands contain 0.2-0.5 m of coarse sand overlying fine sand or interbedded fine and coarse sand. Cores from fine-sand bands have at least one thin coarse sand layer at about the depth of the adjacent coarse-sand band. None of the cores revealed a thick deposit of coarse sand. The shore-parallel bands are of unknown origin. Their origin is especially puzzling because approximately shore-normal bands are present in parts of the study area and immediately to the north. ?? 1988.

Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod.

PubMed

Schwing, Patrick T; Romero, Isabel C; Larson, Rebekka A; O'Malley, Bryan J; Fridrik, Erika E; Goddard, Ethan A; Brooks, Gregg R; Hastings, David W; Rosenheim, Brad E; Hollander, David J; Grant, Guy; Mulhollan, Jim

2016-08-17

Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, this resolution provides records at the annual to decadal scale, at best. An extrusion method, using a calibrated, threaded-rod is presented here, which allows for millimeter-scale subsampling of aquatic sediment cores of varying diameters. Millimeter scale subsampling allows for sub-annual to monthly analysis of the sedimentary record, an order of magnitude higher than typical sampling schemes. The extruder consists of a 2 m aluminum frame and base, two core tube clamps, a threaded-rod, and a 1 m piston. The sediment core is placed above the piston and clamped to the frame. An acrylic sampling collar is affixed to the upper 5 cm of the core tube and provides a platform from which to extract sub-samples. The piston is rotated around the threaded-rod at calibrated intervals and gently pushes the sediment out the top of the core tube. The sediment is then isolated into the sampling collar and placed into an appropriate sampling vessel (e.g., jar or bag). This method also preserves the unconsolidated samples (i.e., high pore water content) at the surface, providing a consistent sampling volume. This mm scale extrusion method was applied to cores collected in the northern Gulf of Mexico following the Deepwater Horizon submarine oil release. Evidence suggests that it is necessary to sample at the mm scale to fully characterize events that occur on the monthly time-scale for continental slope sediments.

Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod

PubMed Central

Schwing, Patrick T.; Romero, Isabel C.; Larson, Rebekka A.; O'Malley, Bryan J.; Fridrik, Erika E.; Goddard, Ethan A.; Brooks, Gregg R.; Hastings, David W.; Rosenheim, Brad E.; Hollander, David J.; Grant, Guy; Mulhollan, Jim

2016-01-01

Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, this resolution provides records at the annual to decadal scale, at best. An extrusion method, using a calibrated, threaded-rod is presented here, which allows for millimeter-scale subsampling of aquatic sediment cores of varying diameters. Millimeter scale subsampling allows for sub-annual to monthly analysis of the sedimentary record, an order of magnitude higher than typical sampling schemes. The extruder consists of a 2 m aluminum frame and base, two core tube clamps, a threaded-rod, and a 1 m piston. The sediment core is placed above the piston and clamped to the frame. An acrylic sampling collar is affixed to the upper 5 cm of the core tube and provides a platform from which to extract sub-samples. The piston is rotated around the threaded-rod at calibrated intervals and gently pushes the sediment out the top of the core tube. The sediment is then isolated into the sampling collar and placed into an appropriate sampling vessel (e.g., jar or bag). This method also preserves the unconsolidated samples (i.e., high pore water content) at the surface, providing a consistent sampling volume. This mm scale extrusion method was applied to cores collected in the northern Gulf of Mexico following the Deepwater Horizon submarine oil release. Evidence suggests that it is necessary to sample at the mm scale to fully characterize events that occur on the monthly time-scale for continental slope sediments. PMID:27585268

The Importance of Actualistic Source-to-Sink Sand Provenance Studies in Illuminating the Nature of Ancient Fluvial Systems From the Deep-Marine Clastic Successions They Sourced

NASA Astrophysics Data System (ADS)

Marsaglia, K. M.; Parra, J. G.; Dawson, S.

2006-12-01

Successions of gravity-flow deposits in deep-marine fan systems have the potential to record the evolution of their fluvial source region as well as specific tectonic, climatic, eustatic and anthropogenic events. Deciphering these signals involves the description and quantification of key sediment attributes such as fan volume, the rate of sediment accumulation, the frequency of depositional events, sediment texture, and sediment composition. Sediment composition/provenance provides insight into the nature of the fluvial source, including drainage basin geology and drainage development. For example, Marsaglia et al. (1995) demonstrated a connection between source river lengthening owing to eustatic change and sand composition in Quaternary turbidite successions of the Santa Barbara Basin at Ocean Drilling Program (ODP) Site 893. In contrast, longer-term compositional trends recognized in the Mesozoic to Cenozoic rift-to-drift successions cored by various ODP legs on the North Atlantic margins are more likely associated with continental margin drainage development and fluvial system evolution (Marsaglia et al., in press). These two connections between sink and source were made possible by well-documented petrologic data sets for both modern onshore fluvial systems and older offshore deep-marine successions, but in each case different workers collected the onshore and offshore data sets. In the Waipaoa River Sedimentary System of North Island, New Zealand we have taken a different, more holistic approach, with a limited and linked group of researchers and sample data base covering the complete system. The study area is an active forearc margin characterized by uplifted and deformed sedimentary successions and periodic input of arc-derived ash. Recently, the modern onshore system has been thoroughly documented via studies of the petrology of outcropping Mesozoic to Cenozoic units, fluvial terrace deposits, and modern fluvial sediments (e.g., James et al., in press). Now we are building on that data set and moving from source-to-sink to trace sandy sediment through the system out onto the shelf and slope where it has been encountered in shallow cores. Lessons learned onshore, such as a distinct compositional dependence on grain size and the relationships of bedrock geology to certain sand grain types, also apply to these offshore core samples. Many of the sandy intervals are largely composed of reworked tephra from Taupo eruptions, whereas quartz and feldspar dominate finer sand samples. Lithic-dominated sands are less common and coarser grained. Isolated greywacke gravel clasts indicate that at some point coarse sediment "leaked" into the basin from the south. The volumetric importance of this extrabasinal input can be assessed by looking at the types and proportions of lithic fragments within the finer sand fraction.

The Pliocene Lost River found to west: Detrital zircon evidence of drainage disruption along a subsiding hotspot track

USGS Publications Warehouse

Hodges, M.K.V.; Link, P.K.; Fanning, C.M.

2009-01-01

SHRIMP analysis of U/Pb ages of detrital zircons in twelve late Miocene to Pleistocene sand samples from six drill cores on the Snake River Plain (SRP), Idaho, suggests that an ancestral Lost River system was drained westward along the northern side of the SRP. Neoproterozoic (650 to 740??Ma, Cryogenian) detrital zircon grains from the Wildhorse Creek drainage of the Pioneer Mountains core complex, with a source in 695??Ma orthogneiss, and which are characteristic of the Big Lost River system, are found in Pliocene sand from cores drilled in the central SRP (near Wendell) and western SRP (at Mountain Home). In addition to these Neoproterozoic grains, fluvial sands sourced from the northern margin of the SRP contain detrital zircons with the following ages: 42 to 52??Ma from the Challis magmatic belt, 80 to 100??Ma from the Atlanta lobe of the Idaho batholith, and mixed Paleozoic and Proterozoic ages (1400 to 2000??Ma). In contrast, sands in the Mountain Home Air Base well (MHAB) that contain 155-Ma Jurassic detrital grains with a source in northern Nevada are interpreted to represent an integrated Snake River, with provenance on the southern, eastern and northern sides of the SRP. We propose that late Pliocene and early Pleistocene construction of basaltic volcanoes and rhyolitic domes of the Axial Volcanic Zone of the eastern SRP and the northwest-trending Arco Volcanic Rift Zone (including the Craters of the Moon volcanic center), disrupted the paleo-Lost River drainage, confining it to the Big Lost Trough, a volcanically dammed basin of internal drainage on the Idaho National Laboratory (INL). After the Axial Volcanic Zone and Arco Volcanic Rift Zone were constructed to form a volcanic eruptive and intrusive highland to the southwest, sediment from the Big Lost River was trapped in the Big Lost Trough instead of being delivered by surface streams to the western SRP. Today, water from drainages north of the SRP enters the Snake River Plain regional aquifer through sinks in the Big Lost Trough, and the water resurfaces at Thousand Springs, Idaho, about 195??km to the southwest. Holocene to latest Pliocene samples from drill core in the Big Lost Trough reveal interplay between the glacio-fluvial outwash of the voluminous Big Lost River system and the relatively minor Little Lost River system. A mixed provenance signature is recognized in fine-grained sands deposited in a highstand of a Pleistocene pluvial-lake system. ?? 2009 Elsevier B.V.

Localized enrichment of polycyclic aromatic hydrocarbons in soil, spruce needles, and lake sediments linked to in-situ bitumen extraction near Cold Lake, Alberta.

PubMed

Korosi, J B; Irvine, G; Skierszkan, E K; Doyle, J R; Kimpe, L E; Janvier, J; Blais, J M

2013-11-01

The extraction of bitumen from the Alberta oil sands using in-situ technologies is expanding at a rapid rate; however, investigations into the environmental impacts of oil sands development have focused on surface mining in the Athabasca region. We measured polycyclic aromatic hydrocarbons (PAH) in soils, spruce needles, and lake sediment cores in the Cold Lake oil sands region to provide a historical and spatial perspective on PAH contamination related to in-situ extraction activities. A pronounced increase in PAH concentrations was recorded in one of two study lakes (Hilda Lake) corresponding to the onset of commercial bitumen production in ~1985. Distance from extraction rigs was not an important predictor of PAH concentrations in soils, although two samples located near installations were elevated in alkyl PAHs. Evidence of localized PAH contamination in Hilda Lake and two soil samples suggests that continued environmental monitoring is justified to assess PAH contamination as development intensifies. Copyright © 2013 Elsevier Ltd. All rights reserved.

System Controls on the South Texas Sand Sheet

NASA Astrophysics Data System (ADS)

Barrineau, Clifton Patrick

Semi-stabilized dune systems are important indicators of Quaternary drought variability across central North America. The South Texas sand sheet (STSS) is the southernmost relict dune system in central North America and is exposed to higher evapotranspiration and moisture variability than similar landscapes farther north. This study uses multi-scale analysis of LiDAR data, geophysical surveys, optically stimulated luminescence dates of core samples, and X-ray fluorescence analysis to identify historical periods of desertification across the STSS. These data suggest long-term relationships between climate, ecological disturbances, geological framework, and desertification. Aeolian activations dated at ca. 75, 230, 2000, 4100, and 6600 yr bp correspond to periods of persistent regional drought, changes in sediment supply, and anthropogenic disturbances of native ecology. From these results it appears that regionalized activation in semi-stabilized dune systems is controlled primarily by climatic variations that reduce the overall moisture available for maintaining vigorous vegetation growth, while localized activation patterns depend more on stresses related to site-specific morphodynamics as well as human activity. With enhanced aridity forecast for much of central North America through the 21 st century, understanding the specific thresholds of desertification is an important step towards building a conceptual model of desertification in semi-stabilized dune landscapes.

Linking morphodynamic response with sediment mass balance on the Colorado River in Marble Canyon: issues of scale, geomorphic setting, and sampling design

USGS Publications Warehouse

Grams, Paul E.; Topping, David J.; Schmidt, John C.; Hazel, Joseph E.; Kaplinski, Matt

2013-01-01

Measurements of morphologic change are often used to infer sediment mass balance. Such measurements may, however, result in gross errors when morphologic changes over short reaches are extrapolated to predict changes in sediment mass balance for long river segments. This issue is investigated by examination of morphologic change and sediment influx and efflux for a 100 km segment of the Colorado River in Grand Canyon, Arizona. For each of four monitoring intervals within a 7 year study period, the direction of sand-storage response within short morphologic monitoring reaches was consistent with the flux-based sand mass balance. Both budgeting methods indicate that sand storage was stable or increased during the 7 year period. Extrapolation of the morphologic measurements outside the monitoring reaches does not, however, provide a reasonable estimate of the magnitude of sand-storage change for the 100 km study area. Extrapolation results in large errors, because there is large local variation in site behavior driven by interactions between the flow and local bed topography. During the same flow regime and reach-average sediment supply, some locations accumulate sand while others evacuate sand. The interaction of local hydraulics with local channel geometry exerts more control on local morphodynamic response than sand supply over an encompassing river segment. Changes in the upstream supply of sand modify bed responses but typically do not completely offset the effect of local hydraulics. Thus, accurate sediment budgets for long river segments inferred from reach-scale morphologic measurements must incorporate the effect of local hydraulics in a sampling design or avoid extrapolation altogether.

Alexandria's Eastern Harbor, Egypt: Pollen, microscopic charcoal, and the transition from natural to human-modified basin

USGS Publications Warehouse

Stanley, J.-D.; Bernhardt, C.E.

2010-01-01

Pollen and microscopic charcoal examined in Holocene sediment core samples record major environmental modifications affecting Alexandria's Eastern Harbor through time. We assess whether such changes on Egypt's coastal margin were influenced primarily by natural, or natural plus human, or primarily human factors. We focus on (1) the times when pollen assemblages and microscopic charcoal content changed in the core, (2) how they changed, and (3) why this occurred. The analysis takes into account the core's stratigraphy, regional climate variability, human history, and local archaeological record. Four pollenmicroscopic charcoal zones are identified. The earliest change occurred at ca. 6000 YBP, during Egypt's earlier Predynastic (Neolithic) period, coinciding with a lithologic break from sand to muddy sand. Pollen during this time indicates a transition to a much drier climate rather than effects of human activity. The second change in pollen occurred 3600-2900 YBP, during a period of continued aridity with no lithologic variation in this core interval. Pollen (cereal taxa, agricultural weeds, grape) and a sharp increase in microscopic charcoal indicate that human activity became prevalent at least 700 y before Alexander the Great's arrival in this region, and these results highlight the transition from a largely natural climatecontrolled environment to one influenced by both climate and anthropogenic activity. The third shift up-core in pollen assemblages is dated at ca. 2300 YBP, at the boundary between a sand and mud unit. It coincides with construction by the Ptolemies of the Heptastadion between Alexandria and Pharos Island. From this time onward, harbor sediment in the nearly enclosed catchment basin indicates a near-continuous record of dominant proximal human activity. ?? 2010 Coastal Education and Research Foundation.

Scientific results of the Second Gas Hydrate Drilling Expedition in the Ulleung Basin (UBGH2)

USGS Publications Warehouse

Ryu, Byong-Jae; Collett, Timothy S.; Riedel, Michael; Kim, Gil-Young; Chun, Jong-Hwa; Bahk, Jang-Jun; Lee, Joo Yong; Kim, Ji-Hoon; Yoo, Dong-Geun

2013-01-01

As a part of Korean National Gas Hydrate Program, the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) was conducted from 9 July to 30 September, 2010 in the Ulleung Basin, East Sea, offshore Korea using the D/V Fugro Synergy. The UBGH2 was performed to understand the distribution of gas hydrates as required for a resource assessment and to find potential candidate sites suitable for a future offshore production test, especially targeting gas hydrate-bearing sand bodies in the basin. The UBGH2 sites were distributed across most of the basin and were selected to target mainly sand-rich turbidite deposits. The 84-day long expedition consisted of two phases. The first phase included logging-while-drilling/measurements-while-drilling (LWD/MWD) operations at 13 sites. During the second phase, sediment cores were collected from 18 holes at 10 of the 13 LWD/MWD sites. Wireline logging (WL) and vertical seismic profile (VSP) data were also acquired after coring operations at two of these 10 sites. In addition, seafloor visual observation, methane sensing, as well as push-coring and sampling using a Remotely Operated Vehicle (ROV) were conducted during both phases of the expedition. Recovered gas hydrates occurred either as pore-filling medium associated with discrete turbidite sand layers, or as fracture-filling veins and nodules in muddy sediments. Gas analyses indicated that the methane within the sampled gas hydrates is primarily of biogenic origin. This paper provides a summary of the operational and scientific results of the UBGH2 expedition as described in 24 papers that make up this special issue of the Journal of Marine and Petroleum Geology.

Late Pleistocene dune activity in the central Great Plains, USA

USGS Publications Warehouse

Mason, J.A.; Swinehart, J.B.; Hanson, P.R.; Loope, D.B.; Goble, R.J.; Miao, X.; Schmeisser, R.L.

2011-01-01

Stabilized dunes of the central Great Plains, especially the megabarchans and large barchanoid ridges of the Nebraska Sand Hills, provide dramatic evidence of late Quaternary environmental change. Episodic Holocene dune activity in this region is now well-documented, but Late Pleistocene dune mobility has remained poorly documented, despite early interpretations of the Sand Hills dunes as Pleistocene relicts. New optically stimulated luminescence (OSL) ages from drill cores and outcrops provide evidence of Late Pleistocene dune activity at sites distributed across the central Great Plains. In addition, Late Pleistocene eolian sands deposited at 20-25 ka are interbedded with loess south of the Sand Hills. Several of the large dunes sampled in the Sand Hills clearly contain a substantial core of Late Pleistocene sand; thus, they had developed by the Late Pleistocene and were fully mobile at that time, although substantial sand deposition and extensive longitudinal dune construction occurred during the Holocene. Many of the Late Pleistocene OSL ages fall between 17 and 14 ka, but it is likely that these ages represent only the later part of a longer period of dune construction and migration. At several sites, significant Late Pleistocene or Holocene large-dune migration also probably occurred after the time represented by the Pleistocene OSL ages. Sedimentary structures in Late Pleistocene eolian sand and the forms of large dunes potentially constructed in the Late Pleistocene both indicate sand transport dominated by northerly to westerly winds, consistent with Late Pleistocene loess transport directions. Numerical modeling of the climate of the Last Glacial Maximum has often yielded mean monthly surface winds southwest of the Laurentide Ice Sheet that are consistent with this geologic evidence, despite strengthened anticyclonic circulation over the ice sheet. Mobility of large dunes during the Late Pleistocene on the central Great Plains may have been the result of cold, short growing seasons with relatively low precipitation and low atmospheric CO2 that increased plant moisture stress, limiting the ability of vegetation to stabilize active dune sand. The apparent coexistence of large mobile dunes with boreal forest taxa suggests a Late Pleistocene environment with few modern analogs. ?? 2011 Elsevier Ltd.

Thermomechanical properties and fracture of resin-bonded-sand cores - Experimental study and application in aluminium foundry

NASA Astrophysics Data System (ADS)

Menet, Claire; Reynaud, Pascal; Fantozzi, Gilbert; Thibault, Delphine; Laforêt, Adrien

2017-06-01

Sand cores are used to produce internal cavities of metallic cast parts with complex shapes like automotive cylinder heads. Foundry cores are granular materials made of sand grains aggregated with binder bridges. In the cold box coring process, the binder is a polyurethane resin. It is noteworthy that during the casting of the liquid metal, the polymer binder is seriously damaged. This kind of materials has been poorly investigated so far. This study aims for a better understanding of the mechanical behaviour and fracture of cores subjected to various loads and thermal ageing. Particularly, the focus is on the decoring step, which consists in removing the sand by hammering and vibration of the metallic part after casting. This major project, generated from the collaboration of the aluminum casting company Montupet, and two laboratories Centre des Matériaux (CdM) and MATEIS, includes both experimental and numerical activities in order to model the decoring step of cylinder heads based on empiric data. Here, the experimental part of the work is presented.

Initial Results on the Extraterrestrial Component of New Sediment Cores Containing Deposits of the Eltanin Impact Event

NASA Technical Reports Server (NTRS)

Kyte, Frank T.; Gersonde, Rainer

2003-01-01

Background The impact of the Eltanin asteroid into the Bellingshausen Sea (2.15 Ma) is the only known impact in a deep-ocean (approx. 5 km) basin. In 1995, Polarstern expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5 S, 91 W) contained well-preserved impact deposits. Sediments of Eocene age and younger were ripped up and redeposited by the impact. The depositional sequence produced by the impact has three units: a chaotic assemblage of sediment fragments up to 50 cm, followed by laminated sands deposited as a turbulent flow, and finally silts and clays that accumulated from dispersed sediments in the water column. The meteoritic impact ejecta, which is composed of shock-melted asteroidal materials and unmelted meteorites, settled through the water column and concentrated near the top of the laminated sands.

Improvements in Fabrication of Sand/Binder Cores for Casting

NASA Technical Reports Server (NTRS)

Bakhitiyarov, Sayavur I.; Overfelt, Ruel A.; Adanur, Sabit

2005-01-01

Three improvements have been devised for the cold-box process, which is a special molding process used to make sand/binder cores for casting hollow metal parts. These improvements are: The use of fiber-reinforced composite binder materials (in contradistinction to the non-fiber-reinforced binders used heretofore), The substitution of a directed-vortex core-blowing subprocess for a prior core-blowing process that involved a movable gassing plate, and The use of filters made from filtration-grade fabrics to prevent clogging of vents. For reasons that exceed the scope of this article, most foundries have adopted the cold-box process for making cores for casting metals. However, this process is not widely known outside the metal-casting industry; therefore, a description of pertinent aspects of the cold-box process is prerequisite to a meaningful description of the aforementioned improvements. In the cold-box process as practiced heretofore, sand is first mixed with a phenolic resin (considered to be part 1 of a three-part binder) and an isocyanate resin (part 2 of the binder). Then by use of compressed air, the mixture is blown into a core box, which is a mold for forming the core. Next, an amine gas (part 3 of the binder) that acts as a catalyst for polymerization of parts 1 and 2 is blown through the core box. Alternatively, a liquid amine that vaporizes during polymerization can be incorporated into the sand/resin mixture. Once polymerization is complete, the amine gas is purged from the core box by use of compressed air. The finished core is then removed from the core box.

Seismic Imaging and Hydrogeologic Characterization of the Potomac Formation in Northern New Castle County, Delaware

NASA Astrophysics Data System (ADS)

Velez, C. C.; McLaughlin, P. P.; McGeary, S.

2008-05-01

A land streamer system, an alternative to conventional seismic acquisition equipment for collecting large amounts of seismic reflection data in urbanized and semi urbanized areas, is being used to conduct a near surface high-resolution seismic experiment in Northern New Castle County, Delaware. The main goal of this project is to provide continuous data of the subsurface in order to improve our understanding on the connectivity of sand bodies and water flow pathways distribution in ancient fluvial deposits, such as those of the Potomac Formation, that were deposited along passive margin, alluvial plain settings. Such understanding is necessary to create accurate models for groundwater flow and to identify groundwater contaminant pathways. The Potomac Formation was deposited during the Albian to early Cenomanian. In northern Delaware, these sediments are entirely fluvial deposits that are thought to onlap Paleozoic basement, and are truncated by an unconformity. McKenna et al. (2004) recognized five facies for this unit in Delaware: amalgamated sands, thick individual sands, thin sands, interlaminated sands, and mottled silts and clays, and described the sands of the unit as being laterally discontinuous, resulting in a "labyrinth style heterogeneity". Benson's (2006) well-log correlations show the depth of the basement ranging from 115 m to 400 m in the study area of this project. A noise test and a 1.2 km long high-resolution seismic reflection line collected using conventional seismic reflection methods during the preliminary phase of the project indicate that seismic methods can be used in this area to image the subsurface as shallow as 18 m and as deep as 315 m, and suggest that the basement is being imaged. During this project, a 30-km seismic dataset and two continuous cores will be collected. Sonic logs collected at the cores will be used to create synthetic seismograms to create depth sections that will be correlated with existing geophysical logs and existing sediment samples to create cross sections, a model of the geometry of the fluvial system, and facies maps. The core samples will be used to determine porosity and permeability which will allow better understanding of the heterogeneity of this unit. This project is important because the methodology to be used will provide a robust 2-D dataset that will allow one to test/revise the existing facies analysis, and stratigraphic correlations that are based in 1-D well data and are actually used for ground water modeling in the state of Delaware where the population depends and benefits from groundwater supply.

Understanding the Role of Typhoons, Fire, and Climate on the Vegetation Dynamics of Tropical Dry Forests: Looking to the Past to Develop Future Management Solutions

DTIC Science & Technology

2010-04-01

centennial -to millennial scale typhoon reconstructions from the western North Pacific are far more limited. Historical government documents of typhoon... Centennial scale swings from humid to drought conditions have been documented in some tropical locations (Hodell et al., 2001). By looking to the past... depressions with a maximum depth of roughly 12 meters. The lagoon hollows are bounded by sand flats and coral reefs (Fig. 2). Core VC9 was located in the

Submarine sand ridges and sand waves in the eastern part of the China Sea

NASA Astrophysics Data System (ADS)

Wu, Ziyin; Li, Shoujun; Shang, Jihong; Zhou, Jieqiong; Zhao, Dineng; Liang, Yuyang

2016-04-01

Integrated with multi-beam and single-beam echo sounding data, as well as historical bathymetric data, submarine bathymetric maps of the eastern part of the China Sea, including the Bohai Sea, Huanghai Sea, and East China Sea, are constructed to systematically study submarine sand ridges and sand waves in the eastern part of the China Sea, combined with high-resolution seismic, sub-bottom profile and borehole data. Submarine sand ridges are extraordinarily developed in the eastern part of the China Sea, and 7 sand ridge areas can be divided from north to south, that is, the Laotieshan Channel sand ridge area in the Bohai Sea, the Korea Bay sand ridge area in the southern Huanghai Sea, the sand ridge area in the eastern Huanghai islands and the Huanghai Troughs, the Jianggang sand ridge area in the western Huanghai Sea, the sand ridge area in the East China Sea shelf, and the sand ridge and sand wave area in the Taiwan Strait and Taiwan Banks. The distribution area of the sand ridges and sand waves covers more than 450,000 km2, wherein ~10,000 km2 in the Bohai Bay, ~200,000 km2 in the Huanghai Sea, ~200,000 km2 in the East China Sea shelf, and ~40,000 km2 in the Taiwan Strait and Taiwan Banks, respectively. The great mass of sand ridges are distributed within water depth of 5-160 m, with a total length of over 160 km and a main width of 5-10 km. The inner structure of the sand ridges presents features of high-angle inclined beddings, with main lithology of sands, sand-mud alternations partly visible, and a small number of mud cores. Dating results indicate that the sand ridges in the eastern part of the China Sea are mainly developed in the Holocene. Sea-level variation dominates the sand ridge evolution in the eastern part of the China Sea since the LGM, and the sand ridges developed in the area of < 60m water depth are appeared in bad activity, meanwhile sand ridges with good activity are still developed in large scale.

Evaluation of stratigraphic relations of sandstone-producing reservoirs in upper Council Grove and Chase groups (Permian) in north-central Oklahoma

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

Chaplin, J.R.

1989-08-01

Poor well control and the absence of surface stratigraphic control made previous interpretations of the stratigraphic relations of sandstone-producing reservoirs tenuous. Recent extensive analyses of surface outcrops and well and core data support the contention that the major sandstone-producing reservoirs can be physically correlated with formations in the outcrop section. Sandstone bodies within the upper Council Grove Group include Neva sand and Blackwell sand (Neva Limestone), Hotson-Kisner sand (Eskridge Shale), and the Whitney-Hodges sand. The Whitney-Hodges sand correlates, in part, with the Speiser Shale (Garrison Formation) of the outcrop section. However, previous usage suggested tentative correlations with sandstone bodies stratigraphicallymore » lower in the section. These sands were probably deposited in channels that were, in part, fluvial, tidal, or estuarine. Production from the Chase Group occurs locally within channelform sandstone bodies referred to as the Hoy-Matfield sand. These sands appear to be equivalent, occupying essentially the position of the Kinney Limestone Member (Matfield Shale) of the outcrop section. Detailed core-hole data at and in the vicinity of Kaw Dam, southeastern Kay County, and outcrops along the shoreline of Kaw Lake at Kaw City, Kay County, clearly demonstrate the facies distribution of the Hoy sand. Core-hole data has also delineated additional potential sandstone reservoirs within and near or at the top of the Fort Riley Limestone Member (Barneston Limestone). The Wolfe sand, a producing sandstone locally, occupies a stratigraphic position within the Doyle Shale.« less

Variability in form and growth of sediment waves on turbidite channel levees

USGS Publications Warehouse

Normark, W.R.; Piper, D.J.W.; Posamentier, H.; Pirmez, C.; Migeon, S.

2002-01-01

Fine-grained sediment waves have been observed in many modern turbidite systems, generally restricted to the overbank depositional element. Sediment waves developed on six submarine fan systems are compared using high-resolution seismic-reflection profiles, sediment core samples (including ODP drilling), multibeam bathymetry, 3D seismic-reflection imaging (including examples of burried features), and direct measurements of turbidity currents that overflow their channels. These submarine fan examples extend over more than three orders of magnitude in physical scale. The presence or absence of sediment waves is not simply a matter of either the size of the turbidite channel-levee systems or the dominant initiation process for the turbidity currents that overflow the channels to form the wave fields. Both sediment-core data and seismic-reflection profiles document the upslope migration of the wave forms, with thicker and coarser beds deposited on the up-current flank of the waves. Some wave fields are orthogonal to channel trend and were initiated by large flows whose direction was controlled by upflow morphology, whereas fields subparallel to channel levees resulted from local spillover. In highly meandering systems, sediment waves may mimic meander planform. Larger sediment waves form on channel-levee systems with thicker overflow of turbidity currents, but available data indicate that sediment waves can be maintaned during conditions of relatively thin overflow. Coarser-grained units in sediment waves are typically laminated and thin-bedded sand as much as several centimetres thick, but sand beds as thick as several tens of centimetres have been documented from both modern and buried systems. Current production of hydrocarbons from sediment-wave deposits suggests that it is important to develop criteria for recognising this overbank element in outcrop exposures and borehole data, where the wavelength of typical waves (several kilometres) generally exceeds outcrop scales and wave heights, which are reduced as a result of consolidation during burial, may be too subtle to recognise. Crown Copyright ?? 2002 Published by Elsevier Science B.V. All rights reserved.

Connecting onshore and offshore near-surface geology: Delaware's sand inventory project

USGS Publications Warehouse

Ramsey, K.W.; Jordan, R.R.; Talley, J.H.

1999-01-01

Beginning in 1988, the Delaware Geological Survey began a program to inventory on-land sand resources suitable for beach nourishment. The inventory included an assessment of the native beach textures using existing data and developing parameters of what would be considered suitable sand textures for Delaware's Atlantic beaches. An assessment of the economics of on-land sand resources was also conducted, and it was determined that the cost of the sand was competitive with offshore dredging costs. In addition, the sand resources were put into a geologic context for purposes of predicting which depositional environments and lithostratigraphic units were most likely to produce suitable sand resources. The results of the work identified several suitable on-land sand resource areas in the Omar and Beaverdam formations that were deposited in barrier-tidal delta and fluvial-estuarine environments, respectively. The identified on-land resources areas have not been utilized due to difficulties of truck transport and development pressures in the resource areas. The Delaware Geological Survey's participation in years 8, 9, and 10 of the Continental Margins Program was developed to extend the known resource areas onshore to offshore Delaware in order to determine potential offshore sand resources for beach nourishment. Years 8 and 9 involved primarily the collection of all available data on the offshore geology. These data included all seismic lines, surface grab samples, and cores. The data were filtered for those that had reliable locations and geologic information that could be used for geologic investigations. Year 10 completed the investigations onshore by construction of a geologic cross-section from data along the coast of Delaware from Cape Henlopen to Fenwick. This cross section identified the geologic units and potential sand resource bodies as found immediately along the coast. These units and resources are currently being extended offshore and tied to known and potential sand resources as part of the continuing cooperative effort between the Delaware Geological Survey and the Minerals Management Service's INTERMAR office as sand resources are identified in federal waters off Delaware. Offshore sand resources are found in the Pliocene Beaverdam Formation offshore where overlying Quaternary units have been stripped, in the tidal delta complexes of several Quaternary units likely equivalent to the onshore Omar Formation, and in late Pleistocene- and Holocene-age shoal complexes. Onshore lithostratigraphic units can be traced offshore and show another reason for continued geologic mapping both onshore and offshore.The Delaware Geological Survey's participation in years 8, 9, and 10 of the Continental Margins Program was developed to extend the known resource areas onshore to offshore Delaware in order to determine potential offshore sand resources for beach nourishment. Years 8 and 9 involved primarily the collection of all available data on the offshore geology. These data included all seismic lines, surface grab samples, and cores. The data were filtered for those that had reliable locations and geologic information that could be used for geologic investigations. Year 10 completed the investigations onshore by construction of a geologic cross-section from data along the coast of Delaware from cape Henlopen to Fenwick.

Mechanics of a granular skin

NASA Astrophysics Data System (ADS)

Karmakar, Somnath; Sane, Anit; Bhattacharya, S.; Ghosh, Shankar

2017-04-01

Magic sand, a hydrophobic toy granular material, is widely used in popular science instructions because of its nonintuitive mechanical properties. A detailed study of the failure of an underwater column of magic sand shows that these properties can be traced to a single phenomenon: the system self-generates a cohesive skin that encapsulates the material inside. The skin, consisting of pinned air-water-grain interfaces, shows multiscale mechanical properties: they range from contact-line dynamics in the intragrain roughness scale, to plastic flow at the grain scale, all the way to sample-scale mechanical responses. With decreasing rigidity of the skin, the failure mode transforms from brittle to ductile (both of which are collective in nature) to a complete disintegration at the single-grain scale.

Oil migration in a major growth fault: Structural analysis of the Pathfinder core, South Eugene Island Block 330, offshore Louisiana

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

Losh, S.

1998-09-01

The Pathfinder core, collected in the South Eugene Island Block 330 field, offshore Louisiana, provides an outstanding sample of structures associated with a major growth fault that abuts a giant oil field and that is thought to have acted as a conduit for hydrocarbon migration into the producing reservoirs. The fault zone in the core consists of three structural domains, each characterized by a distinct rock type, distribution of fault dips and dip azimuths, and distribution of spacing between adjacent faults and fractures. Although all of the domains contain oil-bearing sands, only faults and fractures in the deepest domain containmore » oil, even though the oil-barren fault domains contain numerous faults and fractures that are parallel to those containing oil in the deepest domain. The deepest domain is also distinguished from the other two domains by a greater degree of structural complexity and by a well-defined power-law distribution of fault and fracture spacings. Even though oil is present in sands throughout the core, its restriction to faults and fractures in the youngest sampled portion of the fault zone implies that oil migrated only through that part of the fault that was active during the time when oil had access to it. The absence of oil in fractures or faults in the other, probably older, fault domains indicates that the oil was never sufficiently pressured to flow up the fault zone on its own, either by hydraulic fracture or by increased permeability as a result of decreased effective stress. Instead, fluid migration along faults and fractures in the Pathfinder core was enhanced by permeability created in response to relatively far-field stresses related to minibasin subsidence.« less

Mapping epibenthic assemblages and their relations to sedimentary features in shallow-water, high-energy environments

NASA Astrophysics Data System (ADS)

Sisson, John D.; Shimeta, Jeff; Zimmer, Cheryl Ann; Traykovski, Peter

2002-03-01

Knowledge of spatial relationships among benthic biota and sedimentary features in shallow-water (<30 m) high-energy environments has been severely limited by sampling technology. We describe and report tests of a SCUBA-diving mapping method specifically for this region. Underwater acoustic location is used to achieve meter-scale resolution over kilometer-scale regions of the sea floor. A triad of acoustic transponders is bottom-mounted at known positions, 300-500 m apart. Transported by underwater personal vehicles, SCUBA-divers map the bed using hand-held acoustic receivers that record ranges to the transponders. The mean error of acoustic fixes was 2.4±1.2 m in a 0.5 km×1.0 km test area. Dense assemblages of epibenthic animals were mapped relative to sediment texture and bedforms off the exposed south coast of Martha's Vineyard Island, Massachusetts, USA. Surveys one month apart within a 0.6 km×0.6 km area (8-12 m depth) revealed 100-m-scale patches of the tube worm Spiophanes bombyx (⩽30,000 m -2) in fine sand and of the sand dollar Echinarachnius parma (⩽55 m -2) in coarse sand. Raised mud patches that, together with fine sand, occurred in two shore-perpendicular belts are likely exposed, ancient marsh deposits. Depth gradients of sand-ripple geometry indicated that ripples in deeper areas were not in equilibrium with wave conditions monitored during surveys; i.e., they were relict ripples. Thus, sand dollars in some areas may have had >1 month to rework surficial sands since their transformation by physical processes. Linear regressions of ripple characteristics against sand dollar or tube worm densities were not significant, although such relationships would be highly dependent on temporal scale. The survey method described here can be used at more frequent intervals to explore such interactions between epibenthic animals and sediment-transport dynamics.

Conceptual hydrogeologic framework of the shallow aquifer system at Virginia Beach, Virginia

USGS Publications Warehouse

Smith, Barry S.; Harlow, George E.

2002-01-01

The hydrogeologic framework of the shallow aquifer system at Virginia Beach was revised to provide a better understanding of the distribution of fresh ground water, its potential use, and its susceptibility to contamination. The revised conceptual framework is based primarily on analyses of continuous cores and downhole geophysical logs collected at 7 sites to depths of approximately 200 ft.The shallow aquifer system at Virginia Beach is composed of the Columbia aquifer, the Yorktown confining unit, and the Yorktown-East-over aquifer. The shallow aquifer system is separated from deeper units by the continuous St. Marys confining unit.The Columbia aquifer is defined as the predominantly sandy surficial deposits above the Yorktown confining unit. The Yorktown confining unit is composed of a series of very fine sandy to silty clay units of various colors at or near the top of the Yorktown Formation. The Yorktown confining unit varies in thickness and in composition, but on a regional scale is a leaky confining unit. The Yorktown-Eastover aquifer is defined as the predominantly sandy deposits of the Yorktown Formation and the upper part of the Eastover Formation above the confining clays of the St. Marys Formation. The limited areal extent of highly permeable deposits containing freshwater in the Yorktown-Eastover aquifer precludes the installation of highly productive freshwater wells over most of the city. Some deposits of biofragmental sand or shell hashes in the Yorktown-Eastover aquifer can support high-capacity wells.A water sample was collected from each of 10 wells installed at 5 of the 7 core sites to determine the basic chemistry of the aquifer system. One shallow well and one deep well was installed at each site. Concentrations of chloride were higher in the water from the deeper well at each site. Concentrations of dissolved iron in all of the water samples were higher than the U.S. Environmental Protection Agency Secondary Drinking Water Regulations. Concentrations of manganese and chloride were higher than the Secondary Drinking Water Regulations in samples from some wells.In the humid climate of Virginia Beach, the periodic recharge of freshwater through the sand units of the shallow aquifer system occurs often enough to create a dynamic equilibrium whereby freshwater flows continually down and away from the center of the ridges to mix with and sweep brackish water and saltwater back toward the tidal rivers, bays, salt marshes, and the Atlantic Ocean.The aquifers and confining units of the shallow aquifer system at Virginia Beach are heterogeneous, discontinuous, and without exact marker beds, which makes correlations in the study area difficult. Investigations using well cuttings, spot cores, or split-spoon samples with geophysical logs are not as definitive as continuous cores for determining or correlating hydrogeologic units. Future investigations of the shallow aquifer system would benefit by collecting continuous cores.

Site selection for DOE/JIP gas hydrate drilling in the northern Gulf of Mexico

USGS Publications Warehouse

Hutchinson, Deborah; Shelander, Dianna; Dai, J.; McConnell, D.; Shedd, William; Frye, Matthew; Ruppel, Carolyn D.; Boswell, R.; Jones, Emrys; Collett, Timothy S.; Rose, Kelly K.; Dugan, Brandon; Wood, Warren T.

2008-01-01

n the late spring of 2008, the Chevron-led Gulf of Mexico Gas Hydrate Joint Industry Project (JIP) expects to conduct an exploratory drilling and logging campaign to better understand gas hydrate-bearing sands in the deepwater Gulf of Mexico. The JIP Site Selection team selected three areas to test alternative geological models and geophysical interpretations supporting the existence of potential high gas hydrate saturations in reservoir-quality sands. The three sites are near existing drill holes which provide geological and geophysical constraints in Alaminos Canyon (AC) lease block 818, Green Canyon (GC) 955, and Walker Ridge (WR) 313. At the AC818 site, gas hydrate is interpreted to occur within the Oligocene Frio volcaniclastic sand at the crest of a fold that is shallow enough to be in the hydrate stability zone. Drilling at GC955 will sample a faulted, buried Pleistocene channel-levee system in an area characterized by seafloor fluid expulsion features, structural closure associated with uplifted salt, and abundant seismic evidence for upward migration of fluids and gas into the sand-rich parts of the sedimentary section. Drilling at WR313 targets ponded sheet sands and associated channel/levee deposits within a minibasin, making this a non-structural play. The potential for gas hydrate occurrence at WR313 is supported by shingled phase reversals consistent with the transition from gas-charged sand to overlying gas-hydrate saturated sand. Drilling locations have been selected at each site to 1) test geological methods and models used to infer the occurrence of gas hydrate in sand reservoirs in different settings in the northern Gulf of Mexico; 2) calibrate geophysical models used to detect gas hydrate sands, map reservoir thicknesses, and estimate the degree of gas hydrate saturation; and 3) delineate potential locations for subsequent JIP drilling and coring operations that will collect samples for comprehensive physical property, geochemical and other analyses

Hurricane Sandy washover deposits on Fire Island, New York

USGS Publications Warehouse

La Selle, SeanPaul M.; Lunghino, Brent D.; Jaffe, Bruce E.; Gelfenbaum, Guy; Costa, Pedro J.M.

2017-02-16

Washover deposits on Fire Island, New York, from Hurricane Sandy in 2012 were investigated a year after the storm to document the sedimentary characteristics of hurricane washover features. Sediment data collected in the field includes stratigraphic descriptions and photos from trenches, bulk sediment samples, U-channels, and gouge and push cores. Samples and push cores were further analyzed in the laboratory for grain size, density variations using x-ray computed tomography (CT), and surface microtexture using a scanning electron microscope (SEM). Elevation profiles of washover features were measured using Differential Global Positioning System (DGPS) with Real Time Kinematic processing. The DGPS elevations were compared to lidar (light detection and ranging) data from pre- and post-Sandy surveys to assess the degree to which washover deposit thicknesses changed within the year following deposition. Hurricane Sandy washover deposits as much as 1 meter thick were observed in trenches. Initial results show that the upper parts of the deposits have been reworked significantly in some places by wind, but there are still areas where the deposits are almost entirely intact. Where mostly intact, the washover deposits consist of massive or weakly laminated sand near the base, overlain by more strongly laminated sands.

Sample support and resistivity imaging interpretation

NASA Astrophysics Data System (ADS)

Bentley, L. R.; Gharibi, M.

2003-04-01

Three-D Electrical Resistivity Imaging (ERI) is a powerful technique that can be used to improve site characterization. In order to integrate ERI with other site characterization measurements such as soil and water chemistry, it is necessary to understand the sample support of various data. We have studied a decommissioned sour gas processing plant which has experienced releases of glycol and amine. Ammonium and acetic acid are degradation products that cause elevated electrical conductivity (EC) in groundwater and soils.The site is underlain by glacial till that is fractured and has thin sand lenses. 3-D ERI inversion results, direct push tool EC and core EC from the same location are well correlated. However, groundwater EC from piezometer installations are poorly correlated with ERI EC. We hypothesize that the ERI, direct push and core EC are mainly meausuring relatively immobile pore water EC in the fine grain matrix. Piezometer water is derived from mobile groundwater that travels in preferred flow paths such as fractures and higher permeability sand lenses. Due to dewatering and other remediation efforts, the mobile groundwater can have a different chemistry, concentration and EC than the immobile pore water. Consequently, the sample support is different for the groundwater samples and the difference explains the poor correlation between ERI EC and groundwater sample EC. In this particular case, we have the potential to monitor the chemical evolution of the source areas, but cannot use ERI to monitor the chemical evolution of mobile groundwater.

Characterization of gas hydrate reservoirs by integration of core and log data in the Ulleung Basin, East Sea

USGS Publications Warehouse

Bahk, J.-J.; Kim, G.-Y.; Chun, J.-H.; Kim, J.-H.; Lee, J.Y.; Ryu, B.-J.; Lee, J.-H.; Son, B.-K.; Collett, Timothy S.

2013-01-01

Examinations of core and well-log data from the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) drill sites suggest that Sites UBGH2-2_2 and UBGH2-6 have relatively good gas hydrate reservoir quality in terms of individual and total cumulative thicknesses of gas-hydrate-bearing sand (HYBS) beds. In both of the sites, core sediments are generally dominated by hemipelagic muds which are intercalated with turbidite sands. The turbidite sands are usually thin-to-medium bedded and mainly consist of well sorted coarse silt to fine sand. Anomalies in infrared core temperatures and porewater chlorinity data and pressure core measurements indicate that “gas hydrate occurrence zones” (GHOZ) are present about 68–155 mbsf at Site UBGH2-2_2 and 110–155 mbsf at Site UBGH2-6. In both the GHOZ, gas hydrates are preferentially associated with many of the turbidite sands as “pore-filling” type hydrates. The HYBS identified in the cores from Site UBGH2-6 are medium-to-thick bedded particularly in the lower part of the GHOZ and well coincident with significant high excursions in all of the resistivity, density, and velocity logs. Gas-hydrate saturations in the HYBS range from 12% to 79% with an average of 52% based on pore-water chlorinity. In contrast, the HYBS from Site UBGH2-2_2 are usually thin-bedded and show poor correlations with both of the resistivity and velocity logs owing to volume averaging effects of the logging tools on the thin HYBS beds. Gas-hydrate saturations in the HYBS range from 15% to 65% with an average of 37% based on pore-water chlorinity. In both of the sites, large fluctuations in biogenic opal contents have significant effects on the sediment physical properties, resulting in limited usage of gamma ray and density logs in discriminating sand reservoirs.

Depositional analysis of Hill sand of Rodessa Formation (lower Cretaceous) in north Shongaloo-Red Rock field, Webster Parish, Louisiana

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

Adamick, J.A.; Sartin, A.A.

1988-09-01

Hill sand is an informal subdivision of the Lower Cretaceous Rodessa Formation and is a common hydrocarbon reservoir in northeastern Texas, northern Louisiana, and southern Arkansas. The Hill sand is lithologically variable within the study area and consists of conglomerate, fine-grained sandstone, siltstone, mottled red-green claystone, black shale, and limestone. Five depositional environments were interpreted for lithofacies present in Hill sand cores from the North Shongaloo-Red Rock field. These include facies A, fluvial point bar; facies B, crevasse system; facies C, interdistributary bay; facies D, swamp; and facies E, carbonate interdistributary bay. Fluvial point bar and crevasse deposits commonly formmore » hydrocarbon reservoirs in the field. On a regional scale, depositional environments observed in the Hill sand include several fluvial deposystems trending northeast-southwest through Webster Parish. These deposystems terminate into deltaic distributary mouth bars along a northwest-southeast-trending coastline. Areas west of the coastline were occupied by shallow marine environments. Interchannel areas east of the coastline were occupied by interdistributary bay, lake, and crevasse environments in lower deltaic areas, and by lake, swamp, and crevasse environments in upper deltaic areas. Lowermost deposits of the Hill sand throughout the region are interpreted to consist of shallow marine environments. These marine deposits were overlain by thick, predominantly nonmarine sediments. Near the end of Hill sand deposition, the entire region was covered by very shallow marine environments, prior to deposition of the overlying First Lower Anhydrite Stringer.« less

Analysis of total metals in waste molding and core sands from ferrous and non-ferrous foundries.

PubMed

Miguel, Roberto E; Ippolito, James A; Leytem, April B; Porta, Atilio A; Banda Noriega, Roxana B; Dungan, Robert S

2012-11-15

Waste molding and core sands from the foundry industry are successfully being used around the world in geotechnical and soil-related applications. Although waste foundry sands (WFSs) are generally not hazardous in nature, relevant data is currently not available in Argentina. This study aimed to quantify metals in waste molding and core sands from foundries using a variety of metal-binder combinations. Metal concentrations in WFSs were compared to those in virgin silica sands (VSSs), surface soils and soil guidance levels. A total analysis for Ag, Al, Ba, Be, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sb, Te, Tl, V, and Zn was conducted on 96 WFSs and 14 VSSs collected from 17 small and medium-sized foundries. The majority of WFSs analyzed, regardless of metal cast and binder type, contained metal concentrations similar to those found in VSSs and native soils. In several cases where alkyd urethane binder was used, Co and Pb concentrations were elevated in the waste sands. Elevated Cr, Mo, Ni, and Tl concentrations associated with VSSs should not be an issue since these metals are bound within the silica sand matrix. Because of the naturally low metal concentrations found in most WFSs examined in this study, they should not be considered hazardous waste, thus making them available for encapsulated and unencapsulated beneficial use applications. Published by Elsevier Ltd.

Effects of core retrieval, handling, and preservation on hydrate-bearing samples

NASA Astrophysics Data System (ADS)

Kneafsey, T. J.; Lu, H.; Winters, W. J.; Hunter, R. B.

2009-12-01

Recovery, preservation, storage, and transport of samples containing natural gas hydrate cause changes in the stress conditions, temperature, pressure, and hydrate saturation of samples. Sample handling at the ground surface and sample preservation, either by freezing in liquid nitrogen (LN) or repressurization using methane, provides additional time and driving forces for sample alteration. The extent to which these disturbances alter the properties of the hydrate bearing sediments (HBS) depend on specific sample handling techniques, as well as on the sample itself. HBS recovered during India’s National Gas Hydrate Program (NGHP) Expedition 01 and the 2007 BP Exploration Alaska - Department of Energy - U.S. Geological Survey (BP-DOE-USGS) Mount Elbert (ME) gas hydrate well on the Alaskan North Slope provide comparisons of sample alterations induced by multiple handling techniques. HBS samples from the NGHP and the ME projects were examined using x-ray computed tomography. Mount Elbert sand samples initially preserved in LN have non-uniform short “crack-like” low-density zones in the center that probably do not extend to the outside perimeter. Samples initially preserved by repressurization show fewer “crack-like” features and higher densities. Two samples were analyzed in detail by Lu and coworkers showing reduced hydrate saturations approaching the outer surface, while substantial hydrate remained in the central region. Non-pressure cored NGHP samples show relatively large altered regions approaching the core surface, while pressure-cored-liquid-nitrogen preserved samples have much less alteration.

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

Miller, D. H.; Reigel, M. M.

A full-scale formed core sampler was designed and functionally tested for use in the Saltstone Disposal Facility (SDF). Savannah River National Laboratory (SRNL) was requested to compare properties of the formed core samples and core drilled samples taken from adjacent areas in the full-scale sampler. While several physical properties were evaluated, the primary property of interest was hydraulic conductivity. Differences in hydraulic conductivity between the samples from the formed core sampler and those representing the bulk material were noted with respect to the initial handling and storage of the samples. Due to testing conditions, the site port samples were exposedmore » to uncontrolled temperature and humidity conditions prior to testing whereas the formed core samples were kept in sealed containers with minimal exposure to an uncontrolled environment prior to testing. Based on the results of the testing, no significant differences in porosity or density were found between the formed core samples and those representing the bulk material in the test stand.« less

Sample descriptions and geophysical logs for cored well BP-3-USGS, Great Sand Dunes National Park and Preserve, Alamosa County, Colorado

USGS Publications Warehouse

Grauch, V.J.S.; Skipp, Gary L.; Thomas, Jonathan V.; Davis, Joshua K.; Benson, Mary Ellen

2015-01-01

BP-3-USGS was sited to test hypotheses developed from geophysical studies and to answer questions about the history and evolution of Pliocene and Pleistocene Lake Alamosa, which is represented by lacustrine deposits sampled by the well. The findings reported here represent a basis from which future studies can answer these questions and address other important scientific questions in the San Luis Valley regarding geologic history and climate change, groundwater hydrology, and geophysical interpretation.

Applications of resistivity modeling in reservoir development: examples from Balder Field, Norwegian North Sea

USGS Publications Warehouse

Paillet, Frederick L.; Haynes, F.M.; Buretz, O.M.

2001-01-01

The massive Paleocene oil sands of the Balder Field are overlain by several thinly bedded Eocene sand-prone packages of variable facies and reservoir quality. Although these sands have been penetrated by numerous exploration and development wells, uncertainty remains as to their extent, distribution, and ultimate effect on reservoir performance. The section is geologically complex (thin beds, injected sands, shale clasts and laminae, and faulting), and also contains a field-wide primary gas cap. With a depletion plan involving both gas and water injection, geologic/reservoir characterization of the Eocene is critical for prudent resource management during depletion. With this goal, resistivity modeling and core-based thin bed reservoir description from the first phase of development drilling have been integrated with seismic attribute mapping. Detailed core description, core permeability and grain size distribution data delineate six facies and help in distinguishing laterally continuous massive and laminated sands from potentially non-connected injection sands and non-reservoir quality siltstones and tuffs. Volumetric assessment of the thin sand resource has been enhanced by I-D forward modeling of induction log response using a commercial resistivity modeling program, R,BAN. After defining beds and facies with core and high resolution log data, the AHF60 array induction curve response was approximated using the 6FF40 response. Because many of the beds were thinner than 6FF40 resolution, the modeling is considered to provide a lower bound on R,. However, for most beds this model-based R, is significantly higher than that provided by one-foot vertical resolution shallow resistivity data, and is thought to be the best available estimate of true formation resistivity. Sensitivities in STOOIP were assessed with multiple R, earth models which can later be tested against production results. In addition, water saturation height functions, developed in vertical wells and thick beds, can be validated in deviated wells with thin beds. Sand thickness models constrained by this logand core-based petrophysical analysis were used to build impedance seismic synthetic sections from which seismic attributes could be extracted and calibrated. The model-based attribute calibration was then applied to the seismic impedance 3-D cube permitting sand thickness to be mapped and reservoir geology to be modeled with significantly more detail than previously possible. These results will guide the field''s reservoir management and assist in the delineation of new targets.

Coastal eolian sand-ramp development related to paleo-sea-level changes during the Latest Pleistocene and Holocene (21–0 ka) in San Miguel Island, California, U.S.A.

USGS Publications Warehouse

Peterson, Curt D.; Erlandson, Jon M.; Stock, Errol; Hostetler, Steven W.; Price, David M.

2017-01-01

Coastal eolian sand ramps (5–130 m elevation) on the northern slope (windward) side of the small San Miguel Island (13 km in W-E length) range in age from late Pleistocene to modern time, though a major hiatus in sand-ramp growth occurred during the early Holocene marine transgression (16–9 ka). The Holocene sand ramps (1–5 m measured thicknesses) currently lack large dune forms, thereby representing deflated erosional remnants, locally covering thicker late Pleistocene sand-ramp deposits. The ramp sand was initially supplied from the adjacent island-shelf platform, extending about 20 km north of the present coastline. The sand-ramp deposits and interbedded loess soils were 14C dated using 112 samples from 32 archaeological sites and other geologic sections. Latest Pleistocene sand ramps (66–18 ka) were derived from across-shelf eolian sand transport during marine low stands. Shoreward wave transport supplied remobilized late Pleistocene sand from the inner shelf to Holocene beaches, where dominant NW winds supplied sand to the sand ramps. The onset dates of the sand-ramp deposition in San Miguel are 7.2 ± 1.5 ka (sample n = 14). The internal strata dates in the vertically accreting sand ramps are 3.4 ± 1.7 ka (n = 34). The sand ramps in San Miguel show wide-scale termination of sand supply in the latest Holocene time. The sand-ramp top dates or burial dates are 1.7 ± 0.9 ka (n = 28). The latest Holocene sand ramps are truncated along most of the island's northern coastline, indicating recent losses of nearshore sand reserves to onshore, alongshore, and, possibly, offshore sand sinks. The truncated sand ramps in San Miguel Island and in other sand-depleted marine coastlines provide warnings about future beach erosion and/or shoreline retreat from accelerated sea-level rise accompanying predicted global warming.

Publications - GMC 356 | Alaska Division of Geological & Geophysical

Science.gov Websites

corresponding report entitled Coring for Methane-Hydrate in shallow sands of the Sagavanirkick and Canning Ice #1 well log along with corresponding report entitled Coring for Methane-Hydrate in shallow sands Report Information gmc356.pdf (17.0 M) Keywords Coalbed Methane; Methane Top of Page Department of

77 FR 16554 - Endangered and Threatened Wildlife and Plants; Receipt of Applications for Incidental Take...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-21

... tiered sand-filled geotextile containers as its core that is regularly maintained with 3 feet of beach...--such as mitigation, sea turtle monitoring, physical monitoring, maintenance of sand coverage, and removal of the dune core container system--are assured by: (a) Funds that will be placed annually in an...

Holocene moisture variations over the arid central Asia revealed by a comprehensive sand-dune record from the central Tian Shan, NW China

NASA Astrophysics Data System (ADS)

Long, Hao; Shen, Ji; Chen, Jianhui; Tsukamoto, Sumiko; Yang, Linhai; Cheng, Hongyi; Frechen, Manfred

2017-10-01

Arid central Asia (ACA) is one of the largest arid (desert) areas in the world, and its climate is dominated by the westerlies. In this study, we examined sand dune evolution from the Bayanbulak Basin in the Tian Shan (Xinjiang, NW China), aiming to infer the Holocene moisture history of the ACA. Combined with stratigraphic observation and environmental proxies analysis (grain size, magnetic susceptibility and total organic content), large numbers of luminescence ages from multiple sites (eight sections, 79 samples) were applied to reconstruct the evolution of the sand dune accumulation in the study basin. The overall results imply very dry conditions characterized by sand dune accumulation at ∼12-6.5 ka, a wet interval between ∼6.5 and 0.8 ka when soil formation occurred, and decreased moisture during the last 0.8 ka. This moisture variation pattern is generally consistent with that inferred from many lacustrine records in the core zone of ACA, suggesting a widespread dry period in the early-to-middle Holocene and relatively wet middle-to-late Holocene. Thus, the moisture history derived from the current sand dune system contrasts with that in Asian monsoon areas, which are characterized by a strong monsoon (high precipitation) in the early and mid-Holocene and a weak monsoon (low precipitation and dry climate) during the late Holocene. Our results strongly suggest that the winter solar insolation and the external boundary conditions such as atmospheric CO2 concentration, ice sheets, and meltwater fluxes, have been major influential factors triggering the Holocene moisture evolution in the core zone of ACA.

Modern Estuarine Sedimentation in Suisun Bay, California

NASA Astrophysics Data System (ADS)

Chin, J. L.; Orzech, K.; Anima, R. J.; Jaffe, B.

2002-12-01

Suisun Bay is the northeasternmost part of San Francisco Bay (California), the largest estuary on the Pacific Coast of the United States. Suisun Bay's geographic and morphologic position are unique in that it occupies the head of the estuary and is subject to the maximum freshwater inflow and sediment input of the Sacramento-San Joaquin Rivers, whose drainage basin covers 40% of the land area of California. Suisun Bay consists of two smaller subembayments, Grizzly and Honker Bays. Gravity cores obtained in 1990-1991 and 1999 were analyzed to delineate depositional environments and sedimentation patterns in Suisun Bay. Major depositional environments include: tidal channel (subtidal), tidal channel banks (subtidal), tidal flat (intertidal to subtidal), and bay mouth (subtidal). The tidal channel environment includes both large and small channels in Suisun Bay as well as the tidal sloughs Suisun and Montezuma Sloughs. The coarsest sediment, usually sand or muddy sand, characterize this environment and water depths range from 2 to 11 m. Thin (1-2 mm) and discontinuous silt and clay laminae are common. Suisun and Montezuma Sloughs are the exception to this pattern in that they consist of massive, intensely bioturbated muds. Tidal channel banks (both "cut" and "accretionary" channel margins), particularly accretionary banks, are characterized by low-to-moderate bioturbation and sandy mud to muddy sand lithology. Typically alternating sand and mud beds (1-6 cm thick) are present; both types of beds consist of 1mm to 1cm thick subhorizontal to inclined laminae. Laminae composed of organic detritus are also present. Where this environment is transitional with the tidal flat environment water depths range from 2-8 m. Tidal flat environments include the "sand" shoals present on bathymetry charts, and are typically a bioturbated muddy sand to sandy mud. Sand and mud beds, 1-3 cm thick, are often characterized by very fine 1-2 mm thick silt and mud laminae. Water depths range from 2 to 4.5 m where these laminated tidal flat sediments occur. Bay mouth environments occur only in the distal portions of Grizzly and Honker Bays, subembayments of Suisun Bay proper. This environment is transitional with both tidal channel bank and tidal flat environments and shares characteristics with each. Massive to interbedded mud is the most common lithology, although sandy mud to muddy sand also occurs. Centimeters thick sand and mud beds typically alternate vertically. Bioturbation is low to moderate. Water depths over this environment range from 2 to 3 m. Depositional environments present in Suisun Bay are the result of a full range of tidal and fluvial processes as shown by the lithologies and alternating sediment stratigraphic patterns observed in cores. Very thin beds and intense bioturbation evidence intervals of very slow to negligible sedimentation. Rapid deposition and/or resuspension are evidenced by thick sediment intervals and by laminae that are continuous and apparently unbioturbated. Very fine scale sedimentation that may represent individual ebb and flood events as well as longer term seasonal sedimentation patterns are also present. An additional observation is that almost a quarter of the gravity cores reveal that modern estuarine deposits overlie an erosional surface that separate them from an organic-rich mud. This organic-rich mud, in one core to date, has been radiocarbon dated at roughly 4500 yrs. B.P. (J.Chin and K. Orzech, 2002, unpublished data). The organic-rich mud is interpreted as a tidal marsh deposit that pre-dates the present tidal marshes occurring in Suisun Bay.

Antarctic Glaciation during the Tertiary Recorded in Sub-Antarctic Deep-Sea Cores.

PubMed

Margolis, S V; Kennett, J P

1970-12-04

Study of 18 Cenozoic South Pacific deep-sea cores indicates an association of glacially derived ice-rafted sands and relatively low planktonic foraminiferal diversity with cooling of the Southern Ocean during the Lower Eocene, upper Middle Eocene, and Oligocene. Increased species diversity and reduction or absence of ice-rafted sands in Lower and Middle Miocene cores indicate a warming trend that ended in the Upper Miocene. Antarctic continental glaciation appears to have prevailed throughout much of the Cenozoic.

Regional Similarities and Consistent Patterns of Local Variation in Beach Sand Bacterial Communities throughout the Northern Hemisphere

PubMed Central

Staley, Christopher

2016-01-01

ABSTRACT Recent characterization of the bacterial community structure in beach sands has revealed patterns of biogeography similar to those observed in aquatic environments. Studies to date, however, have mainly focused on subtidal sediments from marine beaches. Here, we investigate the bacterial diversity, using Illumina-based sequencing of the V5-V6 region of the 16S rRNA gene, at 11 beaches representing those next to the Great Lakes, Florida, and the Pacific Ocean. The alpha diversity differed significantly among regions (P < 0.0001), while the within-region diversity was more similar. The beta diversity also differed by region (P < 0.001), where freshwater sands had significantly higher abundances of taxa within the Actinobacteria, Betaproteobacteria, and Verrucomicrobia than marine environments. In contrast, marine sands harbored greater abundances of Gammaproteobacteria and Planctomycetes, and those from Florida had more Deltaproteobacteria and Firmicutes. Marine beaches had significantly different phylogenetic community structures (P ≤ 0.018), but freshwater and Florida beaches showed fewer within-region phylogenetic differences. Furthermore, regionally distinct patterns in taxonomic variation were observed in backshore sands, which had communities distinct from those in nearshore sands (P < 0.001). Sample depth minimally influenced the community composition. The results of this study reveal distinct bacterial community structures in sand on a broad geographic scale but moderate regional similarity and suggest that local variation is primarily related to the distance from the shoreline. This study offers a novel comparison of the bacterial communities in freshwater and marine beach sands and provides an important basis for future comparisons and analyses to elucidate factors affecting microbial ecology in this underexplored environment. IMPORTANCE This study presents a large-scale geographic characterization of the bacterial communities present in beach sands. While previous studies have evaluated how environmental factors influence bacterial community composition, few have evaluated bacterial communities in freshwater sands. Furthermore, the use of a consistent methodology to characterize bacterial communities here allowed a novel comparison of communities across geographic regions. We reveal that while the community composition in sands at individual beaches is distinct, beach sands within the same region harbor similar assemblages of bacteria and these assemblages differ greatly between regions. In addition, moisture, associated with distance from the shoreline, strongly influences the bacteria present in sands and more strongly influences the bacteria present than sample depth does. Thus, the data presented here offer an important basis for a broader characterization of the ecology of bacteria in sands, which may also be relevant to public health and resource management initiatives. PMID:26921429

The geological record of prehistorical tsunami at a coastal area of Beppu Bay in eastern Kyushu, Japan

NASA Astrophysics Data System (ADS)

Yamada, M.; Fujino, S.; Chiba, T.; Shinozaki, T.; Okuwaki, R.; Takeda, D.

2015-12-01

Tsunamis are typically generated by plate-boundary ruptures at subduction zones, but also vertical displacement associated with intraplate earthquakes. Historical written records documented that coasts of Beppu Bay, eastern Kyushu, Japan was devastated by a tsunami associated with the AD 1596 Keicho-Bungo earthquake (M7.0). It is considered that the earthquake occurred at submarine active faults in the bay. The aim of this study is to unravel the occurrence age and source of tsunamis that struck the coast of the bay in prehistorical ages. This study may also make a contribution to the understanding of tsunami-generating system at submarine active faults. We conducted a coring survey at paddy fields along the north coast of the bay. The 10 cm thick muddy sand layer with a few granules (hereinafter, sand layer), bounded by sharp contacts, was evident in the 1.7 m long sediment core taken at 700 m from the shoreline. Plant materials obtained from mud above the sand layer was dated to 1880-2000 cal. yr BP. Sharp contacts between sand and surrounding muds imply that the sand layer is formed by a sudden event. Existence of mud clast in the sand layer indicates erosion of surface mud. There were no brackish-marine diatoms in surrounding mud, but they accounted for 5-6% of the total within the sand layer, indicating that the sand grains were sourced at least in part from brackish-marine environment. Mean grain size/sorting of the sand layer and beach sand were 2.31/0.94 and 2.03/0.41 phi. The difference in sorting probably suggests that the sand layer partly contains the onshore sediments eroded in inundation process. Additional coring surveys would clarify the distribution of prehistorical tsunami deposits and source of past tsunamis.

Direct sampling during multiple sediment density flows reveals dynamic sediment transport and depositional environment in Monterey submarine canyon

NASA Astrophysics Data System (ADS)

Maier, K. L.; Gales, J. A.; Paull, C. K.; Gwiazda, R.; Rosenberger, K. J.; McGann, M.; Lundsten, E. M.; Anderson, K.; Talling, P.; Xu, J.; Parsons, D. R.; Barry, J.; Simmons, S.; Clare, M. A.; Carvajal, C.; Wolfson-Schwehr, M.; Sumner, E.; Cartigny, M.

2017-12-01

Sediment density flows were directly sampled with a coupled sediment trap-ADCP-instrument mooring array to evaluate the character and frequency of turbidity current events through Monterey Canyon, offshore California. This novel experiment aimed to provide links between globally significant sediment density flow processes and their resulting deposits. Eight to ten Anderson sediment traps were repeatedly deployed at 10 to 300 meters above the seafloor on six moorings anchored at 290 to 1850 meters water depth in the Monterey Canyon axial channel during 6-month deployments (October 2015 - April 2017). Anderson sediment traps include a funnel and intervalometer (discs released at set time intervals) above a meter-long tube, which preserves fine-scale stratigraphy and chronology. Photographs, multi-sensor logs, CT scans, and grain size analyses reveal layers from multiple sediment density flow events that carried sediment ranging from fine sand to granules. More sediment accumulation from sediment density flows, and from between flows, occurred in the upper canyon ( 300 - 800 m water depth) compared to the lower canyon ( 1300 - 1850 m water depth). Sediment accumulated in the traps during sediment density flows is sandy and becomes finer down-canyon. In the lower canyon where sediment directly sampled from density flows are clearly distinguished within the trap tubes, sands have sharp basal contacts, normal grading, and muddy tops that exhibit late-stage pulses. In at least two of the sediment density flows, the simultaneous low velocity and high backscatter measured by the ADCPs suggest that the trap only captured the collapsing end of a sediment density flow event. In the upper canyon, accumulation between sediment density flow events is twice as fast compared to the lower canyon; it is characterized by sub-cm-scale layers in muddy sediment that appear to have accumulated with daily to sub-daily frequency, likely related to known internal tidal dynamics also measured in the experiment. The comprehensive scale of the Monterey Coordinated Canyon Experiment allows us to integrate sediment traps with ADCP instrument data and seafloor core samples, which provides important new data to constrain how, when, and what sediment is transported through submarine canyons and how this is archived in seafloor deposits.

23. CORE WORKER OPERATING A COREBLOWER THAT PNEUMATICALLY FILLED CORE ...

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

23. CORE WORKER OPERATING A CORE-BLOWER THAT PNEUMATICALLY FILLED CORE BOXES WITH RESIGN IMPREGNATED SAND AND CREATED A CORE THAT THEN REQUIRED BAKING, CA. 1950. - Stockham Pipe & Fittings Company, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

Gas geochemistry of the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: implications for gas hydrate exploration in the Arctic

USGS Publications Warehouse

Lorenson, T.D.; Collett, T.S.; Hunter, R.B.

2011-01-01

Gases were analyzed from well cuttings, core, gas hydrate, and formation tests at the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well, drilled within the Milne Point Unit, Alaska North Slope. The well penetrated a portion of the Eileen gas hydrate deposit, which overlies the more deeply buried Prudhoe Bay, Milne Point, West Sak, and Kuparuk River oil fields. Gas sources in the upper 200 m are predominantly from microbial sources (C1 isotopic compositions ranging from −86.4 to −80.6‰). The C1 isotopic composition becomes progressively enriched from 200 m to the top of the gas hydrate-bearing sands at 600 m. The tested gas hydrates occur in two primary intervals, units D and C, between 614.0 m and 664.7 m, containing a total of 29.3 m of gas hydrate-bearing sands. The hydrocarbon gases in cuttings and core samples from 604 to 914 m are composed of methane with very little ethane. The isotopic composition of the methane carbon ranges from −50.1 to −43.9‰ with several outliers, generally decreasing with depth. Gas samples collected by the Modular Formation Dynamics Testing (MDT) tool in the hydrate-bearing units were similarly composed mainly of methane, with up to 284 ppm ethane. The methane isotopic composition ranged from −48.2 to −48.0‰ in the C sand and from −48.4 to −46.6‰ in the D sand. Methane hydrogen isotopic composition ranged from −238 to −230‰, with slightly more depleted values in the deeper C sand. These results are consistent with the concept that the Eileen gas hydrates contain a mixture of deep-sourced, microbially biodegraded thermogenic gas, with lesser amounts of thermogenic oil-associated gas, and coal gas. Thermal gases are likely sourced from existing oil and gas accumulations that have migrated up-dip and/or up-fault and formed gas hydrate in response to climate cooling with permafrost formation.

Visualization and simulation of density driven convection in porous media using magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Montague, James A.; Pinder, George F.; Gonyea, Jay V.; Hipko, Scott; Watts, Richard

2018-05-01

Magnetic resonance imaging is used to observe solute transport in a 40 cm long, 26 cm diameter sand column that contained a central core of low permeability silica surrounded by higher permeability well-sorted sand. Low concentrations (2.9 g/L) of Magnevist, a gadolinium based contrast agent, produce density driven convection within the column when it starts in an unstable state. The unstable state, for this experiment, exists when higher density contrast agent is present above the lower density water. We implement a numerical model in OpenFOAM to reproduce the observed fluid flow and transport from a density difference of 0.3%. The experimental results demonstrate the usefulness of magnetic resonance imaging in observing three-dimensional gravity-driven convective-dispersive transport behaviors in medium scale experiments.

Petrography, mineralogy, and geochemistry of deep gravelly sands in the Eyreville B core, Chesapeake Bay impact structure

USGS Publications Warehouse

Bartosova, Katerina; Gier, Susanne; Horton, J. Wright; Koeberl, Christian; Mader, Dieter; Dypvik, Henning

2010-01-01

The ICDP–USGS Eyreville drill cores in the Chesapeake Bay impact structure reached a total depth of 1766 m and comprise (from the bottom upwards) basement-derived schists and granites/pegmatites, impact breccias, mostly poorly lithified gravelly sand and crystalline blocks, a granitic slab, sedimentary breccias, and postimpact sediments. The gravelly sand and crystalline block section forms an approximately 26 m thick interval that includes an amphibolite block and boulders of cataclastic gneiss and suevite. Three gravelly sands (basal, middle, and upper) are distinguished within this interval. The gravelly sands are poorly sorted, clast supported, and generally massive, but crude size-sorting and subtle, discontinuous layers occur locally. Quartz and K-feldspar are the main sand-size minerals and smectite and kaolinite are the principal clay minerals. Other mineral grains occur only in accessory amounts and lithic clasts are sparse (only a few vol%). The gravelly sands are silica rich (~80 wt% SiO2). Trends with depth include a slight decrease in SiO2 and slight increase in Fe2O3. The basal gravelly sand (below the cataclasite boulder) has a lower SiO2 content, less K-feldspar, and more mica than the higher sands, and it contains more lithic clasts and melt particles that are probably reworked from the underlying suevite. The middle gravelly sand (below the amphibolite block) is finer-grained, contains more abundant clay minerals, and displays more variable chemical compositions than upper gravelly sand (above the block). Our mineralogical and geochemical results suggest that the gravelly sands are avalanche deposits derived probably from the nonmarine Potomac Formation in the lower part of the target sediment layer, in contrast to polymict diamictons higher in the core that have been interpreted as ocean-resurge debris flows, which is in agreement with previous interpretations. The mineralogy and geochemistry of the gravelly sands are typical for a passive continental margin source. There is no discernible mixing with marine sediments (no glauconite or Paleogene marine microfossils noted) during the impact remobilization and redeposition. The unshocked amphibolite block and cataclasite boulder might have originated from the outer parts of the transient crater.

Linking two thousand years of European historical records with environmental change recorded in a high Alpine ice core

NASA Astrophysics Data System (ADS)

Bohleber, Pascal; Spaulding, Nicole; Mayewski, Paul; Kurbatov, Andrei; Hoffmann, Helene; Erhardt, Tobias; Fischer, Hubertus; More, Alexander; Loveluck, Christopher; Luongo, Matthew; Kabala, Jakub; McCormick, Michael

2016-04-01

Its extraordinary network of historical and archaeological records makes Europe exceptionally promising for investigating environmental change and human response over the last two thousand years. Among natural proxy archives, ice core records offer a wide range of environmental reconstructions including natural and human source histories of the chemistry of the atmosphere. To link these robust environmental records with historical evidence of past civilizations remains a great challenge, however. In central Europe the unique target for a comparison for environmental change recorded in ice cores and human activity is the small firn saddle of Colle Gnifetti (4550 m above sea level on the Italian-Swiss border). Its exceptionally low net accumulation make Colle Gnifetti (CG) the only feasible site in the Alps for retrieving a long-term ice core record beyond the last century. However, at CG rapid annual layer thinning eventually limits conventional cm-resolution analysis to multi-annual signals and hampers dating by annual layer counting beyond a few hundred years. Thereby, a crucial gap is introduced to the sub-seasonal time scale of events typically recorded in written archives. In our ongoing project we pioneer correlating the CG environmental ice core archive with a unique compilation of European historical records provided through the Harvard Initiative for the Science of the Human Past and the Digital Atlas of Roman and Medieval Civilization. For this purpose, state-of-the-art glacio-chemical analysis was performed on a newly recovered CG ice core, including continuous flow analysis chemistry and stable isotopes. A crucial contribution comes from the application of LA-ICP-MS (laser ablation ion coupled plasma mass spectrometry) to meter long sections of frozen ice samples, developed and operated by the University of Maine's Climate Change Institute, offering glacio-chemical records up to 100 μm in resolution. The new methods significantly improves sampling resolution and allows detection of annual layers even in highly compressed old sections of CG ice cores: A breakthrough not only for extending the ice core dating over the last two millennia but also for bridging the gap in time scales to historical records. Here we present first results from our ongoing efforts in bringing together ice core time series with historical evidence, focusing on the time period from 1 to 1400 C.E. Based on a thorough consideration of the glaciological constraints at CG we explore various ice core proxy signals for their significance to correlate with events recorded in human writing, such as dust storms, volcanic events, climate-induced crop failures and starvation as well as metal production levels. Distinct dust layers are frequently found in CG ice cores, representative for meteorological conditions that transported sand from the Sahara to Europe. At the same time, Saharan dust events were also frequently recorded by ancient and medieval observers as "blood rain". Ultimately we work towards using past extreme climate events from medieval Europe recorded as written evidence to constrain the ice core age scale and, vice versa, to investigate the response of human societies to environmental change recorded in the CG glacier archive.

A new method of evaluating tight gas sands pore structure from nuclear magnetic resonance (NMR) logs

NASA Astrophysics Data System (ADS)

Xiao, Liang; Mao, Zhi-qiang; Xie, Xiu-hong

2016-04-01

Tight gas sands always display such characteristics of ultra-low porosity, permeability, high irreducible water, low resistivity contrast, complicated pore structure and strong heterogeneity, these make that the conventional methods are invalid. Many effective gas bearing formations are considered as dry zones or water saturated layers, and cannot be identified and exploited. To improve tight gas sands evaluation, the best method is quantitative characterizing rock pore structure. The mercury injection capillary pressure (MICP) curves are advantageous in predicting formation pore structure. However, the MICP experimental measurements are limited due to the environment and economy factors, this leads formation pore structure cannot be consecutively evaluated. Nuclear magnetic resonance (NMR) logs are considered to be promising in evaluating rock pore structure. Generally, to consecutively quantitatively evaluate tight gas sands pore structure, the best method is constructing pseudo Pc curves from NMR logs. In this paper, based on the analysis of lab experimental results for 20 core samples, which were drilled from tight gas sandstone reservoirs of Sichuan basin, and simultaneously applied for lab MICP and NMR measurements, the relationships of piecewise power function between nuclear magnetic resonance (NMR) transverse relaxation T2 time and pore-throat radius Rc are established. A novel method, which is used to transform NMR reverse cumulative curve as pseudo capillary pressure (Pc) curve is proposed, and the corresponding model is established based on formation classification. By using this model, formation pseudo Pc curves can be consecutively synthesized. The pore throat radius distribution, and pore structure evaluation parameters, such as the average pore throat radius (Rm), the threshold pressure (Pd), the maximum pore throat radius (Rmax) and so on, can also be precisely extracted. After this method is extended into field applications, several tight gas sandstone reservoirs are processed, and the predicted results are compared with core derived results. Good consistency between evaluated results with core derived results illustrates the dependability of the proposed method. Comparing with the previous methods, this presented model is much more theoretical, and the applicability is much improved. Combining with the evaluated results, our target tight gas sands are well evaluated, and many potential gas-bearing layers are effectively identified.

On Mellitella stokesii and Amphipholis geminata (Echinodermata), from an intertidal flat in the upper Gulf of Nicoya estuary, Pacific, Costa Rica.

PubMed

Vargas, José A; Solano, Sylvia

2011-03-01

Information on changes over time in the biodiversity and ecology of tropical systems is of increasing importance against the background of local, regional, and global dynamics. This study aimed to contribute with long-term data on the abundance fluctuations of two species of echinoderms from a tropical tidal flat. From February 1984 to December 1986, March 1985 to April 1987, and July 1994 to September 1996 (total: 76 dates), core samples (17.7 cm2, 15 cm deep) were collected at low tide at a mud-sand flat in the mid upper Gulf of Nicoya estuary, Costa Rica, as part of a survey of the benthic community. Among more than 100 taxa, the burrowing brittle star, Amphipholis geminata, and the sand dollar, Mellitella stokesii, consistently appeared in the samples over the study period. A total of 63 M. stokesii and 149 A. geminata were collected. The 43 sand dollars found during 1984-1985, give an approximate density of 35 ind./m2, which is within the range reported for this species. M. stokesii was almost absent from 1994 to 1996, while A. geminata had its peak of abundance at the end of 1995. Low abundances of the sand dollar during the rainy seasons (May-November) and slight increments in dry seasons (December-April) cores, also agrees with a report from the region. A. geminata also presented an irregular pattern of abundance, with slight increases at the end of the rainy seasons or during the dry seasons, when higher salinities are more suitable for echinoderms. The patchy spatial distribution of both species makes difficult the detection of patterns with a corer. Nevertheless, this information is unique due to its extensive time coverage and provides a baseline for future surveys designed specifically for the study of tropical intertidal estuarine echinoderms.

Evaluation of beach grooming techniques on Escherichia coli density in foreshore sand at North Beach, Racine, WI

USGS Publications Warehouse

Kinzelman, Julie L.; Whitman, Richard L.; Byappanahalli, Muruleedhara N.; Jackson, Emma; Bagley, Robert C.

2003-01-01

Elevated levels of Escherichia coli(E. coli) in bathing waters at North Beach, a popular recreational site in Racine, Wisconsin, have been a persistent problem often resulting in the issuance of poor water quality advisories. Moreover, waterfowl (mostly Larus delawarensis and L. argentatus) in nearshore and offshore areas are common and may serve as non-point sources for bacterial contamination of recreational waters. Current beach management practice involves daily mechanical grooming of the nearshore sand for aesthetics and removal of hazardous debris. However, this practice has not been evaluated in terms of its effects on E. coli loading to beach sand and potential introduction to contiguous swimming water. In this study, we tested E. coli responses to three treatments: mechanical groomer, daily and twice weekly hand raking, and a control (no raking/grooming). A randomized block design consisted of replicated treatments and one control (10 each), for a total of 40 blocks sampled daily for 10 days. Foreshore sand samples were collected by hand coring to an average depth of 10 cm. Median E. colirecovered were 73 (mechanically groomed), 27 (hand-raked daily), 32 (hand-raked twice weekly), and 22 (control) colony-forming units (CFU) per gram dry weight sand. E. colicounts in sand that was groomed were significantly higher than hand rakings and control (p <0.0001), and there was no significant difference between control and raking treatments (p<0.01). This study demonstrates the beach management implications related to grooming efficacy and the importance of understanding non-point sources of bacterial contamination.

Initial Observations and Activities of Curiosity's Mars Hand Lens Imager (MAHLI) at the Gale Field Site

NASA Astrophysics Data System (ADS)

Aileen Yingst, R.; Edgett, Kenneth; MSL Science Team

2013-04-01

The Mars Hand Lens Imager (MAHLI) is a 2-megapixel focusable macro lens color camera on the turret on the Mars Science Laboratory rover, Curiosity's, robotic arm. The investigation centers on stratigraphy, grain-scale texture, structure, mineralogy, and morphology. MAHLI acquires focused images at working distances of 2.1 cm to infinity; at 2.1 cm the scale is 14 µm/pixel; at 6.9 cm it is 31 µm/pixel, like the Spirit and Opportunity Microscopic Imagers (MI). Most MAHLI use during the first 100 Martian days (sols) was focused on instrument, rover, and robotic arm engineering check-outs and risk reduction, including (1) interrogation of an eolian sand shadow for suitability for scooping, decontamination of the sample collection and processing system (CHIMRA, Collection and Handling for In-Situ Martian Rock Analysis), and first solid sample delivery to the Chemistry and Mineralogy (CheMin) and Sample Analysis at Mars (SAM) instruments; (2) documentation of the nature of this sand; (3) verification that samples were delivered to SAM and passed through a 150 µm mesh and a 2 mm funnel throat in the CheMin inlet; (4) development of methods for future precision robotic arm positioning of MAHLI and the Alpha Particle X-Ray Spectrometer (APXS); and (5) use of MAHLI autofocus for range-finding to determine locations to position the scoop before each scooping event. Most Sol 0-100 MAHLI images were obtained at scales of 31-110 µm/pixel; some geologic targets were imaged at 21-31 µm/pixel. No opportunities to position the camera close enough to obtain 14-20 µm/pixel images were available during this initial period. Only two rocks, named Jake Matijevic and Bathurst Inlet, were imaged at a resolution higher than MI. Both were dark gray and mantled with dust and fine/very fine sand. In both cases, the highest resolution images of these rocks show no obvious, indisputable grains, suggesting that grain sizes (as expressed at the rock surfaces) are < 80 µm. However, because of the dust and sand obscuration, the observables are unclear —grains 300-500 µm size in the Bathurst Inlet images and 300-500 µm-sized rhombus-shaped crystals in the rock, Jake Matijevic have been observed by some workers. Sand and granules (as well as dust), exhibiting a variety of colors, shapes, and other grain attributes, were deposited on rover hardware during descent. As noted above, sand as well as dust also mantles the rocks observed by MAHLI; in one case the cohesive properties of this material was demonstrated by the presence of a "micro landslide" on a rock named Burwash. At the Rocknest sand shadow, a variety of coarse to very coarse sand grains of differing color, shape, luster, angularity, and roundness were observed, including glassy spheroids and ellipsoids (perhaps formed from impact melt droplets) and clear, translucent grains. The fine to very fine sands sieved (≤ 150 µm) and delivered to the rover's observation tray exhibited at least four distinct grain types, including clear, translucent crystal fragments.

Multi-field plasma sandpile model in tokamaks and applications

NASA Astrophysics Data System (ADS)

Peng, X. D.; Xu, J. Q.

2016-08-01

A multi-field sandpile model of tokamak plasmas is formulated for the first time to simulate the dynamic process with interaction between avalanche events on the fast/micro time-scale and diffusive transports on the slow/macro time-scale. The main characteristics of the model are that both particle and energy avalanches of sand grains are taken into account simultaneously. New redistribution rules of a sand-relaxing process are defined according to the transport properties of special turbulence which allows the uphill particle transport. Applying the model, we first simulate the steady-state plasma profile self-sustained by drift wave turbulences in the Ohmic discharge of a tokamak. A scaling law as f = a q0 b + c for the relation of both center-density n ( 0 ) and electron (ion) temperatures T e ( 0 ) ( T i ( 0 ) ) with the center-safety-factor q 0 is found. Then interesting work about the nonlocal transport phenomenon observed in tokamak experiments proceeds. It is found that the core electron temperature increases rapidly in response to the edge cold pulse and inversely it decreases in response to the edge heat pulse. The results show that the nonlocal response of core electron temperature depending on the amplitudes of background plasma density and temperature is more remarkable in a range of gas injection rate. Analyses indicate that the avalanche transport caused by plasma drift instabilities with thresholds is a possible physical mechanism for the nonlocal transport in tokamaks. It is believed that the model is capable of being applied to more extensive questions occurring in the transport field.

Lunar and Meteorite Thin Sections for Undergraduate and Graduate Studies

NASA Technical Reports Server (NTRS)

Allen, J.; Galindo, C.; Luckey, M.; Reustle, J.; Todd, N.; Allen, C.

2012-01-01

The Johnson Space Center (JSC) has the unique responsibility to curate NASA's extraterrestrial samples from past and future missions. Curation includes documentation, preservation, preparation, and distribution of samples for research, education, and public outreach. Between 1969 and 1972 six Apollo missions brought back 382 kilograms of lunar rocks, core samples, pebbles, sand and dust from the lunar surface. JSC also curates meteorites collected on US expeditions to Antarctica including rocks from Moon, Mars, and many asteroids including Vesta. Studies of rock and soil samples from the Moon and meteorites continue to yield useful information about the early history of the Moon, the Earth, and the inner solar system.

