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Articles 2731 - 2760 of 4541

Full-Text Articles in Earth Sciences

A Vegetation And Fire History Of Lake Titicaca Since The Last Glacial Maximum, Gina M. Paduano, Mark B. Bush, Paul A. Baker, Sherilyn C. Fritz, Geoffrey O. Seltzer May 2003

A Vegetation And Fire History Of Lake Titicaca Since The Last Glacial Maximum, Gina M. Paduano, Mark B. Bush, Paul A. Baker, Sherilyn C. Fritz, Geoffrey O. Seltzer

Department of Earth and Atmospheric Sciences: Faculty Publications

Fine-resolution fossil pollen and charcoal analyses reconstruct a vegetation and fire history in the area surrounding Lake Titicaca (3810 m, Peru/Bolivia) since ca. 27,500 cal yr BP (hereafter BP). Time control was based on 26 accelerator mass spectrometer (AMS) radiocarbon dates. Seventeen AMS dates and 155 pollen and charcoal samples between ca. 17,500 BP and ca. 3,100 BP allow a centennial-scale reconstruction of deglacial and early- to mid-Holocene events. Local and regional fire signals were based on the separation of two charcoal size fractions, ≥180 μm and 179–65 μm. Charcoal abundance correlated closely with the proportion of woody taxa present …

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Water Transfers And Marketing In Nebraska, J Michaeil Jess Apr 2003

Water Transfers And Marketing In Nebraska, J Michaeil Jess

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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2003 Changes To Water Transfer Law In Nebraska - Addendum, J Michael Jess Apr 2003

2003 Changes To Water Transfer Law In Nebraska - Addendum, J Michael Jess

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Geology, Groundwater Chemistry And Management Of The Dakota Aquifer In Nebraska, David C. Gosselin, F. Edwin Harvey, Charles A. Flowerday Apr 2003

Geology, Groundwater Chemistry And Management Of The Dakota Aquifer In Nebraska, David C. Gosselin, F. Edwin Harvey, Charles A. Flowerday

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Field Study Of Hydraulic Conductivity In A Heterogeneous Aquifer: Comparison Of Single-Borehole Measurements Using Different Instruments, Vitaly A. Zlotnik, Brian R. Zurbuchen Apr 2003

Field Study Of Hydraulic Conductivity In A Heterogeneous Aquifer: Comparison Of Single-Borehole Measurements Using Different Instruments, Vitaly A. Zlotnik, Brian R. Zurbuchen

Department of Earth and Atmospheric Sciences: Faculty Publications

This field study compares three techniques for estimating the vertical distribution of horizontal hydraulic conductivity Kr in a heterogeneous aquifer and evaluates possible support volume effects. The dipole flow test (DFT), multilevel slug test (MLST), and borehole flowmeter test (BFT) are based on different kinematic flow structures and the shape and the size of the support volumes. The experiment design employed an identical characteristic linear scale for all tests. Vertical profiles of Kr ranging up to 260 m/day from tested wells in an alluvial aquifer exhibit a strong correlation in spite of the differences between test hydraulics. Results …

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Moon Lake 11,000 Year Diatom-Inferred Salinity Data, Kathleen R. Laird, Sherilyn C. Fritz, Eric C. Grimm, P. G. Mueller Apr 2003

Moon Lake 11,000 Year Diatom-Inferred Salinity Data, Kathleen R. Laird, Sherilyn C. Fritz, Eric C. Grimm, P. G. Mueller

Department of Earth and Atmospheric Sciences: Faculty Publications

Estimates of past lake-water salinity from fossil diatom assemblages were used to infer past climatic conditions at Moon Lake, a climatically sensitive site in the northern Great Plains. A good correspondence between diatom-inferred salinity and historical records of mean annual precipitation minus evapotranspiration (P-ET) strongly suggests that the sedimentary record from Moon Lake can be used to reconstruct past climatic conditions. Century-scale analysis of the Holocene diatom record indicates four major hydrological periods: an early Holocene transition from an open freshwater system to a closed saline system by 7300 BP, which corresponds with a transition from spruce forest to deciduous …

