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Articles 3031 - 3060 of 4541

Full-Text Articles in Earth Sciences

Aquatic Dissipation Of The Herbicide Triclopyr In Lake Minnetonka, Minnesota, Kurt D. Getsinger, David G. Petty, John D. Madsen, John G. Skogerboe, Bruce A. Houtman, William T. Haller, Alison M. Fox Jan 2000

Aquatic Dissipation Of The Herbicide Triclopyr In Lake Minnetonka, Minnesota, Kurt D. Getsinger, David G. Petty, John D. Madsen, John G. Skogerboe, Bruce A. Houtman, William T. Haller, Alison M. Fox

United States Army Corps of Engineers, Omaha District

A study of the aquatic fate of the triethylamine salt of triclopyr (3,5,6-trichloro-2- pyridinyloxyacetic acid) was conducted in three bays of Lake Minnetonka, Minnesota. Triclopyr is under review by the US Environmental Protection Agency as a selective aquatic herbicide. The primary purpose of this study was to determine dissipation rates of the parent active ingredient, triclopyr, and its major metabolites, 3,5,6-trichloropyridinol (TCP) and 3,5,6-trichloro-2-methoxypyridine (TMP) in selected matrices including water, sediment, plants, finfish and shellfish. Two 6.5- ha plots dominated by the weedy species Eurasian watermilfoil (Myriophyllum spicatum L) were treated with triclopyr-triethylammonum at a rate of 2.5mg AE liter …

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Geochemical And Mineralogical Evidence From Eolian Sediments For Northwesterly Mid-Holocene Paleowinds, Central Kansas, Usa, Alan F. Arbogast, Daniel R. Muhs Jan 2000

Geochemical And Mineralogical Evidence From Eolian Sediments For Northwesterly Mid-Holocene Paleowinds, Central Kansas, Usa, Alan F. Arbogast, Daniel R. Muhs

United States Geological Survey: Staff Publications

A prominent (4500 km2) dune field in the Great Plains is the Great Bend Sand Prairie of south-central Kansas. Dunes here overlie late Quaternary alluvium and were reactivated extensively in the late Holocene. Geomorphic and soil evidence suggests that the most likely eolian sand source is the Arkansas River valley to the northwest. Nevertheless, orientations of stabilized dunes indicate that the most recent dune-forming winds came from the south or southwest, in agreement with modern wind data.

Mineralogy and trace element concentrations in eolian sands of the Great Bend Sand Prairie are similar to those of the Arkansas …

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Geochemical Variations In Peoria Loess Of Western Iowa Indicate Paleowinds Of Midcontinental North America During Last Glaciation, Daniel R. Muhs, E. Arthur Bettis Iii Jan 2000

Geochemical Variations In Peoria Loess Of Western Iowa Indicate Paleowinds Of Midcontinental North America During Last Glaciation, Daniel R. Muhs, E. Arthur Bettis Iii

United States Geological Survey: Staff Publications

Peoria Loess deposited in western Iowa during the last glacial maximum (LGM) shows distinct geochemical and particle-size variations as a function of both depth and distance east of the Missouri River. Geochemical and particle-size data indicate that Peoria Loess in western Iowa probably had two sources: the Missouri River valley, and a source that lay to the west of the Missouri River. Both sources indicate that LGM paleowinds in western Iowa had a strong westerly component, similar to interpretations of previous workers. A compilation of loess studies in Iowa and elsewhere indicates that westerlv winds were dominant during loess transport …

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Effects Of Topography And Soil Properties On Recharge At Two Sites In An Agricultural Field, Geoffrey N. Delin, Richard W. Healy, Matthew K. Landon, John Karl Böhlke Jan 2000

Effects Of Topography And Soil Properties On Recharge At Two Sites In An Agricultural Field, Geoffrey N. Delin, Richard W. Healy, Matthew K. Landon, John Karl Böhlke

United States Geological Survey: Staff Publications

Field experiments were conducted from 1992 to 1995 to estimate ground water recharge rates at two sites located within a 2.7-hectare agricultural field. The field lies in a sand plain setting in central Minnesota and is cropped continuously in field corn. The sites are located at a topographically high (upland) site and a topographically low (lowland) site in an effort to quantify the effects of depression focusing of recharge. Three site-specific methods were used to estimate recharge rates: well hydrograph analysis, chlorofluorocarbon age dating, and an unsaturated zone water balance. All three recharge methods indicated that recharge rates at the …