A long record of extreme wave events in coastal Lake Hamana, Japan

NASA Astrophysics Data System (ADS)

Boes, Evelien; Yokoyama, Yusuke; Schmidt, Sabine; Riedesel, Svenja; Fujiwara, Osamu; Nakamura, Atsunori; Garrett, Ed; Heyvaert, Vanessa; Brückner, Helmut; De Batist, Marc

2017-04-01

Coastal Lake Hamana is located near the convergent tectonic boundary of the Nankai-Suruga Trough, along which the Philippine Sea slab is subducted underneath the Eurasian Plate, giving rise to repeated tsunamigenic megathrust earthquakes (Mw ≥ 8). A good understanding of the earthquake- and tsunami-triggering mechanisms is crucial in order to better estimate the complexity of seismic risks. Thanks to its accommodation space, Lake Hamana may represent a good archive for past events, such as tsunamis and tropical storms (typhoons), also referred to as "extreme wave" events. Characteristic event layers, consisting of sediment entrained by these extreme waves and their backwash, are witnesses of past marine incursions. By applying a broad range of surveying methods (reflection-seismic profiling, gravity coring, piston coring), sedimentological analyses (CT-scanning, XRF-scanning, multi-sensor core logging, grain size, microfossils etc.) and dating techniques (210Pb/137Cs, 14C, OSL, tephrochronology), we attempt to trace extreme wave event deposits in a multiproxy approach. Seismic imagery shows a vertical stacking of stronger reflectors, interpreted to be coarser-grained sheets deposited by highly energetic waves. Systematic sampling of lake bottom sediments along a transect from ocean-proximal to ocean-distal sites enables us to evaluate vertical and lateral changes in stratigraphy. Ocean-proximal, we observe a sequence of eight sandy units separated by silty background sediments, up to a depth of 8 m into the lake bottom. These sand layers quickly thin out and become finer-grained land-inward. Seismic-to-core correlations show a good fit between the occurrence of strong reflectors and sandy deposits, hence confirming presumptions based on acoustic imagery alone. Sand-rich intervals typically display a higher magnetic susceptibility, density and stronger X-ray attenuation. However, based on textural and structural differences, we can make the distinction between different types of sand units: i) massive to layered sands with a sharp, erosive lower contact, ii) thin, discontinuous sand lenses with a sharp lower contact and iii) inter-fingered sand-rich and silt-rich intervals with a gradual lower contact. Variability in appearance suggests a variety in triggering events too, going from tsunamis, over storm surges (typhoons) to the impact of sea-level changes on the interaction between tidal delta and lacustrine sedimentation. Preliminary dating (210Pb/137Cs) results in sedimentation rates of 0.4 cm/yr for the last 100-150 yr. Two closely-spaced tephra layers are tentatively linked with the reported Osawa Fuji scoria (3090 BP) and Kawago-daira pumice (3150 BP). However, more absolute ages (14C and OSL) are essential in order to obtain an accurate age-depth model and to position events in time. We are proceeding with the age determination of event sand beds based on single-grain OSL dating of feldspars. Whereas quartz appeared to be not suitable for dating, research in onshore archives close to Lake Hamana already proved the suitability of the IRSL50 signal of feldspar.

Combined use of field and laboratory testing to predict preferred flow paths in an heterogeneous aquifer.

PubMed

Gierczak, R F D; Devlin, J F; Rudolph, D L

2006-01-05

Elevated nitrate concentrations within a municipal water supply aquifer led to pilot testing of a field-scale, in situ denitrification technology based on carbon substrate injections. In advance of the pilot test, detailed characterization of the site was undertaken. The aquifer consisted of complex, discontinuous and interstratified silt, sand and gravel units, similar to other well studied aquifers of glaciofluvial origin, 15-40 m deep. Laboratory and field tests, including a conservative tracer test, a pumping test, a borehole flowmeter test, grain-size analysis of drill cuttings and core material, and permeameter testing performed on core samples, were performed on the most productive depth range (27-40 m), and the results were compared. The velocity profiles derived from the tracer tests served as the basis for comparison with other methods. The spatial variation in K, based on grain-size analysis, using the Hazen method, were poorly correlated with the breakthrough data. Trends in relative hydraulic conductivity (K/K(avg)) from permeameter testing compared somewhat better. However, the trends in transient drawdown with depth, measured in multilevel sampling points, corresponded particularly well with those of solute mass flux. Estimates of absolute K, based on standard pumping test analysis of the multilevel drawdown data, were inversely correlated with the tracer test data. The inverse nature of the correlation was attributed to assumptions in the transient drawdown packages that were inconsistent with the variable diffusivities encountered at the scale of the measurements. Collectively, the data showed that despite a relatively low variability in K within the aquifer under study (within a factor of 3), water and solute mass fluxes were concentrated in discrete intervals that could be targeted for later bioremediation.

Nitrate transport and transformation processes in unsaturated porous media

USGS Publications Warehouse

Tindall, James A.; Petrusak, Robin L.; McMahon, Peter B.

1995-01-01

A series of experiments was conducted on two contrasting agricultural soils to observe the influence of soil texture, preferential flow, and plants on nitrate transport and denitrification under unsaturated conditions. Calcium nitrate fertilizer was applied to the surface of four large undisturbed soil cores (30 cm diameter by 40 cm height). Two of the cores were a structured clay obtained from central Missouri and two were an unstructured fine sand obtained from central Florida. The cores were irrigated daily and maintained at a matric potential of -20 kPa, representative of soil tension in the rooting zone of irrigated agricultural fields. Volumetric water content (θ), concentration of nitrate-N in the soil solution, and nitrous oxide flux at the surface, 10, 20, and 30 cm were monitored daily. Leaching loss of surface-applied N03− -N was significant in both the sand and the clay. In unplanted sand cores, almost all of the applied nitrate was leached below 30 cm within 10 days. Gaseous N loss owing to denitrification was no greater than 2% of the nitrate-N applied to the unplanted sand cores and, in general, was less than 1 %. Although leaching was somewhat retarded in the clay cores, about 60% of the applied nitrate-N was leached from the unplanted clay soil in 5–6 weeks. Under unsaturated conditions, the clay had little to no tendency to denitrify despite the greater moisture content of the clay and retarded leaching of nitrate in the clay. The planted sand cores had surprisingly large gaseous N loss owing to denitrification, as much as 17% of the nitrate-N. Results from both the clay and sand experiments show that the dynamics of nitrate transport and transformation in unsaturated soils are affected by small, localized variations in the soil moisture content profile, the gaseous diffusion coefficient of the soil, the rate at which the nitrate pulse passes through the soil, the solubility of N2O and N2 and the diffusion of the gasses through the soil solution, and development of a water content profile in the soil. Limited dentrification in the clay soil was due to a limited volume of soil available for infiltration after internal catchment and the development of denitrifying conditions resulting from the presence of an extensive macropore system.

Core Cutting Test with Vertical Rock Cutting Rig (VRCR)

NASA Astrophysics Data System (ADS)

Yasar, Serdar; Osman Yilmaz, Ali

2017-12-01

Roadheaders are frequently used machines in mining and tunnelling, and performance prediction of roadheaders is important for project economics and stability. Several methods were proposed so far for this purpose and, rock cutting tests are the best choice. Rock cutting tests are generally divided into two groups which are namely, full scale rock cutting tests and small scale rock cutting tests. These two tests have some superiorities and deficiencies over themselves. However, in many cases, where rock sampling becomes problematic, small scale rock cutting test (core cutting test) is preferred for performance prediction, since small block samples and core samples can be conducted to rock cutting testing. Common problem for rock cutting tests are that they can be found in very limited research centres. In this study, a new mobile rock cutting testing equipment, vertical rock cutting rig (VRCR) was introduced. Standard testing procedure was conducted on seven rock samples which were the part of a former study on cutting rocks with another small scale rock cutting test. Results showed that core cutting test can be realized successfully with VRCR with the validation of paired samples t-test.

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

Cipolla, C.L.; Mayerhofer, M.

The paper details the acquisition of detailed core and pressure data and the subsequent reservoir modeling in the Ozona Gas Field, Crockett County, Texas. The Canyon formation is the focus of the study and consists of complex turbidite sands characterized by numerous lenticular gas bearing members. The sands cannot be characterized using indirect measurements (logs) and no reliable porosity-permeability relationship could be developed. The reservoir simulation results illustrate the problems associated with interpreting typical pressure and production data in tight gas sands and details procedures to identify incremental reserves. Reservoir layering was represented by five model layers and layer permeabilitiesmore » were estimated based on statistical distributions from core measurements.« less

Visualization and simulation of density driven convection in porous media using magnetic resonance imaging.

PubMed

Montague, James A; Pinder, George F; Gonyea, Jay V; Hipko, Scott; Watts, Richard

2018-05-01

Magnetic resonance imaging is used to observe solute transport in a 40cm long, 26cm diameter sand column that contained a central core of low permeability silica surrounded by higher permeability well-sorted sand. Low concentrations (2.9g/L) of Magnevist, a gadolinium based contrast agent, produce density driven convection within the column when it starts in an unstable state. The unstable state, for this experiment, exists when higher density contrast agent is present above the lower density water. We implement a numerical model in OpenFOAM to reproduce the observed fluid flow and transport from a density difference of 0.3%. The experimental results demonstrate the usefulness of magnetic resonance imaging in observing three-dimensional gravity-driven convective-dispersive transport behaviors in medium scale experiments. Copyright © 2017 Elsevier B.V. All rights reserved.

Third-generation site characterization: Cryogenic core collection, nuclear magnetic resonance, and electrical resistivity

NASA Astrophysics Data System (ADS)

Kiaalhosseini, Saeed

In modern contaminant hydrology, management of contaminated sites requires a holistic characterization of subsurface conditions. Delineation of contaminant distribution in all phases (i.e., aqueous, non-aqueous liquid, sorbed, and gas), as well as associated biogeochemical processes in a complex heterogeneous subsurface, is central to selecting effective remedies. Arguably, a factor contributing to the lack of success of managing contaminated sites effectively has been the limitations of site characterization methods that rely on monitoring wells and grab sediment samples. The overarching objective of this research is to advance a set of third-generation (3G) site characterization methods to overcome shortcomings of current site characterization techniques. 3G methods include 1) cryogenic core collection (C3) from unconsolidated geological subsurface to improve recovery of sediments and preserving key attributes, 2) high-throughput analysis (HTA) of frozen core in the laboratory to provide high-resolution, depth discrete data of subsurface conditions and processes, 3) resolution of non-aqueous phase liquid (NAPL) distribution within the porous media using a nuclear magnetic resonance (NMR) method, and 4) application of a complex resistivity method to track NAPL depletion in shallow geological formation over time. A series of controlled experiments were conducted to develop the C 3 tools and methods. The critical aspects of C3 are downhole circulation of liquid nitrogen via a cooling system, the strategic use of thermal insulation to focus cooling into the core, and the use of back pressure to optimize cooling. The C3 methods were applied at two contaminated sites: 1) F.E. Warren (FEW) Air Force Base near Cheyenne, WY and 2) a former refinery in the western U.S. The results indicated that the rate of core collection using the C3 methods is on the order of 30 foot/day. The C3 methods also improve core recovery and limits potential biases associated with flowing sands. HTA of frozen core was employed at the former refinery and FEW. Porosity and fluid saturations (i.e., aqueous, non-aqueous liquid, and gas) from the former refinery indicate that given in situ freezing, the results are not biased by drainage of pore fluids from the core during sample collection. At FEW, a comparison between the results of HTA of the frozen core collected in 2014 and the results of site characterization using unfrozen core, (second-generation (2G) methods) at the same locations (performed in 2010) indicate consistently higher contaminant concentrations using C 3. Many factors contribute to the higher quantification of contaminant concentrations using C3. The most significant factor is the preservation of the sediment attributes, in particular, pore fluids and volatile organic compounds (VOCs) in comparison to the unfrozen conventional sediment core. The NMR study was performed on laboratory-fabricated sediment core to resolve NAPL distribution within the porous media qualitatively and quantitatively. The fabricated core consisted of Colorado silica sand saturated with deionized water and trichloroethylene (TCE). The cores were scanned with a BRUKER small-animal scanner (2.3 Tesla, 100 MHz) at 20 °C and while the core was frozen at -25 °C. The acquired images indicated that freezing the water within the core suppressed the NMR signals of water-bound hydrogen. The hydrogen associated with TCE was still detectable since the TCE was in its liquid state (melting point of TCE is -73 °C). Therefore, qualitative detection of TCE within the sediment core was performed via the NMR scanning by freezing the water. A one-dimensional NMR scanning method was used for quantification of TCE mass distribution within the frozen core. However, the results indicated inconsistency in estimating the total TCE mass within the porous media. Downhole NMR logging was performed at the former refinery in the western U.S. to detect NAPL and to discriminate NAPL from water in the formation. The results indicated that detection of NMR signals to discriminate NAPL from water is compromised by the noise stemming from the active facilities and/or power lines passing over the site. A laboratory experiment was performed to evaluate the electrical response of unconsolidated porous media through time (30 days) while NAPL was being depleted. Sand columns (Colorado silica sand) contaminated with methyl tert-butyl ether (MTBE, a light non-aqueous phase liquid (LNAPL)) were studied. A multilevel electrode system was used to measure electrical resistivity of impacted sand by imposing alternative current. The trend of reduction in resistivity through the depth of columns over time followed depletion of LNAPL by volatilization. Finally, a field experiment was performed at the former refinery in the western U.S. to track natural losses of LNAPL over time. Multilevel systems consisting of water samplers, thermocouples, and electrodes were installed at a clean zone (background zone) and an LNAPL-impacted zone. In situ measurements of complex resistivity and temperature were taken and water sampling was performed for each depth (from 3 to 14 feet below the ground surface at one-foot spacing) within almost a year. At both locations, the results indicated decreases in apparent resistivity below the water table over time. This trend was supported by the geochemistry of the pore fluids. Overall, results indicate that application of the electrical resistivity method to track LNAPL depletion at field sites is difficult due to multiple conflicting factors affecting the geoelectrical response of LNAPL-impacted zones over time.

Effects of bacterial pollution caused by a strong typhoon event and the restoration of a recreational beach: Transitions of fecal bacterial counts and bacterial flora in beach sand.

PubMed

Suzuki, Yoshihiro; Teranishi, Kotaro; Matsuwaki, Tomonori; Nukazawa, Kei; Ogura, Yoshitoshi

2018-05-28

To determine the effects of bacteria pollution associated with a strong typhoon event and to assess the restoration of the normal bacterial flora, we used conventional filtration methods and nextgeneration sequencing of 16S rRNA genes to analyze the transition of fecal and total bacterial counts in water and core sand samples collected from a recreational beach. Immediately after the typhoon event, Escherichia coli counts increased to 82 CFU/100 g in the surface beach sand. E. coli was detected through the surface to sand 85-cm deep at the land side point (10-m land side from the high-water line). However, E. coli disappeared within a month from the land side point. The composition of the bacterial flora in the beach sand at the land point was directly influenced by the typhoon event. Pseudomonas was the most prevalent genus throughout the sand layers (0-102-cm deep) during the typhoon event. After 3 months, the population of Pseudomonas significantly decreased, and the predominant genus in the surface layer was Kaistobacter, although Pseudomonas was the major genus in the 17- to 85-cm layer. When the beach conditions stabilized, the number of pollutant Pseudomonas among the 10 most abundant genera decreased to lower than the limit of detection. The bacterial population of the sand was subsequently restored to the most populous pre-event orders at the land point. A land-side beach, where users directly contact the sand, was significantly affected by bacterial pollution caused by a strong typhoon event. We show here that the normal bacterial flora of the surface sand was restored within 1 month. Copyright © 2018 Elsevier B.V. All rights reserved.

Provenance of sand on the Poverty Bay shelf, the link between source and sink sectors of the Waipaoa River sedimentary system

NASA Astrophysics Data System (ADS)

Parra, Julie G.; Marsaglia, Kathleen M.; Rivera, Kevin S.; Dawson, Shelby T.; Walsh, J. P.

2012-12-01

The Poverty Shelf, North Island, New Zealand, is a segment of the Waipaoa Sedimentary System (WSS), a MARGINS Source-to-Sink focus site. Our petrographic analysis of sand from shelf core samples indicates that the sand fraction is mainly derived from intra- and potentially extrabasinal sources, but surprisingly, the major fluvial system that drains into Poverty Bay, the Waipaoa River (mean %QFL = xQyFzL), is not the dominant source. Only one vibracore at the mouth of Poverty Bay contained sand (%QFL = xQyFzL) potentially derived from the Waipaoa River. The shelf sand (mean %QFL = xQyFzL) more strongly resembles beach sand (mean %QFL = xQyFzL) collected along the coast, which is likely sourced from pervasive local cliff erosion of Miocene-Pliocene sedimentary units that exhibit similar sandstone detrital modes (mean %QFL = xQyFzL). Texturally, coarser, more poorly sorted and more angular sand is located along the outer shelf, while finer, well-sorted sand characterizes the mid-shelf. These findings suggest a shorter transport history for the material near the outer-shelf bathymetric high areas, and this observation along with the composition data suggests that they were sourced by erosion of locally exposed Miocene-Pliocene units. A potential extrabasinal source of shelf sediment is indicated by anomalous prolate and equant-shaped greywacke (Torlesse) and minor red chert pebbles collected in two outer-shelf box cores on the Lachlan anticline; these are not lithologies found within the terrestrial segment of the WSS or strata comprising the outer-shelf highs. The clast shapes are also distinctly different from the oblate-shaped, pebble-sized greywacke gravel clasts on beaches in Hawke Bay. Rather, these sediments are more similar to Torlesse stream gravel. Seismic and multibeam data support the possibility that during the most recent sea-level lowstand, the Hawke Bay fluvial system flowed into Poverty Canyon, bringing these unique gravels onto what is now the Poverty outer shelf. The presence of the Torlesse gravel is significant in that it highlights how the WSS was not a closed sedimentary system in the past, just as recent sedimentary research has shown in the case today.

Nanoscale Pore Imaging and Pore Scale Fluid Flow Modeling in Chalk

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

Tomutsa, Liviu; Silin, Dmitriy

2004-08-19

For many rocks of high economic interest such as chalk, diatomite, tight gas sands or coal, nanometer scale resolution is needed to resolve the 3D-pore structure, which controls the flow and trapping of fluids in the rocks. Such resolutions cannot be achieved with existing tomographic technologies. A new 3D imaging method, based on serial sectioning and using the Focused Ion Beam (FIB) technology has been developed. FIB allows for the milling of layers as thin as 10 nanometers by using accelerated Ga+ ions to sputter atoms from the sample surface. After each milling step, as a new surface is exposed,more » a 2D image of this surface is generated. Next, the 2D images are stacked to reconstruct the 3D pore or grain structure. Resolutions as high as 10 nm are achievable using such a technique. A new robust method of pore-scale fluid flow modeling has been developed and applied to sandstone and chalk samples. The method uses direct morphological analysis of the pore space to characterize the petrophysical properties of diverse formations. Not only petrophysical properties (porosity, permeability, relative permeability and capillary pressures) can be computed but also flow processes, such as those encountered in various IOR approaches, can be simulated. Petrophysical properties computed with the new method using the new FIB data will be presented. Present study is a part of the development of an Electronic Core Laboratory at LBNL/UCB.« less

Mineralogical Characterization of the Miocene Olcese Formation, Southern San Joaquin Valley, California

NASA Astrophysics Data System (ADS)

Lopez, K. A.; Baron, D.; Guo, J.; Woolford, J. M.

2016-12-01

The early to middle Miocene Olcese Formation in the southern San Joaquin Valley of California consists of shallow marine shelf sands in its lower and upper parts, and non-marine, frequently pumiceous sands in its middle part, and varies in thickness up to 1800 ft. There is little known as to the origin, nature, quantity, and distribution of clay minerals throughout the formation. This study examined 95 sidewall core samples from three wells, as well as 388 cutting samples from four wells and 12 samples from 3 outcrops. Well samples were from depths between 1,800 and 4,000 ft. Qualitative and quantitative mineralogy including clay minerals of the sidewall samples and selected cutting samples was determined by powder X-ray diffraction (XRD). XRD analyses were supplemented by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) and petrographic microscopy of selected samples. The main minerals of bulk samples include composite clay, quartz, potassium feldspar/plagioclase, calcite, and clinoptilolite. Content of composite clay varies between 17% and 51%. The clay-size fraction is predominantly composed of smectite, illite, kaolinite and chlorite with smectite being the most abundant. Smectite and clinoptilolite may be the alteration products of deeper burial of volcanic materials. The formation permeability could be significantly lowered by these authigenic minerals.

Hydrogeologic framework and simulation of ground-water flow and travel time in the shallow aquifer system in the area of Naval Support Activity Memphis, Millington, Tennessee

USGS Publications Warehouse

Robinson, James L.; Carmichael, John K.; Halford, Keith J.; Ladd, David E.

1997-01-01

Naval Support Activity (NSA) Memphis is a Department of the Navy facility located at the City of Millington, Tennessee, about 5 miles north of Memphis. Contaminants have been detected in surface-water, sediment, and ground-water samples collected at the facility. As part of the Installation Restoration Program, the Navy is considering remedial-action options to prevent or lessen the effect of ground-water contamination at the facility and to control the movement and discharge of contaminants. A numerical model of the ground-water-flow system in the area of NSA Memphis was constructed and calibrated so that quantifiable estimates could be made of ground-water-flow rates, direction, and time-of-travel. The sediments beneath NSA Memphis, to a depth of about 200 feet, form a shallow aquifer system. From youngest to oldest, the stratigraphic units that form the shallow aquifer system are alluvium, loess, fluvial deposits, and the Cockfield and Cook Mountain Formations. The shallow aquifer system is organized into five hydrogeologic units: (1) a confining unit composed of the relatively low permeability sediments of the upper alluvium and the loess; (2) the A1 aquifer comprising sand and gravel of the lower alluvium and the fluvial deposits, and sand lenses in the upper part of the preserved section of the Cockfield Formation; (3) a confining unit composed of clay and silt within the upper part of the Cockfield Formation; (4) the Cockfield aquifer comprising sand lenses within the lower part of the preserved section of the Cockfield Formation; and (5) a confining unit formed by low permeability sediments of the Cook Mountain Formation that composes the upper confining unit for the Memphis aquifer. Thicknesses of individual units vary considerably across the facility. Structural and depositional features that affect the occurrence of ground water in the shallow aquifer system include faulting, an erosional scarp, and 'windows' in the confining units. Underlying the shallow aquifer system is the Memphis aquifer, the primary source of water for NSA Memphis and the City of Memphis, Tennessee. Analyses of sediment cores, aquifer and well specific-capacity tests, and numerical modeling were used to estimate the hydraulic characteristics of units of the shallow aquifer system. The vertical hydraulic conductivity of core samples of the alluvium-loess confining unit ranged from about 8.5 x 10-5 to 1.6 x 10-2 feet per day, and the total porosity of the samples ranged from about 35 to 48 percent. The results of the aquifer test were used to estimate a horizontal hydraulic conductivity of about 5 feet per day for the alluvial-fluvial deposits aquifer. The total porosity of core samples of the alluvial-fluvial deposits aquifer ranged from about 22 to 39 percent. The vertical hydraulic conductivity of core samples of the Cockfield confining unit ranged from about 4.5 x 10-5 to 2.5 x 10-3 feet per day, and the total porosity ranged from about 41 to 55 percent. Well specific-capacity tests indicate that the horizontal hydraulic conductivity of sand units that compose the Cockfield aquifer range from about 0.5 to 3 feet per day. The vertical hydraulic conductivity of core samples of the Cook Mountain confining unit ranged from about 5.0 x 10-6 to 9.9 x 10-4 feet per day. Total porosity of core samples of the Cook Mountain confining unit ranged from about 30 to 42 percent. Ground-water flow and time-of-travel in the shallow aquifer system were simulated using the MODFLOW finite-difference model and the -particle-tracking program MODPATH. A three-layer, steady-state model of the shallow aquifer system was constructed and calibrated to the potentiometric surface of the A1 aquifer. Results of numerical modeling support the proposed conceptual hydrogeologic model of the shallow aquifer system. Ground-water time-of-travel in the A1 aquifer was simulated using an assumed effective porosity of 25 percent. Typical ground-water-flow velocities were on the or

Application of random seismic inversion method based on tectonic model in thin sand body research

NASA Astrophysics Data System (ADS)

Dianju, W.; Jianghai, L.; Qingkai, F.

2017-12-01

The oil and gas exploitation at Songliao Basin, Northeast China have already progressed to the period with high water production. The previous detailed reservoir description that based on seismic image, sediment core, borehole logging has great limitations in small scale structural interpretation and thin sand body characterization. Thus, precise guidance for petroleum exploration is badly in need of a more advanced method. To do so, we derived the method of random seismic inversion constrained by tectonic model.It can effectively improve the depicting ability of thin sand bodies, combining numerical simulation techniques, which can credibly reducing the blindness of reservoir analysis from the whole to the local and from the macroscopic to the microscopic. At the same time, this can reduce the limitations of the study under the constraints of different geological conditions of the reservoir, accomplish probably the exact estimation for the effective reservoir. Based on the research, this paper has optimized the regional effective reservoir evaluation and the productive location adjustment of applicability, combined with the practical exploration and development in Aonan oil field.

Geochronology of Mudflow Deposits on the Mississippi River Delta Front, Louisiana, USA

NASA Astrophysics Data System (ADS)

Keller, G. P.; Bentley, S. J.; Xu, K.; Georgiou, I. Y.; Miner, M. D.; Obelcz, J.; Maloney, J. M.

2016-02-01

Short multicores (<50cm) and longer gravity cores (up to 3m) were collected seaward of the Southwest Pass of the Mississippi River Delta (Gulf of Mexico) and were analyzed to assess the frequency, extent, and potential causes of submarine mass wasting events. Cores were analyzed for radionuclide activity, grain size, and density at 2cm resolution, with x-radiography for the whole core. Short-term sedimentation rates calculated from 7Be are 2-12cm/y, while longer-term accumulation from 210Pb are only 1.3-5.5cm/y. In most cores, 210Pb activity steadily decreases downcore without displaying a "stairstep" nature. However, six cores have layers of low 210Pb activity stratigraphically above layers with higher activity. In one long core from a mudflow gully, 210Pb steadily decreases for the upper 90cm before stabilizing for the remaining 130cm. Clay content generally ranges between 25-40% and sand ranges between 5-15% with silt making up the rest of each sample. Sedimentation rates derived from 210Pb in the short cores indicate that proximity to the river mouth has stronger influence than depositional environment (mudflow gully, depositional lobe, prodelta). This finding may be explained by rapid sedimentation rates coupled with a reduced tropical cyclone activity over the delta in the last seven years (2006-2013). The regions of decreased 210Pb activity may be evidence of scavenging effects of plume sedimentation because they do not correspond with decreases in clay fraction. The zone of homogenized activity below 90cm in the gully core occurs at a depth equivalent to 18 years, indicating mixing on a decadal scale, potentially from mudflows. These results may be explained by a lack of recent mass failures corresponding with lulls in tropical cyclone activity over the delta, preceded by a period of more active hurricane-driven mudflow activity.

Bacterial transport in heterogeneous porous media: Observations from laboratory experiments

NASA Astrophysics Data System (ADS)

Silliman, S. E.; Dunlap, R.; Fletcher, M.; Schneegurt, M. A.

2001-11-01

Transport of bacteria through heterogeneous porous media was investigated in small-scale columns packed with sand and in a tank designed to allow the hydraulic conductivity to vary as a two-dimensional, lognormally distributed, second-order stationary, exponentially correlated random field. The bacteria were Pseudomonas ftuorescens R8, a strain demonstrating appreciable attachment to surfaces, and strain Ml, a transposon mutant of strain R8 with reduced attachment ability. In bench top, sand-filled columns, transport was determined by measuring intensity of fluorescence of stained cells in the effluent or by measuring radiolabeled cells that were retained in the sand columns. Results demonstrated that strain Ml was transported more efficiently than strain R8 through columns packed with either a homogeneous silica sand or a more heterogeneous sand with iron oxide coatings. Two experiments conducted in the tank involved monitoring transport of bacteria to wells via sampling from wells and sample ports in the tank. Bacterial numbers were determined by direct plate count. At the end of the first experiment, the distribution of the bacteria in the sediment was determined by destructive sampling and plating. The two experiments produced bacterial breakthrough curves that were quite similar even though the similarity between the two porous media was limited to first- and second-order statistical moments. This result appears consistent with the concept of large-scale, average behavior such as has been observed for the transport of conservative chemical tracers. The transported bacteria arrived simultaneously with a conservative chemical tracer (although at significantly lower normalized concentration than the tracer). However, the bacterial breakthrough curves showed significant late time tailing. The concentrations of bacteria attached to the sediment surfaces showed considerably more spatial variation than did the concentrations of bacteria in the fluid phase. This contrast between behavior in the fluid phase and on the solids is consistent with field observations by other authors and initial modeling of these heterogeneous media.

Band gaps and localization of surface water waves over large-scale sand waves with random fluctuations

NASA Astrophysics Data System (ADS)

Zhang, Yu; Li, Yan; Shao, Hao; Zhong, Yaozhao; Zhang, Sai; Zhao, Zongxi

2012-06-01

Band structure and wave localization are investigated for sea surface water waves over large-scale sand wave topography. Sand wave height, sand wave width, water depth, and water width between adjacent sand waves have significant impact on band gaps. Random fluctuations of sand wave height, sand wave width, and water depth induce water wave localization. However, random water width produces a perfect transmission tunnel of water waves at a certain frequency so that localization does not occur no matter how large a disorder level is applied. Together with theoretical results, the field experimental observations in the Taiwan Bank suggest band gap and wave localization as the physical mechanism of sea surface water wave propagating over natural large-scale sand waves.

Drivers of small scale variability in soil-atmosphere fluxes of CH4, N2O and CO2 in a forest soil

NASA Astrophysics Data System (ADS)

Maier, Martin; Nicolai, Clara; Wheeler, Denis; Lang, Friedeike; Paulus, Sinikka

2016-04-01

Soil-atmosphere fluxes of CH4, N2O and CO2 can vary on different spatial scales, on large scales between ecosystems but also within apparently homogenous sites. While CO2 and CH4 consumption is rather evenly distibuted in well aerated soils, the production of N2O and CH4 seems to occur at hot spots that can be associated with anoxic or suboxic conditions. Small-scale variability in soil properties is well-known from field soil assesment, affecting also soil aeration and thus theoretically, greenhouse gas fluxes. In many cases different plant species are associated with different soil conditions and vegetation mapping should therefor combined with soil mapping. Our research objective was explaining the small scale variability of greenhouse gas fluxes in an apparently homogeneous 50 years old Scots Pine stand in a former riparian flood plain.We combined greenhouse gas measurements and soil physical lab measurments with field soil assessment and vegetation mapping. Measurements were conducted with at 60 points at a plot of 30 X 30 m at the Hartheim monitoring site (SW Germany). For greenhouse gas measurements a non-steady state chamber system and laser analyser, and a photoacoustic analyser were used. Our study shows that the well aerated site was a substantial sink for atmospheric CH4 (-2.4 nmol/m² s) and also a for N2O (-0.4 nmol/m² s), but less pronounced, whereas CO2 production was a magnitude larger (2.6 μmol/m² s). The spatial variability of the CH4 consumption of the soils could be explained by the variability of the soil gas diffusivity (measured in situ + using soil cores). Deviations of this clear trend were only observed at points where decomposing woody debris was directly under the litter layer. Soil texture ranged from gravel, coarse sand, fine sand to pure silt, with coarser texture having higher soil gas diffusivity. Changes in texture were rather abrupt at some positions or gradual at other positions, and were well reflected in the vegetation structure. On patches of gravel and coarse sand there was hardly any ground vegatation, and a shrublayer was found only at silty patches Our results indicate that a stratification and regionalisation approach based on vegetation structure and soil texture represents a promising tool for the adjustment of sampling designs for soil gas flux measurement. Acknowledgement This research was financially supported by the project DFG (MA 5826/2-1).

Sedimentology of cores recovered from the Canada Basin of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Edwards, B. D.; Saint-Ange, F.; Pohlman, J.; Higgins, J.; Mosher, D. C.; Lorenson, T. D.; Hart, P.

2011-12-01

Researchers from the United States and Canada are collaborating to understand the tectonic and sedimentary history of the Arctic Ocean between Canada and Alaska. As part of this on-going study, a joint US-Canadian ice breaker expedition operated in parts of the Canada Basin during August 2010. Occasional interruptions of the seismic data acquisition provided the ship time to collect gravity and piston cores at five sites-of-opportunity throughout the basin. High-resolution multibeam bathymetry and chirp sub-bottom profiler data collected immediately prior to coring reveal the fine-scale morphology of each site. Core photographs, X-ray radiographs, and physical property data support the following descriptions. Two piston cores were collected from the Beaufort Sea continental margin in a region of known bottom simulating reflectors (BSRs). Site 1 (2538 m water depth): This core recovered 5.72 m of gas-charged, gray sticky clay and silty-clay from an approximately 1100 m diameter, 130 m high conical mound overlying the crest of a buried anticline. Gas hydrate recovered in the core catcher combined with cracks and voids, methane and other hydrocarbon gasses, pyrite concretions, chemosynthetic clams, carbonate nodules, and soft carbonate masses indicate the likely upward migration of deep-seated fluids. Site 2 (1157 m water depth): This core, positioned 40 km upslope from the gas hydrate core, recovered 3 m of gray sticky silty clay and clayey silt near the base of an erosional scarp. Some voids and fracturing are apparent but carbonate masses and pyrite concretions are absent. Site 3 (3070 m water depth): This core from the top of a seamount discovered in 2009 in the north-central part of the Canada Basin recovered 4.94 m of sediment. More than 3 m of dark brown to yellowish brown, massive interbedded silty clays with sands and matrix-supported gravels (ice rafted debris [IRD]) occur in abrupt contact with underlying reddish yellow to brownish yellow silty clay and gravelly sandy clay interpreted to be altered hydrothermally. Successions of IRD layers create a thinly- to medium-bedded sequence throughout the lower section. Site 4 (3700 m water depth; central Canada Basin): This core recovered 3.4 m of sediment typified by decimeter-thick sequences of stacked graded beds with erosional basal contacts (Bouma sequences) characteristic of turbidite deposition. Site 5 (2081 m water depth; continental slope west of the Canadian archipelago): This core recovered 4.96 m of sediment of which the upper 2 m is silty clay to clayey silt with dispersed sand and granules. This upper section has an irregular, sharp basal contact with an underlying 16-cm-thick clast-supported massive gravel. The gravel has a scoured basal contact and overlies a monotonous gray clayey silt containing dispersed granules of IRD. Sparse and poorly preserved fauna throughout all the cores make age determination difficult; however, given the paucity of sediment cores in the Arctic Ocean, these samples provide vital geophysical groundtruth and sedimentological information about the basin.

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

USGS Publications Warehouse

Santamarina, J.C.; Dai, Shifeng; Terzariol, M.; Jang, Jeonghwan; Waite, William F.; Winters, William J.; Nagao, J.; Yoneda, J.; Konno, Y.; Fujii, T.; Suzuki, K.

2015-01-01

Natural hydrate-bearing sediments from the Nankai Trough, offshore Japan, were studied using the Pressure Core Characterization Tools (PCCTs) to obtain geomechanical, hydrological, electrical, and biological properties under in situ pressure, temperature, and restored effective stress conditions. Measurement results, combined with index-property data and analytical physics-based models, provide unique insight into hydrate-bearing sediments in situ. Tested cores contain some silty-sands, but are predominantly sandy- and clayey-silts. Hydrate saturations Sh range from 0.15 to 0.74, with significant concentrations in the silty-sands. Wave velocity and flexible-wall permeameter measurements on never-depressurized pressure-core sediments suggest hydrates in the coarser-grained zones, the silty-sands where Sh exceeds 0.4, contribute to soil-skeletal stability and are load-bearing. In the sandy- and clayey-silts, where Sh < 0.4, the state of effective stress and stress history are significant factors determining sediment stiffness. Controlled depressurization tests show that hydrate dissociation occurs too quickly to maintain thermodynamic equilibrium, and pressure–temperature conditions track the hydrate stability boundary in pure-water, rather than that in seawater, in spite of both the in situ pore water and the water used to maintain specimen pore pressure prior to dissociation being saline. Hydrate dissociation accompanied with fines migration caused up to 2.4% vertical strain contraction. The first-ever direct shear measurements on never-depressurized pressure-core specimens show hydrate-bearing sediments have higher sediment strength and peak friction angle than post-dissociation sediments, but the residual friction angle remains the same in both cases. Permeability measurements made before and after hydrate dissociation demonstrate that water permeability increases after dissociation, but the gain is limited by the transition from hydrate saturation before dissociation to gas saturation after dissociation. In a proof-of-concept study, sediment microbial communities were successfully extracted and stored under high-pressure, anoxic conditions. Depressurized samples of these extractions were incubated in air, where microbes exhibited temperature-dependent growth rates.

Numerical simulation of mud erosion rate in sand-mud alternate layer and comparison with experiment

NASA Astrophysics Data System (ADS)

Yoshida, T.; Yamaguchi, T.; Oyama, H.; Sato, T.

2015-12-01

For gas production from methane hydrates in sand-mud alternate layers, depressurization method is expected as feasible. After methane hydrate is dissociated, gas and water flow in pore space. There is a concern about the erosion of mud surface and it may result in flow blockage that disturbs the gas production. As a part of a Japanese National hydrate research program (MH21, funded by METI), we developed a numerical simulation of water-induced mud erosion in pore-scale sand-mud domains to model such mud erosion. The size of which is of the order of 100 micro meter. Water flow is simulated using a lattice Boltzmann method (LBM) and mud surface is treated as solid boundary with arbitrary shape, which changes with time. Periodic boundary condition is adopted at the domain boundaries, except for the surface of mud layers and the upper side. Shear stress acting on the mud surface is calculated using a momentum-exchange method. Mud layer is eroded when the shear stress exceeds a threshold coined a critical shear stress. In this study, we compared the simulated mud erosion rate with experimental data acquired from an experiment using artificial sand-mud core. As a result, the simulated erosion rate agrees well with that of the experiment.

Sediment composition and texture of Pleistocene deep-sea turbidites in the eastern Nankai Trough gas hydrate field

NASA Astrophysics Data System (ADS)

Egawa, K.; Nishimura, O.; Izumi, S.; Ito, T.; Konno, Y.; Yoneda, J.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

2013-12-01

In the 2012 JOGMEC/JAPEX pressure coring operation, we collected a totally 60-m-long core sample from the interval of gas hydrate concentration zone at the planned site of the world's first offshore production test of natural gas hydrates in the eastern Nankai Trough area. In this contribution, the cored sediments were sedimentologically, mineralogically, and paleontologically analyzed to know sediment composition and texture of reservoir formation, which are known to provide useful geological information to discuss sedimentation, diagenesis, and permeability. The targeted interval belongs to a Middle Pleistocene deep-sea turbidite sequence distributed around the Daini Atsumi Knoll, east of the Kumano forearc basin, and consists of the lower (thick sand-dominant), middle (thin-bedded sand-and-mud alteration), and upper (mud-dominant) formations in ascending order. X-ray powder diffraction analysis and scanning electron microscopic observation revealed that pore space in turbidite sands is commonly filled with clay fractions (mostly phyllosilicates) in the lower formation. Such a pore filling of clay fractions is reflected in particle size distribution showing high standard deviation and clay content, and thus is expected to have an impact on permeability. There is the older Pliocene to Early Pleistocene fossil coccolith record in the middle formation, indicating sediment reworking probably induced by submarine landslide. The coexistence of authigenic siderite and framboidal pyrite in the middle formation strongly suggests anoxic microbial activity under methane oxidation and sulfide reduction conditions at least before the hydrate cementation. This contribution was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI).

Low faunal diversity on Maltese sandy beaches: fact or artefact?

NASA Astrophysics Data System (ADS)

Deidun, Alan; Azzopardi, Marthese; Saliba, Stephen; Schembri, Patrick J.

2003-10-01

Eight sandy beaches on Malta and two on Gozo were sampled for macrofauna to test the hypothesis that Maltese beaches have an intrinsically low diversity. Stations distributed in the supralittoral (dry zone), mediolittoral (wet zone) and upper infralittoral (submerged zone to 1 m water depth) were sampled by sieving core samples and standardised searching during daytime, and pitfall trapping and standardised sweeping of the water column using a hand-net at night, as appropriate. Physical parameters of the sediment were measured and human occupancy of the beaches was estimated. From the supralittoral and mediolittoral, 39 species represented by 1584 individuals were collected by the combined techniques of pitfall trapping, sieving and standard searching. For Ramla beach, which had the highest diversity, 267 individuals representing 25 infaunal species were collected by sieving from a combined volume of 1.175 m 3 of sand, and 149 individuals representing 28 epifaunal species were collected by standardised searching from a combined area of 700 m 2 of sand during two winter and two summer sampling sessions between 1992 and 1993. For nine other beaches sampled during the summer of 2000, only six macrofaunal species were collected from core samples, with overall population densities ranging from 4.13 to 45.45 individuals m -2. Only 92 individuals belonging to 12 species were collected by hand-net from the uppermost infralittoral of five beaches sampled using this method during the summer of 2000. Taxa of gastropods, bivalves, decapods, mysids and staphylinid beetles generally abundant on Mediterranean sandy beaches, were entirely absent from the beaches sampled. Few correlations that could explain the impoverishment of Maltese sandy beaches were found between physical parameters and faunal abundances, and other factors such as inadequate sampling effort, human disturbance and marine pollution were also excluded; however, seasonally biased sampling may partly explain the results obtained. One factor that may explain why certain species are missing could be lack of recruitment, due to Malta's geographical isolation from the European and African mainlands.

Effects of core self-evaluations on the job burnout of nurses: the mediator of organizational commitment.

PubMed

Zhou, Yangen; Lu, Jiamei; Liu, Xianmin; Zhang, Pengcheng; Chen, Wuying

2014-01-01

To explore the impact of Core self-evaluations on job burnout of nurses, and especially to test and verify the mediator role of organizational commitment between the two variables. Random cluster sampling was used to pick up participants sample, which consisted of 445 nurses of a hospital in Shanghai. Core self-evaluations questionnaire, job burnout scale and organizational commitment scale were administrated to the study participants. There are significant relationships between Core self-evaluations and dimensions of job burnout and organizational commitment. There is a significant mediation effect of organizational commitment between Core self-evaluations and job burnout. To enhance nurses' Core self-evaluations can reduce the incidence of job burnout.

Reconstruction of paleostorm history using geochemical proxies in sediment cores from Eastern Lake, Florida

NASA Astrophysics Data System (ADS)

Das, O.; Wang, Y.; Donoghue, J. F.; Coor, J. L.; Kish, S.; Elsner, J.; Hu, X. B.; Niedoroda, A. W.; Ye, M.; Xu, Y.

2009-12-01

Analysis of geochemical proxies of coastal lake sediments provides a useful tool for reconstructing paleostorm history. Such paleostorm records can help constrain models that are used to predict future storm events. In this study, we collected two sediment cores (60 and 103 cm long, respectively) from the center of Eastern Lake located on the Gulf coast of NW Florida. These cores, which are mainly composed of organic-rich mud and organic-poor sand, were sub-sampled at 2-3mm intervals for analyses of their organic carbon and nitrogen concentrations as well as δ13C and δ15N isotopic signatures. Selected samples were submitted for radiocarbon dating in order to establish a chronological framework for the interpretation of the geochemical data. There are significant variations in δ13C, δ15N, C%, N% and C/N with depth. The δ13C and δ15N values vary from -21.8‰ to -26.7‰ and 2.6‰ to 5‰, respectively. The stable isotopic signatures of carbon and nitrogen indicate that the sources of organic matter in sediments include terrestrial C3 type vegetation, marine input from Gulf of Mexico and biological productivity within the lake, such as phytoplankton and zooplankton growing in the lacustrine environment. The δ13C and δ15N values exhibit significant negative excursions by 2‰ in a 30 cm thick sand layer, bounded by a rapid return to the base value. A positive shift in the δ15N record observed in the upper part of the cores likely reflects increased anthropogenic input of N such as sewage or septic tank effluents associated with recent development of areas around the lake for human habitation. Similarly, organic C% and N% range from 5.8 to 0.4 and 0.4 to 0.1, respectively. A prominent negative shift by 2σ relative to the baseline in C% and N% has been observed at approx. 55 to 58 cm depth, consisting of an organic-poor sand layer. This shift in C% and N% can be correlated with the negative shift in the δ13C and δ15N values, indicating a major storm event. Radiocarbon dates will allow establishment of the timing of the event and the interpretation of geochemical data in terms of changes in the lake environment.

Analysis of Monolith Cores from an Engineering Scale Demonstration of a Prospective Cast Stone Process

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

Crawford, C. L.; Cozzi, A. D.; Hill, K. A.

2016-06-01

The primary disposition path of Low Activity Waste (LAW) at the DOE Hanford Site is vitrification. A cementitious waste form is one of the alternatives being considered for the supplemental immobilization of the LAW that will not be treated by the primary vitrification facility. Washington River Protection Solutions (WRPS) has been directed to generate and collect data on cementitious or pozzolanic waste forms such as Cast Stone. This report documents the coring and leach testing of monolithic samples cored from an engineering-scale demonstration (ES Demo) with non-radioactive simulants. The ES Demo was performed at SRNL in October of 2013 usingmore » the Scaled Continuous Processing Facility (SCPF) to fill an 8.5 ft. diameter x 3.25 ft. high container with simulated Cast Stone grout. The Cast Stone formulation was chosen from the previous screening tests. Legacy salt solution from previous Hanford salt waste testing was adjusted to correspond to the average LAW composition generated from the Hanford Tank Waste Operation Simulator (HTWOS). The dry blend materials, ordinary portland cement (OPC), Class F fly ash, and ground granulated blast furnace slag (GGBFS or BFS), were obtained from Lafarge North America in Pasco, WA. In 2014 core samples originally obtained approximately six months after filling the ES Demo were tested along with bench scale molded samples that were collected during the original pour. A latter set of core samples were obtained in late March of 2015, eighteen months after completion of the original ES Demo. Core samples were obtained using a 2” diameter x 11” long coring bit. The ES Demo was sampled in three different regions consisting of an outer ring, a middle ring and an inner core zone. Cores from these three lateral zones were further segregated into upper, middle and lower vertical segments. Monolithic core samples were tested using the Environmental Protection Agency (EPA) Method 1315, which is designed to provide mass transfer rates (release rates) of inorganic analytes contained in monolithic material under diffusion controlled release conditions as a function of leaching time. Compressive strength measurements and drying tests were also performed on the 2015 samples. Leachability indices reported are based on analyte concentrations determined from dissolution of the dried samples.« less

34. DESPATCH CORE OVENS, GREY IRON FOUNDRY CORE ROOM, BAKES ...

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

34. DESPATCH CORE OVENS, GREY IRON FOUNDRY CORE ROOM, BAKES CORES THAT ARE NOT MADE ON HEATED OR COLD BOX CORE MACHINES, TO SET BINDING AGENTS MIXED WITH THE SAND CREATING CORES HARD ENOUGH TO WITHSTAND THE FLOW OF MOLTEN IRON INSIDE A MOLD. - Stockham Pipe & Fittings Company, Grey Iron Foundry, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

Core drilling provides information about Santa Fe Group aquifer system beneath Albuquerque's West Mesa

USGS Publications Warehouse

Allen, B.D.; Connell, S.D.; Hawley, J.W.; Stone, B.D.

1998-01-01

Core samples from the upper ???1500 ft of the Santa Fe Group in the Albuquerque West Mesa area provide a first-hand look at the sediments and at subsurface stratigraphic relationships in this important part of the basin-fill aquifer system. Two major hydrostratigraphic subunits consisting of a lower coarse-grained, sandy interval and an overlying fine-grained, interbedded silty sand and clay interval lie beneath the water table at the 98th St core hole. Borehole electrical conductivity measurements reproduce major textural changes observed in the recovered cores and support subsurface correlations of hydrostratigraphic units in the Santa Fe Group aquifer system based on geophysical logs. Comparison of electrical logs from the core hole and from nearby city wells reveals laterally consistent lithostratigraphic patterns over much of the metropolitan area west of the Rio Grande that may be used to delineate structural and related stratigraphic features that have a direct bearing on the availability of ground water.

Microbial community in a full-scale drinking water biosand filter.

PubMed

Feng, Shuo; Chen, Chao; Wang, Qingfeng; Yang, Zhiyu; Zhang, Xiaojian; Xie, Shuguang

2013-04-01

To remove turbidity and minimize microbiological risks, rapid sand filtration is one of main drinking water treatment processes in the world. However, after a long-term operation, sand particles will be colonized by microorganisms which can remove biodegradable organic matters and nitrogen compounds. In this study, 16S rRNA gene clone library analysis was applied to characterize the microbial community in a full-scale biosand filter used for drinking water treatment. The results indicate that phylum Nitrospirae and class Alphaproteobacteria were the dominant bacterial groups in the biosand sample collected from the upper filter layer. The dominance of Sphingomonas species might pose a microbiological risk. This work could provide some new insights into microbial community in drinking water biofilter.

Role of a large marine protected area for conserving landscape attributes of sand habitats on Georges Bank (NW Atlantic)

USGS Publications Warehouse

Lindholm, J.; Auster, P.; Valentine, P.

2004-01-01

Mobile fishing gear reduces seafloor habitat complexity through the removal of structure-building fauna, e.g. emergent organisms that create pits and burrows, as well as by smoothing of sedimentary bedforms (e.g. sand ripples). In this study, we compared the relative abundance of microhabitat features (the scale at which individual fish associate with seafloor habitat) inside and outside of a large fishery closed area (6917 km2) on Georges Bank. Starting in late 1994, the closed area excluded all bottom tending fishing gear capable of capturing demersal fishes. A total of 32 stations were selected inside and outside of the closed area in sand habitats. Video and still photographic transects were conducted at each station using the Seabed Observation and Sampling System (SEABOSS). Seven common (i.e. featureless sand, rippled sand, sand with emergent fauna, bare gravelly sand, gravelly sand with attached-erect fauna, whole shell, shell fragment) and 2 rare (sponges, biogenic depressions) microhabitat types were compared separately. Results showed significant differences in the relative abundance of the shell fragment and sponge microhabitat types between fished and unfished areas. The lack of differences for the other microhabitats may indicate that the level of fishing activity in the area is matched by the system's ability to recover.

U.S. Geological survey program on toxic waste--ground-water contamination; proceedings of the Second technical meeting, Cape Cod, Massachusetts, October 21-25, 1985

USGS Publications Warehouse

Ragone, S.E.

1988-01-01

This study characterizes the clay minerals in sediments associated with a plume of creosote-contaminated groundwater. The plume of contaminated groundwater near Pensacola, FL, is in shallow, permeable, Miocene to Holocene quartz sand and flows southward toward Pensacola Bay. Clay-size fractions were separated from 41 cores, chiefly split-spoon samples at 13 drill sites. The most striking feature of the chemical analyses of the clay fractions from uncontaminated site 2 and contaminated sites 4,5,6, and 7 is the variability of iron oxide (species in some samples as Fe2O3); total iron oxide abundance is lowest (2.5%) in uncontaminated sample 2-40, but is > 4.5% (4.5 to 8.5%) in the remaining assemblages. One feature suggesting interaction between the indigenous clays and the waste plume is the presence of nontronite-rich smectite. Nontronite commonly has been identified as the product of hydrothermal alteration and deep-sea weathering of submarine basalts; it is not a common constituent of Cenozoic Gulf Coast sediments. At the Pensacola site, relatively abundant nontronitic smectite is confined to contaminated sands or associated muds; it is least abundant or absent in sands and muds peripheral to the waste plume. The geochemistry of the waste plume, its substantial dissolved, (chiefly ferrous iron), mildly acidic (pH 5-6), and low redox composition, provides an environment similar to that previously determined for the low-temperature synthesis of nontronite. Data from clay-size fractions confirm conclusions that neoformed pyrite in some grain coatings occurs in an assemblage with excess iron over that required in the pyrite. Continuing studies to evaluate these tentative conclusions include: (1) chemical analysis of clay fractions from remaining sites to further examine the apparent relation between iron content and abundance of nontronitic smectite; (2) clay separation and analysis, and pore fluid extraction (squeezing or ultracentrifugation) and analysis from a continuous core through the mud lens to determine pore fluid composition (presence or absence of waste fluid), and character of associated clay minerals; and (3) clay separation and analysis in both permeable sands and the intervening mud lens that are clearly outside the limits of the waste plume to further document the effects of the plume. (See also W90-00022) (Lantz-PTT)

Numerical and experimental investigation of DNAPL removal mechanisms in a layered porous medium by means of soil vapor extraction.

PubMed

Yoon, Hongkyu; Oostrom, Mart; Wietsma, Thomas W; Werth, Charles J; Valocchi, Albert J

2009-10-13

The purpose of this work is to identify the mechanisms that govern the removal of carbon tetrachloride (CT) during soil vapor extraction (SVE) by comparing numerical and analytical model simulations with a detailed data set from a well-defined intermediate-scale flow cell experiment. The flow cell was packed with a fine-grained sand layer embedded in a coarse-grained sand matrix. A total of 499 mL CT was injected at the top of the flow cell and allowed to redistribute in the variably saturated system. A dual-energy gamma radiation system was used to determine the initial NAPL saturation profile in the fine-grained sand layer. Gas concentrations at the outlet of the flow cell and 15 sampling ports inside the flow cell were measured during subsequent CT removal using SVE. Results show that CT mass was removed quickly in coarse-grained sand, followed by a slow removal from the fine-grained sand layer. Consequently, effluent gas concentrations decreased quickly at first, and then started to decrease gradually, resulting in long-term tailing. The long-term tailing was mainly due to diffusion from the fine-grained sand layer to the coarse-grained sand zone. An analytical solution for a one-dimensional advection and a first-order mass transfer model matched the tailing well with two fitting parameters. Given detailed knowledge of the permeability field and initial CT distribution, we were also able to predict the effluent concentration tailing and gas concentration profiles at sampling ports using a numerical simulator assuming equilibrium CT evaporation. The numerical model predictions were accurate within the uncertainty of independently measured or literature derived parameters. This study demonstrates that proper numerical modeling of CT removal through SVE can be achieved using equilibrium evaporation of NAPL if detailed fine-scale knowledge of the CT distribution and physical heterogeneity is incorporated into the model. However, CT removal could also be fit by a first-order mass transfer analytical model, potentially leading to an erroneous conclusion that the long-term tailing in the experiment was kinetically controlled due to rate-limited NAPL evaporation.

Linking pore-scale and basin-scale effects on diffusive methane transport in hydrate bearing environments through multi-scale reservoir simulations

NASA Astrophysics Data System (ADS)

Nole, M.; Daigle, H.; Cook, A.; Malinverno, A.; Hillman, J. I. T.

2016-12-01

We explore the gas hydrate-generating capacity of diffusive methane transport induced by solubility gradients due to pore size contrasts in lithologically heterogeneous marine sediments. Through the use of 1D, 2D, and 3D reactive transport simulations, we investigate scale-dependent processes in diffusion-dominated gas hydrate systems. These simulations all track a sand body, or series of sands, surrounded by clays as they are buried through the gas hydrate stability zone. Methane is sourced by microbial methanogenesis in the clays surrounding the sand layers. In 1D, simulations performed in a Lagrangian reference frame demonstrate that gas hydrate in thin sands (3.6 m thick) can occur in high saturations (upward of 70%) at the edges of sand bodies within the upper 400 meters below the seafloor. Diffusion of methane toward the center of the sand layer depends on the concentration gradient within the sand: broader sand pore size distributions with smaller median pore sizes enhance diffusive action toward the sand's center. Incorporating downhole log- and laboratory-derived sand pore size distributions, gas hydrate saturations in the center of the sand can reach 20% of the hydrate saturations at the sand's edges. Furthermore, we show that hydrate-free zones exist immediately above and below the sand and are approximately 5 m thick, depending on the sand-clay solubility contrast. A moving reference frame is also adopted in 2D, and the angle of gravity is rotated relative to the grid system to simulate a dipping sand layer. This is important to minimize diffusive edge effects or numerical diffusion that might be associated with a dipping sand in an Eulerian grid system oriented orthogonal to gravity. Two-dimensional simulations demonstrate the tendency for gas hydrate to accumulate downdip in a sand body because of greater methane transport at depth due to larger sand-clay solubility contrasts. In 3D, basin-scale simulations illuminate how convergent sand layers in a multilayered system can compete for diffusion from clays between them, resulting in relatively low hydrate saturations. All simulations suggest that when hydrate present in clays dissociates with burial, the additional dissolved methane is soaked up by nearby sands preserving high hydrate saturations.

SPRUCE S1 Bog Pretreatment Fungal Hyphae Carbon and Nitrogen Concentrations and Stable Isotope Composition from In-growth Cores, 2013-2014

DOE Data Explorer

Hofmockel, K. S. [Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A.; Chen, J. [Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A.; Hobbie, E. A. [Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A.

2014-02-01

This data set reports fungal hyphal carbon and nitrogen concentrations and δ13C, and δ15N data for samples obtained from in-growth cores in the S1 Bog. Hyphae were collected using 40 μm in-growth bags (10 cm × 10 cm) filled with sterile sand. Bags were incubated in the field in paired hummock and hollows at six locations in the bog. In hummocks, bags were inserted at +10 to 0 cm above the adjacent hollow and in both locations from 0 to -10 cm and -10 to -20 cm below the hollow surface

Population dynamics of the sand shiner (notropis stramineus) in non-wadeable rivers of Iowa

USGS Publications Warehouse

Smith, C.D.; Neebling, T.E.; Quist, M.C.

2010-01-01

The sand shiner (Notropis stramineus) is a common cyprinid found throughout the Great Plains region of North America that plays an important ecological role in aquatic systems. This study was conducted to describe population dynamics of sand shiners including age structure, growth, mortality, and recruitment variability in 15 non-wadeable rivers in Iowa. Fish were collected during June-August (2007-2008) using a modified Missouri trawl, a seine, and boat-mounted electrofishing. Scales were removed for age and growth analysis. A total of 3,443 fish was sampled from 15 populations across Iowa, of which 676 were aged. Iowa's sand shiner populations consisted primarily of age-1 fish (53% of all fish sampled), followed by age-2 fish (30%), age-0 fish (15%), and age-3 fish (2%). Sand shiners grew an average of 38.5 mm (SE = 5.7) during their first year, 13.8 mm (4.5) during their second year, and 9.0 mm (6.9) during their third year. Total annual mortality varied from 35.0% to 92.3% among populations with a mean of 77.9% (0.2). Incremental mortality rates were 84.5% (0.2) between age 1 and age 2, and 92.0% (0.1) between age 2 and age 3. Recruitment was highly variable, as indicated by a mean recruitment variation index of-0.12 (0.54). Overall, the sand shiner was characterized by relatively low mean age, fast growth, high mortality, and high recruitment variability. Indices of sand shiner population dynamics were poorly correlated with habitat characteristics.

The Effect of Heating During In Situ Remediation on the Dynamics and Activity of Soil Microorganisms

DTIC Science & Technology

2000-10-01

understanding the microbial ecology at the lab-scale. Experiments were performed in three insulated boxes (0.5 m x 0.5 m x 0.1 m) containing medium sand...Lexan® boxes (0.5 m H x 0.5 m W X 0. 1 m H) containing soil from the Piedmont region of North Carolina (Medium sand). Nine soil sampling ports were...Soil Vapor Extraction (SVE) system operates on the principle that organic hydrocarbons contained in contaminated sites can volatize at temperatures

Diversity patterns, Leishmania DNA detection, and bloodmeal identification of Phlebotominae sand flies in villages in northern Colombia

PubMed Central

León, Cielo; Paz, Andrea; López, Marla; Molina, Gisell; Toro, Diana; Ortiz, Mario; Cordovez, Juan Manuel; Atencia, María Claudia; Aguilera, Germán; Tovar, Catalina

2018-01-01

Leishmaniases are neglected tropical diseases exhibiting complex transmission cycles due to the number of parasite species circulating, sand fly species acting as vectors and infected mammals, including humans, which are defined in the New World as accidental hosts. However, current transmission scenarios are changing, and the disease is no longer exclusively related to forested areas but urban transmission foci occur, involving some species of domestic animals as suspected reservoirs. The aim of this study was to determine the transmission cycles in urban environments by evaluating sand fly diversity, detection of Leishmania DNA, and bloodmeal sources through intra and peridomestic collections. The study was carried out in Colombia, in 13 municipalities of Cordoba department, implementing a methodology that could be further used for the evaluation of vector-borne diseases in villages or towns. Our sampling design included 24 houses randomly selected in each of 15 villages distributed in 13 municipalities, which were sampled in two seasons in 2015 and 2016. Sand flies were collected using CDC light traps placed in intra and peridomestic habitats. In addition to the morphological identification, molecular identification through DNA barcodes was also performed. A total of 19,743 sand flies were collected and 13,848 of them (10,268 females and 3,580 males) were used in molecular procedures. Circulation of two known parasite species–Leishmania infantum and Leishmania panamensis was confirmed. Blood source analyses showed that sand flies fed on humans, particularly in the case of the known L. infantum vector, P. evansi; further analyses are advised to evaluate the reservoirs involved in parasite transmission. Our sampling design allowed us to evaluate potential transmission cycles on a department scale, by defining suspected vector species, parasite species present in different municipalities and feeding habits. PMID:29320544

Diversity patterns, Leishmania DNA detection, and bloodmeal identification of Phlebotominae sand flies in villages in northern Colombia.

PubMed

González, Camila; León, Cielo; Paz, Andrea; López, Marla; Molina, Gisell; Toro, Diana; Ortiz, Mario; Cordovez, Juan Manuel; Atencia, María Claudia; Aguilera, Germán; Tovar, Catalina

2018-01-01

Leishmaniases are neglected tropical diseases exhibiting complex transmission cycles due to the number of parasite species circulating, sand fly species acting as vectors and infected mammals, including humans, which are defined in the New World as accidental hosts. However, current transmission scenarios are changing, and the disease is no longer exclusively related to forested areas but urban transmission foci occur, involving some species of domestic animals as suspected reservoirs. The aim of this study was to determine the transmission cycles in urban environments by evaluating sand fly diversity, detection of Leishmania DNA, and bloodmeal sources through intra and peridomestic collections. The study was carried out in Colombia, in 13 municipalities of Cordoba department, implementing a methodology that could be further used for the evaluation of vector-borne diseases in villages or towns. Our sampling design included 24 houses randomly selected in each of 15 villages distributed in 13 municipalities, which were sampled in two seasons in 2015 and 2016. Sand flies were collected using CDC light traps placed in intra and peridomestic habitats. In addition to the morphological identification, molecular identification through DNA barcodes was also performed. A total of 19,743 sand flies were collected and 13,848 of them (10,268 females and 3,580 males) were used in molecular procedures. Circulation of two known parasite species-Leishmania infantum and Leishmania panamensis was confirmed. Blood source analyses showed that sand flies fed on humans, particularly in the case of the known L. infantum vector, P. evansi; further analyses are advised to evaluate the reservoirs involved in parasite transmission. Our sampling design allowed us to evaluate potential transmission cycles on a department scale, by defining suspected vector species, parasite species present in different municipalities and feeding habits.

Characteristics of Holocene sediments in the Gunsan Basin, central Yellow Sea

NASA Astrophysics Data System (ADS)

Woo, H. J.; Huh, S.; Jeong, K. S.; Lee, J. H.; Ham, A.; Kang, J.

2016-12-01

The Gunsan Basin, in the eastern part of the South Yellow Sea Basin, is filled by terrestrial sedimentary rocks, maximally up to 8 km deep on the basement of metamorphic rocks that constitutes the Yangtze Platform. The uppermost sedimentary layer (generally less than 1 km) appears to have formed experiencing the repeated marine environments since the middle Miocene. This study is to investigate the characteristics of Holocene sediments in the Gunsan Basin, based on interpretation of core sediments and high-resolution shallow (Sparker and Chirp) seismic profiles. The surface sediments in the basin consist of sand (56.6% on the average), silt (18.4%), and clay (25.0%) with a mean grain size of 1.5 to 7.8 Ø. Sand is prevalent (63.8 to 98.3%) in and around the Yellow Sea Trough lying in the eastern part of the basin. The sandy sediments are regarded as relict sediments deposited in the last glacial maximum (LGM). The sedimentary environments are classified, based on the acoustic and morphological characters of high-resolution shallow (Sparker and Chirp) seismic profiles, into mud zone, deformed zone, and sand ridges with sand waves zone from the west to the east in the Gunsan Basin. The deformed zone in the central Yellow Sea is a mixing area of sediments derived from China and Korea, where there are a number of paleochannels and erosional surfaces in the direction of northwest-southeast. The deformed zone represents non-deposition or erosion in the central Yellow Sea during the Holocene. Tidal sand ridges and sand waves are well developed along the coast of Korea. Modern sand ridges are generally moving in the northeast-southwest direction, which coincide with dominant tidal current direction. Fifteen piston cores were collected in the basin to investigate the general geological characters of the marine sedimentary sequence. In comparison with three cores in the southern basin, the sand contents tend to increase in the direction of east. 14C dates from three cores near border of Exclusive Economic Zone (EEZ) of Korea reveal that Holocene sediments have accumulated at the rate 6-18 cm/ka. The mud sediments sequentially change sandy mud to mud after the sea-level rise. In the Gunsan Basin, paleochannels played an important role in sedimentary processes during low sea-level periods of Quaternary.

Effects of Core Self-Evaluations on the Job Burnout of Nurses: The Mediator of Organizational Commitment

PubMed Central

Zhou, Yangen; Lu, Jiamei; Liu, Xianmin; Zhang, Pengcheng; Chen, Wuying

2014-01-01

Objective To explore the impact of Core self-evaluations on job burnout of nurses, and especially to test and verify the mediator role of organizational commitment between the two variables. Method Random cluster sampling was used to pick up participants sample, which consisted of 445 nurses of a hospital in Shanghai. Core self-evaluations questionnaire, job burnout scale and organizational commitment scale were administrated to the study participants. Results There are significant relationships between Core self-evaluations and dimensions of job burnout and organizational commitment. There is a significant mediation effect of organizational commitment between Core self-evaluations and job burnout. Conclusions To enhance nurses’ Core self-evaluations can reduce the incidence of job burnout. PMID:24755670

Summary of Paleotsunami Investigations in Aliomanu, Anahola, Kauai

NASA Astrophysics Data System (ADS)

Griswold, F. R.; La Selle, S.; Richmond, B. M.; Jaffe, B. E.; Gelfenbaum, G. R.; Chague-Goff, C.; LeVeque, R. J.; Bellanova, P.; Sugawara, D.; Nelson, A. R.

2016-12-01

The Hawaiian Islands are susceptible to tsunami hazards from both local and distant sources. Damaging historical tsunamis, such as the 1946 and 1957 Aleutian, and 1960 Chile tsunamis, have been observed in the Hawaiian Islands, but little is known about prehistoric tsunami events. We conducted a field survey in a freshwater marsh in Anahola Valley, on the northeast shore of Kauai, looking for prehistoric tsunami deposits. Cores were collected at 142 sites, spanning to 700 meters inland, using a vibracore, gouge augers, and Russian D-corer. The coring reveals the presence of at least three marine sand layers, which all exhibit a sharp basal contact with underlying marsh peats and muds. The two uppermost sand layers were dated by measuring 137Cs activity in the upper 50 cm of several cores. These sands were likely deposited by the 1946 and 1957 Aleutian tsunamis, both of which were observed by residents in Anahola Valley, with recorded run-ups of 5.2 m and 4.9 m, respectively. The deepest sand layer was deposited approximately 700 cal yr B.P. and may correspond to recently discovered tsunami deposits on Sedanka Island in the Aleutian Islands. In order to characterize the structure and composition of the deeper sand unit, as well as its possible origin, grain size, CT scan, and X-Ray fluorescence data were collected from the cores. We are modeling tsunami propagation and inundation in Anahola Valley to test whether the observed deposits are consistent with an Aleutian subduction zone earthquake source. Additional field investigations and analyses of candidate tsunami deposits are required in order to map the extent of this deposit throughout the Hawaiian Islands and to determine a probable source of this event.

Highstand shelf fans: The role of buoyancy reversal in the deposition of a new type of shelf sand body

USGS Publications Warehouse

Steel, Elisabeth; Simms, Alexander R.; Warrick, Jonathan; Yokoyama, Yusuke

2016-01-01

Although sea-level highstands are typically associated with sediment-starved continental shelves, high sea level does not hinder major river floods. Turbidity currents generated by plunging of sediment-laden rivers at the fluvial-marine interface, known as hyperpycnal flows, allow for cross-shelf transport of suspended sand beyond the coastline. Hyperpycnal flows in southern California have deposited six subaqueous fans on the shelf of the northern Santa Barbara Channel in the Holocene. Using eight cores and nine grab samples, we describe the deposits, age, and stratigraphic architecture of two fans in the Santa Barbara Channel. Fan lobes have up to 3 m of relief and are composed of multiple hyperpycnite beds ∼5 cm to 40 cm thick. Deposit architecture and geometry suggest the hyperpycnal flows became positively buoyant and lifted off the seabed, resulting in well-sorted, structureless, elongate sand lobes. Contrary to conventional sequence stratigraphic models, the presence of these features on the continental shelf suggests that active-margin shelves may locally develop high-quality reservoir sand bodies during sea-level highstands, and that such shelves need not be solely the site of sediment bypass. These deposits may provide a Quaternary analogue to many well-sorted sand bodies in the rock record that are interpreted as turbidites but lack typical Bouma-type features.

Effect of Binder and Mold parameters on Collapsibility and Surface Finish of Gray Cast Iron No-bake Sand Molds

NASA Astrophysics Data System (ADS)

Srinivasulu Reddy, K.; Venkata Reddy, Vajrala; Mandava, Ravi Kumar

2017-08-01

Chemically bonded no-bake molds and cores have good mechanical properties and produce dimensionally accurate castings compared to green sand molds. Poor collapsibility property of CO2 hardened sodium silicate bonded sand mold and phenolic urethane no-bake (PUN) binder system, made the reclamation of the sands more important. In the present work fine silica sand is mixed with phenolic urethane no-bake binder and the sand sets in a very short time within few minutes. In this paper it is focused on optimizing the process parameters of PUN binder based sand castings for better collapsibility and surface finish of gray cast iron using Taguchi design. The findings were successfully verified through experiments.

Sedimentological and geochemical investigations to understand source of sediments and processes of recent past in Schirmacher Oasis, East Antarctica

NASA Astrophysics Data System (ADS)

Choudhary, Shabnam; Tiwari, Anoop Kumar; Nayak, G. N.; Bejugam, Purnima

2018-03-01

Three sediment cores collected from GL-1, V-1(Vetehiya) and L-6 lakes of Schirmacher Oasis, East Antarctica were studied for sediment components (sand, silt, clay, total organic carbon, total nitrogen, TOC/TN ratio and biogenic silica), major elements (Aluminium, Iron and Manganese) and trace metals (Chromium, Zinc, Lead, Cobalt, Cadmium and Nickel). High sand content in all the three cores revealed the release of coarser sediments through mechanical weathering in fluvio-glacial environment. Relatively, high biogenic silica along with high total organic carbon associated with high clay in some sections indicated high primary productivity due to the warming and exposure of the lakes to the ice-melt water influx. TOC/TN ratio for all the cores was found to be < 10 which indicated that the major source of organic matter was autochthonous. Metals were found to be strongly associated with clay and organic carbon in core V-1, with sand and clay in core L-6 while, with silt and organic matter in core GL-1 indicating their role in regulating the distribution of metals. Cadmium in lake GL-1 was found to be associated with total organic carbon and showed largely biogenic origin, while, Cd and Pb in lakes L-6 and V-1 were found to be of anthropogenic origin. All the other metals showed signatures of lithogenic origin.

Holocene deltaic succession recording millennium-scale subsidence trend near the source region of the 2011 Tohoku-oki earthquake: An example from the Tsugaruishi plain, northeast Japan

NASA Astrophysics Data System (ADS)

Niwa, Y.; Sugai, T.; Matsushima, Y.; Toda, S.

2017-12-01

For clarification of megathrust earthquake cycle with recurrence interval of several hundreds to about a thousand years, crustal movement trend on a timescale of 103-104 years can be basic and important data. Well-dated Holocene sedimentary succession provides useful information for estimation of crustal movement trend on a timescale of 103 - 104 years. Here we collected three sediment cores, TGI1, TGI2, and TGI3, from the Tsugaruishi delta plain on the central Sanriku coast, which is near the source region of the 2011 Tohoku-oki earthquake and where discrepancies in crustal movement have been reported between uplift on a timescale of 105 years inferred from marine terrace versus subsidence on a timescale of 101-102 years from geodetic measurement. We recognized a Holocene deltaic succession in all three cores; basal gravel of alluvium, floodplain sand and mud, inner bay mud, prodelta delta front sand and mud, and fluvial sand and gravel, from lower to upper. In core TGI3, from the farthest inland site, the intertidal sediment facies, deposited from 7500 to 7000 cal BP, and the overlying 6-m-thick delta to floodplain facies, deposited from 7000 to 5000 cal BP, are both below the present sea level. Because a sea-level highstand due to hydroisostatic uplift around Japan occurred in the mid-Holocene, we inferred that the Tsugaruishi plain subsided during the Holocene, and the estimated subsidence rate, 1.1-1.9 mm/yr at maximum, is consistent with the recently reported subsidence rate along the southern Sanriku coast. The results of this study confirm that the central to southern Sanriku coast is subsiding, in contrast to an interpretation based on the study of marine terraces that this part of the coast is uplifting. The Holocene deltaic succession presented here will be useful for constructing an earthquake cycle model related to plate subduction.

Lithofacies and seismic-reflection interpretation of temperate glacimarine sedimentation in Tarr Inlet, Glacier Bay, Alaska

USGS Publications Warehouse

Cai, J.; Powell, R.D.; Cowan, E.A.; Carlson, P.R.

1997-01-01

High-resolution seismic-reflection profiles of sediment fill within Tart Inlet of Glacier Bay, Alaska, show seismic facies changes with increasing distance from the glacial termini. Five types of seismic facies are recognized from analysis of Huntec and minisparker records, and seven lithofacies are determined from detailed sedimentologic study of gravity-, vibro- and box-cores, and bottom grab samples. Lithofacies and seismic facies associations, and fjord-floor morphology allow us to divide the fjord into three sedimentary environments: ice-proximal, iceberg-zone and ice-distal. The ice-proximal environment, characterized by a morainal-bank depositional system, can be subdivided into bank-back, bank-core and bank-front subenvironments, each of which is characterized by a different depositional subsystem. A bank-back subsystem shows chaotic seismic facies with a mounded surface, which we infer consists mainly of unsorted diamicton and poorly sorted coarse-grained sediments. A bank-core depositional subsystem is a mixture of diamicton, rubble, gravel, sand and mud. Seismic-reflection records of this subsystem are characterized by chaotic seismic facies with abundant hyperbolic diffractions and a hummocky surface. A bank-front depositional subsystem consists of mainly stratified and massive sand, and is characterized by internal hummocky facies on seismic-reflection records with significant surface relief and sediment gravity flow channels. The depositional system formed in the iceberg-zone environment consists of rhythmically laminated mud interbedded with thin beds of weakly stratified diamicton and stratified or massive sand and silt. On seismic-reflection profiles, this depositional system is characterized by discontinuously stratified facies with multiple channels on the surface in the proximal zone and a single channel on the largely flat sediment surface in the distal zone. The depositional system formed in the ice-distal environment consists of interbedded homogeneous or laminated mud and massive or stratified sand and coarse silt. This depositional system shows continuously stratified seismic facies with smooth and flat surfaces on minisparker records, and continuously stratified seismic facies which are interlayered with thin weakly stratified facies on Huntec records.

A multiscale investigation of habitat use and within-river distribution of sympatric sand darter species

USGS Publications Warehouse

Thompson, Patricia A.; Welsh, Stuart A.; Strager, Michael P.; Rizzo, Austin A.

2018-01-01

The western sand darter Ammocrypta clara, and eastern sand darter Ammocrypta pellucida, are sand-dwelling fishes of conservation concern. Past research has emphasized the importance of studying individual populations of conservation concern, while recent research has revealed the importance of incorporating landscape scale processes that structure habitat mosaics and local populations. We examined habitat use and distributions of western and eastern sand darters in the lower Elk River of West Virginia. At the sandbar habitat use scale, western sand darters were detected in sandbars with greater area, higher proportions of coarse grain sand and faster bottom current velocity, while the eastern sand darter used a wider range of sandbar habitats. The landscape scale analysis revealed that contributing drainage area was an important predictor for both species, while sinuosity, which presumably represents valley type, also contributed to the western sand darter’s habitat suitability. Sandbar quality (area, grain size, and velocity) and fluvial geomorphic variables (drainage area and valley type) are likely key driving factors structuring sand darter distributions in the Elk River. This multiscale study of within-river species distribution and habitat use is unique, given that only a few sympatric populations are known of western and eastern sand darters.

Linking pore-scale and basin-scale effects on diffusive methane transport in hydrate bearing environments through multi-scale reservoir simulations

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

Nole, Michael; Daigle, Hugh; Cook, Ann

We explore the gas hydrate-generating capacity of diffusive methane transport induced by solubility gradients due to pore size contrasts in lithologically heterogeneous marine sediments. Through the use of 1D, 2D, and 3D reactive transport simulations, we investigate scale-dependent processes in diffusion-dominated gas hydrate systems. These simulations all track a sand body, or series of sands, surrounded by clays as they are buried through the gas hydrate stability zone. Methane is sourced by microbial methanogenesis in the clays surrounding the sand layers. In 1D, simulations performed in a Lagrangian reference frame demonstrate that gas hydrate in thin sands (3.6 m thick)more » can occur in high saturations (upward of 70%) at the edges of sand bodies within the upper 400 meters below the seafloor. Diffusion of methane toward the center of the sand layer depends on the concentration gradient within the sand: broader sand pore size distributions with smaller median pore sizes enhance diffusive action toward the sand’s center. Incorporating downhole log- and laboratory-derived sand pore size distributions, gas hydrate saturations in the center of the sand can reach 20% of the hydrate saturations at the sand’s edges. Furthermore, we show that hydrate-free zones exist immediately above and below the sand and are approximately 5 m thick, depending on the sand-clay solubility contrast. A moving reference frame is also adopted in 2D, and the angle of gravity is rotated relative to the grid system to simulate a dipping sand layer. This is important to minimize diffusive edge effects or numerical diffusion that might be associated with a dipping sand in an Eulerian grid system oriented orthogonal to gravity. Two-dimensional simulations demonstrate the tendency for gas hydrate to accumulate downdip in a sand body because of greater methane transport at depth due to larger sand-clay solubility contrasts. In 3D, basin-scale simulations illuminate how convergent sand layers in a multilayered system can compete for diffusion from clays between them, resulting in relatively low hydrate saturations. All simulations suggest that when hydrate present in clays dissociates with burial, the additional dissolved methane is soaked up by nearby sands preserving high hydrate saturations.« less

Characterization of methane-hydrate formation inferred from insitu Vp-density relationship for hydrate-bearing sediment cores obtained off the eastern coast of India

NASA Astrophysics Data System (ADS)

Kinoshita, M.; Hamada, Y.; Hirose, T.; Yamada, Y.

2017-12-01

In 2015, the Indian National Gas Hydrate Program (NGHP) Drilling Expedition 02 was carried out off the eastern margin of the Indian Peninsula in order to investigate distribution and occurrence of gas hydrates. From 25 drill sites, downhole logging data, cored samples, and drilling performance data were collected. One of the target areas (area B) is located on the axial and flank of an anticline, where the BSR is identified 100 m beneath the summit of anticline. 3 sites were drilled in the crest. The lower potential hydrate zone II was suggested by downhole logging (LWD) at 270-290 m below seafloor across the top of anticline. Core samples from this interval is characterized by a higher natural gamma radiation, gamma-ray-based higher bulk density and lower porosity, and higher electrical resistivity. All these features are in good agreement with LWD results. During this expedition, numerous special core sampling operations (PCAT) were carried out, keeping its insitu pressure in a pressure-tight vessel. They enabled acquiring insitu P-wave velocity and gamma-ray attenuation density measurements. In-situ X-CT images exhibit very clear hydrate distribution as lower density patches. Hydrate-bearing sediments exhibit a Vp-density trend that is clearly different from the ordinary formation. Vp values are significantly higher than 2 km/s whereas the density remains constant at 2-2.2 g/cm3 in hydrate zones. At some hydrate-bearing sediments, we noticed that Vp is negatively correlated to the density in the deeper portion (235-285 mbsf). On the other hand, in the shallower portion they are positively correlated. From lithostratigraphy the shallower portion consists of sand, whereas deeper portion are silty-clay dominant. We infer that the sand-dominant, shallower hydrate is a pore-filling type, and Vp is correlated positively to density. On the other hand, the clay-dominant, deeper hydrate is filled in vertical veins, and Vp is negatively correlated to density. Negative correlation may be explained by a (partial) replacement of pore water with hydrate because the density of hydrate is lower than the water.

Large-scale bedforms as indicators of mutually evasive sand transport and the sequential infilling of wide-mouthed estuaries

NASA Astrophysics Data System (ADS)

Harris, Peter T.

1988-06-01

Large-scale bedforms (2-10 m in vertical and 10 2-10 3 m in horizontal dimensions) found in wide-mouthed estuaries are described. Different bedform types occur depending upon the local availability of sand. With an increasing sand supply, sand ribbons grade into elongate trains of sand waves and then form sandwave fields. Inshore, headland-associated sand banks are formed which multiply into en-echelon sand banks. Based upon a review of data on directions of sand transport from the Bristol Channel and Thames Estuary, U.K., and from Moreton Bay, Australia, charts of ebb- and flood-dominant transport zones are constructed for lower estuarine environments which have undergone different degrees of infilling. Linear sand banks are seen to delimit partially the boundaries between opposing sand transport zones. Transport paths demonstrate how sediments derived from outside of the estuary are dispersed through ebb and flood transport zones, to supply other areas of net deposition. A comparison between different estuaries reveals that variations in the compexity of ebb- and flood-dominant transport zones and the morphologies of large-scale bedforms are coupled with apparent changes in the relative amounts of sand available to each system. A model for the sequential infilling of estuaries and the evolution of large-scale bedforms is presented and applied to the interpretation of present day examples. Vertical sequences predicted to be generated by such bedform evolution are described and discussed, in terms of their preservation in the geological record.

4D Imaging of Salt Precipitation during Evaporation from Saline Porous Media Influenced by the Particle Size Distribution

NASA Astrophysics Data System (ADS)

Norouzi Rad, M.; Shokri, N.

2014-12-01

Understanding the physics of water evaporation from saline porous media is important in many processes such as evaporation from porous media, vegetation, plant growth, biodiversity in soil, and durability of building materials. To investigate the effect of particle size distribution on the dynamics of salt precipitation in saline porous media during evaporation, we applied X-ray micro-tomography technique. Six samples of quartz sand with different grain size distributions were used in the present study enabling us to constrain the effects of particle and pore sizes on salt precipitation patterns and dynamics. The pore size distributions were computed using the pore-scale X-ray images. The packed beds were saturated with NaCl solution of 3 Molal and the X-ray imaging was continued for one day with temporal resolution of 30 min resulting in pore scale information about the evaporation and precipitation dynamics. Our results show more precipitation at the early stage of the evaporation in the case of sand with the larger particle size due to the presence of fewer evaporation sites at the surface. The presence of more preferential evaporation sites at the surface of finer sands significantly modified the patterns and thickness of the salt crust deposited on the surface such that a thinner salt crust was formed in the case of sand with smaller particle size covering larger area at the surface as opposed to the thicker patchy crusts in samples with larger particle sizes. Our results provide new insights regarding the physics of salt precipitation in porous media during evaporation.

Nugget-Navaho-Aztec sandstone: interaction of eolian sand sea with Andean-type volcanic arc

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

Marzolf, J.E.

1986-05-01

The Nugget-Navaho-Aztec sand sea was deposited east of an Andean-type volcanic arc. During the early stage of eolian deposition, fluvially transported sand was concentrated in the marine littoral zone and returned inland by onshore winds from the northwest. With progressive development of the arc, the sea withdrew. Wind direction changed from northwest to northeast. Previously deposited eolian sand was transported southwestward into the volcanic arc. Proximity of the arc can be detected with great difficulty by examining eolian and underlying red-bed facies. In southern Nevada, the volcanic arc is undetectable in eolian facies, but thin sandstone beds containing volcanic clastsmore » or weathered feldspar in the finer grained red-bed facies indicate arc volcanism; volcanic clasts are distinct in a basal conglomerate. Westward into California, the sub-Aztec Sandstone contains volcanic pebbles. The upper part of the Aztec Sandstone contains a 1 to 2-m thick volcaniclastic siltstone. Farther west, the Aztec Sandstone is interbedded with volcanic flows, ash flows, and flow breccias. These rocks might easily be mistaken for red beds in well cores or cuttings. Sand in sets of large-scale cross-beds remain virtually identical in composition and texture to sand in eolian facies of the Colorado Plateau. Where sets of eolian cross-beds lie on volcanics, the quartzose sandstone contains pebble to cobble-size volcanic clasts. Locally, cross-bed sets of yellowish-white, quartzose sandstone alternate with purplish-gray cross-bed sets containing numerous pebble to cobble-size volcanic clasts. The ability to recognize volcanic indicators within Nugget-Navaho-Aztec eolian facies is important in delineating the western margin of the back-arc eolian basin.« less

Sand incursion into temperate (Lithuania) and tropical (the Bahamas) maritime vegetation: Georadar visualization of target-rich aeolian lithosomes

NASA Astrophysics Data System (ADS)

Buynevich, Ilya V.; Savarese, Michael; Curran, H. Allen; Bitinas, Albertas; Glumac, Bosiljka; Pupienis, Donatas; Kopcznski, Karen; Dobrotin, Nikita; Gnivecki, Perry; Boush, Lisa Park; Damušytė, Aldona

2017-08-01

Interaction of windblown sand with maritime vegetation, either as dune migration or episodic grain transport is a common phenomenon along many sandy coasts. Vegetation introduces antecedent surface roughness, especially when scaled to the landform height, but its role may be concealed if overwhelmed by aeolian incursion and burial. Where field observations and cores lack detail for characterizing this complex process, ground-penetrating radar (GPR) offers continuous visualization of aeolian sequences. Along the Curonian Spit, Lithuania, dune reactivation phases resulted in massive invasion of siliciclastic sand triggered by natural perturbations and land clearance. Massive (>30 m high) dunes entombed mature pine, oak, and alder stands and this process is ongoing. Mid-frequency (200 MHz) georadar surveys reveal landward-dipping lateral accretion surfaces interrupted by high-amplitude point-source anomalies produced by recently buried trees. In tropical regions, dense vegetation and potential for rapid lithification of carbonate sand results in more complex internal structures. Along the windward coast of San Salvador Island, the Bahamas, a massive dune has buried several generations of maritime scrubland, resulting in highly chaotic reflection pattern and high target density. On a nearby Little Exuma Island, numerous reentrants in aeolianites promoted formation of blowouts and incursion of windblown sand 10-25 m into a silver thatch palm forest. High-frequency (800 MHz) GPR images resolve diffractions from trunks and roots buried by > 2 m of oolitic sand. Basal refection morphology helps differentiate the irregular dune/beachrock surface from a smooth palm-frond mat. Aside from detecting and mapping buried vegetation, geophysical images capture its effect on sediment accumulation. This has the potential for differentiating its effect from other discordant structures within dunes (clasts, dissolution voids, trunk molds, burrows, and cultural remains).

