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United States Geological Survey: Staff Publications

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Articles 811 - 840 of 1026

Full-Text Articles in Earth Sciences

Molybdenum Accumulation In Cariaco Basin Sediment Over The Past 24 K.Y.: A Record Of Water-Column Anoxia And Climate, Walter E. Dean, David Z. Piper, Larry C. Peterson Jun 1999

Molybdenum Accumulation In Cariaco Basin Sediment Over The Past 24 K.Y.: A Record Of Water-Column Anoxia And Climate, Walter E. Dean, David Z. Piper, Larry C. Peterson

United States Geological Survey: Staff Publications

Molybdenum (Mo) concentrations in a sediment core from the Cariaco basin on the Venezuelan continental shelf can be partitioned between a marine fraction and a terrigenous fraction. The accumulation rate of the marine fraction of Mo increased abruptly 15 000 calendar years ago (15 ka), from <0.5 mg • cm-2 • yr-1 to >4 μg • cm-2 • yr-1, and then decreased abruptly at 9 ka. The accumulation rate remained high throughout this 6 k.y. period, but exhibited maxima at 15–14 and 12.5 ka, corresponding in time to meltwater pulse IA into the Gulf of Mexico and the onset …

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Long-Term Prairie Falcon Population Changes In Relation To Prey Abundance, Weather, Land Uses, And Habitat Conditions, Karen Steenhof, Michael Kochert, Leslie B. Carpenter, Robert N. Lehman Feb 1999

Long-Term Prairie Falcon Population Changes In Relation To Prey Abundance, Weather, Land Uses, And Habitat Conditions, Karen Steenhof, Michael Kochert, Leslie B. Carpenter, Robert N. Lehman

United States Geological Survey: Staff Publications

We studied a nesting population of Prairie Falcons (Falco mexicanus) in the Snake River Birds of Prey National Conservation Area (NCA) from 1974-1997 to identify factors that influence abundance and reproduction. Our sampling period included two major droughts and associated crashes in Townsend's ground squirrel (Spermophilus townsendii) populations. The number of Prairie Falcon pairs found on long-term survey segments declined significantly from 1976-1997. Early declines were most severe at the eastern end of the NCA, where fires and agriculture have changed native shrubsteppe habitat. More recent declines occurred in the portion of canyon near the Orchard …

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Geochemistry, Toxicity, And Sorption Properties Of Contaminated Sediments And Pore Waters From Two Reservoirs Receiving Acid Mine Drainage, D. Kirk Nordstrom, Charles N. Alpers, Jennifer A. Coston, Howard E. Taylor, R. Blaine Mccleskey, James W. Ball, Scott Ogle, Jeffrey S. Cotsifas, James A. Davis Jan 1999

Geochemistry, Toxicity, And Sorption Properties Of Contaminated Sediments And Pore Waters From Two Reservoirs Receiving Acid Mine Drainage, D. Kirk Nordstrom, Charles N. Alpers, Jennifer A. Coston, Howard E. Taylor, R. Blaine Mccleskey, James W. Ball, Scott Ogle, Jeffrey S. Cotsifas, James A. Davis

United States Geological Survey: Staff Publications

Acid mine waters from the Iron Mountain Superfund Site, Shasta County, California, flow through Spring Creek Reservoir and into Keswick Reservoir on the Sacramento River. In Keswick Reservoir, the acid mine waters have neutralized on mixing with neutral-pH lake water, producing fine-grained, metalrich sediments. Sediment cores were collected during 1997 from both reservoirs for characterization and pore waters were extracted under anoxic conditions. Chemical composition, mineralogical identification, redox chemistry, sorption properties, and toxicity were determined on several samples. Metal concentrations in sediment ranged from 4 to 47 % for Fe, 200 to 4,800 mg/kg (milligrams per kilogram) for Cu, and …

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Trace-Element Concentrations In Streambed Sediment Across The Conterminous United States, Karen Rice Jan 1999

Trace-Element Concentrations In Streambed Sediment Across The Conterminous United States, Karen Rice

United States Geological Survey: Staff Publications

Trace-element concentrations in 541 streambed-sediment samples collected from 20 study areas across the conterminous United States were examined as part of the National Water-Quality Assessment Program of the U.S. Geological Survey. Sediment samples were sieved and the <63-μm fraction was retained for determination of total concentrations of trace elements. Aluminum, iron, titanium, and organic carbon were weakly or not at all correlated with the nine trace elements examined: arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, and zinc. Four different methods of accounting for background/ baseline concentrations were examined; however, normalization was not required because field sieving removed most of the background differences between samples. The sum of concentrations of trace elements characteristic of urban settings-copper, mercury, lead, and zinc-was well correlated with population density, nationwide. Median concentrations of seven trace elements (all nine examined except arsenic and selenium) were enriched in samples collected from urban settings relative to agricultural or forested settings. Forty-nine percent of the sites sampled in urban settings had concentrations of one or more trace elements that exceeded levels at which adverse biological effects could occur in aquatic biota.