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Water-Quality Assessment Of The Central Nebraska Basins-— Enering A New Decade, Ronald B. Zelt, Jill D. Frankforter Mar 2003

Water-Quality Assessment Of The Central Nebraska Basins-— Enering A New Decade, Ronald B. Zelt, Jill D. Frankforter

United States Geological Survey: Publications

In 2001, the U.S. Geological Survey’s (USGS) National Water- Quality Assessment (NAWQA) Program began its second decade of intensive water-quality assessments (Cycle II). NAWQA scientists plan to revisit 42 major river-basin and aquifer systems (called study units) that were assessed in the first decade (Gilliom and others, 2001).

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The Application Of A Diatom-Based Transfer Function To Evaluate Regional Water-Quality Trends In Minnesota Since 1970, J. M. Ramstack, Sherilyn C. Fritz, D. R. Engstrom, S. A. Heiskary Mar 2003

The Application Of A Diatom-Based Transfer Function To Evaluate Regional Water-Quality Trends In Minnesota Since 1970, J. M. Ramstack, Sherilyn C. Fritz, D. R. Engstrom, S. A. Heiskary

Department of Earth and Atmospheric Sciences: Faculty Publications

Significant population growth over the last three decades, as well as efforts to improve surface-water quality mandated by the Clean Water Act, potentially have had opposing influences on aquatic ecosystems in the U.S. Because historical data on water-quality trends are limited over this time period, we developed a diatom-based transfer function to reconstruct chloride, color, acid neutralizing capacity (ANC), total phosphorus (TP), and pH in 55 Minnesota lakes. The lakes span three different ecoregions, as well as the Twin Cities metropolitan area, and differ in their history of settlement and land use, and in surficial geology, climate, and vegetation. Lakes …

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Effects Of Holocene Climate Change On Mercury Deposition In Elk Lake, Minnesota: The Importance Of Eolian Transport In The Mercury Cycle, W.F. Cannon, Walter E. Dean, John H. Bullock Jr. Feb 2003

Effects Of Holocene Climate Change On Mercury Deposition In Elk Lake, Minnesota: The Importance Of Eolian Transport In The Mercury Cycle, W.F. Cannon, Walter E. Dean, John H. Bullock Jr.

United States Geological Survey: Staff Publications

Sediments in Elk Lake, Minnesota, consist of 10,400 varve layers that provide a precise chronology for Holocene fluctuations in climate and biota recorded in the strata. Progressively greater concentrations and accumulation rates of mercury since ca. A.D. 1875 reflect deposition of anthropogenic mercury additions to the atmosphere. Within the Holocene record are numerous short intervals in which mercury concentrations and accumulation rates exceed the modern values. The highest mercury concentrations formed ca. 8 ka, coincident with a rapid change from cool, moist conditions to warm, dry conditions. A related change in flora from pine forest to prairie caused destruction of …

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A Late Quaternary Record Of Eolian Silt Deposition In A Maar Lake, St. Michael Island, Western Alaska, Daniel R. Muhs, Thomas A. Ager, Josh Been, J. Platt Bradbury, Walter E. Dean Jan 2003

A Late Quaternary Record Of Eolian Silt Deposition In A Maar Lake, St. Michael Island, Western Alaska, Daniel R. Muhs, Thomas A. Ager, Josh Been, J. Platt Bradbury, Walter E. Dean

United States Geological Survey: Staff Publications

Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the mineral fraction of the lake sediments is not derived from the local basalt and is probably eolian. Silt deposition took place from at least the latter part of the …

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Inverse Modeling Of Btex Dissolution And Biodegradation At The Bemidji, Mn Crude-Oil Spill Site, Hedeff I. Essaid, Isabelle M. Cozzarelli, Robert P. Eganhouse, William N. Herkelrath, Barbara A. Bekins, Geoffrey N. Delin, Win Butler Jan 2003