Potential methane production and oxidation in soil reclamation covers of an oil sands mining site in Alberta, Canada

NASA Astrophysics Data System (ADS)

Pum, Lisa; Reichenauer, Thomas; Germida, Jim

2015-04-01

Anthropogenic activities create a number of significant greenhouse gases and thus potentially contribute to global warming. Methane production is significant in some agricultural production systems and from wetlands. In soil, methane can be oxidised by methanotrophic bacteria. However, little is known about methane production and oxidation in oil sand reclamation covers. The purpose of this study was to investigate methane production and oxidation potential of tailing sands and six different reclamation layers of oil sands mining sites in Alberta, Canada. Methane production and oxidation potential were investigated in laboratory scale microcosms through continuous headspace analysis using gas chromatography. Samples from a reclamation layer were collected at the Canadian Natural Resources Limited (CNRL) reclamation site at depths of 0-10 cm, 10-20 cm and 20-40 cm in October 2014. In addition, tailing sands provided by Suncor Energy Inc. and soil from a CNRL wetland were studied for methane production. Samples were dried, crushed and sieved to 4 mm, packed into serum bottle microcosms and monitored for eight weeks. Methane production potential was assessed by providing an anoxic environment and by adjusting the samples to a moisture holding capacity of 100 %. Methane oxidation potential was examined by an initial application of 2 vol % methane to the microcosms and by adjusting the samples to a moisture holding capacity of 50 %. Microcosm headspace gas was analysed for methane, carbon dioxide, nitrous oxide and oxygen. All experiments were carried out in triplicates, including controls. SF6 and Helium were used as internal standards to detect potential leaks. Our results show differences for methane production potential between the soil depths, tailing sands and wetlands. Moreover, there were differences in the methane oxidation potential of substrate from the three depths investigated and between the reclamation layers. In conclusion, the present study shows that reclamation layers for oil sands mining sites in Alberta, Canada have the potential to oxidize on-site produced methane emissions to the less harmful greenhouse gas carbon dioxide. Such oxidation might mitigate impacts of methane production from these sites.

Bitumen recovery from oil sands using deep eutectic solvent and its aqueous solutions

NASA Astrophysics Data System (ADS)

Pulati, Nuerxida

Oil sands compose a significant proportion of the world's known oil reserves. Oil sands are also known as tar sands and bituminous sands, are complex mixtures of sand, clays, water and bitumen, which is "heavy" and highly viscous oil. The extraction and separation of bitumen from oil sands requires significant amount of energy and large quantities of water and poses several environmental challenges. Bitumen can be successfully separated from oil sands using imidazolium based ionic liquids and nonpolar solvents, however, ionic liquids are expensive and toxic. In this thesis, the ionic liquid alternatives- deep eutectic solvent, were investigated. Oil sands separation can be successfully achieved by using deep eutectic solvents DES (choline chloride and urea) and nonpolar solvent naphtha in different types of oil sands, including Canadian ("water-wet"), Utah ("oil-wet") and low grade Kentucky oil sands. The separation quality depends on oil sands type, including bitumen and fine content, and separation condition, such as solvent ratio, temperature, mixing time and mechanical centrifuge. This separation claims to the DES ability to form ion /charge layering on mineral surface, which results in reduction of adhesion forces between bitumen and minerals and promote their separation. Addition of water to DES can reduce DES viscosity. DES water mixture as a media, oil sands separation can be achieved. However, concentration at about 50 % or higher might be required to obtain a clear separation. And the separation efficiency is oil sands sample dependent. The highest bitumen extraction yield happened at 75% DES-water solution for Utah oil sands samples, and at 50 60% DES-water solutions for Alberta oil sands samples. Force curves were measured using Atomic Force Microscopy new technique, PeakForce Tapping Quantitative Nanomechanical Mapping (PFTQNM). The results demonstrate that, by adding DES, the adhesion force between bitumen and silica and dissipation energy will decrease comparing to DI water. At higher concentration DES solution (>80%DES), the amount of decrease can be up to 80-90%. In lower concentration, at about 50% decrease was observed. The results provide fundamental insights into the mechanism of bitumen separation from oil sands. The reduction of adhesion force between bitumen and minerals (silica) in DES media is the main reason which facilitates the separation between them, which by means existence of DES will favor bitumen and minerals separation. Comparing to other techniques, DES based separation is environmentally compatible and economically viable. The separation can easily happen at room temperature. Choline chloride and urea are biodegradable, environmentally compatible, accessible in large scale and easily prepared by mixing and heating (<80 °C). Further improvement is needed regarding to separation quality and efficiency, either in the direction of developing better separation techniques or by looking for chemical additives which can improve separation and reduce environmental side-effects.

Late Pleistocene shallow water sand transported to the slope at IODP Sites U1484 and U1485 off the north coast of Papua New Guinea: how, when and why?

NASA Astrophysics Data System (ADS)

Mountain, G. S.; Browning, J. V.; Bova, S. C.

2017-12-01

IODP Exp 363 drilled two sites on a gently seaward-dipping terrace 18 and 21 km north of Papua New Guinea, enabling the study of mechanisms that bring shallow water sediment to the deep sea. We expect past changes in sea level and precipitation / fluvial run-off dominated this record, but additional processes may have been important. We examined Hole U1484B (1031 m water depth; 223 m drilled; 99.8% recovered) and detected 339 sharp-based sand layers 0.5 cm or more thick. In contrast to the background hemipelagic nanno-bearing silty clay, sand layers are graded or massive turbidites containing detrital grains, shallow-water benthic foraminifera, shell fragments and/or wood. δ18O values of Globigerinoides ruber tied to the isotopic curve of Lisiecki and Raymo (2004) show the densest concentration of sand layers in the last 310 ka occurred during the cooling trend of MIS stage 6. Stage 2 contains significantly fewer discrete sand beds, even during the coldest part of the LGM. Other times of glacial intensification show a similarly modest correlation to peak sand deposition. Sand layers strongly correlate with high values of magnetic susceptibility (MS) measured on unsplit cores, and when mapped to the MIS time scale, MS increases match times of ice growth / falling sea level more consistently than does the density of sand layers. We attribute this to reworking of discrete sand layers by bioturbation, indicating the need for caution tying the absence of sharp-based sands to times of transgression or low precipitation / fluvial run-off. Packages of especially thick and closely-spaced sharp-based sands match seismic reflections at Site U1484. Tracing these reflections throughout the grid of hi-res MCS site survey profiles reveals the areal distribution and transport path of sand as well as a direct tie to similar sharp-based sands in the more distal Hole U1485A (1145 m water depth; 301 m drilled; 103.8% recovered.) The distribution of sands through time might be influenced by sea level and/or precipitation, in which case they should exhibit orbital cyclicity and patterns in provenance. Alternatively, some may be turbidites that originated on the upper slope due to non-periodic earthquakes along this active plate boundary; inferences based on the age and provenance of sands at both sites will evaluate this possibility.

Digital shaded relief image of a carbonate platform (northern Great Bahama Bank): Scenery seen and unseen

NASA Astrophysics Data System (ADS)

Boss, Stephen K.

1996-11-01

A mosaic image of the northern Great Bahama Bank was created from separate gray-scale Landsat images using photo-editing and image analysis software that is commercially available for desktop computers. Measurements of pixel gray levels (relative scale from 0 to 255 referred to as digital number, DN) on the mosaic image were compared to bank-top bathymetry (determined from a network of single-channel, high-resolution seismic profiles), bottom type (coarse sand, sandy mud, barren rock, or reef determined from seismic profiles and diver observations), and vegetative cover (presence and/or absence and relative density of the marine angiosperm Thalassia testudinum determined from diver observations). Results of these analyses indicate that bank-top bathymetry is a primary control on observed pixel DN, bottom type is a secondary control on pixel DN, and vegetative cover is a tertiary influence on pixel DN. Consequently, processing of the gray-scale Landsat mosaic with a directional gradient edge-detection filter generated a physiographic shaded relief image resembling bank-top bathymetric patterns related to submerged physiographic features across the platform. The visibility of submerged karst landforms, Pleistocene eolianite ridges, islands, and possible paleo-drainage patterns created during sea-level lowstands is significantly enhanced on processed images relative to the original mosaic. Bank-margin ooid shoals, platform interior sand bodies, reef edifices, and bidirectional sand waves are features resulting from Holocene carbonate deposition that are also more clearly visible on the new physiographic images. Combined with observational data (single-channel, high-resolution seismic profiles, bottom observations by SCUBA divers, sediment and rock cores) across the northern Great Bahama Bank, these physiographic images facilitate comprehension of areal relations among antecedent platform topography, physical processes, and ensuing depositional patterns during sea-level rise.

Sand dune of Ruby, Arizona, an anthropogenically created biodiversity hotspot for wasps and their velvet ant parasitoids

Treesearch

Justin O. Schmidt

2013-01-01

A large artificial sand dune composed of finely crushed mine tailings was produced by deep mining operations at Ruby, Arizona. Today, the ghost town of Ruby is an important historical location and biodiversity refuge, with the newly formed dune forming the core of the refuge. The dune provides ideal nesting habitat for at least 13 species of sand-loving wasps,...

A Xhosa language translation of the CORE-OM using South African university student samples.

PubMed

Campbell, Megan M; Young, Charles

2016-10-01

The translation of well established psychometric tools from English into Xhosa may assist in improving access to psychological services for Xhosa speakers. The aim of this study was to translate the Clinical Outcomes in Routine Evaluation - Outcome Measure (CORE-OM), a measure of general distress and dysfunction developed in the UK, into Xhosa for use at South African university student counselling centres. The CORE-OM and embedded CORE-10 were translated into Xhosa using a five-stage translation design. This design included (a) forward-translation, (b) back-translation, (c) committee approach, (d) qualitative piloting, and (e) quantitative piloting on South African university students. Clinical and general samples were drawn from English-medium South African universities. Clinical samples were generated from university student counselling centres. General student samples were generated through random stratified cluster sampling of full-time university students. Qualitative feedback from the translation process and results from quantitative piloting of the 34-item CORE-OM English and Xhosa versions supported the reduction of the scale to 10 items. This reduced scale is referred to as the South African CORE-10 (SA CORE-10). A measurement and structural model of the SA CORE-10 English version was developed and cross-validated using an English-speaking university student sample. Equivalence of this model with the SA CORE-10 Xhosa version was investigated using a first-language Xhosa-speaking university sample. Partial measurement equivalence was achieved at the metric level. The resultant SA CORE-10 Xhosa and English versions provide core measures of distress and dysfunction. Additional, culture- and language-specific domains could be added to increase sensitivity and specificity. © The Author(s) 2016.

Neoformation of clay in lateral root catchments of mallee eucalypts: a chemical perspective

PubMed Central

Verboom, William H.; Pate, John S.; Aspandiar, Mehrooz

2010-01-01

Background and Aims A previous paper (Annals of Botany 103: 673–685) described formation of clayey pavements in lateral root catchments of eucalypts colonizing a recently formed sand dune in south-west Western Australia. Here chemical and morphological aspects of their formation at the site are studied. Methods Chemical and physical examinations of soil cores through pavements and sand under adjacent heath assessed build-up of salts, clay and pH changes in or below pavements. Relationships of root morphology to clay deposition were examined and deposits subjected to scanning electron microscopy and energy-dispersive X-ray analysis. Xylem transport of mineral elements in eucalypt and non-eucalypt species was studied by analysis of xylem (tracheal) sap from lateral roots. Key Results The columns of which pavements are composed develop exclusively on lower-tier lateral roots. Such sites show intimate associations of fine roots, fungal filaments, microbiota and clay deposits rich in Si, Al and Fe. Time scales for construction of pavements by eucalypts were assessed. Cores through columns of pavemented profiles showed gross elevations of bulk density, Al, Fe and Si in columns and related increases in pH, Mg and Ca status in lower profiles. A cutting through the dune exhibited pronounced alkalinity (pH 7–10) under mallee woodland versus acidity (pH 5–6·5) under proteaceous heath. Xylem sap analyses showed unusually high concentrations of Al, Fe, Mg and Si in dry-season samples from column-bearing roots. Conclusions Deposition of Al–Fe–Si-rich clay is pivotal to pavement construction by eucalypts and leads to profound chemical and physical changes in relevant soil profiles. Microbial associates of roots are likely to be involved in clay genesis, with parent eucalypts supplying the required key mineral elements and carbon sources. Acquisition of the Al and Fe incorporated into clay derives principally from hydraulic uplift from ground water via deeply penetrating tap roots. PMID:19897459

Estimation of groundwater flow from temperature monitoring in a borehole heat exchanger during a thermal response test

NASA Astrophysics Data System (ADS)

Yoshioka, Mayumi; Takakura, Shinichi; Uchida, Youhei

2018-05-01

To estimate the groundwater flow around a borehole heat exchanger (BHE), thermal properties of geological core samples were measured and a thermal response test (TRT) was performed in the Tsukuba upland, Japan. The thermal properties were measured at 57 points along a 50-m-long geological core, consisting predominantly of sand, silt, and clay, drilled near the BHE. In this TRT, the vertical temperature in the BHE was also monitored during and after the test. Results for the thermal properties of the core samples and from the monitoring indicated that groundwater flow enhanced thermal transfers, especially at shallow depths. The groundwater velocities around the BHE were estimated using a two-dimensional numerical model with monitoring data on temperature changes. According to the results, the estimated groundwater velocity was generally consistent with hydrogeological data from previous studies, except for the data collected at shallow depths consisting of a clay layer. The reasons for this discrepancy at shallow depths were predicted to be preferential flow and the occurrence of vertical flow through the BHE grout, induced by the hydrogeological conditions.

Variable scale channel avulsion history using fan architecture and stratigraphy, and sediment provenance of Sutlej-Yamuna fans in northwest Gangetic plains during Late Quaternary

NASA Astrophysics Data System (ADS)

Singh, Ajit; Gupta, Sanjeev; Sinha, Rajiv; Densmore, Alexander; Buylaert, Jan-Pieter; Carter, Andrew; Van-Dijk, Wout M.; Joshi, Suneel; Nayak, Nibedita; Mason, Philippa J.; Kumar, Dewashish; Mondal, Setbandhu; Murray, Andrew; Rai, Shiv P.; Shekhar, Shashank

2016-04-01

Channel avulsion during fan development controls distribution and deposition of channel sandbodies and hence alluvial architecture of a fan system. Variable scale spatio-temporal information of fluvial responses to past climate changes is stored in these channel sandbodies. Further these channel sandbodies form fluvial aquifers in alluvial fans and therefore understanding of alluvial architecture and stratigraphy of a fan is crucial for development of groundwater management strategies. In this study we used multiple approaches to map subsurface fluvial aquifer architecture and alluvial stratigraphy, and to estimate sediment provenance using U-Pb dating of detrital zircon grains of Sutlej-Yamuna fan system in northwest India. Satellite imagery based geomorphic mapping shows two large fan system with interfan area. The fan surfaces show presence of major and minor paleochannels. 2D resistivity tomography along several transects across fan surfaces shows distinct layers with contrasting resistivity values. These geo-electric facies corresponds to presence of channel sandbodies beneath surface signature of paleochannels and finer floodplain deposits useful to demarcate lateral extent of subsurface channel sandbodies. A more detailed subsurface stratigraphy using ~50m deep sediment cores and their luminescence ages from across fan surface shows presence of multi-storey sandbodies (MSB) separated by floodplain fines. Within the MSB, individual channel deposits are identified by presence of channel scour surfaces located at coarse sand overlying fine sand layer. Depositional ages of MSB's ranges from ~81 ka (late MIS5) to ~15 ka (MIS2) with major depositional break during MIS3 in parts of the fans. Sediment aggradation rate varies laterally across fan surface as well as vertically down the depth with an average rate of 0.54 mm/year. Fluvial channel persistence for studied time interval (about last 81 ka BP) shows major depositional breaks (and possible incision) at ~41 ka (mid MIS3) and ~31 ka (late MIS3). U-Pb age patterns of detrital zircon grains from cores located at paleochannels on the fan system show prominent age peaks at ~480 Ma and ~1800 Ma that respectively corresponds to modern Sutlej and Yamuna rivers. Luminescence ages of these samples suggest that major channel activity of Sutlej river at its fan system ceased around ~15 ka (post last-glacial maxima) and thereafter it avulsed to its modern course. Our surface study results clearly show that alluvial fan system have well developed longitudinal channel sandbodies that may or may not have surface expression in the form of paleochannel and/or longitudinal ridges. However our geophysical studies show that such channel sandbodies can be delineated in shallow surface on the basis of characteristic resistivity values. The subsurface stratigraphy results show development of MSB possibly due to series of small scale (intravalley) avulsion punctuated by large scale (intervalley) avulsion across the fan surface. Our provenance studies clearly identifies two major large scale channel avulsions of Sutlej and Yamuna rivers. Our study has importance for groundwater management policies in this water-stressed agricultural hotspot of India. Thus, understanding the variability in sand body stratigraphy, channel avulsion history, and aggradation rates is important for understanding aquifer geometry of alluvial fan system.

Mid-infrared spectroscopic analysis of chemically bound metalcasting sands

USDA-ARS?s Scientific Manuscript database

Foundries around the world discard millions of tonnes of molding and core sand each year even though they can be beneficially used in manufactured soils and geotechnical applications. Despite their usefulness as an aggregate replacement, some environmental authorities are concerned over potential ne...

Sand transportation and reverse patterns over leeward face of sand dune

NASA Astrophysics Data System (ADS)

Jiang, Hong; Dun, Hongchao; Tong, Ding; Huang, Ning

2017-04-01

Sand saltation has complex interactions with turbulent flow and dune form. Most models of wind-blown sand consider ideal circumstances such as steady wind velocity and a flat surface, and the bulk of data on wind flow and sand transport over an individual dune has focused mostly on the influence of dune shape or inter-dune space on the wind flow, neglecting the effect of morphology on sand saltation, particularly airflow and sand transportation over the leeward slope. Wind flow structures over the leeward slope of sand dunes have a fundamental influence on the organization of sand dunes. In order to understand sand dune dynamics, lee face airflow and sediment transportation should be paid more attention. Previous field observations could not measure turbulent flow structure well because of the limited observation points and the influence of experiment structure on wind field. In addition, the reverse sand particles over leeward face could not be collected by sand trap in field. Numerous field observations could not measure turbulent flow structure because of the limited observation points and the influence of experimental structures on the wind field. In addition, the reverse transport of sand particles over leeward face could not be collected by sand traps in field. Therefore, this paper aims to investigate the turbulent flow structure and sand transport pattern over the leeward slope. A numerical model of sand saltation over slope terrain is constructed, which also considers the coupling effects between air flow and sand particles. The large eddy simulation method is used to model turbulent flow. Sand transport is simulated by tracking the trajectory of each sand particle. The results show that terrain significantly alters the turbulent air flow structure and wind-blown sand movement, especially over the leeward slope. Here, mass flux increases initially and then decreases with height in the reversed flow region in the direction of wind flow, and the mass flux decreases with height in the reversed direction. The height of 0.5 H is the height of vortex core in the reversed flow region. The vortex core is a critical point in the flow region where few particles are transited. In the reversed region, the reversed mass flux of sand particles is 25% of the mass flux in the flow direction. This research may contribute to scientific understanding of the mechanisms of sand motion and wind flow over leeward of dune and it is likely to be significant in desertification control.

The provenance of Taklamakan desert sand

NASA Astrophysics Data System (ADS)

Rittner, Martin; Vermeesch, Pieter; Carter, Andrew; Bird, Anna; Stevens, Thomas; Garzanti, Eduardo; Andò, Sergio; Vezzoli, Giovanni; Dutt, Ripul; Xu, Zhiwei; Lu, Huayu

2016-03-01

Sand migration in the vast Taklamakan desert within the Tarim Basin (Xinjiang Uyghur Autonomous region, PR China) is governed by two competing transport agents: wind and water, which work in diametrically opposed directions. Net aeolian transport is from northeast to south, while fluvial transport occurs from the south to the north and then west to east at the northern rim, due to a gradual northward slope of the underlying topography. We here present the first comprehensive provenance study of Taklamakan desert sand with the aim to characterise the interplay of these two transport mechanisms and their roles in the formation of the sand sea, and to consider the potential of the Tarim Basin as a contributing source to the Chinese Loess Plateau (CLP). Our dataset comprises 39 aeolian and fluvial samples, which were characterised by detrital-zircon U-Pb geochronology, heavy-mineral, and bulk-petrography analyses. Although the inter-sample differences of all three datasets are subtle, a multivariate statistical analysis using multidimensional scaling (MDS) clearly shows that Tarim desert sand is most similar in composition to rivers draining the Kunlun Shan (south) and the Pamirs (west), and is distinctly different from sediment sources in the Tian Shan (north). A small set of samples from the Junggar Basin (north of the Tian Shan) yields different detrital compositions and age spectra than anywhere in the Tarim Basin, indicating that aeolian sediment exchange between the two basins is minimal. Although river transport dominates delivery of sand into the Tarim Basin, wind remobilises and reworks the sediment in the central sand sea. Characteristic signatures of main rivers can be traced from entrance into the basin to the terminus of the Tarim River, and those crossing the desert from the south to north can seasonally bypass sediment through the sand sea. Smaller ephemeral rivers from the Kunlun Shan end in the desert and discharge their sediment there. Both river run-off and wind intensity are strongly seasonal, their respective transport strength and opposing directions maintain the Taklamakan in its position and topography.

Suitability assessment of grey water quality treated with an upflow-downflow siliceous sand/marble waste filtration system for agricultural and industrial purposes.

PubMed

Chaabane, Safa; Riahi, Khalifa; Hamrouni, Hédi; Thayer, Béchir Ben

2017-04-01

The present study examines the suitability assessment of an upflow-downflow siliceous sand/marble waste filtration system for treatment and reuse of grey water collected from bathrooms of the student residential complex at the Higher Institute of Engineering Medjez El Bab (Tunisia). Once the optimization of grey water pre-treatment system has been determined, the filtration system was operated at different hydraulic loading rate and media filter proportions in order to assess the suitability of treated grey water for irrigational purpose according to salinity hazard, sodium hazard, magnesium hazard, permeability index, water infiltration rate, and widely used graphical methods. Suitability of the treated grey water for industrial purpose was evaluated in terms of foaming, corrosion, and scaling. Under optimal operational conditions, results reveals that treated grey water samples with an upflow-downflow siliceous sand/marble waste filtration system may be considered as a good and an excellent water quality suitable for irrigation purpose. However, treated grey water was found not appropriate for industrial purpose due to high concentrations of calcium and sodium that can generate foaming and scaling harm to boilers. These results suggest that treated grey water with an upflow-downflow siliceous sand/marble waste filtration system would support production when used as irrigation water.

Geostatistics and the representative elementary volume of gamma ray tomography attenuation in rocks cores

USGS Publications Warehouse

Vogel, J.R.; Brown, G.O.

2003-01-01

Semivariograms of samples of Culebra Dolomite have been determined at two different resolutions for gamma ray computed tomography images. By fitting models to semivariograms, small-scale and large-scale correlation lengths are determined for four samples. Different semivariogram parameters were found for adjacent cores at both resolutions. Relative elementary volume (REV) concepts are related to the stationarity of the sample. A scale disparity factor is defined and is used to determine sample size required for ergodic stationarity with a specified correlation length. This allows for comparison of geostatistical measures and representative elementary volumes. The modifiable areal unit problem is also addressed and used to determine resolution effects on correlation lengths. By changing resolution, a range of correlation lengths can be determined for the same sample. Comparison of voxel volume to the best-fit model correlation length of a single sample at different resolutions reveals a linear scaling effect. Using this relationship, the range of the point value semivariogram is determined. This is the range approached as the voxel size goes to zero. Finally, these results are compared to the regularization theory of point variables for borehole cores and are found to be a better fit for predicting the volume-averaged range.

Geohydrologic units of the Gulf Coastal Plain in Arkansas

USGS Publications Warehouse

Petersen, J.C.; Broom, M.E.; Bush, W.V.

1985-01-01

This report describes geohydrologic units of the Jurassic, Cretaceous, Tertiary and Quaternary Systems and of the Paleozoic Era in the Gulf Coastal Plain in Arkansas. Structure contour maps on top of the Paleozoic rocks, Trinity Group, Tokio Formation, Nacatoch Sand, Midway Group, Wilcox Group, Carrizo Sand, Cane River Formation. Sparta Sand, and the Memphis Sand are included. Thickness maps of the Wilcox Group, Carrizo Sand, Cane River Formation, Sparta Sand, and the Memphis Sand and maps showing lines of equal dissolved-solids concentrations of the Nacatoch Sand, Wilcox Group, Carrizo Sand, Cane River Formation, and Sparta Sand are also included. The dissolved-solids maps are at about a 1:2 million scale. All other maps are at a 1:1 million scale. Brief descriptions of the geohydrologic units mentioned above and of the Cook Mountain and Cockfield Formations and the Jackson Group are also included. (USGS)

A giant sediment trap in the Florida keys

USGS Publications Warehouse

Shinn, E.A.; Reich, C.D.; Locker, S.D.; Hine, A.C.

1996-01-01

Aerial photography, high-resolution seismic profiling, coring and jet probing have revealed a large sediment-filled sinkhole in the Key Largo National Marine Sanctuary off Key Largo, Florida. The 600-m-diameter feature straddles coral reef and carbonate-sand facies and contains >55 m of marine lime sand and aragonite mud. Bulk 14C age determinations of mud from a 30- m sediment core indicate infilling rates exceeding 20 m/ka between 3 and 5.6 ka. The total thickness and nature of the sediment near the base of the sinkhole are not known.

The hazard education model in the high school science-club activities above active huge fault

NASA Astrophysics Data System (ADS)

Nakamura, R.

2017-12-01

Along the west coast of pacific ocean, includes Japan, there are huge numerous volcanoes and earthquakes. The biggest cause is their location on the border of plates. The pressure among the plates cause strains and cracks. By the island arc lines, strains make long and enormous faults. More than huge 150 faults are reported (the head quarters for earthquake research promotion, Japan, 2017). Below my working school, it is laying one of the biggest faults Nagamachi-Rifu line which is also laying under 1 million population city Sendai. Before 2011 Tohoku earthquake, one of the hugest earthquake was predicted because of the fault activities. Investigating the fault activity with our school student who live in the closest area is one of the most important hazard education. Therefore, now we are constructing the science club activity with make attention for (1) seeking fault line(s) with topographic land maps and on foot search (2) investigate boling core sample soils that was brought in our school founded. (1) Estimate of displacement of the faults on foot observation In order to seek the unknown fault line in Rifu area, at first it was needed to estimate on the maps(1:25,000 Scale Topographic Maps and Active Faults in Urban Area of Map(Sendai), Geographical Survey Institute of Japan). After that estimation, walked over the region with club students to observe slopes which was occurred by the faults activation and recorded on the maps. By observant slope gaps, there has a possibilities to have 3 or 4 fault lines that are located parallel to the known activate faults. (2) Investigate of the boling core samples above the fault. We investigated 6 columnar-shaped boling core samples which were excavated when the school has been built. The maximum depth of the samples are over 20m, some are new filled sands over original ash tephra and pumice from old volcanoes located west direction. In the club activities, we described column diagram of sediments and discussed the sediment circumstances by the sediments grain observation, however, it was impossible to describe the sediments origin of exact volcano(es).

REACH-SCALE GEOMORPHOLOGY AFFECTS ORGANIC MATTER AND CONSUMER Ä 13C IN A FORESTED PIEDMONT STREAM

EPA Science Inventory

We investigated seasonal (spring, autumn) and spatial variation of stream organic matter and consumer δ 13C in a Piedmont stream. Sites were sampled along a continuum and fit into two geomorphic categories: high-gradient, rock-bed ("rock") or low-gradient, sand-bed...

Geochemical data for mercury, methylmercury, and other constituents in sediments from Englebright Lake, California, 2002

USGS Publications Warehouse

Alpers, Charles N.; Hunerlach, Michael P.; Marvin-DePasquale, Mark C.; Antweiler, Ronald C.; Lasorsa, Brenda K.; De Wild, John F.; Snyder, Noah P.

2006-01-01

Deep coring penetrated the full thickness of material deposited after 1940 at six locations in the reservoir; the cores reached a maximum depth of 32.8 meters below the reservoir floor. At the three deep coring sites closest to Englebright Dam, concentrations of HgT (dry basis) were consistently in the range of 100 to 500 ng/g (nanogram per gram), in sediment dominantly of silt size (median grain size of 0.004 to 0.063 mm [millimeter]). At the deep coring sites located farther upstream, the upper parts of the profile had lower concentrations of HgT, generally ranging from 2 to 100 ng/g, in sediment dominantly of sand size (median grain size from 0.063 to 2 mm). The lower part of the vertical profiles at three upstream coring sites had higher concentrations of HgT than the upper and middle parts of these profiles, and had finer median grain size. The highest median concentration of MeHg (1.1 ng/g) was in the top 2 cm (centimeter) of the shallow box cores. This vertical interval also had the highest value of the ratio of MeHg to HgT, 0.41 percent. Median concentrations of MeHg and median values of MeHg/HgT decreased systematically with depth from 0-4 to 4-8 to 8-12 cm in the shallow cores. However, similar systematic decreases were not observed at the meter scale in the deep cores of the MEM (MEthylMercury) series. The overall median of the ratio MeHg/HgT in the deep cores was 0.25 percent, not much less than the overall median value for the shallow cores (0.33 percent). Mercury-203 radiotracer divalent inorganic mercury (203Hg(II)) was used to determine microbial mercury-methylation potential rates for 11 samples collected from three reservoir locations and various depths in the sediment profile. For the five shallow mercury-methylation subsamples, ancillary geochemical parameters were assayed, including microbial sulfate reduction rates, sulfur speciation (sediment acid volatile sulfide, total reduced sulfur, and pore-water sulfate), iron speciation (sediment acid extractable iron(II), amorphous iron(III), crystalline iron(III) and pore-water iron(II)), pore-water chloride and dissolved organic carbon, and pH, oxidation-reduction potential (Eh) and whole-sediment organic content. The highest potential rates of microbial mercury methylation were measured in shallow (0 to 8 cm depth) sediments (5 to 30 nanograms of mercury per gram dry sediment per day), whereas potential rates for subsamples collected from depths greater than 500 cm were consistently below the detection limit of the radiotracer method (< 0.02 nanogram of mercury per gram dry sediment per day). Chemical analyses of trace and major elements in bed sediment are presented for 202 samples from deep cores from five locations in Englebright Lake. The mean values and standard deviations for selected trace elements were as follows (in micrograms per gram): antimony, 2.4 ? 1.6; arsenic, 69 ? 48; chromium, 134 ? 23; lead, 33 ? 25; and nickel, 87 ? 24. Concentrated samples of heavy-mineral grains, prepared using nine large-volume composite samples from

Leaching assessment of road materials containing primary lead and zinc slags.

PubMed

Barna, R; Moszkowicz, P; Gervais, C

2004-01-01

Characterisation of the leaching behaviour of waste-containing materials is a crucial step in the environmental assessment for reuse scenarios. In our research we applied the multi-step European methodology ENV 12-920 to the leaching assessment of road materials containing metallurgical slag. A Zn slag from an imperial smelting furnace (ISF) and a Pb slag from a lead blast furnace (LBF) are investigated. The two slags contain up to 11.2 wt% of lead and 3.5 wt% of zinc and were introduced as a partial substitute for sand in two road materials, namely sand-cement and sand-bitumen. At the laboratory scale, a leaching assessment was performed first through batch equilibrium leaching tests. Second, the release rate of the contaminants was evaluated using saturated leaching tests on monolithic material. Third, laboratory tests were conducted on monolithic samples under intermittent wetting conditions. Pilot-scale tests were conducted for field testing of intermittent wetting conditions. The results show that the release of Pb and Zn from the materials in a saturated scenario was controlled by the pH of the leachates. For the intermittent wetting conditions, an additional factor, blocking of the pores by precipitation during the drying phase is proposed. Pilot-scale leaching behaviour only partially matched with the laboratory-scale test results: new mass transfer mechanisms and adapted laboratory leaching tests are discussed.

21. WHILE AUTOMATED CORE BLOWERS REDUCED THE NUMBER OF HANDMADE ...

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

21. WHILE AUTOMATED CORE BLOWERS REDUCED THE NUMBER OF HAND-MADE CORES IN THE 1950S, MANY SMALLER CORES COULD STILL BE FORMED FASTER BY HAND WITH A RESIGN IMPREGNATED SAND PRIOR TO BAKING. HAND CORE-MAKING WAS ALSO ONE OF THE FEW POSITIONS WOMEN WERE ALLOWED TO FILL IN THE FOUNDRY. - Stockham Pipe & Fittings Company, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

Three Types of Earth's Inner Core Boundary

NASA Astrophysics Data System (ADS)

Tian, D.; Wen, L.

2017-12-01

The Earth's inner core boundary (ICB) is the site where the liquid outer core solidifies and the solid inner core grows. Thus, the fine-scale structure of the ICB is important for our understanding of the thermo-compositional state of the Earth's core. In this study, we collect a large set of seismic records with high-quality pre-critical PKiKP and PcP phase pairs, recorded by two dense seismic arrays, Hi-net in Japan and USArray in US. This dataset samples the ICB regions beneath East Asia, Mexico and the Bering Sea. We use differential travel times, amplitude ratios and waveform differences between PKiKP and PcP phases to constrain fine-scale structure of the ICB. The sampled ICB can be grouped into three types based on their seismic characteristics: (1) a simple ICB with a flat and sharp boundary, (2) a bumpy ICB with topographic height changes of 10 km, and (3) a localized mushy ICB with laterally varying thicknesses of 4-8 km. The laterally varying fine-scale structure of the ICB indicates existence of complex small-scale forces at the surface and a laterally varying solidification process of the inner core due to lateral variation of thermo-compositional condition near the ICB.

Characterization of minerals in natural and manufactured sand in Cauvery River belt, Tamilnadu, India

NASA Astrophysics Data System (ADS)

Gnanasaravanan, S.; Rajkumar, P.

2013-05-01

The present study investigates the characterization of minerals in the River Sand (R - Sand) and the Manufactured sand (M-Sand) through FTIR spectroscopic studies. The R - Sand is collected from seven different locations in Cauvery River and M - Sand is collected from eight different manufactures around the Cauvery River belt in Salem, Erode, Tirupur and Namakkal districts of Tamilnadu, India. To extend the effectiveness of the analysis, the samples were subjected to grain size separation to classify the bulk samples into different grain sizes. All the samples were analyzed using FTIR spectrometer. The number of minerals identified with the help of FTIR spectra in overall (bulk) samples of R - Sand is 14 and of M - Sand is 13. The number has been increased while going for grain size separation, i.e., from 14 to 31 for R - Sand and from 13 to 20 for M - Sand. Among all minerals, quartz plays a major role. The relative distribution and the crystallinity nature of quartz have been discussed based on the extinction co-efficient and the crystallinity index values computed. There is no major variation found in M - Sand while going for grain size separation.

Dendrogeochronologic and Anatomic Analysis of Excavated Plains Cottonwoods Determine Overbank Sedimentation Rates and Historical Channel Positions Along the Interior of a Migrating Meander Bend, Powder River, Montana

NASA Astrophysics Data System (ADS)

Metzger, T. L.; Pizzuto, J. E.; Schook, D. M.; Hasse, T. R.; Affinito, R. A.

2017-12-01

Dendrochronological dating of buried trees precisely determines the germination year and identifies the stratigraphic context of germination for the trees. This recently developed application of dendrochronology provides accurate time-averaged sedimentation rates of overbank deposition along floodplains and can be used to identify burial events. Previous studies have demonstrated that tamarisk (Tamarix ramosissima) and sandbar willow (Salix exigua) develop anatomical changes within the tree rings (increased vessel size and decreased ring widths) on burial, but observations of plains cottonwood (Populus deltoides ssp. monilifera) are lacking. In September 2016 and June 2017, five buried plains cottonwoods were excavated along a single transect of the interior of a meander bend of the Powder River, Montana. Sediment samples were obtained near each tree for 210Pb and 137Cs dating, which will allow for comparison between dendrochronological and isotopic dating methods. The plains cottonwood samples collected exhibit anatomical changes associated with burial events that are observed in other species. All trees germinated at the boundary between thinly bedded fine sand and mud and coarse sand underlain by sand and gravel, indicating plains cottonwoods germinate on top of point bars prior to overbank deposition. The precise germination age and depth provide elevations and minimum age constraints for the point bar deposits and maximum ages for the overlying sediment, helping constrain past channel positions and overbank deposition rates. Germination years of the excavated trees, estimated from cores taken 1.5 m above ground level, range from 2014 to 1862. Accurate establishment years determined by cross-dating the buried section of the tree can add an additional 10 years to the cored age. The sedimentation rate and accumulation thickness varied with tree age. The germination year, total sediment accumulation, and average sedimentation rate at the five sampled trees is: 2011, 35 cm, 7.0 cm/year; 1973, 77 cm, 1.8 cm/year; 1962, 140 cm, 2.6 cm/year; 1960, 123 cm, 2.2 cm/year; and 1862, 112 cm, 0.7 cm/year. These sedimentation rates indicate that the cumulative sedimentation decreases as a power law with increasing tree age.

Evolution of the Middle Bengal Fan at 8°N in the Oligocene to Pliocene - Preliminary Results from IODP Expedition 354

NASA Astrophysics Data System (ADS)

Volkhard, Spiess; Tilmann, Schwenk; Fenna, Bergmann; Christian, France-Lanord; Adam, Klaus

2016-04-01

Three deep penetration and additional four shallow sites were drilled during IODP Expedition 354 in the Bay of Bengal at 8°N in February-March 2015 across a 320 km-long transect to study Neogene Bengal fan deposition. The three deeper sites located on top of the elevated crustal features of the Ninetyeast Ridge (Site U1451) and 85°Ridge (Site U1455/DSDP Site 218) as well as central between them (Site U1450) shall provide the stratigraphic framework for the Oligocene to Pliocene reconstruction of fan deposition and sedimentary fluxes driven by monsoon evolution and Himalayan erosion and weathering. Based on shipboard biostratigraphy, drilled material reach back in geologic time to the late Miocene (Site U1450), middle Miocene (Site U1455) and Oligocene (Site U1451). While core recovery was generally severely reduced due to the presence of unconsolidated sand and silt units, half-length APC coring technology provided valuable sand samples/recovery down to ~800 meters below seafloor. Increased compaction/diagenesis of units indicating the temporary absence of fan deposition due to major depocenter shifts, comprising of calcarous clay units of mostly pelagic origin, required a change to rotary coring between 600 and 800 mbsf, and thus the presence of sand is mostly uncertain for those deeper sections. However, derived from penetration rates, a high proportion of sand is anticipated back to early Miocene or Oligocene times. The calcareous clay units serve as stratigraphic marker horizons, which turned out to be suitable for seismic correlation across the drilling transect. This in turn allows to determine sedimentary budgets and overall fan growth for numerous time slices. Recovered sediments have Himalayan mineralogical and geochemical signatures suitable to analyze time series of erosion, weathering and changes in source regions as well as impacts on the global carbon cycle. Miocene shifts in terrestrial vegetation, in sediment budget and in style of sediment transport have been tracked. Moderate sedimentation rates. Preliminary seismic stratigraphy also reveals that crustal features evolved since the Miocene thus confining pathways for turbidite transport. The onset of channel-levee structures indentified since ~10 Ma in the seismic records, is correlated with an increase in sediment flux from moderate rates on the order of 30 m/m.y. to an order of magnitude high accumulation rates during phases of sand lobe deposition and levee growth. Expedition 354 has extended the record of early fan deposition by 10 Ma into the Late Oligocene.

Etude de l'impact des barrages sur la réduction des transports sédimentaires jusqu'à la mer par approche paléohydrologique dans la basse vallée de la Medjerda

NASA Astrophysics Data System (ADS)

Kotti, Fatma; Dezileau, Laurent; Mahé, Gil; Habaieb, Hamadi; Bentkaya, Malik; Dieulin, Claudine; Amrouni, Oula

2018-04-01

The sedimentary contributions of the Medjerda to the coastal zone are poorly measured, and there is no chronicle of observations. In this context, the sediment monitoring appears indispensable for the quantification of sediment transport at the outlet. This study focuses on the largest watershed in Tunisia, the Wadi Medjerda (23 600 km2). The main objective of this work is to assess the reduction of sediment transport following anthropogenic intensification on the basin, especially since the construction of many large dams. In order to collect information on actual deposits over several years, the paleo-hydrological approach was applied through the study of sediment cores sampled in the low valley meanders on alluvial terraces, after the last dam (Sidi Salem, the largest water storage capacity over the basin), but before the estuary to avoid marine influence and near a hydrological station (Jdaida). The sedimentary deposits of the river provide key information on the past sedimentary inputs. A visible succession of sedimentary layers corresponding to the deposits of successive floods on the study site has been determined and the history of the sedimentary contributions of the Medjerda is reconstructed by this approach. The thickest layers of sedimentary deposits are related to exceptional events. They are mainly concentrated on the lower part of the core and are mainly composed of sands. The first 1.2 m of the core from the bottom upward relates to 10 years of river discharges, as can be determined from the 137Cs datation. The next upward 1.05 m of core relates to the following 20 years of discharges, up to 1981, date of the construction of the Sidi Salem dam, and is composed of a mix of sand, silts and clays. The last 75 cm of core near the surface is only composed of clays with thin silt bands, and relates to a period of 32 years. We thus observe that there is no more sand deposits in the river bed since the construction of the Sidi Salem dam. The deficit of sediment supply to the sea is viewed as a major factor to be taken into account for better understanding of the dynamics of coastal areas in the context of global climate change.

Assessment of different bedding systems for lactating cows in freestall housing

USDA-ARS?s Scientific Manuscript database

The objective of this study was to compare different bedding systems for lactating cows in freestall housing. Bedding systems included new sand (NS), recycled byproducts of manure separation (organic solids [OS] and recycled sand [RS]), and foam-core mattresses with a shallow layer of OS (MS). The e...

PIXE analysis of sand and soil from Ulaanbaatar and Karakurum, Mongolia

NASA Astrophysics Data System (ADS)

Markwitz, A.; Barry, B.; Shagjjamba, D.

2008-09-01

Twenty-one sand and soil samples were collected at the surface from 22 to 25 June 2007 at sampling sites from Ulaanbaatar to Karakurum, Mongolia. The sand samples were collected from constantly changing sand dunes which may still contain salt from prehistoric oceans. The dry sand and soil samples were processed for PIXE and PIGE analyses. A clear division between soils and sand become apparent in the silicon results. Concentrations of all bulk elements in human habitation samples and of Si, Al, K and Fe in dry lake/flood plain samples are similar to those in the soils and sands. Among elements which could be regarded as being at trace concentrations the average S concentration in the soils is 0.9 g kg-1 whereas it is not detected in the sand samples. Zinc and Cu concentrations are both higher in the soils than the sands and are strongly correlated. A surprising presence of uranium at a concentration of 350 mg kg-1 was detected in the PIXE measurement on one of the dry lake samples. Gamma spectrometry confirmed the presence of U in this sample and also at a lower level in a sample from the lake shore, but in none of the other samples. Further, the gamma spectrometry showed that 238U decay products were present only at a level corresponding to about 3 mg kg-1 U for a system in radioactive equilibrium, a figure which is typical for U in the earth's crust. Disequilibria between 238U and its decay products occur naturally but such a high degree of separation at high concentration would be unique if confirmed. PIXE and PIGE measurements of these samples highlight the difficulty in correlating trace element measurements with occurrence of indicators of sea salt in air particulate samples.

MAHLI at the Rocknest sand shadow: Science and science-enabling activities

NASA Astrophysics Data System (ADS)

Minitti, M. E.; Kah, L. C.; Yingst, R. A.; Edgett, K. S.; Anderson, R. C.; Beegle, L. W.; Carsten, J. L.; Deen, R. G.; Goetz, W.; Hardgrove, C.; Harker, D. E.; Herkenhoff, K. E.; Hurowitz, J. A.; Jandura, L.; Kennedy, M. R.; Kocurek, G.; Krezoski, G. M.; Kuhn, S. R.; Limonadi, D.; Lipkaman, L.; Madsen, M. B.; Olson, T. S.; Robinson, M. L.; Rowland, S. K.; Rubin, D. M.; Seybold, C.; Schieber, J.; Schmidt, M.; Sumner, D. Y.; Tompkins, V. V.; Van Beek, J. K.; Van Beek, T.

2013-11-01

Martian solar days 57-100, the Mars Science Laboratory Curiosity rover acquired and processed a solid (sediment) sample and analyzed its mineralogy and geochemistry with the Chemistry and Mineralogy and Sample Analysis at Mars instruments. An aeolian deposit—herein referred to as the Rocknest sand shadow—was inferred to represent a global average soil composition and selected for study to facilitate integration of analytical results with observations from earlier missions. During first-time activities, the Mars Hand Lens Imager (MAHLI) was used to support both science and engineering activities related to sample assessment, collection, and delivery. Here we report on MAHLI activities that directly supported sample analysis and provide MAHLI observations regarding the grain-scale characteristics of the Rocknest sand shadow. MAHLI imaging confirms that the Rocknest sand shadow is one of a family of bimodal aeolian accumulations on Mars—similar to the coarse-grained ripples interrogated by the Mars Exploration Rovers Spirit and Opportunity—in which a surface veneer of coarse-grained sediment stabilizes predominantly fine-grained sediment of the deposit interior. The similarity in grain size distribution of these geographically disparate deposits support the widespread occurrence of bimodal aeolian transport on Mars. We suggest that preservation of bimodal aeolian deposits may be characteristic of regions of active deflation, where winnowing of the fine-sediment fraction results in a relatively low sediment load and a preferential increase in the coarse-grained fraction of the sediment load. The compositional similarity of Martian aeolian deposits supports the potential for global redistribution of fine-grained components, combined with potential local contributions.

Reservoir characteristics of two minter oil sands based on continuous core, E-logs, and geochemical data: Bee Brake field, East-Central Louisiana

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

Echols, J.B.; Goddard, D.A.; Bouma, A.

The Bee Brake field area, located in township 4N/6E and 4N/7E in Concordia Parish, has been one of the more prolific oil-producing areas in east-central Louisiana. Production decline in various fields, however, has sparked interest in the economic feasibility of locating and producing the remaining bypassed oil in the lower Wilcox. For this purpose, the Angelina BBF No. 1 well was drilled, and a 500-ft conventional core and a complete suite of state-of-the-are wireline logs were recovered. Production tests were run on the Minter interval of interest. The 16-ft Minter interval (6742-6758 ft depth), bounded at its top and basemore » by lignite seams, consists of an upper 4-ft oil sand (Bee Brake) and a lower 3-ft oil sand (Angelina). The oil sands are separated by approximately 5 ft of thinly laminated silty shale and 4 ft of very fine-grained silty sandstone. Detailed sedimentologic and petrographic descriptions of the Minter interval provide accurate facies determinations of this lower delta-plain sequence. Petrophysical evaluation, combining core plug and modern electric-log data show differences between reservoir quality of the Bee Brake and Angelina sands. This data will also be useful for correlating and interpolating old electric logs. Organic geochemistry of the oil, lignites, and shales provides insight as to the source of the Minter oils and the sourcing potential of the lignites.« less

Comparison of Cottonwood Dendrochronology and Optically Stimulated Luminescence Geochronometers Along a High Plains Meandering River, Powder River, Montana, USA

NASA Astrophysics Data System (ADS)

Hasse, T. R.; Schook, D. M.

2017-12-01

Geochronometers at centennial scales can aid our understanding of process rates in fluvial geomorphology. Plains cottonwood trees (Populus deltoides ssp. Monilifera) in the high plains of the United States are known to germinate on freshly created deposits such as point bars adjacent to rivers. As the trees mature they may be partially buried (up to a few meters) by additional flood deposits. Cottonwood age gives a minimum age estimate of the stratigraphic surface where the tree germinated and a maximum age estimate for overlying sediments, providing quantitative data on rates of river migration and sediment accumulation. Optically Stimulated Luminescence (OSL) of sand grains can be used to estimate the time since the sand grains were last exposed to sunlight, also giving a minimum age estimate of sediment burial. Both methods have disadvantages: Browsing, partial burial, and other damage to young cottonwoods can increase the time required for the tree to reach a height where it can be sampled with a tree corer, making the germination point a few years to a few decades older than the measured tree age; fluvial OSL samples can have inherited age (when the OSL age is older than the burial age) if the sediment was not completely bleached prior to burial. We collected OSL samples at 8 eroding banks of the Powder River Montana, and tree cores at breast height (±1.2 m) from cottonwood trees growing on the floodplain adjacent to the OSL sample locations. Using the Minimum Age Model (MAM) we found that OSL ages appear to be 500 to 1,000 years older than the adjacent cottonwood trees which range in age (at breast height) from 60 to 185 years. Three explanations for this apparent anomaly in ages are explored. Samples for OSL could be below a stratigraphic unconformity relative to the cottonwood germination elevation. Shallow samples for OSL could be affected by anthropogenic mixing of sediments due to plowing and leveling of hay fields. The OSL samples could have significant inherited ages due to partial bleaching during sediment transport in this high plains river with high suspended sediment loads. The dendrochronology of the adjacent cottonwood trees then offers an independent measurement of the inherited age of the OSL samples.

The distribution of dragonfly larvae in a South Carolina stream: relationships with sediment type, body size, and the presence of other larvae.

PubMed

Worthen, Wade B; Horacek, Henry Joseph

2015-01-01

Dragonfly larvae were sampled in Little Creek, Greenville, SC. The distributions of five common species were described relative to sediment type, body size, and the presence of other larvae. In total, 337 quadrats (1 m by 0.5 m) were sampled by kick seine. For each quadrat, the substrate was classified as sand, sand-cobble mix, cobble, coarse, or rock, and water depth and distance from bank were measured. Larvae were identified to species, and the lengths of the body, head, and metafemur were measured. Species were distributed differently across sediment types: sanddragons, Progomphus obscurus (Rambur) (Odonata: Gomphidae), were common in sand; twin-spotted spiketails, Cordulegaster maculata Selys (Odonata: Cordulegastridae), preferred a sand-cobble mix; Maine snaketails, Ophiogomphus mainensis Packard (Odonata: Gomphidae), preferred cobble and coarse sediments; fawn darners, Boyeria vinosa (Say) (Odonata: Aeshnidae), preferred coarse sediments; and Eastern least clubtails, Stylogomphus albistylus (Hagen) (Odonata: Gomphidae), preferred coarse and rock sediments. P. obscurus and C. maculata co-occurred more frequently than expected by chance, as did O. mainensis, B. vinosa, and S. albistylus. Mean size varied among species, and species preferences contributed to differences in mean size across sediment types. There were significant negative associations among larval size classes: small larvae (<12 mm) occurred less frequently with large larvae (>15 mm) than expected by chance, and large larvae were alone in quadrats more frequently than other size classes. Species may select habitats at a large scale based on sediment type and their functional morphology, but small scale distributions are consistent with competitive displacement or intraguild predation. © The Author 2015. Published by Oxford University Press on behalf of the Entomological Society of America.

Coastal geology and recent origins for Sand Point, Lake Superior

USGS Publications Warehouse

Fisher, Timothy G.; Krantz, David E.; Castaneda, Mario R.; Loope, Walter L.; Jol, Harry M.; Goble, Ronald J.; Higley, Melinda C.; DeWald, Samantha; Hansen, Paul

2014-01-01

Sand Point is a small cuspate foreland located along the southeastern shore of Lake Superior within Pictured Rocks National Lakeshore near Munising, Michigan. Park managers’ concerns for the integrity of historic buildings at the northern periphery of the point during the rising lake levels in the mid-1980s greatly elevated the priority of research into the geomorphic history and age of Sand Point. To pursue this priority, we recovered sediment cores from four ponds on Sand Point, assessed subsurface stratigraphy onshore and offshore using geophysical techniques, and interpreted the chronology of events using radiocarbon and luminescence dating. Sand Point formed at the southwest edge of a subaqueous platform whose base is probably constructed of glacial diamicton and outwash. During the post-glacial Nipissing Transgression, the base was mantled with sand derived from erosion of adjacent sandstone cliffs. An aerial photograph time sequence, 1939–present, shows that the periphery of the platform has evolved considerably during historical time, infl uenced by transport of sediment into adjacent South Bay. Shallow seismic refl ections suggest slump blocks along the leading edge of the platform. Light detection and ranging (LiDAR) and shallow seismic refl ections to the northwest of the platform reveal large sand waves within a deep (12 m) channel produced by currents fl owing episodically to the northeast into Lake Superior. Ground-penetrating radar profi les show transport and deposition of sand across the upper surface of the platform. Basal radiocarbon dates from ponds between subaerial beach ridges range in age from 540 to 910 cal yr B.P., suggesting that Sand Point became emergent during the last ~1000 years, upon the separation of Lake Superior from Lakes Huron and Michigan. However, optically stimulated luminescence (OSL) ages from the beach ridges were two to three times as old as the radiocarbon ages, implying that emergence of Sand Point may have begun earlier, ~2000 years ago. The age discrepancy appears to be the result of incomplete bleaching of the quartz grains and an exceptionally low paleodose rate for the OSL samples. Given the available data, the younger ages from the radiocarbon analyses are preferred, but further work is necessary to test the two age models.

A novel bench-scale column assay to investigate site-specific nitrification biokinetics in biological rapid sand filters.

PubMed

Tatari, K; Smets, B F; Albrechtsen, H-J

2013-10-15

A bench-scale assay was developed to obtain site-specific nitrification biokinetic information from biological rapid sand filters employed in groundwater treatment. The experimental set-up uses granular material subsampled from a full-scale filter, packed in a column, and operated with controlled and continuous hydraulic and ammonium loading. Flowrates and flow recirculation around the column are chosen to mimic full-scale hydrodynamic conditions, and minimize axial gradients. A reference ammonium loading rate is calculated based on the average loading experienced in the active zone of the full-scale filter. Effluent concentrations of ammonium are analyzed when the bench-scale column is subject to reference loading, from which removal rates are calculated. Subsequently, removal rates above the reference loading are measured by imposing short-term loading variations. A critical loading rate corresponding to the maximum removal rate can be inferred. The assay was successfully applied to characterize biokinetic behavior from a test rapid sand filter; removal rates at reference loading matched those observed from full-scale observations, while a maximum removal capacity of 6.9 g NH4(+)-N/m(3) packed sand/h could easily be determined at 7.5 g NH4(+)-N/m(3) packed sand/h. This assay, with conditions reflecting full-scale observations, and where the biological activity is subject to minimal physical disturbance, provides a simple and fast, yet powerful tool to gain insight in nitrification kinetics in rapid sand filters. Copyright © 2013 Elsevier Ltd. All rights reserved.

Surface sediment remobilization triggered by earthquakes in the Nankai forearc region

NASA Astrophysics Data System (ADS)

Okutsu, N.; Ashi, J.; Yamaguchi, A.; Irino, T.; Ikehara, K.; Kanamatsu, T.; Suganuma, Y.; Murayama, M.

2017-12-01

Submarine landslides triggered by earthquakes generate turbidity currents (e.g. Piper et al., 1988; 1999). Recently several studies report that the remobilization of the surface sediment triggered by earthquakes can also generate turbidity currents. However, studies that proposed such process are still limited (e.g. Ikehara et al., 2016; Mchugh et al., 2016; Moernaut et al., 2017). The purpose of this study is to examine those sedimentary processes in the Nankai forearc region, SW Japan using sedimentary records. We collected 46 cm-long multiple core (MC01) and a 6.7 m-long piston core (PC03) from the small basin during the R/V Shinsei Maru KS-14-8 cruise. The small confined basin, which is our study site, block the paths of direct sediment supply from river-submarine canyon system. The sampling site is located at the ENE-WSW elongated basin between the accretionary prism and the forearc basin off Kumano without direct sediment supply from river-submarine canyon system. The basin exhibits a confined basin that captures almost of sediments supplied from outside. Core samples are mainly composed of silty clay or very fine sand. Cs-137 measurement conducted on a MC01 core shows constantly high value at the upper 17 cm section and no detection below it. Moreover, the sedimentary structure is similar to fine-grained turbidite described by Stow and Shanmgam (1980), we interpret the upper 17 cm of MC01 as muddy turbidite. Grain size distribution and magnetic susceptibility also agree to this interpretation. Rapid sediment deposition after 1950 is assumed and the most likely event is the 2004 off Kii peninsula earthquakes (Mw=6.6-7.4). By calculation from extent of provenance area, which are estimated by paleocurrent analysis and bathymetric map, and thickness of turbidite layer we conclude that surface 1 cm of slope sediments may be remobilized by the 2004 earthquakes. Muddy turbidites are also identified in a PC03 core. The radiocarbon age gap of 170 years obtained around 2 mbsf of PC03 core also indicates similar sedimentary process. However, we also obtained large age gap in a thick turbidite layer, indicating remobilization of deeper sediments by landslide. Our results revealed that the studied basin recorded various scales and styles of sediment remobilizations by earthquake shakings.

Pore Water Transport of Enterococci out of Beach Sediments

PubMed Central

Phillips, Matthew C.; Solo-Gabriele, Helena M.; Reniers, Adrianus J. H. M.; Wang, John D.; Kiger, Russell T.; Abdel-Mottaleb, Noha

2011-01-01

Enterococci are used to evaluate the safety of beach waters and studies have identified beach sands as a source of these bacteria. In order to study and quantify the release of microbes from beach sediments, flow column systems were built to evaluate flow of pore water out of beach sediments. Results show a peak in enterococci (average of 10% of the total microbes in core) released from the sand core within one pore water volume followed by a marked decline to below detection. These results indicate that few enterococci are easily removed and that factors other than simple pore water flow control the release of the majority of enterococci within beach sediments. A significantly larger quantity and release of enterococci were observed in cores collected after a significant rain event suggesting the influx of fresh water can alter the release pattern as compared to cores with no antecedent rainfall. PMID:21945015

Sediment data collected in 2012 from the northern Chandeleur Islands, Louisiana

USGS Publications Warehouse

Bernier, Julie C.; Kelso, Kyle W.; Buster, Noreen A.; Flocks, James G.; Miselis, Jennifer L.; DeWitt, Nancy T.

2014-01-01

As part of the Barrier Island Evolution Research project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center collected sediment samples from the northern Chandeleur Islands in March and September 2012. The overall objective of this project, which integrates geophysical (bathymetric, seismic, and topographic) and sedimentologic data, is to better understand the depositional and erosional processes that drive the morphologic evolution of barrier islands over annual to interannual timescales (1 to 5 years). Between June 2010 and April 2011, in response to the Deepwater Horizon oil spill, the State of Louisiana constructed a sand berm extending more than 14 kilometers along the northern Chandeleur Islands platform. The construction of the berm provided a unique opportunity to investigate how this new sediment source will interact with and affect the morphologic evolution of the barrier-island system. Data collected from this study will be used to describe differences in the physical characteristics and spatial distribution of sediments both along the axis of the berm and also along transects across the berm and onto the adjacent barrier island. Comparison of these data with data from subsequent sampling efforts will provide information about sediment interactions and movement between the berm and the natural island platform, improving our understanding of short-term morphologic change and processes in this barrier-island system. This data series serves as an archive of sediment data collected in March and September 2012 from the Chandeleur Islands sand berm and adjacent barrier-island environments. Data products include descriptive core logs, core photographs and x-radiographs, results of sediment grain-size analyses, sample location maps, and Geographic Information System data files with accompanying formal Federal Geographic Data Committee metadata.

Preliminary Micropaleontological Investigation of a Preserved, Late Pleistocene Cypress Forest on the Northern Gulf of Mexico Inner Shelf

NASA Astrophysics Data System (ADS)

Truong, J. T.; DeLong, K. L.; Bentley, S. J.; Xu, K.; Harley, G. L.; Reese, A.; Gonzalez, S.; Obelcz, J.; Caporaso, A.

2017-12-01

Exposed at the bottom of a trough 13 km offshore Orange Beach, AL on the Gulf of Mexico (GOM) shelf in 18 m water depth are exceptionally preserved in situ bald cypress (Taxodium distichum) stumps. Preserved seeds (T. distichum, Cephalanthus occidentalis, Hibiscus lasiocarpos, Liquidambar styraciflua) discovered in core catcher samples illustrate the exceptional preservation of the site. Woody debris samples have come back radiocarbon dead with an exception to samples located in the upper peat layer with 14C ages from 37,350-41,830 years BP. Optically stimulated luminescence and 14C dates, in combination with GOM eustatic sea level curves, suggest the forest was located 30 m above the paleoshoreline. How the forest remained preserved during subaerial exposure of the continental shelf through the Last Glacial Maximum lowstand until ensuing Holocene sea level transgression remains unknown. The R/V Coastal Profiler collected 7 vibracores from the study site in 2015 and an additional 11 in 2016. A single core (DF1) contains facies identified as the Holocene Mississippi-Alabama-Florida sand sheet, a transitional facies of interbedded sand and mud, and a basal floodplain facies in which the stumps reside. This study seeks to identify the location of the Pleistocene-Holocene unconformity and to assist in stratigraphy of the area. Foraminiferal assemblages found within the transitional facies are of a shallow marine environment that suggests Holocene in age. It is hypothesized that a pulse of sea level rise during Marine Isotope Stages 3-4 caused subsequent rapid aggradation of the paleovalley system allowing for preservation through >30 kyrs of subaerial exposure. One of the ultimate goals of this study is to serve as a guide for identification of other possible sites along the gulf coast.

U-Pb Geochronology of non-marine Upper Triassic strata of the Colorado Plateau (western North America): implications for stratigraphic correlation and paleoenvironmental reconstruction

NASA Astrophysics Data System (ADS)

Rasmussen, C.; Mundil, R.; Irmis, R. B.; Keller, C. B.; Giesler, D.; Gehrels, G. E.

2017-12-01

The Triassic is a critical period in Earth history that witnessed the origin of modern ecosystems and frequent climate fluctuations, as well as major environmental events such as flood basalt volcanism and bolide impacts. The Chinle Formation contains a primary non-marine archive for past ecosystems in North America due to its fossil richness and well-studied sedimentology. Moreover, within these highly fossiliferous strata, a biotic turnover has been reported that has been hypothesized to coincide with one or more of the aforementioned environmental events. Unfortunately, few radioisotopic ages have been published for the Late Triassic, limiting our ability for lithological and paleoenvironmental correlations. In addition, the superposition of the Chinle Formation remains illusive due to frequent lateral facies changes and discontinuous outcrops across the Colorado Plateau. The 520 m long core 1A of the Colorado Plateau Coring Project from Petrified Forest National Park (PFNP) (Arizona) provides, for the first time, a continuous section of these early Mesozoic sedimentary strata. Many of the sand- and siltstones from this continuous succession throughout most of the Upper Triassic Chinle Formation contain euhedral zircons suitable for U-Pb analyses. We analyzed >300 crystals each from 10 samples using LA-ICPMS; these results indicated abundant Late Triassic crystals that appear to be closely associated with the depositional age of the host rock. We then selected the youngest grains from these samples to obtain precise CA-TIMS U-Pb single zircon ages in order to constrain the maximum depositional ages (using quantitative methods) of these formations. We are able to revise the proposed time scale (based on outcrop samples) for Upper Triassic strata at PFNP and evaluate whether the biotic turnover observed within the Sonsela Member of these strata coincides with the Manicouagan bolide impact event. This revised chronostratigraphic framework allows intercalibration with the Newark astrochronostratigraphic polarity time scale and the correlation with other key non-marine and marine Late Triassic sections globally (e.g., Ischigualasto-Villa Uníon Basin, Argentina; Tethyan region, Europe) improving our understanding of paleoenvironmental and evolutionary changes during the Triassic.

Geochemical evidence for the provenance of aeolian deposits in the Qaidam Basin, Tibetan Plateau

NASA Astrophysics Data System (ADS)

Du, Shisong; Wu, Yongqiu; Tan, Lihua

2018-06-01

The main purpose of this study is to analyse the material source of different grain-size components of dune sand in the Qaidam Basin. We determined the trace and rare earth element (REE) compositions and Sr-Nd isotopic compositions of the coarse (75-500 μm) and fine (<75 μm) fractions of surface sediment samples. The comparison of the immobile trace element and REE compositions, Sr-Nd isotopic compositions and multidimensional scaling (MDS) results of the dune sands with those of different types of sediments in potential source areas revealed the following information. (1) The fine- and coarse-grained fractions of dune sands in the Qaidam Basin exhibit distinctly different elemental concentrations, elemental patterns and characteristic parameters of REE. Moreover, Sr-Nd isotopic differences also exist between different grain-size fractions of aeolian sand, which means that different grain-size fractions of these dune sands have different source areas. (2) The geochemical characteristics of the coarse particles of dune sand exhibit obvious regional heterogeneity and generally record a local origin derived from local fluvial sediments and alluvial/proluvial sediments. The coarse- and fine-grained dune sand in the southern Qaidam Basin mainly came from Kunlun Mountains, whereas the coarse- and fine-grained dune sand in the northeastern Qaidam Basin mainly came from Qilian Mountains. (3) The fine-grained fractions of sediments throughout the entire Qaidam Basin may have been affected by the input of foreign materials from the Tarim Basin.

Effect of Fractal Dimension on the Strain Behavior of Particulate Media

NASA Astrophysics Data System (ADS)

Altun, Selim; Sezer, Alper; Goktepe, A. Burak

2016-12-01

In this study, the influence of several fractal identifiers of granular materials on dynamic behavior of a flexible pavement structure as a particulate stratum is considered. Using experimental results and numerical methods as well, 15 different grain-shaped sands obtained from 5 different sources were analyzed as pavement base course materials. Image analyses were carried out by use of a stereomicroscope on 15 different samples to obtain quantitative particle shape information. Furthermore, triaxial compression tests were conducted to determine stress-strain and shear strength parameters of sands. Additionally, the dynamic response of the particulate media to standard traffic loads was computed using finite element modeling (FEM) technique. Using area-perimeter, line divider and box counting methods, over a hundred grains for each sand type were subjected to fractal analysis. Relationships among fractal dimension descriptors and dynamic strain levels were established for assessment of importance of shape descriptors of sands at various scales on the dynamic behavior. In this context, the advantage of fractal geometry concept to describe irregular and fractured shapes was used to characterize the sands used as base course materials. Results indicated that fractal identifiers can be preferred to analyze the effect of shape properties of sands on dynamic behavior of pavement base layers.

Porosity characterization for heterogeneous shales using integrated multiscale microscopy

NASA Astrophysics Data System (ADS)

Rassouli, F.; Andrew, M.; Zoback, M. D.

2016-12-01

Pore size distribution analysis plays a critical role in gas storage capacity and fluid transport characterization of shales. Study of the diverse distribution of pore size and structure in such low permeably rocks is withheld by the lack of tools to visualize the microstructural properties of shale rocks. In this paper we try to use multiple techniques to investigate the full pore size range in different sample scales. Modern imaging techniques are combined with routine analytical investigations (x-ray diffraction, thin section analysis and mercury porosimetry) to describe pore size distribution of shale samples from Haynesville formation in East Texas to generate a more holistic understanding of the porosity structure in shales, ranging from standard core plug down to nm scales. Standard 1" diameter core plug samples were first imaged using a Versa 3D x-ray microscope at lower resolutions. Then we pick several regions of interest (ROIs) with various micro-features (such as micro-cracks and high organic matters) in the rock samples to run higher resolution CT scans using a non-destructive interior tomography scans. After this step, we cut the samples and drill 5 mm diameter cores out of the selected ROIs. Then we rescan the samples to measure porosity distribution of the 5 mm cores. We repeat this step for samples with diameter of 1 mm being cut out of the 5 mm cores using a laser cutting machine. After comparing the pore structure and distribution of the samples measured form micro-CT analysis, we move to nano-scale imaging to capture the ultra-fine pores within the shale samples. At this stage, the diameter of the 1 mm samples will be milled down to 70 microns using the laser beam. We scan these samples in a nano-CT Ultra x-ray microscope and calculate the porosity of the samples by image segmentation methods. Finally, we use images collected from focused ion beam scanning electron microscopy (FIB-SEM) to be able to compare the results of porosity measurements from all different imaging techniques. These multi-scale characterization techniques are then compared with traditional analytical techniques such as Mercury Porosimetry.

The Late Holocene Stratigraphy of an Inlet-Dominated Barrier Island, Pea Island, North Carolina.

NASA Astrophysics Data System (ADS)

Smith, C. G.; Ames, D.; Corbett, D. R.; Culver, S.; Mallinson, D.; Riggs, S. R.; Vance, D.

2002-12-01

Sedimentological, foraminiferal, geochemical, and geophysical data sets as well as aerial photographs have been used to investigate the natural processes (inlet dynamics, ocean/estuarine washover, and sea-level change) responsible for the late Holocene units preserved in the barrier island subsurface at Pea Island National Wildlife Refuge. Historic nautical charts indicate that three inlets characterized Pea Island between early European exploration (1590) and the late 19th century; aerial photographs show New Inlet open in 1932 and 1940. Vibracores (up to 5.5 m) collected along three transects across Pea Island extend our knowledge of the geological evolution of this region to pre-historic times. The section in the longest core (PI01S6) consists of four fining-upwards depositional sequences. The basal unit of each sequence is a bedded, medium to fine, clean quartz sand with increasing concentrations of organic matter (3-4 % detrital and 5-7 % in situ Spartina alterniflora roots) or irregular mud clasts (2-5 cm) to spherical mud balls (1-2 cm) up core. The clean sand units have so far proven to be barren of foraminifera except for a shelly unit at ca. 220 cm below MSL. The foraminiferal assemblage in this unit is of open shelf character (Elphidium excavatum, Hanzawaia strattoni, and Buccella inusitata). A 14C age on a disarticulated Chione cancellata valve from this unit is cal. 930+/-60 BP. The sand grades into a gray, tight mud in the first two sequences and into an inter-laminated mud and in situ peat in the third sequence. The peat contains leaf fragments and rhizomes of the marsh plants Juncus roemarianus, Spartina cynosuroides, and/or Phragmites spp. The peat and muddy sand units contain marsh foraminifera (Trochammina spp., Miliammina fusca, Arenoparrella mexicana), which are also found in modern marsh deposits. A peat sample from the third fining upward sequence (the only one to grade into a true peat) has a 14C age of cal. 395+/-35 BP, cal. 295+/-35 BP, or cal 180+/-40 BP. The four fining-upwards sequences have sharp erosional basal contacts. These deposits appear to reflect back-barrier processes including sequential deposition of flood-tide delta sands and/or sound sands adjacent to marshes. The shelly sands, containing open shelf foraminiferal assemblages, represent oceanic overwash, inlet deposits, or open embayment sands deposited behind a laterally extensive breach in the barrier island. The sequences are capped by the deposits of modern environments that include algal flats, tidal creeks, high and low marshes, back-barrier berms, overwash fans, and aeolian dunes. Several of the modern environments became covered with marsh vegetation after the construction of barrier dune ridges in the late 1930?s.

Rates of carbonate soil evolution from carbon, U- and Th-series isotope studies: Example of the Astian sands (SE France)

NASA Astrophysics Data System (ADS)

Barbecot, Florent; Ghaleb, Bassam; Hillaire-Marcel, Claude

2015-04-01

In carbonate rich soils, C-isotopes (14C, 13C) and carbonate mass budget may inform on centennial to millennial time scale dissolution/precipitation processes and weathering rates, whereas disequilibria between in the U- and Th-decay series provide tools to document high- (228Ra-228Th-210Pb) to low- (234U, 230Th, 231Pa, 226Ra) geochemical processes rate, covering annual to ~ 1Ma time scales, governing both carbonate and silicate soil fractions. Because lithology constitutes a boundary condition, we intend to illustrate the behavior of such isotopes in soils developed over Astian sands formation (up to ~ 30% carbonate) from the Béziers area (SE France). A >20 m thick unsaturated zone was sampled firstly along a naturally exposed section, then in a cored sequence. Geochemical and mineralogical analyses, including stable isotopes and 14C-measurements, were complemented with 228U, 234U, 230Th, 226Ra, 210Pb and 228Th, 232Th measurements. Whereas the upper 7 m depict geochemical and isotopic features forced by dissolution/precipitation processes leading to variable radioactive disequilibria, but overall deficits in more soluble elements of the decay series, the lower part of the sequence shows strong excesses in 234U and 230Th over parent isotopes (i.e., 238U and 234U, respectively). These features might have been interpreted as the result of successive phases of U-loss and gains. However, 226Ra and 230Th are in near-equilibrium, thus leading to conclude at a more likely slow enrichment process in both 234Th(234U) and 230Th, which we link to dissolved U-decay during groundwater recharge events. In addition, 210Pb deficits (vs parent 226Ra) are observed down to 12 m along the natural outcropping section and below the top-soil 210Pb-excess in the cored sequence, due to gaseous 222Rn-diffusion over the cliff outcrop. Based on C-isotope and chemical analysis, reaction rates at 14C-time scale are distinct from those estimates at the short- or long-lived U-series isotopes, but provide a specific insight into carbonate budgets when confronted with data on dissolved and gaseous phases as well as on solid matter, and possibly best integrate the overall soil behavior through time. It is concluded from this example that if first order estimates of long-term geochemical fluxes in soils can be obtained from disequilibria in the 238U-234U-230Th sequence or from C-isotope data. While insights into recent to "Anthropocene" processes require information on the shorter-lived isotopes of the U and Th series, adding specific information on physical and chemical erosion budgets from 232Th data. As also illustrated in the present example, a robust assessment of overall chemical and physical erosion rates must be based on measurements in cored sequences away from natural or recent man-made cuts.

Remagnetization and Cementation of Unconsolidated Sediments in the Mallik 5L-38 Well (Canadian Arctic) by Solute Exclusion During Gas Hydrate Formation

NASA Astrophysics Data System (ADS)

Hamilton, T. S.; Enkin, R. J.; Esteban, L.

2007-05-01

Bulk magnetic properties provide a sensitive measure of sedimentary diagenesis related to the stability and growth of gas hydrates. The deposit at Mallik (Mackenzie Delta, Canadian Arctic) occurs in unconsolidated Tertiary sands, but is absent in interstratified silt layers. A detailed sampling of the JAPEX/JNOC/GSC Mallik 5L-38 core tested the use of magnetic properties for detecting diagenetic changes related to the hydrate. Petrographic studies reveal that the sands are well sorted and clean, with quartz > chert >> muscovite and little fines content. Excepting a few rare bands of indurated dolomite in the midst of the gas hydrate zone, there is little or no cementation in the sands. Detrital magnetite is the dominant magnetic mineral, comprising up to a few percent of the sand grain population. In contrast, the muddier layers have a somewhat different detrital grain composition, richer in lithic (sedimentary and metamorphic) grains, feldspar, and clays. They are extensively diagenetically altered (to as much as 30- 40%) and cemented with carbonates, clays, chlorite and the iron sulphide greigite (the dominant magnetic mineral). The greigite is recognized by its isotropic creamy-white reflectance, cubic to prismatic habit, and characteristic tarnish to faintly bluish bireflectant mackinawite. Habits range from disseminated cubes and colliform masses to inflationary massive sulphide veins and clots. Rare detrital grains of magnetite were observed among the silt grains, but never in a reaction relationship or overgrown. Instead the greigite has nucleated separately, in tensional fractures and granular masses up to 4 mm across. In this particular sediment sequence, being so quartz and chert rich, there is insufficient local source for the introduced cements (calcite, dolomite, greigite, clays, jarosite), so ions must have been introduced by fluid flow. Magnetic studies reveal a bi-modal character related to the lithology (sands versus silts) and their magnetic mineralogy. Silt samples are significantly stronger than sand samples in saturation magnetization and magnetic susceptibility. The silt samples have single-domain to pseudo-single domain coercivity ratios whereas the gas hydrate bearing sands have a more multi-domain nature. Sands with current gas hydrate concentrations > 80% have less magnetic material and single domain characteristics. The source of the greigite, carbonates, and other diagenetic minerals was apparently concentrated solutes excluded from formation waters by the freezing and formation of the water dominated gas hydrate. The hydrates served as a cementing agent for the unconsolidated sediments, allowing them to fracture. Some layers have been so inflated by the introduction carbonate and sulfide cements that they resemble hydrothermal tufa and skarns with floating sand grains. In the silts, the magnetic properties reflect the mixture of primary detrital magnetite and diagenetic greigite in various grain sizes and concentrations. At Mallik, the magnetic properties are sensitive to the diagenetic mineralogy and redox state associated with the transport of methane and pore fluids and the creation of gas hydrates. Hypersaline brines, produced by solute exclusion from pore waters, fractured and inflated less permeable sediments and forced rapid disequilibrium growth of greigite without dissolving primary detrital magnetite grains.

Transverse bacterial migration induced by chemotaxis in a packed column with structured physical heterogeneity.

PubMed

Wang, Meng; Ford, Roseanne M

2009-08-01

The significance of chemotaxis in directing bacterial migration toward contaminants in natural porous media was investigated under groundwater flow conditions. A laboratory-scale column, with a coarse-grained sand core surrounded by a fine-grained annulus, was used to simulate natural aquifers with strata of different hydraulic conductivities. A chemoattractant source was placed along the central axis of the column to model contaminants trapped in the heterogeneous subsurface. Chemotactic bacterial strains, Escherichia coli HCB1 and Pseudomonas putida F1, introduced into the column by a pulse injection, were found to alter their transport behaviors under the influence of the attractant chemical emanating from the central source. For E. coil HCB1, approximately 18% more of the total population relative to the control without attractant exited the column from the coarse sand layer due to the chemotactic effects of alpha-methylaspartate under an average fluid velocity of 5.1 m/d. Although P. putida F1 demonstrated no observable changes in migration pathways with the model contaminant acetate under the same flow rate, when the flow rate was reduced to 1.9 m/d, approximately 6-10% of the population relative to the control migrated from the fine sand layer toward attractant into the coarse sand layer. Microbial transport properties were further quantified by a mathematical model to examine the significance of bacterial motility and chemotaxis under different hydrodynamic conditions, which suggested important considerations for strain selection and practical operation of bioremediation schemes.

CHARACTERIZATION OF METAL ADSORPTION VARIABILITY IN A SAND & GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS, U.S.A.

EPA Science Inventory

Several geochemical properties of an aquifer sediment that control metal-ion adsorption were investigated to determine their potential use as indicators of the spatial variability of metal adsorption. Over the length of a 4.5-m-long core from a sand and gravel aquifer, lead (Pb2+...

MECHANISMS OF MICROBIAL MOVEMENT IN SUBSURFACE MATERIALS

EPA Science Inventory

The biological factors important in the penetration of Escherichia coli through anaerobic, nutrient-saturated, Ottawa sand-packed cores were studied under static conditions. In cores saturated with galactose-peptone medium, motile strains of E. coli penetrated four times faster t...

Plains South of Valles Marineris

NASA Image and Video Library

2017-03-28

This enhanced-color sample reveals the incredible diversity of landforms on some Martian plains that appear bland and uniform at larger scales. Here we see layers, small channels suggesting water flow, craters, and indurated sand dunes. The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25.7 centimeters (10.1 inches) per pixel (with 1 x 1 binning); objects on the order of 77 centimeters (30.3 inches) across are resolved.] North is up. http://photojournal.jpl.nasa.gov/catalog/PIA21573

Temporal changes in lithology and radiochemistry from the back-barrier environments along the Chandeleur Islands, Louisiana: March 2012-July 2013

USGS Publications Warehouse

Marot, Marci E.; Adams, C. Scott; Richwine, Kathryn A.; Smith, Christopher G.; Osterman, Lisa E.; Bernier, Julie C.

2014-01-01

Scientists from the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center conducted a time-series collection of shallow sediment cores from the back-barrier environments along the Chandeleur Islands, Louisiana from March 2012 through July 2013. The sampling efforts were part of a larger USGS study to evaluate effects on the geomorphology of the Chandeleur Islands following the construction of an artificial sand berm to reduce oil transport onto federally managed lands. The objective of this study was to evaluate the response of the back-barrier tidal and wetland environments to the berm. This report serves as an archive for sedimentological, radiochemical, and microbiological data derived from the sediment cores. Data are available for a time-series of four sampling periods: March 2012; July 2012; September 2012; and July 2013. Downloadable data are available as Excel spreadsheets and as JPEG files. Additional files include: ArcGIS shapefiles of the sampling sites, detailed results of sediment grain size analyses, and formal Federal Geographic Data Committee metadata.

Fractal Dimensionality of Pore and Grain Volume of a Siliciclastic Marine Sand

NASA Astrophysics Data System (ADS)

Reed, A. H.; Pandey, R. B.; Lavoie, D. L.

Three-dimensional (3D) spatial distributions of pore and grain volumes were determined from high-resolution computer tomography (CT) images of resin-impregnated marine sands. Using a linear gradient extrapolation method, cubic three-dimensional samples were constructed from two-dimensional CT images. Image porosity (0.37) was found to be consistent with the estimate of porosity by water weight loss technique (0.36). Scaling of the pore volume (Vp) with the linear size (L), V~LD provides the fractal dimensionalities of the pore volume (D=2.74+/-0.02) and grain volume (D=2.90+/-0.02) typical for sedimentary materials.

A field study of large-scale oscillation ripples in a very coarse-grained, high-energy marine environment

USGS Publications Warehouse

Hirschaut, D.W.; Dingler, J.R.

1982-01-01

Monastery Beach, Carmel, California is a pocket beach that sits within 200 m of the head of Carmel Submarine Canyon. Coarse to very coarse sand covers both the beach and adjacent shelf; in the latter area incoming waves have shaped the sand into large oscillation ripples. The accessibility of this area and a variable wave climate produce a unique opportunity to study large-scale coarse-grained ripples in a high-energy environment. These ripples, which only occur in very coarse sand, form under the intense, wave-generated currents that exist during storm conditions. Once formed, these ripples do not significantly change under lower energy waves. On three separate occasions scuba divers measured ripples and collected sand samples from ripple crests near fixed reference stakes along three transects. Ripple wavelength and grain size decreased with an increase in water depth. Sediment sorting was best closest to the surf zone and poorest at the rim of Carmel Canyon. Cobbles and gravel observed in ripple troughs represent lag deposits. Carmel Canyon refracts waves approaching Monastery Beach such that wave energy is focused towards the northern and southern portions of the beach, leaving the central part of the beach lower in energy. This energy distribution causes spatial variations in the ripples and grain sizes with the shortest wavelengths and smallest grain sizes being in the central part of the shelf.

Sediment lithology and radiochemistry from the back-barrier environments along the northern Chandeleur Islands, Louisiana—March 2012

USGS Publications Warehouse

Marot, Marci E.; Smith, Christopher G.; Adams, C. Scott; Richwine, Kathryn A.

2017-04-11

Scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center collected a set of 8 sediment cores from the back-barrier environments along the northern Chandeleur Islands, Louisiana, in March 2012. The sampling efforts were part of a larger USGS study to evaluate effects on the geomorphology of the Chandeleur Islands following the construction of an artificial sand berm to reduce oil transport onto federally managed lands. The objective of this study was to evaluate the response of the back-barrier tidal and wetland environments to the berm. This report serves as an archive for sedimentological and radiochemical data derived from the sediment cores. The data described in this report are available for download on the data downloads page.

Restoration in Sand-slugged Streams and Drought---the Granite Creeks Project.

NASA Astrophysics Data System (ADS)

Lake, P. S.; Bond, N.; Glaister, A.; Downes, B.

2005-05-01

European settlement, with accompanying land clearance and heavy grazing, of the Strathbogie Ranges in central Victoria, Australia, resulted in the massive export of sediment to lowland streams. These streams, originally configured as "chains of ponds", were filled with "sand slugs" that generated a raised flat streambed depleted in habitat heterogeneity. The invertebrate fauna of the sand slugs is similar to that of sandbed streams elsewhere, but lacks an abundant hyporheos. The fish fauna was reduced in diversity and abundance. In 2001 habitat restoration in the sand slugs commenced after pre-restoration samples were taken.Timber structures, made from railway sleepers, were installed and subsequently created scour pools. Fish responded positively to restoration measure, but no significant effect was apparent for the invertebrates. In 2001-2004 a very severe drought occurred causing the streams to cease to flow and in the sand-slugged sections faunal abundance declined greatly due to the loss of residential habitat and the lack of refugia. Thus, the large-scale effects of severe drought thwarted the effects of localized habitat restoration, stressing the point that in restoring habitat it is also imperative to generate resilience to the prevailing disturbance regime-a regime that may be exacerbated by human activities.

Magnetic Fabric Associated with Faulting of Poorly Consolidated Basin Sediments of the Rio Grande Rift, New Mexico, USA

NASA Astrophysics Data System (ADS)

Hudson, M. R.; Minor, S. A.; Caine, J. S.

2015-12-01

Permanent strain in sediments associated with shallow fault zones can be difficult to characterize. Anisotropy of magnetic susceptibility (AMS) data were obtained from 120 samples at 6 sites to assess the nature of fault-related AMS fabrics for 4 faults cutting Miocene-Pliocene basin fill sediments of the Rio Grande rift of north-central New Mexico. The San Ysidro (3 sites), Sand Hill, and West Paradise faults within the northern Albuquerque basin have normal offset whereas an unnamed fault near Buckman in the western Española basin has oblique strike-slip offset. Previous studies have shown that detrital magnetite controls magnetic susceptibility in rift sandstones, and in a 50-m-long hanging wall traverse of the San Ysidro fault, non-gouge samples have typical sedimentary AMS fabrics with Kmax and Kint axes (defining magnetic foliation) scattered within bedding. For the 5 normal-fault sites, samples from fault cores or adjacent mixed zones that lie within 1 m of the principal slip surface developed common deformation fabrics with (1) magnetic foliation inclined in the same azimuth but more shallowly dipping than the fault plane, and (2) magnetic lineation plunging down foliation dip with nearly the same trend as the fault striae, although nearer for sand versus clay gouge samples. These relations suggest that the sampled fault materials deformed by particulate flow with alignment of magnetite grains in the plane of maximum shortening. For a 2-m-long traverse at the Buckman site, horizontal sedimentary AMS foliation persists to < 15 cm to the fault slip surface, wherein foliation in sand and clay gouge rotates toward the steeply dipping fault plane in a sense consistent with sinistral offset. Collectively these data suggest permanent deformation fabrics were localized within < 1 m of fault surfaces and that AMS fabrics from gouge samples can provide kinematic information for faults in unconsolidated sediments which may lack associated slickenlines.

Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux.

PubMed

Ayoub, F; Avouac, J-P; Newman, C E; Richardson, M I; Lucas, A; Leprince, S; Bridges, N T

2014-09-30

Coupling between surface winds and saltation is a fundamental factor governing geological activity and climate on Mars. Saltation of sand is crucial for both erosion of the surface and dust lifting into the atmosphere. Wind tunnel experiments along with measurements from surface meteorology stations and modelling of wind speeds suggest that winds should only rarely move sand on Mars. However, evidence for currently active dune migration has recently accumulated. Crucially, the frequency of sand-moving events and the implied threshold wind stresses for saltation have remained unknown. Here we present detailed measurements of Nili Patera dune field based on High Resolution Imaging Science Experiment images, demonstrating that sand motion occurs daily throughout much of the year and that the resulting sand flux is strongly seasonal. Analysis of the seasonal sand flux variation suggests an effective threshold for sand motion for application to large-scale model wind fields (1-100 km scale) of τ(s)=0.01±0.0015 N m(-2).

Macroinvertebrate community sample collection methods and data collected from Sand Creek and Medano Creek, Great Sand Dunes National Park and Preserve, Colorado, 2005–07

USGS Publications Warehouse

Ford, Morgan A.; Zuellig, Robert E.; Walters, David M.; Bruce, James F.

2016-08-11

This report provides a table of site descriptions, sample information, and semiquantitative aquatic macroinvertebrate data from 105 samples collected between 2005 and 2007 from 7 stream sites within the Sand Creek and Medano Creek watersheds in Great Sand Dunes National Park and Preserve, Saguache County, Colorado. Additionally, a short description of sample collection methods and laboratory sample processing procedures is presented. These data were collected in anticipation of assessing the potential effects of fish toxicants on macroinvertebrates.

A Improved Seabed Surface Sand Sampling Device

NASA Astrophysics Data System (ADS)

Luo, X.

2017-12-01

In marine geology research it is necessary to obtain a suf fcient quantity of seabed surface samples, while also en- suring that the samples are in their original state. Currently,there are a number of seabed surface sampling devices available, but we fnd it is very diffcult to obtain sand samples using these devices, particularly when dealing with fne sand. Machine-controlled seabed surface sampling devices are also available, but generally unable to dive into deeper regions of water. To obtain larger quantities of seabed surface sand samples in their original states, many researchers have tried to improve upon sampling devices,but these efforts have generally produced ambiguous results, in our opinion.To resolve this issue, we have designed an improved andhighly effective seabed surface sand sampling device that incorporates the strengths of a variety of sampling devices. It is capable of diving into deepwater to obtain fne sand samples and is also suited for use in streams, rivers, lakes and seas with varying levels of depth (up to 100 m). This device can be used for geological mapping, underwater prospecting, geological engineering and ecological, environmental studies in both marine and terrestrial waters.

Variations in Grain-Scale Sediment Structure in a Gravel-Bed Channel as a Function of Fine Sediment Content and Morphological Location

NASA Astrophysics Data System (ADS)

Voepel, H.; Ahmed, S. I.; Hodge, R. A.; Leyland, J.; Sear, D. A.

2016-12-01

One of the major causes of uncertainty in estimates of bedload transport rates in gravel bed rivers is a lack of understanding of grain-scale sediment structure, and the impact that this structure has on bed stability. Furthermore, grain-scale structure varies throughout a channel and over time in ways that have not been fully quantified. Our research aims to quantify variations in sediment structure caused by two key variables; morphological location within a riffle-pool sequence (reflecting variation in hydraulic conditions), and the fine sediment content of the gravel bed (sand and clay). We report results from a series of flume experiments in which we water-worked a gravel bed with a riffle-pool morphology. The fine sediment content of the bed was incrementally increased over a series of runs from gravel only, to coarse sand, fine sand and two concentrations of clay. After each experimental run intact samples of the bed at different locations were extracted and the internal structure of the bed was measured using non-destructive, micro-focus X-ray computed tomography (CT) imaging. The CT images were processed to measure the properties of individual grains, including volume, center of mass, dimension, and contact points. From these data we were able to quantify the sediment structure through metrics including measurement of grain pivot angles, grain exposure and protrusion, and vertical variation in bed porosity and fine sediment content. Metrics derived from the CT data were verified using data from grain counts and tilt-table measurements on co-located samples. Comparison of the metrics across different morphological locations and fine sediment content demonstrates how these factors affect the bed structure. These results have implications for the development of sediment entrainment models for gravel bed rivers.

Sedimentologic characteristics of recent washover deposits from Assateague Island, Maryland

USGS Publications Warehouse

Bernier, Julie C.; Zaremba, Nicholas J.; Wheaton, Cathryn J.; Ellis, Alisha M.; Marot, Marci E.; Smith, Christopher G.

2016-06-08

This report describes sediment data collected using sand augers in active overwash zones on Assateague Island in Maryland. Samples were collected by the U.S. Geological Survey (USGS) during two surveys in March/April and October 2014 (USGS Field Activity Numbers [FAN] 2014-301-FA and 2014-322-FA, respectively). The physical characteristics (for example, sediment texture or bedding structure) of and spatial differences among these deposits will provide information about overwash processes and sediment transport from the sandy barrier-island reaches to the back-barrier environments. Metrics derived from these data, such as mean grain size or deposit thicknesses, can be used to ground-truth remote sensing and geophysical data and can also be incorporated into sediment transport models. Data products, including sample location tables, descriptive core logs, core photographs and x-radiographs, the results of sediment grain-size analyses, and Geographic Information System (GIS) data files with accompanying formal Federal Geographic Data Committee (FGDC) metadata can be downloaded from the Data Downloads page.

The timing of sediment transport down Monterey Submarine Canyon, offshore California

USGS Publications Warehouse

Stevens, Thomas; Paull, Charles K.; Ussler, William III; McGann, Mary; Buylaert, Jan-Pieter; Lundsten, Eve M.

2013-01-01

While submarine canyons are the major conduits through which sediments are transported from the continents out into the deep sea, the time it takes for sediment to pass down through a submarine canyon system is poorly constrained. Here we report on the first study to couple optically stimulated luminescence (OSL) ages of quartz sand deposits and accelerator mass spectrometry 14C ages measured on benthic foraminifera to examine the timing of sediment transport through the axial channel of Monterey Submarine Canyon and Fan, offshore California. The OSL ages date the timing of sediment entry into the canyon head while the 14C ages of benthic foraminifera record the deposition of hemipelagic sediments that bound the sand horizons. We use both single-grain and small (∼2 mm area) single-aliquot regeneration approaches on vibracore samples from fining-upward sequences at various water depths to demonstrate relatively rapid, decadal-scale sand transport to at least 1.1 km depth and more variable decadal- to millennial-scale transport to a least 3.5 km depth on the fan. Significant differences between the time sand was last exposed at the canyon head (OSL age) and the timing of deposition of the sand (from 14C ages of benthic foraminifera in bracketing hemipelagic sediments) are interpreted as indicating that the sand does not pass through the entire canyon instantly in large individual events, but rather moves multiple times before emerging onto the fan. The increased spread in single-grain OSL dates with water depth provides evidence of mixing and temporary storage of sediment as it moves through the canyon system. The ages also indicate that the frequency of sediment transport events decreases with distance down the canyon channel system. The amalgamated sands near the canyon head yield OSL ages that are consistent with a sub-decadal recurrence frequency while the fining-upward sand sequences on the fan indicate that the channel is still experiencing events with a 150–250 year recurrence frequency out to 3.5 km water depths.    

Dynamics of sediment carbon stocks across intertidal wetland habitats of Moreton Bay, Australia.

PubMed

Hayes, Matthew A; Jesse, Amber; Hawke, Bruce; Baldock, Jeff; Tabet, Basam; Lockington, David; Lovelock, Catherine E

2017-10-01

Coastal wetlands are known for high carbon storage within their sediments, but our understanding of the variation in carbon storage among intertidal habitats, particularly over geomorphological settings and along elevation gradients, is limited. Here, we collected 352 cores from 18 sites across Moreton Bay, Australia. We assessed variation in sediment organic carbon (OC) stocks among different geomorphological settings (wetlands within riverine settings along with those with reduced riverine influence located on tide-dominated sand islands), across elevation gradients, with distance from shore and among habitat and vegetation types. We used mid-infrared (MIR) spectroscopy combined with analytical data and partial least squares regression to quantify the carbon content of ~2500 sediment samples and provide fine-scale spatial coverage of sediment OC stocks to 150 cm depth. We found sites in river deltas had larger OC stocks (175-504 Mg/ha) than those in nonriverine settings (44-271 Mg/ha). Variation in OC stocks among nonriverine sites was high in comparison with riverine and mixed geomorphic settings, with sites closer to riverine outflow from the east and south of Moreton Bay having higher stocks than those located on the sand islands in the northwest of the bay. Sediment OC stocks increased with elevation within nonriverine settings, but not in riverine geomorphic settings. Sediment OC stocks did not differ between mangrove and saltmarsh habitats. OC stocks did, however, differ between dominant species across the research area and within geomorphic settings. At the landscape scale, the coastal wetlands of the South East Queensland catchments (17,792 ha) are comprised of approximately 4,100,000-5,200,000 Mg of sediment OC. Comparatively high variation in OC storage between riverine and nonriverine geomorphic settings indicates that the availability of mineral sediments and terrestrial derived OC may exert a strong influence over OC storage potential across intertidal wetland systems. © 2017 John Wiley & Sons Ltd.

Navy Fan, California Borderland: Growth pattern and depositional processes

USGS Publications Warehouse

Normark, W.R.; Piper, D.J.W.

1984-01-01

Navy Fan is a Late Pleistocene sand-rich fan prograding into an irregularly shaped basin in the southern California Borderland. The middle fan, characterized by one active and two abandoned 'distributary' channels and associated lobe deposits, at present onlaps part of the basin slope directly opposite from the upper-fan valley, thus dividing the lower-fan/basin-plain regions into two separate parts of different depths. Fine-scale mesotopographic relief on the fan surface and correlation of individual turbidite beds through nearly 40 cores on the middle and lower fan provide data for evaluating the Late Pleistocene and Holocene depositional processes. ?? 1984 Springer-Verlag New York Inc.

Recovery and fractionation of phosphorus retained by lightweight expanded shale and masonry sand used as media in subsurface flow treatment wetlands.

PubMed

Forbes, Margaret G; Dickson, Kenneth L; Saleh, Farida; Waller, William T; Doyle, Robert D; Hudak, Paul

2005-06-15

Most subsurface flow treatment wetlands, also known as reed bed or root zone systems, use sand or gravel substrates to reduce organics, solids, and nutrients in septic tank effluents. Phosphorus (P) retention in these systems is highly variable and few studies have identified the fate of retained P. In this study, two substrates, expanded shale and masonry sand, were used as filter media in five subsurface flow pilot-scale wetlands (2.7 m3). After 1 year of operation, we estimated the annual rate of P sorption by taking the difference between total P (TP) of substrate in the pilot cells and TP of substrate not exposed to wastewater (control). Means and standard deviations of TP retained by expanded shale were 349 +/- 171 mg kg(-1), respectively. For a substrate depth of 0.9 m, aerial P retention by shale was 201 +/- 98.6 g of P m(-2) year(-1), respectively. Masonry sand retained an insignificant quantity of wastewater P (11.9 +/- 21.8 mg kg(-1)) and on occasion exported P. Substrate samples were also sequentially fractionated into labile P, microbial P, (Fe + Al) P, humic P, (Ca + Mg) P, and residual P. In expanded shale samples, the greatest increase in P was in the relatively permanent form of (Fe + Al) P (108 mg kg(-1)), followed by labile P (46.7 mg kg(-1)) and humic P (39.8 mg kg(-1)). In masonry sand, there was an increase in labile P (9.71 mg kg(-1)). Results suggest that sand is a poor candidate for long-term P storage, but its efficiency is similar to that reported for many sand, gravel, and rock systems. By contrast, expanded shale and similar products with high hydraulic conductivity and P sorption capacity could greatly improve performance of P retention in constructed wetlands.

Advanced core-analyses for subsurface characterization

NASA Astrophysics Data System (ADS)

Pini, R.

2017-12-01

The heterogeneity of geological formations varies over a wide range of length scales and represents a major challenge for predicting the movement of fluids in the subsurface. Although they are inherently limited in the accessible length-scale, laboratory measurements on reservoir core samples still represent the only way to make direct observations on key transport properties. Yet, properties derived on these samples are of limited use and should be regarded as sample-specific (or `pseudos'), if the presence of sub-core scale heterogeneities is not accounted for in data processing and interpretation. The advent of imaging technology has significantly reshaped the landscape of so-called Special Core Analysis (SCAL) by providing unprecedented insight on rock structure and processes down to the scale of a single pore throat (i.e. the scale at which all reservoir processes operate). Accordingly, improved laboratory workflows are needed that make use of such wealth of information by e.g., referring to the internal structure of the sample and in-situ observations, to obtain accurate parameterisation of both rock- and flow-properties that can be used to populate numerical models. We report here on the development of such workflow for the study of solute mixing and dispersion during single- and multi-phase flows in heterogeneous porous systems through a unique combination of two complementary imaging techniques, namely X-ray Computed Tomography (CT) and Positron Emission Tomography (PET). The experimental protocol is applied to both synthetic and natural porous media, and it integrates (i) macroscopic observations (tracer effluent curves), (ii) sub-core scale parameterisation of rock heterogeneities (e.g., porosity, permeability and capillary pressure), and direct 3D observation of (iii) fluid saturation distribution and (iv) the dynamic spreading of the solute plumes. Suitable mathematical models are applied to reproduce experimental observations, including both 1D and 3D numerical schemes populated with the parameterisation above. While it validates the core-flooding experiments themselves, the calibrated mathematical model represents a key element for extending them to conditions prevalent in the subsurface, which would be otherwise not attainable in the laboratory.

First results of the palaeogeographical research in Limyra and its environs (SW-Turkey)

NASA Astrophysics Data System (ADS)

Stock, Friederieke; Uncu, Levent; Seyer, Martin; Brückner, Helmut

2017-04-01

Geoarchaeological research in and around ancient cities of Asia Minor is an important tool for reconstructing the palaeogeography of their environs. An intensive geoarchaeological research project has started 2015 in the framework of a cooperation between the Austrian Archaeological Institute (ÖAI) and the University of Cologne (Brückner et al., 2016). 21 sediment cores were carried out in the ancient city of Limyra and its environs since 2015 and analysed with a multi-proxy approach (geochemical, sedimentological and microfaunal methods). The main goals of the project are to reconstruct (i) the environment, especially during the Classical to Late Roman periods; (ii) the geohydrological situation; (iii) the thickness of the settlement layers; (iv) the maximum extension of the former lake; to reveal (vi) the earthquake chronology and (vii) the spatio-temporal shifts in the coastline. First results show that the middle and eastern part of the city had been built on top of former lake sediments. Peat layers (so-called "floating peats") are intercalated and represent the starting siltation process. The reactivated lake phases, expressed in the rapid transitions from peat to lake strata, may be explained by earthquakes with co-seismic subsidence. Then follow fluvial sands with a fining-upward sequence (gravel at the base, overlain sands and alluvia). The strata provide information about shifting river channels. Anthropogenic layers form the top part of the core; they partly consolidated a swampy environment (core-filling limestone layers). In drill cores located between the eastern and the western city, pebbles and edged stones with artifacts follow on top of lake sediments and sands (littoral). The stones seem to have been intentionally deposited; people may have settled at the lake shore. The peat layer on top may represent the changing hydrology and co-seismic subsidence. The drill cores outside the city area confirm the sediment sequence: on top of limnic follow by a fluvial facies (fining-upward sequence, sands, alluvium). Lim 20, carried out close to the present coast reveals homogenous sands overlying the fluvial ones. The stratigraphy most likely represents the uppermost layers of a beach barrier which is overlain by dunes. Thus, the explanation that the origin of the lake was a lagoon is the most probable one.

Load capacity, failure mode and design criteria investigation of sand jacks : full scale load testing of sand jacks.

DOT National Transportation Integrated Search

2008-12-01

A sand-jack is a sand filled container used as a component of cast-in-place bridge false-work. The sand filler facilitates the removal of the false-work by allowing slow and controlled lowering of the bracing that has become wedged beneath the new br...

Geoacoustic Characterization of the Mud Drape at the New England Mud Patch

NASA Astrophysics Data System (ADS)

Reed, A. H.

2016-02-01

The New England Mud Patch is an extensive deposit of fine-grained sediments that extends from an area south of Cape Cod, MA to south of Montauk Point Long Island, NY out on the continental shelf in water depths of 60 to 90 meters. The mud patch has a remarkable accumulation of up to a 13 meter thick sequence of mud that overlays a transgressive surface of Pleistocene Age and then thins out on the periphery where surficial sediments convert from mud to sand and sand/gravel. The deposit likely accumulated in this region due to the coalescing of shelf currents that had oppositional flow. This work focuses on a section of the mud patch that is centered over the thickest portion of mud and extends east-west for 30 km and north south for 10 km. Gravity cores were collected throughout this region and the cores penetrated the upper 2-4 m of mud at 28 different sites with multiple cores collected in several locations. The mud thickness in these regions exceeded the core barrel length, therefore the cores did not penetrate into the basal sand sediment layer, a relict transgressional horizon, which displays prominently in the acoustic data for this selected region. These cores were evaluated for compressional sound speed (averaging 1480 m/s) and density (1580 kg/m3) and found to be largely homogeneous and similar throughout the study area. The largest source of inhomogeneity was due to dispersed shell hash and disarticulated bivalves, but these inclusions represent minor components in the total sediment volume. The overlying sediment that characterizes the New England Mud Patch can be readily classified as mud, silty mud, or sandy-silty mud. This fine-grained sediment deposit reflects upon the low-energy nature of the hydrodynamics within this region.

Spatial Distribution of Phlebotomine Sand Fly Species (Diptera: Psychodidae) in Qom Province, Central Iran.

PubMed

Saghafipour, Abedin; Vatandoost, Hassan; Zahraei-Ramazani, Ali Reza; Yaghoobi-Ershadi, Mohammad Reza; Rassi, Yavar; Shirzadi, Mohammad Reza; Akhavan, Amir Ahmad

2017-01-01

Zoonotic cutaneous leishmaniasis (ZCL) is transmitted to humans by phlebotomine sand fly bites. ZCL is a major health problem in Iran, where basic knowledge gaps about sand fly species diversity persist in some ZCL-endemic areas. This paper describes the richness and spatial distribution of sand fly species, collected with sticky traps, in Qom province, a ZCL-endemic area in central Iran, where sand fly fauna has been poorly studied. Collected species were mapped on urban and rural digital maps based on a scale of 1/50,000. All analyses were undertaken with rural- and urban-level precision, i.e., rural and urban levels were our basic units of analysis. After identifying the sand flies, high-risk foci were determined. For spatial analysis of vector species population, the entomological sampling sites were geo-referenced using GPS. Arc GIS 9.3 software was used to determine the foci with leishmaniasis vector species. Following the analyses, two genera (Phlebotomus and Sergentomyia) and 14 species were identified. Based on the mapping and sand fly dispersion analysis, the rural districts were categorized into three groups-infection reported, without infection, and no report. Based on Geographical Information System analyses, Kahak and Markazi districts were identified as high-risk foci with leishmaniasis vector species. These findings can act as a help guide to direct active control measures to the identified high-risk foci and, eventually, lead to reduction in incidence of the disease. © Crown copyright 2016.

Full scale load testing of sand-jacks.

DOT National Transportation Integrated Search

2006-06-01

A sand-jack is a sand filled container used as a component of cast-in-place bridge false-work. The sand filler facilitates the removal of the false-work by allowing slow and controlled lowering of the bracing that has become wedged beneath the new br...

Pore-scale mechanisms of gas flow in tight sand reservoirs

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

Silin, D.; Kneafsey, T.J.; Ajo-Franklin, J.B.

2010-11-30

Tight gas sands are unconventional hydrocarbon energy resource storing large volume of natural gas. Microscopy and 3D imaging of reservoir samples at different scales and resolutions provide insights into the coaredo not significantly smaller in size than conventional sandstones, the extremely dense grain packing makes the pore space tortuous, and the porosity is small. In some cases the inter-granular void space is presented by micron-scale slits, whose geometry requires imaging at submicron resolutions. Maximal Inscribed Spheres computations simulate different scenarios of capillary-equilibrium two-phase fluid displacement. For tight sands, the simulations predict an unusually low wetting fluid saturation threshold, at whichmore » the non-wetting phase becomes disconnected. Flow simulations in combination with Maximal Inscribed Spheres computations evaluate relative permeability curves. The computations show that at the threshold saturation, when the nonwetting fluid becomes disconnected, the flow of both fluids is practically blocked. The nonwetting phase is immobile due to the disconnectedness, while the permeability to the wetting phase remains essentially equal to zero due to the pore space geometry. This observation explains the Permeability Jail, which was defined earlier by others. The gas is trapped by capillarity, and the brine is immobile due to the dynamic effects. At the same time, in drainage, simulations predict that the mobility of at least one of the fluids is greater than zero at all saturations. A pore-scale model of gas condensate dropout predicts the rate to be proportional to the scalar product of the fluid velocity and pressure gradient. The narrowest constriction in the flow path is subject to the highest rate of condensation. The pore-scale model naturally upscales to the Panfilov's Darcy-scale model, which implies that the condensate dropout rate is proportional to the pressure gradient squared. Pressure gradient is the greatest near the matrix-fracture interface. The distinctive two-phase flow properties of tight sand imply that a small amount of gas condensate can seriously affect the recovery rate by blocking gas flow. Dry gas injection, pressure maintenance, or heating can help to preserve the mobility of gas phase. A small amount of water can increase the mobility of gas condensate.« less

Identification of bedforms in lower cook inlet, Alaska

USGS Publications Warehouse

Bouma, A.H.; Rappeport, M.L.; Orlando, R.C.; Hampton, M.A.

1980-01-01

The seafloor of the central part of lower Cook Inlet, Alaska, is characterized by the presence of different sizes and types of bedforms. The bedforms in the sandy sediments include straight-crested to sinuous to lunate ripples, small, medium, and large sand waves, sand ridges, sand ribbons, and sand patches. In addition, rocky and pebbly seafloor has been identified. The water depth ranges from 25 to 120 m, and surface currents average 3.8 kt (2 m/s). Bottom currents have been measured at as much as 42 cm/s at 1 m above bottom. Underwater television observations have shown that the rate of sand transport is lower than expected because small amounts of clay and organic matter appear to inhibit remobilization. Only during the last 1 to 2 h of ebb and flood stages of spring tides, and during storms, does significant transport occur. Comparison of data from high-resolution seismic profiling systems, side-scan sonar, bottom television and camera, and bottom sampling shows that bottom and bedform interpretations based solely on sonographs can be in error. Measuring the length of 'acoustic shadows' on sonographs to obtain bedform heights gives dimensions that are too large by factors of 3-7. Bottom television investigations revealed that the troughs between small sand waves are flat and carpeted by shell fragments. Such coarse material has a high acoustic reflectance that is not related to slope or height and can lead to false interpretations on bedform dimensions. Our observations have shown that small sand waves commonly superimposed on larger ones are slightly higher than those present on flat hard bottom but are still less than calculated from acoustic shadows. Where the bottom is rather smooth or contains elevations small enough to be masked by bathymetric 'noise' caused by the pitching of the vessel, sonographs typically show either small sand waves, sand ribbons, sand patches, rocks, or smooth bottom. The smooth-bottom category can vary widely from ripples to gravelly or shelly or to small rocks with biological overgrowth as verified by television observations. Our observations have clearly demonstrated the need for an integrated multi-scale observation and sampling program in order to classify the bottom characteristics and to provide quantitative data for transport calculations. ?? 1980.

Soil and surface layer type affect non-rainfall water inputs

NASA Astrophysics Data System (ADS)

Agam, Nurit; Berliner, Pedro; Jiang, Anxia

2017-04-01

Non-rainfall water inputs (NRWIs), which include fog deposition, dew formation, and direct water vapor adsorption by the soil, play a vital role in arid and semiarid regions. Environmental conditions, namely radiation, air temperature, air humidity, and wind speed, largely affect the water cycle driven by NRWIs. The substrate type (soil type and the existence/absence of a crust layer) may as well play a major role. Our objective was to quantify the effects of soil type (loess vs. sand) and surface layer (bare vs. crusted) on the gain and posterior evaporation of NRWIs in the Negev Highlands throughout the dry summer season. Four undisturbed soil samples (20 cm diameter and 50 cm depth) were excavated and simultaneously introduced into a PVC tube. Two samples were obtained in the Negev's Boker plain (loess soil) and two in the Nizzana sand dunes in the Western Negev. On one sample from each site the crust was removed while on the remaining one the natural crust was left in place. The samples were brought to the research site at the Jacob Bluestein Institutes for Desert Research, Ben-Gurion University of the Negev, Israel (31˚08' N, 34˚53' E, 400 meter above the sea level) where they were exposed to the same environmental conditions. The four samples in their PVC tubes were placed on top of scales and the samples mass was continuously monitored. Soil temperatures were monitored at depths of 1, 2, 3, 5 and10 cm in each microlysimeter (ML) using Copper-Constantan thermocouples. The results of particle size distribution indicated that the crust of the loess soil is probably a physical crust, i.e., a crust that forms due to raindroplets impact; while the crust on the sand soil is biological. On most days, the loess soils adsorbed more water than their corresponding sand soil samples. For both soils, the samples for which the crust was removed adsorbed more water than the samples for which it was intact. The difference in daily water adsorption amount between crusted and non-crusted sandy soils often exceeded that between crusted and non-crusted loess soils.

Late Holocene coastal stratigraphy of Sitkinak Island reveals Aleutian-Alaska megathrust earthquakes and tsunamis southwest of Kodiak Island

NASA Astrophysics Data System (ADS)

Nelson, A. R.; Briggs, R. W.; Kemp, A.; Haeussler, P. J.; Engelhart, S. E.; Dura, T.; Angster, S. J.; Bradley, L.

2012-12-01

Uncertainty in earthquake and tsunami prehistory of the Aleutian-Alaska megathrust westward of central Kodiak Island limit assessments of southern Alaska's earthquake hazard and forecasts of potentially damaging tsunamis along much of North America's west coast. Sitkinak Island, one of the Trinity Islands off the southwest tip of Kodiak Island, lies at the western end of the rupture zone of the 1964 Mw9.2 earthquake. Plafker reports that a rancher on the north coast of Sitkinak Island observed ~0.6 m of shoreline uplift immediately following the 1964 earthquake, and the island is now subsiding at about 3 mm/yr (PBO GPS). Although a high tsunami in 1788 caused the relocation of the first Russian settlement on southwestern Kodiak Island, the eastern extent of the megathrust rupture accompanying the tsunami is uncertain. Interpretation of GPS observations from the Shumagin Islands, 380 km southwest of Kodiak Island, suggests an entirely to partially creeping megathrust in that region. Here we report the first stratigraphic evidence of tsunami inundation and land-level change during prehistoric earthquakes west of central Kodiak Island. Beneath tidal and freshwater marshes around a lagoon on the south coast of Sitkinak Island, 27 cores and tidal outcrops reveal the deposits of four to six tsunamis in 2200 years and two to four abrupt changes in lithology that may correspond with coseismic uplift and subsidence over the past millennia. A 2- to 45-mm-thick bed of clean to peaty sand in sequences of tidal sediment and freshwater peat, identified in more than one-half the cores as far inland as 1.5 km, was probably deposited by the 1788 tsunami. A 14C age on Scirpus seeds, double 137Cs peaks at 2 cm and 7 cm depths (Chernobyl and 1963?), a consistent decline in 210Pb values, and our assumption of an exponential compaction rate for freshwater peat, point to a late 18th century age for the sand bed. Initial 14C ages suggest that two similar extensive sandy beds, identified in eight cores at higher tidal and freshwater sites, date from about 1.5 ka and 2.0 ka, respectively. A younger silty sand bed, <10 cm beneath the now-eroding low marsh around the lagoon, may record the 1964 tsunami. Correlations of two to three other sandy beds are too uncertain to infer their deposition by tsunamis. Stratigraphic contacts found only in cores and outcrops of the <0.8- to 1-ka tidal section fringing the lagoon may mark coseismic uplift (peat over tidal mud, sometimes with intervening sand) or subsidence (tidal mud over peat, sometimes with intervening sand). We collected samples of modern tidal foraminifera along three elevational transects for the baseline dataset needed to use fossil assemblages to measure the amount of uplift or subsidence recorded by contacts. Foraminiferal assemblages above and below one contact confirm rapid uplift a few hundred years before the 1788 tsunami, but cores are too few to correlate this contact with any of the sandy beds that we infer were deposited by tsunamis farther inland. These initial results demonstrate the promise of this previously unexplored island and similar sites for using stratigraphic evidence of sudden land-level changes and high tsunamis to map prehistoric ruptures of the Aleutian-Alaskan megathrust.

Controls on desert dune activity - a geospatial approach

NASA Astrophysics Data System (ADS)

Lancaster, N.; Hesse, P. P.

2017-12-01

Desert and other inland dunes occur on a wide spectrum of activity (defined loosely as the proportion of the surface area subject to sand movement) from unvegetated to sparsely vegetated "active" dunes through discontinuously vegetated inactive dunes to completely vegetated and degraded dunes. Many of the latter are relicts of past climatic conditions. Although field studies and modeling of the interactions between winds, vegetation cover, and dune activity can provide valuable insights, the response of dune systems to climate change and variability past, present, and future has until now been hampered by the lack of pertinent observational data on geomorphic and climatic boundary conditions and dune activity status for most dune areas. We have developed GIS-based approach that permits analysis of boundary conditions and controls on dune activity at a range of spatial scales from dunefield to global. In this approach, the digital mapping of dune field and sand sea extent has been combined with systematic observations of dune activity at 0.2° intervals from high resolution satellite image data, resulting in four classes of activity. 1 km resolution global gridded datasets for the aridity index (AI); precipitation, satellite-derived percent vegetation cover; and estimates of sand transport potential (DP) were re-sampled for each 0.2° grid cell, and dune activity was compared to vegetation cover, sand transport potential, precipitation, and the aridity index. Results so far indicate that there are broad-scale relationships between dunefield mean activity, climate, and vegetation cover. However, the scatter in the data suggest that other local factors may be at work. Intra-dune field patterns are complex in many cases. Overall, much more work needs to be done to gain a full understanding of controls at different spatial and temporal scales, which can be faciliated by this spatial database.

Laboratory investigation of the erosion of cohesive sediments under oscillatory flows using a synchronized imaging technique

NASA Astrophysics Data System (ADS)

Sou, I.; Calantoni, J.; Reed, A. H.; Furukawa, Y.

2012-12-01

A synchronized dual stereo particle image velocimetry (PIV) measurement technique is used to examine the erosion process of a cohesive sediment core in the Small Oscillatory Flow Tunnel (S-OFT) in the Sediment Dynamics Laboratory at the Naval Research Laboratory, Stennis Space Center, MS. The PIV system uses four cameras and a dual cavity Nd:YAG laser. The system allows for a pair of stereo PIV windows of about 10 cm by 10 cm each to be arbitrarily located within a single light sheet. Image pairs were acquired with all four cameras at 50 Hz for 50 consecutive seconds for each flow condition. The stereo PIV windows were positioned on either side of sediment cores inserted along the centerline of the S-OFT allowing for a total measurement window of about 20 cm long by 10 cm high with sub-millimeter spacing on resolved velocity vectors. The oscillatory flows are generated by two types of driving mechanism (scotch yoke and crank lever) for converting the rotational motion of the flywheel into the linear motion of a piston. The period of oscillation ranged from 2.86 to 6.12 seconds with constant semi-excursion amplitude in the test section of 9 cm. Two kinds of inorganic sediment samples were examined. One was a mixture of 50% kaolinite and 50% 500-micron sand under flows driven by the crank lever mechanism. Another sediment core was a mixture of 50% mud collected in Galveston Bay, TX, and 50% 250-micron sand under flows driven by the scotch-yoke mechanism. During the erosion process, Kelvin-Helmholtz instabilities were observed as the flow accelerated in each direction and eventually were broken down when the flow reversed. An example of the instantaneous velocity field superimposed on the raw image is shown in Figure 1. The relative concentration of suspended sediments under different flow conditions was estimated using the intensity of light scattered from the sediment particles in suspension. By subtracting the initial light scattered from the mud core, the residual light intensity was assumed to be scattered from suspended sediments eroded from the core. Relative comparisons were only made using the same sample mixture since it is difficult, if not impossible, to calibrate the light scattering from different sediments.; Figure 1. An example of the instantaneous time-resolved velocity field superimposed on the raw image.

The Contribution of Oil Sands Industry Related Atmospheric THg and MeHg Deposition to Rivers of the Athabasca Oil Sands Region of Canada

NASA Astrophysics Data System (ADS)

Wasiuta, V. L.; Cooke, C. A.; Kirk, J.; Chambers, P. A.; Alexander, A. C.; Rooney, R. C.

2017-12-01

Rapid development of Oil Sands deposits in northern Alberta (Canada) raises concerns about human health and environmental impacts. We present results from a three-year study of winter-time atmospheric deposition of total mercury (THg) and methylmercury (MeHg) in six tributary watersheds of the Athabasca River. Seasonal snowpack THg and MeHg concentrations were obtained from spring-time sampling throughout the oil sands region. Winter-time Hg loads were then modeled at watershed and sub-basin scales using ArcGIS geostatistical kriging. To determine the potential impacts of snowmelt on aquatic ecosystems, six rivers were sampled at high frequency over 2012 to 2014 ice-free seasons. Hydrologic year (HY) and first discharge peak loads were then calculated from linear extrapolation of measured concentrations and mean daily discharge. Results showed high THg and MeHg loads from atmospheric deposition around regional upgrading facilities with loads diminishing outwards. This reflects the large proportion of particle bound Hg with a short atmospheric residence time, and deposition close to emission sources. Snowpacks within the six watersheds contained substantial proportions of tributary river THg and MeHg loads. For example, HY2014 snowpacks contained 24 to 46 % of river MeHg loads. All rivers showed a large proportion of HY loads discharged, within a few weeks, in the spring first discharge peak. HY2014 snowpack MeHg loads were greater than river loads in the first discharge peak for all watersheds except the High Hills. This first discharge peak is important as it occurs during critical growth periods for aquatic life. Large differences in tributary river THg and MeHg loads suggest factors other than atmospheric deposition and watershed scale contributed to the load. Considerably higher THg and MeHg snowpack loads in the Muskeg Watershed relative to river export suggest substantial losses to catchment soils or wetlands during snowmelt. Evaluation of factors that could contribute to the large differences in watershed Hg discharge, include proportion of wetlands along with different wetland classes, scale of industrial development, and development hydrologic connectivity. The consequence of long-term Hg loading to wetland ecosystems has yet to be assessed.

The Pearson-Readhead Survey of Compact Extragalactic Radio Sources from Space. II. Analysis of Source Properties

NASA Astrophysics Data System (ADS)

Lister, M. L.; Tingay, S. J.; Preston, R. A.

2001-06-01

We have performed a multidimensional correlation analysis on the observed properties of a statistically complete core-selected sample of compact radio-loud active galactic nuclei based on data from the VLBI Space Observing Programme (Paper I) and previously published studies. Our sample is drawn from the well-studied Pearson-Readhead (PR) survey and is ideally suited for investigating the general effects of relativistic beaming in compact radio sources. In addition to confirming many previously known correlations, we have discovered several new trends that lend additional support to the beaming model. These trends suggest that the most highly beamed sources in core-selected samples tend to have (1) high optical polarizations; (2) large parsec- kiloparsec-scale jet misalignments; (3) prominent VLBI core components; (4) one-sided, core, or halo radio morphology on kiloparsec scales; (5) narrow emission line equivalent widths; and (6) a strong tendency for intraday variability at radio wavelengths. We have used higher resolution space and ground-based VLBI maps to confirm the bimodality of the jet misalignment distribution for the PR survey and find that the sources with aligned parsec- and kiloparsec-scale jets generally have arcsecond-scale radio emission on both sides of the core. The aligned sources also have broader emission line widths. We find evidence that the BL Lacertae objects in the PR survey are all highly beamed and have very similar properties to the high optically polarized quasars, with the exception of smaller redshifts. A cluster analysis on our data shows that after partialing out the effects of redshift, the luminosities of our sample objects in various wave bands are generally well correlated with each other but not with other source properties.

Monitoring Sand Sheets and Dunes

NASA Image and Video Library

2017-06-12

NASA's Mars Reconnaissance Orbiter (MRO) captured this crater featuring sand dunes and sand sheets on its floor. What are sand sheets? Snow fall on Earth is a good example of sand sheets: when it snows, the ground gets blanketed with up to a few meters of snow. The snow mantles the ground and "mimics" the underlying topography. Sand sheets likewise mantle the ground as a relatively thin deposit. This kind of environment has been monitored by HiRISE since 2007 to look for movement in the ripples covering the dunes and sheets. This is how scientists who study wind-blown sand can track the amount of sand moving through the area and possibly where the sand came from. Using the present environment is crucial to understanding the past: sand dunes, sheets, and ripples sometimes become preserved as sandstone and contain clues as to how they were deposited The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25 centimeters (9.8 inches) per pixel (with 1 x 1 binning); objects on the order of 75 centimeters (29.5 inches) across are resolved.] North is up. https://photojournal.jpl.nasa.gov/catalog/PIA21757

An experimental study on dynamic response for MICP strengthening liquefiable sands

NASA Astrophysics Data System (ADS)

Han, Zhiguang; Cheng, Xiaohui; Ma, Qiang

2016-12-01

The technology of bio-grouting is a new technique for soft ground improvement. Many researchers have carried out a large number of experiments and study on this topic. However, few studies have been carried out on the dynamic response of solidified sand samples, such reducing liquefaction in sand. To study this characteristic of microbial-strengthened liquefiable sandy foundation, a microorganism formula and grouting scheme is applied. After grouting, the solidified samples are tested via dynamic triaxial testing to examine the cyclic performance of solidified sand samples. The results indicate that the solidified sand samples with various strengths can be obtained to meet different engineering requirements, the use of bacteria solution and nutritive salt is reduced, and solidified time is shortened to 1-2 days. Most importantly, in the study of the dynamic response, it is found that the MICP grouting scheme is effective in improving liquefiable sand characteristic, such as liquefaction resistance.

Heterogeneous photochemistry of oxalic acid on Mauritanian sand and Icelandic volcanic ash.

PubMed

Styler, Sarah A; Donaldson, D J

2012-08-21

Teragram quantities of crustal and volcanic aerosol are released into the atmosphere on an annual basis. Although these substrates contain photoactive metal oxides, little is known about the role that they may play in catalyzing the heterogeneous phototransformation of semivolatile organic species. In the present study, we have investigated oxalic acid photochemistry at the surface of Fe(2)O(3), TiO(2), Mauritanian sand, and Icelandic volcanic ash in the presence and absence of oxygen using a photochemical Knudsen cell reactor. Illumination of all sample types resulted in the production of gas-phase CO(2). In the case of Mauritanian sand, the production of gas-phase CO(2) scaled with the loss of surface oxalic acid. In the absence of oxygen, the production of CO(2) by the sand and ash films scaled with the absorption spectrum of iron oxalate, which suggests that the reaction is at least in part iron-mediated. The presence of oxygen suppressed CO(2) production at the Fe(2)O(3) surface, enhanced CO(2) production at the Mauritanian sand surface, and did not have a net effect upon CO(2) production at the Icelandic ash surface. These different oxygen dependencies imply that oxalic acid photochemistry at the authentic surfaces under study was not solely iron-mediated. Experiments at the TiO(2) surface, which showed enhanced CO(2) production from oxalic acid in the presence of oxygen, suggest that Ti-mediated photochemistry played an important role. In summary, these results provide evidence that solid-phase aerosol photochemistry may influence the atmospheric lifetime of oxalic acid in arid regions, where its removal via wet deposition is insignificant.

Oxygen profile and clogging in vertical flow sand filters for on-site wastewater treatment.

PubMed

Petitjean, A; Forquet, N; Boutin, C

2016-04-01

13 million people (about 20% of the population) use on-site wastewater treatment in France. Buried vertical sand filters are often built, especially when the soil permeability is not sufficient for septic tank effluent infiltration in undisturbed soil. Clogging is one of the main problems deteriorating the operation of vertical flow filters for wastewater treatment. The extent of clogging is not easily assessed, especially in buried vertical flow sand filters. We suggest examining two possible ways of detecting early clogging: (1) NH4-N/NO3-N outlet concentration ratio, and (2) oxygen measurement within the porous media. Two pilot-scale filters were equipped with probes for oxygen concentration measurements and samples were taken at different depths for pollutant characterization. Influent and effluent grab-samples were taken three times a week. The systems were operated using batch-feeding of septic tank effluent. Qualitative description of oxygen transfer processes under unclogged and clogged conditions is presented. NH4-N outlet concentration appears to be useless for early clogging detection. However, NO3-N outlet concentration and oxygen content allows us to diagnose the early clogging of the system. Copyright © 2016 Elsevier Ltd. All rights reserved.

Neutral glycans from sandfish skin can reduce friction of polymers

PubMed Central

Vihar, Boštjan; Hanisch, Franz Georg; Baumgartner, Werner

2016-01-01

The lizard Scincus scincus, also known as sandfish, can move through aeolian desert sand in a swimming-like manner. A prerequisite for this ability is a special integument, i.e. scales with a very low friction for sand and a high abrasion resistance. Glycans in the scales are causally related to the low friction. Here, we analysed the glycans and found that neutral glycans with five to nine mannose residues are important. If these glycans were covalently bound to acrylic polymers like poly(methyl methacrylate) or acrylic car coatings at a density of approximately one molecule per 4 nm², friction for and adhesion of sand particles could be reduced to levels close to those observed with sandfish scales. This was also found true, if the glycans were isolated from sources other than sandfish scales like plants such as almonds or mistletoe. We speculate that these neutral glycans act as low density spacers separating sand particles from the dense scales thereby reducing van der Waals forces. PMID:27030038

Sand ridge morphology and bedform migration patterns derived from bathymetry and backscatter on the inner-continental shelf offshore of Assateague Island, USA

USGS Publications Warehouse

Pendleton, Elizabeth; Brothers, Laura; Thieler, E. Robert; Sweeney, Edward

2017-01-01

The U.S. Geological Survey and the National Oceanographic and Atmospheric Administration conducted geophysical and hydrographic surveys, respectively, along the inner-continental shelf of Fenwick and Assateague Islands, Maryland and Virginia over the last 40 years. High resolution bathymetry and backscatter data derived from surveys over the last decade are used to describe the morphology and presence of sand ridges on the inner-continental shelf and measure the change in the position of smaller-scale (10–100 s of meters) seafloor features. Bathymetric surveys from the last 30 years link decadal-scale sand ridge migration patterns to the high-resolution measurements of smaller-scale bedform features. Sand ridge morphology on the inner-shelf changes across-shore and alongshore. Areas of similar sand ridge morphology are separated alongshore by zones where ridges are less pronounced or completely transected by transverse dunes. Seafloor-change analyses derived from backscatter data over a 4–7 year period show that southerly dune migration increases in magnitude from north to south, and the east-west pattern of bedform migration changes ~ 10 km north of the Maryland-Virginia state line. Sand ridge morphology and occurrence and bedform migration changes may be connected to observed changes in geologic framework including topographic highs, deflated zones, and sand availability. Additionally, changes in sand ridge occurrence and morphology may help explain changes in the long-term shoreline trends along Fenwick and Assateague Islands. Although the data presented here cannot quantitatively link sand ridges to sediment transport and shoreline change, it does present a compelling relationship between inner-shelf sand availability and movement, sand ridge occurrence and morphology, geologic framework, and shoreline behavior.

Controls on late Holocene drift-sand dynamics: the role of people and climate on inland aeolian activity in the Netherlands

NASA Astrophysics Data System (ADS)

Pierik, Harm Jan; Van Lanen, Rowin; Gouw-Bouman, Marjolein; Groenewoudt, Bert; Wallinga, Jakob; Hoek, Wim

2017-04-01

Holocene drift-sand activity is commonly linked directly to either population pressure (via agricultural activity) or to climate change (e.g. storminess). In the Pleistocene sand areas of the Netherlands small-scale Holocene aeolian activity occurred since the Neolithic, whereas large scale drift-sand activity started during the Middle Ages (especially after AD 1000. This last phase coincides with the intensification of farming and demographic pressure, but is also commonly associated with a colder climate and enhanced storminess. This raises the question to what extent drift-sand activity can be attributed to human activities or to natural forcing factors. In this study we compare the spatial and chronological patterns of drift-sand occurrence for four characteristic Pleistocene sand regions in the Netherlands. For this, we compiled a new supra-regional overview of dates related to drift-sand activity (14C, OSL, archaeological and historical), that we compared with existing national soil maps, historical-route networks, and vegetation and climate reconstructions. Results show a steady occurrence of aeolian activity between 1000 BC and AD 1000, interrupted by remarkable dip in aeolian activity around 2000 BP, probably caused by changing land-use practices or by lower storminess. It is evident that human pressure on the landscape was most influential on initiating sand drifting: this is supported by more frequent occurrence close to routes and the uninterrupted increase in drift-sand activity after ca AD 1000 during periods of high population density and large-scale deforestation. Once triggered by human activities, the drift-sand development was probably further enhanced several centuries later during the cold and more stormy Little Ice Age (AD 1570-1900).

Sand ridge morphology and bedform migration patterns derived from bathymetry and backscatter on the inner-continental shelf offshore of Assateague Island, USA

NASA Astrophysics Data System (ADS)

Pendleton, Elizabeth A.; Brothers, Laura L.; Thieler, E. Robert; Sweeney, Edward M.

2017-07-01

The U.S. Geological Survey and the National Oceanographic and Atmospheric Administration conducted geophysical and hydrographic surveys, respectively, along the inner-continental shelf of Fenwick and Assateague Islands, Maryland and Virginia over the last 40 years. High resolution bathymetry and backscatter data derived from surveys over the last decade are used to describe the morphology and presence of sand ridges on the inner-continental shelf and measure the change in the position of smaller-scale (10-100 s of meters) seafloor features. Bathymetric surveys from the last 30 years link decadal-scale sand ridge migration patterns to the high-resolution measurements of smaller-scale bedform features. Sand ridge morphology on the inner-shelf changes across-shore and alongshore. Areas of similar sand ridge morphology are separated alongshore by zones where ridges are less pronounced or completely transected by transverse dunes. Seafloor-change analyses derived from backscatter data over a 4-7 year period show that southerly dune migration increases in magnitude from north to south, and the east-west pattern of bedform migration changes 10 km north of the Maryland-Virginia state line. Sand ridge morphology and occurrence and bedform migration changes may be connected to observed changes in geologic framework including topographic highs, deflated zones, and sand availability. Additionally, changes in sand ridge occurrence and morphology may help explain changes in the long-term shoreline trends along Fenwick and Assateague Islands. Although the data presented here cannot quantitatively link sand ridges to sediment transport and shoreline change, it does present a compelling relationship between inner-shelf sand availability and movement, sand ridge occurrence and morphology, geologic framework, and shoreline behavior.

Supply-Limited Bedforms in a Gravel-Sand Transition

NASA Astrophysics Data System (ADS)

Venditti, J. G.; Nittrouer, J. A.; Humphries, R. P.; Allison, M. A.

2009-12-01

Rivers often exhibit an abrupt transition from gravel to sand-bedded conditions as river channel slopes decrease. A distinct suite of bedforms has been observed through these reaches where sand supply to the bed is limited. The suite of bedforms includes a sequence of sand ribbons, barchans, and channel spanning dunes as sediment supply increases in the downstream direction. While these bedforms have been extensively documented in laboratory channels, there are relatively few observations of this sequence of supply-limited bedforms from large natural channels. Here we examine the sequence through the gravel-sand transition of the Fraser River in Southwestern British Columbia. We mapped the bed using multi-beam swath-bathymetry (Reson 8101 Seabat) at high flow (~9,000 m3s-1) immediately following a high peak flow of 11,800 m3s-1 in June 2007 The bed material grades from >70% gravel to entirely sand through the reach. The bedforms follow the expected sequence where sand ribbons and barchanoid forms cover the bed where it is primarily gravel. Channel spanning dunes form as the sand bed coverage increases. Bedform dimensions (height and length) increase moving downstream as the sand moving on the bed increases. Supply-unlimited bedforms typically scale with the flow depth where the height is 1/5 the flow depth. The bedforms developed over the gravel are undersized by this criterion. Downstream, where the bed is dominantly sand, bedforms do scale with flow depth. These data highlight the dominant role sediment supply can play in bedform morphology and scaling, confirming patterns observed in laboratory data.

A continuously weighing, high frequency sand trap: Wind tunnel and field evaluations

NASA Astrophysics Data System (ADS)

Yang, Fan; Yang, XingHua; Huo, Wen; Ali, Mamtimin; Zheng, XinQian; Zhou, ChengLong; He, Qing

2017-09-01

A new continuously weighing, high frequency sand trap (CWHF) has been designed. Its sampling efficiency is evaluated in a wind tunnel and the potential of the new trap has been demonstrated in field trials. The newly designed sand trap allows fully automated and high frequency measurement of sediment fluxes over extensive periods. We show that it can capture the variations and structures of wind-driven sand transport processes and horizontal sediment flux, and reveal the relationships between sand transport and meteorological parameters. Its maximum sampling frequency can reach 10 Hz. Wind tunnel tests indicated that the sampling efficiency of the CWHF sand trap varies between 39.2 to 64.3%, with an average of 52.5%. It achieved a maximum sampling efficiency of 64.3% at a wind speed of 10 m s- 1. This is largely achieved by the inclusion of a vent hole which leads to a higher sampling efficiency than that of a step-like sand trap at high wind speeds. In field experiments, we show a good agreement between the mass of sediment from the CWHF sand trap, the wind speed at 2 m and the number of saltating particles at 5 cm above the ground surface. According to analysis of the horizontal sediment flux at four heights from the CWHF sand trap (25, 35, 50, and 100 cm), the vertical distribution of the horizontal sediment flux up to a height of 100 cm above the sand surface follows an exponential function. Our field experiments show that the new instrument can capture more detailed information on sediment transport with much reduced labor requirement. Therefore, it has great potential for application in wind-blown sand monitoring and process studies.

Transport and abatement of fluorescent silica nanoparticle (SiO2 NP) in granular filtration: effect of porous media and ionic strength

NASA Astrophysics Data System (ADS)

Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

2017-03-01

The extensive production and application of engineered silica nanoparticles (SiO2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO2 NP filtration.

Gas Hydrate Petroleum System Analysis

NASA Astrophysics Data System (ADS)

Collett, T. S.

2012-12-01

In a gas hydrate petroleum system, the individual factors that contribute to the formation of gas hydrate accumulations, such as (1) gas hydrate pressure-temperature stability conditions, (2) gas source, (3) gas migration, and (4) the growth of the gas hydrate in suitable host sediment can identified and quantified. The study of know and inferred gas hydrate accumulations reveal the occurrence of concentrated gas hydrate is mostly controlled by the presence of fractures and/or coarser grained sediments. Field studies have concluded that hydrate grows preferentially in coarse-grained sediments because lower capillary pressures in these sediments permit the migration of gas and nucleation of hydrate. Due to the relatively distal nature of the deep marine geologic settings, the overall abundance of sand within the shallow geologic section is usually low. However, drilling projects in the offshore of Japan, Korea, and in the Gulf of Mexico has revealed the occurrence of significant hydrate-bearing sand reservoirs. The 1999/2000 Japan Nankai Trough drilling confirmed occurrence of hydrate-bearing sand-rich intervals (interpreted as turbidite fan deposits). Gas hydrate was determined to fill the pore spaces in these deposits, reaching saturations up to 80% in some layers. A multi-well drilling program titled "METI Toaki-oki to Kumano-nada" also identified sand-rich reservoirs with pore-filling hydrate. The recovered hydrate-bearing sand layers were described as very-fine- to fine-grained turbidite sand layers measuring from several centimeters up to a meter thick. However, the gross thickness of the hydrate-bearing sand layers were up to 50 m. In 2010, the Republic of Korea conducted the Second Ulleung Basin Gas Hydrate (UBGH2) Drilling Expedition. Seismic data clearly showed the development of a thick, potential basin wide, sedimentary sections characterized by mostly debris flows. The downhole LWD logs and core data from Site UBGH2-5 reveal that each debris flows is characterized by basal silt- to sand-rich clay dominated stratigraphic units. The upper most debris flow at Site UBGH2-5 extends into the overlying gas hydrate stability zone and IR core scans indicate that this section contains some amount of gas hydrate. The UBGH2 LWD and coring program also confirmed the occurrence of numerous volcaniclastic and siliciclastic sand reservoirs that were deposited as part of local to basin-wide turbidite events. Gas hydrate saturations within the turbidite sands ranged between 60-80 percent. In 2009, the Gulf of Mexico (GOM) Joint Industry Project (JIP) drilled seven wells at three sites, finding gas hydrate at high concentration in sands in four wells, with suspected gas hydrate at low to moderate saturations in two other wells. In the northern GOM, high sedimentation rates in conjunction with salt tectonism, has promoted the formation of complex seafloor topography. As a result, coarse-grained deposition can occur as gravity-driven sedimentation traversing the slope within intra-slope "ponded" accommodation spaces.

Microbiological quality assessment of sand and water from three selected beaches of South Coast, São Paulo State, Brazil.

PubMed

Pinto, K C; Hachich, E M; Sato, M I Z; Di Bari, M; Coelho, M C L S; Matté, M H; Lamparelli, C C; Razzolini, M T P

2012-01-01

This study aimed to assess the sanitary quality of water, and wet and dry sand from three beaches located in the South Coast region of São Paulo State, Brazil, selected taking into account the frequency of tourists and the water quality (good, fair and poor). Thirty-six water samples each of wet and dry sand and seawater were collected monthly over a period of one year and analyzed for fecal indicator bacteria (FIB: thermotolerant coliforms, Escherichia coli, and enterococci), presumptive Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and dermatophytes. The results revealed FIB concentrations more elevated in dry sand followed by wet sand and water. P. aeruginosa and presumptive S. aureus were detected with a similar frequency in water and sand samples, but maximum concentrations and geometric means were higher in dry sand. C. albicans was detected only in water samples whereas the dermatophyte Microsporum sp. was isolated exclusively from dry and wet sand samples. This evaluation showed also that the environment had a significant influence on P. aeruginosa but not on presumptive S. aureus concentrations. According to threshold values proposed in the literature for E. coli and enterococci dry sand densities, none of the beaches would be considered of sufficient quality for recreational activities.

Relationships Between Sand and Water Quality at Recreational Beaches

PubMed Central

Phillips, Matthew C.; Solo-Gabriele, Helena M.; Piggot, Alan M.; Klaus, James S.; Zhang, Yifan

2011-01-01

Enterococci are used to assess the risk of negative human health impacts from recreational waters. Studies have shown sustained populations of enterococci within sediments of beaches but comprehensive surveys of multiple tidal zones on beaches in a regional area and their relationship to beach management decisions are limited. We sampled three tidal zones on eight South Florida beaches in Miami-Dade and Broward counties and found that enterococci were ubiquitous within South Florida beach sands although their levels varied greatly both among the beaches and between the supratidal, intertidal and subtidal zones. The supratidal sands consistently had significantly higher (p<0.003) levels of enterococci (average 40 CFU/g dry sand) than the other two zones. Levels of enterococci within the subtidal sand correlated with the average level of enterococci in the water (CFU/100mL) for the season during which samples were collected (rs= 0.73). The average sand enterococci content over all the zones on each beach correlated with the average water enterococci levels of the year prior to sand samplings (rs=0.64) as well as the average water enterococci levels for the month after sand samplings (rs=0.54). Results indicate a connection between levels of enterococci in beach water and sands throughout South Florida’s beaches and suggest that the sands are one of the predominant reservoirs of enterococci impacting beach water quality. As a result, beaches with lower levels of enterococci in the sand had fewer exceedences relative to beaches with higher levels of sand enterococci. More research should focus on evaluating beach sand quality as a means to predict and regulate marine recreational water quality. PMID:22071324

Relationships between sand and water quality at recreational beaches.

PubMed

Phillips, Matthew C; Solo-Gabriele, Helena M; Piggot, Alan M; Klaus, James S; Zhang, Yifan

2011-12-15

Enterococci are used to assess the risk of negative human health impacts from recreational waters. Studies have shown sustained populations of enterococci within sediments of beaches but comprehensive surveys of multiple tidal zones on beaches in a regional area and their relationship to beach management decisions are limited. We sampled three tidal zones on eight South Florida beaches in Miami-Dade and Broward counties and found that enterococci were ubiquitous within South Florida beach sands although their levels varied greatly both among the beaches and between the supratidal, intertidal and subtidal zones. The supratidal sands consistently had significantly higher (p < 0.003) levels of enterococci (average 40 CFU/g dry sand) than the other two zones. Levels of enterococci within the subtidal sand correlated with the average level of enterococci in the water (CFU/100mL) for the season during which samples were collected (r(s) = 0.73). The average sand enterococci content over all the zones on each beach correlated with the average water enterococci levels of the year prior to sand samplings (r(s) = 0.64) as well as the average water enterococci levels for the month after sand samplings (r(s) = 0.54). Results indicate a connection between levels of enterococci in beach water and sands throughout South Florida's beaches and suggest that the sands are one of the predominant reservoirs of enterococci impacting beach water quality. As a result, beaches with lower levels of enterococci in the sand had fewer exceedences relative to beaches with higher levels of sand enterococci. More research should focus on evaluating beach sand quality as a means to predict and regulate marine recreational water quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

Removals of cryptosporidium parvum oocysts and cryptosporidium-sized polystyrene microspheres from swimming pool water by diatomaceous earth filtration and perlite-sand filtration.

PubMed

Lu, Ping; Amburgey, James E; Hill, Vincent R; Murphy, Jennifer L; Schneeberger, Chandra L; Arrowood, Michael J; Yuan, Tao

2017-06-01

Removal of Cryptosporidium-sized microspheres and Cryptosporidium parvum oocysts from swimming pools was investigated using diatomaceous earth (DE) precoat filtration and perlite-sand filtration. In pilot-scale experiments, microsphere removals of up to 2 log were obtained with 0.7 kg·DE/m 2 at a filtration rate of 5 m/h. A slightly higher microsphere removal (2.3 log) was obtained for these DE-precoated filters when the filtration rate was 3.6 m/h. Additionally, pilot-scale perlite-sand filters achieved greater than 2 log removal when at least 0.37 kg/m 2 of perlite was used compared to 0.1-0.4 log removal without perlite both at a surface loading rate of 37 m/h. Full-scale testing achieved 2.7 log of microspheres and oocysts removal when 0.7 kg·DE/m 2 was used at 3.6 m/h. Removals were significantly decreased by a 15-minute interruption of the flow (without any mechanical agitation) to the DE filter in pilot-scale studies, which was not observed in full-scale filters. Microsphere removals were 2.7 log by perlite-sand filtration in a full-scale swimming pool filter operated at 34 m/h with 0.5 kg/m 2 of perlite. The results demonstrate that either a DE precoat filter or a perlite-sand filter can improve the efficiency of removal of microspheres and oocysts from swimming pools over a standard sand filter under the conditions studied.

The Influence of SAND’s Gradation and Clay Content of Direct Sheart Test on Clayey Sand

NASA Astrophysics Data System (ADS)

Wibisono, Gunawan; Agus Nugroho, Soewignjo; Umam, Khairul

2018-03-01

The shear strength of clayey-sand can be affected by several factors, e.g. gradation, density, moisture content, and the percentage of clay and sand fraction. The same percentage of clay and sand fraction in clayey-sand mixtures may have different shear strengths due to those factors. This research aims to study the effect of clay content on sand that cause the change of its shear strength. Samples consisted of different clay and sand fractions were reconstituted at a certain moisture content. Sand fractions varied from well-graded to poorly-graded sand. Shear strength was measured in terms of the direct shear test. Prior to the test, surcharge loads were applied to represent overburden pressures. Shear strength results and their components (i.e. Cohesion and internal angle of friction) were correlated with physical properties of samples (i.e. grading coefficient of curvature, coefficient of uniformity, and density). Results showed that samples classified as well-graded and dense sand had higher shear strength. In the other hand, the shear strengths decreased when the mixtures became poorly-graded and less dense. The inclusion of the clay fraction increased cohesion component and decreased internal angle of friction.

Textural evidence for jamming and dewatering of a sub-surface, fluid-saturated granular flow

NASA Astrophysics Data System (ADS)

Sherry, T. J.; Rowe, C. D.; Kirkpatrick, J. D.; Brodsky, E. E.

2011-12-01

Sand injectites are spectacular examples of large-scale granular flows involving migration of hundreds of cubic meters of sand slurry over hundreds of meters to kilometers in the sub-surface. By studying the macro- and microstructural textures of a kilometer-scale sand injectite, we interpret the fluid flow regimes during emplacement and define the timing of formation of specific textures in the injected material. Fluidized sand sourced from the Santa Margarita Fm., was injected upward into the Santa Cruz Mudstone, Santa Cruz County, California. The sand injectite exposed at Yellow Bank Beach records emplacement of both hydrocarbon and aqueous sand slurries. Elongate, angular mudstone clasts were ripped from the wall rock during sand migration, providing evidence for high velocity, turbid flow. However, clast long axis orientations are consistently sub-horizontal suggesting the slurry transitioned to a laminar flow as the flow velocity decreased in the sill-like intrusion. Millimeter to centimeter scale laminations are ubiquitous throughout the sand body and are locally parallel to the mudstone clast long axes. The laminations are distinct in exposure because alternating layers are preferentially cemented with limonite sourced from later groundwater infiltration. Quantitative microstructural analyses show that the laminations are defined by subtle oscillations in grain alignment between limonite and non-limonite stained layers. Grain packing, size and shape distributions do not vary. The presence of limonite in alternating layers results from differential infiltration of groundwater, indicating permeability changes between the layers despite minimal grain scale differences. Convolute dewatering structures deform the laminations. Dolomite-cemented sand, a signature of hydrocarbon saturation, forms irregular bodies that cross-cut the laminations and dewatering structures. Laminations are not formed in the dolomite-cemented sand. The relative viscosity difference between the hydrocarbon and aqueous sand slurries controls the the critical radius of the contacts between dolomite cemented and limonite cemented sand bodies. The cross-cutting relationships established in the field show that the laminations formed at the jamming transition in the aqueous sand slurry. We interpret the laminations as preserving evidence for dynamic permeability instabilities in the dewatering slurry. Relatively high permeability channels formed as pore fluid flow rearranged grains during initial dewatering. Once initiated, the flow localized further into the higher permeability channels resulting in a feedback that caused the permeability in the channels to increase.

Anatomy of a shoreface sand ridge revisited using foraminifera: False Cape Shoals, Virginia/North Carolina inner shelf

USGS Publications Warehouse

Robinson, M.M.; McBride, R.A.

2008-01-01

Certain details regarding the origin and evolution of shelf sand ridges remain elusive. Knowledge of their internal stratigraphy and microfossil distribution is necessary to define the origin and to determine the processes that modify sand ridges. Fourteen vibracores from False Cape Shoal A, a well-developed shoreface-attached sand ridge on the Virginia/North Carolina inner continental shelf, were examined to document the internal stratigraphy and benthic foraminiferal assemblages, as well as to reconstruct the depositional environments recorded in down-core sediments. Seven sedimentary and foraminiferal facies correspond to the following stratigraphic units: fossiliferous silt, barren sand, clay to sandy clay, laminated and bioturbated sand, poorly sorted massive sand, fine clean sand, and poorly sorted clay to gravel. The units represent a Pleistocene estuary and shoreface, a Holocene estuary, ebb tidal delta, modern shelf, modern shoreface, and swale fill, respectively. The succession of depositional environments reflects a Pleistocene sea-level highstand and subsequent regression followed by the Holocene transgression in which barrier island/spit systems formed along the Virginia/North Carolina inner shelf ???5.2 ka and migrated landward and an ebb tidal delta that was deposited, reworked, and covered by shelf sand.

Anatomy of a shoreface sand ridge revisted using foraminifera: False Cape Shoals, Virginia/North Carolina inner shelf

USGS Publications Warehouse

Robinson, Marci M.; McBride, Randolph A.

2008-01-01

Certain details regarding the origin and evolution of shelf sand ridges remain elusive. Knowledge of their internal stratigraphy and microfossil distribution is necessary to define the origin and to determine the processes that modify sand ridges. Fourteen vibracores from False Cape Shoal A, a well-developed shoreface-attached sand ridge on the Virginia/North Carolina inner continental shelf, were examined to document the internal stratigraphy and benthic foraminiferal assemblages, as well as to reconstruct the depositional environments recorded in down-core sediments. Seven sedimentary and foraminiferal facies correspond to the following stratigraphic units: fossiliferous silt, barren sand, clay to sandy clay, laminated and bioturbated sand, poorly sorted massive sand, fine clean sand, and poorly sorted clay to gravel. The units represent a Pleistocene estuary and shoreface, a Holocene estuary, ebb tidal delta, modern shelf, modern shoreface, and swale fill, respectively. The succession of depositional environments reflects a Pleistocene sea-level highstand and subsequent regression followed by the Holocene transgression in which barrier island/spit systems formed along the Virginia/North Carolina inner shelf not, vert, ~5.2 ka and migrated landward and an ebb tidal delta that was deposited, reworked, and covered by shelf sand.

Behavior of plastic sand confinement grids

DOT National Transportation Integrated Search

1986-01-01

The concept of improving the load carrying ability of unbound aggregates, particularly sand, by lateral confinement has been investigated for some time. Extensive full-scale testing of the trafficability of confined beach sand pavement layers has bee...

Comparative Emissions of Random Orbital Sanding between Conventional and Self-Generated Vacuum Systems

PubMed Central

Liverseed, David R.

2013-01-01

Conventional abrasive sanding generates high concentrations of particles. Depending on the substrate being abraded and exposure duration, overexposure to the particles can cause negative health effects ranging from respiratory irritation to cancer. The goal of this study was to understand the differences in particle emissions between a conventional random orbital sanding system and a self-generated vacuum random orbital sanding system with attached particle filtration bag. Particle concentrations were sampled for each system in a controlled test chamber for oak wood, chromate painted (hexavalent chromium) steel panels, and gel-coated (titanium dioxide) fiberglass panels using a Gesamtstaub-Probenahmesystem (GSP) sampler at three different locations adjacent to the sanding. Elevated concentrations were reported for all particles in the samples collected during conventional sanding. The geometric mean concentration ratios for the three substrates ranged from 320 to 4640 times greater for the conventional sanding system than the self-generated vacuum sanding system. The differences in the particle concentration generated by the two sanding systems were statistically significant with the two sample t-test (P < 0.0001) for all three substances. The data suggest that workers using conventional sanding systems could utilize the self-generated vacuum sanding system technology to potentially reduce exposure to particles and mitigate negative health effects. PMID:23065674

Comparative emissions of random orbital sanding between conventional and self-generated vacuum systems.

PubMed

Liverseed, David R; Logan, Perry W; Johnson, Carl E; Morey, Sandy Z; Raynor, Peter C

2013-03-01

Conventional abrasive sanding generates high concentrations of particles. Depending on the substrate being abraded and exposure duration, overexposure to the particles can cause negative health effects ranging from respiratory irritation to cancer. The goal of this study was to understand the differences in particle emissions between a conventional random orbital sanding system and a self-generated vacuum random orbital sanding system with attached particle filtration bag. Particle concentrations were sampled for each system in a controlled test chamber for oak wood, chromate painted (hexavalent chromium) steel panels, and gel-coated (titanium dioxide) fiberglass panels using a Gesamtstaub-Probenahmesystem (GSP) sampler at three different locations adjacent to the sanding. Elevated concentrations were reported for all particles in the samples collected during conventional sanding. The geometric mean concentration ratios for the three substrates ranged from 320 to 4640 times greater for the conventional sanding system than the self-generated vacuum sanding system. The differences in the particle concentration generated by the two sanding systems were statistically significant with the two sample t-test (P < 0.0001) for all three substances. The data suggest that workers using conventional sanding systems could utilize the self-generated vacuum sanding system technology to potentially reduce exposure to particles and mitigate negative health effects.

Endmember analysis of isothermal and high-temperature magnetization data from ODP 910C, Yermak Plateau, NW Svalbard

NASA Astrophysics Data System (ADS)

Fabian, Karl; Knies, Jochen; Kosareva, Lina; Nurgaliev, Danis

2017-04-01

Room temperature magnetic initial curves, upper hysteresis curves, acquisition curves of induced remanent magnetization (IRM), and backfield (BF) curves have been measured between -1.5 T and 1.5 T for more than 430 samples from Ocean Drilling Program (ODP) Hole 910C. The core was drilled in 556.4 m water depth on the southern Yermak Plateau (80°15.896'N, 6°35.430'E), NW Svalbard. In total, 507.4 m of sediments were cored, and average recovery was 57%, with 80% between 170 and 504.7 meter below seafloor (mbsf). For this study, the borehole was re-sampled between 150 mbsf and 504.7 mbsf for environmental magnetic, inorganic geochemical, and sedimentological analyses (443 samples). The lithology is mainly silty-clay with some enrichments of fine sands in the lower section (below 400 mbsf). For all samples, a Curie express balance was used to obtain the temperature dependence of induced magnetization in air at a heating rate of 100 °C/min up to a maximum temperature of 800 °C. The hysteresis curves were used to infer classical hysteresis parameters like saturation remanence (Mrs), saturation magnetization (Ms), remanence coercivity (Hcr) or coercivity (Hc). In addition several other parameters, like hysteresis energy, high-field slope or saturation field have been determined and help to characterize the down-core variation of the magnetic fractions. Acquisition curves of isothermal remanent magnetization are decomposed into endmembers using non-negative matrix factorization. The obtained mixing coefficients decompose hysteresis loops, back-field, thermomagnetic curves, geochemistry, and sedimentological parameters into their related endmember components. Down-core variation of the endmembers enables reconstruction of sediment transport processes and in-situ formation of magnetic mineral phases.

Sand waves in environmental flows: Insights gained by coupling large-eddy simulation with morphodynamics

NASA Astrophysics Data System (ADS)

Sotiropoulos, Fotis; Khosronejad, Ali

2016-02-01

Sand waves arise in subaqueous and Aeolian environments as the result of the complex interaction between turbulent flows and mobile sand beds. They occur across a wide range of spatial scales, evolve at temporal scales much slower than the integral scale of the transporting turbulent flow, dominate river morphodynamics, undermine streambank stability and infrastructure during flooding, and sculpt terrestrial and extraterrestrial landscapes. In this paper, we present the vision for our work over the last ten years, which has sought to develop computational tools capable of simulating the coupled interactions of sand waves with turbulence across the broad range of relevant scales: from small-scale ripples in laboratory flumes to mega-dunes in large rivers. We review the computational advances that have enabled us to simulate the genesis and long-term evolution of arbitrarily large and complex sand dunes in turbulent flows using large-eddy simulation and summarize numerous novel physical insights derived from our simulations. Our findings explain the role of turbulent sweeps in the near-bed region as the primary mechanism for destabilizing the sand bed, show that the seeds of the emergent structure in dune fields lie in the heterogeneity of the turbulence and bed shear stress fluctuations over the initially flatbed, and elucidate how large dunes at equilibrium give rise to energetic coherent structures and modify the spectra of turbulence. We also discuss future challenges and our vision for advancing a data-driven simulation-based engineering science approach for site-specific simulations of river flooding.

Spatial Scaling of Environmental Variables Improves Species-Habitat Models of Fishes in a Small, Sand-Bed Lowland River

PubMed Central

Radinger, Johannes; Wolter, Christian; Kail, Jochem

2015-01-01

Habitat suitability and the distinct mobility of species depict fundamental keys for explaining and understanding the distribution of river fishes. In recent years, comprehensive data on river hydromorphology has been mapped at spatial scales down to 100 m, potentially serving high resolution species-habitat models, e.g., for fish. However, the relative importance of specific hydromorphological and in-stream habitat variables and their spatial scales of influence is poorly understood. Applying boosted regression trees, we developed species-habitat models for 13 fish species in a sand-bed lowland river based on river morphological and in-stream habitat data. First, we calculated mean values for the predictor variables in five distance classes (from the sampling site up to 4000 m up- and downstream) to identify the spatial scale that best predicts the presence of fish species. Second, we compared the suitability of measured variables and assessment scores related to natural reference conditions. Third, we identified variables which best explained the presence of fish species. The mean model quality (AUC = 0.78, area under the receiver operating characteristic curve) significantly increased when information on the habitat conditions up- and downstream of a sampling site (maximum AUC at 2500 m distance class, +0.049) and topological variables (e.g., stream order) were included (AUC = +0.014). Both measured and assessed variables were similarly well suited to predict species’ presence. Stream order variables and measured cross section features (e.g., width, depth, velocity) were best-suited predictors. In addition, measured channel-bed characteristics (e.g., substrate types) and assessed longitudinal channel features (e.g., naturalness of river planform) were also good predictors. These findings demonstrate (i) the applicability of high resolution river morphological and instream-habitat data (measured and assessed variables) to predict fish presence, (ii) the importance of considering habitat at spatial scales larger than the sampling site, and (iii) that the importance of (river morphological) habitat characteristics differs depending on the spatial scale. PMID:26569119

Permeability and porosity of hydrate-bearing sediments in the northern Gulf of Mexico

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

Daigle, Hugh; Cook, Ann; Malinverno, Alberto

Hydrate-bearing sands are being actively explored because they contain the highest concentrations of hydrate and are the most economically recoverable hydrate resource. However, relatively little is known about the mechanisms or timescales of hydrate formation, which are related to methane supply, fluid flux, and host sediment properties such as permeability. We used logging-while-drilling data from locations in the northern Gulf of Mexico to develop an effective medium theory-based model for predicting permeability based on clay-sized sediment fraction. The model considers permeability varying between sand and clay endpoint permeabilities that are defined from laboratory data. We verified the model using permeabilitymore » measurements on core samples from three boreholes, and then used the model to predict permeability in two wells drilled in Walker Ridge Block 313 during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II expedition in 2009. We found that the cleanest sands (clay-sized fraction <0.05) had intrinsic (hydrate-free) permeability contrasts of 5-6 orders of magnitude with the surrounding clays, which is sufficient to provide focused hydrate formation due to advection of methane from a deep source or diffusion of microbial methane from nearby clay layers. In sands where the clay-sized fraction exceeds 0.05, the permeability reduces significantly and focused flow is less pronounced. In these cases, diffusion of dissolved microbial methane is most likely the preferred mode of methane supply for hydrate formation. In conclusion, our results provide important constraints on methane supply mechanisms in the Walker Ridge area and have global implications for evaluating rates of methane migration and hydrate formation in hydrate-bearing sands.« less

Permeability and porosity of hydrate-bearing sediments in the northern Gulf of Mexico

DOE PAGES

Daigle, Hugh; Cook, Ann; Malinverno, Alberto

2015-10-14

Hydrate-bearing sands are being actively explored because they contain the highest concentrations of hydrate and are the most economically recoverable hydrate resource. However, relatively little is known about the mechanisms or timescales of hydrate formation, which are related to methane supply, fluid flux, and host sediment properties such as permeability. We used logging-while-drilling data from locations in the northern Gulf of Mexico to develop an effective medium theory-based model for predicting permeability based on clay-sized sediment fraction. The model considers permeability varying between sand and clay endpoint permeabilities that are defined from laboratory data. We verified the model using permeabilitymore » measurements on core samples from three boreholes, and then used the model to predict permeability in two wells drilled in Walker Ridge Block 313 during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II expedition in 2009. We found that the cleanest sands (clay-sized fraction <0.05) had intrinsic (hydrate-free) permeability contrasts of 5-6 orders of magnitude with the surrounding clays, which is sufficient to provide focused hydrate formation due to advection of methane from a deep source or diffusion of microbial methane from nearby clay layers. In sands where the clay-sized fraction exceeds 0.05, the permeability reduces significantly and focused flow is less pronounced. In these cases, diffusion of dissolved microbial methane is most likely the preferred mode of methane supply for hydrate formation. In conclusion, our results provide important constraints on methane supply mechanisms in the Walker Ridge area and have global implications for evaluating rates of methane migration and hydrate formation in hydrate-bearing sands.« less

Physical stratigraphy, paleontology, and magnetostratigraphy of the USGS-Santee Coastal Reserve core (CHN-803), Charleston County, South Carolina

USGS Publications Warehouse

Edwards, Lucy E.; Gohn, G.S.; ,; Prowell, D.C.; Bybell, L.M.; Bardot, L.P.; Firth, J.V.; Huber, B.T.; Frederiksen, N.O.; MacLeod, K.G.

1999-01-01

The Santee Coastal Reserve core, a 545-ft-deep corehole in northeastern Charleston County, South Carolina, recovered sediments of Late Cretaceous, Paleocene, Eocene, and Quaternary age. The deepest sediments, the Donoho Creek Formation (545-475.7 ft), consist of 69.3 ft of muddy calcareous sand of marine origin. This formation is placed within the upper Campanian calcareous nannofossil Subzone CC 22c. The overlying Peedee Formation (475.7-367.1 ft) in the core consists of 108.6 ft of silty clay of marine origin. It is placed in upper Maastrichtian calcareous nannofossil Subzones CC 25b, CC 26a, and CC 26b. Combined fossil and paleomagnetic information indicates nearly continuous deposition. Foraminifers indicate an outer neritic paleobathymetric setting. The Rhems Formation sensu stricto (367.1-267.3 ft) consists of 99.8 ft of silty clay, muddy sand, and minor calcite-cemented, shelly sand of marine origin. It is apparently the product of rapid sediment accumulation during a short period of time in the early Paleocene (calcareous nannofossil Zone NP 1). The upper part of the Rhems Formation sensu Bybell and others (1998) (267.3-237.4 ft) consists of 29.9 ft of calcite-cemented muddy sand and burrowed fine sand of marine origin. It is placed in calcareous nannofossil Zone NP 4 and, because it shows normal polarity, likely represents the upper part of the lower Paleocene. This unit may be correlative with the lower part of the Lower Bridge Member of the Williamsburg Formation in its type area. The Lower Bridge Member of the Williamsburg Formation (237.4-125.0 ft) has an unconformable contact at 205.0 ft that divides the member into lower muddy sand beds and upper calcareous clay beds. Both are placed in the upper Paleocene calcareous nannofossil Zone NP 5. The Chicora Member of the Williamsburg Formation (125-51.5 ft) consists of 73.5 ft of muddy, shelly sand of marine origin. It is poorly dated but includes late Paleocene nannofossils (Zones NP 5 and NP 6). A mollusk-bryozoan limestone (51.5-42.0 ft) above the Chicora Member of the Williamsburg yields early Eocene calcareous nannofossils representing both Zone NP 9/10 and Zone NP 12, together with pollen and dinocysts that are younger. Sediments of middle and late Eocene, Oligocene, Miocene, and Pliocene ages were not recovered in the Santee Coastal Reserve core. The upper 42.0 ft of sediments represent Quaternary deposits and are included in the Wando Formation (42.0-28.0 ft) and the informal Silver Bluff beds (28.0-0 ft).

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

French, T.

The Warden ASP project has progressed from the initial planning stage to construction of an injection plant. An ASP chemical system was designed based on laboratory evaluations that included interfacial tension, mobility requirements, rock-alkali interaction, fluid capabilities, and core tests. Field cores were obtained from the Permian No. 5 and No. 6 sands on the Warden lease in Sho-Vel-Tum oil field. A separate tank battery for the pilot pattern area was installed, and a field tracer test is currently being evaluated. Tracer test results to date indicate that there is no major fracturing in the No. 5 sand. There ismore » indication, however, of some channeling through high permeability sand. The field injection plant was designed, and construction is in progress. Several variations of injection plant design have been evaluated. Some plant design details, such as alkali storage, were found to be dependent on the availability of use equipment and project budget. The surfactant storage facility design was shown to be dependent on surfactant rheology.« less

Sand Impact Tests of a Half-Scale Crew Module Boilerplate Test Article

NASA Technical Reports Server (NTRS)

Vassilakos, Gregory J.; Hardy, Robin C.

2012-01-01

Although the Orion Multi-Purpose Crew Vehicle (MPCV) is being designed primarily for water landings, a further investigation of launch abort scenarios reveals the possibility of an onshore landing at Kennedy Space Center (KSC). To gather data for correlation against simulations of beach landing impacts, a series of sand impact tests were conducted at NASA Langley Research Center (LaRC). Both vertical drop tests and swing tests with combined vertical and horizontal velocity were performed onto beds of common construction-grade sand using a geometrically scaled crew module boilerplate test article. The tests were simulated using the explicit, nonlinear, transient dynamic finite element code LS-DYNA. The material models for the sand utilized in the simulations were based on tests of sand specimens. Although the LSDYNA models provided reasonable predictions for peak accelerations, they were not always able to track the response through the duration of the impact. Further improvements to the material model used for the sand were identified based on results from the sand specimen tests.

Constitutive models for the Etchegoin Sands, Belridge Diatomite, and overburden formations at the Lost Hills oil field, California

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

FOSSUM,ARLO F.; FREDRICH,JOANNE T.

2000-04-01

This report documents the development of constitutive material models for the overburden formations, reservoir formations, and underlying strata at the Lost Hills oil field located about 45 miles northwest of Bakersfield in Kern County, California. Triaxial rock mechanics tests were performed on specimens prepared from cores recovered from the Lost Hills field, and included measurements of axial and radial stresses and strains under different load paths. The tested intervals comprise diatomaceous sands of the Etchegoin Formation and several diatomite types of the Belridge Diatomite Member of the Monterey Formation, including cycles both above and below the diagenetic phase boundary betweenmore » opal-A and opal-CT. The laboratory data are used to drive constitutive parameters for the Extended Sandler-Rubin (ESR) cap model that is implemented in Sandia's structural mechanics finite element code JAS3D. Available data in the literature are also used to derive ESR shear failure parameters for overburden formations. The material models are being used in large-scale three-dimensional geomechanical simulations of the reservoir behavior during primary and secondary recovery.« less

The Apollo Lunar Sample Image Collection: Digital Archiving and Online Access

NASA Technical Reports Server (NTRS)

Todd, Nancy S.; Lofgren, Gary E.; Stefanov, William L.; Garcia, Patricia A.

2014-01-01

The primary goal of the Apollo Program was to land human beings on the Moon and bring them safely back to Earth. This goal was achieved during six missions - Apollo 11, 12, 14, 15, 16, and 17 - that took place between 1969 and 1972. Among the many noteworthy engineering and scientific accomplishments of these missions, perhaps the most important in terms of scientific impact was the return of 382 kg (842 lb.) of lunar rocks, core samples, pebbles, sand, and dust from the lunar surface to Earth. Returned samples were curated at JSC (then known as the Manned Spacecraft Center) and, as part of the original processing, high-quality photographs were taken of each sample. The top, bottom, and sides of each rock sample were photographed, along with 16 stereo image pairs taken at 45-degree intervals. Photographs were also taken whenever a sample was subdivided and when thin sections were made. This collection of lunar sample images consists of roughly 36,000 photographs; all six Apollo missions are represented.

Water quality, weather and environmental factors associated with fecal indicator organism density in beach sand at two recreational marine beaches.

PubMed

Heaney, Christopher D; Exum, Natalie G; Dufour, Alfred P; Brenner, Kristen P; Haugland, Richard A; Chern, Eunice; Schwab, Kellogg J; Love, David C; Serre, Marc L; Noble, Rachel; Wade, Timothy J

2014-11-01

Recent studies showing an association between fecal indicator organisms (FIOs) in sand and gastrointestinal (GI) illness among beachgoers with sand contact have important public health implications because of the large numbers of people who recreate at beaches and engage in sand contact activities. Yet, factors that influence fecal pollution in beach sand remain unclear. During the 2007 National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water Study, sand samples were collected at three locations (60 m apart) on weekend days (Sat, Sun) and holidays between June and September at two marine beaches - Fairhope Beach, AL and Goddard Beach, RI - with nearby publicly-owned treatment works (POTWs) outfalls. F(+) coliphage, enterococci, Bacteroidales, fecal Bacteroides spp., and Clostridium spp. were measured in sand using culture and qPCR-based calibrator-cell equivalent methods. Water samples were also collected on the same days, times and transects as the 144 sand samples and were assayed using the same FIO measurements. Weather and environmental data were collected at the time of sample collection. Mean FIO concentrations in sand varied over time, but not space. Enterococci CFU and CCE densities in sand were not correlated, although other FIOs in sand were. The strongest correlation between FIO density in sand and water was fecal Bacteroides CCE, followed by enterococci CFU, Clostridium spp. CCE, and Bacteroidales CCE. Overall, the factors associated with FIO concentrations in sand were related to the sand-water interface (i.e., sand-wetting) and included daily average densities of FIOs in water, rainfall, and wave height. Targeted monitoring that focuses on daily trends of sand FIO variability, combined with information about specific water quality, weather, and environmental factors may inform beach monitoring and management decisions to reduce microbial burdens in beach sand. The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency. Copyright © 2014 Elsevier B.V. All rights reserved.

Nano-Scale Sample Acquisition Systems for Small Class Exploration Spacecraft

NASA Astrophysics Data System (ADS)

Paulsen, G.

2015-12-01

The paradigm for space exploration is changing. Large and expensive missions are very rare and the space community is turning to smaller, lighter, and less expensive missions that could still perform great exploration. These missions are also within reach of commercial companies such as the Google Lunar X Prize teams that develop small scale lunar missions. Recent commercial endeavors such as "Planet Labs inc." and Sky Box Imaging, inc. show that there are new benefits and business models associated with miniaturization of space hardware. The Nano-Scale Sample Acquisition System includes NanoDrill for capture of small rock cores and PlanetVac for capture of surface regolith. These two systems are part of the ongoing effort to develop "Micro Sampling" systems for deployment by the small spacecraft with limited payload capacities. The ideal applications include prospecting missions to the Moon and Asteroids. The MicroDrill is a rotary-percussive coring drill that captures cores 7 mm in diameter and up to 2 cm long. The drill weighs less than 1 kg and can capture a core from a 40 MPa strength rock within a few minutes, with less than 10 Watt power and less than 10 Newton of preload. The PlanetVac is a pneumatic based regolith acquisition system that can capture surface sample in touch-and-go maneuver. These sampling systems were integrated within the footpads of commercial quadcopter for testing. As such, they could also be used by geologists on Earth to explore difficult to get to locations.

Stacking pattern and stratigraphic model of reservoirs from a modern analogue to ancient deltaic and siliciclastic deposits: Golfe du Lion, SE France

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

Tesson, M.; Bernard, G.; Georges, A.