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Abrupt Along-Strike Change In Tectonic Style: San Andreas Fault Zone, San Francisco Peninsula, Mary Lou Zoback, Robert C. Jachens, Jean A. Olson Jan 1999

Abrupt Along-Strike Change In Tectonic Style: San Andreas Fault Zone, San Francisco Peninsula, Mary Lou Zoback, Robert C. Jachens, Jean A. Olson

United States Geological Survey: Staff Publications

Seismicity and high-resolution aeromagnetic data are used to define an abrupt change from compressional to extensional tectonism within a 10- to 15-km-wide zone along the San Andreas fault on the San Francisco Peninsula and offshore from the Golden Gate. This 100-km-long section of the San Andreas fault includes the hypocenter of the Mw= 7.8 1906 San Francisco earthquake as well as the highest level of persistent microseismicity along that ~470-km-long rupture. We define two distinct zones of deformation along this stretch of the fault using well-constrained relocations of all post- 1969 earthquakes based a joint one-dimensional velocity/hypocenter inversion …

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A Memorial For William V. Sliter, Robert G. Douglas, Jere H. Lipps, James C. Ingle Jr., John Barron Jan 1999

A Memorial For William V. Sliter, Robert G. Douglas, Jere H. Lipps, James C. Ingle Jr., John Barron

United States Geological Survey: Staff Publications

William V. (Bill) Sliter, an internationally known micropaleontologist and research geologist for the U.S. Geological Survey, passed away suddenly, October, 1997, while talking to a colleague in his office. In his honor, B. Huber, T. Bralower, and M. Leckie organized a keynote symposium ‘‘Paleoecological and Geochemical Signatures of Cretaceous Anoxic Events’’ at the 1998 annual meeting of the Geological Society of America in Toronto, Canada. This theme issue of the Journal of Foraminiferal Research contains the published papers from the symposium and is dedicated to his memory.

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Comparison Of An Enzyme-Linked Immunosorbent Assay (Elisa) To Gas Chromatography (Gc) - Measurement Of Polychlorinated Biphenyls (Pcbs) In Selected Us Fish Extracts, James L. Zajicek, Donald E. Tillitt, Ted R. Schwartz, Christopher J. Schmitt, Robert O. Harrison Jan 1999

Comparison Of An Enzyme-Linked Immunosorbent Assay (Elisa) To Gas Chromatography (Gc) - Measurement Of Polychlorinated Biphenyls (Pcbs) In Selected Us Fish Extracts, James L. Zajicek, Donald E. Tillitt, Ted R. Schwartz, Christopher J. Schmitt, Robert O. Harrison

United States Geological Survey: Staff Publications

The analysis of PCBs in fish tissues by immunoassay methods was evaluated using fish collected from a US monitoring program, the National Contaminant Biomonitoring Program of the US Department of Interior, Fish and Wildlife Service. Selected composite whole fish samples, which represented widely varying concentrations and sources of PCBs, were extracted and subjected to congener PCB analysis by gas chromatography (GC) and total PCB analysis using an ELISA (ePCBs) calibrated against technical Aroclor 1248. PCB congener patterns in these fishes were different from the patterns found in commercial Aroclors or their combinations as demonstrated by principal component analysis of normalized …

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Biogenic Silica Records From The Bdp93 Drill Site And Adjacent Areas Of The Selenga Delta, Lake Baikal, Siberia, Steven M. Colman, John A. Peck, Josephine Hatton, Eugene B. Karabanov, John W. King Jan 1999

Biogenic Silica Records From The Bdp93 Drill Site And Adjacent Areas Of The Selenga Delta, Lake Baikal, Siberia, Steven M. Colman, John A. Peck, Josephine Hatton, Eugene B. Karabanov, John W. King