Inverse Modeling Of Btex Dissolution And Biodegradation At The Bemidji, Mn Crude-Oil Spill Site, Hedeff I. Essaid, Isabelle M. Cozzarelli, Robert P. Eganhouse, William N. Herkelrath, Barbara A. Bekins, Geoffrey N. Delin, Win Butler

United States Geological Survey: Staff Publications

The U.S. Geological Survey (USGS) solute transport and biodegradation code BIOMOC was used in conjunction with the USGS universal inverse modeling code UCODE to quantify field-scale hydrocarbon dissolution and biodegradation at the USGS Toxic Substances Hydrology Program crude-oil spill research site located near Bemidji, MN. This inverse modeling effort used the extensive historical data compiled at the Bemidji site from 1986 to 1997 and incorporated a multicomponent transport and biodegradation model. Inverse modeling was successful when coupled transport and degradation processes were incorporated into the model and a single dissolution rate coefficient was used for all BTEX components. Assuming a …

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Entropy And Generalized Least Square Methods In Assessment Of The Regional Value Of Streamgages, Momcilo Markus, H. Vernon Knapp, Gary D. Tasker Jan 2003

Entropy And Generalized Least Square Methods In Assessment Of The Regional Value Of Streamgages, Momcilo Markus, H. Vernon Knapp, Gary D. Tasker

United States Geological Survey: Staff Publications

The Illinois State Water Survey performed a study to assess the streamgaging network in the State of Illinois. One of the important aspects of the study was to assess the regional value of each station through an assessment of the information transfer among gaging records for low, average, and high flow conditions. This analysis was performed for the main hydrologic regions in the State, and the stations were initially evaluated using a new approach based on entropy analysis. To determine the regional value of each station within a region, several information parameters, including total net information, were defined based on …

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Changes In The Timing Of High River Flows In New England Over The 20th Century, G. A. Hodgkins, R. W. Dudley, T. G. Huntington Jan 2003

Changes In The Timing Of High River Flows In New England Over The 20th Century, G. A. Hodgkins, R. W. Dudley, T. G. Huntington

United States Geological Survey: Staff Publications

The annual timing of river flows is a good indicator of climate-related changes, or lack of changes, for rivers with long-term data that drain unregulated basins with stable land use. Changes in the timing of annual winter/spring (January 1 to May 31) and fall (October 1 to December 31) center of volume dates were analyzed for 27 rural, unregulated river gaging stations in New England, USA with an average of 68 years of record. The center of volume date is the date by which half of the total volume of water for a given period of time flows past a …

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Red Willow County Test Hole Logs, Duane A. Eversoll Jan 2003

Red Willow County Test Hole Logs, Duane A. Eversoll

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Mid-Holocene Climates Of The Americas: A Dynamical Response To Changed Seasonality, S. P. Harrison, J. E. Kutzbach, Z. Liu, P. J. Bartlein, B. Otto-Bliesner, Daniel R. Muhs, I. C. Prentice, R. S. Thompson Jan 2003

Mid-Holocene Climates Of The Americas: A Dynamical Response To Changed Seasonality, S. P. Harrison, J. E. Kutzbach, Z. Liu, P. J. Bartlein, B. Otto-Bliesner, Daniel R. Muhs, I. C. Prentice, R. S. Thompson

United States Geological Survey: Staff Publications

Abstract Simulations of the climatic response to mid- Holocene (6 ka BP) orbital forcing with two coupled ocean–atmosphere models (FOAM and CSM) show enhancement of monsoonal precipitation in parts of the American Southwest, Central America and northernmost South America during Northern Hemisphere summer. The enhanced onshore flow that brings precipitation into Central America is caused by a northward displacement of the inter-tropical convergence zone, driven by cooling of the equatorial and warming of the northern subtropical and mid-latitude ocean. Ocean feedbacks also enhance precipitation over the American Southwest, although the increase in monsoon precipitation there is largely driven by increases …