1995-08-01

The {open_quotes}Golfe du Lion{close_quotes} Pleistocene shelf deposits are used as modern analogues of ancient deltaic and shallow water siliciclastic deposits. At least 6 cyclic superimposed sedimentary packages constituting a seaward thickening wedge are documented, including major progradational clinoforms units bounded by regional unconformities, with their updip terminations. Seismic correlations and geometry models, together with age dating and facies analysis of the uppermost units have been used at regional scale. They allowed to differentiate allocyclic from autocyclic events, to improve our knowledge of the nature of tectonic control on architecture, and to rely the different seismic units, inside the packages, tomore » the environmental changes from interglacial highstand to glacial lowstand in 4 to 5th order cycles. An alternative model of {open_quotes}forced regression{close_quotes} during sea level lowstand was documented and validated. The different illustrated sedimentary units, related to specific parts of the relative sea level curve along a short duration/high amplitude cycle, are: (i) the {open_quotes}forced regression{close_quotes} deposits (ii) the late lowstand massive sands onto the outer shelf (iii) the early transgressive backstepping (?) beach sands, (iii) the late transgressive backslapping parasequences. The sand content inferred from the seismic facies, comforted with the uppermost units facies from data cores, is in agreement with this model.« less

Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems: DIFFUSION-DRIVEN HYDRATE GROWTH IN SANDS

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

Nole, Michael; Daigle, Hugh; Cook, Ann E.

The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1 to 20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two- dimensional and basin-scalemore » three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. As a result, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.« less

Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems: DIFFUSION-DRIVEN HYDRATE GROWTH IN SANDS

DOE PAGES

Nole, Michael; Daigle, Hugh; Cook, Ann E.; ...

2017-02-01

The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1 to 20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two- dimensional and basin-scalemore » three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. As a result, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.« less

Movement of coliform bacteria and nutrients in ground water flowing through basalt and sand aquifers.

PubMed

Entry, J A; Farmer, N

2001-01-01

Large-scale deposition of animal manure can result in contamination of surface and ground water and in potential transfer of disease-causing enteric bacteria to animals or humans. We measured total coliform bacteria (TC), fecal coliform bacteria (FC), NO3, NH4, total P, and PO4 in ground water flowing from basalt and sand aquifers, in wells into basalt and sand aquifers, in irrigation water, and in river water. Samples were collected monthly for 1 yr. Total coliform and FC numbers were always higher in irrigation water than in ground water, indicating that soil and sediment filtered most of these bacteria before they entered the aquifers. Total coliform and FC numbers in ground water were generally higher in the faster flowing basalt aquifer than in the sand aquifer, indicating that the slower flow and finer grain size may filter more TC and FC bacteria from water. At least one coliform bacterium/100 mL of water was found in ground water from both basalt and sand aquifers, indicating that ground water pumped from these aquifers is not necessarily safe for human consumption according to the American Public Health Association and the USEPA. The NO3 concentrations were usually higher in water flowing from the sand aquifer than in water flowing from the basalt aquifer or in perched water tables in the basalt aquifer. The PO4 concentrations were usually higher in water flowing from the basalt aquifer than in water flowing from the sand aquifer. The main concern is fecal contamination of these aquifers and health consequences that may arise from human consumption.

Development of low-cost technology for the removal of iron and manganese from ground water in siwa oasis.

PubMed

El-Naggar, Hesham M

2010-01-01

Ground water is the only water resource for Siwa Oasis. It is obtained from natural freshwater wells and springs fed by the Nubian aquifer. Water samples collected from Siwa Oasis had relatively higher iron (Fe) and manganese (Mn) than the permissible limits specified in WHO Guidelines and Egyptian Standards for drinking water quality. Aeration followed by sand filtration is the most commonly used method for the removal of iron from ground water. The study aimed at development of low-cost technology for the removal of iron and manganese from ground water in Siwa Oasis. The study was carried out on Laboratory-scale columns experiments sand filters with variable depths of 15, 30, 45, 60, 75, 90 cm and three graded types of sand were studied. The graded sand (E.S. =0.205 mm, U.C. =3.366, depth of sand = 60 cm and filtration rate = 1.44 m3/m2/hr) was the best type of filter media. Iron and manganese concentrations measured in ground water with aeration only, decreased with an average removal percentage of 16%, 13% respectively. Iron and manganese concentrations after filtration with aeration came down to 0.1123, 0.05 mg/L respectively in all cases from an initial concentration of 1.14, 0.34 mg/L respectively. Advantages of such treatment unit included simplicity, low cost design, and no need for chemical addition. In addition, the only maintenance required was periodic washing of the sand filter or replacement of the sand in order to maintain reasonable flow rate through the system.

Investigation of vertical distribution and morphology of indigenous organic matter at Sleeping Bear site, Michigan

NASA Astrophysics Data System (ADS)

West, C. C.; Lyon, W. G.; Ross, D. L.; Pennington, L. K.

1994-11-01

This study evaluates the nature and origin of particulate organic carbon and organic coatings on aquifer sands upgradient from a fuel spill site near the Sleeping Bear Dunes National Lakeshore in Michigan. The distribution of carbon was found to be highly complex due to the occurrence of high organic carbon horizons, bounded above and below by high carbonate sediments. The organic coatings on the sands were examined using white light and fluorescence microscopy and by scanning electron microscopy. Core samples were analyzed for organic and inorganic carbon, solution pH, humic/fulvic acid ratios, and insoluble organic matter content (that is, humin) as a function of depth from the ground surface. The organic geochemistry of the soil profile at this site was found to be significantly influenced by the carbonates producing a sharp boundary of precipitated organic matter. This boundary was followed by coatings of predominantly fulvic acid salts on mineral grains deeper in the soil column. The coatings extended into the aquifer. The existence of native organic films on sand grains is well documented in the soils literature. The study reported here was greatly aided by this information and provides the framework for future studies concerning the influence of carbon distribution, chemical identity, and morphology on contaminant fate and transport processes.

Shallow stratigraphy of the Skagit River Delta, Washington, derived from sediment cores

USGS Publications Warehouse

Grossman, Eric E.; George, Douglas A.; Lam, Angela

2011-01-01

Sedimentologic analyses of 21 sediment cores, ranging from 0.4 to 9.6 m in length, reveal that the shallow geologic framework of the Skagit River Delta, western Washington, United States, has changed significantly since 1850. The cores collected from elevations of 3.94 to -2.41 m (relative to mean lower low water) along four cross-shore transects between the emergent marsh and delta front show relatively similar environmental changes across an area spanning ~75 km2. Offshore of the present North Fork Skagit River and South Fork Skagit River mouths where river discharge is focused by diked channels through the delta, the entire 5–7-km-wide tidal flats are covered with 1–2 m of cross-bedded medium-to-coarse sands. The bottoms of cores, collected in these areas are composed of mud. A sharp transition from mud to a cross-bedded sand unit indicates that the tidal flats changed abruptly from a calm environment to an energetic one. This is in stark contrast to the Martha's Bay tidal flats north of the Skagit Bay jetty that was completed in the 1940s to protect the newly constructed Swinomish Channel from flooding and sedimentation. North of the jetty, mud ranging from 1 to 2 m thick drapes a previously silt- and sand-rich tidal flat. The silty sand is a sediment facies that would be expected there where North Fork Skagit River sedimentation occurred prior to jetty emplacement. This report describes the compositional and textural properties of the sediment cores by using geophysical, photographic, x-radiography, and standard sediment grain-size and carbon-analytical methods. The findings help to characterize benthic habitat structure and sediment transport processes and the environmental changes that have occurred across the nearshore of the Skagit River Delta. The findings will be useful for quantifying changes to nearshore marine resources, including impacts resulting from diking, river-delta channelization, shoreline development, and natural variations in fluvial-sediment inputs. These results also provide important quantitative data on the amount of sediment delivered to the nearshore from the Skagit River for use in calculating sediment budgets for application to watershed planning and wetland and coastal-ecosystem restoration.

Investigation of soil properties for identifying recharge characteristics in the Lake Chad Basin

NASA Astrophysics Data System (ADS)

Banks, M. L.; Ndunguru, G. G.; Adisa, S. J.; Lee, J.; Adegoke, J. O.; Goni, I. B.; Grindley, J.; Mulugeta, V.

2009-12-01

Lake Chad was once labeled as one of the largest fresh water lakes in the world, providing water and livelihood to over 20 million people. The lake is shared by six different countries; Chad Nigeria, Niger, Cameroon, Central African Republic, and Sudan. Since the 1970 to date, a significant decrease in the size of the lake has been observed with the use of satellite imagery. This shrinking of the lake has been blamed on global warming, population increase and poor water management by the agriculture industry for farming purpose for both plants and animals. While these can be all valid reasons for the decrease of Lake Chad, we see the need to examine environmental and hydrological evidence around the Lake Chad basin. This study was carried out from upper stream to lower stream leading from Kano to the Damatru region which is one of several water bodies that supply Lake Chad. Over seventy six sites were sampled for soil texture, bulk density and other physical properties to investigate recharge capacity of the basin especially along the stream. Soils were collected using a soil core and properly stored at 4 degrees Celsius. Soils were weighed and put to dry at 105 degrees for twenty four hours. Dry weight was recorded and bulk density was calculated. The wet sieve method was used to determine the particle size analysis. Soils were weighed to 10 grams and hydrogen peroxide added to separate particles. Samples were washed with water and put to dry overnight. Soils were reweighed and sieved to separate as course sand, fine sand and silt and clay. The data revealed that in the upstream, coarse sand continuously decreased while silt and clay continuously increased down toward the lake. At mid stream silt and clay had significantly higher values when compared to coarse sand and fine sand. In the lower stream, bulk density clearly decreased compared to the upper and mid streams. Correlations will be carried out to investigate the particle size analysis and bulk density with recharge capacity of the lake Chad Basin.

Analysis of beachgrass ecomorphodynamics and foredune morphology along US Pacific Northwest coastal sand dunes using a Bayesian network

NASA Astrophysics Data System (ADS)

Biel, R.; Hacker, S.; Ruggiero, P.

2016-12-01

Coastal dunes provide valuable infrastructure for mitigating flooding and erosion hazard exposure by dissipating wave energy. Although vegetation is essential for foredune establishment and growth by facilitating sand deposition and stabilization, few have examined how plant distribution and abundance relates to foredune morphology in the field. The US Pacific Northwest coastal dune system presents an excellent case study for examining ecomorphodynamic processes on sand dunes. It exhibits a diverse array of geomorphological conditions, including a range of dissipative to reflective beaches and highly varied foredune morphology. Ecologically, the region contains two invasive, dune-building beachgrasses of the same genus (Ammophila arenaria and A. breviligulata). To explore how geomorphological and ecological drivers alter foredune morphology, we used a Bayesian network to assess the role of nearshore bathymetry, sand supply (measured as shoreline change rate), and beachgrass species identity and density in determining foredune morphology. At a finer scale, we also examined whether beachgrass density and species identity altered sand accretion between 2012 and 2014 at multiple points across the foredune using a mixed model. Our Bayesian network analysis indicates that nearshore slope, shoreline change rate, beach width, and beachgrass density directly or indirectly affect foredune width, slope, and height. However, we observed no relationships between species identity and foredune morphology. When examining the finer-scale relationship between beachgrass density and sand accretion at points along the foredune, we found that sand accretion was correlated with beachgrass stem density in 2012, new stem growth between 2012 and 2014, beach width, and elevation. Moreover, A. arenaria accreted more sand than A. breviligulata on the foredune face, suggesting that subtle differences in beachgrass morphology or growth patterns may produce differing accretion patterns across the foredune. Both analyses indicate that beachgrass density alters foredune morphology. Although A. arenaria and A. breviligulata exhibit differing sand accretion patterns at points across the foredune face, it is unclear whether these fine-scale differences produce coarse-scale changes in foredune morphology.

Chenier Development within a Prograding Strandplain Complex

NASA Astrophysics Data System (ADS)

FitzGerald, D.; Hein, C. J.; Georgiou, I. Y.

2017-12-01

Strandplains dominate the southern coast of Brazil due to abundant shelf and local sediment and falling sea-level (2-4 m) during the past 6 ka. These plains are composed chiefly of swash-aligned sandy beach and dune ridges deposited in bedrock-framed embayments 2-5 km wide and 3-10 km long. The Tijucas Strandplain developed in a more sheltered and deeply embayed setting fronted by long peninsulas and bedrock islands, which reduce ocean wave energy. The Tijucas River bisects the plain and has provided the primary source of sediment to produce a Holocene basinal fill composed of a seaward-thickening bay mud sequence (10-16 m thick). Long-term gradual shoaling of the basin and attendant lessening wave energy produced upper strandplain foreshore and beach units that transition from landward 8-m thick sand sections to a 3-4-m thick mud unit along the present-day shoreline. The gradual lateral change of the morpho-sedimentary character of the plain is likely a product of climate-induced changes in sediment composition and supply and/or wave regime. For example, the mid-plain is defined by a series of abrupt alterations between sand-dominated beach ridges and mixed sand-and-mud cheniers. This area contains at least four chenier complexes consisting of closely spaced (25-40 m apart) 50-75 m wide ridges composed of 3-4 m thick shelly sand underlain and separated by a cohesive basin-fill clay. The seaward portion of the plain has two sandy chenier ridges each 1 m high and <3 m thick, separated by 100 m of consolidated mud with rare sand beds. Ground-penetrating radar sections show ridges contain numerous seaward-sloping beds having variable dips and multiple truncations, resulting from repeated erosional and depositional events. Expansive, thin (<50 cm) sand sheets composed of flat-lying to shallowly landward-dipping internal radar reflections extend landward from most chenier ridges that overtop inter-ridge mud. The present beach comprises the most current developing chenier. Recent storm-induced landward transport of a thin, sandy overwash fan mimics the proposed mechanism for earlier ridge-swale development. Finally, a future chenier is forming 1 km offshore where breaking waves concentrate sand. Between these two sand deposits is a shallow (< 3 m) muddy region where cores and surface samples indicate an absence of sand.

Presence of Campylobacter and Salmonella in sand from bathing beaches.

PubMed

Bolton, F J; Surman, S B; Martin, K; Wareing, D R; Humphrey, T J

1999-02-01

The purpose of this study was to determine the presence of thermophilic Campylobacter spp. and Salmonella spp. in sand from non-EEC standard and EEC standard designated beaches in different locations in the UK and to assess if potentially pathogenic strains were present. Campylobacter spp. were detected in 82/182 (45%) of sand samples and Salmonella spp. in 10/182 (6%). Campylobacter spp. were isolated from 46/92 (50%) of samples from non-EEC standard beaches and 36/90 (40%) from EEC standard beaches. The prevalence of Campylobacter spp. was greater in wet sand from both types of beaches but, surprisingly, more than 30% of samples from dry sand also contained these organisms. The major pathogenic species C. jejuni and C. coli were more prevalent in sand from non-EEC standard beaches. In contrast, C. lari and urease positive thermophilic campylobacters, which are associated with seagulls and other migratory birds, were more prevalent in sand from EEC standard beaches. Campylobacter isolates were further characterized by biotyping and serotyping, which confirmed that strains known to be of types associated with human infections were frequently found in sand on bathing beaches.

Effect of Porosity on Synthetic Sand Infiltration within Yttria-Stabilized Zirconia Pellets

DTIC Science & Technology

Sand infiltration was investigated for several yttria-stabilized zirconia (YSZ) pellets of varying porosity. The pellets were synthesized through...each. Several characterization techniques were used to correlate the sand infiltration to porosity. It was found that there was no significant...difference in the results of low and high porosity samples. Interestingly, sand had infiltrated all samples to some degree although the magnitude of the

Do High-elevation Lakes Record Variations in Snowfall and Atmospheric Rivers in the Sierra Nevada of California?

NASA Astrophysics Data System (ADS)

Ashford, J.; Sickman, J. O.; Lucero, D. M.

2014-12-01

Understanding the underlying causes of interannual variation in snowfall and extreme hydrologic events in the Sierra Nevada is hampered by short instrumental records and the difficulties in reconstructing climate using a traditional paleo-record such as tree-rings. New paleo proxies are needed to provide a record of snowpack water content and extreme precipitation events over millennial timescales which can be used to test hypotheses regarding teleconnections between Pacific climate variability and water supply and flood risk in California. In October 2013 we collected sediment cores from Pear Lake (z = 27 m), an alpine lake in Sequoia National Park. The cores were split and characterized by P-wave velocity, magnetic susceptibility and density scanning. Radiocarbon dates indicate that the Pear Lake cores contain a 13.5K yr record of lake sediment. In contrast to other Sierra Nevada lakes previously cored by our group, high-resolution scanning revealed alternating light-dark bands (~1 mm to 5 mm thick) for most of the Pear Lake core length. This pattern was interrupted at intervals by homogenous clasts (up to 75 mm thick) ranging in grain size from sand to gravel up to 1 cm diameter. We hypothesize that the light-dark banding results from the breakdown of persistent hypolimnetic anoxia during spring snowmelt and autumn overturn. We speculate that the thicknesses of the dark bands are controlled by the duration of anoxia which in turn is controlled by the volume and duration of snowmelt. The sand to gravel sized clasts are most likely associated with extreme precipitation events resulting from atmospheric rivers intersecting the southern Sierra Nevada. We hypothesize that centimeter-sized clasts are deposited in large avalanches and that the sands are deposited in large rain events outside of the snow-cover period.

Gas and Oil Flow through Wellbore Flaws

NASA Astrophysics Data System (ADS)

Hatambeigi, M.; Anwar, I.; Reda Taha, M.; Bettin, G.; Chojnicki, K. N.; Stormont, J.

2017-12-01

We have measured gas and oil flow through laboratory samples that represent two important potential flow paths in wellbores associated with the Strategic Petroleum Reserve (SPR): cement-steel interfaces (microannuli) and cement fractures. Cement fractures were created by tensile splitting of cement cores. Samples to represent microannuli were created by placing thin steel sheets within split cement cores so flow is channeled along the cement-steel interface. The test sequence included alternating gas and oil flow measurements. The test fluids were nitrogen and silicone oil with properties similar to a typical crude oil stored in the SPR. After correcting for non-linear (inertial) flow when necessary, flows were interpreted as effective permeability and hydraulic aperture using the cubic law. For both samples with cement fractures and those with cement-steel interfaces, initial gas and oil permeabilities were comparable. Once saturated with oil, a displacement pressure had to be overcome to establish gas flow through a sample, and the subsequent gas permeability were reduced by more than 50% compared to its initial value. Keywords: wellbore integrity, leakage, fracture, microannulus, SPR. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of NTESS/Honeywell, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2017-8168 A

Development and psychometric evaluation of the Core Nurse Resource Scale.

PubMed

Simpson, Michelle R

2010-11-01

To examine the factor structure, internal consistency reliability and concurrent-related validity of the Core Nurse Resource Scale. A cross-sectional survey study design was used to obtain a sample of 149 nurses and nursing staff [Registered Nurse (RNs), Licensed Practical Nurse (LPNs) and Certified Nursing Assistant (CNAs)] working in long-term care facilities. Exploratory factor analysis, Cronbach's alpha and bivariate correlations were used to evaluate validity and reliability. Exploratory factor analysis yielded a scale with 18 items on three factors, accounting for 52% of the variance in scores. Internal consistency reliability for the composite and Core Nurse Resource Scale factors ranged from 0.79 to 0.91. The Core Nurse Resource Scale composite scale and subscales correlated positively with a measure of work engagement (r=0.247-0.572). The initial psychometric evaluation of the Core Nurse Resource Scale demonstrates it is a sound measure. Further validity and reliability assessment will need to be explored and assessed among nurses and other nursing staff working in other practice settings. The intent of the Core Nurse Resource Scale is to evaluate the presence of physical, psychological and social resources of the nursing work environment, to identify workplaces at risk for disengaged (low work engagement) nursing staff and to provide useful diagnostic information to healthcare administrators interested in interventions to improve the nursing work environment. © 2010 The Author. Journal compilation © 2010 Blackwell Publishing Ltd.

Intermittent flux from a sand filter for household wastewater and integrated solute transfer to the vadose zone.

PubMed

Nasri, Behzad; Fouché, Olivier

2018-02-24

Depending on the actual number of soil-based on-site wastewater treatment system (OWTS) in an area, on-site sanitation may be a significant source of pollutants and a threat to groundwater. Even in the case of a system functioning correctly, here, a sand filter substituted for the in-situ soil, as the treated effluent may reach to the water table, it is necessary evaluating in situ how much the sand and underneath soil respectively contribute to pollutant removal. On the plot of a household in a small rural community, the functioning of a real scale OWTS was monitored for 1.5 years. This system, composed of a septic tank connected to a 5 × 5 m 2 and 0.7-m thick aerobic sand filter was equipped with soil hydrodynamic probes (water content and matrix potential) during construction. By using the instantaneous profile method of water content, the intermittent infiltrated flux was determined across the sand-pack according to position and time. Treated water infiltrates into underneath soil acting as post-treatment. Quality of interstitial liquid from the sand and the soil was analysed each month on a 12-h pumping sample obtained through porous plates. Results of water fluxes and concentrations provide an estimate of the annual flux to the vadose zone and groundwater of metals, nutrients and some organic micro-pollutants (parabens and triclosan) through the OWTS and subsoil.

Use of Computed X-ray Tomographic Data for Analyzing the Thermodynamics of a Dissociating Porous Sand/Hydrate Mixture

DOE R&D Accomplishments Database

Freifeld, Barry M.; Kneafsey, Timothy J.; Tomutsa, Liviu; Stern, Laura A.; Kirby, Stephen H.

2002-02-28

X-ray computed tomography (CT) is a method that has been used extensively in laboratory experiments for measuring rock properties and fluid transport behavior. More recently, CT scanning has been applied successfully to detect the presence and study the behavior of naturally occurring hydrates. In this study, we used a modified medical CT scanner to image and analyze the progression of a dissociation front in a synthetic methane hydrate/sand mixture. The sample was initially scanned under conditions at which the hydrate is stable (atmospheric pressure and liquid nitrogen temperature, 77 K). The end of the sample holder was then exposed to the ambient air, and the core was continuously scanned as dissociation occurred in response to the rising temperature. CT imaging captured the advancing dissociation front clearly and accurately. The evolved gas volume was monitored as a function of time. Measured by CT, the advancing hydrate dissociation front was modeled as a thermal conduction problem explicitly incorporating the enthalpy of dissociation, using the Stefan moving-boundary-value approach. The assumptions needed to perform the analysis consisted of temperatures at the model boundaries. The estimated value for thermal conductivity of 2.6 W/m K for the remaining water ice/sand mixture is higher than expected based on conduction alone; this high value may represent a lumped parameter that incorporates the processes of heat conduction, methane gas convection, and any kinetic effects that occur during dissociation. The technique presented here has broad implications for future laboratory and field testing that incorporates geophysical techniques to monitor gas hydrate dissociation.

A Improved and Highly Effective Seabed Surface Sand Sampling Device

NASA Astrophysics Data System (ADS)

Liu, Ying

2017-04-01

In marine geology research, it is necessary to obtain a sufficient quantity of seabed surface samples, while also ensuring that the samples are in their original state. Currently, there are a number of seabed surface sampling devices available, but it is very difficult to obtain sand samples using ordinary seabed surface sampling devices, whereas machine-controlled seabed surface sampling devices are unable to dive into deeper regions of water. To obtain larger quantities of samples in their original states, many researchers have tried to improve seabed surface sampling devices, but these efforts have generally produced ambiguous results. To resolve the aforementioned issue, we have designed an improved and highly effective seabed surface sand sampling device, which incorporates the strengths of a variety of sampling devices; it is capable of diving into deeper water regions to obtain sand samples, and is also suited for use in streams, rivers, lakes and seas with varying levels of flow velocities and depth.

Patterns and Prevalence of Core Profile Types in the WPPSI Standardization Sample.

ERIC Educational Resources Information Center

Glutting, Joseph J.; McDermott, Paul A.

1990-01-01

Found most representative subtest profiles for 1,200 children comprising standardization sample of Wechsler Preschool and Primary Scale of Intelligence (WPPSI). Grouped scaled scores from WPPSI subtests according to similar level and shape using sequential minimum-variance cluster analysis with independent replications. Obtained final solution of…

DNA Barcoding Reveals Hidden Diversity of Sand Flies (Diptera: Psychodidae) at Fine and Broad Spatial Scales in Brazilian Endemic Regions for Leishmaniasis.

PubMed

Rodrigues, Bruno Leite; Carvalho-Costa, Luís Fernando; Pinto, Israel de Souza; Rebêlo, José Manuel Macário

2018-03-17

Sand fly (Diptera: Psychodidae) taxonomy is complex and time-consuming, which hampers epidemiological efforts directed toward controlling leishmaniasis in endemic regions such as northeastern Brazil. Here, we used a fragment of the mitochondrial cytochrome c oxidase I (COI) gene to identify sand fly species in Maranhão State (northeastern Brazil) and to assess cryptic diversity occurring at different spatial scales. For this, we obtained 148 COI sequences of 15 sand fly species (10 genera) from Maranhão (fine spatial scale), and joined them to COI sequences from other Brazilian localities (distant about 2,000 km from Maranhão, broad spatial scale) available in GenBank. We revealed cases of cryptic diversity in sand flies both at fine (Lutzomyia longipalpis (Lutz and Neiva) and Evandromyia termitophila (Martins, Falcão and Silva)) and broad spatial scales (Migonemyia migonei (França), Pressatia choti (Floch and Abonnenc), Psychodopygus davisi (Root), Sciopemyia sordellii (Shannon and Del Ponte), and Bichromomyia flaviscutellata (Mangabeira)). We argue that in the case of Bi. flaviscutellata, the cryptic diversity is associated with a putative new species. Cases in which DNA taxonomy was not as effective as morphological identification possibly involved recent speciation and/or introgressive hybridization, highlighting the need for integrative approaches to identify some sand fly species. Finally, we provide the first barcode sequences for four species (Brumptomyia avellari (Costa Lima), Evandromyia infraspinosa (Mangabeira), Evandromyia evandroi (Costa Lima and Antunes), and Psychodopygus complexus (Mangabeira)), which will be useful for further molecular identification of neotropical species.

Using mm-scale seafloor roughness to improve monitoring of macrobenthos by remote sensing

NASA Astrophysics Data System (ADS)

Feldens, Peter; Schönke, Mischa; Wilken, Dennis; Papenmeier, Svenja

2017-04-01

In this study, we determine seafloor roughness at mm-scales by laser line-scanning to improve the remote marine habitat monitoring of macrobenthic organisms. Towards this purpose, a new autonomous lander system has been developed. Remote sensing of the seafloor is required to obtain a comprehensive view of the marine environment. It allows for analyzing spatiotemporal dynamics, monitoring of natural seabed variations, and evaluating possible anthropogenic impacts, all being crucial in regard to marine spatial planning as well as the sustainable and economic use of the sea. One aspect of ongoing remote sensing research is the identification of marine life, including both fauna and flora. The monitoring of seafloor fauna - including benthic communities - is mainly done using optical imaging systems and sample retrieval. The identification of new remote sensing indicator variables characteristic for the physical nature of the respective habitat would allow an improved spatial monitoring. A poorly investigated indicator variable is mm-scale seafloor microtopography and -roughness, which can be measured by laser line scanning and in turn strongly affects acoustic scatter. Two field campaigns have been conducted offshore Sylt Island in 2015 and 2016 to measure the microtopography of seafloor covered by sand masons, blue mussels, and oysters and to collect multi-frequency acoustic data. The acoustic data and topography of the blue mussel and oyster fields are currently being analyzed. The mm-scale microtopography of sand mason covered seafloor were transformed into the frequency domain and the average of the magnitude at different spatial wavelengths was used as a measure of roughness. The presence of sand masons causes a measurable difference in roughness magnitude at spatial wavelengths between 0.02 m and 0.0036 m, with the magnitude depending on sand mason abundance. This effect was not detected by commonly used 1D roughness profiles but required consideration of the complete spectrum. The influenced spatial wavelengths correspond to acoustic frequencies of 75 kHz and 400 kHz that are common for acoustic monitoring purposes. The available results indicate that the development of habitat-specific indicator variables, e.g. related to the abundance of sand masons or mussels, is possible and that remote sensing may assist the monitoring of benthic habitats in the future.

Historical ecology of the northern Adriatic Sea: Field methods and coring device

NASA Astrophysics Data System (ADS)

Haselmair, Alexandra; Gallmetzer, Ivo; Tomasovych, Adam; Stachowitsch, Michael; Zuschin, Martin

2014-05-01

For an ongoing study on the historical ecology of the northern Adriatic Sea, the objective was to retrieve a high number of sediment cores at seven sampling stations spread across the entire basin. One set of cores is intended for sediment analyses including radiometric Pb-sediment-dating, grain size, TOC, TAC and heavy metal analyses. The other set of cores delivered enough shelly remains of endo- or epibenthic hard part producers (e.g. molluscs, crustaceans, echinoderms) to enable the reconstruction of death assemblages in core layers from top to bottom. The down-core changes of such assemblages record ecological shifts in a marine environment that has endured strong human impacts over several centuries. A 1.5 m-long core could, according to the available sedimentation data for the area, cover up to 2000 or even more years of ecological history. The coring method had to meet the following requirements: a) deliver 1.5-m-long cores from different sediment settings (mud to sand, reflecting a wide range of benthic habitats in the northern Adriatic); b) enable quick and easy deployment to ensure that multiple cores can be taken at the individual sampling stations within a short time; c) be relatively affordable and allow handling by the researchers themselves, potentially using a small vessel in order to further contain the operating costs. Two types of UWITEC™ piston corers were used to meet these requirements. A model with 90 mm of diameter (samples for sediment analysis) and another one with 160 mm, specifically designed to obtain the large amount of material needed for shell analysis, successfully delivered a total of 54 cores. The device consists of a stabilizing tripod and the interchangeable coring cylinders. It is equipped with a so-called hammer action that makes it possible, at least for the smaller cylinder, to penetrate even harder sediments. A closing mechanism of the corer retains the sediment in the cylinder upon extraction; it works either automatically through hydraulic pressure once the final core-length is reached, or can be triggered manually anytime from the surface using a connected hose and water pump. The whole coring device weighs less than 300 kg and can readily be transported in a van. It can easily be assembled, disassembled and operated by two to three persons after a brief training. With a newly designed, very simple and effective slicing device, the cores can be sliced in an upright position directly on board after extraction. This type of corer can be highly recommended for any smaller coring operations on lakes, streams, or at sea.

Large-scale natural gradient tracer test in sand and gravel, Cape Cod, Massachusetts: 2. Analysis of spatial moments for a nonreactive tracer

USGS Publications Warehouse

Garabedian, Stephen P.; LeBlanc, Dennis R.; Gelhar, Lynn W.; Celia, Michael A.

1991-01-01

A large-scale natural gradient tracer test was conducted to examine the transport of reactive and nonreactive tracers in a sand and gravel aquifer on Cape Cod, Massachusetts. As part of this test the transport of bromide, a nonreactive tracer, was monitored for about 280 m and quantified using spatial moments. The calculated mass of bromide for each sampling date varied between 85% and 105% of the injected mass using an estimated porosity of 0.39, and the center of mass moved at a nearly constant horizontal velocity of 0.42 m per day. A nonlinear change in the bromide longitudinal variance was observed during the first 26 m of travel distance, but afterward the variance followed a linear trend, indicating the longitudinal dispersivity had reached a constant value of 0.96 m. The transverse dispersivities were much smaller; transverse horizontal dispersivity was 1.8 cm, and transverse vertical dispersivity was about 1.5 mm.

Depositional environments and sand body morphologies of the muddy sandstones at Kitty Field, Powder River Basin, Wyoming

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

Larberg, G.M.B.

1980-01-01

Lower Cretaceous muddy sandstones form a stratigraphic trap at Kitty Field, Campbell County, Wyoming. Porosity and permeability are generally low, but the best reservoir develop maximum effective porosity of 17% and maximum permeability of 442 md. Reservoirs sandstones average less than 15 ft and rarely exceed 30 ft in thickness. Ultimate recovery from the field is estimated at 23 million bbl. Based on electric log character, 4 easily recognizable zones within the muddy interval at Kitty were numbered one through 4 in slabbed cores and petrographic analyses of selected core samples, suggest that sandstones in the second, third, and fourthmore » muddy zones were deposited as part of a sequence associated with the overall transgression of the lower Cretaceous sea. Fourth zone sandstones are fluvial in origin, and were deposited in lows on the unconformable surface of the underlying skull creek shale. 18 references.« less

Mapping the Gulf of Maine with side-scan sonar: A new bottom-type classification for complex seafloors

USGS Publications Warehouse

Barnhardt, W.A.; Kelley, J.T.; Dickson, S.M.; Belknap, D.F.

1998-01-01

The bedrock-framed seafloor in the northwestern Gulf of Maine is characterized by extreme changes in bathymetric relief and covered with a wide variety of surficial materials. Traditional methods of mapping cannot accurately represent the great heterogeneity of such a glaciated region. A new mapping scheme for complex seafloors, based primarily on the interpretation of side-scan sonar imagery, utilizes four easily recognized units: rock, gravel, sand and mud. In many places, however, the seafloor exhibits a complicated mixture or extremely 'patchy' distribution of the four basic units, which are too small to map individually. Twelve composite units, each a two-component mixture of the basic units, were established to represent this patchiness at a small scale (1:100,000). Using a geographic information system, these and all other available data (seismic profiles, grab samples, submersible dives and cores) were referenced to a common geographic base, superimposed on bathymetric contours and then integrated into surficial geologic maps of the regional inner continental shelf. This digital representation of the seafloor comprises a multidimensional, interactive model complete with explicit attributes (depth, bottom type) that allow for detailed analysis of marine environments.

JOBS. A Partnership between Education and Industry.

ERIC Educational Resources Information Center

Mann, Sandra; And Others

This packet contains 15 lessons developed in a workplace basic skills project for the metal casting industry established jointly by Central Alabama Community College and Robinson Foundry, Inc. The lessons cover the following topics: (1) green sand schedule; (2) the core room; (3) the core room (continued); (4) figuring time; (5) the cleaning room;…

Sedimentary Environment Changes between Tsunami Events in the Central Fukushima Prefecture, Japan

NASA Astrophysics Data System (ADS)

Kusumoto, S.; Goto, T.; Satake, K.; Sugai, T.; Yoneda, M.; Omori, T.; Ozaki, H.

2016-12-01

Many tsunami deposits were found in the Tohoku region, Japan from recent and past tsunamis. Study of tsunami deposits is particularly important in the central to southern Fukushima Prefecture, which is the southern limit of the distributions of tsunami deposits of the 869 Jogan, 1454 Kyotoku and 1611 Keicho-Sanriku earthquakes. Previous studies reported that there were at least five tsunami deposits (EV1-EV5) consisted of fine-middle sand and the sedimentary environment was inner-bay or lagoon for the past 2,600 years (Goto and Aoyama, 2005; JpGU, Oikawa et al., 2011; JpGU, Oota and Hoyanagi, 2014; GSJ, Kusumoto et al., 2016; JpGU). However, the sedimentary environment changes between or across historical tsunamis have not been examined. In this study, we try to estimate the sedimentary environment changes using Total Organic Carbon (TOC), Total Nitrogen (TN) concentrations and organic Carbon-to-Nitrogen (C/N) ratio. We took 13 geological core samples of length 2.0-2.5 m at 11 locations 0.6-2.7 km from the coast. The deposits consisted of silt and massive sand with graded beddings, laminas and rip-up clasts. For samples, we performed grain-size analysis, radiocarbon age measurement and CN elemental analysis. We found three interesting characteristics. First, grain size of ordinary deposits between EV4 and EV5 tend to fine upward slightly. It suggests that tidal current became gradually weak. Second, C/N ratio is about 5-10 at every depth, meaning that organic material source was phytoplankton or zooplankton (Müller, 1977; GCA). Finally, TOC and TN concentrations slowly increase between EV4 and EV5, and they rapidly decrease across EV3 and EV4. Their slow increases correspond to sedimentary environment change from anaerobic to aerobic, whereas rapid decreases correspond to sedimentary environment change from aerobic to anaerobic. These characteristics might indicate development of sand bar between tsunami events and sudden collapse of sand bar by historical tsunamis.

Laboratory investigation of the erosion of cohesive sediments under oscillatory flows using a synchronized imaging technique

NASA Astrophysics Data System (ADS)

Sou, In Mei; Calantoni, Joseph; Reed, Allen; Furukawa, Yoko

2012-11-01

A synchronized dual stereo particle image velocimetry (PIV) measurement technique is used to examine the erosion process of a cohesive sediment core in the Small Oscillatory Flow Tunnel (S-OFT) in the Sediment Dynamics Laboratory at the Naval Research Laboratory, Stennis Space Center, MS. The dual stereo PIV windows were positioned on either side of a sediment core inserted along the centerline of the S-OFT allowing for a total measurement window of about 20 cm long by 10 cm high with sub-millimeter spacing on resolved velocity vectors. The period of oscillation ranged from 2.86 to 6.12 seconds with constant semi-excursion amplitude in the test section of 9 cm. During the erosion process, Kelvin-Helmholtz instabilities were observed as the flow accelerated in each direction and eventually were broken down when the flow reversed. The relative concentration of suspended sediments under different flow conditions was estimated using the intensity of light scattered from the sediment particles in suspension. By subtracting the initial light scattered from the core, the residual light intensity was assumed to be scattered from suspended sediments eroded from the core. Results from two different sediment core samples of mud and sand mixtures will be presented.

Sea-floor geology of a part of Mamala Bay, Hawaii

USGS Publications Warehouse

Hampton, Monty A.; Torresan, Michael E.; Barber, John H.

1997-01-01

We surveyed the sea-floor geology within a 200-km2 area of Mamala Bay, off Honolulu, Hawaii by collecting and analyzing sidescan sonar images, 3.5-kHz profiles, video and still visual images, and box-core samples. The study area extends from 20-m water depth on the insular shelf to 600-m water depth in a southeast-trending trough. The sidescan images depict three principal types of sea-floor material: low-backscatter natural sediment, high-backscatter drowned carbonate reef, and intermediate-backscatter dredged-material deposits. Cores indicate that the natural sediment is muddy sand, composed of carbonate reef and microfauna debris with some volcanic grains. Vague areal trends in composition are evident. The dredged material comprises poorly sorted, cobble- to clay-size mixtures of reef, volcanic, and man-made debris, up to 35 cm thick. Dredged-material deposits are not evident in the 3.5-kHz profiles. In the sidescan images they appear as isolated, circular to subcircular imprints, apparently formed by individual drops, around the periphery of their occurrence, but they overlap and coalesce to a nearly continuous, intermediate-backscatter blanket toward the center of three disposal sites investigated. We did not observe significant currents during our camera surveys, but there is abundant evidence of sediment reworking: symmetrical and asymmetrical ripples in the visual images, sand waves in the 3.5-kHz profiles and side-scan images, moats around the reefs in 3.5-kHz profiles, winnowed dredged material in the visual images, and burial of dredged material by natural sediment in cores. Most current indicators imply a westerly to northwesterly transport direction, along contours or up-slope, although there are a few areas of easterly indicators. Internal waves probably drive the transport; their possible existence is implied by measured water-column density gradients.

Sea-floor geology of a part of Mamala Bay, Hawai'i

USGS Publications Warehouse

Hampton, M.A.; Torresan, M.E.; Barber, J.H.

1997-01-01

We surveyed the sea-floor geology within a 200-km2 area of Mamala Bay, off Honolulu, Hawai'i, by collecting and analyzing sidescan sonar images, 3.5kHz profiles, video and still visual images, and box-core samples. The study area extends from 20-m water depth on the insular shelf to 600-m water depth in a southeast-trending trough. The sidescan images depict three principal types of seafloor material: low-backscatter natural sediment, high-backscatter drowned carbonate reef, and intermediate-backscatter dredged-material deposits. Cores indicate that the natural sediment is muddy sand, composed of carbonate reef and microfauna debris with some volcanic grains. Vague areal trends in composition are evident. The dredged material comprises poorly sorted, cobble- to clay-size mixtures of reef, volcanic, and man-made debris, up to 35 cm thick. Dredged-material deposits are not evident in the 3.5-kHz profiles. In the sidescan images they appear as isolated, circular to subcircular imprints, apparently formed by individual drops, around the periphery of their occurrence, but they overlap and coalesce to a nearly continuous, intermediate-backscatter blanket toward the center of three disposal sites investigated. We did not observe noticeable currents during our camera surveys, but there is abundant evidence of sediment reworking: symmetrical and asymmetrical ripples in the visual images, sand waves in the 3.5-kHz profiles and side-scan images, moats around the reefs in 3.5-kHz profiles, winnowed dredged material in the visual images, and burial of dredged material by natural sediment in cores. Most current indicators imply a westerly to northwesterly transport direction, along contours or upslope, although there are a few areas of easterly indicators. Internal waves probably drive the transport; their possible existence is implied by measured water-column density gradients.

Diversity of bacteriome associated with Phlebotomus chinensis (Diptera: Psychodidae) sand flies in two wild populations from China

PubMed Central

Li, Kaili; Chen, Huiying; Jiang, Jinjin; Li, Xiangyu; Xu, Jiannong; Ma, Yajun

2016-01-01

Sand fly Phlebotomus chinensis is a primary vector of transmission of visceral leishmaniasis in China. The sand flies have adapted to various ecological niches in distinct ecosystems. Characterization of the microbial structure and function will greatly facilitate the understanding of the sand fly ecology, which would provide critical information for developing intervention strategy for sand fly control. In this study we compared the bacterial composition between two populations of Ph. chinensis from Henan and Sichuan, China. The phylotypes were taxonomically assigned to 29 genera of 19 families in 9 classes of 5 phyla. The core bacteria include Pseudomonas and enterobacteria, both are shared in the sand flies in the two regions. Interestingly, the endosymbionts Wolbachia and Rickettsia were detected only in Henan, while the Rickettsiella and Diplorickettsia only in Sichuan. The intracellular bacteria Rickettsia, Rickettsiella and Diplorickettsia were reported for the first time in sand flies. The influence of sex and feeding status on the microbial structure was also detected in the two populations. The findings suggest that the ecological diversity of sand fly in Sichuan and Henan may contribute to shaping the structure of associated microbiota. The structural classification paves the way to function characterization of the sand fly associated microbiome. PMID:27819272

Geologic and paleoecologic studies of the Nebraska Sand Hills

USGS Publications Warehouse

Ahlbrandt, Thomas S.; Fryberger, S.G.; Hanley, John H.; Bradbury, J. Platt

1980-01-01

PART A: The Nebraska Sand Hills are an inactive, late Quaternary, most probably Holocene, dune field (covering 57,000 km 2 ) that have been eroded along streams and in blowouts, resulting in excellent lateral and vertical exposures of the stratification of dune and interdune sediments. This paper presents new data on the geometry, primary sedimentary structures, modification of sedimentary structures, direction of sand movement, and petrography of these eolian deposits. Eolian deposits of the Sand Hills occur as relatively thin (9-24 m) 'blanket' sands, composed of a complex of dune and discontinuous, diachronous interdune deposits unconformably overlying fluviolacustrine sediments. The internal stratification of large dunes in the Sand Hills (as high as 100 m), is similar to the internal stratification of smaller dunes of the same type in the Sand Hills, differing only in scale. Studies of laminae orientation in the Sand Hills indicate that transverse, barchan, and blowout dunes can be differentiated in rocks of eolian origin using both the mean dip angle of laminae and the mean angular deviation of dip direction. A variety of secondary structures modify or replace primary eolian stratification in the Sand Hills, the more common of which are dissipation structures and bioturbation. Dissipation structures in the Sand Hills may develop when infiltrating water deposits clay adjacent to less permeable layers in the sand, or along the upper margins of frozen layers that form in the sands during winter. Cross-bed measurements from dunes of the Nebraska Sand Hills necessitate a new interpretation of the past sand transport directions. The data from these measurements indicate a general northwest-to-southeast drift of sand, with a more southerly drift in the southeast part of the Sand Hills. A large area of small dunes < 100 m high) described by Smith (1965) as linear or seif in the central part of the Sand Hills was interpreted by him on the basis of morphology only. We interpret these as transverse-ridge dunes that were generally moving to the south. Further, our measurements indicate that dunes in the western part of the Sand Hills did not develop in response to present-day effective wind regimes. The presence of 'transverse' and en echelon barchan dunes in the Sand Hills corresponds to a developmental sequence of barchan to linear dunes proposed by Tsoar (1978). Dune and interdune deposits of the Sand Hills are subfeldsarenites to feldsarenites. Sand grains are commonly coated with montmorillonitic clay, which may be the local source of the clay concentrated in the dissipation structures. Textures of sand samples taken from adjacent layers within a dune were as dissimilar as textures of samples taken from widely separated dunes. This common occurrence indicates that textural data must be used carefully and in combination with other data to recognize ancient rocks of eolian origin. Organic material derived from a variety of flora and fauna that inhabit the interdunes (chapters B and C) generated both oil and gas upon heating. Thus, interdune sediments may be an indigenous hydrocarbon source if buried in eolianites. The twofold stratigraphy of loess and correlative dune deposits in the Sand Hills proposed by Reed and Dreeszen (1965) could not be confirmed by the present study. Rather, available data indicate that the dunes represent a single formation as suggested by Lugn (1935). PART B: Three assemblages of nonmarine Mollusca from paleointerdune deposits in the Nebraska Sand Hills inhabited shallow, quiet, vegetated, subpermanent or temporary, freshwater interdune ponds and adjacent terrestrial habitats. Analysis of factors affecting the taxonomic composition, diversity, and abundance of species in living assemblages of mollusks support this interpretation. The mollusks have long biostratigraphic ranges and broad biogeographic distributions. They fail to establish precise age relations of the faunas othe

Characterization of channel substrate, and changes in suspended-sediment transport and channel geometry in white sturgeon spawning habitat in the Kootenai River near Bonners Ferry, Idaho, following the closure of Libby Dam

USGS Publications Warehouse

Barton, Gary J.

2004-01-01

Many local, State, and Federal agencies have concerns over the declining population of white sturgeon (Acipenser transmontanus) in the Kootenai River and the possible effects of the closure and subsequent operation of Libby Dam in 1972. In 1994, the Kootenai River white sturgeon was listed as an Endangered Species. A year-long field study was conducted in cooperation with the Kootenai Tribe of Idaho along a 21.7-kilometer reach of the Kootenai River including the white sturgeon spawning reach near Bonners Ferry, Idaho, approximately 111 to 129 kilometers below Libby Dam. During the field study, data were collected in order to map the channel substrate in the white sturgeon spawning reach. These data include seismic subbottom profiles at 18 cross sections of the river and sediment cores taken at or near the seismic cross sections. The effect that Libby Dam has on the Kootenai River white sturgeon spawning substrate was analyzed in terms of changes in suspended-sediment transport, aggradation and degradation of channel bed, and changes in the particle size of bed material with depth below the riverbed. The annual suspended-sediment load leaving the Kootenai River white sturgeon spawning reach decreased dramatically after the closure of Libby Dam in 1972: mean annual pre-Libby Dam load during 1966–71 was 1,743,900 metric tons, and the dam-era load during 1973–83 was 287,500 metric tons. The amount of sand-size particles in three suspended-sediment samples collected at Copeland, Idaho, 159 kilometers below Libby Dam, during spring and early summer high flows after the closure of Libby Dam is less than in four samples collected during the pre-Libby Dam era. The supply of sand to the spawning reach is currently less due to the reduction of high flows and a loss of 70 percent of the basin after the closure of Libby Dam. The river's reduced capacity to transport sand out of the spawning reach is compensated to an unknown extent by a reduced load of sand entering the spawning reach. Since the closure of Libby Dam, the most notable change in channel geometry at the Copeland streamflow gaging station was the initiation of cyclical aggradation and degradation of the riverbed in the center of the channel. The aggradation and degradation of the riverbed are reflected in a twofold increase, from 1.3 to 2.5 meters, in the fluctuation of the minimum riverbed elevation, which suggests that during the Libby Dam era, parts of the riverbed in the spawning reach may have aggraded or degraded by as much as 2.5 meters. Before the closure of Libby Dam, there was a greater propensity for aggradation and degradation of sand over the discontinuous gravel and cobble layers in the buried gravelcobble reach at Bonners Ferry. The gravel and cobble in this reach, 111.3 to 115.9 kilometers below Libby Dam, are buried by sand. Unregulated spring snowmelt-runoff flows flushed part of the sand layer and exposed some of the buried gravel-cobble layer because streamflow velocities were higher at that time. Unregulated autumn-winter base flows gradually deposited silt and sand and reestablished a sand layer, burying the gravel-cobble layer. This cyclical process of aggradation and degradation of the riverbed sediment is reflected in the alternating gravel-cobble layers and sand layers found in sediment core K18-TH taken as part of this project. White sturgeon spawning substrate in the Kootenai River meander reach is currently composed of alluvial sand that forms sand dunes and of minor amounts of lacustrine clay and silt that generally are found in the river's thalweg. The present substrate composition in the meander reach is considered similar to that which existed prior to closure of Libby Dam, with one possible exception. Prior to closure of Libby Dam, minor amounts of gravel and cobble may have been exposed on the riverbed in the spawning reach just below the mouth of Myrtle Creek 230 kilometers below Libby Dam. The substrate composition near Shorty Island, 234 kilometers below Libby Dam, a notable white sturgeon spawning reach, is predominantly sand and is similar to that which existed prior to closure of Libby Dam.

Directional optical transmission through a sand layer: a preliminary laboratory experiment

NASA Astrophysics Data System (ADS)

Tian, Jia; Philpot, William D.

2017-10-01

Given the importance of penetration of light in the soil for seed germination, soil warming, and the photolytic degradation of pesticides, directional transmission of thin sand samples are studied in this paper under both dry and saturated conditions. The detector views upward through a glass-bottom sample holder, filled to 3 or 4 mm with a coarse, translucent, quartz sand sample. Transmission through the samples was measured as the illumination zenith angle moved from 0 to 70° in 5° intervals. In the most cases, transmission decreased monotonically, but slowly with increasing illumination angle at all wavelengths. A peak in transmission only appeared at 0° illumination for the low bulk density, dry sample at 3 mm depth. The 0° peak disappeared when the sample was wetted, when the bulk density increased, or when the depth of the sample increased, which indicates that the radiation transmitting through a sand layer can be diffused thoroughly with a millimeters-thin sand layer. For the saturated samples, water influences light transmission in contrasting ways in shorter and longer wavelength. Transmission increased in the VNIR when saturated relative to dry, while transmission decreased sharply after 1300 nm, with spectral absorption features characteristic of water absorption. In VNIR region, water absorption is low and the low relative index of refraction enhanced transmission through sand sample. In contrast, water absorption became dominant at longer wavelengths region leading to the strongly reduced transmission.

Pore-Water Quality in the Clay-Silt Confining Units of the Lower Miocene Kirkwood Formation and Hypothetical Effects on Water Quality in the Atlantic City 800-Foot Sand, Northeastern Cape May County, New Jersey, 2001

USGS Publications Warehouse

Szabo, Zoltan; Keller, Elizabeth A.; Defawe, Rose M.

2006-01-01

Pore water was extracted from clay-silt core samples collected from a borehole at Ocean View, west of Sea Isle City, in northeastern Cape May County, New Jersey. The borehole intersects the lower Miocene Kirkwood Formation, which includes a thick sand and gravel unit between two clay-silt units. The sand and gravel unit forms a major confined aquifer in the region, known as the Atlantic City 800-foot sand, the major source of potable water along the Atlantic Coast of southern New Jersey. The pore water from the core is of interest because the borehole intersects the aquifer in an area where the ground water is sodium-rich and sulfidic. Locally in the aquifer in central and southern Cape May County, sodium concentrations are near the New Jersey secondary drinking-water standard of 50 mg/L (milligrams per liter), and typically are greater than 30 mg/L, but chloride and sulfate do not approach their respective secondary drinking-water standards except in southernmost Cape May County. Pore waters from the confining units are suspected to be a source of sodium, sulfur, and chloride to the aquifer. Constituent concentrations in filtered pore-water samples were determined using the inductively coupled plasma-mass spectrometry analytical technique to facilitate the determination of low-level concentrations of many trace constituents. Calcium-sodium-sulfate-bicarbonate, calcium-chloride-sulfate, calcium-sulfate, and sodium-sulfate-chloride-bicarbonate type waters characterize samples from the deepest part of the confining unit directly overlying the aquifer (termed the 'lower' confining unit). A sodium-chloride-sulfate type water is dominant in the composite confining unit below the aquifer. Sodium, chloride, and sulfate became increasingly dominant with depth. Pore water from the deepest sample recovered (1,390 ft (feet) below land surface) was brackish, with concentrations of sodium, chloride, and sulfate of 5,930, 8,400, and 5,070 mg/L, respectively. Pore-water samples from 900 ft or less below land surface, although mineralized, were fresh, not brackish. Sodium concentrations ranged from 51.3 to 513 mg/L, with the maximum concentration found at 882 ft below land surface in the composite confining unit below the aquifer. Chloride concentrations ranged from 46.4 to 757 mg/L, with the maximum concentration found at 596 ft below land surface in the 'lower' confining unit, and were higher than those in pore water from the same units at Atlantic City, N.J. Concentrations of chloride in the composite confining unit below the aquifer were consistently greater than 250 mg/L, indicating that the confining unit can be a source of chloride at depth. Of the major anions, sulfate was the constituent whose concentration varied most, ranging from 42 to 799 mg/L. The maximum concentration was found at 406 ft below land surface, in the upper part of the confining unit overlying the aquifer and the Rio Grande water-bearing zone (termed the 'upper' confining unit). Sulfide was not detected in any pore-water sample despite the presence of abundant quantities of sulfate and sulfide in the aquifer. The absence of sulfide in the pore waters is consistent with the hypothesis that sulfate is reduced in the aquifer. The presence of arsenic, at concentrations ranging from 0.0062 to 0.0374 mg/L, is consistent with the absence of sulfide and the possible presence of iron in the pore water.

Microbiological and mycological beach sand quality in a volcanic environment: Madeira archipelago, Portugal.

PubMed

Pereira, Elisabete; Figueira, Celso; Aguiar, Nuno; Vasconcelos, Rita; Vasconcelos, Sílvia; Calado, Graça; Brandão, João; Prada, Susana

2013-09-01

Madeira forms a mid-Atlantic volcanic archipelago, whose economy is largely dependent on tourism. There, one can encounter different types of sand beach: natural basaltic, natural calcareous and artificial calcareous. Microbiological and mycological quality of the sand was analyzed in two different years. Bacterial indicators were detected in higher number in 2010 (36.7% of the samples) than in 2011 (9.1%). Mycological indicators were detected in a similar percentage of samples in 2010 (68.3%) and 2011 (75%), even though the total number of colonies detected in 2010 was much higher (827 in 41 samples) than in 2011 (427 in 66 samples). Enterococci and potentially pathogenic and allergenic fungi (particularly Penicillium sp.) were the most common indicators detected in both years. Candida sp. yeast was also commonly detected in the samples. The analysis of the 3rd quartile and maximum numbers of all indicators in samples showed that artificial beaches tend to be more contaminated than the natural ones. However, a significant difference between the variables was lacking. More monitoring data (number of bathers, sea birds, radiation intensity variation, and a greater number of samples) should be collected in order to confirm if these differences are significant. In general, the sand quality in the archipelago's beaches was good. As the sand may be a vector of diseases, an international common set of indicators and values and a compatible methodologies for assessing sand contamination, should be defined, in order to provide the bather's with an indication of beach sand quality, rather than only the water. Copyright © 2013 Elsevier B.V. All rights reserved.

Non-cohesive silt turbidity current flow processes; insights from proximal sandy-silt and silty-sand turbidites, Fiordland, New Zealand

NASA Astrophysics Data System (ADS)

Strachan, Lorna J.; Bostock, Helen C.; Barnes, Philip M.; Neil, Helen L.; Gosling, Matthew

2016-08-01

Silt-rich turbidites are commonly interpreted as distal marine deposits. They are associated with interlaminated clay and silt deposition from the upper and rear portions of turbidity currents. Here, multibeam bathymetry and shallow sediment core data from the intra-slope Secretary Basin, Fiordland, New Zealand, located < 10 km from shore, are used to describe a suite of late Holocene proximal sandy-silt and silty-sand turbidites that contain negligible clay and a wide variety of vertical grading patterns. The steep, rugged catchment to the Secretary Basin is dominated by a complex tributary turbidite channel network that feeds the low gradient Secretary Basin floor intra-slope lobe. Sediment core T49 is located within the lobe and positioned between shallow channels that are prone to deposition from decelerating, silty-sand and sandy-silt turbidity currents. The wide variety of sedimentary structures and vertical grading patterns, dominated by inversely graded beds, implies a range of non-cohesive flow processes, with deposition from multiphase, mixed mode (turbulent and laminar) flows that have undergone a variety of up-dip flow transformations. Most flows were initially erosive followed by deposition of partitioned 2- or 3- phase mixed mode flows that include high-density transitional and laminar flows that can be fore- or after-runners to low-density turbulent flow sections. Turbulence is inferred to have been suppressed in high-density flows by increasing flow concentration of both sands and silts. The very fine and fine sand modal grain sizes of sandy-silt and silty-sand turbidites are significantly coarser than classical abyssal plain silt turbidites and are generally coarser than overbank silt turbidites. While the low percentage of clays within Secretary Basin sandy-silt and silty-sand turbidites represents a fundamental difference between these and other silt and mud turbidites, we suggest these beds represent a previously undescribed suite of proximal continental slope deposits.

Multi-level slug tests in highly permeable formations: 2. Hydraulic conductivity identification, method verification, and field applications

USGS Publications Warehouse

Zlotnik, V.A.; McGuire, V.L.

1998-01-01

Using the developed theory and modified Springer-Gelhar (SG) model, an identification method is proposed for estimating hydraulic conductivity from multi-level slug tests. The computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double-packer system. Field verification of the method was performed at a specially designed fully penetrating well of 0.1-m diameter with a 10-m screen in a sand and gravel alluvial aquifer (MSEA site, Shelton, Nebraska). During well installation, disturbed core samples were collected every 0.6 m using a split-spoon sampler. Vertical profiles of hydraulic conductivity were produced on the basis of grain-size analysis of the disturbed core samples. These results closely correlate with the vertical profile of horizontal hydraulic conductivity obtained by interpreting multi-level slug test responses using the modified SG model. The identification method was applied to interpret the response from 474 slug tests in 156 locations at the MSEA site. More than 60% of responses were oscillatory. The method produced a good match to experimental data for both oscillatory and monotonic responses using an automated curve matching procedure. The proposed method allowed us to drastically increase the efficiency of each well used for aquifer characterization and to process massive arrays of field data. Recommendations generalizing this experience to massive application of the proposed method are developed.Using the developed theory and modified Springer-Gelhar (SG) model, an identification method is proposed for estimating hydraulic conductivity from multi-level slug tests. The computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double-packer system. Field verification of the method was performed at a specially designed fully penetrating well of 0.1-m diameter with a 10-m screen in a sand and gravel alluvial aquifer (MSEA site, Shelton, Nebraska). During well installation, disturbed core samples were collected every 0.6 m using a split-spoon sampler. Vertical profiles of hydraulic conductivity were produced on the basis of grain-size analysis of the disturbed core samples. These results closely correlate with the vertical profile of horizontal hydraulic conductivity obtained by interpreting multi-level slug test responses using the modified SG model. The identification method was applied to interpret the response from 474 slug tests in 156 locations at the MSEA site. More than 60% of responses were oscillatory. The method produced a good match to experimental data for both oscillatory and monotonic responses using an automated curve matching procedure. The proposed method allowed us to drastically increase the efficiency of each well used for aquifer characterization and to process massive arrays of field data. Recommendations generalizing this experience to massive application of the proposed method are developed.

Assessment of nitrification in groundwater filters for drinking water production by qPCR and activity measurement.

PubMed

de Vet, W W J M; Kleerebezem, R; van der Wielen, P W J J; Rietveld, L C; van Loosdrecht, M C M

2011-07-01

In groundwater treatment for drinking water production, the causes of nitrification problems and the effectiveness of process optimization in rapid sand filters are often not clear. To assess both issues, the performance of a full-scale groundwater filter with nitrification problems and another filter with complete nitrification and pretreatment by subsurface aeration was monitored over nine months. Quantitative real-time polymerase chain reaction (qPCR) targeting the amoA gene of bacteria and archaea and activity measurements of ammonia oxidation were used to regularly evaluate water and filter sand samples. Results demonstrated that subsurface aeration stimulated the growth of ammonia-oxidizing prokaryotes (AOP) in the aquifer. Cell balances, using qPCR counts of AOP for each filter, showed that the inoculated AOP numbers from the aquifer were marginal compared with AOP numbers detected in the filter. Excessive washout of AOP was not observed and did not cause the nitrification problems. Ammonia-oxidizing archaea grew in both filters, but only in low numbers compared to bacteria. The cell-specific nitrification rate in the sand and backwash water samples was high for the subsurface aerated filter, but systematically much lower for the filter with nitrification problems. From this, we conclude that incomplete nitrification was caused by nutrient limitation. Copyright © 2011 Elsevier Ltd. All rights reserved.

Limited effectiveness of household sand filters for removal of arsenic from well water in North Vietnam.

PubMed

Ilmiawati, Cimi; Thang, Nguyen Dinh; Iida, Machiko; Maeda, Masao; Ohnuma, Shoko; Yajima, Ichiro; Ohgami, Nobutaka; Oshino, Reina; Al Hossain, M M Aeorangajeb; Ninomiya, Hiromasa; Kato, Masashi

2016-12-01

Since well water utilized for domestic purposes in the Red River Delta of North Vietnam has been reported to be polluted by arsenic, barium, iron, and manganese, household sand filters consisting of various components are used. Information regarding the effectiveness of various sand filters for removal of the four toxic elements in well water is limited. In this study, arsenic levels in 13/20 of well water samples and 1/7 of tap water samples exceeded World Health Organization (WHO) health-based guideline value for drinking water. Moreover, 2/20, 6/20, and 4/20 of well water samples had levels exceeding the present and previous guideline levels for barium, iron, and manganese, respectively. Levels of iron and manganese, but not arsenic, in well water treated by sand filters were lower than those in untreated water, although previous studies showed that sand filters removed all of those elements from water. A low ratio of iron/arsenic in well water may not be sufficient for efficient removal of arsenic from household sand filters. The levels of barium in well water treated by sand filters, especially a filter composed of sand and charcoal, were significantly lower than those in untreated water. Thus, we demonstrated characteristics of sand filters in North Vietnam.

Evaluating the reliability of equilibrium dissolution assumption from residual gasoline in contact with water saturated sands

NASA Astrophysics Data System (ADS)

Lekmine, Greg; Sookhak Lari, Kaveh; Johnston, Colin D.; Bastow, Trevor P.; Rayner, John L.; Davis, Greg B.

2017-01-01

Understanding dissolution dynamics of hazardous compounds from complex gasoline mixtures is a key to long-term predictions of groundwater risks. The aim of this study was to investigate if the local equilibrium assumption for BTEX and TMBs (trimethylbenzenes) dissolution was valid under variable saturation in two dimensional flow conditions and evaluate the impact of local heterogeneities when equilibrium is verified at the scale of investigation. An initial residual gasoline saturation was established over the upper two-thirds of a water saturated sand pack. A constant horizontal pore velocity was maintained and water samples were recovered across 38 sampling ports over 141 days. Inside the residual NAPL zone, BTEX and TMBs dissolution curves were in agreement with the TMVOC model based on the local equilibrium assumption. Results compared to previous numerical studies suggest the presence of small scale dissolution fingering created perpendicular to the horizontal dissolution front, mainly triggered by heterogeneities in the medium structure and the local NAPL residual saturation. In the transition zone, TMVOC was able to represent a range of behaviours exhibited by the data, confirming equilibrium or near-equilibrium dissolution at the scale of investigation. The model locally showed discrepancies with the most soluble compounds, i.e. benzene and toluene, due to local heterogeneities exhibiting that at lower scale flow bypassing and channelling may have occurred. In these conditions mass transfer rates were still high enough to fall under the equilibrium assumption in TMVOC at the scale of investigation. Comparisons with other models involving upscaled mass transfer rates demonstrated that such approximations with TMVOC could lead to overestimate BTEX dissolution rates and underestimate the total remediation time.

Evaluating the reliability of equilibrium dissolution assumption from residual gasoline in contact with water saturated sands.

PubMed

Lekmine, Greg; Sookhak Lari, Kaveh; Johnston, Colin D; Bastow, Trevor P; Rayner, John L; Davis, Greg B

2017-01-01

Understanding dissolution dynamics of hazardous compounds from complex gasoline mixtures is a key to long-term predictions of groundwater risks. The aim of this study was to investigate if the local equilibrium assumption for BTEX and TMBs (trimethylbenzenes) dissolution was valid under variable saturation in two dimensional flow conditions and evaluate the impact of local heterogeneities when equilibrium is verified at the scale of investigation. An initial residual gasoline saturation was established over the upper two-thirds of a water saturated sand pack. A constant horizontal pore velocity was maintained and water samples were recovered across 38 sampling ports over 141days. Inside the residual NAPL zone, BTEX and TMBs dissolution curves were in agreement with the TMVOC model based on the local equilibrium assumption. Results compared to previous numerical studies suggest the presence of small scale dissolution fingering created perpendicular to the horizontal dissolution front, mainly triggered by heterogeneities in the medium structure and the local NAPL residual saturation. In the transition zone, TMVOC was able to represent a range of behaviours exhibited by the data, confirming equilibrium or near-equilibrium dissolution at the scale of investigation. The model locally showed discrepancies with the most soluble compounds, i.e. benzene and toluene, due to local heterogeneities exhibiting that at lower scale flow bypassing and channelling may have occurred. In these conditions mass transfer rates were still high enough to fall under the equilibrium assumption in TMVOC at the scale of investigation. Comparisons with other models involving upscaled mass transfer rates demonstrated that such approximations with TMVOC could lead to overestimate BTEX dissolution rates and underestimate the total remediation time. Copyright © 2016. Published by Elsevier B.V.

Community variability of bacteria in alpine snow (Mont Blanc) containing Saharan dust deposition and their snow colonisation potential.

PubMed

Chuvochina, Maria S; Marie, Dominique; Chevaillier, Servanne; Petit, Jean-Robert; Normand, Philippe; Alekhina, Irina A; Bulat, Sergey A

2011-01-01

Microorganisms uplifted during dust storms survive long-range transport in the atmosphere and could colonize high-altitude snow. Bacterial communities in alpine snow on a Mont Blanc glacier, associated with four depositions of Saharan dust during the period 2006-2009, were studied using 16S rRNA gene sequencing and flow cytometry. Also, sand from the Tunisian Sahara, Saharan dust collected in Grenoble and Mont Blanc snow containing no Saharan dust (one sample of each) were analyzed. The bacterial community composition varied significantly in snow containing four dust depositions over a 3-year period. Out of 61 phylotypes recovered from dusty snow, only three phylotypes were detected in more than one sample. Overall, 15 phylotypes were recognized as potential snow colonizers. For snow samples, these phylotypes belonged to Actinobacteria, Proteobacteria and Cyanobacteria, while for Saharan sand/dust samples they belonged to Actinobacteria, Bacteroidetes, Deinococcus-Thermus and Proteobacteria. Thus, regardless of the time-scale, Saharan dust events can bring different microbiota with no common species set to alpine glaciers. This seems to be defined more by event peculiarities and aeolian transport conditions than by the bacterial load from the original dust source.

Presence of Campylobacter and Salmonella in sand from bathing beaches.

PubMed Central

Bolton, F. J.; Surman, S. B.; Martin, K.; Wareing, D. R.; Humphrey, T. J.

1999-01-01

The purpose of this study was to determine the presence of thermophilic Campylobacter spp. and Salmonella spp. in sand from non-EEC standard and EEC standard designated beaches in different locations in the UK and to assess if potentially pathogenic strains were present. Campylobacter spp. were detected in 82/182 (45%) of sand samples and Salmonella spp. in 10/182 (6%). Campylobacter spp. were isolated from 46/92 (50%) of samples from non-EEC standard beaches and 36/90 (40%) from EEC standard beaches. The prevalence of Campylobacter spp. was greater in wet sand from both types of beaches but, surprisingly, more than 30% of samples from dry sand also contained these organisms. The major pathogenic species C. jejuni and C. coli were more prevalent in sand from non-EEC standard beaches. In contrast, C. lari and urease positive thermophilic campylobacters, which are associated with seagulls and other migratory birds, were more prevalent in sand from EEC standard beaches. Campylobacter isolates were further characterized by biotyping and serotyping, which confirmed that strains known to be of types associated with human infections were frequently found in sand on bathing beaches. PMID:10098779

India National Gas Hydrate Program Expedition 02 Technical Contributions

NASA Astrophysics Data System (ADS)

Collett, T. S.; Kumar, P.; Shukla, K. M.; Nagalingam, J.; Lall, M. V.; Yamada, Y.; Schultheiss, P. J.; Holland, M.; Waite, W. F.

2017-12-01

The National Gas Hydrate Program Expedition 02 (NGHP-02) was conducted from 3-March-2015 to 28-July-2015 off the eastern coast of India. The primary objective of this expedition was the exploration and discovery of highly saturated gas hydrate occurrences in sand reservoirs that would be targets of future production testing. The first 2 months of the expedition were dedicated to logging while drilling (LWD) operations with a total of 25 holes being drilled and logged. The next 3 months were dedicated to coring operations at 10 of the most promising sites. NGHP-02 downhole logging, coring and formation pressure testing have confirmed the presence of large, highly saturated, gas hydrate accumulations in coarse-grained sand-rich depositional systems throughout the Krishna-Godavari Basin within the regions defined during NGHP-02 as Area-B, Area-C, and Area-E. The nature of the discovered gas hydrate occurrences closely matched pre-drill predictions, confirming the project developed depositional models for the sand-rich depositional facies in the Krishna-Godavari and Mahanadi Basins. The existence of a fully developed gas hydrate petroleum system was established in Area-C of the Krishna-Godavari Basin with the discovery of a large slope-basin interconnected depositional system, including a sand-rich, gas-hydrate-bearing channel-levee prospect at Sites NGHP-02-08 and -09. The acquisition of closely spaced LWD and core holes in the Area-B L1 Block gas hydrate accumulation have provided one of the most complete three-dimensional petrophysical-based views of any known gas hydrate reservoir system in the world. It was concluded that Area-B and Area-C in the area of the greater Krishna-Godavari Basin contain important world-class gas hydrate accumulations and represent ideal sites for consideration of future gas hydrate production testing.

Structure and builtup of the Middle Bengal Fan at 8°N from multichannel seismic surveys and the IODP Expedition 354 drilling transect

NASA Astrophysics Data System (ADS)

Spiess, V.; Bergmann, F.; Schwenk, T.; Lantzsch, H.; Bahk, J. J.; Weber, M. E.; France-Lanord, C.; Klaus, A.

2016-12-01

IODP Expedition 354 to the Bengal Fan drilled a 320 km long e-W transect at 8°N with 7 drill sites, fully covering the uppermost 150-200 meters of fan deposits at distances of 50 km, originating from Himalayan mountain ranges and the Ganges-Brahmaputra river system. A major goal of this transect approach was to ensure a continuous record of turbiditic material delivered over the last appx. 1 million year, considering frequent longitudinal depocenter shifts of the active channel. By extensively utilizing the new half-APC coring technique, high quality and high recovery cores could be retrieved representing a wide range of grain sizes from hemipelagic deposits through clay rich turbidites to coarse silt and sandy units. Up to medium sand grain sizes were retrieved within the basal units of levees, which correspond to high-reflectivity units in high-resolution multichannel seismic profiles. Finely laminated sections with mm to cm-thick turbidites represents levee formations. At Site U1453 for example, core logging and downhole logging data confirm the representative sampling based on a very good match of several physical property data sets. An expanded section was cored at Site U1454, where the presumably currently active channel has built a levee, which likely represents major sediment supply within the last 30 kyr. A spatial grid of seismic and echosounder data in the vicinity of the active channel reveals a high spatial variability in sedimentation rates and distinct depocenter shifts in response to changes in channel geometry. Site U1452 has provided a full record a levee growth including interlevee sedimentation, sandy basal units characterized by a lobe formation, and a pronounced fining upward trend following the phase of channel erosion and levee builtup. From all sites, detailed comparisons of physical and sedimentological shipboard results with seismic data will be presented. Expedition 354 has provided a unique sample and data set to better understand fan deposition and channel-levee growth including silt and sand grain sizes. It will also provide valuable constraints on the volume, nature and composition of suspension flows contributing to fan growth in the Middle Bengal Fan.

Tracking recent climate and anthropogenic change in Central America in sediments form the lower fan of the Rio Yaqui, Gulf of California, Mexico

NASA Astrophysics Data System (ADS)

Aiello, I. W.; Ravelo, A. C.; Moraes, R.; Swarzenski, P. W.

2015-12-01

We report the results of preliminary sedimentologic analyses of a ~3.3m long piston core (P13) collected in the lower fan of the Rio Yaqui (Guaymas Basin, Gulf of California; depth, 1859m) by UNAM's (Universidad Nacional Autónoma de México) research ship El Puma in 2014. The core was collected to test the potential for high-resolution reconstructions of basin-scale paleoclimate in the Pacific and the Mesoamerican region. Shipboard and post-cruise analyses include magnetic susceptibility (MS), smear slide counts and laser diffraction particle size analysis. The core is being analyzed for X-Ray Fluorescence (XRF) and color reflectance, and a 210Pb age model is being constructed. Preliminary results show that Rio Yaqui lower fan sediment differs significantly from that in the Guaymas Basin, which is dominantly diatom ooze. The lower ~2m of core P13 show prominent alternations (~10-20cm) between very-fine-grained, clay intervals characterized by higher MS and mixed diatom and clay intervals, with coarser grain size and lower MS values. In contrast, the upper ~1m has distinctive high MS sand turbidites alternating with diatom-rich layers. Previous core studies from nearby ODP Leg 64 site show sedimentation rates of ~1.2 m/ka; as these sites are further away from the Yaqui delta the sedimentation rates for core P13 should be higher possibly recording only the last few hundred years of sedimentation. Clay/diatom cycles in the lower part of the core could record decadal- or ENSO-scale wet/aridity cycles in the Sonoran Mainland. Conversely, the coarser siliciclastic intervals and the diatom layers in the upper part of the core could reflect the last few decades of land usage in the watershed of the Rio Yaqui, the most important river in the state of Sonora, Mexico. These include large modifications to the river's hydrography (e.g. construction of dams and aqueducts), rapidly expanding mass agricultural practices in the region, and increased eutrophication in the Gulf.

Development of coring procedures applied to Si, CdTe, and CIGS solar panels

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

Moutinho, H. R.; Johnston, S.; To, B.

Most of the research on the performance and degradation of photovoltaic modules is based on macroscale measurements of device parameters such as efficiency, fill factor, open-circuit voltage, and short-circuit current. Our goal is to develop the capabilities to allow us to study the degradation of these parameters in the micro- and nanometer scale and to relate our results to performance parameters. To achieve this objective, the first step is to be able to access small samples from specific areas of the solar panels without changing the properties of the material. In this paper, we describe two coring procedures that wemore » developed and applied to Si, CIGS, and CdTe solar panels. In the first procedure, we cored full samples, whereas in the second we performed a partial coring that keeps the tempered glass intact. The cored samples were analyzed by different analytical techniques before and after coring, at the same locations, and no damage during the coring procedure was observed.« less

Development of coring procedures applied to Si, CdTe, and CIGS solar panels

DOE PAGES

Moutinho, H. R.; Johnston, S.; To, B.; ...

2018-01-04

Most of the research on the performance and degradation of photovoltaic modules is based on macroscale measurements of device parameters such as efficiency, fill factor, open-circuit voltage, and short-circuit current. Our goal is to develop the capabilities to allow us to study the degradation of these parameters in the micro- and nanometer scale and to relate our results to performance parameters. To achieve this objective, the first step is to be able to access small samples from specific areas of the solar panels without changing the properties of the material. In this paper, we describe two coring procedures that wemore » developed and applied to Si, CIGS, and CdTe solar panels. In the first procedure, we cored full samples, whereas in the second we performed a partial coring that keeps the tempered glass intact. The cored samples were analyzed by different analytical techniques before and after coring, at the same locations, and no damage during the coring procedure was observed.« less

Tar sand extraction by steam stimulation and steam drive: measurement of physical properties

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

Linberg, W.R.

The measurement of the following thermophysical properties of Utah tar sands is in progress: thermal conductivity, specific heat relative permeability, and viscosity (of the recovered bitumen). During the report period (October 1, 1978 to November 1, 1979), experimental procedures have been developed and a basic data set has been measured. Additionally, standard core analysis has been performed for four drill sites in the Asphalt Ridge, Utah area.

Microbial strengthening of loose sand.

PubMed

Banagan, B L; Wertheim, B M; Roth, M J S; Caslake, L F

2010-08-01

To test whether the addition of Flavobacterium johnsoniae could increase the strength of saturated Ottawa 30 sand. A box model was built that simulates groundwater-like flow through a main sand compartment. Strength tests were performed at seven locations and at two depths, 10.8 and 20.3 cm below the top of the tank, using a vane shear device before and after the addition of bacteria. After the addition of Fl. johnsoniae, sand samples were obtained from multiple sampling ports on the vertical sides of the box model. The presence of a bacterial biofilm was confirmed by staining these sand samples with SYTO-9 and Alexa Fluor 633 and viewing with a confocal microscope. The average shear strength increases after the addition of Fl. johnsoniae were 15.2-87.5%, depending on the experimental conditions. Flavobacterium johnsoniae caused a statistically significant increase in the strength of saturated Ottawa 30 sand. Biofilm-forming bacteria can increase the shear strength of saturated sand. The addition of biofilm-forming bacteria to a building site may be an alternate method to mitigate the effects of liquefaction.

Characterizing scale- and location-dependent correlation of water retention parameters with soil physical properties using wavelet techniques.

PubMed

Shu, Qiaosheng; Liu, Zuoxin; Si, Bingcheng

2008-01-01

Understanding the correlation between soil hydraulic parameters and soil physical properties is a prerequisite for the prediction of soil hydraulic properties from soil physical properties. The objective of this study was to examine the scale- and location-dependent correlation between two water retention parameters (alpha and n) in the van Genuchten (1980) function and soil physical properties (sand content, bulk density [Bd], and organic carbon content) using wavelet techniques. Soil samples were collected from a transect from Fuxin, China. Soil water retention curves were measured, and the van Genuchten parameters were obtained through curve fitting. Wavelet coherency analysis was used to elucidate the location- and scale-dependent relationships between these parameters and soil physical properties. Results showed that the wavelet coherence between alpha and sand content was significantly different from red noise at small scales (8-20 m) and from a distance of 30 to 470 m. Their wavelet phase spectrum was predominantly out of phase, indicating negative correlation between these two variables. The strong negative correlation between alpha and Bd existed mainly at medium scales (30-80 m). However, parameter n had a strong positive correlation only with Bd at scales between 20 and 80 m. Neither of the two retention parameters had significant wavelet coherency with organic carbon content. These results suggested that location-dependent scale analyses are necessary to improve the performance for soil water retention characteristic predictions.

Map showing locations and statistical parameters of beach and offshore sand samples, Tutuila Island, American Samoa

USGS Publications Warehouse

Dingler, J.R.; Carlson, D.V.; Sallenger, A.H.

1987-01-01

In April 1985, sand samples were collected from many of the beaches on Tutuila Island, American Samoa, and in July 1985, three bays were surveyed using side-scan sonar and shallow seismic profiling. During that second trip, scuba divers collected sand samples from the surveyed areas. Dingler and others (1986) describes the study; this report presents the grain-size and composition data for the onshore and offshore sand samples. Locations of the onshore samples are plotted on the map of the island, which is reproduced from Normark and others (1985); locations of most of the offshore samples and side-scan sonar interpretations made during the study are plotted on enlargements (A and B, respectively) of Fagaitua and Nua-seetaga Bays. Lam Yuen (1981), U.S. Army Corps of Engineers (1980), and Sea Engineering Services Inc. (1980) provide additional information pertaining to the island's beaches.

Filamentous fungi isolated from sand and water of "Bairro Novo" and "Casa Caiada" beaches, Olinda, Pernambuco, Brazil.

PubMed

Gomes, D N F; Cavalcanti, M A Q; Fernandes, M J S; Lima, D M M; Passavante, J Z O

2008-08-01

Fungi comprehend a heterogeneous group of heterotrophic microorganisms that act as saprobes or parasites or, less frequently, as symbionts living in association with other organisms. They are cosmopolitan and important components of ecosystems. Considering the small number of Brazilian papers on the filamentous mycota in marine environments, and the need to improve knowledge of the diversity of these microfungi in "Casa Caiada" and "Bairro Novo" beaches, Olinda, PE, the aim of this work was to isolate and identify the fungi from sand and water samples of these ecosystems. Thirty two samplings of sand (surface and 20 cm deep) and water (surface and 1 m deep) were carried out during the dry and rainy seasons, in low and high tide. From each sand sample, a suspension was made with 50 g of sand diluted in 90 mL of sterilized distilled water. From each sand suspension and water sample, 0.5 mL was spread, in triplicate, onto Petri dishes containing Sabouraud Agar added of chloramphenicol. The plates were incubated at 28 degrees C (+/-2 degrees C). Fifty seven species were isolated, identified, and classified in 20 genera. Aspergillus and Penicillium were the most frequent genera in both sand and water, with a total of 11 and 19 species, respectively.

The Record of Tsunamis and Storms in a Coastal Mangrove Pond, NW Puerto Rico

NASA Astrophysics Data System (ADS)

Jaffe, B. E.; Buckley, M. L.; Watt, S. G.; Moya, J. C.; Richmond, B. M.; Gelfenbaum, G. R.; La Selle, S.

2017-12-01

The written record of tsunamis in the Caribbean extends back over 500 years, yet, is incomplete. In particular, it is not known whether great earthquakes or submarine landslides near the Puerto Rico Trench have generated large tsunamis that impact the north coast of Puerto Rico. We cored a coastal mangrove pond in NW Puerto Rico to search for tsunami deposits. The pond extends from 150 to 350 m from the shoreline, and is 0.5 m above sea level. The area between the pond and the ocean presently has a high of 3 m above sea level, but had dunes up to 10 m high before they were mined for sand beginning in the 1960s. Pond sediments are predominately mud or mangrove peat and contain prominent sand layers. At the sediment surface, a tabular sandy overwash deposit up to 40 cm thick extends inland approximately 30 m from the pond's seaward edge and abruptly ends. This sand layer contains no evidence of vertical grading and was likely formed by one or more recent hurricanes, which with the removal of coastal dunes in the 1960s are able to flood the pond. In contrast, underlying the overwash deposit and mangrove peat at a depth of approximately 60 cm is a thin (1 - 7 cm thick) sand layer extending to the landward limit of the pond. This layer has features of a tsunami deposit, including suspension grading, which is a specific type of normal grading where the entire grain-size distribution shifts to finer sizes upward that is created when sediment settles out of suspension as a high-speed flow wanes, an erosive basal contact, and an organic cap. In addition, couplets or triplets of sand inter-layered with mud are present within the thin sandy layer at some locations. Alternation of sand and mud layers at this scale is a signature of series of tsunami waves. Radiocarbon dates from organic material above and below the thin sand layer constrain deposition as occurring sometime from 1446 to 1919 AD. We present the features of the coastal mangrove pond deposits and evaluate whether these deposits could be correlated with an extreme wave overwash that left a deposit on Anegada, BVI, sometime between 1200 and 1480 AD, which would support a great Puerto Rico Trench earthquake and tsunami about 600 years ago.

Plume persistence caused by back diffusion from thin clay layers in a sand aquifer following TCE source-zone hydraulic isolation.

PubMed

Parker, Beth L; Chapman, Steven W; Guilbeault, Martin A

2008-11-14

This paper concludes that back diffusion from one or a few thin clayey beds in a sand aquifer can cause contaminant persistence above MCLs in a sand aquifer long after the source zone initially causing the plume is isolated or removed. This conclusion is based on an intensive case study of a TCE contaminated site in Florida, with the processes evaluated using numerical modeling. At this site, the TCE DNAPL zone formed decades ago, and was hydraulically isolated by means of an innovative system performing groundwater extraction, treatment and re-injection. Treated water is re-injected in a row of injection wells situated a short distance downgradient of the extraction wells, creating a clean-water displacement front to efficiently flush the downgradient plume. This scheme avoids the creation of stagnation zones typical of most groundwater pump-and-treat systems, thereby minimizing the time for aquifer flushing and therefore downgradient cleanup. The system began operation in August 2002 and although the performance monitoring shows substantial declines in concentrations, detectable levels of TCE and degradation products persist downgradient of the re-injection wells, long after the TCE should have disappeared based on calculations assuming a nearly homogenous sand aquifer. Three hypotheses were assessed for this plume persistence: 1) incomplete source-zone capture, 2) DNAPL occurrence downgradient of the re-injection wells, and 3) back diffusion from one or more thin clay beds in the aquifer. After careful consideration, the first two hypotheses were eliminated, leaving back diffusion as the only plausible hypothesis, supported by detailed measurements of VOC concentrations within and near the clay beds and also by numerical model simulations that closely represent the field site hydrogeologic conditions. The model was also used to simulate a more generalized, hypothetical situation where more thin clayey beds occur in a sand aquifer with an underlying aquitard. While there is no doubt that DNAPL source mass reduction can eventually improve downgradient groundwater quality, the magnitude and time scale over which the improvement occurs is the major uncertainty given current characterization approaches. This study shows that even one thin clay bed, less than 0.2 m thick, can cause plume persistence due to back diffusion for several years or even decades after the flux from the source is completely isolated. Thin clay beds, which have a large storage capacity for dissolved and sorbed contaminant mass, are common in many types of sandy aquifers. However, without careful inspection of continuous cores and sampling, such thin clay beds, and their potential for causing long-term back-diffusion effects, can easily go unnoticed during site characterization.

Multiscale Geoarchaeological Approaches from the Laurentine Shore, Castelporziano, Lazio, Italy

NASA Astrophysics Data System (ADS)

Bicket, A. R.; Rendell, H. M.; Claridge, A.; Rose, P.; Brown, F. S. J.