United States Geological Survey: Staff Publications

Biogenic silica contents of sediments on the lower Selenga Delta and Buguldeika saddle in Lake Baikal show distinct fluctuations that reflect changes in diatom productivity, and ultimately, climate. The pattern of the upper 50 m of the section, dating from about 334 ka, is similar to that of the marine oxygen isotope record, increasingly so as the younger sediments become progressively finer grained and less locally derived with time. The last two interglaciations are marked by biogenic silica abundances similar to those of the Holocene. The equivalent of marine oxygenisotope stage 3 is distinctly intermediate in character between full glacial …

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The Carbon Cycle And Biogeochemical Dynamics In Lake Sediments, Walter E. Dean Jan 1999

The Carbon Cycle And Biogeochemical Dynamics In Lake Sediments, Walter E. Dean

United States Geological Survey: Staff Publications

The concentrations of organic carbon (OC) and CaCO3 in lake sediments are often inversely related. This relation occurs in surface sediments from different locations in the same lake, surface sediments from different lakes, and with depth in Holocene sediments. Where data on accumulation rates are available, the relation holds for organic carbon and CaCO3 accumulation rates as well. An increase of several percent OC is accompanied by a decrease of several tens of percent CaCO3 indicating that the inverse relation is not due to simple dilution of one component by another. It appears from core data that …

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200,000 Years Of Climate Change Recorded In Eolian Sediments Of The High Plains Of Eastern Colorado And Western Nebraska, Daniel R. Muhs, James Swinehart, David Loope, John N. Aleinikoff, Josh Been Jan 1999

200,000 Years Of Climate Change Recorded In Eolian Sediments Of The High Plains Of Eastern Colorado And Western Nebraska, Daniel R. Muhs, James Swinehart, David Loope, John N. Aleinikoff, Josh Been

United States Geological Survey: Staff Publications

Loess and eolian sand cover vast areas of the western Great Plains of Nebraska, Kansas and Colorado (Fig. 1). In recent studies of Quaternary climate change, there has been a renewed interest in loess and eolian sand. Much of the attention now given to loess stems from new studies of long loess sequences that contain detailed records of Quaternary glacial-interglacial cycles, thought to be a terrestrial equivalent to the foraminiferal oxygen isotope record in deep-sea sediments (Fig. 2). Loess is also a direct record of atmospheric circulation, and identification of loess paleowinds in the geologic record can test atmospheric general …

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Slip-Parallel Seismic Lineations On The Northern Hayward Fault, California, Felix Waldhauser, William L. Ellsworth, Alex Cole Jan 1999

Slip-Parallel Seismic Lineations On The Northern Hayward Fault, California, Felix Waldhauser, William L. Ellsworth, Alex Cole

United States Geological Survey: Staff Publications

A high-resolution relative earthquake location procedure is used to image the fine-scale seismicity structure of the northern Hayward fault, California. The seismicity defines a narrow, near-vertical fault zone containing horizontal alignments of hypocenters extending along the fault zone. The lineations persist over the 15-year observation interval, implying the localization of conditions on the fault where brittle failure conditions are met. The horizontal orientation of the lineations parallels the slip direction of the fault, suggesting that they are the result of the smearing of frictionally weak material along the fault plane over thousands of years.

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Late Quaternary Loess In Northeastern Colorado: Part I—Age And Paleoclimatic Significance, Daniel R. Muhs, John N. Aleinikoff, Thomas W. Stafford Jr., Rolf Kihl, Josh Been, Shannon A. Mahan, Scott Cowherd Jan 1999

Late Quaternary Loess In Northeastern Colorado: Part I—Age And Paleoclimatic Significance, Daniel R. Muhs, John N. Aleinikoff, Thomas W. Stafford Jr., Rolf Kihl, Josh Been, Shannon A. Mahan, Scott Cowherd

United States Geological Survey: Staff Publications

Loess in eastern Colorado covers an estimated 14,000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20,000 to 12,000 14C yr B.P. (ca. 20–14 ka) and correlates reasonably well with the culmination and retreat of Pinedale glaciers in the Colorado Front Range during the last glacial maximum. The second period of loess deposition occurred between ca. 11,000 and 9,000 14C yr B.P. This interval may be Holocene or may …

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Late Quaternary Loess In Northeastern Colorado: Part Ii—Pb Isotopic Evidence For The Variability Of Loess Sources, John N. Aleinikoff, Daniel R. Muhs, Rebecca R. Sauer, C. Mark Fanning Jan 1999