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Multivariate Correlation Between Concentrations Of Selected Herbicides And Derivatives In Outflows From Selected U.S. Midwestern Reservoirs, R. Tauler, D. Barcelo, E. Michael Thurman Jan 2000

Multivariate Correlation Between Concentrations Of Selected Herbicides And Derivatives In Outflows From Selected U.S. Midwestern Reservoirs, R. Tauler, D. Barcelo, E. Michael Thurman

United States Geological Survey: Staff Publications

Multivariate correlations between the concentrations of selected herbicides and herbicide derivatives in outflows from selected reservoirs in the Midwestern United States for April 1992 through September 1993 were investigated using principal component analysis (PCA) and multivariate curve resolution (MCR). Two independent sources for alachlor ethanesulfonic acid, one major source related to spring flush and seasonal runoff and another minor source related to groundwater, were identified using PCA. Results of MCR provided a semiquantitative interpretation of the environmental sources of the observed herbicide concentrations in reservoir outflows and allowed the examination of their temporal and geographical distributions. Samples with higher herbicide …

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Nutrients In Groundwaters Of The Conterminous United States, 1992-1995, Bernard Nolan, Jeffrey Stoner Jan 2000

Nutrients In Groundwaters Of The Conterminous United States, 1992-1995, Bernard Nolan, Jeffrey Stoner

United States Geological Survey: Staff Publications

Results of a national water quality assessment indicate that nitrate is detected in 71% of groundwater samples, more than 13 times as often as ammonia, nitrite, organic nitrogen, and orthophosphate, based on a common detection threshold of 0.2 mg/L. Shallow groundwater (typically 5 m deep or less) beneath agricultural land has the highest median nitrate concentration (3.4 mg/L), followed by shallow groundwater beneath urban land (1.6 mg/L) and deeper groundwater in major aquifers (0.48 mg/L). Nitrate exceeds the maximum contaminant level, 10 mg/L as nitrogen, in more than 15% of groundwater samples from 4 of 33 major aquifers commonly used …

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Ecogeochemistry Of The Subsurface Food Web At Ph 0–2.5 In Iron Mountain, California, U.S.A., Eleanora I. Robbins, Teresa M. Rodgers, Charles N. Alpers, D. Kirk Nordstrom Jan 2000

Ecogeochemistry Of The Subsurface Food Web At Ph 0–2.5 In Iron Mountain, California, U.S.A., Eleanora I. Robbins, Teresa M. Rodgers, Charles N. Alpers, D. Kirk Nordstrom

United States Geological Survey: Staff Publications

Pyrite oxidation in the underground mining environment of Iron Mountain, California, has created the most acidic pH values ever reported in aquatic systems. Sulfate values as high as 120 000 mg 1-1 and iron as high as 27600mg 1-1 have been measured in the mine water, which also carries abundant other dissolved metals including Al, Zn, Cu, Cd, Mn, Sb and Pb. Extreme acidity and high metal concentrations apparently do not preclude the presence of an underground acidophilic food web, which has developed with bacterial biomass at the base and heliozoans as top predators. Slimes, oil-like films, flexible …

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Groundwater-Level Changes In Nebraska - Spring 1999 To Spring 2000, Conservation Survey Division Jan 2000

Groundwater-Level Changes In Nebraska - Spring 1999 To Spring 2000, Conservation Survey Division

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Field Trip Guide (For The Nebraska Well Drillers Association) Eastern Nebraska Geology, S. Summerside, D. A. Eversoll, M. Kuzila, M. Joeckel Jan 2000

Field Trip Guide (For The Nebraska Well Drillers Association) Eastern Nebraska Geology, S. Summerside, D. A. Eversoll, M. Kuzila, M. Joeckel

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Resource News-Spring 2000 Jan 2000

Resource News-Spring 2000

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Calamus River Valley Map, University Of Nebraska - Lincoln Jan 2000

Calamus River Valley Map, University Of Nebraska - Lincoln

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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County Names/Numbers, University Of Nebraska - Lincoln Jan 2000

County Names/Numbers, University Of Nebraska - Lincoln

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Natural Resource Districts In Nebraska, Nebraska Natural Resource Commission Jan 2000

Natural Resource Districts In Nebraska, Nebraska Natural Resource Commission

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Nebraska Information, Number Of Topographical Maps Per County, University Of Nebraska - Lincoln Jan 2000

Nebraska Information, Number Of Topographical Maps Per County, University Of Nebraska - Lincoln

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Overland Trails, University Of Nebraska - Lincoln Jan 2000

Overland Trails, University Of Nebraska - Lincoln

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Nebraska Map Of Counties, Conservation And Survey Division Jan 2000

Nebraska Map Of Counties, Conservation And Survey Division

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Distribution And Thickness Of Glacial Till In Nebraska. Jan 2000

Distribution And Thickness Of Glacial Till In Nebraska.