2009-04-01

The relationship between the meso-scale record of human activity during the Roman period and the larger-scale coastal development of the Tiber Delta (ca. 20 ka) is investigated using the archaeological and sedimentary record from a large aquaculture pond and its wider meso- to macro-scale geomorphological setting. The position of the pond is adjacent to the Roman period shoreline, known as the Laurentine Shore on the southern, distal flank of the Tiber delta, Lazio Italy, within what is now the Castelporziano Estate. The pond is thought to have been constructed in the wet dune slack behind the active coastal foredune. Magnetometer survey and excavation of the archaeological structures around this pond have shown them to be substantial features ca. 80m in length with high-status Imperial Roman architecture and with evidence for water management. Sedimentological analysis of sediment cores from within the ponds are supplemented with diatom analysis to assess the period of pre-construction, use and abandonment of this aquaculture pond. Diatom analysis suggests a relatively short period of use and it is argued that abandonment of the aquaculture structures may be linked to both alkali groundwater conditions and the dynamism of the coastal zone preventing effective management. Optical luminescence dating of the archaeological sediments and the post-abandonment dunes that bury part of the site suggest that the aquaculture pond was abandoned ca. 100 years prior to final abandonment of the Roman settlement. This case-study also highlights the implications for meso-scale investigations of human/environment relationships utilising relatively low-sensitivity sedimentary records without high-resolution proxy records. D-GPS survey in conjunction with a high-quality DEM has permitted important archaeological remains to be understood relative to sea level; a key variable for examining the formation and development of the dune ridge record. These surveys have also permitted the effective mapping of dune ridges, from aerial photography, under the extremely dense vegetation that hinders easy access across much of the site. The D-GPS georeferenced DEM has been linked to the diatom analysis of a cored salt marsh to peat sediment transition providing valuable biostratigraphic information for deriving an accurate measurement of the Roman period sea level (Lambeck et al., 2004a). This measurement is in line with published literature from nearby coastal sites, ca. - 1.3m RSL (Lambeck et al., 2004b). Understanding the sites geomorphological development in the context of eustatic sea level is a key consideration for issues of sand supply driving dune formation, linked ultimately to the development of the Tiber Delta since the Last Glacial Maximum and throughout the Holocene. On this larger spatial scale, the archaeological sites described within the Laurentine Shore, built upon the Roman period coastline, are now preserved several hundred metres inland of the contemporary shoreline. The development of the shoreline can now be investigated within the macro-scale progradation of the Tiber delta relative to eustatic sea level rise. Archaeological excavations since the 1980's have provided a rich record of high status villas, and also the supporting infrastructure of a village settlement (vicus), roads, aqueduct and the large aquaculture ponds. The dominant geomorphological features on the site are preserved coastal dune ridges. Sampling was undertaken along an alongshore transect and three inland transects. This sampling regime focuses upon the contemporary deposition of sands on the beach and the phases of dune formation, preservation and alteration recorded by the relict dune crests in relation to the archaeological record. A campaign of optical dating of the relict dune crests has provided a Late Pleistocene and Holocene record of sandsheet and dune formation linked to delta progradation that permits the larger spatial- and temporal-scale context of the archaeological record to be discussed. Sedimentary petrology techniques allow the provenance and transportation dynamics of both the sand-sized and dust-sized sediments to be assessed. Furthermore this approach also enables an investigation of carbonate and iron oxide diagenetic cements, which are an important product of the long-term in situ weathering of the dune ridges' mineralogical assemblages, but is also a feature of short-term weathering of archaeological contexts. This work has implications for locations of interest to geoarchaeological surveys. There are also important implications for the mineralogy, provenance and preservation of luminescent minerals; and some form mineralogical/provenance analysis is recommended for all optical dating studies as a result. In summary, the geoarchaeological approach undertaken at Castelporziano allows the meso-scale human/environment interactions to be considered within the broader temporal scales of the late Quaternary. It also permits consideration within the macro-spatial scales of the Tiber Delta's development during the last 15-20ka within the context of eustatic sea level rise. REFERENCES LAMBECK, K., ANTONIOLI, F., PURCELL, A. & SILENZI, S. (2004a) Sea-level change along the Italian coast for the past 10,000 yr. Quaternary Science Reviews, 23, 1567-1598. LAMBECK, K., ANZIDEI, M., ANTONIOLI, F., BENINI, A. & ESPOSITO, A. (2004b) Sea level in Roman time in the Central Mediterranean and implications for recent change. Earth and Planetary Science Letters, 224, 563-575.

Impact on demersal fish of a large-scale and deep sand extraction site with ecosystem-based landscaped sandbars

NASA Astrophysics Data System (ADS)

de Jong, Maarten F.; Baptist, Martin J.; van Hal, Ralf; de Boois, Ingeborg J.; Lindeboom, Han J.; Hoekstra, Piet

2014-06-01

For the seaward harbour extension of the Port of Rotterdam in the Netherlands, approximately 220 million m3 sand was extracted between 2009 and 2013. In order to decrease the surface area of direct impact, the authorities permitted deep sand extraction, down to 20 m below the seabed. Biological and physical impacts of large-scale and deep sand extraction are still being investigated and largely unknown. For this reason, we investigated the colonization of demersal fish in a deep sand extraction site. Two sandbars were artificially created by selective dredging, copying naturally occurring meso-scale bedforms to increase habitat heterogeneity and increasing post-dredging benthic and demersal fish species richness and biomass. Significant differences in demersal fish species assemblages in the sand extraction site were associated with variables such as water depth, median grain size, fraction of very fine sand, biomass of white furrow shell (Abra alba) and time after the cessation of sand extraction. Large quantities of undigested crushed white furrow shell fragments were found in all stomachs and intestines of plaice (Pleuronectes platessa), indicating that it is an important prey item. One and two years after cessation, a significant 20-fold increase in demersal fish biomass was observed in deep parts of the extraction site. In the troughs of a landscaped sandbar however, a significant drop in biomass down to reference levels and a significant change in species assemblage was observed two years after cessation. The fish assemblage at the crests of the sandbars differed significantly from the troughs with tub gurnard (Chelidonichthys lucerna) being a Dufrêne-Legendre indicator species of the crests. This is a first indication of the applicability of landscaping techniques to induce heterogeneity of the seabed although it remains difficult to draw a strong conclusion due the lack of replication in the experiment. A new ecological equilibrium is not reached after 2 years since biotic and abiotic variables are still adapting. To understand the final impact of deep and large-scale sand extraction on demersal fish, we recommend monitoring for a longer period, at least for a period of six years or even longer.

Chemical mass transport between fluid fine tailings and the overlying water cover of an oil sands end pit lake

NASA Astrophysics Data System (ADS)

Dompierre, Kathryn A.; Barbour, S. Lee; North, Rebecca L.; Carey, Sean K.; Lindsay, Matthew B. J.

2017-06-01

Fluid fine tailings (FFT) are a principal by-product of the bitumen extraction process at oil sands mines. Base Mine Lake (BML)—the first full-scale demonstration oil sands end pit lake (EPL)—contains approximately 1.9 × 108 m3 of FFT stored under a water cover within a decommissioned mine pit. Chemical mass transfer from the FFT to the water cover can occur via two key processes: (1) advection-dispersion driven by tailings settlement; and (2) FFT disturbance due to fluid movement in the water cover. Dissolved chloride (Cl) was used to evaluate the water cover mass balance and to track mass transport within the underlying FFT based on field sampling and numerical modeling. Results indicated that FFT was the dominant Cl source to the water cover and that the FFT is exhibiting a transient advection-dispersion mass transport regime with intermittent disturbance near the FFT-water interface. The advective pore water flux was estimated by the mass balance to be 0.002 m3 m-2 d-1, which represents 0.73 m of FFT settlement per year. However, the FFT pore water Cl concentrations and corresponding mass transport simulations indicated that advection rates and disturbance depths vary between sample locations. The disturbance depth was estimated to vary with location between 0.75 and 0.95 m. This investigation provides valuable insight for assessing the geochemical evolution of the water cover and performance of EPLs as an oil sands reclamation strategy.

Contrasting styles of large-scale displacement of unconsolidated sand: examples from the early Jurassic Navajo Sandstone on the Colorado Plateau, USA

NASA Astrophysics Data System (ADS)

Bryant, Gerald

2015-04-01

Large-scale soft-sediment deformation features in the Navajo Sandstone have been a topic of interest for nearly 40 years, ever since they were first explored as a criterion for discriminating between marine and continental processes in the depositional environment. For much of this time, evidence for large-scale sediment displacements was commonly attributed to processes of mass wasting. That is, gravity-driven movements of surficial sand. These slope failures were attributed to the inherent susceptibility of dune sand responding to environmental triggers such as earthquakes, floods, impacts, and the differential loading associated with dune topography. During the last decade, a new wave of research is focusing on the event significance of deformation features in more detail, revealing a broad diversity of large-scale deformation morphologies. This research has led to a better appreciation of subsurface dynamics in the early Jurassic deformation events recorded in the Navajo Sandstone, including the important role of intrastratal sediment flow. This report documents two illustrative examples of large-scale sediment displacements represented in extensive outcrops of the Navajo Sandstone along the Utah/Arizona border. Architectural relationships in these outcrops provide definitive constraints that enable the recognition of a large-scale sediment outflow, at one location, and an equally large-scale subsurface flow at the other. At both sites, evidence for associated processes of liquefaction appear at depths of at least 40 m below the original depositional surface, which is nearly an order of magnitude greater than has commonly been reported from modern settings. The surficial, mass flow feature displays attributes that are consistent with much smaller-scale sediment eruptions (sand volcanoes) that are often documented from modern earthquake zones, including the development of hydraulic pressure from localized, subsurface liquefaction and the subsequent escape of fluidized sand toward the unconfined conditions of the surface. The origin of the forces that produced the lateral, subsurface movement of a large body of sand at the other site is not readily apparent. The various constraints on modeling the generation of the lateral force required to produce the observed displacement are considered here, along with photodocumentation of key outcrop relationships.

Exceptional marine sand bodies in the Paleozoic of Oklahoma

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

Fritz, R.D.; Kuykendall, M.D.; Hooker, E.O.

Of the wide variety of sandstone reservoirs in Oklahoma, the most unusual types of sand bodies are present in the Atokan Spiro Sandstone, Devonian Misener Sandstone, and Morrowan lower Morrow Sandstone. The common factors are that upon correlation and mapping these units are channel-like (fluvial-deltaic) in geometry, but from petrographic evidence are quartz-rich shallow-marine units, with the exclusion of intraclastic and diagenetic constituents. Stratigraphic mapping of the Spiro Sandstone of the Arkoma basin indicates two types of sand bodies: channel and sheet. The marine channel-like deposits, 10-150 ft thick, probably were deposited on a paleosurface produced by a pre-Atokan unconformity.more » Examination of cores and outcrop indicate that both the channel and sheet Spiro sands contain shallow-marine fossils, limestones, peloidal chamosite, burrows, and bioturbation, all indicative of a shallow-marine setting. The Misener Sandstone of north-central Oklahoma ranges from 10 to 100 ft thick with sharp boundaries. It was deposited in pre-Frisco/Woodford eroded paleochannels. Core evidence for shallow-marine deposition is glauconite, phosphatic fossils and clasts, burrows, and bioturbation. These were probably deposited in an embayed, estuary-like environment. The lower Morrow Sandstone of the Anadarko basin is similar in geometry, except that the sand bodies are multistoried and multilateral and do not appear to be associated with a regional unconformity. The lower Morrow sandstones, usually 30-60 ft thick. commonly are elongated and deposited parallel to the shoreline. Deposition is inferred to be shallow-marine from marine fossils and glauconite.« less

Microstructural and petrophysical characterization of a "structurally oversimplified" fault zone in poorly lithified sands: evidence for a coseismic rupture?

NASA Astrophysics Data System (ADS)

Balsamo, Fabrizio; Storti, Fabrizio

2010-05-01

We studied an extensional fault zone developed in poorly lithified, quartz-rich high porosity sandy sediments of the seismically active Crotone basin (southern Italy). The fault zone cuts across interlayered fine- to coarse-grained sands and consists of a cm-thick, discrete fault core embedded in virtually undeformed wall sediments. Consequently, it can be described as "structurally oversimplified" due to the lack of footwall and hanging wall damage zones. We acquired microstructural, grain size, grain shape, porosity, mineralogical and permeability data to investigate the influence of initial sedimentological characteristics of sands on the final faulted granular products and related hydrologic properties. Faulting evolves by a general grain size and porosity reduction with a combination of intragranular fracturing, spalling, and flaking of grain edges, irrespective of grain mineralogy. The dominance of cataclasis, also confirmed by fractal dimensions >2.6, is generally not expected at a deformation depth <1 km. Coarse-grained sand shows a much higher comminution intensity, grain shape variations and permeability drop than fine-grained sands. This is because coarser aggregates have (i) fewer grain-to-grain contacts for a given area, which results in higher stress concentration at contact points, and (ii) a higher probability of pre-existing intragranular microstructural defects that result in a lower grain strength. The peculiar structural architecture, the dominance of cataclasis over non-destructive particulate flow, and the compositional variations of clay minerals in the fault core, strongly suggest that the studied fault zone developed by a coseismic rupture.

Terrestrial analogs of the hellespontus dunes, Mars

USGS Publications Warehouse

Breed, C.S.

1977-01-01

Geomorphic features in the Hellespontus region, Mars, were compared with dunes of the crescentic ridge type in numerous terrestrial sand seas quantitatively by dimensional analysis of dune lengths, widths, and wavelengths. Mean values for the Hellespontus dunes are close to mean values derived from measurements of all sampled terrestrial sand seas. Terrestrial analogs of form and areal distribution of the Hellespontus dunes are shown by comparison of scale ratios derived from the measurements. Dunes of similar form occur in South West Africa, in Pakistan, in the southeastern Arabian peninsula, in the Sahara, in eastern USSR and northern China, and in western North America. Terrestrial analogs closest to form and areal distribution of the Hellespontus dunes are in the Kara Kum Desert, Turkmen SSR, and in the Ala Shan (Gobi) Desert, China. ?? 1977.

Spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region (Alberta, Canada)

NASA Astrophysics Data System (ADS)

Cooke, Colin A.; Kirk, Jane L.; Muir, Derek C. G.; Wiklund, Johan A.; Wang, Xiaowa; Gleason, Amber; Evans, Marlene S.

2017-12-01

The mining and processing of the Athabasca oil sands (Alberta, Canada) has been occurring for decades; however, a lack of consistent regional monitoring has obscured the long-term environmental impact. Here, we present sediment core results to reconstruct spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region. Early mining operations (during the 1970s and 1980s) led to elevated V and Pb inputs to lakes located <50 km from mining operations. Subsequent improvements to mining and upgrading technologies since the 1980s have reduced V and Pb loading to near background levels at many sites. In contrast, Hg deposition increased by a factor of ~3 to all 20 lakes over the 20th century, reflecting global-scale patterns in atmospheric Hg emissions. Base cation deposition (from fugitive dust emissions) has not measurably impacted regional lake sediments. Instead, results from a principal components analysis suggest that the presence of carbonate bedrock underlying lakes located close to development appears to exert a first-order control over lake sediment base cation concentrations and overall lake sediment geochemical composition. Trace element concentrations generally did not exceed Canadian sediment quality guidelines, and no spatial or temporal trends were observed in the frequency of guideline exceedence. Our results demonstrate that early mining efforts had an even greater impact on trace element cycling than has been appreciated previously, placing recent monitoring efforts in a critical long-term context.

Identification of hydraulic conductivity structure in sand and gravel aquifers: Cape Cod data set

USGS Publications Warehouse

Eggleston, J.R.; Rojstaczer, S.A.; Peirce, J.J.

1996-01-01

This study evaluates commonly used geostatistical methods to assess reproduction of hydraulic conductivity (K) structure and sensitivity under limiting amounts of data. Extensive conductivity measurements from the Cape Cod sand and gravel aquifer are used to evaluate two geostatistical estimation methods, conditional mean as an estimate and ordinary kriging, and two stochastic simulation methods, simulated annealing and sequential Gaussian simulation. Our results indicate that for relatively homogeneous sand and gravel aquifers such as the Cape Cod aquifer, neither estimation methods nor stochastic simulation methods give highly accurate point predictions of hydraulic conductivity despite the high density of collected data. Although the stochastic simulation methods yielded higher errors than the estimation methods, the stochastic simulation methods yielded better reproduction of the measured In (K) distribution and better reproduction of local contrasts in In (K). The inability of kriging to reproduce high In (K) values, as reaffirmed by this study, provides a strong instigation for choosing stochastic simulation methods to generate conductivity fields when performing fine-scale contaminant transport modeling. Results also indicate that estimation error is relatively insensitive to the number of hydraulic conductivity measurements so long as more than a threshold number of data are used to condition the realizations. This threshold occurs for the Cape Cod site when there are approximately three conductivity measurements per integral volume. The lack of improvement with additional data suggests that although fine-scale hydraulic conductivity structure is evident in the variogram, it is not accurately reproduced by geostatistical estimation methods. If the Cape Cod aquifer spatial conductivity characteristics are indicative of other sand and gravel deposits, then the results on predictive error versus data collection obtained here have significant practical consequences for site characterization. Heavily sampled sand and gravel aquifers, such as Cape Cod and Borden, may have large amounts of redundant data, while in more common real world settings, our results suggest that denser data collection will likely improve understanding of permeability structure.

Validation of the Korean version of the pediatric quality of life inventory 4.0 (PedsQL) generic core scales in school children and adolescents using the Rasch model.

PubMed

Kook, Seung Hee; Varni, James W

2008-06-02

The Pediatric Quality of Life Inventory (PedsQL) is a child self-report and parent proxy-report instrument designed to assess health-related quality of life (HRQOL) in healthy and ill children and adolescents. It has been translated into over 70 international languages and proposed as a valid and reliable pediatric HRQOL measure. This study aimed to assess the psychometric properties of the Korean translation of the PedsQL 4.0 Generic Core Scales. Following the guidelines for linguistic validation, the original US English scales were translated into Korean and cognitive interviews were administered. The field testing responses of 1425 school children and adolescents and 1431 parents to the Korean version of PedsQL 4.0 Generic Core Scales were analyzed utilizing confirmatory factor analysis and the Rasch model. Consistent with studies using the US English instrument and other translation studies, score distributions were skewed toward higher HRQOL in a predominantly healthy population. Confirmatory factor analysis supported a four-factor and a second order-factor model. The analysis using the Rasch model showed that person reliabilities are low, item reliabilities are high, and the majority of items fit the model's expectation. The Rasch rating scale diagnostics showed that PedsQL 4.0 Generic Core Scales in general have the optimal number of response categories, but category 4 (almost always a problem) is somewhat problematic for the healthy school sample. The agreements between child self-report and parent proxy-report were moderate. The results demonstrate the feasibility, validity, item reliability, item fit, and agreement between child self-report and parent proxy-report of the Korean version of PedsQL 4.0 Generic Core Scales for school population health research in Korea. However, the utilization of the Korean version of the PedsQL 4.0 Generic Core Scales for healthy school populations needs to consider low person reliability, ceiling effects and cultural differences, and further validation studies on Korean clinical samples are required.

Lateral fluid flow in a compacting sand-shale sequence: South Caspian basin.

USGS Publications Warehouse

Bredehoeft, J.D.; Djevanshir, R.D.; Belitz, K.R.

1988-01-01

The South Caspian basin contains both sands and shales that have pore-fluid pressures substantially in excess of hydrostatic fluid pressure. Pore-pressure data from the South Caspian basin demonstrate that large differences in excess hydraulic head exist between sand and shale. The data indicate that sands are acting as drains for overlying and underlying compacting shales and that fluid flows laterally through the sand on a regional scale from the basin interior northward to points of discharge. The major driving force for the fluid movement is shale compaction. We present a first- order mathematical analysis in an effort to test if the permeability of the sands required to support a regional flow system is reasonable. The results of the analysis suggest regional sand permeabilities ranging from 1 to 30 md; a range that seems reasonable. This result supports the thesis that lateral fluid flow is occurring on a regional scale within the South Caspian basin. If vertical conduits for flow exist within the basin, they are sufficiently impermeable and do not provide a major outlet for the regional flow system. The lateral fluid flow within the sands implies that the stratigraphic sequence is divided into horizontal units that are hydraulically isolated from one another, a conclusion that has important implications for oil and gas migration.-Authors

Holocene Climate Change in Sub-Alpine Southwestern Alberta: Evidence from Oxygen and Carbon Isotope values of Hogarth Lake Marl.

NASA Astrophysics Data System (ADS)

Matkowski, D.; Patterson, W. P.; Timsic, S.

2017-12-01

A 3.6-meter lake sediment core was recovered from Upper Hogarth Lake, providing proxy evidence for climate variability over the last 11,500 years. The core was sampled at millimeter scale for high-resolution oxygen and carbon isotope values. Large variations (up to 6‰) in the carbon isotope values are attributed to the increasingly dominant role of terrestrial-sourced organic matter over bedrock-sourced DIC during initial lake formation and subsequent changes in regional humidity. Variations (up to 4‰) in oxygen isotope values of the marl are interpreted as representing changes in meteoric water source and regional temperature. The hydrologically-open, fresh-water lake is hosted in Devonian-Carboniferous carbonates, recharged via groundwater, surface flow and precipitation. Marl sediment is generated by the green algae Chara sp., with marl deposition beginning approximately 11,500 cal yBP. Our age model was constructed using tephrochronology and radiocarbon dating of 8 terrestrial plant samples, then calibrated using the University of Minnesota's "Bacon" software. The presence of an ash layer in the core was associated with the Mazama ash layer dated 7,627 ±150 yBP, and was used to support the 14C age model. Sediment deposition is characterized by 3 stages: from the recent, dating back to 11,500 cal yBP, the core is marl dominated, comprising 70% of the 3.6m core. Prior to marl deposition there is a 500-year depositional period of carbonate and allochthonous clastic material. Below 2.65 meters, the sediment consists of fine sand and mud; sourced from the weathering of surrounding bedrock. Isotope data are characterized by 5 distinct periods. 7,800 cal yBP to the end Younger Dryas ( 11,500 cal yBP) exhibits irregular, and generally decreasing, δ13C and δ18O values, with a positive excursion in δ18O values occurring around 9,000 cal yBP. Climate was stable, cool and dry from 5,000-7,000 cal yBP, evidenced by relatively invariant δ13C and δ18O values. The period from 3,000-5,000 cal yBP exhibits decreasing δ13C values and increasing δ18O values, suggesting regional climate warming, possibly accompanied by an increase in humidity. From 3,000 cal yBP to the present, δ13C and δ18O values coincidently decrease, suggesting an increase in regional humidity along with a general cooling trend.

High-resolution seismic reflection to delineate shallow gas in Eastern Kansas

USGS Publications Warehouse

Miller, R.D.; Watney, W.L.; Begay, D.K.; Xia, J.

2000-01-01

Unique amplitude characteristics of shallow gas sands within Pennsylvanian clastic-carbonate dominated sequences are discernible on high-resolution seismic reflection data in eastern Kansas. Upward grading sequences of sand into shale represent a potential gas reservoir with a low-impedence acoustic contrast at the base of the encasing layer. The gas sand and encasing shale, which define the gas reservoir studied here, are part of an erosional incised valley where about 30 m of carbonates and shale have been replaced by sandstone and shale confined to the incised valley. These consolidated geologic settings would normally possess high impedence gas sand reservoirs as defined by abrupt contacts between the gas sand and encasing shale. Based orr core and borehole logs, the gas sand studied here grades from sand into shale in a fashion analogous to that observed in classic low-impedance environments. Amplitude and phase characteristics of high-resolution seismic data across this approximately 400-m wide gas sand are indicative of a low-impedance reservoir. Shot gathers possess classic amplitude with offsett-dependent characteristics which are manifeted on the stacked section as "bright spots." Dominant Frequencies of around 120 Hz allow detection of several reflectors within the 30+ meters of sand/shale that make up this localized gas-rich incised valley fill. The gradational nature of the trapping mechanism observed in this gas reservoir would make detection with conventional seismic reflection methods unlikely.

Vector soup: high-throughput identification of Neotropical phlebotomine sand flies using metabarcoding.

PubMed

Kocher, Arthur; Gantier, Jean-Charles; Gaborit, Pascal; Zinger, Lucie; Holota, Helene; Valiere, Sophie; Dusfour, Isabelle; Girod, Romain; Bañuls, Anne-Laure; Murienne, Jerome

2017-03-01

Phlebotomine sand flies are haematophagous dipterans of primary medical importance. They represent the only proven vectors of leishmaniasis worldwide and are involved in the transmission of various other pathogens. Studying the ecology of sand flies is crucial to understand the epidemiology of leishmaniasis and further control this disease. A major limitation in this regard is that traditional morphological-based methods for sand fly species identifications are time-consuming and require taxonomic expertise. DNA metabarcoding holds great promise in overcoming this issue by allowing the identification of multiple species from a single bulk sample. Here, we assessed the reliability of a short insect metabarcode located in the mitochondrial 16S rRNA for the identification of Neotropical sand flies, and constructed a reference database for 40 species found in French Guiana. Then, we conducted a metabarcoding experiment on sand flies mixtures of known content and showed that the method allows an accurate identification of specimens in pools. Finally, we applied metabarcoding to field samples caught in a 1-ha forest plot in French Guiana. Besides providing reliable molecular data for species-level assignations of phlebotomine sand flies, our study proves the efficiency of metabarcoding based on the mitochondrial 16S rRNA for studying sand fly diversity from bulk samples. The application of this high-throughput identification procedure to field samples can provide great opportunities for vector monitoring and eco-epidemiological studies. © 2016 John Wiley & Sons Ltd.

Experimental Simulations of Methane Gas Migration through Water-Saturated Sediment Cores

NASA Astrophysics Data System (ADS)

Choi, J.; Seol, Y.; Rosenbaum, E. J.

2010-12-01

Previous numerical simulations (Jaines and Juanes, 2009) showed that modes of gas migration would mainly be determined by grain size; capillary invasion preferably occurring in coarse-grained sediments vs. fracturing dominantly in fine-grained sediments. This study was intended to experimentally simulate preferential modes of gas migration in various water-saturated sediment cores. The cores compacted in the laboratory include a silica sand core (mean size of 180 μm), a silica silt core (1.7 μm), and a kaolin clay core (1.0 μm). Methane gas was injected into the core placed within an x-ray-transparent pressure vessel, which was under continuous x-ray computed tomography (CT) scanning with controlled radial (σr), axial (σa), and pore pressures (P). The CT image analysis reveals that, under the radial effective stress (σr') of 0.69 MPa and the axial effective stress (σa') of 1.31 MPa, fracturings by methane gas injection occur in both silt and clay cores. Fracturing initiates at the capillary pressure (Pc) of ~ 0.41 MPa and ~ 2.41 MPa for silt and clay cores, respectively. Fracturing appears as irregular fracture-networks consisting of nearly invisibly-fine multiple fractures, longitudinally-oriented round tube-shape conduits, or fine fractures branching off from the large conduits. However, for the sand core, only capillary invasion was observed at or above 0.034 MPa of capillary pressure under the confining pressure condition of σr' = 1.38 MPa and σa' = 2.62 MPa. Compared to the numerical predictions under similar confining pressure conditions, fracturing occurs with relatively larger grain sizes, which may result from lower grain-contact compression and friction caused by loose compaction and flexible lateral boundary employed in the experiment.

Quartz Knapping Strategies in the Howiesons Poort at Sibudu (KwaZulu-Natal, South Africa)

PubMed Central

de la Peña, Paloma; Wadley, Lyn

2014-01-01

The variability associated with Sibudu's Howiesons Poort Industry highlights the unpredictable trajectory of technology in the Middle Stone Age. We reach this conclusion through a study of the technology on quartz from one of the Howiesons Poort layers (Grey Sand) from Sibudu rock shelter. Quartz bifacial technology has previously been described at the site, but this new in-depth study of the quartz technology reveals other strategies. First is the recurring employment of bipolar knapping, formerly considered as a defining feature of the Later Stone Age. Secondly, we highlight a laminar technology with emphasis on small quartz bladelets. Bipolar cores are most common, followed by prismatic cores. The knapping strategies in Grey Sand seem to involve systematic recycling and the deliberate production of microliths. PMID:25014352

Micro X-ray CT Imaging of Sediments under Confining Pressure

NASA Astrophysics Data System (ADS)

Schindler, M.; Prasad, M.

2016-12-01

We developed a pressure and temperature control system for use inside the micro X-ray CT scanner Xradia 400. We succeeded in building a pressure vessel that can be pressurized to 34.5 MPa (5000 psi) while being transparent to X-rays. The setup can currently be cooled to -5°C and heated to 40°C. We were able to observe grain damage and porosity reduction due to applied confining pressure in clean quartz sand samples and quartz sand and bentonite samples. By comparing micro CT images at atmospheric pressure and 13.8 MPa (2000 psi) confining pressure, we observed compaction of the samples resulting in grain damage and fracturing of sediment grains (Figure 1). When the confining pressure was decreased some grains experienced further fracturing. The grain damage appears irreversible. Further fracturing of grains in pre-compacted sediment was observed upon repeated confining pressure cycling. We are currently working on feed-throughs for fluid lines and electric wiring to use ultrasonic transducers and pressure control in combination. Further we plan to include pore pressure in addition to confining pressure into the system. The pressure control system in combination with ultrasonic transducers will allow us to visually observe pore scale changes in rock samples while simultaneously identifying their influence on ultrasonic velocities. Such pore-scale changes are usually not taken into account by rock physics models and could help to identify why laboratory data diverges from theoretical models. Further, it is possible to compute compressibility from mCT images at different stress states by image correlation

Development of a solar receiver for an organic rankine cycle engine

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

Haskins, H.J.; Taylor, R.M.; Osborn, D.B.

A solar receiver is described for use with an organic Rankine cycle (ORC) engine as part of the Small Community Solar Thermal Power Experiment (SCSE). The selected receiver concept is a direct-heated, once-through, monotube boiler normally operating at supercritical pressure. Fabrication methods for the receiver core have been developed and validated with flat braze samples, cylindrical segment samples, and a complete full-scale core assembly.

Sedimentological and Micropaleontological Characteristics of the 2015 Hurricane Joaquin Deposit and their Implications for Long-Term Records of Storms and Tsunamis Impacting the Caribbean

NASA Astrophysics Data System (ADS)

Kosciuch, T. J.; Pilarczyk, J.; Reinhardt, E. G.; Mauviel, A.; Aucoin, C. D.

2017-12-01

The uncertainty of extreme wave events in the Caribbean was highlighted in October 2015 when Hurricane Joaquin tracked through, or near, several islands (e.g., Bahamas, Haiti, Turks and Caicos) as a Category 4 storm. The short observational record of landfalling hurricanes is insufficient in preparing many of these islands for such a rare, intense storm. Examining the sediments deposited by recent landfalling hurricanes assists the understanding of the long-term spatial and temporal variations in storm frequency and intensity. However, the interpretation of prehistoric hurricane deposits in the Caribbean is complicated by the possibility of tsunami deposits (e.g., Puerto Rico Trench, 1755 Lisbon Tsunami), which are similar in composition and difficult to differentiate from storm sediments. To circumvent this problem, we describe the microfossil and sedimentary characteristics of a modern storm analogue, the Hurricane Joaquin deposit, from San Salvador Island in the Bahamas and use it as a basis for interpreting a series of 10 anomalous sand deposits found in a coastal pond. San Salvador is a small (160 km2) island in the Bahamas with a history of landfalling hurricanes and tsunamis. On 4 October 2015, Hurricane Joaquin came within 7 km of San Salvador, inundating most of its coastline and depositing two distinct layers: a sand layer and a boulder layer. The sand layer was 12 to 104 cm thick, extended 135 m inland, and consisted of fine to medium sand. The sand layer contained high abundances of foraminifera, including Homotrema rubra, a foraminifer that lives on the reef and is detached by large waves. The presence of well-preserved fragments of Homotrema within the Joaquin deposit suggests transport from the reef and rapid burial. The boulder layer included large clasts (30 to 200 cm in length) that were imbricated perpendicular to the shoreline and extended 135 m inland. The boulder layer was more laterally extensive (1020 m) than the sand layer (110 m). The anomalous sand layers in the coastal pond cores shared many similarities with the Joaquin sand layer; they sharply overlie organic-rich sediment and contain abundant well-preserved Homotrema fragments. Further foraminiferal analysis on the older sand layers in the cores will aid in determining the relative intensity of hurricanes that have impacted San Salvador.

Above vs. belowground plant biomass along a barrier island: Implications for dune stabilization.

PubMed

Charbonneau, Bianca R; Wnek, John P; Langley, J Adam; Lee, Gina; Balsamo, Ronald A

2016-11-01

Coastal regions are inherently and increasingly vulnerable and geomorphologically unstable, yet are invaluable economic and residential hubs. Dunes are dynamic buffers to erosion and the most natural, economical, and effective defense for coastal communities. Vegetation is integral to dune structure as it facilitates accretion and stabilization. Differences in the vegetation and root density likely translate to variability in coastal erosion prevention, but this notion has been largely unconsidered. We directly compared stabilizing factors, depth and density, of the root systems of two dominant mid-Atlantic dune plant species, native American beach grass (Ammophila breviligulata) and invasive Asiatic sand sedge (Carex kobomugi). Despite high plant density, C. kobomugi is targeted for removal in restoration efforts as its roots are assumed to provide less effective stabilization than A. breviligulata. We collected 30 cores and hand dug 14 A. breviligulata ramets at Island Beach State Park, New Jersey to examine biomass, root:shoot ratios, and root density. C. kobomugi had a more extensive root system with a root:shoot ratio of 11.36:1 compared to 1.62:1 for A. breviligulata. Similarly, cores 60 cm deep and 7.6 cm wide were sufficient to attain fully intact A. breviligulata roots, which did not extend deeper than 40 cm, but insufficient for C. kobomugi roots which extended beyond the sampling system vertically and horizontally. Scaling these findings to m(-2), aboveground biomass is relatively equal, but C. kobomugi had over 700% more root mass m(-2) than A. breviligulata. These results have strong implications for dune management. The root system of C. kobomugi may be better adapted to stabilize dunes and thus protect coastal areas during small and large-scale perturbations than previously supposed. This is a unique situation whereby the creation of monocultures will hyperstabilize dunes and make them more resistant to erosion at the cost of reduced biodiversity within the framework of resiliency. Published by Elsevier Ltd.

Holocene ruptures along the North Anatolia Fault in the Marmara Sea, Turkey: Sedimentary processes, spatial extent and age

NASA Astrophysics Data System (ADS)

Braudy, N.; McHugh, C. M.; Cagatay, M.; Seeber, L.; Henry, P.; Geli, L.

2010-12-01

The North Anatolian fault (NAF), which extends east west for over 1600 km across Turkey, is one of the world's major continental transforms. Since 1939, a sequence of M>7 earthquakes ruptured progressively westward the entire NAF east of Marmara. The most recent and westernmost events in this sequence, the Mw7.4 Izmit and the Mw7.2 Duzce main shocks of 1999, ruptured about 160 km of the fault and were particularly destructive (~17,000 deaths). The only portion of the NAF that did not rupture in the last century is the segment beneath the Marmara Sea that is considered a seismic gap and presents high risk to Istanbul and surroundings. To decipher Holocene earthquake ruptures and the processes leading to their signature in the sedimentary record we applied submarine paleoseismology techniques to study a transect of three 10 m long cores recovered from the Central Basin. The sediments were analyzed with x-ray radiography, for grain size variability at cm-scale, geochemical elements at mm-scale and physical properties. These measurements were calibrated to a chronology developed from short-lived radioisotopes (137-Cs, 210-Pb) and radiocarbon. Turbidites were sampled from the deepest part of the Central Basin, from 1248 to 1262 m depth. As previously documented by McHugh et al (2006), these turbidites are characterized by multiple sand and coarse silt beds, each normally graded, and that together grade upwards into a non-stratified silt that also fines upwards. Elemental concentrations of Al and Si increase with the sand and coarser silt components indicative of an influx of terrigenous components. These complex turbidites-homogenites are as thick as 1 m and dominate the sedimentation in the basin (≈80%). The remainder includes 10 to 20 cm thick fining upwards silt deposits. We interpret these depositional events to represent large earthquakes, the ones including transport of sand are proximal, and the ones without the sand are distal. We measured concentrations of Ca within the coarse component of the complex turbidite and depletion of Mn above. These elemental trends, previously documented by Cagatay et al (2008) can generally be associated with the turbidite-homogenite units and are linked to diagnetic processes resulting from diffuse fluid/gas escape during strong shaking of the sea floor or after the earthquake. Fifteen turbidites-homogenites were preserved within the past 4000 years with an average recurrence interval of 300 years. This is consistent with previous estimates and with a constant slip rate for the NAF for the mid to late Holocene. We have tentatively linked one of the turbidite-homogenite deposits to the 740 AD historical earthquake and two others to possibly the 1912 > Ms 7.4 and more distal 1963 or 1964 events Ms >6.4 linked to the Yalova and Manyas faults, respectively.

Investigation of vertical distribution and morphology of indigenous organic matter Sleeping Bear site, Michigan

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

West, C.C.; Lyon, W.G.; Ross, D.L.

1994-11-01

This study evaluates the nature and origin of particulate organic carbon and organic coatings on aquifer sands upgradient from a fuel spill site near the Sleeping Bear Dunes National Lakeshore in Michigan. The distribution of carbon was found to be highly complex due to the occurrence of high organic carbon horizons, bounded above and below by high carbonate sediments. The organic coatings on the sands were examined using white light and fluorescence microscopy and by scanning electron microscopy. Core samples were analyzed for organic and inorganic carbon, solution pH, humic/fulvic acid ratios, and insoluable organic matter content (that is, humin)more » as function of depth from the ground surface. The organic geochemistry of the soil profile at this site was found to be significantly influenced by the carbonates producing a sharp boundary of precipitated organic matter. This boundary was followed by coatings of predominantly fulvic acid salts on mineral grains deeper in the soil column. The coatings extended into the aquifer. The existence of native organic films on sand grains is well documented in the soils literature. The study reported here was greatly aided by this information and provides the framework for future studies concerning the influence of carbon distribution, chemical identity, and morphology on contaminant fate and transport processes. 56 refs., 9 figs., 2 tabs.« less

Spatial and Temporal Variation in Enterococcal Abundance and Its Relationship to the Microbial Community in Hawaii Beach Sand and Water

PubMed Central

Cui, Henglin; Yang, Kun; Pagaling, Eulyn

2013-01-01

Recent studies have reported high levels of fecal indicator enterococci in marine beach sand. This study aimed to determine the spatial and temporal variation of enterococcal abundance and to evaluate its relationships with microbial community parameters in Hawaii beach sand and water. Sampling at 23 beaches on the Island of Oahu detected higher levels of enterococci in beach foreshore sand than in beach water on a mass unit basis. Subsequent 8-week consecutive samplings at two selected beaches (Waialae and Kualoa) consistently detected significantly higher levels of enterococci in backshore sand than in foreshore/nearshore sand and beach water. Comparison between the abundance of enterococci and the microbial communities showed that enterococci correlated significantly with total Vibrio in all beach zones but less significantly with total bacterial density and Escherichia coli. Samples from the different zones of Waialae beach were sequenced by 16S rRNA gene pyrosequencing to determine the microbial community structure and diversity. The backshore sand had a significantly more diverse community and contained different major bacterial populations than the other beach zones, which corresponded to the spatial distribution pattern of enterococcal abundance. Taken together, multiple lines of evidence support the possibility of enterococci as autochthonous members of the microbial community in Hawaii beach sand. PMID:23563940

Joint Measurements Of Acoustic And Mechanical Properties For Methane Hydrate-Bearing Unconsolidated Sediments Synthesized In Laboratory

NASA Astrophysics Data System (ADS)

Yang, Z.; He, T.

2017-12-01

To more accurately explain geophysical exploration data of natural gas hydrate reservoir and to better assess the formation stability for geological or engineering hazards, it is important to comprehensively understand the geophysical and mechanical properties of hydrate-bearing unconsolidated marine sediments, which are significantly different from sea-water saturated ones. Compared to hard-to-control in-situ measurement, laboratory methods are important and feasible to investigate the parameter effects. With the new designed experimental apparatus, we measured ultrasonic velocity, resistivity and stress-strain relation of methane hydrate-bearing unconsolidated sediments. The experimental mineral mixture is prepared as the composition of sample HY-3 of core SH-7 from Shenhu area, South China Sea. It composed of 0.4 wt. % kaolinite, 23.5 wt. % silt (4 - 63 μm), 32.1 wt. % fine sand (63 - 250 μm), 29.2 wt. % medium sand (250 - 500 μm) and 14.8 wt. % coarse sand (500 - 2000 μm). The pure methane enters into the brine (NaCl salinity of 3.5%) saturated sample all around to synthesis methane hydrate. The methane hydrate saturation was calculated by methane consumption amount, which was in turn calculated by gas state equation using the measured methane pressure drop in high pressure reactor. The ultrasonic velocities and resistivity were measured frequently during methane hydrate saturation increasing to examine the velocity varying pattern, especially for S-wave velocities, which may reflect different hydrate occurrence states in sediment pores: load-bearing or not. The stress - strain curves of methane hydrate - bearing sediments showed typical elastic - plastic characteristics and were used to obtain Young's modulus, Poisson's ratio, failure strength and other mechanical parameters. With these results, we can know better about the hydrate reservoir at Shenhu area.

Epibenthic communities of sedimentary habitats in a NE Atlantic deep seamount (Galicia Bank)

NASA Astrophysics Data System (ADS)

Serrano, A.; Cartes, J. E.; Papiol, V.; Punzón, A.; García-Alegre, A.; Arronte, J. C.; Ríos, P.; Lourido, A.; Frutos, I.; Blanco, M.

2017-12-01

Galicia Bank is a deep seamount included as Site of Community Importance (SCI) in the Spanish Natura 2000 Network proposal. In the present study, epibenthic assemblages of sedimentary habitats have been described, together with the main environmental factor explaining species and communities distribution. Five epibenthic assemblages have been identified. Depth was the main factor explaining assemblage distribution, and the role of sediment type, water masses, and coral framework presence is also discussed. Three assemblages are located in the summit: the shallowest one (730-770 m), in the boundary between Eastern North Atlantic Central Water (ENACW) and Mediterranean Overflow Water (MOW) water masses is typified by ophiuroids and characterized by medium sands. The second assemblage (770-800 m) typified by the bivalve Limopsis minuta and the solitary coral Flabellum chunii correspond with medium sands and MOW core; and the third typified by the presence of cold-water coral communities dominated by Lophelia pertusa and Madrepora oculata, also on the MOW influence. In the border of the summit, in the bank break, an assemblage located in the range 1000-1200 m is dominated by the urchin Cidaris cidaris and the sponge Thenea muricata. In the flat flanks around the bank, the deepest assemblage (1400-1800 m) is dominated by the holothurian Benthogone rosea, in a depth range dominated by the Labrador water (LSW) and in fine sands with highest contents of organic matter. Most of species appeared in a depth range smaller than 25% of total depth range sampled and in < 10% of samples. Differential preference of species is evident in the different trophic guilds, with a higher dominance of filter-feeders in the summit and of deposit-feeders in the deepest assemblage, and have clear links with nutrient dynamics in the bank.

Compositional Signatures in Acoustic Backscatter Over Vegetated and Unvegetated Mixed Sand-Gravel Riverbeds

NASA Astrophysics Data System (ADS)

Buscombe, D.; Grams, P. E.; Kaplinski, M. A.

2017-10-01

Multibeam acoustic backscatter has considerable utility for remote characterization of spatially heterogeneous bed sediment composition over vegetated and unvegetated riverbeds of mixed sand and gravel. However, the use of high-frequency, decimeter-resolution acoustic backscatter for sediment classification in shallow water is hampered by significant topographic contamination of the signal. In mixed sand-gravel riverbeds, changes in the abiotic composition of sediment (such as homogeneous sand to homogeneous gravel) tend to occur over larger spatial scales than is characteristic of small-scale bedform topography (ripples, dunes, and bars) or biota (such as vascular plants and periphyton). A two-stage method is proposed to filter out the morphological contributions to acoustic backscatter. First, the residual supragrain-scale topographic effects in acoustic backscatter with small instantaneous insonified areas, caused by ambiguity in the local (beam-to-beam) bed-sonar geometry, are removed. Then, coherent scales between high-resolution topography and backscatter are identified using cospectra, which are used to design a frequency domain filter that decomposes backscatter into the (unwanted) high-pass component associated with bedform topography (ripples, dunes, and sand waves) and vegetation, and the (desired) low-frequency component associated with the composition of sediment patches superimposed on the topography. This process strengthens relationships between backscatter and sediment composition. A probabilistic framework is presented for classifying vegetated and unvegetated substrates based on acoustic backscatter at decimeter resolution. This capability is demonstrated using data collected from diverse settings within a 386 km reach of a canyon river whose bed varies among sand, gravel, cobbles, boulders, and submerged vegetation.

Compositional signatures in acoustic backscatter over vegetated and unvegetated mixed sand-gravel riverbeds

USGS Publications Warehouse

Buscombe, Daniel; Grams, Paul E.; Kaplinski, Matt A.

2017-01-01

Multibeam acoustic backscatter has considerable utility for remote characterization of spatially heterogeneous bed sediment composition over vegetated and unvegetated riverbeds of mixed sand and gravel. However, the use of high-frequency, decimeter-resolution acoustic backscatter for sediment classification in shallow water is hampered by significant topographic contamination of the signal. In mixed sand-gravel riverbeds, changes in the abiotic composition of sediment (such as homogeneous sand to homogeneous gravel) tend to occur over larger spatial scales than is characteristic of small-scale bedform topography (ripples, dunes, and bars) or biota (such as vascular plants and periphyton). A two-stage method is proposed to filter out the morphological contributions to acoustic backscatter. First, the residual supragrain-scale topographic effects in acoustic backscatter with small instantaneous insonified areas, caused by ambiguity in the local (beam-to-beam) bed-sonar geometry, are removed. Then, coherent scales between high-resolution topography and backscatter are identified using cospectra, which are used to design a frequency domain filter that decomposes backscatter into the (unwanted) high-pass component associated with bedform topography (ripples, dunes, and sand waves) and vegetation, and the (desired) low-frequency component associated with the composition of sediment patches superimposed on the topography. This process strengthens relationships between backscatter and sediment composition. A probabilistic framework is presented for classifying vegetated and unvegetated substrates based on acoustic backscatter at decimeter resolution. This capability is demonstrated using data collected from diverse settings within a 386 km reach of a canyon river whose bed varies among sand, gravel, cobbles, boulders, and submerged vegetation.

Understanding the core-halo relation of quantum wave dark matter from 3D simulations.

PubMed

Schive, Hsi-Yu; Liao, Ming-Hsuan; Woo, Tak-Pong; Wong, Shing-Kwong; Chiueh, Tzihong; Broadhurst, Tom; Hwang, W-Y Pauchy

2014-12-31

We examine the nonlinear structure of gravitationally collapsed objects that form in our simulations of wavelike cold dark matter, described by the Schrödinger-Poisson (SP) equation with a particle mass ∼10(-22)  eV. A distinct gravitationally self-bound solitonic core is found at the center of every halo, with a profile quite different from cores modeled in the warm or self-interacting dark matter scenarios. Furthermore, we show that each solitonic core is surrounded by an extended halo composed of large fluctuating dark matter granules which modulate the halo density on a scale comparable to the diameter of the solitonic core. The scaling symmetry of the SP equation and the uncertainty principle tightly relate the core mass to the halo specific energy, which, in the context of cosmological structure formation, leads to a simple scaling between core mass (Mc) and halo mass (Mh), Mc∝a(-1/2)Mh(1/3), where a is the cosmic scale factor. We verify this scaling relation by (i) examining the internal structure of a statistical sample of virialized halos that form in our 3D cosmological simulations and by (ii) merging multiple solitons to create individual virialized objects. Sufficient simulation resolution is achieved by adaptive mesh refinement and graphic processing units acceleration. From this scaling relation, present dwarf satellite galaxies are predicted to have kiloparsec-sized cores and a minimum mass of ∼10(8)M⊙, capable of solving the small-scale controversies in the cold dark matter model. Moreover, galaxies of 2×10(12)M⊙ at z=8 should have massive solitonic cores of ∼2×10(9)M⊙ within ∼60  pc. Such cores can provide a favorable local environment for funneling the gas that leads to the prompt formation of early stellar spheroids and quasars.

Core food of the French food supply: second Total Diet Study.

PubMed

Sirot, V; Volatier, J L; Calamassi-Tran, G; Dubuisson, C; Menard, C; Dufour, A; Leblanc, J C

2009-05-01

As first described in the 1980s, the core food intake model allows a precise assessment of dietary nutrient intake and dietary exposure to contaminants insofar as it reflects the eating habits of a target population and covers the most important foods in terms of consumption, selected nutrient and contaminant contribution. This model has been used to set up the sampling strategy of the second French Total Diet Study (TDS) with the aim of obtaining a realistic panorama of nutrient intakes and contaminant exposure for the whole population, useful for quantitative risk assessment. Data on consumption trends and eating habits from the second French individual food consumption survey (INCA2) as well as data from a 2004 purchase panel of French households (SECODIP) were used to identify the core foods to be sampled. A total of 116 core foods on a national scale and 70 core foods on a regional scale were selected according to (1) the consumption data for adults and children, (2) their consumer rates, and (3) their high contribution to exposure to one or more contaminants of interest. Foods were collected in eight French regions (36 cities) and prepared 'as consumed' to be analysed for their nutritional composition and contamination levels. A total of 20 280 different food products were purchased to make up the 1352 composite samples of core foods to be analysed for additives, environmental contaminants, pesticide residues, trace elements and minerals, mycotoxins and acrylamide. The establishment of such a sampling plan is essential for effective, high-quality monitoring of dietary exposure from a public health point of view.

Geometry of the Nojima fault at Nojima-Hirabayashi, Japan - II. Microstructures and their implications for permeability and strength

USGS Publications Warehouse

Moore, Diane E.; Lockner, D.A.; Ito, H.; Ikeda, R.; Tanaka, H.; Omura, K.

2009-01-01

Samples of damage-zone granodiorite and fault core from two drillholes into the active, strike-slip Nojima fault zone display microstructures and alteration features that explain their measured present-day strengths and permeabilities and provide insight on the evolution of these properties in the fault zone. The least deformed damage-zone rocks contain two sets of nearly perpendicular (60-90?? angles), roughly vertical fractures that are concentrated in quartz-rich areas, with one set typically dominating over the other. With increasing intensity of deformation, which corresponds generally to increasing proximity to the core, zones of heavily fragmented rock, termed microbreccia zones, develop between prominent fractures of both sets. Granodiorite adjoining intersecting microbreccia zones in the active fault strands has been repeatedly fractured and locally brecciated, accompanied by the generation of millimeter-scale voids that are partly filled with secondary minerals. Minor shear bands overprint some of the heavily deformed areas, and small-scale shear zones form from the pairing of closely spaced shear bands. Strength and permeability measurements were made on core collected from the fault within a year after a major (Kobe) earthquake. Measured strengths of the samples decrease regularly with increasing fracturing and fragmentation, such that the gouge of the fault core and completely brecciated samples from the damage zone are the weakest. Permeability increases with increasing disruption, generally reaching a peak in heavily fractured but still more or less cohesive rock at the scale of the laboratory samples. Complete loss of cohesion, as in the gouge or the interiors of large microbreccia zones, is accompanied by a reduction of permeability by 1-2 orders of magnitude below the peak values. The core samples show abundant evidence of hydrothermal alteration and mineral precipitation. Permeability is thus expected to decrease and strength to increase somewhat in active fault strands between earthquakes, as mineral deposits progressively seal fractures and fill pore spaces. ?? Birkh??user Verlag, Basel 2009.

Granulometric analysis at Lampulo Fishing Port (LFP) substrate, Banda Aceh, Indonesia

NASA Astrophysics Data System (ADS)

Purnawan, S.; Setiawan, I.; Haridhi, H. A.; Irham, M.

2018-01-01

The study of sediment granulometry was completed at Lampulo fishing port (LFP). The LFP is a main fishing port in Aceh Province, Indonesia, located at 5°34’35” N; 95°19’23” E. The purpose of the research is to study and construct the environment condition of the bottom substrate. The data was taken by incorporating coring method at 10 stations using purposive random sampling. The wet sieve method was used to analyze the grain size for geostatistical analysis. The geostatistical parameters analysis in this study is classified as mean, sorting, skewness and kurtosis. The result informs that the types of sediments are sand, sandy clay and clayey sand for all stations. Station 1, however, is found as the coarsest compares to the other stations. All of the sediment collected at each station displays moderately sorted to poor sorted, while kurtosis values may be categorized as very leptokurtic. The results of the sediment parameters indicate that the environment of harbor pool was in a stable state, related to a sheltered condition.

Pore space analysis of NAPL distribution in sand-clay media

USGS Publications Warehouse

Matmon, D.; Hayden, N.J.

2003-01-01

This paper introduces a conceptual model of clays and non-aqueous phase liquids (NAPLs) at the pore scale that has been developed from a mathematical unit cell model, and direct micromodel observation and measurement of clay-containing porous media. The mathematical model uses a unit cell concept with uniform spherical grains for simulating the sand in the sand-clay matrix (???10% clay). Micromodels made with glass slides and including different clay-containing porous media were used to investigate the two clays (kaolinite and montmorillonite) and NAPL distribution within the pore space. The results were used to understand the distribution of NAPL advancing into initially saturated sand and sand-clay media, and provided a detailed analysis of the pore-scale geometry, pore size distribution, NAPL entry pressures, and the effect of clay on this geometry. Interesting NAPL saturation profiles were observed as a result of the complexity of the pore space geometry with the different packing angles and the presence of clays. The unit cell approach has applications for enhancing the mechanistic understanding and conceptualization, both visually and mathematically, of pore-scale processes such as NAPL and clay distribution. ?? 2003 Elsevier Science Ltd. All rights reserved.

Environmental Support for High Frequency Acoustic Measurements at NOSC (Naval Ocean Systems Center) Oceanographic Tower, 26 April-7 May 1982. Part 1. Sediment Geoacoustic Properties

DTIC Science & Technology

1983-06-01

surrounding the tripod (cores 14, 15, 16) were moderately to moderately well-sorted, fine-skewed, platykurtic to mesokurtic coarse grained sands, The...side of the interface. mrt Sediments throughout the 18 cm length of core 7 were moderately sorted, very finely-skewed, platykurtic to mesokurtic

Inner Core Tomography Under Africa

NASA Astrophysics Data System (ADS)

Irving, J. C. E.

2014-12-01

Hemispherical structure in the inner core has been observed using both normal mode and body wave data, but the more regional scale properties of the inner core are still the subject of ongoing debate. The nature of the vertical boundary regions between the eastern and western hemispheres will be an important constraint on dynamical processes at work in the inner core. With limited data available, earlier inner core studies defined each boundary using one line of longitude, but this may not be a sufficient description for what could be one of the inner core's most heterogeneous regions. Here, I present a large, hand-picked dataset of PKPbc-PKPdf differential travel times which sample the inner core under Africa, where the proposed position of one hemisphere boundary is located. The dataset contains polar, intermediate and equatorial rays through the inner core, and the presence of crossing raypaths makes regional-scale tomography of the inner core feasible. I invert the data to find regional variations in inner core anisotropy under different parts of Africa, and present both anisotropy and voigt isotropic velocity variations of this important portion of the inner core.

The Recent Microrelief Features of the Yangtze Estuary

NASA Astrophysics Data System (ADS)

Wu, S. H.

2016-02-01

Based on the bedforms date were made in the Yangtze estuary, China, during January 2010 and July 2015 with the acoustic multi-beam bathymetric and shallow sediment profiler and surface sediment samples collected recently, the microrelief features of the Yangtze Estuary under the human interference recently is studied. Results show that in addition to four types of common microrelief (smooth bedfloors , sandwaves, hollow and gully), but also there are two types of microrelief under the human interference (sand and dredging mark).Restricted by the nature of sediment, sand waves exist only in the local region of the South Channel, the North Channel the South Passage and the Hengsha passage whose main types of the surface sediment was fine sand. Under the combined effect of a series of large-scale engineering with watershed and estuary, the upper reach of North Channel, the Hengsha passage, the upper reach of south Channel and the upper reach of the South passage are subject to different degrees of erosion recently, so there are varying degrees of erosive microrelief (hollow and gully). Due to dredging engineering and artificial disordered mining, there are a huge range of dredging mark in the lower reach of South Channel, Yuanyuansha channel and North passage and there are a degree of sand in the main channel of south side of Ruifengsha.

Analysis of substrate degradation, metabolite formation and microbial community responses in sand bioreactors treating winery wastewater: a comparative study.

PubMed

Welz, P J; Palmer, Z; Isaacs, S; Kirby, B; le Roes-Hill, M

2014-12-01

There is a global need for the implementation of more cost-effective green technologies for the treatment of effluent from wineries. However, systems reliant on microbial biodegradation may be adversely affected by the highly seasonal character of cellar waste. In this study, the biodegradation of two different formulations of winery effluent in sand bioreactors was compared. The degradation of organic substrates and formation of metabolites was monitored by physicochemical analyses of pore water and final effluent samples. Changes in the bacterial community structures were detected using molecular fingerprinting. In wastewater with an overall COD of 2027 mg/L, a formulation with a high concentration of acetate (800 mg COD/L) was more recalcitrant to degradation than a formulation with a high concentration of glucose (800 mg COD/L). Ethanol, glucose and phenolics were degraded preferentially in the deeper layers of the sand bioreactors (average Eh 25 mV) than in the superficial layers (average Eh 102 mV). The redox status also played a pivotal role on the bacterial community composition. The study yielded valuable insight that can be utilized in the design (configuration and operation) of full scale sand bioreactors. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modern sedimentation processes in a wave-dominated coastal embayment: Espírito Santo Bay, southeast Brazil

NASA Astrophysics Data System (ADS)

Bastos, Alex Cardoso; Costa Moscon, Daphnne Moraes; Carmo, Dannilo; Neto, José Antonio Baptista; da Silva Quaresma, Valéria

2015-02-01

Sediment dynamics in wave-dominated coastal embayments are generally controlled by seasonal meteorological conditions, storms having a particularly strong influence. In the present study, such hydrodynamic processes and associated deposits have been investigated in a coastal embayment located along the southeast coast of Brazil, i.e. Espírito Santo Bay, in the winter (June/July) of 2008. The bay has undergone a series of human interventions that have altered the local hydrodynamic processes and, consequently, the sediment transport patterns. Facies distribution and sediment dynamics were examined by acoustic seabed mapping, sediment and core sampling, hydrodynamic measurements and sand transport modelling. The results show that sediment distribution can be described in terms of nearshore and offshore zones. The offshore bay sector is predominantly composed of "palimpsest" lithoclastic medium-coarse sands deposited in the course of the early Holocene transgression that peaked about 5,000 years ago. In the inner bay or nearshore zone (up to depths of 4-8 m), these older transgressive deposits are today overlain by a thin (up to 30-cm-thick) and partly patchy blanket of younger regressive fine sand/muddy fine sands. Both coarse- and fine-grained facies are being reworked during high-energy events (Hs>1.5 m) when fine sediment is resuspended, weak tide-induced drift currents causing the sand patches to be displaced. The coarser sediment, by contrast, is mobilized as bedload to produce wave ripples with spacings of up to 1.2 m. These processes lead to a sharp spatial delimitation between a fine sand/mud facies and a rippled coarse sand facies. The fine sand patches have a relief of about 20-30 cm and reveal a typical internal tempestite depositional sequence. Fair-weather wave-induced sediment transport (Hs<1 m), supported by weak tidal currents, seems to only affect the fine sediment facies. Sediment dynamics in Espírito Santo Bay is thus essentially controlled by wave action during storms, tidal currents playing a very subordinate role. Anthropogenic changes due to the construction of a port at the entrance of the bay have not only produced erosion along the beach, but could also explain the occurrence of sand patches concentrated in the north-eastern part of the bay. Because storm-induced deposits of the type observed in this study have an inherently patchy distribution, this feature needs to be taken into consideration when interpreting the rock record in terms of modern analogues.

LARGE-SCALE NATURAL GRADIENT TRACER TEST IN SAND AND GRAVEL, CAPE COD, MASSACHUSETTS - 1. EXPERIMENTAL DESIGN AND OBSERVED TRACER MOVEMENT

EPA Science Inventory

A large-scale natural gradient tracer experiment was conducted on Cape Cod, Massachusetts, to examine the transport and dispersion of solutes in a sand and gravel aquifer. The nonreactive tracer, bromide, and the reactive tracers, lithium and molybdate, were injected as a pulse i...

Pilot- and bench-scale testing of faecal indicator bacteria survival in marine beach sand near point sources.

PubMed

Mika, K B; Imamura, G; Chang, C; Conway, V; Fernandez, G; Griffith, J F; Kampalath, R A; Lee, C M; Lin, C-C; Moreno, R; Thompson, S; Whitman, R L; Jay, J A

2009-07-01

Factors affecting faecal indicator bacteria (FIB) and pathogen survival/persistence in sand remain largely unstudied. This work elucidates how biological and physical factors affect die-off in beach sand following sewage spills. Solar disinfection with mechanical mixing was pilot-tested as a disinfection procedure after a large sewage spill in Los Angeles. Effects of solar exposure, mechanical mixing, predation and/or competition, season, and moisture were tested at bench scale. First-order decay constants for Escherichia coli ranged between -0.23 and -1.02 per day, and for enterococci between -0.5 and -1.0 per day. Desiccation was a dominant factor for E. coli but not enterococci inactivation. Effects of season were investigated through a comparison of experimental results from winter, spring, and fall. Moisture was the dominant factor controlling E. coli inactivation kinetics. Initial microbial community and sand temperature were also important factors. Mechanical mixing, common in beach grooming, did not consistently reduce bacterial levels. Inactivation rates are mainly dependent on moisture and high sand temperature. Chlorination was an effective disinfection treatment in sand microcosms inoculated with raw influent.

Electrochemical and Dry Sand Impact Erosion Studies on Carbon Steel

PubMed Central

Naz, M. Y.; Ismail, N. I.; Sulaiman, S. A.; Shukrullah, S.

2015-01-01

This study investigated the dry and aqueous erosion of mild steel using electrochemical and dry sand impact techniques. In dry sand impact experiments, mild steel was eroded with 45 μm and 150 μm sand particles. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and micro-hardness techniques were used to elaborate the surface morphology of the eroded samples. The results revealed significant change in morphology of the eroded samples. In-depth analysis showed that although the metal erosion due to larger particles was significantly higher, the fines also notably damaged the metal surface. The surface damages were appreciably reduced with decrease in impact angle of the accelerated particles. The maximum damages were observed at an impact angle of 90°. The hardness of the samples treated with 45 μm and 150 μm sand remained in the range of 88.34 to 102.31 VHN and 87.7 to 97.55 VHN, respectively. In electrochemical experiments, a triple electrode probe was added into the metal treatment process. The linear polarization resistance (LPR) measurements were performed in slurries having 5% (by weight) of sand particles. LPR of the samples treated with 45 μm and 150 μm sand slurries was calculated about 949 Ω.cm2 and 809 Ω.cm2, respectively. PMID:26561231

Electrochemical and Dry Sand Impact Erosion Studies on Carbon Steel.

PubMed

Naz, M Y; Ismail, N I; Sulaiman, S A; Shukrullah, S

2015-11-12

This study investigated the dry and aqueous erosion of mild steel using electrochemical and dry sand impact techniques. In dry sand impact experiments, mild steel was eroded with 45 μm and 150 μm sand particles. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and micro-hardness techniques were used to elaborate the surface morphology of the eroded samples. The results revealed significant change in morphology of the eroded samples. In-depth analysis showed that although the metal erosion due to larger particles was significantly higher, the fines also notably damaged the metal surface. The surface damages were appreciably reduced with decrease in impact angle of the accelerated particles. The maximum damages were observed at an impact angle of 90°. The hardness of the samples treated with 45 μm and 150 μm sand remained in the range of 88.34 to 102.31 VHN and 87.7 to 97.55 VHN, respectively. In electrochemical experiments, a triple electrode probe was added into the metal treatment process. The linear polarization resistance (LPR) measurements were performed in slurries having 5% (by weight) of sand particles. LPR of the samples treated with 45 μm and 150 μm sand slurries was calculated about 949 Ω.cm(2) and 809 Ω.cm(2), respectively.

The physics of wind-blown sand and dust.

PubMed

Kok, Jasper F; Parteli, Eric J R; Michaels, Timothy I; Karam, Diana Bou

2012-10-01

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.

The physics of wind-blown sand and dust

NASA Astrophysics Data System (ADS)

Kok, Jasper F.; Parteli, Eric J. R.; Michaels, Timothy I.; Karam, Diana Bou

2012-10-01

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.

Shifting sources and transport paths for the late Quaternary Escanaba Trough sediment fill (northeast Pacific)

USGS Publications Warehouse

Zuffa, G.G.; De Rosa, R.; Normark, W.R.

1997-01-01

Escanaba Trough, which forms the southernmost part of the axial valley of the actively spreading Gorda Ridge, is filled with several hundred meters of sediment of presumed late Quaternary age. Surficial sediment samples from gravity cores, deeper samples (as much as 390 m) from Site 35 of the Deep Sea Drilling Program (Leg 5), and the acoustic character of the sediment fill observed on seismic-reflection profiles indicate that much of the sediment fill is of turbidite origin. Gross composition and heavy- mineral analyses of sand samples show that two distinct petrofacies comprise the sediment fill. The lower part of the fill was derived primarily from the Klamath River source of northern California while the younger fill, including the surficial sand beds, are from the Columbia River drainage much farther north. The Escanaba Trough sediment provides an opportunity to evaluate concepts for paleogeographic and paleotectonic reconstructions that are based on facies analysis and compositional and textural data for the volcanic components because both intrabasinal and extrabasinal sources are present as well as coeval (neovolcanic) and non coeval (paleovolcanic) sourcre This study of a modern basin shows, that although the sediment sources could be identified, it was useful to have some knowledge of the sediment pathway(s), the effects of diagenesis, and the possible effects of sediment sorting as a result of long transport distances from the source area for some components. Application of these same techniques to ancient deposits without benefit of the additional parameters will face limitations.

Summary Fracturing of Coso Samples with StimuFrac

DOE Data Explorer

Carlos Fernandez

2016-09-06

Lab-scale stimulation was performed on Coso samples obtained from a single core (1623 feet TVD, reservoir Coso CGC 18-27) using StimuFrac and control fluid in the absence of stimuli-responsive polymer.

4D XMT of Reaction in Carbonates: Reactive Transport Dynamics at Multiples Scales

NASA Astrophysics Data System (ADS)

Menke, H. P.; Reynolds, C. A.; Andrew, M. G.; Nunes, J. P. P.; Bijeljic, B.; Blunt, M. J.

2016-12-01

Upscaling pore scale rock-fluid interaction processes for predictive modelling poses a challenge to underground carbon storage. We have completed experiments and flow modelling to investigate the impact of pore-space heterogeneity and scale on the dissolution of two limestones at both the mm and cm scales. Two samples were reacted with reservoir condition CO2-saturated brine at both scales and scanned dynamically as dissolution took place. First, 1-cm long 4-mm diameter micro cores were scanned during reactive flow at a 4-μm resolution between 4 and 40 times using 4D X-ray micro-tomography over the course of 1.5 hours using a laboratory μ-CT. Second, 3.8-cm diameter, 8-cm long macro cores were reacted at the same conditions inside a reservoir condition flow rig and imaged using a medical CT scanner. Each sample was imaged 10 times over the course of 1.5 hours at a 250 x 250 x 500-μm resolution. The reacted macro cores were then scanned inside a μ-CT at a 27-μm resolution to assess the alteration in pore-scale reaction-induced heterogeneity. It was found that both limestones showed channel formation at the pore-scale and progressive high porosity pathway dissolution at the core-scale with the more heterogeneous rock having dissolution progressing along direction of flow more quickly. Additionally, upon analysis of the high-resolution macro core images it was found that the dissolution pathways contained a distinct microstructure that was not visible at the resolution of the medical CT, where the reactive fluid had not completely dissolved the internal pore-structure. Flow was modelled in connected pathways, the flow streamlines were traced and streamline density for each voxel was calculated. It was found that the streamline density was highest in the most well-connected pathways and that density increased with increasing heterogeneity as the number of connected pathways decreased and flow was consolidated along fewer pathways. This work represents the first study of scale dependency using reservoir condition 4D X-ray tomography and provides insight into the mechanisms that control local reaction rates at multiple scales.

Geologic columns for the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure: Impactites and crystalline rocks, 1766 to 1096 m depth

USGS Publications Warehouse

Horton, J. Wright; Gibson, R.L.; Reimold, W.U.; Wittmann, A.; Gohn, G.S.; Edwards, L.E.

2009-01-01

The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville drill cores from the Chesapeake Bay impact structure provide one of the most complete geologic sections ever obtained from an impact structure. This paper presents a series of geologic columns and descriptive lithologic information for the lower impactite and crystalline-rock sections in the cores. The lowermost cored section (1766-1551 m depth) is a complex assemblage of mica schists that commonly contain graphite and fibrolitic sillimanite, intrusive granite pegmatites that grade into coarse granite, and local zones of mylonitic deformation. This basement-derived section is variably overprinted by brittle cataclastic fabrics and locally cut by dikes of polymict impact breccia, including several suevite dikes. An overlying succession of suevites and lithic impact breccias (1551-1397 m) includes a lower section dominated by polymict lithic impact breccia with blocks (up to 17 m) and boulders of cataclastic gneiss and an upper section (above 1474 m) of suevites and clast-rich impact melt rocks. The uppermost suevite is overlain by 26 m (1397-1371 m) of gravelly quartz sand that contains an amphibolite block and boulders of cataclasite and suevite. Above the sand, a 275-m-thick allochthonous granite slab (1371-1096 m) includes gneissic biotite granite, fine- and medium-to-coarse-grained biotite granites, and red altered granite near the base. The granite slab is overlain by more gravelly sand, and both are attributed to debris-avalanche and/or rockslide deposition that slightly preceded or accompanied seawater-resurge into the collapsing transient crater. ?? 2009 The Geological Society of America.

Bioenhanced dissolution of dense non-aqueous phase of trichloroethylene as affected by iron reducing conditions: model systems and environmental samples.

PubMed

Paul, Laiby; Smolders, Erik

2015-01-01

The anaerobic biotransformation of trichloroethylene (TCE) can be affected by competing electron acceptors such as Fe (III). This study assessed the role of Fe (III) reduction on the bioenhanced dissolution of TCE dense non-aqueous phase liquid (DNAPL). Columns were set up as 1-D diffusion cells consisting of a lower DNAPL layer, a layer with an aquifer substratum and an upper water layer that is regularly refreshed. The substrata used were either inert sand or sand coated with 2-line ferrihydrite (HFO) or two environmental Fe (III) containing samples. The columns were inoculated with KB-1 and were repeatedly fed with formate. In none of the diffusion cells, vinyl chloride or ethene was detected while dissolved and extractable Fe (II) increased strongly during 60 d of incubation. The cis-DCE concentration peaked at 4.0 cm from the DNAPL (inert sand) while it was at 3.4 cm (sand+HFO), 1.7 cm and 2.5 cm (environmental samples). The TCE concentration gradients near the DNAPL indicate that the DNAPL dissolution rate was larger than that in an abiotic cell by factors 1.3 (inert sand), 1.0 (sand+HFO) and 2.2 (both environmental samples). This results show that high bioavailable Fe (III) in HFO reduces the TCE degradation by competitive Fe (III) reduction, yielding lower bioenhanced dissolution. However, Fe (III) reduction in environmental samples was not reducing TCE degradation and the dissolution factor was even larger than that of inert sand. It is speculated that physical factors, e.g. micro-niches in the environmental samples protect microorganisms from toxic concentrations of TCE. Copyright © 2014 Elsevier Ltd. All rights reserved.

On the relation between fluvio-deltaic flood basin geomorphology and the wide-spread occurrence of arsenic pollution in shallow aquifers.

PubMed

Donselaar, Marinus E; Bhatt, Ajay G; Ghosh, Ashok K

2017-01-01

Pollution of groundwater with natural (geogenic) arsenic occurs on an enormous, world-wide scale, and causes wide-spread, serious health risks for an estimated more than hundred million people who depend on the use of shallow aquifers for drinking and irrigation water. A literature review of key studies on arsenic concentration levels yields that Holocene fluvial and deltaic flood basins are the hotspots of arsenic pollution, and that the dominant geomorphological setting of the arsenic-polluted areas consists of shallow-depth meandering-river deposits with sand-prone fluvial point-bar deposits surrounded by clay-filled (clay plug) abandoned meander bends (oxbow lakes). Analysis of the lithofacies distribution and related permeability contrasts of the geomorphological elements in two cored wells in a point bar and adjacent clay plug along the Ganges River, in combination with data of arsenic concentrations and organic matter content reveals that the low-permeable clay-plug deposits have a high organic matter content and the adjacent permeable point-bar sands show high but spatially very variable arsenic concentrations. On the basis of the geomorphological juxtaposition, the analysis of fluvial depositional processes and lithofacies characteristics, inherent permeability distribution and the omnipresence of the two geomorphological elements in Holocene flood basins around the world, a generic model is presented for the wide-spread arsenic occurrence. The anoxic deeper part (hypolimnion) of the oxbow lake, and the clay plugs are identified as the loci of reactive organic carbon and microbial respiration in an anoxic environment that triggers the reductive dissolution of iron oxy-hydroxides and the release of arsenic on the scale of entire fluvial floodplains and deltaic basins. The adjacent permeable point-bar sands are identified as the effective trap for the dissolved arsenic, and the internal permeability heterogeneity is the cause for aquifer compartmentalization, with large arsenic concentration differences between neighboring compartments. Copyright © 2016 Elsevier B.V. All rights reserved.

Analytical mesoscale modeling of aeolian sand transport

NASA Astrophysics Data System (ADS)

Lämmel, Marc; Kroy, Klaus

2017-11-01

The mesoscale structure of aeolian sand transport determines a variety of natural phenomena studied in planetary and Earth science. We analyze it theoretically beyond the mean-field level, based on the grain-scale transport kinetics and splash statistics. A coarse-grained analytical model is proposed and verified by numerical simulations resolving individual grain trajectories. The predicted height-resolved sand flux and other important characteristics of the aeolian transport layer agree remarkably well with a comprehensive compilation of field and wind-tunnel data, suggesting that the model robustly captures the essential mesoscale physics. By comparing the predicted saturation length with field data for the minimum sand-dune size, we elucidate the importance of intermittent turbulent wind fluctuations for field measurements and reconcile conflicting previous models for this most enigmatic emergent aeolian scale.

The Shell Seeker: What Is the Quantity of Shell in the Lido di Venezia Sand? A Calibration DRIFTS Experiment

ERIC Educational Resources Information Center

Pezzolo, Alessandra De Lorenzi

2011-01-01

In this experiment, students are given a fanciful application of the standard addition method to evaluate the approximate quantity of the shell component in a sample of sand collected on the Lido di Venezia seashore. Several diffuse reflectance infrared Fourier transform (DRIFT) spectra are recorded from a sand sample before and after addition of…

Foreshore sand as a source of Escherichia coli in nearshore water of a Lake Michigan beach.

PubMed

Whitman, Richard L; Nevers, Meredith B

2003-09-01

Swimming advisories due to excessive Escherichia coli concentrations are common at 63rd Street Beach, Chicago, Ill. An intensive study was undertaken to characterize the source and fate of E. coli in beach water and sand at the beach. From April through September 2000, water and sand samples were collected daily or twice daily at two depths on three consecutive days per week (water samples, n = 1,747; sand samples, n = 858); hydrometeorological conditions and bird and bather distributions were also recorded. E. coli concentrations in sand and water were significantly correlated, with the highest concentration being found in foreshore sand, followed by those in submerged sediment and water of increasing depth. Gull contributions to E. coli densities in sand and water were most apparent on the day following gull activity in a given area. E. coli recolonized newly placed foreshore sand within 2 weeks. Analysis of variance, correlation, cluster analyses, concentration gradients, temporal-spatial distribution, demographic patterns, and DNA fingerprinting suggest that E. coli may be able to sustain population density in temperate beach sand during summer months without external inputs. This research presents evidence that foreshore beach sand (i) plays a major role in bacterial lake water quality, (ii) is an important non-point source of E. coli to lake water rather than a net sink, (iii) may be environmentally, and perhaps hygienically, problematic, and (iv) is possibly capable of supporting an autochthonous, high density of indicator bacteria for sustained periods, independent of lake, human, or animal input.

Preliminary Facies Reconstruction of a Late Pleistocene Cypress Forest Discovered on the Northern Gulf of Mexico Continental Shelf

NASA Astrophysics Data System (ADS)

Gonzalez Rodriguez, S. M.; Bentley, S. J.; DeLong, K. L.; Xu, K.; Caporaso, A.; Obelcz, J. B.; Harley, G. L.; Reese, C. A.; Truong, J. T.

2016-12-01

We are investigating the origin and preservation of an ancient bald cypress forest (Taxodium distichum) discovered on the continental shelf seafloor, offshore of Gulf Shores, Alabama, USA, in 20 m water depth. The forest was likely buried in the late Pleistocene, possibly exhumed by Hurricane Ivan in 2004, and is now exposed as stumps in life position with little evidence of decay before recent marine exposure. Radiocarbon analyses show that the forest age is near (and in some cases beyond) the limits of 14C dating, at least 41-45 ky BP. In August 2015 and July 2016, submersible vibracores (up to 5 m in length) were collected. Ongoing core analyses include: organic content (loss on ignition), granulometry, and core logging using a Geotek Multi Sensor Core Logger to generate imagery, bulk density, and x-ray fluorescence data. To bolster 14C analyses, cores collected in 2016 are presently being dated using optically stimulated luminescence. Local stratigraphy consists of a surface facies of Holocene transgressive sands, underlain by possible estuarine sediments of interbedded sand and mud (potentially Holocene or Pleistocene), overlying a swamp or delta plain facies (likely Pleistocene) containing woody debris and mud. Deeper woody facies are thought to include the soil horizons of the ancient cypress forest. Cores collected in 2016 revealed a Pleistocene paleosol beneath Holocene sands in a nearby trough. Elevation differences between swamp and paleosol horizons will be evaluated from bathymetric and subbottom data, to help characterize the preserved ancient landscape. Initial interpretation based on close proximity of Pleistocene swamp and oxidized paleosol sediments, and regional geomorphic gradients suggest that this relatively diverse assemblage of facies developed up to tens of km from the glacial-age coastline, and relatively rapid burial prevented erosion by coastal processes during the Holocene transgression thus preserving the tree stumps and wood debris.

K West Basin Sand Filter Backwash Sample Analysis

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

Fiskum, Sandra K.; Smoot, Margaret R.; Coffey, Deborah S.

A sand filter is used to help maintain water clarity at the K West Basin where highly radioactive sludge is stored. Eventually that sand filter will require disposal. The radionuclide content of the solids trapped in the sand filter will affect the selection of the sand filter disposal pathway. The Pacific Northwest National Laboratory (PNNL) was contracted by the K Basin Operations & Plateau Remediation Project (operations contractor CH2M Hill) to analyze the radionuclide content of the solids collected from the backwash of the K West Basin sand filter. The radionuclide composition in the sand filter backwash solids will bemore » used by CH2M Hill to determine if the sand filter media and retained sludge solids will be designated as transuranic waste for disposal purposes or can be processed through less expensive means. On October 19, 2015, K Basin Operations & Plateau Remediation Project staff backwashed the sand filter into the North Load-Out Pit (NLOP) and immediately collected sample slurry from a sampling tube positioned 24 in. above the NLOP floor. The 764 g sand filter backwash slurry sample, KW-105 SFBW-001, was submitted to PNNL for analysis on October 20, 2015. Solids from the slurry sample were consolidated into two samples (i.e., a primary and a duplicate sample) by centrifuging and measured for mass (0.82 g combined – wet centrifuged solids basis) and volume (0.80 mL combined). The solids were a dark brown/orange color, consistent with iron oxide/hydroxide. The solids were dried; the combined dry solids mass was 0.1113 g, corresponding to 0.0146 weight percent (wt%) solids in the original submitted sample slurry. The solids were acid-digested using nitric and hydrochloric acids. Insoluble solids developed upon dilution with 0.5 M HNO 3, corresponding to an average 6.5 wt% of the initial dry solids content. The acid digestate and insoluble solids were analyzed separately by gamma spectrometry. Nominally, 7.7% of the 60Co was present in the insoluble solids; less than 1% of other gamma-emitters (i.e., 137Cs, 154/155Eu, and 241Am) were present in the insoluble solids. Aliquots of the acid digestate were analyzed directly using gamma energy analysis (GEA) and after separations for 238Pu, 239+240Pu, 237Np, and 241Am radioisotopes using alpha energy analysis (AEA). The 90Sr was measured by liquid scintillation counting (LSC) on the Sr-separated fraction. The plutonium isotopic distribution of the acid digestate was analyzed following Pu separations by thermal ionization mass spectrometry (TIMS). A table summarizes the results for the primary and duplicate samples. The 239+240Pu concentration (µCi/g dry) relative to 90Sr and to 137Cs concentrations (µCi/g dry) was examined. The K West Basin sludge has a 239+240Pu/ 90Sr ranging from 0.1 to 1.2 and the 239+240Pu/ 137Cs ratio ranging from 0.10 to 0.47. In contrast, the sand filter backwash solids 239+240Pu/ 90Sr ratio was 10.6 and the 239+240Pu/ 137Cs ratio was 2.0. The ratio differences indicate a relative enhancement of the Pu concentration in the sand filter solids relative to the 137Cs and 90Sr sludge concentrations currently in the K West Basin. A dose-to-curie radioisotope evaluation of the sand filter waste form may need to consider this dissimilarity.« less

Capillary pressure heterogeneity and hysteresis for the supercritical CO2/water system in a sandstone

NASA Astrophysics Data System (ADS)

Pini, Ronny; Benson, Sally M.

2017-10-01

We report results from an experimental investigation on the hysteretic behaviour of the capillary pressure curve for the supercritical CO2-water system in a Berea Sandstone core. Previous observations have highlighted the importance of subcore-scale capillary heterogeneity in developing local saturations during drainage; we show in this study that the same is true for the imbibition process. Spatially distributed drainage and imbibition scanning curves were obtained for mm-scale subsets of the rock sample non-invasively using X-ray CT imagery. Core- and subcore-scale measurements are well described using the Brooks-Corey formalism, which uses a linear trapping model to compute mobile saturations during imbibition. Capillary scaling yields two separate universal drainage and imbibition curves that are representative of the full subcore-scale data set. This enables accurate parameterisation of rock properties at the subcore-scale in terms of capillary scaling factors and permeability, which in turn serve as effective indicators of heterogeneity at the same scale even when hysteresis is a factor. As such, the proposed core-analysis workflow is quite general and provides the required information to populate numerical models that can be used to extend core-flooding experiments to conditions prevalent in the subsurface, which would be otherwise not attainable in the laboratory.

Structure of the Wechsler Intelligence Scale for Children-Fourth Edition among a National Sample of Referred Students

ERIC Educational Resources Information Center

Watkins, Marley W.

2010-01-01

The structure of the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV; D. Wechsler, 2003a) was analyzed via confirmatory factor analysis among a national sample of 355 students referred for psychoeducational evaluation by 93 school psychologists from 35 states. The structure of the WISC-IV core battery was best represented by four…

An innovative piston corer for large‐volume sediment samples

PubMed Central

Haselmair, Alexandra; Stachowitsch, Michael; Zuschin, Martin

2016-01-01

Abstract Coring is one of several standard procedures to extract sediments and their faunas from open marine, estuarine, and limnic environments. Achieving sufficiently deep penetration, obtaining large sediment volumes in single deployments, and avoiding sediment loss upon retrieval remain problematic. We developed a piston corer with a diameter of 16 cm that enables penetration down to 1.5 m in a broad range of soft bottom types, yields sufficient material for multiple analyses, and prevents sediment loss due to a specially designed hydraulic core catcher. A novel extrusion system enables very precise slicing and preserves the original sediment stratification by keeping the liners upright. The corer has moderate purchase costs and a robust and simple design that allows for a deployment from relatively small vessels as available at most marine science institutions. It can easily be operated by two to three researchers rather than by specially trained technicians. In the northern Adriatic Sea, the corer successfully extracted more than 50 cores from a range of fine mud to coarse sand, at water depths from three to 45 m. The initial evaluation of the cores demonstrated their usefulness for fauna sequences along with heavy metal, nutrient and pollutant analyses. Their length is particularly suited for historical ecological work requiring sedimentary and faunal sequences to reconstruct benthic communities over the last millennia. PMID:28111529

Microbes in Beach Sands: Integrating Environment, Ecology and Public Health

PubMed Central

Whitman, Richard; Harwood, Valerie J.; Edge, Thomas A.; Nevers, Meredith; Byappanahalli, Muruleedhara; Vijayavel, Kannappan; Brandão, João; Sadowsky, Michael J.; Alm, Elizabeth Wheeler; Crowe, Allan; Ferguson, Donna; Ge, Zhongfu; Halliday, Elizabeth; Kinzelman, Julie; Kleinheinz, Greg; Przybyla-Kelly, Kasia; Staley, Christopher; Staley, Zachery; Solo-Gabriele, Helena M.

2014-01-01

SUMMARY Beach sand is a habitat that supports many microbes, including viruses, bacteria, fungi and protozoa (micropsammon). The apparently inhospitable conditions of beach sand environments belie the thriving communities found there. Physical factors, such as water availability and protection from insolation; biological factors, such as competition, predation, and biofilm formation; and nutrient availability all contribute to the characteristics of the micropsammon. Sand microbial communities include autochthonous species/phylotypes indigenous to the environment. Allochthonous microbes, including fecal indicator bacteria (FIB) and waterborne pathogens, are deposited via waves, runoff, air, or animals. The fate of these microbes ranges from death, to transient persistence and/or replication, to establishment of thriving populations (naturalization) and integration in the autochthonous community. Transport of the micropsammon within the habitat occurs both horizontally across the beach, and vertically from the sand surface and ground water table, as well as at various scales including interstitial flow within sand pores, sediment transport for particle-associated microbes, and the large-scale processes of wave action and terrestrial runoff. The concept of beach sand as a microbial habitat and reservoir of FIB and pathogens has begun to influence our thinking about human health effects associated with sand exposure and recreational water use. A variety of pathogens have been reported from beach sands, and recent epidemiology studies have found some evidence of health risks associated with sand exposure. Persistent or replicating populations of FIB and enteric pathogens have consequences for watershed/beach management strategies and regulatory standards for safe beaches. This review summarizes our understanding of the community structure, ecology, fate, transport, and public health implications of microbes in beach sand. It concludes with recommendations for future work in this vastly under-studied area. PMID:25383070

Forensic source differentiation of petrogenic, pyrogenic, and biogenic hydrocarbons in Canadian oil sands environmental samples.