Late Quaternary Loess In Northeastern Colorado: Part Ii—Pb Isotopic Evidence For The Variability Of Loess Sources, John N. Aleinikoff, Daniel R. Muhs, Rebecca R. Sauer, C. Mark Fanning

United States Geological Survey: Staff Publications

A new application of the Pb isotopic tracer technique has been used to determine the relative importance of different silt sources for late Wisconsin loess in the central Great Plains of eastern Colorado. Samples of the Peoria Loess collected throughout the study area contain K-feldspar derived from two isotopically and genetically distinct sources: (1) glaciogenic material from Early and Middle Proterozoic crystalline rocks of the Colorado province, and (2) volcaniclastic material from the Tertiary White River Group exposed on the northern Great Plains. Pb isotopic compositions of K-feldspar in loess from two dated vertical sections (at Beecher Island and Last …

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Predation Of Artificial Ground Nests On White-Tailed Prairie Dog Colonies, Bruce W. Baker, Thomas R. Stanley, James A. Sedgwick Jan 1999

Predation Of Artificial Ground Nests On White-Tailed Prairie Dog Colonies, Bruce W. Baker, Thomas R. Stanley, James A. Sedgwick

United States Geological Survey: Staff Publications

Prairie dog (Cynomys spp.) colonies are unique to prairie and shrub-steppe landscapes. However, widespread eradication, habitat loss, and sylvatic plague (Yersinia pestis) have reduced their numbers by 98% since historical times. Birds associated with prairie dogs also are declining. Potential nest predators, such as coyotes (Canis latrans), swift foxes (Vulpes velox), and badgers (Taxidea taxus), may be attracted to colonies where a high concentration of prairie dogs serve as available prey. Increased abundance of small mammals, including prairie dogs, also may increase the risk of predation for birds nesting on colonies. …

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Atrazine Degradation In A Small Stream In Iowa, Dana W. Kolpin, Stephen J. Kalkhoff Jan 1999

Atrazine Degradation In A Small Stream In Iowa, Dana W. Kolpin, Stephen J. Kalkhoff

United States Geological Survey: Staff Publications

A study was conducted during 1990 through an 11.2-km reach of Roberts Creek in northeastern Iowa to determine the fate of atrazine in a surface water environment. Water samples were collected at ~1-month intervals from April through November during stable low to medium flow conditions and analyzed for atrazine and two of its initial biotic degradation products, desethylatrazine and deisopropylatrazine. Samples were collected on the basis of a Lagrangian model of streamflow in order to sample the same parcel of water as it moved downstream. Atrazine concentrations substantially decreased (roughly 25-60% ) between water entering and exiting the study reach …

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Are Shifts In Herbicide Use Reflected In Concentration Changes In Midwestern Rivers?, William Battaglin, Donald Goolsby Jan 1999

Are Shifts In Herbicide Use Reflected In Concentration Changes In Midwestern Rivers?, William Battaglin, Donald Goolsby

United States Geological Survey: Staff Publications

In many Midwestern rivers, elevated concentrations of herbicides occur during runoff events for 1-3 months following application. The highest or “peak” herbicide concentration often occurs during one of these runoff events. Herbicide concentrations in rivers are affected by a number of factors, including herbicide use patterns within the associated basin. Changing agricultural practices, reductions in recommended and permitted herbicide applications, shifts to new herbicides, and greater environmental awareness in the agricultural community have resulted in changes to herbicide use patterns. In the Midwestern United States, alachlor use was much larger in 1989 than in 1995, while acetochlor was not used …

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Negative Ph, Efflorescent Mineralogy, And Consequences For Environmental Restoration At The Iron Mountain Superfund Site, California, D. Kirk Nordstrom, Charles N. Alpers Jan 1999

Negative Ph, Efflorescent Mineralogy, And Consequences For Environmental Restoration At The Iron Mountain Superfund Site, California, D. Kirk Nordstrom, Charles N. Alpers

United States Geological Survey: Staff Publications

The Richmond Mine of the Iron Mountain copper deposit contains some of the most acid mine waters ever reported. Values of pH have been measured as low as -3.6, combined metal concentrations as high as 200 g/liter, and sulfate concentrations as high as 760 g/liter. Copious quantities of soluble metal sulfate salts such as melanterite, chalcanthite, coquimbite, rhomboclase, voltaite, copiapite, and halotrichite have been identified, and some of these are forming from negative-pH mine waters. Geochemical calculations show that, under a mine-plugging remediation scenario, these salts would dissolve and the resultant 600,000-m3 mine pool would have a pH of …