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Metric System Vs. Inch-Pound Units Jan 2000

Metric System Vs. Inch-Pound Units

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Chase County Test Hole Logs, Vincent H. Dreeszen Jan 2000

Chase County Test Hole Logs, Vincent H. Dreeszen

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Dakota County Test Hole Logs, Raymond R. Burchett, Frank A. Smith Jan 2000

Dakota County Test Hole Logs, Raymond R. Burchett, Frank A. Smith

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Custer County Test Hole Logs, Larry D. Cast Jan 2000

Custer County Test Hole Logs, Larry D. Cast

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Gosper County Test Hole Logs, Larry D. Cast Jan 2000

Gosper County Test Hole Logs, Larry D. Cast

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Garden County Test Hole Logs, Frank A. Smith Jan 2000

Garden County Test Hole Logs, Frank A. Smith

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Kimball County Test Hole Logs, Frank A. Smith Jan 2000

Kimball County Test Hole Logs, Frank A. Smith

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Preliminary Results Of Bitumen And Whole-Rock Elemental Analyses Of Crp-2/2a, Victoria Land Basin, Antarctica, Richard Kettler, E. Papastavros Jan 2000

Preliminary Results Of Bitumen And Whole-Rock Elemental Analyses Of Crp-2/2a, Victoria Land Basin, Antarctica, Richard Kettler, E. Papastavros

Department of Earth and Atmospheric Sciences: Faculty Publications

Sediments and rocks recovered in CRP-2/2A coring operations contain relatively little organic matter (average TOC=0.28%) and very small amounts of solvent-soluble organic matter. Because Early Oligocene sediment included significant amounts of coal detritus, TOC values are higher in Early Oligocene rocks than in younger rocks. TOC values are highest in the fine-grained rocks deposited as part of the highstand systems tract (HST) and TOC values decrease from the bottom to the top of the HST. The TOC:TN ratios observed in the CRP-2/2A core typically exceed 10, and are strong evidence that the preserved organic matter comprises a mixture of detrital …

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Laser-Derived, Particle Size Data From Crp-2/2a: Implications For Sequence And Seismic Stratigraphy, K J. Woolfe, L K. Stewart, Christopher R. Fielding, M Lavelle Jan 2000

Laser-Derived, Particle Size Data From Crp-2/2a: Implications For Sequence And Seismic Stratigraphy, K J. Woolfe, L K. Stewart, Christopher R. Fielding, M Lavelle

Department of Earth and Atmospheric Sciences: Faculty Publications

Gravel-free, high-resolution (1-metre spacing, 32 channel) particle size data from the CRP-2/2A drill core indicate that many of the diamictites were likely deposited from floating ice. Textural dislocations occur at most sequence boundaries and provide independent corroboration of the sequence stratigraphic interpretation. Likewise the data largely support the correlation drawn (Fielding et al., this volume) between the sequence stratigraphic cycles and the regional seismic stratigraphy (an alternative correlation to Reflector ‘f’ is also suggested). The gravel-free data appear to be reflecting predominantly regional (global?) forcing with some possible local effects, and long-term trends persisting through gravelly textural dislocations.