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Monitoring Trends In Bat Populations Of The United States And Territories: Problems And Prospects, T.J. O'Shea, M. A. Bogan Jan 2003

Monitoring Trends In Bat Populations Of The United States And Territories: Problems And Prospects, T.J. O'Shea, M. A. Bogan

United States Geological Survey: Publications

Bats are ecologically and economically important mammals. The life histories of bats (particularly their low reproductive rates and the need for some species to gather in large aggregations at limited numbers of roosting sites) make their populations vulnerable to declines. Many of the species of bats in the United States (U.S.) and territories are categorized as endangered or threatened, have been candidates for such categories, or are considered species of concern. The importance and vulnerability of bat populations makes monitoring trends in their populations a goal for their future management. However, scientifically rigorous monitoring of bat populations requires well-planned, statistically …

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Geologic Studies Of Mercury By The U.S. Geological Survey Jan 2003

Geologic Studies Of Mercury By The U.S. Geological Survey

United States Geological Survey: Publications

A liquid at room temperature, mercury is a unique metal with unusual properties. Elemental mercury has long been used in thermometers because it responds to changes in temperature. In fact, mercury’s many diverse properties have made it useful for many products. Mercury is a good metallic conductor with a low electrical resistivity; it has been used in electrical products including electrical wiring and switches, fluorescent lamps, mercury batteries, and thermostats (Eisler, 1987). Mercury also is used in navigational instruments to measure changes in temperature and pressure. In the medical field, mercury is used as a component in dental fillings and …

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Review Of Population Viability Analysis, Mark W. Miller Jan 2003

Review Of Population Viability Analysis, Mark W. Miller

United States Geological Survey: Staff Publications

Population viability analysis (PVA) historically has been used to estimate the probability that a population will become extinct within a given time period. More recently, PVA has been used to evaluate alternative management strategies. Some might even say PVA gave rise to conservation biology. Nevertheless, PVA has been heavily criticized. This is the second book to present a synthesis and address those concerns. It does so extremely well.

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Genetic Variation In Black Bears In Arkansas And Louisiana Using Microsatellite Dna Markers, Ildiki Csiki, Cynthia Lam, Audie Key, Erica Coulter, Joseph D. Clark, Richard M. Pace Iii, Kimberley G. Smith, Douglas D. Rhoads Jan 2003

Genetic Variation In Black Bears In Arkansas And Louisiana Using Microsatellite Dna Markers, Ildiki Csiki, Cynthia Lam, Audie Key, Erica Coulter, Joseph D. Clark, Richard M. Pace Iii, Kimberley G. Smith, Douglas D. Rhoads

United States Geological Survey: Staff Publications

In the 1950s and 1960s, translocation projects reintroduced black bears (Ursus americanus) from Minnesota and Manitoba to Arkansas and Louisiana. Today, several geographically disconnected populations exist in Arkansas and Louisiana, but their origins are unclear. Some populations may represent a separate subspecies, U. a. luteolus, which is federally protected. We characterized 5 microsatellite loci in 5 isolated populations in Arkansas and Louisiana and compared them with genotypes from Minnesota. Our data indicate that bears of the Ozark and Ouachita mountains of Arkansas, an inland area of Louisiana, and those of Minnesota are similar in overall genetic diversity …

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Evidence For Disease-Related Amphibian Decline In Colorado, Erin Muths, Paul Stephen Corn, Allan P. Pessier, D. Earl Green Jan 2003

Evidence For Disease-Related Amphibian Decline In Colorado, Erin Muths, Paul Stephen Corn, Allan P. Pessier, D. Earl Green