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Magnitude And Significance Of Carbon Burial In Lakes, Reservoirs, And Peatlands, Walter E. Dean, Eville Gorham Jun 1998

Magnitude And Significance Of Carbon Burial In Lakes, Reservoirs, And Peatlands, Walter E. Dean, Eville Gorham

United States Geological Survey: Staff Publications

Globally, lakes are currently accumulating organic carbon (OC) at an estimated annual rate of about 42 Tg•yr-1. Most of the OC in all but the most oligotrophic of these lakes is autochthonous, produced by primary production in the lakes. The sediments of reservoirs accumulate an additional 160 Tg annually, and peatlands contribute 96 Tg annually. These three carbon pools collectively cover less than 2% of the Earth’s surface and constitute a carbon sink of about 300 Tg•yr-1. Although the oceans cover 71% of the Earth’s surface, they accumulate OC at a rate of only about 100 …

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An Evaluation Of Methods For Identifying And Interpreting Buried Soils In Late Quaternary Loess In Alaska, Daniel R. Muhs, Thomas A. Ager, Josh M. Been, Joseph G. Rosenbaum, Richard L. Reynolds Jan 1998

An Evaluation Of Methods For Identifying And Interpreting Buried Soils In Late Quaternary Loess In Alaska, Daniel R. Muhs, Thomas A. Ager, Josh M. Been, Joseph G. Rosenbaum, Richard L. Reynolds

United States Geological Survey: Staff Publications

The presence of buried soils in Alaskan loess is controversial, and therefore criteria for identifying buried soils in these deposits need to be evaluated. In this paper, morphologic and chemical criteria for identifying buried soils are evaluated by studying modern soils developed mostly in Holocene loess under tundra, boreal forest, and transitional coastal-boreal forest vegetation in different parts of Alaska. Data from modern Alaskan soils that developed under vegetation similar to that of the present indicate that soil morphology, organic-matter concentrations, and P concentrations can be useful diagnostic tools for identifying buried soils. Soil morphologic criteria, particularly horizon colors and …

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Estimates Of Annual Survival Probabilities For Adult Florida Manatees (Trichechus Manatus Latirostris), C. A. Langtimm, T. J. O'Shea, R. Pradel, C. A. Beck Jan 1998

Estimates Of Annual Survival Probabilities For Adult Florida Manatees (Trichechus Manatus Latirostris), C. A. Langtimm, T. J. O'Shea, R. Pradel, C. A. Beck

United States Geological Survey: Staff Publications

The population dynamics of large, long-lived mammals are particularly sensitive to changes in adult survival. Understanding factors affecting survival patterns is therefore critical for developing and testing theories of population dynamics and for developing management strategies aimed at preventing declines or extinction in such taxa. Few studies have used modern analytical approaches for analyzing variation and testing hypotheses about survival probabilities in large mammals. This paper reports a detailed analysis of annual adult survival in the Florida manatee (Trichechus manatus latirostris), an endangered marine mammal, based on a mark-recapture approach. Natural and boat- inflicted scars distinctively "marked" individual …

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Book Review Of Paleolimnology Of Europeanmaar Lakes By J. F.W. Negendank & B. Zolitschka (Eds)., J. Platt Bradbury Jan 1998

Book Review Of Paleolimnology Of Europeanmaar Lakes By J. F.W. Negendank & B. Zolitschka (Eds)., J. Platt Bradbury

United States Geological Survey: Staff Publications

This book represents a collection of papers presented at a symposium in May, 1991 on the formation and paleolimnology of European maar lakes. Paleolimnological discussions embrace maar lake deposits of late Quaternary to early Tertiary age in Germany, France and Italy. The goal of the symposium and its outgrowth, this book, is to develop a funding initiative to study, core and analyze the deposits of these remarkable depositional systems.