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Morphology And Taxonomic Position Of The Late Cretaceous Diatom Genus Pomphodiscus Barker & Meakin, Vladimir A. Nikolaev, David M. Harwood Jan 2000

Morphology And Taxonomic Position Of The Late Cretaceous Diatom Genus Pomphodiscus Barker & Meakin, Vladimir A. Nikolaev, David M. Harwood

Department of Earth and Atmospheric Sciences: Faculty Publications

Results from our investigation of Upper Cretaceous diatoms from the Marca Shale Member of the Moreno Shale in California and from Ocean Drilling Program (ODP) Hole 748C on the Kerguelen Plateau ,Southern Indian Ocean enable a clarification of the taxonomic position of several diatoms. Differences in areola structure ,a primary and conservative character of the diatom valve, are used to separate diatoms recently included in the genus Benetorus. We resurrect he genus Pomphodiscusto include species with locular areolae, a central rimoportula ,and a central inflated chamber .We propose the new species Pomphodiscusk erguelensisn. sp. and new combination Pomphodiscusc …

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Oligocene And Lower Miocene Siliceous Microfossil Biostratigraphy Of Cape Roberts Project Core Crp-2/2a, Victoria Land Basin, Antarctica, R. Scherer, S. M. Bohaty, David M. Harwood Jan 2000

Oligocene And Lower Miocene Siliceous Microfossil Biostratigraphy Of Cape Roberts Project Core Crp-2/2a, Victoria Land Basin, Antarctica, R. Scherer, S. M. Bohaty, David M. Harwood

Department of Earth and Atmospheric Sciences: Faculty Publications

Marine diatoms are the primary biostratigraphical and palaeoenvironmental tool for interpreting the upper Palaeogene and lower Neogene strata recovered during the second drilling season of the Cape Roberts Project at site CRP-2 in the western Ross Sea, Antarctica. Silicoflagellates, ebridians, and a chrysophyte cyst provide supporting biostratigraphical information. More than 100 dominantly planktic diatom taxa are recognised. Of these, more than 30 are treated informally, pending SEM examination and formal description. Many other taxa are noted only to generic level. Lower Oligocene (c. 31Ma) through lower Miocene (c. 18.5 Ma) diatoms occur from 28 mbsf down to 565 …

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Nutrients As A Link Between Ionic Concentration/Composition And Diatom Distributions In Saline Lakes, J. E. Saros, Sherilyn C. Fritz Jan 2000

Nutrients As A Link Between Ionic Concentration/Composition And Diatom Distributions In Saline Lakes, J. E. Saros, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Diatom profiles in closed-basin lake sediments are commonly used to reconstruct climate change based on the observed correlations between salinity (ionic concentration) and modern diatom assemblages. Diatom assemblages are strongly correlated not only with salinity but also anion composition, with certain taxa characteristic of carbonate systems and others sulfate-dominated waters. Although strong correlations exist, the actual mechanisms behind these correlations are unknown. Here we briefly review the influence of salinity and ionic composition on nutrient dynamics in saline lakes and suggest that these interactions may drive shifts in diatom species composition along gradients of ionic concentration/ composition. We discuss the …

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Clay Mineral Composition Of Glacial Erratics, Mcmurdo Sound, Mary Anne Holmes Jan 2000

Clay Mineral Composition Of Glacial Erratics, Mcmurdo Sound, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

Twenty-two erratics collected from coastal moraines along the shores of Mount Discovery, Brown Peninsula, Minna Bluff, on Black Island, and from the Salmon and Miers valley floors in East Antarctica were examined for their mineral composition in the <2 m fraction by x-ray diffraction to determine their provenance and the climate under which the sediment in the erratics formed. Semi-quantitative results from peak areas were subjected to principal components analysis and indicate that there are two distinct mineral compositions in the erratics (C = 0.05): A) dominant smectite group minerals, minor illite and kaolinite, and no chlorite, and B) dominant illite, subordinate smectite group, and either chlorite and R=l US clay or R=3 US clay. Group A erratics include two types: 1) Eocene age siliciclastic sediment and 2) volcaniclastics of unknown age. Group B erratics comprise three types: 1) Eocene age siliciclastic sediment dominated by illite with subordinate smectite, no chlorite, and very low levels of kaolinite and mixed-layer clays; 2) post Eocene age erratics dominated by illite with a major component of chlorite and R=l US clay, minor or no smectite and kaolinite; and 3) post Eocene age erratics dominated by illite and containing R=3 US clay. Eocene age sediment occurs in either group and so had two distinct provenances for the clay fraction: a smectite-dominant area and an illite-rich, smectite-poor area. Post Eocene age sediment also had two distinct provenances for the clay fraction and are different from the Eocene sources: a metamorphic + ancient sedimentary terrain that supplied chlorite, illite, and R=l US clay to some of the erratics, and a sedimentary terrain that supplied illite and R=3 US clay. Kaolinite levels are low, indicating the absence of intense weathering and/or any significant contribution from the Beacon Supergroup.

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