United States Geological Survey: Staff Publications

The recent discovery of a pathogenic fungus (Batrachochytrium dendrobatidis) associated with declines of frogs in the American and Australian tropics, suggests that at least the proximate cause, may be known for many previously unexplained amphibian declines. We have monitored boreal toads in Colorado since 1991 at four sites using capture–recapture of adults and counts of egg masses to examine the dynamics of this metapopulation. Numbers of male toads declined in 1996 and 1999 with annual survival rate averaging 78% from 1991 to 1994, 45% in 1995 and 3% between 1998 and 1999. Numbers of egg masses also declined. …

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Unprecedented Last-Glacial Mass Accumulation Rates Determined By Luminescence Dating Of Loess From Western Nebraska, Helen M. Roberts, Daniel R. Muhs, Ann G. Wintle, Geoff A. T. Duller, E. Arthur Bettis Iii Jan 2003

Unprecedented Last-Glacial Mass Accumulation Rates Determined By Luminescence Dating Of Loess From Western Nebraska, Helen M. Roberts, Daniel R. Muhs, Ann G. Wintle, Geoff A. T. Duller, E. Arthur Bettis Iii

United States Geological Survey: Staff Publications

A high-resolution chronology for Peoria (last glacial period) Loess from three sites in Nebraska, midcontinental North America, is determined by applying optically stimulated luminescence (OSL) dating to 35–50 µm quartz. At Bignell Hill, Nebraska, an OSL age of 25,000 yr near the contact of Peoria Loess with the underlying Gilman Canyon Formation shows that dust accumulation occurred early during the last glacial maximum (LGM), whereas at Devil’s Den and Eustis, Nebraska, basal OSL ages are significantly younger (18,000 and 21,000 yr, respectively). At all three localities, dust accumulation ended at some time after 14,000 yr ago. Mass accumulation rates …

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Stratigraphy And Palaeoclimatic Significance Of Late Quaternary Loess–Palaeosol Sequences Of The Last Interglacial–Glacial Cycle In Central Alaska, Daniel R. Muhs, Thomas A. Ager, E. Arthur Bettis Iii, John Mcgeehin, Josh M. Been, James E. Begét, Milan J. Pavich, Thomas W. Stafford Jr., De Anne S. P. Stevens Jan 2003

Stratigraphy And Palaeoclimatic Significance Of Late Quaternary Loess–Palaeosol Sequences Of The Last Interglacial–Glacial Cycle In Central Alaska, Daniel R. Muhs, Thomas A. Ager, E. Arthur Bettis Iii, John Mcgeehin, Josh M. Been, James E. Begét, Milan J. Pavich, Thomas W. Stafford Jr., De Anne S. P. Stevens

United States Geological Survey: Staff Publications

Loess is one of the most widespread subaerialdeposits in Alaska and adjacent Yukon Territory and may have a history that goes back 3 Ma. Based on mineralogy and major and trace element chemistry, central Alaskan loess has a composition that is distinctive from other loess bodies of the world, although it is quartz-dominated. Central Alaskan loess was probably derived from a variety of rock types, including granites, metabasalts and schists. Detailed stratigraphic data and pedologic criteria indicate that, contrary to early studies, many palaeosols are present in central Alaskan loess sections. The buried soils indicate that loess sedimentation was episodic, …

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High Precision Earthquake Locations Reveal Seismogenic Structure Beneath Mammoth Mountain, California, Stephanie Prejean, Anna Stork, William Ellsworth, David Hill, Bruce Julian Jan 2003

High Precision Earthquake Locations Reveal Seismogenic Structure Beneath Mammoth Mountain, California, Stephanie Prejean, Anna Stork, William Ellsworth, David Hill, Bruce Julian

United States Geological Survey: Staff Publications

In 1989, an unusual earthquake swarm occurred beneath Mammoth Mountain that was probably associated with magmatic intrusion. To improve our understanding of this swarm, we relocated Mammoth Mountain earthquakes using a double difference algorithm. Relocated hypocenters reveal that most earthquakes occurred on two structures, a near-vertical plane at 7–9 km depth that has been interpreted as an intruding dike, and a circular ring-like structure at ~5.5 km depth, above the northern end of the inferred dike. Earthquakes on this newly discovered ring structure form a conical section that dips outward away from the aseismic interior. Fault-plane solutions indicate that in …