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Observation Of The Seismic Nucleation Phase In The Ridgecrest, California, Earthquake Sequence, William L. Ellsworth, Gregory C. Beroza Jan 1998

Observation Of The Seismic Nucleation Phase In The Ridgecrest, California, Earthquake Sequence, William L. Ellsworth, Gregory C. Beroza

United States Geological Survey: Staff Publications

Near-source observations of five M 3.8-5.2 earthquakes near Ridgecrest, California are consistent with the presence of a seismic nucleation phase. These earthquakes start abruptly, but then slow or stop before rapidly growing again toward their maximum rate of moment release. Deconvolution of instrument and path effects by empirical Green's functions demonstrates that the initial complexity at the start of the earthquake is a source effect. The rapid growth of the P-wave arrival at the start of the seismic nucleation phase supports the conclusion of Mori and Kanamori [1996] that these earthquakes begin without a magnitude-scaled slow initial phase of the …

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Continuous Lake-Sediment Records Of Glaciation In The Sierra Nevada Between 52,600 And 12,500 14c Yr B.P., Larry Benson, Howard M. May, Ronald C. Antweiler, Terry I. Brinton, Michaele Kashgarian, Joseph P. Smoot, Steve P. Lund Jan 1998

Continuous Lake-Sediment Records Of Glaciation In The Sierra Nevada Between 52,600 And 12,500 14c Yr B.P., Larry Benson, Howard M. May, Ronald C. Antweiler, Terry I. Brinton, Michaele Kashgarian, Joseph P. Smoot, Steve P. Lund

United States Geological Survey: Staff Publications

The chemistry of the carbonate-free clay-size fraction of Owens Lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial-interstadial oscillations, Owens Lake records of total organic carbon, magnetic susceptibility, and chemical composition of the carbonate-free, clay-size fraction indicate that Tioga glaciation began ~24,500 and ended by ~13,600 14C yr B.P. Many of the components of glacial rock flour (e.g., TiO2 , MnO, BaO) found in Owens Lake sediments achieved maximum values during the Tioga glaciation when valley glaciers reached their greatest extent. Total organic carbon and Si02 (amorphous) concentrations reached minimum values …

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Early Life History Stages Of Gulf Sturgeon In The Suwannee River, Florida, Kenneth J. Sulak, James P. Clugston Jan 1998

Early Life History Stages Of Gulf Sturgeon In The Suwannee River, Florida, Kenneth J. Sulak, James P. Clugston

United States Geological Survey: Staff Publications

Egg sampling confirmed that Suwannee River Gulf sturgeon Acipenser ozyrinchus desotoi, a subspecies of Atlantic sturgeon A. o. oxyrinchus use the same spawning site at river kilometer (rkm) 215 from the mouth of the river each year. Forty-nine eggs were recorded in 1995, and 368 were recorded in 1996. Spawning began 4-7 d after the March new moon in both years and lasted 10-11 d; in 1996, a second 10-d spawning round began on the April new moon. Developmental synchrony among eggs recovered suggested serval discrete spawning events in both years. Total eggs deposited for three 1996 sampling days …

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Stable Isotopes And Sediments From Pickerel Lake, South Dakota, Usa: A 12ky Record Of Environmental Changes, Antje Schwalb, Walter E. Dean Jan 1998

Stable Isotopes And Sediments From Pickerel Lake, South Dakota, Usa: A 12ky Record Of Environmental Changes, Antje Schwalb, Walter E. Dean

United States Geological Survey: Staff Publications

Sedimentological parameters and stable O- and C-isotopic composition of marl and ostracode calcite selected from a 17.7 m long core from the 8 m deep center of Pickerel Lake, northeastern South Dakota, provide one of the longest (ca. 12ky) paleoenvironmental records from the northern Great Plains. The late Glacial to early Holocene climate in the northern Great Plains was characterized by changes from cold and wet to cold and dry, and back to cold and wet conditions. These climatic changes were controlled by fluctuations in the positions of the Laurentide ice sheet and the extent of glacial Lake Agassiz. We …

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Determination Of Bioavailable Contaminants In The Lower Missouri River Following The Flood Of 1993, Jimmie Petty, Barry Poulton, Colette Charbonneau, James Huckins, Susan Jones, Jennifer Cameron, Harry Prest Jan 1998

Determination Of Bioavailable Contaminants In The Lower Missouri River Following The Flood Of 1993, Jimmie Petty, Barry Poulton, Colette Charbonneau, James Huckins, Susan Jones, Jennifer Cameron, Harry Prest