PubMed

Wang, Zhendi; Yang, C; Parrott, J L; Frank, R A; Yang, Z; Brown, C E; Hollebone, B P; Landriault, M; Fieldhouse, B; Liu, Y; Zhang, G; Hewitt, L M

2014-04-30

To facilitate monitoring efforts, a forensic chemical fingerprinting methodology has been applied to characterize and differentiate pyrogenic (combustion derived) and biogenic (organism derived) hydrocarbons from petrogenic (petroleum derived) hydrocarbons in environmental samples from the Canadian oil sands region. Between 2009 and 2012, hundreds of oil sands environmental samples including water (snowmelt water, river water, and tailings pond water) and sediments (from river beds and tailings ponds) have been analyzed. These samples were taken from sites where assessments of wild fish health, invertebrate communities, toxicology and detailed chemistry are being conducted as part of the Canada-Alberta Joint Oil Sands Monitoring Plan (JOSMP). This study describes the distribution patterns and potential sources of PAHs from these integrated JOSMP study sites, and findings will be linked to responses in laboratory bioassays and in wild organisms collected from these same sites. It was determined that hydrocarbons in Athabasca River sediments and waters were most likely from four sources: (1) petrogenic heavy oil sands bitumen; (2) biogenic compounds; (3) petrogenic hydrocarbons of other lighter fuel oils; and (4) pyrogenic PAHs. PAHs and biomarkers detected in snowmelt water samples collected near mining operations imply that these materials are derived from oil sands particulates (from open pit mines, stacks and coke piles). Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

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

Cox, D.L.

The Berea Sandstone is a widely recognized producer of oil and gas in the Appalachian basin. Subsurface mapping, core analysis, and production data from producing wells have been evaluated in west-central West Virginia, where the Berea Sandstone represents a wide range of nearshore and coastal environments. Fluvial system deposits are found in southern Jackson County as channel sands (Gay-Fink) and adjacent deltaic facies. Coastal sediments were deposited to the north as intertidal shoals, tidal flats, and coarse-grained tidal-creek point bars. Marine shelf sands are found to the west.

A Mid-Holocene Relative Sea-Level Stack, New Jersey, USA

NASA Astrophysics Data System (ADS)

Horton, B.; Walker, J. S.; Kemp, A.; Shaw, T. J.; Kopp, R. E.

2017-12-01

Most high resolution (decimeter- and decadal-scale) relative sea-level (RSL) records using salt-marsh microfossils as a proxy only extend through the Common Era, limiting our understanding of driving mechanisms of RSL change and how sea-level is influenced by changing climate. Records beyond the Common Era are limited by the depth of continuous sequences of salt-marsh peat suitable for high resolution reconstructions, as well as contamination by local processes such as sediment compaction. In contrast, sequences of basal peats have produced compaction-free RSL records through the Holocene, but at a low resolution (meter- and centennial-scale). We devise a new Multi-Proxy Presence/Absence Method (MP2AM) to develop a mid-Holocene RSL stack. We stack a series of 1 m basal peat cores that overlap along a uniform elevational gradient above an incompressible basal sand. We analyzed three sea-level indicators from 14 cores: foraminifera, testate amoebae, and stable carbon isotope geochemistry. To reconstruct RSL, this multi-proxy approach uses the timesaving presence/absence of forams and testates to determine the elevation of the highest occurrence of forams and the lowest occurrence of testates in each basal core. We use stable carbon isotope geochemistry to determine the C3/C4 vegetation boundary in each core. We develop age-depth models for each core using a series of radiocarbon dates. The RSL records from each 1 m basal core are combined to create a stack or, in effect, one long core of salt-marsh material. This method removes the issue of compaction to create a continuous RSL record to address temporal changes and periods of climate and sea-level variability. We reconstruct a southern NJ mid-Holocene RSL record from Edwin B. Forsythe National Wildlife Refuge, where Kemp et al. (2013) completed a 2500 yr RSL record using a foraminifera-based transfer function approach. Preliminary radiocarbon dates suggest the basal sequence is at least 4246-4408 cal yrs BP. Presence/absence of forams and testates and the transition of C3/C4 vegetation is identified in each core and constrained with radiocarbon dating. A short core with full counts of forams and testates is used to test the new method and compare with the traditional foraminifera-based transfer function approach and the local tide gauge record.

Sand ridges off Sarasota, Florida: A complex facies boundary on a low-energy inner shelf environment

USGS Publications Warehouse

Twichell, D.; Brooks, Gillian L.; Gelfenbaum, G.; Paskevich, V.; Donahue, Brian

2003-01-01

The innermost shelf off Sarasota, Florida was mapped using sidescan-sonar imagery, seismic-reflection profiles, surface sediment samples, and short cores to define the transition between an onshore siliciclastic sand province and an offshore carbonate province and to identify the processes controlling the distribution of these distinctive facies. The transition between these facies is abrupt and closely tied to the morphology of the inner shelf. A series of low-relief nearly shore-normal ridges characterize the inner shelf. Stratigraphically, the ridges are separated from the underlying Pleistocene and Tertiary carbonate strata by the Holocene ravinement surface. While surficial sediment is fine to very-fine siliciclastic sand on the southeastern sides of the ridges and shell hash covers their northwestern sides, the cores of these Holocene deposits are a mixture of both of these facies. Along the southeastern edges of the ridges the facies boundary coincides with the discontinuity that separates the ridge deposits from the underlying strata. The transition from siliciclastic to carbonate sediment on the northwestern sides of the ridges is equally abrupt, but it falls along the crests of the ridges rather than at their edges. Here the facies transition lies within the Holocene deposit, and appears to be the result of sediment reworking by modern processes. This facies distribution primarily appears to result from south-flowing currents generated during winter storms that winnow the fine siliciclastic sediment from the troughs and steeper northwestern sides of the ridges. A coarse shell lag is left armoring the steeper northwestern sides of the ridges, and the fine sediment is deposited on the gentler southeastern sides of the ridges. This pronounced partitioning of the surficial sediment appears to be the result of the siliciclastic sand being winnowed and transported by these currents while the carbonate shell hash falls below the threshold of sediment movement and is left as a lag. The resulting facies boundaries on this low-energy, sediment-starved inner continental shelf are of two origins which both are tied to the remarkably subtle ridge morphology. Along the southeastern sides of the ridges the facies boundary coincides with a stratigraphic discontinuity that separates Holocene from the older deposits while the transition along the northwestern sides of the ridges is within the Holocene deposit and is the result of sediment redistribution by modern processes. ?? 2003 Elsevier B.V. All rights reserved.

Quantifying Sediment Characteristics and Infilling Rate within a Ship Shoal Dredge Borrow Area, Offshore Louisiana

NASA Astrophysics Data System (ADS)

Xue, Z.; Wilson, C.; Bentley, S. J.; Xu, K.; Liu, H.; Li, C.; Miner, M. D.

2017-12-01

Barrier islands provide protection to interior wetlands and maintain estuarine gradients. Mississippi River delta plain barrier islands are undergoing rapid disintegration due to high rates of subsidence and a deficit in the coastal sand supply. To mitigate for barrier island land loss, Louisiana has implemented a restoration program that intends to supplement coastal sand deficits by introducing sand from outside of the active coastal system. Inner-shelf shoals offshore Louisiana are one of the only sand resource options containing large volumes of restoration quality sand. Ship Shoal is one of these inner-shelf shoals that was produced by marine reworking of former Mississippi River Delta barrier island sediments during late Holocene time. Though indirect effects to protected areas or infrastructure adjacent to excavations have been considered, there is a paucity of observational data on their evolution. Caminada borrow area, dredged in 2013-2016 for the Caminada Headland Restoration Project, provides a valuable opportunity to validate and improve predictive models for how borrow areas evolve. In July 2017, a subbottom and bathymetric geophysical survey was conducted and sediment cores were collected to test the hypothesis that sedimentation within the excavation is affected by lateral bedload transport after initial rapid infill as slopes equilibrate. Preliminary results show the sediment within the excavation is predominantly very fine sand with isolated mud drapes. These sediments overlay older delta complex muddy strata. This contrasts strongly with other dredge pits outside of shoal areas and closer to shore, which have been infilled largely by advection of fine suspended sediments of fluvial origin. Laboratory work on cores will include laser grain size, x-ray analyses of sedimentary structures, and radiochemistry analyses for rates and age of deposition. With the knowledge of stratigraphy and sediment dynamics surrounding the dredge pit, we can quantify and better understand the timeline of these depositional processes to provide vital knowledge to coastal managers for future borrow area design and management.

A field study of littoral processes in Estero Bay, California

USGS Publications Warehouse

Dingler, J.R.; Anima, R.J.; Molzan, D.E.; Luepke, Gretchen; Peterson, C.L.

1982-01-01

Estero Bay, which lies on the central California coast, has rocky headlands at both ends and sandy beaches within it. The shoreline of the bay has adjusted to be in equilibrium with the predominant wave climate, which is from the northwest. Because of its present shoreline configuration, the net southward littoral transport found along much of the California coast does not occur within Estero Bay. Instead, the sand primarily moves on- and offshore with a reversing longshore component. This sand transport pattern produces a littoral cell within Estero Bay even though there is no submarine canyon in the area. The primary sand sinks for this cell appear to be the sand spit south of Morro Rock and the entrance to Morro Bay itself, although this opinion was not experimentally verified. Field work during one summer (1978) and the following winter (1979) produced baseline data on the profile of and grain-size distribution across the littoral zone. In the offshore part of the littoral zone we also studied ripple size and type, internal structure, depth of erosion, and mineralogy. Although these data, which were collected along nine transects spaced 2 km apart, are inadequate to yield transport and energy rates, they indicate a northward decrease in wave energy within Estero Bay and a mixing of the sediments in the offshore. Box core and rod height data from grid points in seven meters of water showed that on the order of a meter of erosion occurred in the central part of the bay between the two sampling periods. Offshore, the data were incomplete, but at one station, in 17 m of water, at least 20 cm of erosion occurred.

Colloid transport in dual-permeability media

NASA Astrophysics Data System (ADS)

Leij, Feike J.; Bradford, Scott A.

2013-07-01

It has been widely reported that colloids can travel faster and over longer distances in natural structured porous media than in uniform structureless media used in laboratory studies. The presence of preferential pathways for colloids in the subsurface environment is of concern because of the increased risks for disease caused by microorganisms and colloid-associated contaminants. This study presents a model for colloid transport in dual-permeability media that includes reversible and irreversible retention of colloids and first-order exchange between the aqueous phases of the two regions. The model may also be used to describe transport of other reactive solutes in dual-permeability media. Analytical solutions for colloid concentrations in aqueous and solid phases were obtained using Laplace transformation and matrix decomposition. The solutions proved convenient to assess the effect of model parameters on the colloid distribution. The analytical model was used to describe effluent concentrations for a bromide tracer and 3.2- or 1-μm-colloids that were observed after transport through a composite 10-cm long porous medium made up of a cylindrical lens or core of sand and a surrounding matrix with sand of a different grain size. The tracer data were described very well and realistic estimates were obtained for the pore-water velocity in the two flow domains. An accurate description was also achieved for most colloid breakthrough curves. Dispersivity and retention parameters were typically greater for the larger 3.2-μm-colloids while both reversible and irreversible retention rates tended to be higher for the finer sands than the coarser sand. The relatively small sample size and the complex flow pattern in the composite medium made it difficult to reach definitive conclusions regarding transport parameters for colloid transport.

Electrical conductivity of lab-formed methane hydrate + sand mixtures; technical developments and new results

NASA Astrophysics Data System (ADS)

Stern, L.; Du Frane, W. L.; Weitemeyer, K. A.; Constable, S.; Roberts, J. J.

2012-12-01

Electromagnetic (EM) measurement techniques used in permafrost and marine wells show that electrical conductivity (σ) of gas-hydrate-bearing zones is typically lower than that of surrounding sediments. However, while σ has been measured on analogue materials, it has seldom been studied on methane hydrate, the most common gas hydrate in the shallow geosphere. Additional petrophysical information - such as mixing relations and/or compositions of individual components - is also needed to more accurately relate σ to quantitative estimates of gas hydrate in EM-surveyed regions. To help address these needs, we first quantified the electrical properties of lab-formed methane hydrate at geologically relevant temperatures and pressures (Du Frane et al. GRL, 2011; also AGU 2011). A high-pressure cell was constructed to form hydrate from melting granular ice (made from distilled-deionized water) in the presence of pressurized CH4 gas, while measuring frequency-dependent impedance (Z) and σ. Final samples were pure, polycrystalline methane hydrate with excess CH4 gas but no excess H2O. The hydrate was then either quenched for grain-scale assessment by cryogenic SEM imaging, or dissociated in situ for further Z and σ measurement. Du Frane et al. [GRL, 2011] reported σ of methane hydrate to range from 10-5 to 10-4 S/m between -15 and 15°C, with activation energy (Ea) of 30.6 kJ/mol. In comparison, σ of the dissociated ice byproduct was ~400% higher with ~50% higher Ea. Measurements were then performed on methane hydrate mixed with known amounts of a standard quartz sand (Oklahoma #1, ~125 μm grain size) or similarly-sized silica glass beads in proportions ranging 10 to 90 vol. % relative to the hydrate phase. Several samples were dissociated at temperatures below -3°C for Z and σ measurement of the resulting ice/sand mixtures, and all samples were imaged for phase distribution. Adding sand complicated Z spectra for frequencies < 1 kHz and > 1MHz. However, the impedance at the frequency associated with the highest phase angle (typically 100 kHz) could be used to effectively isolate the electrical response of the sample from system contributions, enabling determination of σ. Surprisingly, the addition of sand, a nominal insulator, served to increase the overall σ of mixtures with sand fractions up through ~50 vol. % (i.e. those samples with well-connected methane hydrate), while Ea significantly decreased relative to single-phase methane hydrate. The reduced Ea suggests that a separate conduction mechanism operates when sand is present. One possible explanation is that ionic impurities from sand surfaces chemically diffuse into the hydrate grains, increasing their concentration of mobile charge-carrying defects. The fact that the addition of glass beads did not produce the same results supports this hypothesis. Geometrical mixing laws alone may therefore not sufficiently describe complicated mixing relationships between gas hydrate and sediment. Further tests are needed to resolve the competing effects, particularly if results are to be applied to systems that are not dominated by the presence of seawater. Work was performed under the auspices of U.S. DOE contracts DE-NT0005668 and DE-AC52-07NA27344, and DOE/USGS Interagency Agreement DE-NT0006147.

Optical dating of tsunami-laid sand from an Oregon coastal lake

USGS Publications Warehouse

Ollerhead, J.; Huntley, D.J.; Nelson, A.R.; Kelsey, H.M.

2001-01-01

Optical ages for five samples of tsunami-laid sand from an Oregon coastal lake were determined using an infrared optical-dating method on K-feldspar separates and, as a test of accuracy, compared to ages determined by AMS 14C dating of detrital plant fragments found in the same beds. Two optical ages were about 20% younger than calibrated 14C ages of about 3.1 and 4.3 ka. Correction of the optical ages using measured anomalous fading rates brings them into agreement with the 14C ages. The approach used holds significant promise for improving the accuracy of infrared optical-dating methods. Luminescence data for the other three samples result in optical age limits much greater than the 14C ages. These data provide a textbook demonstration of the correlation between scatter in the luminescence intensity of individual sample aliquots and their normalization values that is expected when the samples contain sand grains not adequately exposed to daylight just prior to or during deposition and burial. Thus, the data for these three samples suggest that the tsunamis eroded young and old sand deposits before dropping the sand in the lake. ?? 2001 Elsevier Science Ltd. All rights reserved.

Provenance and recycling of Arabian desert sand

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Vermeesch, Pieter; Andò, Sergio; Vezzoli, Giovanni; Valagussa, Manuel; Allen, Kate; Kadi, Khalid; Al-Juboury, Ali

2013-04-01

This study seeks to determine the ultimate origin of aeolian sand in Arabian deserts by high-resolution petrographic and heavy-mineral techniques combined with zircon U-Pb geochronology. Point-counting is used here as the sole method by which unbiased volume percentages of heavy minerals can be obtained. A comprehensive analysis of river and wadi sands from the Red Sea to the Bitlis-Zagros orogen allowed us to characterize all potential sediment sources, and thus to quantitatively constrain provenance of Arabian dune fields. Two main types of aeolian sand can be distinguished. Quartzose sands with very poor heavy-mineral suites including zircon occupy most of the region comprising the Great Nafud and Rub' al-Khali Sand Seas, and are largely recycled from thick Lower Palaeozoic quartzarenites with very minor first-cycle contributions from Precambrian basement, Mesozoic carbonate rocks, or Neogene basalts. Instead, carbonaticlastic sands with richer lithic and heavy-mineral populations characterize coastal dunes bordering the Arabian Gulf from the Jafurah Sand Sea of Saudi Arabia to the United Arab Emirates. The similarity with detritus carried by the axial Tigris-Euphrates system and by transverse rivers draining carbonate rocks of the Zagros indicates that Arabian coastal dunes largely consist of far-travelled sand, deposited on the exposed floor of the Gulf during Pleistocene lowstands and blown inland by dominant Shamal northerly winds. A dataset of detrital zircon U-Pb ages measured on twelve dune samples and two Lower Palaeozoic sandstones yielded fourteen identical age spectra. The age distributions all show a major Neoproterozoic peak corresponding to the Pan-African magmatic and tectonic events by which the Arabian Shield was assembled, with minor late Palaeoproterozoic and Neoarchean peaks. A similar U-Pb signature characterizes also Jafurah dune sands, suggesting that zircons are dominantly derived from interior Arabia, possibly deflated from the Wadi al-Batin fossil alluvial fan or even from Mesozoic sandstones of the Arabian margin accreted to the Cenozoic Zagros orogen. Due to extensive recycling and the fact that zircon is so resistant to weathering and erosion, the U-Pb age signatures are much less powerful a tracer of sedimentary provenance than framework petrography and heavy minerals. Actualistic provenance studies of dune fields at subcontinental scale shed light on the generation and homogenization of aeolian sand, and allow us to trace complex pathways of multistep sediment transport, thus providing crucial independent information for accurate palaeogeographic and palaeoclimatic reconstructions.

Provenance and recycling of Arabian desert sand

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Vermeesch, Pieter; Andò, Sergio; Vezzoli, Giovanni; Valagussa, Manuel; Allen, Kate; Kadi, Khalid A.; Al-Juboury, Ali I. A.

2013-05-01

This study seeks to determine the ultimate origin of aeolian sand in Arabian deserts by high-resolution petrographic and heavy-mineral techniques combined with zircon U-Pb geochronology. Point-counting is used here as the sole method by which unbiased volume percentages of heavy minerals can be obtained. A comprehensive analysis of river and wadi sands from the Red Sea to the Bitlis-Zagros orogen allowed us to characterize all potential sediment sources, and thus to quantitatively constrain provenance of Arabian dune fields. Two main types of aeolian sand can be distinguished. Quartzose sands with very poor heavy-mineral suites including zircon occupy most of the region comprising the Great Nafud and Rub' al-Khali Sand Seas, and are largely recycled from thick Lower Palaeozoic quartzarenites with very minor first-cycle contributions from Precambrian basement, Mesozoic carbonate rocks, or Neogene basalts. Instead, carbonaticlastic sands with richer lithic and heavy-mineral populations characterize coastal dunes bordering the Arabian Gulf from the Jafurah Sand Sea of Saudi Arabia to the United Arab Emirates. The similarity with detritus carried by the axial Tigris-Euphrates system and by transverse rivers draining carbonate rocks of the Zagros indicates that Arabian coastal dunes largely consist of far-travelled sand, deposited on the exposed floor of the Gulf during Pleistocene lowstands and blown inland by dominant Shamal northerly winds. A dataset of detrital zircon U-Pb ages measured on twelve dune samples and two Lower Palaeozoic sandstones yielded fourteen identical age spectra. The age distributions all show a major Neoproterozoic peak corresponding to the Pan-African magmatic and tectonic events by which the Arabian Shield was assembled, with minor late Palaeoproterozoic and Neoarchean peaks. A similar U-Pb signature characterizes also Jafurah dune sands, suggesting that zircons are dominantly derived from interior Arabia, possibly deflated from the Wadi al-Batin fossil alluvial fan or even from Mesozoic sandstones of the Arabian margin accreted to the Cenozoic Zagros orogen. Due to extensive recycling and the fact that zircon is so resistant to weathering and erosion, the U-Pb age signatures are much less powerful a tracer of sedimentary provenance than framework petrography and heavy minerals. Actualistic provenance studies of dune fields at subcontinental scale shed light on the generation and homogenization of aeolian sand, and allow us to trace complex pathways of multistep sediment transport, thus providing crucial independent information for accurate palaeogeographic and palaeoclimatic reconstructions.

Magnetic Tracking of Gas Hydrate Deposits.

NASA Astrophysics Data System (ADS)

Lowe, C.; Enkin, R. J.; Judith, B.; Dallimore, S. R.

2005-12-01

Analysis of recovered core from the Mallik gas hydrate field in the Mackenzie Delta, Northwest Territories, Canada demonstrates that the magnetic properties of hydrate-bearing strata differ significantly from those strata lacking gas hydrate. The recovered core, which extends from just above (885 m) to just below (1152 m) observed gas hydrate occurrences (891-1107 m), comprises a series of six stratigraphic units that are either sand or silt dominated. Gas hydrate is preferentially concentrated in the higher porosity, sand-dominated units. Although the sediment source region for the Mackenzie Delta is sufficiently large that silts and sands have similar primary mineralogy, their magnetic properties are distinct. Magnetite, apparent in silt units with porosities too low to accommodate significant gas hydrate deposits, is reduced to iron sulphide in the gas hydrate-bearing sand horizons. The degree of the observed magnetic reduction increases with increasing gas hydrate concentration. Furthermore, silts retain their primary magnetism, whereas sands are remagnetized. Two independent investigations of marine gas hydrate occurrences (Blake Ridge, offshore eastern USA and Cascadia, offshore western Canada) demonstrate similar magnetic reduction within known gas hydrate fields, and an even larger depletion of magnetic minerals in vent zones where methane is actively fluxing to surface. Collectively, the findings from these three regions indicate that porosity and structure are fundamental controls on methane pathways. Investigations are presently underway to determine the precise triggers and chemical pathways of the observed magnetic reductions. However, findings to date indicate that magnetic studies of host sediments in gas hydrate systems provide a powerful lithologic correlation tool, a window into the processes associated with gas hydrate formation, and form the basis of quantitative analysis of magnetic surveys over gas hydrate deposits.

Reservoir evaluation of thin-bedded turbidites and hydrocarbon pore thickness estimation for an accurate quantification of resource

NASA Astrophysics Data System (ADS)

Omoniyi, Bayonle; Stow, Dorrik

2016-04-01

One of the major challenges in the assessment of and production from turbidite reservoirs is to take full account of thin and medium-bedded turbidites (<10cm and <30cm respectively). Although such thinner, low-pay sands may comprise a significant proportion of the reservoir succession, they can go unnoticed by conventional analysis and so negatively impact on reserve estimation, particularly in fields producing from prolific thick-bedded turbidite reservoirs. Field development plans often take little note of such thin beds, which are therefore bypassed by mainstream production. In fact, the trapped and bypassed fluids can be vital where maximising field value and optimising production are key business drivers. We have studied in detail, a succession of thin-bedded turbidites associated with thicker-bedded reservoir facies in the North Brae Field, UKCS, using a combination of conventional logs and cores to assess the significance of thin-bedded turbidites in computing hydrocarbon pore thickness (HPT). This quantity, being an indirect measure of thickness, is critical for an accurate estimation of original-oil-in-place (OOIP). By using a combination of conventional and unconventional logging analysis techniques, we obtain three different results for the reservoir intervals studied. These results include estimated net sand thickness, average sand thickness, and their distribution trend within a 3D structural grid. The net sand thickness varies from 205 to 380 ft, and HPT ranges from 21.53 to 39.90 ft. We observe that an integrated approach (neutron-density cross plots conditioned to cores) to HPT quantification reduces the associated uncertainties significantly, resulting in estimation of 96% of actual HPT. Further work will focus on assessing the 3D dynamic connectivity of the low-pay sands with the surrounding thick-bedded turbidite facies.

Core Versus Nuclear Gauge Methods of Determining Soil Bulk Density and Moisture Content

Treesearch

Jacqueline G. Steele; Jerry L. Koger; Albert C. Trouse; Donald L. Sirois

1983-01-01

Soil bulk and moisture content measurements were obtained using two nuclear gauge systems and those compared to those obtained from soil cores. The soils, a Hiwassee sandy loam, a Lakeland loamy sand, and a Loyd clay, were free of organic matter and uniform in mechanical composition. The regression equations developed for the nuclear guages for the first phase of the...

Evaluating process origins of sand-dominated fluvial stratigraphy

NASA Astrophysics Data System (ADS)

Chamberlin, E.; Hajek, E. A.

2015-12-01

Sand-dominated fluvial stratigraphy is often interpreted as indicating times of relatively slow subsidence because of the assumption that fine sediment (silt and clay) is reworked or bypassed during periods of low accommodation. However, sand-dominated successions may instead represent proximal, coarse-grained reaches of paleo-river basins and/or fluvial systems with a sandy sediment supply. Differentiating between these cases is critical for accurately interpreting mass-extraction profiles, basin-subsidence rates, and paleo-river avulsion and migration behavior from ancient fluvial deposits. We explore the degree to which sand-rich accumulations reflect supply-driven progradation or accommodation-limited reworking, by re-evaluating the Castlegate Sandstone (Utah, USA) and the upper Williams Fork Formation (Colorado, USA) - two Upper Cretaceous sandy fluvial deposits previously interpreted as having formed during periods of relatively low accommodation. Both units comprise amalgamated channel and bar deposits with minor intra-channel and overbank mudstones. To constrain relative reworking, we quantify the preservation of bar deposits in each unit using detailed facies and channel-deposit mapping, and compare bar-deposit preservation to expected preservation statistics generated with object-based models spanning a range of boundary conditions. To estimate the grain-size distribution of paleo-sediment input, we leverage results of experimental work that shows both bed-material deposits and accumulations on the downstream side of bars ("interbar fines") sample suspended and wash loads of active flows. We measure grain-size distributions of bar deposits and interbar fines to reconstruct the relative sandiness of paleo-sediment supplies for both systems. By using these novel approaches to test whether sand-rich fluvial deposits reflect river systems with accommodation-limited reworking and/or particularly sand-rich sediment loads, we can gain insight into large-scale downstream-fining and mass-extraction trends in basins with limited exposure.

Recent marine deposits reconstruction of two depositional environments of the French Atlantic coast

NASA Astrophysics Data System (ADS)

Pouzet, Pierre; Maanan, Mohamed; Schmidt, Sabine; Athimon, Emmanuelle; Robin, Marc

2017-04-01

This work provides a 300-yr high-resolution record of past storm and/or tsunami events using a multi-proxy analysis (137Cs and 210Pb dating, chemical composition and grain size) of sedimentary deposits from two coastal depositional environments of the French Atlantic coast. We analyse two wetland areas situated just behind a narrow coastal sand strip: 1) the Mer Blanche and 2) the Turballe. Evidence for strong extratropical storms and /or tsunamis events can be identified in this central part of the Bay of Biscay from the XIXth to the XXth century. Nine short sediment cores were collected in August 2016 using gravity type corer of 10 inner diameter and 100 cm length. Each core was longitudinally sliced, each half section photographed and described. High-resolution elemental analyses of split sediment cores were done using an Avaatech XRF core scanner. Then sediment cores were sampled every 0.5 cm. Grain size analysis was done using a Malvern 2600 laser beam grain sizer; organic carbon was measured by Leco induction furnace. 137Cs, 210Pb and 226Ra activities were measured on about 2 g dried sediment using a low background, well-type γ spectrometer (Canberra). The 210Pb in excess, which is used for dating, was calculated as the difference of measured 210Pb and of its supported activities (226Ra). The history information is performed using historical documents including narrative sources, ancient maps, records of cities repairs, surveys conducted after a disaster, newspaper from different departmental and national archives, and meteorological data. Coastal depositional environments were affected hardest by extreme environmental and climatological events during the last century. In the Mer Blanche core, three extreme episodes can be observed: i) at 36 cm, sediment is characterized by coarser sand and higher Sr/Al ratio, this episode coincides with a high tidal wave in spring 1937; ii) at 55 cm, we observe the presence of many gravels, they dates back to the high tidal wave of 1924 and iii) at 65 cm, the presence of another coarse pebble layer is attributed to a series of severe storms associated with coastal flooding episodes between 1910 and 1913. Acknowledgements The authors gratefully acknowledge Isabelle Billy (EPOC, University of Bordeaux 1) for XRF spectrometric core scanner analysis. This work was supported by grants from the Fondation de France through the research program « Quels littoraux pour demain? » and OR2C PDL regional framework.

Fungal alteration of organic coatings on sand grains

NASA Astrophysics Data System (ADS)

Rothhardt, S.; Gleixner, G.; Benzerara, K.; Fischer, C.; Gaupp, R.

2012-04-01

We studied the fungal alteration of organically coated sand particles, sampled in Eocene sediments in the open cast mining Profen, near Leipzig (Germany). These organic coatings were formed on sand grains after their sedimentation owing to mobilization of organic matter from younger coal layers. The organic coatings formed non-continuous layers on quartz grains, measuring few micrometers up to 30 µm in thickness. It has been shown that organic coatings on sand grains retain efficiently dissolved metals by adsorption from groundwaters. They consequently might be used as adsorbent to purify low heavy metal contaminated water. However, their stability has not been assessed yet especially in the oxic environment and, more specifically, in the presence of microorganisms. This is important in order to evaluate whether coated sands could act as a reliable tool in remediation. In order to address this question we characterized the fungal alteration of organic coatings on sand grains using several techniques, including scanning electron microscopy (SEM), scanning transmission X-ray microscopy (STXM) and vertical scanning interferometry (VSI). Sand grains coated with organics were incubated on complex yeast medium with and without Schizophyllum commune to estimate changes in heavy metal retention. Formation of biominerals and etch pits is induced by fungal colonization as shown by SEM. Surface topography analysis was performed using VSI technique. Etch pit depth ranges from 0.5 to 1 µm. Pit formation is limited to the organic coating; dissolution of quartz grains was not detected. Using STXM we measured near-edge X-ray absorption fine structure (NEXAFS) spectra at the C K-edge, N-edge, and O K-edge to characterize the different organic compartments (fungi, genuine organic coatings, altered organic coatings) down to the 25-nm scale. We observed in the spectra measured at the C K-edge on the altered organic coatings a decrease in aromatic and phenolic groups as well as an enrichment in amide-rich molecules compared to the genuine organic coatings. Our results suggest heterogeneous biodegradation of organic coatings on sand grains by fungal exudation. An important implication might be the overall decrease in metal retention potential of organically coated sand grains owing to the alteration processes by S. commune.

Penetration of different human pathogenic viruses into sand columns percolated with distilled water, groundwater, or wastewater.

PubMed Central

Dizer, H; Nasser, A; Lopez, J M

1984-01-01

The adsorption of several enteroviruses and rotavirus SA11 to sand from an aquifer in the Federal Republic of Germany was estimated in sand-filled columns loaded with ca. 10(7) PFU and run at a velocity of 2.5 m/day for 12 h. After either distilled water, groundwater, secondary effluent, or tertiary effluent was percolated, the sand core was slowly extruded out of the column and cut in 1-cm slices. The slices were eluted with nutrient broth, and the amount of viruses in the broth was estimated. The best adsorption was promoted by groundwater and tertiary effluent, followed by distilled water and secondary effluent. Similar experiments, carried out at different percolation rates, indicated that a 50-day underground stay of recharged water probably suffices to eliminate viruses in the groundwater-recharged tertiary effluent. However, when viruses and sand were incubated in the presence of the surfactants sodium dodecyl sulfate, nonyl phenol, dodigen 226, or alkylbenzylsulfonate, the adsorption of the viruses was substantially diminished. Experiments in the presence of nonyl phenol seem to indicate that hydrophobic interactions are involved in the adsorption of viruses to sand. PMID:6324676

Core Across the San Andreas Fault at SAFOD - Photographs, Physical Properties Data, and Core-Handling Procedures

NASA Astrophysics Data System (ADS)

Kirschner, D. L.; Carpenter, B.; Keenan, T.; Sandusky, E.; Sone, H.; Ellsworth, B.; Hickman, S.; Weiland, C.; Zoback, M.

2007-12-01

Core samples were obtained that cross three faults of the San Andreas Fault Zone north of Parkfield, California, during the summer of 2007. The cored intervals were obtained by sidetracking off the SAFOD Main Hole that was rotary drilled across the San Andreas in 2005. The first cored interval targeted the pronounced lithologic boundary between the Salinian terrane and the Great Valley and Franciscan formations. Eleven meters of pebbly conglomerate (with minor amounts of fine sands and shale) were obtained from 3141 to 3152 m (measured depth, MD). The two conglomerate units are heavily fractured with many fractures having accommodated displacement. Within this cored interval, there is a ~1m zone with highly sheared, fine-grained material, possibly ultracataclasite in part. The second cored interval crosses a creeping segment of a fault that has been deforming the cemented casing of the adjacent Main Hole. This cored interval sampled the fault 100 m above a seismogenic patch of M2 repeating earthquakes. Thirteen meters of core were obtained across this fault from 3186 to 3199 m (MD). This fault, which is hosted primarily in siltstones and shales, contains a serpentinite body embedded in a highly sheared shale and serpentinite-bearing fault gouge unit. The third cored interval crosses a second creeping fault that has also been deforming the cemented casing of the Main Hole. This fault, which is the most rapidly shearing fault in the San Andreas fault zone based on casing deformation, contains multiple fine- grained clay-rich fault strands embedded in highly sheared shales and lesser deformed sandstones. Initial processing of the cores was carried out at the drill site. Each core came to the surface in 9 meter-long aluminum core barrels. These were cut into more manageable three-foot sections. The quarter-inch-thick aluminum liner of each section was cut and then split apart to reveal the 10 cm diameter cores. Depending on the fragility and porosity of the rock, the drilling fluid was removed either by washing with dilute calcium chloride brine (to approximately match the salinity of the formation fluids) or by gently scraping away drilling mud on the core surface. Once cleaned, each core section was photographed to very high resolution on a Geotek Multi- Sensor Core Logging (MSCL) system. This system was also used to determine the bulk density and magnetic susceptibility of each section. The 25 MB high-resolution photographs and the raw and processed physical properties data were then uploaded to the ICDP web server in Potsdam for public access (http://safod.icdp- online.org). The cores will be archived at the Gulf Coast Repository of the Integrated Ocean Drilling Program in College Station, TX. The MSCL photographs, physical property measurements, and other related data, such as geophysical logs, will be integrated using CoreWall, and will be on display at the meeting. All samples, data, and imagery are available to the science community.

The Halekulani Sand Channel and Makua Shelf sediment deposits: Are they a sand resource for replenishing Waikiki's beaches?

USGS Publications Warehouse

Hampton, M.A.; Fletcher, C. H.; Barry, J.H.; Lemmo, S.J.; ,

2000-01-01

The Halekulani Sand Channel and the Makua Shelf off the south shore of Oahu contain at least 1.3 million m3 of sediment that is a possible resource for nourishing degraded sections of Waikiki Beach. A sidescan sonar survey indicates continuous sediment cover within the channel and on the shelf, and samples from the top and bottom of vibracores from the channel and shelf contain from 29% to 77% of grains between 0 to 2.5 phi (1 to 0.177 mm), the size range of four samples from Waikiki Beach. Compositional analyses indicate high variability, but the vibracore samples normally have relatively high Halimeda content compared to beach sand samples. Laboratory tests show a positive correlation of abrasion with Halimeda content, suggesting that the offshore sediment would abrade more than beach sediment under nearshore wave action. The common gray color of the offshore sediment can be aesthetically undesirable for sand on popular tourist beaches such as Waikiki; however, visual observation of native beach sand indicates that a significant component of gray color is endemic to many Hawaiian beaches. The gray color was removed in the laboratory by soaking in heated hydrogen peroxide. The geological properties of the offshore sediment indicate potential as a resource for beach nourishment, but industrial treatment might be necessary to remove excess fine and coarse grains, and possibly the gray color. Further, the abrasion potential might have to be considered in calculating beach sand losses over time.

LeMMINGs - I. The eMERLIN legacy survey of nearby galaxies. 1.5-GHz parsec-scale radio structures and cores

NASA Astrophysics Data System (ADS)

Baldi, R. D.; Williams, D. R. A.; McHardy, I. M.; Beswick, R. J.; Argo, M. K.; Dullo, B. T.; Knapen, J. H.; Brinks, E.; Muxlow, T. W. B.; Aalto, S.; Alberdi, A.; Bendo, G. J.; Corbel, S.; Evans, R.; Fenech, D. M.; Green, D. A.; Klöckner, H.-R.; Körding, E.; Kharb, P.; Maccarone, T. J.; Martí-Vidal, I.; Mundell, C. G.; Panessa, F.; Peck, A. B.; Pérez-Torres, M. A.; Saikia, D. J.; Saikia, P.; Shankar, F.; Spencer, R. E.; Stevens, I. R.; Uttley, P.; Westcott, J.

2018-05-01

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H II galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H II galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s-1: LINERs and H II galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ˜107 M⊙, but a break emerges at lower masses. Using [O III] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H II galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H II galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

Geophysical characterization of the Lollie Levee near Conway, Arkansas, using capacitively coupled resistivity, coring, and direct push logging

USGS Publications Warehouse

Gillip, Jonathan A.; Payne, Jason

2011-01-01

A geophysical characterization of Lollie Levee near Conway, Arkansas, was conducted in February 2011. A capacitively coupled resistivity survey (using Geometric's OhmMapper) was completed along the top and toe of the 6.7-mile levee. Two-dimensional inversions were conducted on the geophysical data. As a quality-control measure, cores and direct push logs were taken at approximately 1-mile intervals along the levee. The capacitively coupled resistivity survey, the coring, and the direct push logs were used to characterize the geologic materials. Comparison of the cores and the direct push log data, along with published resistivity values, indicates that resistivity values of 200 Ohm-meters or greater represent relatively clean sand, with decreasing resistivity values occurring with increasing silt and clay content. The cores indicated that the levee is composed of a heterogeneous mixture of sand, silt, and clay. The capacitively coupled resistivity sections confirm that the levee is composed of a heterogeneous mixture of high and low resistivity materials and show that the composition of the levee varies spatially. The geologic materials underlying the levee vary spatially as a result of the geologic processes that deposited them. In general, the naturally deposited geologic materials underlying the levee contain a greater amount of low resistivity materials in the southern extent of the levee.

Characterizing Drainage Multiphase Flow in Heterogeneous Sandstones

NASA Astrophysics Data System (ADS)

Jackson, Samuel J.; Agada, Simeon; Reynolds, Catriona A.; Krevor, Samuel

2018-04-01

In this work, we analyze the characterization of drainage multiphase flow properties on heterogeneous rock cores using a rich experimental data set and mm-m scale numerical simulations. Along with routine multiphase flow properties, 3-D submeter scale capillary pressure heterogeneity is characterized by combining experimental observations and numerical calibration, resulting in a 3-D numerical model of the rock core. The uniqueness and predictive capability of the numerical models are evaluated by accurately predicting the experimentally measured relative permeability of N2—DI water and CO2—brine systems in two distinct sandstone rock cores across multiple fractional flow regimes and total flow rates. The numerical models are used to derive equivalent relative permeabilities, which are upscaled functions incorporating the effects of submeter scale capillary pressure. The functions are obtained across capillary numbers which span four orders of magnitude, representative of the range of flow regimes that occur in subsurface CO2 injection. Removal of experimental boundary artifacts allows the derivation of equivalent functions which are characteristic of the continuous subsurface. We also demonstrate how heterogeneities can be reorientated and restructured to efficiently estimate flow properties in rock orientations differing from the original core sample. This analysis shows how combined experimental and numerical characterization of rock samples can be used to derive equivalent flow properties from heterogeneous rocks.

Metagenomic characterization of biofilter microbial communities in a full-scale drinking water treatment plant.

PubMed

Oh, Seungdae; Hammes, Frederik; Liu, Wen-Tso

2018-01-01

Microorganisms inhabiting filtration media of a drinking water treatment plant can be beneficial, because they metabolize biodegradable organic matter from source waters and those formed during disinfection processes, leading to the production of biologically stable drinking water. However, which microbial consortia colonize filters and what metabolic capacity they possess remain to be investigated. To gain insights into these issues, we performed metagenome sequencing and analysis of microbial communities in three different filters of a full-scale drinking water treatment plant (DWTP). Filter communities were sampled from a rapid sand filter (RSF), granular activated carbon filter (GAC), and slow sand filter (SSF), and from the Schmutzdecke (SCM, a biologically active scum layer accumulated on top of SSF), respectively. Analysis of community phylogenetic structure revealed that the filter bacterial communities significantly differed from those in the source water and final effluent communities, respectively. Network analysis identified a filter-specific colonization pattern of bacterial groups. Bradyrhizobiaceae were abundant in GAC, whereas Nitrospira were enriched in the sand-associated filters (RSF, SCM, and SSF). The GAC community was enriched with functions associated with aromatics degradation, many of which were encoded by Rhizobiales (∼30% of the total GAC community). Predicting minimum generation time (MGT) of prokaryotic communities suggested that the GAC community potentially select fast-growers (<15 h of MGT) among the four filter communities, consistent with the highest dissolved organic matter removal rate by GAC. Our findings provide new insights into the community phylogenetic structure, colonization pattern, and metabolic capacity that potentially contributes to organic matter removal achieved in the biofiltration stages of the full-scale DWTP. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fate(s) of injected CO2 in a coal-bearing formation, Louisiana, Gulf Coast Basin: Chemical and isotopic tracers of microbial-brine-rock-CO2 interactions

USGS Publications Warehouse

Shelton, Jenna L.

2013-01-01

Coal beds are one of the most promising reservoirs for geologic carbon dioxide (CO₂) sequestration, as CO₂ can strongly adsorb onto organic matter and displace methane; however, little is known about the long-term fate of CO₂ sequestered in coal beds. The "2800' sand" of the Olla oil field is a coal-bearing, oil and gas-producing reservoir of the Paleocene–Eocene Wilcox Group in north-central Louisiana. In the 1980s, this field, specifically the 2800' sand, was flooded with CO₂ in an enhanced oil recovery (EOR) project, with 9.0×10⁷m³ of CO₂ remaining in the 2800' sand after injection ceased. This study utilized isotopic and geochemical tracers from co-produced natural gas, oil and brine from reservoirs located stratigraphically above, below and within the 2800' sand to determine the fate of the remaining EOR-CO₂, examining the possibilities of CO₂ migration, dissolution, mineral trapping, gas-phase trapping, and sorption to coal beds, while also testing a previous hypothesis that EOR-CO₂ may have been converted by microbes (CO₂-reducing methanogens) into methane, creating a microbial "hotspot". Reservoirs stratigraphically-comparable to the 2800' sand, but located in adjacent oil fields across a 90-km transect were sampled to investigate regional trends in gas composition, brine chemistry and microbial activity. The source field for the EOR-CO₂, the Black Lake Field, was also sampled to establish the δ¹³C-CO₂ value of the injected gas (0.9‰ +/- 0.9‰). Four samples collected from the Olla 2800' sand produced CO₂-rich gas with δ¹³C-CO₂ values (average 9.9‰) much lower than average (pre-injection) conditions (+15.9‰, average of sands located stratigraphically below the 2800' sand in the Olla Field) and at much higher CO₂ concentrations (24.9 mole %) than average (7.6 mole %, average of sands located stratigraphically below the 2800' sand in the Olla Field), suggesting the presence of EOR-CO₂ and gas-phase trapping as a major storage mechanism. Using δ¹³C values of CO₂ and dissolved organic carbon (DIC), CO₂ dissolution was also shown to be a major storage mechanism for 3 of the 4 samples from the Olla 2800' sand. Minor storage mechanisms were shown to be migration, which only affected 2 samples (from 1 well), and some EOR-CO₂ conversion to microbial methane for 3 of the 4 Olla 2800' sand samples. Since methanogenesis was not shown to be a major storage mechanism for the EOR-CO₂ in the Olla Field (CO₂ injection did not stimulate methanogenesis), samples were examined from adjacent oil fields to determine the cause of the Olla microbial "hot-spot". Microbial methane was found in all oil fields sampled, but indicators of methanogenesis (e.g. alkalinity, high δ¹³C-DIC values) were the greatest in the Olla Field, and the environmental conditions (salinity, pH, temperature) were most ideal for microbial CO₂ reduction in the Olla field, compared to adjacent fields.

Characterization of desert sand as a sensible thermal energy storage medium

NASA Astrophysics Data System (ADS)

Diago, Miguel; Iniesta, Alberto Crespo; Delclos, Thomas; Soum-Glaude, Audrey; Shamim, Tariq; Calvet, Nicolas

2016-05-01

Desert sand from the United Arab Emirates (UAE) is considered as a possible sensible heat, thermal energy storage (TES) material. Its thermal stability, specific heat capacity and tendency to agglomerate are studied at high temperatures. The analyses show that it is possible to use desert sand as a TES material up to 800-1000 °C. Above 800 °C, weak agglomeration effects start to become significant. The samples become solid above 1000 °C. This may represent a major operating limit depending on the handling mechanism in place for the possible transport of the sand. The sand chemical composition is analyzed with the XRF and XRD techniques, which reveal the dominance of quartz and carbonates. Finally, the spectral absorptivity of the samples is measured before and after a thermal cycle, as it may be possible to use the desert sand not only as a TES material but also as a direct solar absorber.

Subaqueous Tsunami Deposits from Ohtsuchi Bay of Sanriku Coast, North Eastern Japan

NASA Astrophysics Data System (ADS)

Haraguchi, T.; Fujiwara, O.; Shimazaki, K.

2005-12-01

Holocene tsunami history was analyzed by using a drilling core obtained from the Ohtsuchi Bay on the Sanriku coast, Pacific side of NE Japan. The saw-tooth Sanriku coast line, facing the Japan Trench, is well known for repeated suffers from the historical great tsunamis. The worst tsunami damage in Japanese history, more than 20,000 fatalities, by the AD1896 Meiji Sanriku Tsunami (M 8 1/2) centered off Sanriku was recorded from this coast. However, the geological records of ancient tsunami such as tsunami deposits have been rarely reported from the Sanriku coast.Reconstruction of the pale-tsunami history including the recurrence interval is fundamental data for the tsunami disaster mitigation on the coast. The core, 24-meter long, obtained from a bay center of 10 m-deep is mainly composed of sandy mud excluding the basal gravel bed (core bottom reached SL-34 m). Sand and gravelly sand beds ranging from several to 200 cm-thick are intercalated in the core and denoted TS-22 to TS-1 in ascending order. Most of these coarse-grained beds have evidences of deposition from high-energy and density currents, basal erosion surface, rip-up clasts mixed mulluscan shells, inverse- and normal grading, and generally upward-fining sequence.Most likely origin of these event deposits is great tsunami, because the coring site is a deep and low energy bay floor isolated from major river mouth. Low sediment supply by river floods and small disturbance by wind waves at the drilling site are favorable for the preservation of tsunami deposits. Depositional ages of TS-1 to TS-22 were estimated from a depositional curve of the core based on ten 14C ages of marine shells. Recurrence interval of 13 sand and gravel beds in the lower part of the core, TS22 (ca. 7800 cal BP) to TS-10 (AD1660-1700), is 400 to 500 years.The number of event beds in the upper part of the core, deposited during the last 400 years (TS-9 to TS-1), approximates to that of historic large tsunamis recorded around the Ohtsuchi Bay (13-14 times).Remarkable differences of the recurrence intervals of event deposits between the lower and upper parts of the core reflects the change of sediment supply system and preservation potential of the event deposits.Identification of tsunami deposits from other deposits such as river flood and storm deposits is problem to be solved for reconstructing the accurate tsunami history on the Sanriku coast.

Sedimentological Properties of Natural Gas Hydrates-Bearing Sands in the Nankai Trough and Mallik Areas

NASA Astrophysics Data System (ADS)

Uchida, T.; Tsuji, T.; Waseda, A.

2009-12-01

The Nankai Trough parallels the Japanese Island, where extensive BSRs have been interpreted from seismic reflection records. High resolution seismic surveys have definitely indicated gas hydrate distributions, and drilling the MITI Nankai Trough wells in 2000 and the METI Tokai-oki to Kumano-nada wells in 2004 have revealed subsurface gas hydrate in the eastern part of Nankai Trough. In 1998 and 2002 Mallik wells were drilled at Mackenzie Delta in the Canadian Arctic that also clarified the characteristics of gas hydrate-dominant sandy layers at depths from 890 to 1110 m beneath the permafrost zone. During the field operations, the LWD and wire-line well log data were continuously obtained and plenty of gas hydrate-bearing sand cores were recovered. Subsequence sedimentological and geochemical analyses performed on those core samples revealed the crucial geologic controls on the formation and preservation of natural gas hydrate in sediments. Pore-space gas hydrates reside in sandy sediments mostly filling intergranular porosity. Pore waters chloride anomalies, core temperature depression and core observations on visible gas hydrates confirm the presence of pore-space gas hydrates within moderate to thick sandy layers, typically 10 cm to a meter thick. Sediment porosities and pore-size distributions were obtained by mercury porosimetry, which indicate that porosities of gas hydrate-bearing sandy strata are approximately 45 %. According to grain size distribution curves, gas hydrate is dominant in fine- to very fine-grained sandy strata. Gas hydrate saturations are typically up to 80 % in pore volume throughout most of the hydrate-dominant sandy layers, which are estimated by well log analyses as well as pore water chloride anomalies. It is necessary for investigating subsurface fluid flow behaviors to evaluate both porosity and permeability of gas hydrate-bearing sandy sediments, and the measurements of water permeability for them indicated that highly saturated sands should have permeability of 1 x 10-15 to 5 x 10-15 m2 (1 to 5 millidarcies). Most of gas hydrates fill the intergranular pore systems of sandy layers, which are derived from the sedimentary facies such as channels and crevasse splay/levee deposits. It is remarked that those sandy strata are usually composed of arenite sands with matrix-free intergranular pore systems. Gas hydrates are less frequently found in fine-grained sediments such as siltstone and mudstone from overbank deposits. Methane gas accumulation and original pore space large enough to occur within host sediments may be required for forming highly saturated gas hydrate in pore system. The distribution of a porous and coarser-grained host rock should be one of the important factors to control the occurrence of gas hydrate, as well as physicochemical conditions. This appears to be a similar mode for conventional oil and gas accumulations, and this knowledge is important to predicting the location of other hydrate deposits and their eventual energy resource. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.

Radiometric age dating of peat cores from ombrotrophic bogs: challenges and opportunities presented by the Industrial Period

NASA Astrophysics Data System (ADS)

Shotyk, W.; Appleby, P.; Davies, L. J.; Froese, D. G.; Magnan, G.; Mullan-Boudreau, G.; Noernberg, T.; Bob, S.; van Bellen, S.; Zaccone, C.

2016-12-01

The upper layers of ombrotrophic (rain-fed) bogs are hydrologically isolated from surface waters and groundwaters and, in consequence, contaminants are supplied exclusively from the atmosphere. Peat cores from bogs have been used to reconstruct the history of heavy metal pollution since mining and metallurgy began, but the greatest changes have taken place since the start of the Industrial Revolution which was well underway by the middle of the 19th century. Dating peat, accumulated since this time has been made possible using 210Pb (t1/2 = 22.3 yr), but the validity of the age-depth relationship obtained must always be assessed using one or more chronostratigraphic markers. The post-industrial period provides an enormous range of possible time markers including various fallout radionuclides, numerous trace metals and their isotopes, and countless organic contaminants. Most of these have not yet been explored, and will be helpful only if they are immobile in the peat column; often, their fate during chemical diagenesis in anoxic, acidic bog waters is either unknown or at least poorly understood. The atmospheric bomb pulse curve of 14C for the period since AD 1950 has proved to be particularly valuable for validating 210Pb chronologies by providing accurate dates for individual plant macrofossils. Peat cores collected in northern Alberta, surrounding open pit mines and upgraders of Athabsca Bituminous Sands, were carefully dated using 210Pb and the age-depth relationship evaluated using both 241Am and 14C. The cores nearest industry (MIL, JPH4) show that atmospheric deposition of trace metals has been declining ever since industrial-scale mining and refining began in 1967. This includes all of the potentially toxic trace elements (Ag, Cd, Pb, Sb, Tl), but also the metals known for their enrichment in bitumen (V, Ni, Mo). In fact, the surface layers of these bogs today are comparable in composition to the "cleanest" peat samples ever found in the northern hemisphere. Our findings are completely opposed to recent claims about environmental pollution by metals from mining and upgrading in this region, illustrating the importance of reliable age dates and the value of robust age-depth models.

Description and analysis of cored hydraulic fractures -- Lost Hills field, Kern County, California

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

Fast, R.E.; Murer, A.S.; Timmer, R.S.

1994-05-01

An inclined observation well was drilled in shallow (2,000 ft) Opal-A diatomite. Seven sand-propped hydraulic fractures were cored and recovered. The hydraulic fractures were found within 5[degree] of the azimuth measured with tilt meters and were tilted 15[degree] from vertical, oriented perpendicular to the formation bedding dip. Hydraulic fractures widths ranged from less than one sand grain (40/60 mesh) to 0.4 in. Scanning electron microscopy (SEM) examination of fracture faces showed no damage to the matrix from proppant embedment or compaction, and no evidence of guard residue was detected in the proppant pack or on the formation face. Fractures appearmore » to be considerably longer than modeled. Three closely spaced fractures are interpreted to be branches of a single hydraulic fracture treatment. This paper presents a description of the fractures recovered during coring in Well OO2. Findings related to fracture dimensions and orientations, fracture sources, fracture permeability measurements, and fracture characteristics (proppant embedment, presence of gel residue) are presented. Implications related to field development are discussed.« less

A new scale for disaster nursing core competencies: Development and psychometric testing.

PubMed

Al Thobaity, Abdulellah; Williams, Brett; Plummer, Virginia

2016-02-01

All nurses must have core competencies in preparing for, responding to and recovering from a disaster. In the Kingdom of Saudi Arabia (KSA), as in many other countries, disaster nursing core competencies are not fully understood and lack reliable, validated tools. Thus, it is imperative to develop a scale for exploring disaster nursing core competencies, roles and barriers in the KSA. This study's objective is to develop a valid, reliable scale that identifies and explores core competencies of disaster nursing, nurses' roles in disaster management and barriers to developing disaster nursing in the KSA. This study developed a new scale testing its validity and reliability. A principal component analysis (PCA) was used to develop and test psychometric properties of the new scale. The PCA used a purposive sample of nurses from emergency departments in two hospitals in the KSA. Participants rated 93 paper-based, self-report questionnaire items from 1 to 10 on a Likert scale. PCA using Varimax rotation was conducted to explore factors emerging from responses. The study's participants were 132 nurses (66% response rate). PCA of the 93 questionnaire items revealed 49 redundant items (which were deleted) and 3 factors with eigenvalues of >1. The remaining 44 items accounted for 77.3% of the total variance. The overall Cronbach's alpha was 0.96 for all factors: 0.98 for Factor 1, 0.92 for Factor 2 and 0.86 for Factor 3. This study provided a validated, reliable scale for exploring nurses' core competencies, nurses' roles and barriers to developing disaster nursing in the KSA. The new scale has many implications, such as for improving education, planning and curricula. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Composition of Eocene Ice-Rafted Debris, Central Arctic Ocean

NASA Astrophysics Data System (ADS)

Ramstad, C.; St. John, K.

2007-12-01

IODP Expedition 302 drilled a 400-m sediment record which contains physical evidence of ice-rafting in the Eocene and Neogene in the Arctic (Backman et al., 2006; Moran et al., 2006, St. John, in press). An increase in the terrigenous sand abundance occurs above 246 mcd (~46 Ma), with a flux similar to that in the Neogene. Higher resolution sampling in an interval of good recovery from 246-236 mcd shows evidence of cyclic input of IRD and biogenic components that fits with Milankovitch forcing at the obliquity period (Sangiorgi et al., in press). The question remains - what areas of the Arctic were ice-covered at this early stage in the Cenozoic? To address this provenance issue the composition of the terrigenous sands (250 micron fraction) in cores 55-56X is being quantified. Grains in 75 samples are being point-counted and their compositions categorized. Quartz grains are the dominant component (greater than 10,000 grains per gram), with some being hematite-stained, and there are lesser amounts of mafic minerals. No carbonate grains are identified so far in this study. Possible sources areas for Eocene IRD are the Eastern European and Russian Arctic margins. Tracking compositional variations of the IRD over the interval of cyclic deposition, should indicate whether the cyclic IRD deposition was consistently derived from one source region or multiple regions during this time.

The effect of small- and core-scale heterogeneity on the multiphase flow properties of CO2 and water in sandstones

NASA Astrophysics Data System (ADS)

Pini, R.; Benson, S. M.

2012-12-01

Capillary pressure and relative permeability functions are characteristic curves that, when coupled to the continuum-scale equations of motion, allow for a description of multiphase displacement processes in porous media. Traditionally, these properties are measured in the laboratory and are implemented into reservoir simulations to predict the behavior at the field-scale. There is an increasing awareness that detailed investigations are required to understand the role of the inherent heterogeneity of the rock samples used in the experiments on the measured multiphase properties. In fact, although a significant amount of simulation work has explored the effect of heterogeneities on Pc-kr-S relationships, very few experimental studies report on displacements with well-characterized, naturally heterogeneous media. To extend the current data set and to support these numerical findings, more laboratory data are therefore required that have been obtained under a variety of conditions and on cores from different geological settings. A direct practical implication of these studies would be the definition of a minimum scale at which heterogeneities have to be resolved, so that mathematical models would adequately capture the observed displacement patterns. Moreover, the coupling of experiments and theory will serve as a firm starting point for testing scale-up methods. In this study, results from core-flooding experiments are presented that have been carried out at representative conditions on a variety of naturally heterogeneous core samples. Results are presented from a newly developed technique that allows measuring drainage capillary pressure curves during core-flooding experiments; data have been collected at different temperature (25 and 50C), at different pressures (2 and 9MPa) and with different fluid pairs (CO2/water, N2/water and CO2/brine), thus showing the applicability of the novel technique in a wide range of interfacial tension levels. Additionally, Pc-S relationships on mm-scale subsets of the rock core have been obtained by combination with saturation measurements from X-ray CT scanning; these are of high relevance as they directly and non-destructively quantify small-scale capillary heterogeneity in these systems. The spatial variation of the capillary pressure curve is then described by means of so-called scaling factors, which are derived from scaling-laws based on the concept of similar media (such as the Leverett J-Function), and which can be related to other relevant petrophysical properties of the rock, such as porosity, permeability and grain size distribution. The role of core-scale capillary heterogeneity is investigated based on observations from a CO2/water core-flooding experiment on a rock core that possesses a heterogeneous feature of relatively simple geometry. An integrated approach is applied where these experimental results are combined with independent measurements of capillary pressure, porosity and permeability. It is shown that 3D saturation profiles obtained by X-ray CT scanning during the core-flooding experiment are essential for defining heterogeneous features and that the latter significantly affect the character of the measured relative permeability curve.

Coupling the Alkaline-Surfactant-Polymer Technology and The Gelation Technology to Maximize Oil Production

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

Malcolm Pitts; Jie Qi; Dan Wilson

2005-10-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or more efficient areal sweep efficiency for those with high permeability contrast ''thief zones''. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or those with thief zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. A priormore » fluid-fluid report discussed interaction of different gel chemical compositions and alkaline-surfactant-polymer solutions. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses. Aluminum-polyacrylamide, flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9. Chromium acetate-polyacrylamide flowing and rigid flowing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid flowing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid flowing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid flowing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. None of the gels tested appeared to alter alkaline-surfactant-polymer solution oil recovery. Total waterflood plus chemical flood oil recovery sequence recoveries were all similar. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetate gels that were stable to injection of alkaline-surfactant-polymer solutions at 72 F were stable to injection of alkaline-surfactant-polymer solutions at 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Xanthan gum-chromium acetate gels maintained gel integrity in linear corefloods after injection of an alkaline-surfactant-polymer solution at 125 F. At 175 F, Xanthan gum-chromium acetate gels were not stable either with or without subsequent alkaline-surfactant-polymer solution injection. Numerical simulation demonstrated that reducing the permeability of a high permeability zone of a reservoir with gel improved both waterflood and alkaline-surfactant-polymer flood oil recovery. A Minnelusa reservoir with both A and B sand production was simulated. A and B sands are separated by a shale layer. A sand and B sand waterflood oil recovery was improved by 196,000 bbls when a gel was placed in the B sand. A sand and B sand alkaline-surfactant-polymer flood oil recovery was improved by 596,000 bbls when a gel was placed in the B sand. Alkaline-surfactant-polymer flood oil recovery improvement over a waterflood was 392,000 bbls. Placing a gel into the B sand prior to an alkaline-surfactant-polymer flood resulted in 989,000 bbl more oil than only water injection.« less

Multi-Method Provenance Analysis of Namibian Desert Sand

NASA Astrophysics Data System (ADS)

Vermeesch, P.; Garzanti, E.

2014-12-01

Mineralogical, geochemical and geochronological provenance proxies each have their own strengths and weaknesses: a. Bulk geochemistry, framework petrography and heavy mineral compositions can differentiate between source areas characterised by different lithologies, but are sensitive to hydraulic sorting and chemical alteration. b. Detrital zircon U-Pb geochronology is insensitive to winnowing effects, but is 'blind' to lithologies devoid of zircon and cannot differentiate between first cycle and recycled sediments. c. Cosmogenic neon isotopes can be used to identify different generations of surface exposure while simultaneously tracking different magmatic sources. The challenge is then to combine these different proxies into a self consistent story, and do so in as objective a manner as possible. We here present a case study of Namibia's Namib Sand Sea and Skeleton Coast ergs, in which all the aforementioned methods have been combined using a three-way multidimensional scaling (aka INDividual Differences SCALing or INDSCAL) analysis: 1. Each of the datasets was represented by a 'dissimilarity matrix' of pairwise distances between samples. 2. The set of these matrices was fed into the INDSCAL algorithm, which produces two pieces of graphical output: the 'group configuration', which is a scatter plot or 'map' in which similar samples plot close together and dissimilar samples plot far apart, and the 'proxy weights', in which not the samples but the proxies are plotted according to the weight they attached to the 'group configuration' axes. The INDSCAL map of the Namibia dataset indicates that (a) long-shore drift of Orange River sediments dominates the coastal sediment compositions all along the Namibian coast until Angola, and (b) that light and heavy minerals tell complementary parts of the provenance story.

Separation of time scales in the HCA model for sand

NASA Astrophysics Data System (ADS)

Niemunis, Andrzej; Wichtmann, Torsten

2014-10-01

Separation of time scales is used in a high cycle accumulation (HCA) model for sand. An important difficulty of the model is the limited applicability of the Miner's rule to multiaxial cyclic loadings applied simultaneously or in a combination with monotonic loading. Another problem is the lack of simplified objective HCA formulas for geotechnical settlement problems. Possible solutions of these problems are discussed.

Pilot- and bench-scale testing of faecal indicator bacteria survival in marine beach sand near point sources

USGS Publications Warehouse

Mika, K.B.; Imamura, G.; Chang, C.; Conway, V.; Fernandez, G.; Griffith, J.F.; Kampalath, R.A.; Lee, C.M.; Lin, C.-C.; Moreno, R.; Thompson, S.; Whitman, R.L.; Jay, J.A.

2009-01-01

Aim: Factors affecting faecal indicator bacteria (FIB) and pathogen survival/persistence in sand remain largely unstudied. This work elucidates how biological and physical factors affect die-off in beach sand following sewage spills. Methods and Results: Solar disinfection with mechanical mixing was pilot-tested as a disinfection procedure after a large sewage spill in Los Angeles. Effects of solar exposure, mechanical mixing, predation and/or competition, season, and moisture were tested at bench scale. First-order decay constants for Escherichia coli ranged between -0??23 and -1??02 per day, and for enterococci between -0??5 and -1??0 per day. Desiccation was a dominant factor for E. coli but not enterococci inactivation. Effects of season were investigated through a comparison of experimental results from winter, spring, and fall. Conclusions: Moisture was the dominant factor controlling E. coli inactivation kinetics. Initial microbial community and sand temperature were also important factors. Mechanical mixing, common in beach grooming, did not consistently reduce bacterial levels. Significance and Impact of the Study: Inactivation rates are mainly dependent on moisture and high sand temperature. Chlorination was an effective disinfection treatment in sand microcosms inoculated with raw influent. ?? 2009 The Society for Applied Microbiology.

Mecoprop (MCPP) removal in full-scale rapid sand filters at a groundwater-based waterworks.

PubMed

Hedegaard, Mathilde J; Arvin, Erik; Corfitzen, Charlotte B; Albrechtsen, Hans-Jørgen

2014-11-15

Contamination by the herbicide mecoprop (MCPP) was detected in groundwater abstraction wells at Kerteminde Waterworks in concentrations up to 0.08μg/L. MCPP was removed to below detection limit in a simple treatment line where anaerobic groundwater was aerated and subsequently filtered by primary and secondary rapid sand filters. Water quality parameters were measured throughout the waterworks, and they behaved as designed for. MCPP was removed in secondary rapid sand filters--removal was the greatest in the sand filters in the filter line with the highest contact time (63 min). In these secondary sand filters, MCPP concentration decreased from 0.037 μg/L to below the detection limit of 0.01 μg/L. MCPP was removed continuously at different filter depths (0.80 m). Additionally, biodegradation, mineralisation and adsorption were investigated in the laboratory in order to elucidate removal mechanisms in the full-scale system. Therefore, microcosms were set up with filter sand, water and (14)C-labelled MCPP at an initial concentration of 0.2 μg/L. After 24 h, 79-86% of the initial concentration of MCPP was removed. Sorption removed 11-15%, while the remaining part was removed by microbial processes, leading to a complete mineralisation of 13-18%. Microbial removal in the filter sand was similar at different depths of the rapid sand filter, while the amount of MCPP which adsorbed to the filter sand after 48 h decreased with depth from 21% of the initial MCPP in the top layer to 7% in the bottom layer. It was concluded that MCPP was removed in secondary rapid sand filters at Kerteminde Waterworks, to which both adsorption and microbial degradation contributed. Copyright © 2014 Elsevier B.V. All rights reserved.

Assessment of offshore New Jersey sources of Beach replenishment sand by diversified application of geologic and geophysical methods

USGS Publications Warehouse

Waldner, J.S.; Hall, D.W.; Uptegrove, J.; Sheridan, R.E.; Ashley, G.M.; Esker, D.

1999-01-01

Beach replenishment serves the dual purpose of maintaining a source of tourism and recreation while protecting life and property. For New Jersey, sources for beach sand supply are increasingly found offshore. To meet present and future needs, geologic and geophysical techniques can be used to improve the identification, volume estimation, and determination of suitability, thereby making the mining and managing of this resource more effective. Current research has improved both data collection and interpretation of seismic surveys and vibracore analysis for projects investigating sand ridges offshore of New Jersey. The New Jersey Geological Survey in cooperation with Rutgers University is evaluating the capabilities of digital seismic data (in addition to analog data) to analyze sand ridges. The printing density of analog systems limits the dynamic range to about 24 dB. Digital acquisition systems with dynamic ranges above 100 dB can permit enhanced seismic profiles by trace static correction, deconvolution, automatic gain scaling, horizontal stacking and digital filtering. Problems common to analog data, such as wave-motion effects of surface sources, water-bottom reverberation, and bubble-pulse-width can be addressed by processing. More than 160 line miles of digital high-resolution continuous profiling seismic data have been collected at sand ridges off Avalon, Beach Haven, and Barnegat Inlet. Digital multichannel data collection has recently been employed to map sand resources within the Port of New York/New Jersey expanded dredge-spoil site located 3 mi offshore of Sandy Hook, New Jersey. Multichannel data processing can reduce multiples, improve signal-to-noise calculations, enable source deconvolution, and generate sediment acoustic velocities and acoustic impedance analysis. Synthetic seismograms based on empirical relationships among grain size distribution, density, and velocity from vibracores are used to calculate proxy values for density and velocity. The seismograms are then correlated to the digital seismic profile to confirm reflected events. They are particularly useful where individual reflection events cannot be detected but a waveform generated by several thin lithologic units can be recognized. Progress in application of geologic and geophysical methods provides advantages in detailed sediment analysis and volumetric estimation of offshore sand ridges. New techniques for current and ongoing beach replenishment projects not only expand our knowledge of the geologic processes involved in sand ridge origin and development, but also improve our assessment of these valuable resources. These reconnaissance studies provide extensive data to the engineer regarding the suitability and quantity of sand and can optimize placement and analysis of vibracore samples.Beach replenishment serves the dual purpose of maintaining a source of tourism and recreation while protecting life and property. Research has improved both data collection and interpretation of seismic surveys and vibracore analysis for projects investigating sand ridges offshore of New Jersey. The New Jersey Geological Survey in cooperation with Rutgers University is evaluating the capabilities of digital seismic data to analyze sand ridges. The printing density of analog systems limits the dynamic range to about 24 dB. Digital acquisition systems with dynamic ranges about 100 dB can permit enhanced seismic profiles by trace static correction, deconvolution, automatic gain scaling, horizontal stacking and digital filtering.

Intrawave sand suspension in the shoaling and surf zone of a field-scale laboratory beach

NASA Astrophysics Data System (ADS)

Brinkkemper, J. A.; de Bakker, A. T. M.; Ruessink, B. G.

2017-01-01

Short-wave sand transport in morphodynamic models is often based solely on the near-bed wave-orbital motion, thereby neglecting the effect of ripple-induced and surface-induced turbulence on sand transport processes. Here sand stirring was studied using measurements of the wave-orbital motion, turbulence, ripple characteristics, and sand concentration collected on a field-scale laboratory beach under conditions ranging from irregular nonbreaking waves above vortex ripples to plunging waves and bores above subdued bed forms. Turbulence and sand concentration were analyzed as individual events and in a wave phase-averaged sense. The fraction of turbulence events related to suspension events is relatively high (˜50%), especially beneath plunging waves. Beneath nonbreaking waves with vortex ripples, the sand concentration close to the bed peaks right after the maximum positive wave-orbital motion and shows a marked phase lag in the vertical, although the peak in concentration at higher elevations does not shift to beyond the positive to negative flow reversal. Under plunging waves, concentration peaks beneath the wavefront without any notable phase lags in the vertical. In the inner-surf zone (bores), the sand concentration remains phase coupled to positive wave-orbital motion, but the concentration decreases with distance toward the shoreline. On the whole, our observations demonstrate that the wave-driven suspended load transport is onshore and largest beneath plunging waves, while it is small and can also be offshore beneath shoaling waves. To accurately predict wave-driven sand transport in morphodynamic models, the effect of surface-induced turbulence beneath plunging waves should thus be included.

Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Coring operations, core sedimentology, and lithostratigraphy

USGS Publications Warehouse

Rose, K.; Boswell, R.; Collett, T.

2011-01-01

In February 2007, BP Exploration (Alaska), the U.S. Department of Energy, and the U.S. Geological Survey completed the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well (Mount Elbert well) in the Milne Point Unit on the Alaska North Slope. The program achieved its primary goals of validating the pre-drill estimates of gas hydrate occurrence and thickness based on 3-D seismic interpretations and wireline log correlations and collecting a comprehensive suite of logging, coring, and pressure testing data. The upper section of the Mount Elbert well was drilled through the base of ice-bearing permafrost to a casing point of 594??m (1950??ft), approximately 15??m (50??ft) above the top of the targeted reservoir interval. The lower portion of the well was continuously cored from 606??m (1987??ft) to 760??m (2494??ft) and drilled to a total depth of 914??m. Ice-bearing permafrost extends to a depth of roughly 536??m and the base of gas hydrate stability is interpreted to extend to a depth of 870??m. Coring through the targeted gas hydrate bearing reservoirs was completed using a wireline-retrievable system. The coring program achieved 85% recovery of 7.6??cm (3??in) diameter core through 154??m (504??ft) of the hole. An onsite team processed the cores, collecting and preserving approximately 250 sub-samples for analyses of pore water geochemistry, microbiology, gas chemistry, petrophysical analysis, and thermal and physical properties. Eleven samples were immediately transferred to either methane-charged pressure vessels or liquid nitrogen for future study of the preserved gas hydrate. Additional offsite sampling, analyses, and detailed description of the cores were also conducted. Based on this work, one lithostratigraphic unit with eight subunits was identified across the cored interval. Subunits II and Va comprise the majority of the reservoir facies and are dominantly very fine to fine, moderately sorted, quartz, feldspar, and lithic fragment-bearing to -rich sands. Lithostratigraphic and palynologic data indicate that this section is most likely early Eocene to late Paleocene in age. The examined units contain evidence for both marine and non-marine lithofacies, and indications that the depositional environment for the reservoir facies may have been shallower marine than originally interpreted based on pre-drill wireline log interpretations. There is also evidence of reduced salinity marine conditions during deposition that may be related to the paleo-climate and depositional conditions during the early Eocene. ?? 2010.

Long term evolution and internal architecture of high-energy banner ridges of Mer d'Iroise (Western Brittany, France) : interplay of sea-level, basement morphology, biogenic productivity and hydrodynamics

NASA Astrophysics Data System (ADS)

Le Roy, P., Sr.; Le Dantec, N.; Franzetti, M.; Delacourt, C.; Ehrhold, A.

2016-12-01

The recent completion of a coupled seismic and swath bathymetric survey, conducted across the Mer d'Iroise (Atlantic continental shelf, France), provided new data for the study of the long term evolution of deep tidal sand ridges. Three major banner sand ridges composed of biogenic sands were investigated: the Banc du Four, the Haut Fond d'Ouessant and the Banc d'Ar Men. Seismic interpretation reveals a compound internal architecture of these sand ridges with a sedimentary core forming the lower units interpreted to be shoreface deposits and overlain by sandwaves. Sandwave climbing, which combines progradation and accretion, is the major process controlling the growth of the ridges. The elevation of the preserved dune foresets reaches values of about 20 to 30 m and indicate a combination of giant dunes characterized by numerous steep (up to 20°) clinoforms corresponding to a high-energy depositional environment. All of the radiocarbon ages of the biogenic surficial deposits of the Banc du Four range from 10,036 to 2,748 cal years B.P. and suggest it has grown during the last sea-level rise. The apparent absence of recent surface deposits could be caused by a change in benthic biogenic productivity or the non-conservation of recent deposits. The multiphase accretion of the ridge is closely linked to the progressive flooding of the coastal promontories and straits that structured the igneous basement. A comparable evolutionary scheme is observed for the Haut-Fond d'Ouessant where a counter-clock wise migration of dunes characterizes the surface of the ridge. In contrast, the Banc d'Ar Men located above a regular basement displays a simpler structure with a consistent Northwestward migration of steep clinoforms. Therefore, the sand ridges of the Mer d'Iroise should be thought of as a representative example of large-scale high-energy banner banks controlled by interaction of sea-level, basement morphology, biogenic productivity, tidal and wave hydrodynamics.

Impacts of Vegetation and Development on the Morphology of Coastal Sand Dunes Using Modern Geospatial Techniques: Jockey's Ridge Case Study

NASA Astrophysics Data System (ADS)

Weaver, K.; Mitasova, H.; Overton, M.

2011-12-01

LiDAR surveys acquired in the years 2007 and 2008, combined with previous LiDAR, topographic mapping and aerial imagery collected along the Outer Banks of North Carolina were used for comprehensive geospatial analysis of the largest sand dune on the eastern coast of the United States, Jockey's Ridge. The objective of the analysis was to evaluate whether the dune's evolution has continued as hypothesized in previous studies and whether an increase of development and vegetation has contributed to the dune's stabilization and overall loss of dune height. Geospatial analysis of the dune system evolution (1974 - 2008) was performed using time series of digital elevation models at one meter resolution. Image processing was conducted in order to analyze land cover change (1932 - 2009) using unsupervised classification to extract vegetation, development and sand in and around Jockey's Ridge State Park. The dune system evolution was then characterized using feature-based and raster-based metrics, including vertical and horizontal change of dune peaks, horizontal migration of dune crests, slip face geometry transformation and volume change analysis using the core and dynamic layer concept. Based on the evolutionary data studied, the volume of sand at Jockey's Ridge is consistent throughout time, composed of a stable core and a dynamically migrating layer that is not gaining or losing sand. Although the peak elevation of the Main Dune has decreased from 43m in 1953 to 22m in 2008, the analysis has shown that the sand is redistributed within the dune field. Today, the dune field peaks are increasing in elevation, and all of the dunes within the system are stabilizing at similar heights of 20-22m along with transformation of the dunes from unvegetated, crescentic to vegetated, parabolic dunes. The overall land cover trend indicates that since the 1930s vegetation and development have gradually increased over time, influencing the morphology of the dune field by stabilizing the area of sand that once fed the dunes, limiting aeolian sand transport and migration of the dune system. Not only are vegetation and development increasing around the Jockey's Ridge State Park, but vegetation is increasing inside the park boundaries with the majority of growth along the windward side of the dune system, blocking sand from feeding the dunes. Vegetation growth is also found to increase in front of the dune field, recently causing the migration of the dune to slow down.

Soil variability and landscape history of the last 800.000 years revealed by the horsification of the landscape in North-Brabant, The Netherlands

NASA Astrophysics Data System (ADS)

Kluiving, Sjoerd; Kok, Marielle; van Suijlekom, Jan-Jaap; Kasse, Kees

2015-04-01

In the province of North-Brabant in the southern Netherlands a diverse geological substrate is present variable in chronology, sediment properties, and soil profiles. The human influence on soil quality and topography has a history of millennia while new developments related to the horsification of the landscape in this region allow an insight in the soil patterns with associated landscape evolution. The objective in this project is to show that records of soils and landscape in this area are able to demonstrate the evolutional history and disseminate the pedological and geological knowledge to a wider audience in demonstrating that soil records and associated landscape evolution reveal a regional identity that can be very useful to apply in landscape architectural projects, such as in the horsification of the landscape. Soil records show landscape evolution has progressed in three distinct phases: 1) The oldest deposits in the region are formed by river sediments that reflect a fluvial environment that was present 800.000 years ago in the Lower-Pleistocene. Old courses of the rivers Rhine and Meuse deposited gravelly white sands and clay layers that have a distinct effect on hydrological properties. 2) Eolian sands dating from the Late Glacial, deposited 12.000-14.000 years before present were deposited by western wind directions, obvious from large scale linear and parabolic dune ridges. These sandy deposits have endured soil acidification and podzolisation resulting in classic Umbric Podzol profiles testifying of a prolonged period of landscape evolution. 3) Tree removal in the Holocene by man created unprotected open sand plains that were eroded and deposited by wind processes in small scale ridges with steep slopes up till approximately 500 years ago. These drift sands have a widespread occurrence and can be recognized in thin micro-podzol profiles in association with a distinct morphology of steep sloped dunes. Multiple soil horizons reflect different time periods elapsed and specific 'open landscape' environments, as these thin podzolic horizons testify. Future research will involve cartographic mapping by soil coring, as well as OSL dating, next to an ecological field reconnaissance. In this poster we will show how the soil in this region beholds an entire landscape history, and how that information can be combined with nature development in landscape architectural plans.

Influence of PPCPs on the performance of intermittently operated slow sand filters for household water purification.

PubMed

Pompei, Caroline M E; Ciric, Lena; Canales, Melisa; Karu, Kersti; Vieira, Eny M; Campos, Luiza C

2017-03-01

Removal of pharmaceuticals and personal care products (PPCPs) from drinking water is usually enhanced by advanced oxidation which is not affordable in low income countries. Slow sand filtration has been found to be capable of removing anti-inflammatory compounds, and its low maintenance costs and easy operation make it an attractive technology for treating drinking water in many parts of the world. In addition, slow sand filters can be used at both large and household scales. The biofilm (i.e. schmutzdecke) developed on the top of the sand and within the upper layers of the sand is acknowledged to be responsible for the water purification. However, it is possible that the PPCPs may affect the schmutzdecke development and microbial community within the filters, and consequently the performance of the filter. This study investigated two household slow sand filters (for water purification) operated intermittently with and without contamination by six PPCPs. Eleven parameters were monitored in the affluent and effluent water, including bacterial species present and schmutzdecke biomass development. Results demonstrated that the household slow sand filter performance was not affected by the 2μgL -1 of PPCPs in the water. There was no significant difference between filters for total coliforms and E. coli removal, but there was considerable difference between sampling times. Biomass considerably increased with the number of filtrations in both filters and there was no significant difference between filter biomass. However, it was found that more bacterial species were present in the period with no contamination than during the contamination period. Bacillus anthracis and Exiguobacterium sp. showed to be resistant to the effects of the PPCPs. These suggest there are effects of PPCPs on bacterial species within the filter. However, the effect of the PPCPs on biomass was not conclusive in this study and needs to be further investigated. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparison of Radiocarbon Ages of Sediments, Plants, and Shells From Coastal Lakes in North Florida

NASA Astrophysics Data System (ADS)

Wang, Y.; Das, O.; Liu, J.; Xu, X.; Roy, R.; Donoghue, J. F.; Means, G. H.

2017-12-01

Coastal lakes sediments are valuable archives of paleo-hurricanes and environmental changes during the late Quaternary provided that they can be accurately dated. Here, we report new radiocarbon (14C) dates derived from various organic and inorganic substrates, including bulk sediment organic matter, plants, shells, particulate organic matter (POM) and dissolved organic matter (DOM), from three coastal lakes in Florida, and compare these ages to evaluate the "reservoir effect" on 14C dating of both organic and inorganic carbon in these lakes. Bulk sediment organic matter yielded consistently older 14C ages than contemporaneous plants and shell fragments, indicating significant radiocarbon deficiencies in sedimentary organic matter in these coastal lakes, caused by influx of old organic carbon from terrestrial sources (such as soils and ancient peat deposits) in the watershed. Several reversals are observed in the 14C ages of bulk sediment organic matter in sediment cores from these lakes, indicating that input of aged organic matter from terrestrial sources into these lakes can vary considerably over time. DOM and POM samples collected at different times also yielded variable 14C signatures, further confirming the temporal variability in the contribution of old organic carbon from terrestrial sources to the lakes. The 14C age discrepancy between bulk sediment organic matter and co-occurring plant fragments or shells varies from less than one hundred years to nearly three thousand years in sediment cores examined in this study. The results show that 14C ages obtained from bulk sediment organic matter in these coastal lakes are unreliable. Analyses of both modern and fossil shells from one of the lakes suggest that the 14C reservoir effect on inorganic carbon in the lake is small and thus freshwater shells (if preserved in the sediment cores) may serve as a good substrate for 14C dating in the absence of plant fragments. However, unidentifiable shell fragments, especially those associated with sand pockets (or sand layers), in coastal lake sediment cores are not suitable for 14C dating as they are likely of marine origin and affected by significant marine 14C reservoir effect.

Maia Mapper: high definition XRF imaging in the lab

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

Ryan, Chris G.; Kirkham, R.; Moorhead, G. F.

Here, Maia Mapper is a laboratory μXRF mapping system for efficient elemental imaging of drill core sections serving minerals research and industrial applications. It targets intermediate spatial scales, with imaging of up to ~80 M pixels over a 500×150 mm 2 sample area. It brings together (i) the Maia detector and imaging system, with its large solid-angle, event-mode operation, millisecond pixel transit times in fly-scan mode and real-time spectral deconvolution and imaging, (ii) the high brightness MetalJet D2 liquid metal micro-focus X-ray source from Excillum, and (iii) an efficient XOS polycapillary lens with a flux gain ~15,900 at 21 keVmore » into a ~32 μm focus, and (iv) a sample scanning stage engineered for standard drill-core sections. Count-rates up to ~3 M/s are observed on drill core samples with low dead-time up to ~1.5%. Automated scans are executed in sequence with display of deconvoluted element component images accumulated in real-time in the Maia detector. Application images on drill core and polished rock slabs illustrate Maia Mapper capabilities as part of the analytical workflow of the Advanced Resource Characterisation Facility, which spans spatial dimensions from ore deposit to atomic scales.« less

Maia Mapper: high definition XRF imaging in the lab

DOE PAGES

Ryan, Chris G.; Kirkham, R.; Moorhead, G. F.; ...

2018-03-13

Here, Maia Mapper is a laboratory μXRF mapping system for efficient elemental imaging of drill core sections serving minerals research and industrial applications. It targets intermediate spatial scales, with imaging of up to ~80 M pixels over a 500×150 mm 2 sample area. It brings together (i) the Maia detector and imaging system, with its large solid-angle, event-mode operation, millisecond pixel transit times in fly-scan mode and real-time spectral deconvolution and imaging, (ii) the high brightness MetalJet D2 liquid metal micro-focus X-ray source from Excillum, and (iii) an efficient XOS polycapillary lens with a flux gain ~15,900 at 21 keVmore » into a ~32 μm focus, and (iv) a sample scanning stage engineered for standard drill-core sections. Count-rates up to ~3 M/s are observed on drill core samples with low dead-time up to ~1.5%. Automated scans are executed in sequence with display of deconvoluted element component images accumulated in real-time in the Maia detector. Application images on drill core and polished rock slabs illustrate Maia Mapper capabilities as part of the analytical workflow of the Advanced Resource Characterisation Facility, which spans spatial dimensions from ore deposit to atomic scales.« less

Maia Mapper: high definition XRF imaging in the lab

NASA Astrophysics Data System (ADS)

Ryan, C. G.; Kirkham, R.; Moorhead, G. F.; Parry, D.; Jensen, M.; Faulks, A.; Hogan, S.; Dunn, P. A.; Dodanwela, R.; Fisher, L. A.; Pearce, M.; Siddons, D. P.; Kuczewski, A.; Lundström, U.; Trolliet, A.; Gao, N.

2018-03-01

Maia Mapper is a laboratory μXRF mapping system for efficient elemental imaging of drill core sections serving minerals research and industrial applications. It targets intermediate spatial scales, with imaging of up to ~80 M pixels over a 500×150 mm2 sample area. It brings together (i) the Maia detector and imaging system, with its large solid-angle, event-mode operation, millisecond pixel transit times in fly-scan mode and real-time spectral deconvolution and imaging, (ii) the high brightness MetalJet D2 liquid metal micro-focus X-ray source from Excillum, and (iii) an efficient XOS polycapillary lens with a flux gain ~15,900 at 21 keV into a ~32 μm focus, and (iv) a sample scanning stage engineered for standard drill-core sections. Count-rates up to ~3 M/s are observed on drill core samples with low dead-time up to ~1.5%. Automated scans are executed in sequence with display of deconvoluted element component images accumulated in real-time in the Maia detector. Application images on drill core and polished rock slabs illustrate Maia Mapper capabilities as part of the analytical workflow of the Advanced Resource Characterisation Facility, which spans spatial dimensions from ore deposit to atomic scales.

Characterization of natural puya sand extract of Central Kalimantan by using X-Ray Diffraction

NASA Astrophysics Data System (ADS)

Suastika, K. G.; Karelius, K.; Sudyana, I. N.

2018-03-01

Start Zircon sand extraction in this study use natural sand material from Kereng Pangi village of Central Kalimantan, also known as Puya sand. There are only three ways to extract the Puya sand. The first is magnetic separation, the second is immersion in HCl, and the third is reaction with NaOH. In addition, sample of each extraction step is analyzed with X-Ray Diffraction (XRD). Then based on the quantitative analysis using X'Pert Highscore Plus software, the samples are identified mostly as zircon (ZrSiO4) and silica (SiO2). Moreover, after the immersion process with HCl, the silica compound goes down and the zircon compound climbs to 74%. In the reaction process with NaOH zircon compound content further to increase to 88%.