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Imaging The Complexity Of An Active Normal Fault System: The 1997 Colfiorito (Central Italy) Case Study, L. Chiaraluce, W. L. Ellseworth, C. Chiarabba, M. Cocco Jan 2003

Imaging The Complexity Of An Active Normal Fault System: The 1997 Colfiorito (Central Italy) Case Study, L. Chiaraluce, W. L. Ellseworth, C. Chiarabba, M. Cocco

United States Geological Survey: Staff Publications

Six moderate magnitude earthquakes (5 < Mw < 6) ruptured normal fault segments of the southern sector of the North Apennine belt (central Italy) in the 1997 Colfiorito earthquake sequence. We study the progressive activation of adjacent and nearby parallel faults of this complex normal fault system using ~1650 earthquake locations obtained by applying a double-difference location method, using travel time picks and waveform cross-correlation measurements. The lateral extent of the fault segments range from 5 to 10 km and make up a broad, ~45 km long, NW trending fault system. The geometry of each segment is quite simple and consists of planar faults gently dipping toward SW with an average dip of 40 °–45 °. The fault planes are not listric but maintain a constant dip through the entire seismogenic volume, down to 8 km depth. We observe the activation of faults on the hanging wall and the absence of seismicity in the footwall of the structure. The observed fault segmentation appears to be due to the lateral heterogeneity of the upper crust: preexisting thrusts inherited from Neogene’s compressional tectonic intersect the active normal faults and control their maximum length. The stress tensor obtained by inverting the six main shock focal mechanisms of the sequence is in agreement with the tectonic stress active in the inner chain of the Apennine, revealing a clear NE trending extension direction. Aftershock focal mechanisms show a consistent extensional kinematics, 70% of which are mechanically consistent with the main shock stress field.

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Mapping Vegetation In Yellowstone National Park Using Spectral Feature Analysis Of Aviris Data, Raymond F. Kokaly, Don G. Despain, Roger N. Clark, K. Eric Livo Jan 2003

Mapping Vegetation In Yellowstone National Park Using Spectral Feature Analysis Of Aviris Data, Raymond F. Kokaly, Don G. Despain, Roger N. Clark, K. Eric Livo

United States Geological Survey: Staff Publications

Knowledge of the distribution of vegetation on the landscape can be used to investigate ecosystem functioning. The sizes and movements of animal populations can be linked to resources provided by different plant species. This paper demonstrates the application of imaging spectroscopy to the study of vegetation in Yellowstone National Park (Yellowstone) using spectral feature analysis of data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). AVIRIS data, acquired on August 7, 1996, were calibrated to surface reflectance using a radiative transfer model and field reflectance measurements of a ground calibration site. A spectral library of canopy reflectance signatures was created by …

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Interplay Of Late Cenozoic Siliciclastic Supply And Carbonate Response On The Southeast Florida Platform, Kevin J. Cunningham, Stanley D. Locker, Albert C. Hine, David Bukry, Laura A. Guertin, John A. Barron Jan 2003

Interplay Of Late Cenozoic Siliciclastic Supply And Carbonate Response On The Southeast Florida Platform, Kevin J. Cunningham, Stanley D. Locker, Albert C. Hine, David Bukry, Laura A. Guertin, John A. Barron

United States Geological Survey: Staff Publications

High-resolution seismic-reflection data collected along the length of the Caloosahatchee River in southwestern Florida have been correlated to nannofossil biostratigraphy and strontium-isotope chemostratigraphy at six continuously cored boreholes. These data are interpreted to show a major Late Miocene(?) to Early Pliocene fluvial– deltaic depositional system that prograded southward across the carbonate Florida Platform, interrupting nearly continuous carbonate deposition since early in the Cretaceous. Connection of the platform top to a continental source of siliciclastics and significant paleotopography combined to focus accumulation of an immense supply of siliciclastics on the southeastern part of the Florida Platform. The remarkably thick (> 100 …