United States Geological Survey: Staff Publications

The semipermeable membrane device (SPMD) technology was employed to determine the presence of bioavailable organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons (PAHs) in the water of the main stem of the lower Missouri River and three of its tributaries. The SPMDs were deployed in 1994 following the extensive flood of 1993. Specifically, the SPMDs were deployed for 28 days at Wilson State Park, IA; Nebraska City, NE; Parkville, MO; the Kansas River in Kansas City, KS; Napoleon, MO; the Grand River; Glasgow, MO; the Missouri River upstream from the confluence of the Gasconade River; the Gasconade River; and …

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Occurrence Of Pesticides In Shallow Groundwater Of The United States: Initial Results From The National Water-Quality Assessment Program, Dana Kolpin, Jake Barbash, Robert Gilliom Jan 1998

Occurrence Of Pesticides In Shallow Groundwater Of The United States: Initial Results From The National Water-Quality Assessment Program, Dana Kolpin, Jake Barbash, Robert Gilliom

United States Geological Survey: Staff Publications

The first phase of intensive data collection for the National Water-Quality Assessment (NAWQA) was completed during 1993-1995 in 20 major hydrologic basins of the United States. Groundwater land-use studies, designed to sample recently recharged groundwater (generally within 10 years) beneath specific land-use and hydrogeologic settings, are a major component of the groundwater quality assessment for NAWQA. Pesticide results from the 41 land use studies conducted during 1993-1995 indicate that pesticides were commonly detected in shallow groundwater, having been found at 54.4% of the 1034 sites sampled in agricultural and urban settings across the United States. Pesticide concentrations were generally low, …

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Seismic Rock-Physics Model For Carbonates At Low Effective Stress Levels Jan 1998

Seismic Rock-Physics Model For Carbonates At Low Effective Stress Levels

United States Geological Survey: Staff Publications

When considering the seismic response from the Dammam aquifer, the first required component is a simple model relating porosity and stress state to frame moduli assuming a carbonate matrix. We explored two such relationships, one based on the empirical regression presented by Domenico (1984) and a second using the critical porosity model of Nur et al. (1998) calibrated to the ultrasonic measurements of Nur and Simmons (1969). Once frame properties for a given porosity/pressure state were estimated, the effect of fluid changes were calculated using the low-frequency form of the Biot-Gassmann model, better known as Gassmann fluid substitution (Mavko …

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Rates, Timing, And Cyclicity Of Holocene Eolian Activity In North-Central United States: Evidence From Varved Lake Sediments, Walter E. Dean Apr 1997

Rates, Timing, And Cyclicity Of Holocene Eolian Activity In North-Central United States: Evidence From Varved Lake Sediments, Walter E. Dean

United States Geological Survey: Staff Publications

Most of the sediment components that accumulated in Elk Lake, northwestern Minnesota, during the Holocene are autochthonous or biogenic, delivered to the sediment-water interface on a seasonal schedule, preserved in distinct annual laminae (varves). The main allochthonous component is detrital clastic material, as measured by bulk-sediment concentrations of aluminum, sodium, potassium, titanium, and quartz, that enters the lake mostly as eolian dust. The eolian clastic influx to Elk Lake was considerably greater during the mid-Holocene (8–4 ka) than it has been for the past 4000 yr, when periods of increased eolian activity correspond to the time of the Little Ice …

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Fracture Permeability And Its Relationship To In-Situ Stress In The Dixie Valley, Nevada, Geothermal Reservoir, Colleen A. Barton, Stephen Hickman, Roger H. Morin, Mark D. Zoback, Thomas Finkbeiner, John Sass, Dick Benoit Jan 1997

Fracture Permeability And Its Relationship To In-Situ Stress In The Dixie Valley, Nevada, Geothermal Reservoir, Colleen A. Barton, Stephen Hickman, Roger H. Morin, Mark D. Zoback, Thomas Finkbeiner, John Sass, Dick Benoit

United States Geological Survey: Staff Publications

An extensive suite of spinner flowmeter, high-resolution temperature and borehole televiewer logs were acquired in a 2.7-km-deep well drilled into a fault-hosted geothermal reservoir at Dixie Valley, Nevada. Localized perturbations to wellbore temperature and flow were used to identify hydraulically conductive fractures. Comparison of these data with fracture orientations from the borehole televiewer logs indicates that hydraulically conductive fractures in crystalline rocks within and adjacent to the producing fault zone have an orientation distinct from the overall fracture population. In conjunction with in-situ stress measurements from this well, Coulomb analysis indicates that these permeable fractures are critically stressed, potentially active …

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