Experimental Investigation on Dilation Mechanisms of Land-Facies Karamay Oil Sand Reservoirs under Water Injection

NASA Astrophysics Data System (ADS)

Lin, Botao; Jin, Yan; Pang, Huiwen; Cerato, Amy B.

2016-04-01

The success of steam-assisted gravity drainage (SAGD) is strongly dependent on the formation of a homogeneous and highly permeable zone in the land-facies Karamay oil sand reservoirs. To accomplish this, hydraulic fracturing is applied through controlled water injection to a pair of horizontal wells to create a dilation zone between the dual wells. The mechanical response of the reservoirs during this injection process, however, has remained unclear for the land-facies oil sand that has a loosely packed structure. This research conducted triaxial, permeability and scanning electron microscopy (SEM) tests on the field-collected oil sand samples. The tests evaluated the influences of the field temperature, confining stress and injection pressure on the dilation mechanisms as shear dilation and tensile parting during injection. To account for petrophysical heterogeneity, five reservoir rocks including regular oil sand, mud-rich oil sand, bitumen-rich oil sand, mudstone and sandstone were investigated. It was found that the permeability evolution in the oil sand samples subjected to shear dilation closely followed the porosity and microcrack evolutions in the shear bands. In contrast, the mudstone and sandstone samples developed distinct shear planes, which formed preferred permeation paths. Tensile parting expanded the pore space and increased the permeability of all the samples in various degrees. Based on this analysis, it is concluded that the range of injection propagation in the pay zone determines the overall quality of hydraulic fracturing, while the injection pressure must be carefully controlled. A region in a reservoir has little dilation upon injection if it remains unsaturated. Moreover, a cooling of the injected water can strengthen the dilation potential of a reservoir. Finally, it is suggested that the numerical modeling of water injection in the Karamay oil sand reservoirs must take into account the volumetric plastic strain in hydrostatic loading.

Gravel Mobility in a High Sand Content Riverbed

NASA Astrophysics Data System (ADS)

Haschenburger, J. K.

2017-12-01

In sand-gravel channels, sand may modify gravel transport by changing conditions of entrainment and promoting longer displacements or gravel may inhibit sand transport if concentrated into distinct deposits, which restrict sand supply with consequences for migrating bedform size or form. This study reports on gravel mobility in the lower San Antonio River, Texas, where gravel content in the bed material ranges from about 1% to more than 20%. Sediment transport observations were collected at three U.S. Geological Survey gauging stations by deploying a Helley-Smith sampler with a 0.2 mm mesh bag from which transport rates and mobile grain sizes were determined. The flow rates sampled translate into an annual exceedance expectation from 0.2% to 98%. Gravel transport rates are generally two orders of magnitude smaller than the rates of sand transport. However, the finest gravels are transported at rates on the same order of magnitude as the coarsest sands. At all sites, the 2 and 2.8 mm fractions are transported at the lowest flow rate sampled, suggesting mobility for at least 38% to as much as 98% of the year. Fractions as large as 8 mm are mobilized at flow rates that are expected between 25% and 53% of the year. The largest fractions captured in the sampling (16 to 32 mm) require flows closer to bankfull conditions that occur no more than 0.8% of the year. Results document that some gravel sizes can be frequently transported in low gradient riverbeds with high sand content.

Iron sand - ZnO based materials of natural origin for dye decolorization under sunlight irradiation

NASA Astrophysics Data System (ADS)

Salprima Yudha, S.; Angasa, Eka; Fitriani, Dyah; Falahudin, Aswin

2017-03-01

A mixed iron sand - ZnO materials was prepared by heating a mixture of natural iron sand and ZnO at 900 °C for 5 hours. XRD study of the sample revealed that, in the mixed iron sand - ZnO present some minor peaks that similar with XRD pattern of γ-Fe2O3 and/or Fe3O4. Observation of the sample using SEM, showed a compact morpholgy and almost homogenenous in particles size. In purpose to evaluate the ability of this materials for textile dying wastewater treatment, a study on rhodamine B decolorization was carried out as a reperesentative.

Sand effects on thermal barrier coatings for gas turbine engines

NASA Astrophysics Data System (ADS)

Walock, Michael; Barnett, Blake; Ghoshal, Anindya; Murugan, Muthuvel; Swab, Jeffrey; Pepi, Marc; Hopkins, David; Gazonas, George; Kerner, Kevin

Accumulation and infiltration of molten/ semi-molten sand and subsequent formation of calcia-magnesia-alumina-silicate (CMAS) deposits in gas turbine engines continues to be a significant problem for aviation assets. This complex problem is compounded by the large variations in the composition, size, and topology of natural sands, gas generator turbine temperatures, thermal barrier coating properties, and the incoming particulate's momentum. In order to simplify the materials testing process, significant time and resources have been spent in the development of synthetic sand mixtures. However, there is debate whether these mixtures accurately mimic the damage observed in field-returned engines. With this study, we provide a direct comparison of CMAS deposits from both natural and synthetic sands. Using spray deposition techniques, 7% yttria-stabilized zirconia coatings are deposited onto bond-coated, Ni-superalloy discs. Each sample is coated with a sand slurry, either natural or synthetic, and exposed to a high temperature flame for 1 hour. Test samples are characterized before and after flame exposure. In addition, the test samples will be compared to field-returned equipment. This research was sponsored by the US Army Research Laboratory, and was accomplished under Cooperative Agreement # W911NF-12-2-0019.

An automated full waveform logging system for high-resolution P-wave profiles in marine sediments

NASA Astrophysics Data System (ADS)

Breitzke, Monika; Spieβ, Volkhard

1993-11-01

An automated, PC-based logging system has been developed to investigate marine sediment cores by full waveform transmission seismograms. High-resolution P-wave velocity and amplitude attenuation profiles are simultaneously derived from the transmission data to characterize the acoustic properties of the sediment column. A pair of ultrasonic, piezoelectric wheel probes is used to generate and record the transmission signals travelling radially through the sediment core. Both unsplit and split cores are allowed. Mounted in a carriage driven by a stepping motor via a shaft the probes automatically move along the core liner, stopping at equidistant spacings to provide a quasi-continuous inspection of the core by the transmission data. The axial travel distance and the core diameter are determined by digital measuring tools. First arrivals are picked automatically from the transmission seismograms using either a threshold in the seismogram's envelope or a cross-correlation algorithm taking the ‘zero-offset’ signal of both wheel probes into account. Combined with the core diameter these first arrivals lead to a P-wave velocity profile with a relative precision of 1 to 2 m s-1. Simultaneously, the maximum peak-to-peak amplitudes of the transmission seismograms are evaluated to get a first idea on the amplitude attenuation along the sediment core. Two examples of gravity cores taken during a recent cruise of R.V. METEOR in the Western Equatorial Atlantic are presented. They yield that the P-wave profiles can be used for locating strong and fine-scale lithological changes, e.g. turbidite layers and slight variations in the sand, silt or clay content. In addition, the transmission seismograms and their amplitude spectra obviously seem to reveal a correlation between the relative amount of low-frequency spectral components and the sediment grain size, and thus provide a tool for the determination of additional, related physical or sedimentological parameters in future investigations.

Sedimentology and geochemistry of mud volcanoes in the Anaximander Mountain Region from the Eastern Mediterranean Sea.

PubMed

Talas, Ezgi; Duman, Muhammet; Küçüksezgin, Filiz; Brennan, Michael L; Raineault, Nicole A

2015-06-15

Investigations carried out on surface sediments collected from the Anaximander mud volcanoes in the Eastern Mediterranean Sea to determine sedimentary and geochemical properties. The sediment grain size distribution and geochemical contents were determined by grain size analysis, organic carbon, carbonate contents and element analysis. The results of element contents were compared to background levels of Earth's crust. The factors that affect element distribution in sediments were calculated by the nine push core samples taken from the surface of mud volcanoes by the E/V Nautilus. The grain size of the samples varies from sand to sandy silt. Enrichment and Contamination factor analysis showed that these analyses can also be used to evaluate of deep sea environmental and source parameters. It is concluded that the biological and cold seep effects are the main drivers of surface sediment characteristics from the Anaximander mud volcanoes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Description of gravity cores from San Pablo Bay and Carquinez Strait, San Francisco Bay, California

USGS Publications Warehouse

Woodrow, Donald L.; John L. Chin,; Wong, Florence L.; Fregoso, Theresa A.; Jaffe, Bruce E.

2017-06-27

Seventy-two gravity cores were collected by the U.S. Geological Survey in 1990, 1991, and 2000 from San Pablo Bay and Carquinez Strait, California. The gravity cores collected within San Pablo Bay contain bioturbated laminated silts and sandy clays, whole and broken bivalve shells (mostly mussels), fossil tube structures, and fine-grained plant or wood fragments. Gravity cores from the channel wall of Carquinez Strait east of San Pablo Bay consist of sand and clay layers, whole and broken bivalve shells (less than in San Pablo Bay), trace fossil tubes, and minute fragments of plant material.

Prediction of Liquefaction Potential of Dredge Fill Sand by DCP and Dynamic Probing

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

Alam, Md. Jahangir; Azad, Abul Kalam; Rahman, Ziaur

2008-07-08

From many research it is proved that liquefaction potential of sand is function of mainly relative density and confining pressure. During routine site investigations, high-quality sampling and laboratory testing of sands are not feasible because of inevitable sample disturbance effects and budgetary constraints. On the other hand quality control of sand fill can be done by determining in situ density of sand in layer by layer which is expensive and time consuming. In this paper TRL DCP (Transportation Research Laboratory Dynamic Cone Penetration) and DPL (Dynamic Probing Light) are calibrated to predict the relative density of sand deposit. For thismore » purpose sand of known relative density is prepared in a calibration chamber which is a mild steel cylinder with diameter 0.5 m and height 1.0 m. Relative density of sand is varied by controlling height of fall and diameter of hole of sand discharge bowl. After filling, every time DPL and DCP tests are performed and for every blow the penetration of cone is recorded. N10 is then calculated from penetration records. Thus a database is compiled where N10 and relative densities are known. A correlation is made between N{sub 10} and relative density for two types of sand. A good correlation of N{sub 10} and relative density is found.« less

Trajectories of saltating sand particles behind a porous fence

NASA Astrophysics Data System (ADS)

Zhang, Ning; Lee, Sang Joon; Chen, Ting-Guo

2015-01-01

Trajectories of aeolian sand particles behind a porous wind fence embedded in a simulated atmospheric boundary layer were visualized experimentally, to investigate the shelter effect of the fence on sand saltation. Two sand samples, one collected from a beach (d = 250 μm) and the other from a desert (d = 100 μm), were tested in comparison with the previous studies of a 'no-fence' case. A wind fence (ε = 38.5%) was installed on a flat sand bed filled with each sand sample. A high-speed photography technique and the particle tracking velocimetry (PTV) method were employed to reconstruct the trajectories of particles saltating behind the fence. The collision processes of these sand particles were analyzed, momentum and kinetic energy transfer between saltating particles and ground surface were also investigated. In the wake region, probability density distributions of the impact velocities agree well with the pattern of no-fence case, and can be explained by a log-normal law. The horizontal component of impact velocity for the beach sand is decreased by about 54%, and about 76% for the desert sand. Vertical restitution coefficients of bouncing particles are smaller than 1.0 due to the presence of the wind fence. The saltating particles lose a large proportion of their energy during the collision process. These results illustrate that the porous wind fence effectively abates the further evolution of saltating sand particles.

Near coast sedimentary stratigraphy as a proxy for climatic instability

NASA Astrophysics Data System (ADS)

McLivenny, J.

2009-04-01

Several studies have indicated a link between climatic deterioration and dune stability (Wilson 2002, Issar 2003, Dawson et al 2004). The frequency and magnitude of storms have been cited as a key variable in the stability of large dune systems. For the stratigraphy of dune systems to act as a regional climatic proxy there must be a good regional relationship between known climatic events and regionally correlated stratigraphic changes. Dunnet Bay in Caithness, Northern Scotland was chosen as a study site to look at the relationship between dune stability and climatic change during the late Holocene in Northern Scotland. Dunnet Bay was chosen for its physical attributes which make it an excellent natural sediment trap. Tucked in between headlands which act as barriers to long-shore transport the predominant movement of sediment there is straight onshore, with only minor amounts being lost to the sea. The immediate back-dune stratigraphy, colloquially known as "links", provided evidence of peat formation and dune stability. Stratigraphy was mapped using traditional field techniques and ground penetrating radar. The cores consisted mostly of massive layers of sand interleaved with peat. Sand layers were dated with optically stimulated luminescence (OSL) and interpreted as reflecting high wind energy regimes transporting sand inland. Peat layers were C14 dated and taken as representing climatic stability. Stratigraphy was mapped using hand auguring, percussion coring, and open sections. Ground penetrating radar was also used to look at the continuity of key layers. OSL dating in two open sections showed dates obtained from the first section (1790 AD ±70, 53 BC ± 100, 300 BC ± 100, 400 BC ± 100) mapped to the top of the second section (1800 AD ± 100, 1500 BC ± 200, 2900 BC ± 300) which was consistent with stratigraphy increasing sediment thickness towards the centre of the bay. The results were consistent with acquired C14 dates from selected peat layers. Taken collectively the results are consistent with some known episodes of climatic instability which occurred during the mid Holocene with instability phases occurring in Dunnet from approximately 6300- 4250 yrs BP, associated with climatic deterioration between 6000 - 5,200 Yrs BP (Lamb 1995) and dune instability between 2560 - 3900 Yrs BP, associated with an abrupt change of climate (Anderson 1995) In addition to the luminescence dates, 31 luminescence profiling dates were acquired in order to look at the continuity of the age vs. depth profile. Luminescence profile dates are small samples that require less preparation prior to luminescence measurement than full luminescence dating. Although larger errors are associated with luminescence profiling, it offered means of identifying at lesser cost the possible occurrence of mixing between eroded layers. The stratigraphic chronology was compared to other local and regional dune studies and periods of climatic deterioration found in other proxies. The GISP2 ice core (Greenland Ice Sheet Project) was found to provide chemical proxies for North Atlantic storminess which partially explained our observed stratigraphy (O`brien et al 1995). It is concluded that changes in dune stability at a regional scale are also influenced by local variables, so that one should be careful when attempting to draw stratigraphy to climate change. Key References: Issar, A. (2003) Climate changes during the Holocene and their impact on hydrological systems. Published by the Cambridge University Press 2003. Wilson, P. (2002) Holocene coastal dune development on the South Erridale peninsula, Wester Ross, Scotland. Scottish Journal of Geology, 38, 1, 5-13. Dawson, S., smith, D., Jordan, J., and Dawson D. G. (2004) Late Holocene coastal sand movements in the outer Hebrides N. W. Scotland. Marine Geology 210, 281-306 O`Brien, S. M. Mayewski, P.A. Meeker, L. D., Meese, D. A., Twickler, M. S. & Whitlow, S. I. (1995) Complexity of the Holocene Climate as reconstructed from a Greenland ice core. Science 270, pp 1962-1964 Lamb, H. (1995) Climate, History and the Modern World. Published by Routledge ISBN 0415127343, 9780415127349 2nd ed. Anderson, D. E. (1995) An abrupt mid-Holocene decline of pinus sylvestris in Glen Torridon, north west Scotland: Implications for paleoclimatic change. School of Geography and the Environment Research papers, Oxford

Dynamic passive pressure on abutments and pile caps.

DOT National Transportation Integrated Search

2010-08-01

This study investigated the lateral load response of a full-scale pile cap with nine different backfill conditions, more specifically being: 1) no backfill present (baseline response), 2) densely compacted clean sand, 3) loosely compacted clean sand,...

Onset and Dynamics of a Subaqueous Dune Field in a Tideless Erosional Deltaic Shoreface: an Analog for the Initial Development of Sand Ridges

NASA Astrophysics Data System (ADS)

Guerrero, Q.; Guillén, J.; Durán, R.; Urgeles, R.

2016-12-01

A subaqueous dune field located over a retreating deltaic lobe in the Ebro delta (NW Mediterranean) is morphodynamically characterized by analyzing three sets of co-located, multibeam bathymetric data acquired in 2004, 2013 and 2015, measurements of near-bottom currents and suspended sediment concentrations, high-resolution seismic profiles and aerial photographs. The dunes, made of fine sand, extend from 5 to 15 m water depth, have straight crestlines and maximum heights and wavelengths of 2.5 and 350 m, respectively (Fig. 1). Results suggest that the onset of dune field development is closely related to the contemporary evolution of the Ebro delta. A change in the main river channel in the 1940s led to the progressive abandonment of the former river mouth, severe coastal retreatment ( 37 m·y-1) and increased sediment availability. The characteristic NW winds of the region induce near-bottom currents flowing towards the SE which are able to rework and transport these sediments. The dune field developed over the shoreface of the abandoned river mouth and is currently active with mean SE migration rates of 10 m·y-1, most likely when high-energetic currents occur. The morphology of the dune field and crestline obliquity to shoreline orientation agree well with that observed in sand ridges of continental shelves worldwide. Mid-outer shelf sand ridges have been interpreted as sedimentary bodies formed in coastal waters and detached from the coast during sea level rise. The studied dune field could therefore be an example of the initial stages of sand ridges development when large amounts of sand are suddenly available. The field developed when the river mouth switched, favored by a pre-existing seafloor irregularity. Despite the time-scale for the genesis and evolution of shoreface sand ridges has been set in time-scales of hundreds/thousands of years, this study shows that shoreface sand ridges can develop during shorter time-scales (tens of years). Furthermore, it is discussed that, in absence of a rapid sea level rise, these sand ridges probably will vanish as a consequence of sediment scarcity and wave reworking.

An investigation of the kinetic processes influencing mercury emissions from sand and soil samples of varying thickness.

PubMed

Quinones, Jason L; Carpi, Anthony

2011-01-01

Mercury flux from HgCl2-treated sand and untreated soil samples of varying thickness (0.5-15 mm) were measured in dark and light under a Teflon dynamic flux chamber. Mean emissions over a 5.5-d sampling period showed an increase with depth for sand samples between 0.5 and 2 mm, but increasing depth above 2 mm had no effect. First-order kinetic models showed strong goodness of fit to the data and explained a high degree ofvariability in the emissions profile of all sand samples (R = 0.70-0.98). Soil samples showed an initial emissions peak that was not correlated with depth, suggesting a very shallow process at work. However, longer-term "baseline" emissions, measured as mean emissions between days 4.5 and 5.5, did show a relationship with depth. First-order kinetic models showed good fit for soil samples up to 4 mm thick (R2 = 0.66-0.91); however, thicker samples did not show a consistent fit to first- or second-order kinetic models (1 degree R2 = 0.00-0.46; 2 degree R2 = 0.00-0.54). The data suggest that mercury emissions from soil samples may follow a multicomponent model for which more

Thermal Equation of State of Iron: Constraint on the Density Deficit of Earth's Core

NASA Astrophysics Data System (ADS)

Fei, Y.; Murphy, C. A.; Shibazaki, Y.; Huang, H.

2013-12-01

The seismically inferred densities of Earth's solid inner core and the liquid outer core are smaller than the measured densities of solid hcp-iron and liquid iron, respectively. The inner core density deficit is significantly smaller than the outer core density deficit, implying different amounts and/or identities of light-elements incorporated in the inner and outer cores. Accurate measurements of the thermal equation-of-state of iron over a wide pressure and temperature range are required to precisely quantify the core density deficits, which are essential for developing a quantitative composition model for the core. The challenge has been evaluating the experimental uncertainties related to the choice of pressure scales and the sample environment, such as hydrostaticity at multi-megabar pressures and extreme temperatures. We have conducted high-pressure experiments on iron in MgO, NaCl, and Ne pressure media and obtained in-situ X-ray diffraction data up to 200 GPa at room temperature. Using inter-calibrated pressure scales including the MgO, NaCl, Ne, and Pt scales, we have produced a consistent compression curve of hcp-Fe at room temperature. We have also performed laser-heated diamond-anvil cell experiments on both Fe and Pt in a Ne pressure medium. The experiment was designed to quantitatively compare the thermal expansion of Fe and Pt in the same sample environment using Ne as the pressure medium. The thermal expansion data of hcp-Fe at high pressure were derived based on the thermal equation of state of Pt. Using the 300-K isothermal compression curve of iron derived from our static experiments as a constraint, we have developed a thermal equation of state of hcp-Fe that is consistent with the static P-V-T data of iron and also reproduces the shock wave Hugoniot data for pure iron. The thermodynamic model, based on both static and dynamic data, is further used to calculate the density and bulk sound velocity of liquid iron. Our results define the solid inner core and liquid outer core density deficits, which can serve as the basis for any core composition models.

New River Dam Foundation Report. Gila River Basin: Phoenix, Arizona and Vicinity (Including New River).

DTIC Science & Technology

1985-10-01

further downstream before merging with the Agua Fria River. 6 Site Geology 2.08 The geological formations present within the project area consist...sampling and in- situ density testing using the sand displacement 11 or large-scale water displacement method. Dozer trenches TT82-1 and TT82-6 were excavated...underlying the valley or may, due to its pervasiveness, represent an in situ weathering product of the buried bedrock. 4.18 Because of the magnitude

Changes in carbon stability and microbial activity in size fractions of micro-aggregates in a rice soil chronosequence under long term rice cultivation

NASA Astrophysics Data System (ADS)

Pan, Genxing; Liu, Yalong; Wang, Ping; Li, Lianqinfg; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Bian, Rongjun; Ding, Yuanjun; Ma, Chong

2016-04-01

Recent studies have shown soil carbon sequestration through physical protection of relative labile carbon intra micro-aggregates with formation of large sized macro-aggregates under good management of soil and agricultural systems. While carbon stabilization had been increasingly concerned as ecosystem properties, the mechanisms underspin bioactivity of soil carbon with increased carbon stability has been still poorly understood. In this study, topsoil samples were collected from rice soils derived from salt marsh under different length of rice cultivation up to 700 years from eastern China. Particle size fractions (PSF) of soil aggregates were separated using a low energy dispersion protocol. Carbon fractions in the PSFs were analyzed either with FTIR spectroscopy. Soil microbial community of bacterial, fungal and archaeal were analyzed with molecular fingerprinting using specific gene primers. Soil respiration and carbon gain from amended maize as well as enzyme activities were measured using lab incubation protocols. While the PSFs were dominated by the fine sand (200-20μm) and silt fraction (20-2μm), the mass proportion both of sand (2000-200μm) and clay (<2μm) fraction increased with prolonged rice cultivation, giving rise to an increasing trend of mean weight diameter of soil aggregates (also referred to aggregate stability). Soil organic carbon was found most enriched in coarse sand fraction (40-60g/kg), followed by the clay fraction (20-24.5g/kg), but depleted in the silt fraction (~10g/kg). Phenolic and aromatic carbon as recalcitrant pool were high (33-40% of total SOC) in both coarse sand and clay fractions than in both fine sand and silt fractions (20-29% of total SOC). However, the ratio of LOC/total SOC showed a weak decreasing trend with decreasing size of the aggregate fractions. Total gene content in the size fractions followed a similar trend to that of SOC. Bacterial and archaeal gene abundance was concentrated in both sand and clay fractions but that of fungi in sand fraction, and sharply decreased with the decreasing size of aggregate fraction. Gene abundance of archaeal followed a similar trend to that of bacterial but showing an increasing trend with prolonged rice cultivation in both sand and clay fractions. Change in community diversity with sizes of aggregate fractions was found of fungi and weakly of bacterial but not of archaeal. Soil respiration ratio (Respired CO2-C to SOC) was highest in silt fraction, followed by the fine sand fraction but lowest in sand and clay fractions in the rice soils cultivated over 100 years. Again, scaled by total gen concentration, respiration was higher in silt fraction than in other fractions for these rice soils. For the size fractions other than clay fraction, soil gene concentration, Archaeal gen abundance, normalized enzyme activity and carbon sequestration was seen increased but SOC- and gene- scaled soil respiration decreased, more or less with prolonged rice cultivation. As shown with regression analysis, SOC content was positively linearly correlated to recalcitrant carbon proportion but negatively linearly correlated to labile carbon, in both sand and clay fractions. However, soil respiration was found positively logarithmically correlated to total DNA contents and bacterial gen abundance in both sand and clay fractions. Total DNA content was found positively correlated to SOC and labile carbon content, recalcitrant carbon proportion and normalized enzyme activity but negatively to soil respiration, in sand fraction only. Our findings suggested that carbon accumulation and stabilization was prevalent in both sand and clay fraction, only the coarse sand fraction was found responsible for bioactivity dynamics in the rice soils. Thus, soil carbon sequestration was primarily by formation of the macro-aggregates, which again mediated carbon stability and bioactivity in the rice soils under long term rice cultivation.

Characterization of reactive flow-induced evolution of carbonate rocks using digital core analysis- part 1: Assessment of pore-scale mineral dissolution and deposition.

PubMed

Qajar, Jafar; Arns, Christoph H

2016-09-01

The application of X-ray micro-computed tomography (μ-CT) for quantitatively characterizing reactive-flow induced pore structure evolution including local particle detachment, displacement and deposition in carbonate rocks is investigated. In the studies conducted in this field of research, the experimental procedure has involved alternating steps of imaging and ex-situ core sample alteration. Practically, it is impossible to return the sample, with micron precision, to the same position and orientation. Furthermore, successive images of a sample in pre- and post-alteration states are usually taken at different conditions such as different scales, resolutions and signal-to-noise ratios. These conditions accompanying with subresolution features in the images make voxel-by-voxel comparisons of successive images problematic. In this paper, we first address the respective challenges in voxel-wise interpretation of successive images of carbonate rocks subject to reactive flow. Reactive coreflood in two carbonate cores with different rock types are considered. For the first rock, we used the experimental and imaging results published by Qajar et al. (2013) which showed a quasi-uniform dissolution regime. A similar reactive core flood was conducted in the second rock which resulted in wormhole-like dissolution regime. We particularly examine the major image processing operations such as transformation of images to the same grey-scale, noise filtering and segmentation thresholding and propose quantitative methods to evaluate the effectiveness of these operations in voxel-wise analysis of successive images of a sample. In the second part, we generalize the methodology based on the three-phase segmentation of normalized images, microporosity assignment and 2D histogram of image intensities to estimate grey-scale changes of individual image voxels for a general case where the greyscale images are segmented into arbitrary number of phases. The results show that local (voxel-based) porosity changes can be decomposed into local mineral dissolution and deposition. Moreover, it is found that the microporosity evolutions are differently distributed in the samples after the reactive coreflood experiments. In the last part of the paper, for the case of quasi-uniform dissolution, we combine the tomographic images with numerical calculations of permeability along the core to characterize the relationship between changes in permeability and the fractions of the mineral dissolved and deposited. A consistency is found between the calculated longitudinal permeability changes and the quantified distribution of mineral dissolved and deposited along the sample. Copyright © 2016 Elsevier B.V. All rights reserved.

Characterization of reactive flow-induced evolution of carbonate rocks using digital core analysis- part 1: Assessment of pore-scale mineral dissolution and deposition

NASA Astrophysics Data System (ADS)

Qajar, Jafar; Arns, Christoph H.

2016-09-01

The application of X-ray micro-computed tomography (μ-CT) for quantitatively characterizing reactive-flow induced pore structure evolution including local particle detachment, displacement and deposition in carbonate rocks is investigated. In the studies conducted in this field of research, the experimental procedure has involved alternating steps of imaging and ex-situ core sample alteration. Practically, it is impossible to return the sample, with micron precision, to the same position and orientation. Furthermore, successive images of a sample in pre- and post-alteration states are usually taken at different conditions such as different scales, resolutions and signal-to-noise ratios. These conditions accompanying with subresolution features in the images make voxel-by-voxel comparisons of successive images problematic. In this paper, we first address the respective challenges in voxel-wise interpretation of successive images of carbonate rocks subject to reactive flow. Reactive coreflood in two carbonate cores with different rock types are considered. For the first rock, we used the experimental and imaging results published by Qajar et al. (2013) which showed a quasi-uniform dissolution regime. A similar reactive core flood was conducted in the second rock which resulted in wormhole-like dissolution regime. We particularly examine the major image processing operations such as transformation of images to the same grey-scale, noise filtering and segmentation thresholding and propose quantitative methods to evaluate the effectiveness of these operations in voxel-wise analysis of successive images of a sample. In the second part, we generalize the methodology based on the three-phase segmentation of normalized images, microporosity assignment and 2D histogram of image intensities to estimate grey-scale changes of individual image voxels for a general case where the greyscale images are segmented into arbitrary number of phases. The results show that local (voxel-based) porosity changes can be decomposed into local mineral dissolution and deposition. Moreover, it is found that the microporosity evolutions are differently distributed in the samples after the reactive coreflood experiments. In the last part of the paper, for the case of quasi-uniform dissolution, we combine the tomographic images with numerical calculations of permeability along the core to characterize the relationship between changes in permeability and the fractions of the mineral dissolved and deposited. A consistency is found between the calculated longitudinal permeability changes and the quantified distribution of mineral dissolved and deposited along the sample.

Aeolian sand transport and aeolian deposits on Venus: A review

NASA Astrophysics Data System (ADS)

Kreslavsly, Mikhail A.; Bondarenko, Nataliya V.

2017-06-01

We review the current state of knowledge about aeolian sand transport and aeolian bedforms on planet Venus. This knowledge is limited by lack of observational data. Among the four planetary bodies of the Solar System with sufficient atmospheres in contact with solid surfaces, Venus has the densest atmosphere; the conditions there are transitional between those for terrestrial subaerial and subaqueous transport. The dense atmosphere causes low saltation threshold and short characteristic saltation length, and short scale length of the incipient dunes. A few lines of evidence indicate that the typical wind speeds exceed the saltation threshold; therefore, sand transport would be pervasive, if sand capable of saltation is available. Sand production on Venus is probably much slower than on the Earth; the major terrestrial sand sinks are also absent, however, lithification of sand through sintering is expected to be effective under Venus' conditions. Active transport is not detectable with the data available. Aeolian bedforms (transverse dunes) resolved in the currently available radar images occupy a tiny area on the planet; however, indirect observations suggest that small-scale unresolved aeolian bedforms are ubiquitous. Aeolian transport is probably limited by sand lithification causing shortage of saltation-capable material. Large impact events likely cause regional short-term spikes in aeolian transport by supplying a large amount of sand-size particles, as well as disintegration and activation of older indurated sand deposits. The data available are insufficient to understand whether the global aeolian sand transport occurs or not. More robust knowledge about aeolian transport on Venus is essential for future scientific exploration of the planet, in particular, for implementation and interpretation of geochemical studies of surface materials. High-resolution orbital radar imaging with local to regional coverage and desirable interferometric capabilities is the most effective way to obtain essential new knowledge about aeolian transport on Venus.

Investigations on Local Quartz Sand for Application in Glass Industry

NASA Astrophysics Data System (ADS)

Dararutana, Pisutti; Chetanachan, Prukswan; Wathanakul, Pornsawat; Sirikulrat, Narin

2009-03-01

Silica or glass sand is a special type of quartz sand that is suitable for glass-making, because of its high silica content, and its low content of iron oxide and other compounds. In Thailand, deposits of quartz sand are found as the beach and the river sands in many areas; eastern, southern, northeastern and northern. In this work, grain-size distribution and chemical analyses were carried out on 10 sand samples taken from various localities in Thailand such as Chanthaburi, Trat, Rayong, Chumphon, Nakhon Si, Pattani, Phuket, Songkhla, Nong Khai, and Tak provinces. The geological resources show that most of them are the surface-to-near-surface glass sand deposits. The sand grains in most deposits were mainly angular-to-rounded, except in some areas of either angular or rounded grains. Chemical analysis showed that the sands contained more than 95wt% silica and low content of Fe, Al, Ca, Mg, Na, and K. The concentration levels of these components in the samples confirm with internationally acceptable standard for glass production. The quartz sand dressing plants that used the spiral classifier to improve the properties of the quartz sands to meet the standard specifications are mostly located in the eastern area. It can be concluded that most of the quartz sand deposits in Thailand investigated show well-sorted grain-size with considerable purity, i.e. high-grade quality. The advanced works resulted in that these raw quartz sands can be used as raw material for fabrication of soda-lime, lead crystal, and lead-free high refractive index glasses. The colorless and various colored glass products have been satisfactorily used in the domestic art and glass manufactures.

Development and optimization of a solid-phase microextraction gas chromatography-tandem mass spectrometry methodology to analyse ultraviolet filters in beach sand.

PubMed

Vila, Marlene; Llompart, Maria; Garcia-Jares, Carmen; Homem, Vera; Dagnac, Thierry

2018-06-06

A methodology based on solid-phase microextraction (SPME) followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) has been developed for the simultaneous analysis of eleven multiclass ultraviolet (UV) filters in beach sand. To the best of our knowledge, this is the first time that this extraction technique is applied to the analysis of UV filters in sand samples, and in other kind of environmental solid samples. Main extraction parameters such as the fibre coating, the amount of sample, the addition of salt, the volume of water added to the sand, and the temperature were optimized. An experimental design approach was implemented in order to find out the most favourable conditions. The final conditions consisted of adding 1 mL of water to 1 g of sample followed by the headspace SPME for 20 min at 100 °C, using PDMS/DVB as fibre coating. The SPME-GC-MS/MS method was validated in terms of linearity, accuracy, limits of detection and quantification, and precision. Recovery studies were also performed at three concentration levels in real Atlantic and Mediterranean sand samples. The recoveries were generally above 85% and relative standard deviations below 11%. The limits of detection were in the pg g -1 level. The validated methodology was successfully applied to the analysis of real sand samples collected from Atlantic Ocean beaches in the Northwest coast of Spain and Portugal, Canary Islands (Spain), and from Mediterranean Sea beaches in Mallorca Island (Spain). The most frequently found UV filters were ethylhexyl salicylate (EHS), homosalate (HMS), 4-methylbenzylidene camphor (4MBC), 2-ethylhexyl methoxycinnamate (2EHMC) and octocrylene (OCR), with concentrations up to 670 ng g -1 . Copyright © 2018 Elsevier B.V. All rights reserved.

Sedimentology and Permafrost Characteristics of Pingo-Like Features (PLFs) from the Beaufort Sea shelf, NWT, Canada

NASA Astrophysics Data System (ADS)

Medioli, B. E.; Dallimore, S. R.; Nixon, F. M.; Dallimore, A.; Blasco, S.; Paull, C. K.; McLaughlin, F.; Ussler, W.; Davies, E.

2004-12-01

Pingo-like features (PLFs) are rounded positive relief features commonly found on Beaufort Sea shelf, NWT. PLFs occur in water depths from 20 to 200m, are typically a few hundred meters in diameter and rise 10 to 35m above the seafloor. In the fall of 2003, an MBARI-USGS-GSC-DFO coring and geophysical study was undertaken of a number of PLFs. The crests, flanks and moats of 8 PLFs, as well as background shelf sites, were vibra-cored. Upon recovery, core temperatures of moat sediments ranged from 2.0 to -0.5 deg C and no ice bonding was observed. Sediments consisted of dark-olive-grey to black muds with shells. Sedimentary structures were rare with some finely laminated to finely-color-banded beds. Intense bioturbation, in situ marine shells and a lack of terriginous macrofossils suggest moat sediments were deposited in a shallow coastal environment. In some instances, a down core grain size coarsening was observed with higher organic content suggesting a gradational environment towards more lagoonal conditions. Core temperatures from the 8 PLFs were 0 to -1.7 deg C, significantly colder than the moat sediments. Ice-bonded permafrost was encountered within 1m of the seabed with visible ice content up to 40% by volume. Several ice-bonded intervals were preserved frozen for detailed investigation in the lab. The observed ground ice in the cores was quite unique when compared with visible ice forms commonly seen in regional terrestrial sections. The ice gave the core a vuggy texture with individual ice-filled vugs 10 to 200 mm3. Vugs were typically flattened to ovoid. When thawed, the ice produced excess water resulting in a very soft texture. In many cases the vuggy texture was maintained with sediment voids forming where the ice was. PLF crest sediments were massive silty clays with clayey silts and muddy fine sand interbeds. They generally lack sedimentary structures, although this may have been due to sediment structure loss upon thawing. The background seafloor sediments consisted of unfrozen, massive silty sands and sandy silts and were distinct from the crest and moat sediments. In several cores, a sharp transition was noted to well-sorted sands. This lower unit may represent a transgressed terrestrial sequence. Research continues to determine the origin of the PLFs and quantify the role of permafrost and ice formation.

Praying Mantis Bending Core Breakoff and Retention Mechanism

NASA Technical Reports Server (NTRS)

Badescu, Mircea; Sherrit, Stewart; Bar-Cohen, Yoseph; Bao, Xiaoqi; Lindermann, Randel A.

2011-01-01

Sampling cores requires the controlled breakoff of the core at a known location with respect to the drill end. An additional problem is designing a mechanism that can be implemented at a small scale, yet is robust and versatile enough to be used for a variety of core samples. The new design consists of a set of tubes (a drill tube, an outer tube, and an inner tube) and means of sliding the inner and outer tubes axially relative to each other. Additionally, a sample tube can be housed inside the inner tube for storing the sample. The inner tube fits inside the outer tube, which fits inside the drill tube. The inner and outer tubes can move axially relative to each other. The inner tube presents two lamellae with two opposing grabbing teeth and one pushing tooth. The pushing tooth is offset axially from the grabbing teeth. The teeth can move radially and their motion is controlled by the outer tube. The outer tube presents two lamellae with radial extrusions to control the inner tube lamellae motion. In breaking the core, the mechanism creates two support points (the grabbing teeth and the bit tip) and one push point. The core is broken in bending. The grabbing teeth can also act as a core retention mechanism. The praying mantis that is disclosed herein is an active core breaking/retention mechanism that requires only one additional actuator other than the drilling actuator. It can break cores that are attached to the borehole bottom as

The effects of Fe-oxidizing microorganisms on post-biostimulation permeability reduction and oxidative processes at the Rifle IFRC site

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

Chan, Clara Sze-Yue

2015-07-02

Fe oxidation and biomineral formation is important in aquifers because the highly-reactive oxides can control the mobility of nutrients (e.g. phosphate, C) and metals (e.g. arsenic, uranium). Mineral formation also has the potential to affect hydrology, depending on the volume and distribution in pore spaces. In this exploratory study, we sought to understand how microbial Fe-oxidizers and their biominerals affect, and are affected by groundwater flow. As part of work at the Rifle aquifer in Colorado, we initially hypothesized that Fe-oxidizers were contributing to aquifer clogging problems associated with enhanced bioremediation. To demonstrate the presence of Fe-oxidizers in the Riflemore » aquifer, we enriched FeOM from groundwater samples, and isolated two novel chemolithotrophic, microaerophilic Fe-oxidizing Betaproteobacteria, Hydrogenophaga sp. P101 and Curvibacter sp. CD03. To image cells and biominerals in the context of pores, we developed a “micro-aquifer,” a sand-filled flow-through culture chamber that allows for imaging of sediment pore space with multiphoton confocal microscopy. Fe oxide biofilms formed on sand grains, demonstrating that FeOM produce Fe oxide sand coatings. Fe coatings are common on aquifer sands, and tend to sequester contaminants; however, it has never previously been shown that microbes are responsible for their formation. In contrast to our original hypothesis, the biominerals did not clog the mini-aquifer. Instead, Fe biofilm distribution was dynamic: they grew as coatings, then periodically sloughed off sand grains, with some flocs later caught in pore throats. This has implications for physical hydrology, including pore scale architecture, and element transport. The sloughing of coatings likely prevents the biominerals from clogging wells and aquifers, at least initially. Although attached biomineral coatings sequester Fe-associated elements (e.g. P, As, C, U), when biominerals detach, these elements are transported as particles through the aquifer. Our work shows that microbial mineralization impacts in aquifers are dynamic, and that the fate and transport of biomineral-associated elements depend not only on geochemical conditions, but also physical pore-scale processes.« less

Multi-scale ecosystem monitoring: an application of scaling data to answer multiple ecological questions

USDA-ARS?s Scientific Manuscript database

Background/Question/Methods Standardized monitoring data collection efforts using a probabilistic sample design, such as in the Bureau of Land Management’s (BLM) Assessment, Inventory, and Monitoring (AIM) Strategy, provide a core suite of ecological indicators, maximize data collection efficiency,...

Lithostratigraphy and shear-wave velocity in the crystallized Topopah Spring Tuff, Yucca Mountain, Nevada

USGS Publications Warehouse

Buesch, D.C.; Stokoe, K.H.; Won, K.C.; Seong, Y.J.; Jung, J.L.; Schuhen, M.D.

2006-01-01

Evaluation of the potential future response to seismic events of the proposed spent nuclear fuel and high-level radioactive waste repository at Yucca Mountain, Nevada, is in part based on the seismic properties of the host rock, the 12.8-million-year-old Topopah Spring Tuff. Because of the processes that formed the tuff, the densely welded and crystallized part has three lithophysal and three nonlithophysal zones, and each zone has characteristic variations in lithostratigraphic features and structures of the rocks. Lithostratigraphic features include lithophysal cavities; rims on lithophysae and some fractures; spots (which are similar to rims but without an associated cavity or aperture); amounts of porosity resulting from welding, crystallization, and vapor-phase corrosion and mineralization; and fractures. Seismic properties, including shear-wave velocity (Vs), have been measured on 38 pieces of core, and there is a good "first order" correlation with the lithostratigraphic zones; for example, samples from nonlithophysal zones have larger Vs values compared to samples from lithophysal zones. Some samples have Vs values that are outside the typical range for the lithostratigraphic zone; however, these samples typically have one or more fractures, "large" lithophysal cavities, or "missing pieces" relative to the sample size. Shear-wave velocity data measured in the tunnels have similar relations to lithophysal and nonlithophysal rocks; however, tunnel-based values are typically smaller than those measured in core resulting from increased lithophysae and fracturing effects. Variations in seismic properties such as Vs data from small-scale samples (typical and "flawed" core) to larger scale transects in the tunnels provide a basis for merging our understanding of the distributions of lithostratigraphic features (and zones) with a method to scale seismic properties.

Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

USGS Publications Warehouse

Stern, Laura A.; Lorenson, T.D.; Pinkston, John C.

2011-01-01

Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA–DOE–USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5 m to 760.1 m depth, and sections investigated here were retrieved from 619.9 m and 661.0 m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70–75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20–120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas.

Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

USGS Publications Warehouse

Stern, L.A.; Lorenson, T.D.; Pinkston, J.C.

2011-01-01

Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5. m to 760.1. m depth, and sections investigated here were retrieved from 619.9. m and 661.0. m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70-75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20-120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas. ?? 2009.

Dispersal and population structure at different spatial scales in the subterranean rodent Ctenomys australis

PubMed Central

2010-01-01

Background The population genetic structure of subterranean rodent species is strongly affected by demographic (e.g. rates of dispersal and social structure) and stochastic factors (e.g. random genetic drift among subpopulations and habitat fragmentation). In particular, gene flow estimates at different spatial scales are essential to understand genetic differentiation among populations of a species living in a highly fragmented landscape. Ctenomys australis (the sand dune tuco-tuco) is a territorial subterranean rodent that inhabits a relatively secure, permanently sealed burrow system, occurring in sand dune habitats on the coastal landscape in the south-east of Buenos Aires province, Argentina. Currently, this habitat is threatened by urban development and forestry and, therefore, the survival of this endemic species is at risk. Here, we assess population genetic structure and patterns of dispersal among individuals of this species at different spatial scales using 8 polymorphic microsatellite loci. Furthermore, we evaluate the relative importance of sex and habitat configuration in modulating the dispersal patterns at these geographical scales. Results Our results show that dispersal in C. australis is not restricted at regional spatial scales (~ 4 km). Assignment tests revealed significant population substructure within the study area, providing support for the presence of two subpopulations from three original sampling sites. Finally, male-biased dispersal was found in the Western side of our study area, but in the Eastern side no apparent philopatric pattern was found, suggesting that in a more continuous habitat males might move longer distances than females. Conclusions Overall, the assignment-based approaches were able to detect population substructure at fine geographical scales. Additionally, the maintenance of a significant genetic structure at regional (~ 4 km) and small (less than 1 km) spatial scales despite apparently moderate to high levels of gene flow between local sampling sites could not be explained simply by the linear distance among them. On the whole, our results support the hypothesis that males disperse more frequently than females; however they do not provide support for strict philopatry within females. PMID:20109219

Petrophysical Effects during karstification

NASA Astrophysics Data System (ADS)

Mai, Franziska; Kirsch, Reinhard; Rücker, Carsten; Börner, Frank

2017-04-01

Sinkholes are depression or collapse structures caused by dissolution in the subsurface or subrosion processes and occur in a vast variety of geological settings. They pose a considerable threat to people's safety and can cause severe economic loss, especially in highly populated areas. Commonly, sinkholes are linked to anomalies in groundwater flow and to the heterogeneities in the soluble sediment. To develop an early recognition system of sinkhole instability, unrest and collapse it is necessary to obtain a better understanding of sinkhole generation. With this intent the joint project "SIMULTAN" studies sinkholes applying a combination of structural, geophysical, petrophysical, and hydrological mapping methods, accompanied by sensor development, and multi-scale monitoring. Studying the solution process of gypsum and limestone as well as the accompanying processes and their relation to hydrologic mechanisms from a petrophysical point of view is essential to understand geophysically detected anomalies related to sinkholes. The focus lies on measurements of the complex, frequency dependent electrical conductivity, the self potential and the travel time of elastic waves. First, systematic laboratory measurements of the complex electrical conductivity were conducted on samples consisting of unconsolidated sand. The fully saturated samples differed in the ionic composition of their pore water (e.g. calcium sulfate and/or sodium chloride). The results indicate that it is possible to detect effects of higher gypsum concentration in the ground- or pore-water using electrical conductivity. This includes both the karstificable sediments as well as the adjacent, non-soluble sediments like e.g. clean sand or shaly sand. To monitor karstification and subrosion processes on a field scale, a stationary measuring system was installed in Münsterdorf, Schleswig-Holstein in northern Germany, an area highly at risk of sinkhole development. The complex electrical conductivity is measured in two boreholes, located 5 meters apart. The results of these measurements are used to investigate possible solution of the subterranean chalk.

To See the World in a Grain of Sand: Recognizing the Origin of Sand Specimens by Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Multivariate Exploratory Data Analysis

ERIC Educational Resources Information Center

Pezzolo, Alessandra De Lorenzi

2011-01-01

The diffuse reflectance infrared Fourier transform (DRIFT) spectra of sand samples exhibit features reflecting their composition. Basic multivariate analysis (MVA) can be used to effectively sort subsets of homogeneous specimens collected from nearby locations, as well as pointing out similarities in composition among sands of different origins.…

Modeling fine-scale geological heterogeneity--examples of sand lenses in tills.

PubMed

Kessler, Timo Christian; Comunian, Alessandro; Oriani, Fabio; Renard, Philippe; Nilsson, Bertel; Klint, Knud Erik; Bjerg, Poul Løgstrup

2013-01-01

Sand lenses at various spatial scales are recognized to add heterogeneity to glacial sediments. They have high hydraulic conductivities relative to the surrounding till matrix and may affect the advective transport of water and contaminants in clayey till settings. Sand lenses were investigated on till outcrops producing binary images of geological cross-sections capturing the size, shape and distribution of individual features. Sand lenses occur as elongated, anisotropic geobodies that vary in size and extent. Besides, sand lenses show strong non-stationary patterns on section images that hamper subsequent simulation. Transition probability (TP) and multiple-point statistics (MPS) were employed to simulate sand lens heterogeneity. We used one cross-section to parameterize the spatial correlation and a second, parallel section as a reference: it allowed testing the quality of the simulations as a function of the amount of conditioning data under realistic conditions. The performance of the simulations was evaluated on the faithful reproduction of the specific geological structure caused by sand lenses. Multiple-point statistics offer a better reproduction of sand lens geometry. However, two-dimensional training images acquired by outcrop mapping are of limited use to generate three-dimensional realizations with MPS. One can use a technique that consists in splitting the 3D domain into a set of slices in various directions that are sequentially simulated and reassembled into a 3D block. The identification of flow paths through a network of elongated sand lenses and the impact on the equivalent permeability in tills are essential to perform solute transport modeling in the low-permeability sediments. © 2012, The Author(s). Groundwater © 2012, National Ground Water Association.

Stratigraphy of a proposed wind farm site southeast of Block Island: Utilization of borehole samples, downhole logging, and seismic profiles

NASA Astrophysics Data System (ADS)

Sheldon, Dane P. H.

Seismic stratigraphy, sedimentology, lithostratigraphy, downhole geophysical logging, mineralogy, and palynology were used to study and interpret the upper 70 meters of the inner continental shelf sediments within a proposed wind farm site located approximately two to three nautical miles to the southeast of Block Island, Rhode Island. Core samples and downhole logging collected from borings drilled for geotechnical purposes at proposed wind turbine sites along with seismic surveys in the surrounding area provide the data for this study. Cretaceous coastal plain sediments that consist of non-marine to marine sand, silt, and clay are found overlying bedrock at a contact depth beyond the sampling depth of this study. The upper Cretaceous sediments sampled in borings are correlated with the Magothy/Matawan formations described regionally from New Jersey to Nantucket. An unconformity formed through sub-aerial, fluvial, marine, and glacial erosion marks the upper strata of the Cretaceous sediments separating them from the overlying deposits. The majority of Quaternary deposits overlying the unconformity represent the advance, pulsing, and retreat of the Laurentide ice sheet that reached its southern terminus in the area of Block Island approximately 25,000 to 21,000 years before present. The sequence consists of a basal glacial till overlain by sediments deposited by meltwater environments ranging from deltaic to proglacial lakefloor. A late Pleistocene to early Holocene unconformity marks the top of the glacial sequence and was formed after glacial retreat through fluvial and subaerial erosion/deposition. Overlying the glacial sequence are sediments deposited during the late Pleistocene and Holocene consisting of interbedded gravel, sand, silt, and clay. Sampling of these sediments was limited and surficial reflectors in seismic profiles were masked due to a hard bottom return. However, two depositional periods are interpreted as representing fluvial and estuarine/marine environments respectively. One sample recovered at five meters contained shell fragments within a gray fine to coarse sand possibly representing a shallow estuarine to marine environment. A coarse near surface deposit described but not recovered in all borings may represent a transgressive unconformity and resulting lag deposit however due to lack of sampling and seismic resolution in the upper 5 meters, the nature of this deposit is merely speculation. In areas where depth to the glacial surface increased, sediments ranging from sand to fine-grained silt and clay were encountered in borings. In summary, the upper 70 meters of the inner continental shelf section within the study site consists of unconsolidated sediments spanning three major depositional periods. Sediments derived from glacial activity represent the bulk of samples collected. The glacial sequences represent various depositional environments, although most samples are interpreted to be the product of glacial meltwater deposition with distribution determined by source as well as highs and lows present in the antecedent topography. Finely laminated (varved) sediment to the south of Block Island indicates the presence of proglacial lakes in the area during the time of glacial retreat. Overlying sediments represent environments ranging from fluvial to marine.

Permeable reactive barrier of coarse sand-supported zero valent iron for the removal of 2,4-dichlorophenol in groundwater.

PubMed

Gao, Weichun; Zhang, Yongxiang; Zhang, Xiaoye; Duan, Zhilong; Wang, Youhao; Qin, Can; Hu, Xiao; Wang, Hao; Chang, Shan

2015-11-01

In this study, coarse sand-supported zero valent iron (ZVI) composite was synthesized by adding sodium alginate to immobilize. Composite was detected by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). SEM results showed that composite had core-shell structure and a wide porous distribution pattern. The synthesized composite was used for degradation of 2,4-dichlorophenol (2,4-DCP) contamination in groundwater. Experimental results demonstrated that degradation mechanism of 2,4-DCP using coarse sand-supported ZVI included adsorption, desorption, and dechlorination. 2,4-DCP adsorption was described as pseudo-second-order kinetic model. It was concluded that dechlorination was the key reaction pathway, ZVI and hydrogen are prime reductants in dechlorination of 2,4-DCP using ZVI.

Grain Size Biasing of 230Th-derived Focusing Factors in the Panama Basin

NASA Astrophysics Data System (ADS)

Loveley, M. R.; Marcantonio, F.; Lyle, M. W.; Ibrahim, R.; Wang, J. K.; Hertzberg, J. E.

2014-12-01

In this study, we attempt to understand how differing grain size classes in Panama Basin sediments may create biasing of 230Th as a constant-flux proxy. Greater amounts of 230Th are contained in fine grained particles, which, if fractionated from coarser grained counterparts may lead to biasing of 230Th-derived mass accumulation rates (MARs) and sediment focusing factors. We examined sediments that span the past 25 kyr from four new sediment cores retrieved from two different localities close to the ridges that bound the Panama Basin. Each locality contained paired sites that were seismically interpreted to have undergone sediment redistribution, i.e., thick focused sites versus thin winnowed sites. Two sediment cores were retrieved from the northern part of the Panama basin, Cocos Ridge, (MV1014-01-"4JC", 5° 44.7'N 85° 45.5' W, 1730 m depth; MV1014-01-"8JC", 6° 14.0'N 86° 2.6' W, 1993 m depth), and two were retrieved from the southern part of the basin, Carnegie Ridge, (MV1014-02-"11JC", 0° 41.6'S 85° 20.0' W, 2452 m depth; MV1014-02-"17JC" 0° 10.8'S 85° 52.0' W, 2846 m depth). Cores 4JC and 11JC lie closer to the ridge tops of the Cocos and Carnegie Ridges, respectively, and have thin sediment drapes, while deeper cores, 8JC (Cocos) and 17JC (Carnegie), have thicker sediment drapes and lie downslope from the ridge top cores. Age-model-derived sand MARs, which likely represent the vertical rain of particles that cannot be transported by bottom currents, are similar at each of the paired sites in Holocene and glacial time slices. However, 230Th-normalized MARs are about 50% lower, on average at each of the paired sites during the same time slices. Both Holocene and glacial samples from "thin" cores (4,11JC) contain, surprisingly, significant amounts (up to 50%) of the 230Th within the coarse grained (>63 μm) fraction which makes up 40-70% of the bulk samples analyzed. On the contrary, Holocene and glacial samples from "thick" cores, (8,17JC), contain the greatest amounts of 230Th (up to 49%) in the finest grain-sized fraction (<4μm), which makes up 26-40% of the bulk samples analyzed. Although, redistribution of sediment has taken place, our analysis indicates that 230Th-derived focusing factors are being overestimated at thick sites and underestimated at thin sites.

Measuring health-related quality of life in children with cancer living in Mainland China: feasibility, reliability and validity of the Chinese Mandarin version of PedsQL 4.0 Generic Core Scales and 3.0 Cancer Module.

PubMed

Ji, Yi; Chen, Siyuan; Li, Kai; Xiao, Nong; Yang, Xue; Zheng, Shan; Xiao, Xianmin

2011-11-23

The Pediatric Quality of Life Inventory (PedsQL) is widely used instrument to measure pediatric health-related quality of life (HRQOL) for children aged 2 to 18 years. The purpose of the current study was to investigate the feasibility, reliability and validity of the Chinese mandarin version of the PedsQL 4.0 Generic Core Scales and 3.0 Cancer Module in a group of Chinese children with cancer. The PedsQL 4.0 Genetic Core Scales and the PedsQL 3.0 Cancer Module were administered to children with cancer (aged 5-18 years) and parents of such children (aged 2-18 years). For comparison, a survey on a demographically group-matched sample of the general population with children (aged 5-18) and parents of children (aged 2-18 years) was conducted with the PedsQL 4.0 Genetic Core Scales. The minimal mean percentage of missing item responses (except the School Functioning scale) supported the feasibility of the PedsQL 4.0 Generic Core Scales and 3.0 Cancer Module for Chinese children with cancer. Most of the scales showed satisfactory reliability with Cronbach's α of exceeding 0.70, and all scales demonstrated sufficient test-retest reliability. Assessing the clinical validity of the questionnaires, statistically significant difference was found between healthy children and children with cancer, and between children on-treatment versus off-treatment ≥12 months. Positive significant correlations were observed between the scores of the PedsQL 4.0 Generic Core Scale and the PedsQL 3.0 Cancer Module. Exploratory factor analysis demonstrated sufficient factorial validity. Moderate to good agreement was found between child self- and parent proxy-reports. The findings support the feasibility, reliability and validity of the Chinese Mandarin version of PedsQL 4.0 Generic Core Scales and 3.0 Cancer Module in children with cancer living in mainland China.

Measuring health-related quality of life in children with cancer living in mainland China: feasibility, reliability and validity of the Chinese mandarin version of PedsQL 4.0 Generic Core Scales and 3.0 Cancer Module

PubMed Central

2011-01-01

Background The Pediatric Quality of Life Inventory (PedsQL) is widely used instrument to measure pediatric health-related quality of life (HRQOL) for children aged 2 to 18 years. The purpose of the current study was to investigate the feasibility, reliability and validity of the Chinese mandarin version of the PedsQL 4.0 Generic Core Scales and 3.0 Cancer Module in a group of Chinese children with cancer. Methods The PedsQL 4.0 Genetic Core Scales and the PedsQL 3.0 Cancer Module were administered to children with cancer (aged 5-18 years) and parents of such children (aged 2-18 years). For comparison, a survey on a demographically group-matched sample of the general population with children (aged 5-18) and parents of children (aged 2-18 years) was conducted with the PedsQL 4.0 Genetic Core Scales. Result The minimal mean percentage of missing item responses (except the School Functioning scale) supported the feasibility of the PedsQL 4.0 Generic Core Scales and 3.0 Cancer Module for Chinese children with cancer. Most of the scales showed satisfactory reliability with Cronbach's α of exceeding 0.70, and all scales demonstrated sufficient test-retest reliability. Assessing the clinical validity of the questionnaires, statistically significant difference was found between healthy children and children with cancer, and between children on-treatment versus off-treatment ≥12 months. Positive significant correlations were observed between the scores of the PedsQL 4.0 Generic Core Scale and the PedsQL 3.0 Cancer Module. Exploratory factor analysis demonstrated sufficient factorial validity. Moderate to good agreement was found between child self- and parent proxy-reports. Conclusion The findings support the feasibility, reliability and validity of the Chinese Mandarin version of PedsQL 4.0 Generic Core Scales and 3.0 Cancer Module in children with cancer living in mainland China. PMID:22111968

Experimental hypervelocity impact into quartz sand - Distribution and shock metamorphism of ejecta

NASA Technical Reports Server (NTRS)

Stoeffler, D.; Gault, D. E.; Wedekind, J.; Polkowski, G.

1975-01-01

Results are presented for vertical impacts of 0.3-g cylindrical plastic projectiles into noncohesive quartz sand in which vertical and horizontal reference strate were employed by using layers of colored sand. The impacts were performed at velocities of 5.9-6.9 km/sec with a vertical gun ballistic range. The craters, 30-33 cm in diameter, reveal a radial decay of the ejecta mass per unit area with a power of -2.8 to -3.5. Material displaced from the upper 15% of the crater depth d is represented within the whole ejecta blanked, material from deeper than 28% of d is deposited inside 2 crater radii, and no material from deeper than 33% of d was ejected beyond the crater rim. Shock-metamorphosed particles (glassy agglutinates, cataclastic breccias, and comminuted quartz) amount to some 4% of the total displaced mass and indicate progressive zones of decay of shock intensity from a peak pressure of 300 kbar. The shock-metamorphosed particles and the shock-induced change in the grain size distribution of ejected samples have close analogies to the basic characteristics of the lunar regolith. Possible applications to regolith formation and to ejecta formations of large-scale impact craters are discussed.

A non-invasive multiproxy approach to recognize Holocene paleocoastal environmental signals in Sri Lanka.

NASA Astrophysics Data System (ADS)

Ranasinghe, P. N.; Ortiz, J. D.; Siriwardana, C.

2009-05-01

Coastal lagoons are archives of paleocoastal environmental signatures. Lagoonal cores are extensively used to recognize paleo-sea level changes, plaeoclimatic changes, paleo-tsunami and storm deposits. Grain size, microfossil assemblages and organic carbon content are some of the common proxies used in such paleoenvironmental studies. This study attempts to use petrophysical methods to measure the physical properties of lagoonal cores to recognize paleoenvironmental signatures. Three sediment cores, each five meters in length, were collected in a 1 km long transect from a siliciclastic coastal lagoon at Kirinda, Sri Lanka. This south-eastern lagoon is highly susceptible to tsunamis and coastal flood events; The 2004 Asian tsunami generated 7-8 m waves in the area. Evidence for Holocene sea level changes are also preserved in nearby areas. Particle size, magnetic susceptibility and visible color reflectance were measured in the three cores at 1 cm resolution. Principal component analysis (PCA) was carried out with grain size (Q-mode) and reflectance data (R-mode). Log records and depth variation diagrams of grain size, reflectance factor scores, and magnetic susceptibility were compared to identify paleo-environmental signals. PCA analysis of reflectance data identified three principle components which describe 92% of the variance while a similar analysis performed for grain size data identifies six components describing 98% of the variance. Downcore variation plots show that a*, b* and the reflectance factor scores representing sediment goethite and iron oxide content have a strong correlation with grain size factors representing the medium sand, silt and clay size classes. Sand layers deposited by 2004 tsunami event and by similar older events can be clearly recognized using these parameters. Magnetic susceptibility plots also show peaks in some of the same sand layers indicating the association of magnetic mineral-rich beach sand. Downcore plots of these petrophysical parameters show a significant abrupt change in the signal at about 2 m below the surface. According to an age model constructed for a nearby lagoon by Jackson (2009) this break dates back about 6000 yrs BP. This break may represent the mid Holocene sea level transgression, which resulted in about 1.5 m sea level rise in Sri Lanka (Katupota, 1995) Correlation of multi proxy downcore variation plots from Kirinda lagoon with geomorphologically and geographically different lagoons on the eastern coast would enable distinguishing different coastal events in the Holocene history.

Magnetic Diagenesis in the Gas Hydrate System

NASA Astrophysics Data System (ADS)

Enkin, R. J.; Hamilton, T. S.; Esteban, L.

2009-05-01

Natural gas hydrate is a methane-bearing form of ice which occurs in permafrost and continental slope settings. Geochemical processes associated with gas hydrate formation lead to the growth of iron sulphides which have a geophysically measurable magnetic signature. Detailed magnetic investigation and complementary petrological observations were undertaken on unconsolidated sediments from three gas hydrate (GH) settings: permafrost in fluvial-deltaic silts and sands in the Western Canadian Arctic (Japex et al. Mallik 5L-38 in 2002); diamictons and hemipelagics in the Cascadia accretionary wedge west of Vancouver Island (IODP Exp.311 in 2006); and marine sands and hemipelagics from the Bay of Bengal (NGHP Exp.01 in 2007). These magnetic measurements provide stratigraphic profiles which reveal fine scale variations in lithology, magnetic grain size, and paleo-pore fluid geochemistry. The highest magnetic susceptibility values are observed in strata which preserve high initial concentrations of detrital magnetite, such as glacial deposits. The lowest values of magnetic susceptibility are observed where iron has been reduced to paramagnetic pyrite, formed in settings with high methane and sulphate flux such as at methane vents. Enhanced values of magnetic susceptibility characterize the introduction of the ferrimagnetic iron sulphide minerals greigite and smythite. These magnetic minerals are mostly found immediately adjacent to the sedimentary horizons which host the gas hydrate and their textures and compositions indicate rapid disequilibrium crystallization. The observed diagenesis result from the unique physical and geochemical properties of the environment where gas hydrates form: methane is available to fuel microbiological activity and the freezing which accompanied GH crystallization quickly removed pure water, froze the sediments into an impermeable solid and expelled more concentrated brines into the adjacent less permeable strata to the point of inducing fracture formation. Magnetic surveying techniques can help delineate anomalies related to gas hydrate deposits, and magnetic logging of wells and core samples provide information on the original lithology and diagenesis caused by gas hydrate formation.

Accelerated gravity testing of aquitard core permeability and implications at formation and regional scale

NASA Astrophysics Data System (ADS)

Timms, W. A.; Crane, R.; Anderson, D. J.; Bouzalakos, S.; Whelan, M.; McGeeney, D.; Rahman, P. F.; Guinea, A.; Acworth, R. I.

2015-03-01

Evaluating the possibility of leakage through low permeability geological strata is critically important for sustainable water supplies, the extraction of fuels from strata such as coal beds, and the confinement of waste within the earth. The current work demonstrates that relatively rapid and reliable hydraulic conductivity (K) measurement of aquitard cores using accelerated gravity can inform and constrain larger scale assessments of hydraulic connectivity. Steady state fluid velocity through a low K porous sample is linearly related to accelerated gravity (g-level) in a centrifuge permeameter (CP) unless consolidation or geochemical reactions occur. The CP module was custom designed to fit a standard 2 m diameter geotechnical centrifuge (550 g maximum) with a capacity for sample dimensions of 30 to 100 mm diameter and 30 to 200 mm in length, and a maximum total stress of ~2 MPa at the base of the core. Formation fluids were used as influent to limit any shrink-swell phenomena which may alter the permeability. Vertical hydraulic conductivity (Kv) results from CP testing of cores from three sites within the same regional clayey silt formation varied (10-7 to 10-9 m s-1, n = 14). Results at one of these sites (1.1 × 10-10 to 3.5 × 10-9 m s-1, n = 5) that were obtained in < 24 h were similar to in situ Kv values (3 × 10-9 m s-1) from pore pressure responses over several weeks within a 30 m clayey sequence. Core scale and in situ Kv results were compared with vertical connectivity within a regional flow model, and considered in the context of heterogeneity and preferential flow paths at site and formation scale. More reliable assessments of leakage and solute transport though aquitards over multi-decadal timescales can be achieved by accelerated core testing together with advanced geostatistical and numerical methods.

Physical properties of northern Gulf of Mexico sediment and laboratory samples containing natural and synthetic methane gas hydrate

NASA Astrophysics Data System (ADS)

Winters, W. J.; Waite, W. F.; Mason, D. H.; Lorenson, T. L.; Paull, C. K.; Novosel, I.; Boldina, O. M.; Dallimore, S. R.; Collett, T. S.; Page 127 Shipboard Sc. Party

2003-04-01

The U.S. Geological Survey (USGS) has been involved in oceanographic and Arctic field programs and laboratory studies to better understand the relationship between natural gas hydrate and physical properties of surrounding sediment. Recently, the Institut Polaire Francais, Paul-Emile Victor (IPEV) and the USGS jointly conducted a cruise aboard the Marion Dufresne to collect giant piston cores to determine the distribution of gas hydrate in the northern Gulf of Mexico. Hydrates recovered during the cruise did not appear to be lithologically controlled (unlike Canadian Arctic cores) and were either disseminated or were massive layers. Sediment water content typically decreases rapidly to a subbottom depth of about 8 to 9 m, but then decreases at a lower rate. At-sea help was provided by the IMAGES (International Marine Past Global Changes Study) and PAGE (Paleoceanography of the Atlantic and Geochemistry) programs, and funding was provided by the U.S. Dept. of Energy. We have used the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI) to analyze sediment containing natural gas hydrate and to examine hydrate formed within (a) initially water-saturated and (b) partly-water saturated sieved Ottawa sand specimens at a pore pressure of 12 MPa and 250 kPa confining stress. Hydrate is formed when methane gas is slowly percolated into a 70-mm diameter by 140-mm long cylindrical specimen and subsequently the temperature is lowered to about 6 degrees C. We have found that acoustic velocity, shear strength, and permeability of samples containing different initial water contents are significantly affected by (a) the amount of hydrate present, (b) its distribution, (c) its position within pores, and (d) concentration at key locations. Acoustic P-wave velocities can increase from 1.7 km/s to 4.0 km/s using different hydrate and synthetic sample formation techniques. Although acoustic properties are significantly affected by hydrate at grain boundaries, the mere presence of hydrate in pores (but not necessarily at grain contacts) causes strength to significantly increase because dilation during undrained shear results in greater negative pore pressures. Recently determined strengths of three Ottawa sand samples are exponentially related to the degree of water saturation, bulk density, and hydrate content.

Experimental Study on Clogging of Fine Particles in Sand Sediments

NASA Astrophysics Data System (ADS)

Hirabayashi, S.

2015-12-01

In the methane hydrate development from the sand sediment beneath the seafloor, it is anticipated that the migrating fine particles may block the pore and consequently reduces the permeability near the production well. Although this phenomenon is known as skin formation, its microscopic mechanism is still unknown. As a part of a Japanese National hydrate research program (MH21, funded by METI), we carried out an experiment on the clogging of fine particles in sand sediments. A transparent core holder was newly developed to directly visualize the behavior of fine particles in the pore of frame sands and formation of skin. It was observed that there seems to be an induction time before the clogging starts to occur. Once clogging occurs, the upstream fine particles cannot move downstream anymore and the skin is formed. It was found that the rate of skin formation is related to the total volume of injected fine particles while the flow velocity has something to do with the length of the induction time.

Measurement of bedload transport in sand-bed rivers: a look at two indirect sampling methods

USGS Publications Warehouse

Holmes, Robert R.; Gray, John R.; Laronne, Jonathan B.; Marr, Jeffrey D.G.

2010-01-01

Sand-bed rivers present unique challenges to accurate measurement of the bedload transport rate using the traditional direct sampling methods of direct traps (for example the Helley-Smith bedload sampler). The two major issues are: 1) over sampling of sand transport caused by “mining” of sand due to the flow disturbance induced by the presence of the sampler and 2) clogging of the mesh bag with sand particles reducing the hydraulic efficiency of the sampler. Indirect measurement methods hold promise in that unlike direct methods, no transport-altering flow disturbance near the bed occurs. The bedform velocimetry method utilizes a measure of the bedform geometry and the speed of bedform translation to estimate the bedload transport through mass balance. The bedform velocimetry method is readily applied for the estimation of bedload transport in large sand-bed rivers so long as prominent bedforms are present and the streamflow discharge is steady for long enough to provide sufficient bedform translation between the successive bathymetric data sets. Bedform velocimetry in small sandbed rivers is often problematic due to rapid variation within the hydrograph. The bottom-track bias feature of the acoustic Doppler current profiler (ADCP) has been utilized to accurately estimate the virtual velocities of sand-bed rivers. Coupling measurement of the virtual velocity with an accurate determination of the active depth of the streambed sediment movement is another method to measure bedload transport, which will be termed the “virtual velocity” method. Much research remains to develop methods and determine accuracy of the virtual velocity method in small sand-bed rivers.

Tracing metal sources in core sediments of the artificial lake An-Dong, Korea: Concentration and metal association.

PubMed

Choi, Mansik; Park, Jongkyu; Cho, Dongjin; Jang, Dongjun; Kim, Miseon; Choi, Jongwoo

2015-09-15

The concentration and source of trace metals in the artificial lake An-Dong, which has widespread abandoned mines and a Zn smelter upstream of the drainage basin, were investigated. Soils (18ea), stream waters (15ea) and sediments (15ea) in the main channel and five tributaries downstream of the Zn smelter towards the lake (~ 50 km downstream) were collected. And two core sediments were also taken from the middle of the lake. All samples were analyzed for trace metals in bulk and in a 1N HCl-leached fraction. Although the soil and stream sediments consisted mostly of sand-sized grains, concentrations of metals (Cu, Zn, Cd and Pb) were very high in all samples, including soils, stream waters and sediments at sites near the Zn smelter. However the metal concentrations decreased rapidly downstream, suggesting that the area of impact of the smelter lies within 5 km. Highly enriched metal concentrations were also found in dated core sediments from the lake; while the highest concentrations of Co, Ni, As, Cu, Zn, Cd and Pb were detected in the bottom of the sediment core (dated 1980) they decreased towards 2000, and only Cu, Zn and Cd concentrations increased again in present-day samples. Since the temporal variation in metal concentrations appeared consistent with historical variation in ore mining and Zn smelter production rates, a model combining the production rates of each was developed, which estimated 3%, 12% and 7% contributions from Zn smelter compared to ore mining production rate to levels of Cu, Cd and Zn, respectively, suggesting the different pathways by different sources. In addition, analysis of Cd/Zn and Cu/Zn ratios showed that contamination from ore mining decreased from 1980 to 2000, and smelting processes were most likely responsible for metal enrichment (Cu, Cd and Zn) from 2000 to the present. Copyright © 2015 Elsevier B.V. All rights reserved.

Sedimentology and carbon-isotope stratigraphy of the Late Cretaceous Chalk Group in the Höllviken-1 core (SW Sweden)

NASA Astrophysics Data System (ADS)

Bøttger, Dorthe; Thibault, Nicolas; Anderskouv, Kresten

2016-04-01

The Höllviken-1 borehole is situated on the Skåne peninsula (SW Sweden) which was part of the Danish Basin in the Late Cretaceous. 1415 meters have been cored among which ca. 1100 meters cover the complete Upper Cretaceous to lower Danian Chalk Group. Besides the publication of a synthetic log and detailed foraminifer biozonation, supplemented by a number of rare macrofossil findings and description of a number of foraminifer holotypes (Brötzen, 1944), very few studies of the core have actually been performed, since the mid 1940s. A new project has thus been undertaken aiming at improving the stratigraphy of the Chalk Group in the Höllviken-1 core. The data presented here comprise the description of the interval 837-489 m covering a large part of the Campanian and the lower Maastrichtian. Two intervals with the presence of sand are noted in the Campanian and two intervals showing possibly progradational sequences of arenaceous marls to sand are present in the Maastrichtian. The purpose of this new study is to revise the foraminifer biostratigraphy of Brötzen and complement it with high-resolution carbon-isotope stratigraphy in order to establish a new age-model for the core and better constrain the timing of siliciclastic input into the Danish Basin. In addition, high-resolution sedimentological data will be used as a preliminary test for cyclostratigraphy of the chalk-marl intervals.

Investigation of quartz grain surface textures by atomic force microscopy for forensic analysis.

PubMed

Konopinski, D I; Hudziak, S; Morgan, R M; Bull, P A; Kenyon, A J

2012-11-30

This paper presents a study of quartz sand grain surface textures using atomic force microscopy (AFM) to image the surface. Until now scanning electron microscopy (SEM) has provided the primary technique used in the forensic surface texture analysis of quartz sand grains as a means of establishing the provenance of the grains for forensic reconstructions. The ability to independently corroborate the grain type classifications is desirable and provides additional weight to the findings of SEM analysis of the textures of quartz grains identified in forensic soil/sediment samples. AFM offers a quantitative means of analysis that complements SEM examination, and is a non-destructive technique that requires no sample preparation prior to scanning. It therefore has great potential to be used for forensic analysis where sample preservation is highly valuable. By taking quantitative topography scans, it is possible to produce 3D representations of microscopic surface textures and diagnostic features for examination. Furthermore, various empirical measures can be obtained from analysing the topography scans, including arithmetic average roughness, root-mean-square surface roughness, skewness, kurtosis, and multiple gaussian fits to height distributions. These empirical measures, combined with qualitative examination of the surfaces can help to discriminate between grain types and provide independent analysis that can corroborate the morphological grain typing based on the surface textures assigned using SEM. Furthermore, the findings from this study also demonstrate that quartz sand grain surfaces exhibit a statistically self-similar fractal nature that remains unchanged across scales. This indicates the potential for a further quantitative measure that could be utilised in the discrimination of quartz grains based on their provenance for forensic investigations. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Channel Morphology and Bed Sediment Characteristics Before and After Habitat Enhancement Activities in the Uridil Property, Platte River, Nebraska, Water Years 2005-2008

USGS Publications Warehouse

Kinzel, Paul J.

2009-01-01

Fluvial geomorphic data were collected by the United States Geological Survey from July 2005 to June 2008 (a time period within water years 2005 to 2008) to monitor the effects of habitat enhancement activities conducted in the Platte River Whooping Crane Maintenance Trust's Uridil Property, located along the Platte River, Nebraska. The activities involved the removal of vegetation and sand from the tops of high permanent islands and the placement of the sand into the active river channel. This strategy was intended to enhance habitat for migratory water birds by lowering the elevations of the high islands, thereby eliminating a visual obstruction for roosting birds. It was also thought that the bare sand on the lowered island surfaces could serve as potential habitat for nesting water birds. Lastly, the project supplied a local source of sediment to the river to test the hypothesis that this material could contribute to the formation of lower sandbars and potential nesting sites downstream. Topographic surveys on the islands and along river transects were used to quantify the volume of removed sand and track the storage and movement of the introduced sand downstream. Sediment samples were also collected to map the spatial distribution of river bed sediment sizes before and after the management activities. While the project lowered the elevation of high islands, observations of the sand addition indicated the relatively fine-grained sand that was placed in the active river channel was rapidly transported by the flowing water. Topographic measurements made 3 months after the sand addition along transects in the area of sediment addition showed net aggradation over measurements made in 2005. In the year following the sand addition, 2007, elevated river flows from local rain events generally were accompanied by net degradation along transects within the area of sediment addition. In the spring of 2008, a large magnitude flow event of approximately 360 cubic meters per second occurred in the study reach and was accompanied by net aggradation in the managed area. These observations illustrate the high sediment transport capacity of the river channel both at lower flows, when the sand was added, and during higher flow events. This field experiment also serves as a practical example of the dynamic response of a Platte River channel to a relatively small-scale sand augmentation project directed toward enhancing in-channel habitat for avian species.

Producing Light Oil from a Frozen Reservoir: Reservoir and Fluid Characterization of Umiat Field, National Petroleum Reserve, Alaska

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

Hanks, Catherine

Umiat oil field is a light oil in a shallow, frozen reservoir in the Brooks Range foothills of northern Alaska with estimated oil-in-place of over 1 billion barrels. Umiat field was discovered in the 1940’s but was never considered viable because it is shallow, in the permafrost, and far from any transportation infrastructure. The advent of modern drilling and production techniques has made Umiat and similar fields in northern Alaska attractive exploration and production targets. Since 2008 UAF has been working with Renaissance Alaska Inc. and, more recently, Linc Energy, to develop a more robust reservoir model that can bemore » combined with rock and fluid property data to simulate potential production techniques. This work will be used to by Linc Energy as they prepare to drill up to 5 horizontal wells during the 2012-2013 drilling season. This new work identified three potential reservoir horizons within the Cretaceous Nanushuk Formation: the Upper and Lower Grandstand sands, and the overlying Ninuluk sand, with the Lower Grandstand considered the primary target. Seals are provided by thick interlayered shales. Reserve estimates for the Lower Grandstand alone range from 739 million barrels to 2437 million barrels, with an average of 1527 million bbls. Reservoir simulations predict that cold gas injection from a wagon-wheel pattern of multilateral injectors and producers located on 5 drill sites on the crest of the structure will yield 12-15% recovery, with actual recovery depending upon the injection pressure used, the actual Kv/Kh encountered, and other geologic factors. Key to understanding the flow behavior of the Umiat reservoir is determining the permeability structure of the sands. Sandstones of the Cretaceous Nanushuk Formation consist of mixed shoreface and deltaic sandstones and mudstones. A core-based study of the sedimentary facies of these sands combined with outcrop observations identified six distinct facies associations with distinctive permeability trends. The Lower Grandstand sand consists of two coarsening-upward shoreface sands sequences while the Upper Grandstand consists of a single coarsening-upward shoreface sand. Each of the shoreface sands shows a distinctive permeability profile with high horizontal permeability at the top getting progressively poorer towards the base of the sand. In contrast, deltaic sandstones in the overlying Ninuluk are more permeable at the base of the sands, with decreasing permeability towards the sand top. These trends impart a strong permeability anisotropy to the reservoir and are being incorporated into the reservoir model. These observations also suggest that horizontal wells should target the upper part of the major sands. Natural fractures may superimpose another permeability pattern on the Umiat reservoir that need to be accounted for in both the simulation and in drilling. Examination of legacy core from Umiat field indicate that fractures are present in the subsurface, but don't provide information on their orientation and density. Nearby surface exposures of folds in similar stratigraphy indicate there are at least three possible fracture sets: an early, N/S striking set that may predate folding and two sets possibly related to folding: an EW striking set of extension fractures that are parallel to the fold axes and a set of conjugate shear fractures oriented NE and NW. Analysis of fracture spacing suggests that these natural fractures are fairly widely spaced (25-59 cm depending upon the fracture set), but could provide improved reservoir permeability in horizontal legs drilled perpendicular to the open fracture set. The phase behavior of the Umiat fluid needed to be well understood in order for the reservoir simulation to be accurate. However, only a small amount of Umiat oil was available; this oil was collected in the 1940’s and was severely weathered. The composition of this ‘dead’ Umiat fluid was characterized by gas chromatography. This analysis was then compared to theoretical Umiat composition derived using the Pedersen method with original Umiat fluid properties published in the original reports. This comparison allowed estimation of the ‘lost’ light hydrocarbon fractions. An Umiat 'dead' oil sample then could be physically created by adding the lost light ends to the weatherized Umiat dead oil sample. This recreated sample was recombined with solution gas to create a 'pseudo-live' Umiat oil sample which was then used for experimental PVT and phase behavior studies to determine fluid properties over the range of reservoir pressures and temperatures. The phase behavior of the ‘pseudo-live’ oil was also simulated using the Peng- Robinson equations of state (EOS). The EOS model was tuned with measured experimental data to accurately simulate the differential liberation tests in order to obtain the necessary data for reservoir simulation studies, including bubble point pressure and oil viscosity. The bubble point pressure of the reconstructed Umiat oil is 345 psi, suggesting that maintenance of reservoir pressures above that pressure will be important for the any proposed production technique. A major part of predicting how the Umiat reservoir will perform is determining the relative permeability of oil in the presence of ice. Early in the project, UAF work on samples of the Umiat reservoir indicated that there is a significant reduction in the relatively permeability of oil in the presence of ice. However, it was not clear as to why this reduction occurred or where the ice resided. To explore this further, additional experimental and theoretical work was conducted. Core flood experiments were performed on two clean Berea sandstone cores under permafrost conditions to determine the relative permeability to oil (kro) over a temperature range of 23ºC to - 10ºC and for a range of connate water salinities. Both cores showed maximum reduction in relative permeability to oil when saturated with deionized water and less reduction when saturated with saline water. This reduction in relative permeability can be explained by formation of ice crystals in the center of pores. Theoretically, the radius of ice formed in the center of the pore can be determined using the Kozeny–Carman Equation by assuming the pores and pore throats as a cube with ‘N’ identical parallel pipes embedded in it. Using the values of kro obtained from the experimental work as input to the Kozeny–Carman Equation at -10ºC, the radius of ice crystals dropped from 0.145 μm to 0.069 μm when flooding-water salinity is increased to 6467 ppm. This explains the reduction of relative permeability with decreasing salinity but does not take into consideration other effects such as variations in pore throat structure. In addition, fluids like deionized water, saline water, and antifreeze (a mixture of 60% ethylene or propylene glycol with 40% water) were tested to find the best flooding agent for frozen reservoirs. At 0ºC, 9% greater recovery was observed with antifreeze was used as a flooding agent as compared to using saline water. Antifreeze showed 48% recovery even at -10ºC, at which temperature the rest of the fluids failed to increase production. Preliminary evaluation of drilling fluids indicate that the brine-based muds caused significantly less swelling in the Umiat reservoir sands when compared to fresh-water based muds. However since freezing filtrate is another cause of formation damage, a simple water-based-mud may not a viable option. It is recommended that new fluids be tested, including different salts, brines, polymers and oil-based fluids. These fluids should be tested at low temperatures in order to determine the potential for formation damage, the fluid properties under these conditions and to ensure that the freezing point is below that of the reservoir. In order to reduce the surface footprint while accessing the maximum amount of the Lower Grandstand interval, simulations used development from 5 surface locations with a wagon-wheel pattern of multilateral injectors and producers. There is no active aquifer support due to small peizometric head in the area and no existing gas cap, so an alternative method of pressure support is needed. Cold gas injection was used in the simulations as it is considered the most viable means of providing pressure maintenance while maintaining wellbore stability and reducing impact on the permafrost. Saline water injection may be a viable alternative, though this may have a detrimental effect on permafrost. In the short term, the results of this work are being incorporated into Linc Energy’s drilling and development plan. This project has also provided valuable information on the rock and fluid properties of low temperature reservoirs as well as the efficacy of potential production techniques for Umiat or similar shallow frozen reservoirs in the circum-Arctic.« less

Controlled experiments of hillslope co-evolution at the Biosphere 2 Landscape Evolution Observatory: toward prediction of coupled hydrological, biogeochemical, and ecological change

NASA Astrophysics Data System (ADS)

Volkmann, T. H. M.; Sengupta, A.; Pangle, L.; Abramson, N.; Barron-Gafford, G.; Breshears, D. D.; Bugaj, A.; Chorover, J.; Dontsova, K.; Durcik, M.; Ferre, T. P. A.; Harman, C. J.; Hunt, E.; Huxman, T. E.; Kim, M.; Maier, R. M.; Matos, K.; Alves Meira Neto, A.; Meredith, L. K.; Monson, R. K.; Niu, G. Y.; Pelletier, J. D.; Rasmussen, C.; Ruiz, J.; Saleska, S. R.; Schaap, M. G.; Sibayan, M.; Tuller, M.; Van Haren, J. L. M.; Wang, Y.; Zeng, X.; Troch, P. A.

2017-12-01

Understanding the process interactions and feedbacks among water, microbes, plants, and porous geological media is crucial for improving predictions of the response of Earth's critical zone to future climatic conditions. However, the integrated co-evolution of landscapes under change is notoriously difficult to investigate. Laboratory studies are typically limited in spatial and temporal scale, while field studies lack observational density and control. To bridge the gap between controlled lab and uncontrolled field studies, the University of Arizona - Biosphere 2 built a macrocosm experiment of unprecedented scale: the Landscape Evolution Observatory (LEO). LEO consists of three replicated, 330-m2 hillslope landscapes inside a 5000-m2 environmentally controlled facility. The engineered landscapes contain 1-m depth of basaltic tephra ground to homogenous loamy sand that will undergo physical, chemical, and mineralogical changes over many years. Each landscape contains a dense sensor network capable of resolving water, carbon, and energy cycling processes at sub-meter to whole-landscape scale. Embedded sampling devices allow for quantification of biogeochemical processes, and facilitate the use of chemical tracers applied with the artificial rainfall. LEO is now fully operational and intensive forcing experiments have been launched. While operating the massive infrastructure poses significant challenges, LEO has demonstrated the capacity of tracking multi-scale matter and energy fluxes at a level of detail impossible in field experiments. Initial sensor, sampler, and restricted soil coring data are already providing insights into the tight linkages between water flow, weathering, and (micro-) biological community development during incipient landscape evolution. Over the years to come, these interacting processes are anticipated to drive the model systems to increasingly complex states, potentially perturbed by changes in climatic forcing. By intensively monitoring the evolutionary trajectory, integrating data with models, and fostering community-wide collaborations, we envision that emergent landscape structures and functions can be linked and significant progress can be made toward predicting the coupled hydro-biogeochemical and ecological responses to global change.