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Paleolimnology Of Lake Tanganyika, East Africa, Over The Past 100 K Yr, Christopher A. Scholz, John W. King, Geoffrey S. Ellis, Peter K. Swart, J. Curt Stager, Steven M. Colman Jan 2003

Paleolimnology Of Lake Tanganyika, East Africa, Over The Past 100 K Yr, Christopher A. Scholz, John W. King, Geoffrey S. Ellis, Peter K. Swart, J. Curt Stager, Steven M. Colman

United States Geological Survey: Staff Publications

New sediment core data from a unique slow-sedimentation rate site in Lake Tanganyika contain a much longer and continuous record of limnological response to climate change than have been previously observed in equatorial regions of central Africa. The new core site was first located through an extensive seismic reflection survey over the Kavala Island Ridge (KIR), a sedimented basement high that separates the Kigoma and Kalemie Basins in Lake Tanganyika.

Proxy analyses of paleoclimate response carried out on core T97-52V include paleomagnetic and index properties, TOC and isotopic analyses of organic carbon, and diatom and biogenic silica analyses. A robust …

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Trace Elements In Lesser Scaup (Aythya Affinis) From The Mississippi Flyway, Christine Custer, Thomas Custer, Michael J. Anteau, Alan D. Afton, David Wooten Jan 2003

Trace Elements In Lesser Scaup (Aythya Affinis) From The Mississippi Flyway, Christine Custer, Thomas Custer, Michael J. Anteau, Alan D. Afton, David Wooten

United States Geological Survey: Staff Publications

Previous research reported that concentrations of selenium in the livers of 88-95% of lesser scaup from locations in Lake Erie, Lake St. Clair, and Lake Michigan, USA were either elevated (10-33 μg/g dry weight [dw]) or in the potentially harmful range (>33 μg/g dw). In order to determine the geographic extent of these high selenium concentrations, we collected lesser scaup in Louisiana, Arkansas, Illinois, Minnesota, Wisconsin, and Manitoba and analyzed the livers for 19 trace elements. We found that all trace element concentrations, except for selenium, generally were low. Arsenic, which usually is not detected in liver samples, was …

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Strontium Isotope Geochemistry In The Central Part Of The Great Plains (Dakota) Aquifer, U.S.A.. Applied Geochemistry, D. C. Gosselin, F. E. Harvey, C. Frost, R. Stotler, P. A. Macfarlane Jan 2003

Strontium Isotope Geochemistry In The Central Part Of The Great Plains (Dakota) Aquifer, U.S.A.. Applied Geochemistry, D. C. Gosselin, F. E. Harvey, C. Frost, R. Stotler, P. A. Macfarlane

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Late Albian Adaptive Radiation In The Calcareous Nannofossil Genus Eiffellithus, David K. Watkins, James A. Bergen Jan 2003

Late Albian Adaptive Radiation In The Calcareous Nannofossil Genus Eiffellithus, David K. Watkins, James A. Bergen

Department of Earth and Atmospheric Sciences: Faculty Publications

Well preserved nannofossil assemblages in upper Albian and lower Cenomanian hemipelagic sections from Ocean Drilling Program (ODP) Leg 171B preserve a record of the early history and adaptive radiation of the genus Eiffellithus. Seven distinct taxa are recognized and differentiated, with one previously named taxon (E. monechiae) emended and four new species described: E. praestigium, E. vonsalisiae, E. equibiramus, and E. parvus. Sample census data indicate that most species evolved, rose to dominance, and then rapidly declined to extinction, to be replaced by other members of the genus. Newly evolved species tended to remain at low …

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