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United States Geological Survey: Staff Publications

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Articles 661 - 690 of 1026

Full-Text Articles in Earth Sciences

Paleolimnology And Paleoclimate Studies In Upper Klamath Lake, Oregon, Steven M. Colman, J. Platt Bradbury, Joseph G. Rosenbaum Jan 2004

Paleolimnology And Paleoclimate Studies In Upper Klamath Lake, Oregon, Steven M. Colman, J. Platt Bradbury, Joseph G. Rosenbaum

United States Geological Survey: Staff Publications

The subsiding Upper Klamath Lake Basin contains sediments that were continuously deposited in a shallow, freshwater lake for more than 40 000 years. Well dated by radiometric methods and containing volcanic ashes of known age, these sediments constitute a valuable paleoclimate record. Sediment constituents and properties that reflect past climatic conditions in the area include pollen, diatoms, sediment geochemistry, and sediment magnetic properties. Many of these proxy measurements are also useful for comparing natural conditions in the lake to conditions following human settlement. Because of its location, the paleoclimate record from Upper Klamath Lake is valuable for comparisons to offshore …

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Quaternary Sea-Level History Of The United States, Daniel R. Muhs, John F. Wehmiller, Kathleen R. Simmons, Linda L. York Jan 2004

Quaternary Sea-Level History Of The United States, Daniel R. Muhs, John F. Wehmiller, Kathleen R. Simmons, Linda L. York

United States Geological Survey: Staff Publications

In the past 30 years, there have been tremendous advances in our understanding of Quaternary sea-level history, due directly to developments in Quaternary dating methods, particularly uranium-series disequilibrium and amino acid racemization. Another reason for this progress is that coastline history can now be tied to the oxygen-isotope record of foraminifera in deep-sea cores. Furthermore, both records have been linked to climate change on the scale of glacial-interglacial cycles that are thought to be forced by changes in Earth-Sun geometry, or “orbital forcing” (Milankovitch, 1941).

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Genetic Identification Of Spotted Owls, Barred Owls, And Their Hybrids: Legal Implications Of Hybrid Identity, Susan M. Haig, Thomas D. Mullins, Eric D. Forsman, Pepper W. Trail, Liv Wennerberg Jan 2004

Genetic Identification Of Spotted Owls, Barred Owls, And Their Hybrids: Legal Implications Of Hybrid Identity, Susan M. Haig, Thomas D. Mullins, Eric D. Forsman, Pepper W. Trail, Liv Wennerberg

United States Geological Survey: Staff Publications

Recent population expansion of Barred Owls (Strix varia) into western North America has led to concern that they may compete with and further harm the Northern Spotted Owl (S. occidentalis caurina), which is already listed as threatened under the U.S. Endangered Species Act (ESA). Because they hybridize, there is a legal need under the ESA for forensic identification of both species and their hybrids. We used mitochondrial control-region DNA and amplified fragment-length polymorphism (AFLP) analyses to assess maternal and biparental gene flow in this hybridization process. Mitochondrial DNA sequences (524 base pairs) indicated large divergence between …

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Subspecific Relationships And Genetic Structure In The Spotted Owl, Susan M. Haig, Thomas D. Mullins, Eric D. Forsman Jan 2004

Subspecific Relationships And Genetic Structure In The Spotted Owl, Susan M. Haig, Thomas D. Mullins, Eric D. Forsman

United States Geological Survey: Staff Publications

Hierarchical genetic structure was examined in the three geographically-defined subspecies of spotted owl (Strix occidentalis) to define relationships among subspecies and quantify variation within and among regional and local populations. Sequences (522 bp) from domains I and II of the mitochondrial control region were analyzed for 213 individuals from 30 local breeding areas. Results confirmed significant differences between northern spotted owls and the other traditional geographically defined subspecies but did not provide support for subspecific level differences between California and Mexican spotted owls. Divergence times among subspecies estimated with a 936 bp portion of the cytochrome b gene …

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An Association Of Benthic Foraminifera And Gypsum In Holocene Sediments Of Estuarine Chesapeake Bay, Usa, John Cann, Thomas Cronin Jan 2004

An Association Of Benthic Foraminifera And Gypsum In Holocene Sediments Of Estuarine Chesapeake Bay, Usa, John Cann, Thomas Cronin

United States Geological Survey: Staff Publications

Two cores of Holocene sediments recovered from the Cape Charles Channel of Chesapeake Bay yielded radiocarbon ages of about 6.8 to 5.8 ka for the lower intervals. Fossil foraminifera preserved in these lower sediments are dominated by species of Elphidium, which make up about 90% of the assemblage throughout, and probably signify deposition in hypersaline waters. Buccella frigida and Ammonia beccarii are the only other species commonly present. Hypersalinity of bottom waters seems to have been maintained by water-density stratification in a basin-like section of the channel. In core PTXT -4-P-I transition to modem Chesapeake conditions, in which numbers …

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Fine-Scale Structure Of The San Andreas Fault Zone And Location Of The Safod Target Earthquakes, C. Thurber, S. Roecker, H. Zhang, S. Baher, W. Ellsworth Jan 2004

Fine-Scale Structure Of The San Andreas Fault Zone And Location Of The Safod Target Earthquakes, C. Thurber, S. Roecker, H. Zhang, S. Baher, W. Ellsworth

United States Geological Survey: Staff Publications

We present results from the tomographic analysis of seismic data from the Parkfield area using three different inversion codes. The models provide a consistent view of the complex velocity structure in the vicinity of the San Andreas, including a sharp velocity contrast across the fault. We use the inversion results to assess our confidence in the absolute location accuracy of a potential target earthquake. We derive two types of accuracy estimates, one based on a consideration of the location differences from the three inversion methods, and the other based on the absolute location accuracy of ‘‘virtual earthquakes.’’ Location differences are …

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Streaks, Multiplets, And Holes: High-Resolution Spatio-Temporal Behavior Of Parkfield Seismicity, F. Waldhauser, W. L. Ellsworth, D. P. Schaff, A. Cole Jan 2004

Streaks, Multiplets, And Holes: High-Resolution Spatio-Temporal Behavior Of Parkfield Seismicity, F. Waldhauser, W. L. Ellsworth, D. P. Schaff, A. Cole

United States Geological Survey: Staff Publications

Double-difference locations of ~8000 earthquakes from 1969–2002 on the Parkfield section of the San Andreas Fault reveal detailed fault structures and seismicity that is, although complex, highly organized in both space and time. Distinctive features of the seismicity include: 1) multiple recurrence of earthquakes of the same size at precisely the same location on the fault (multiplets), implying frictional or geometric controls on their location and size; 2) sub-horizontal alignments of hypocenters along the fault plane (streaks), suggestive of rheological transitions within the fault zone and/or stress concentrations between locked and creeping areas; 3) regions devoid of microearthquakes with typical …

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Introduction To Special Section: Preparing For The San Andreas Fault Observatory At Depth, Stephen Hickman, Mark D. Zoback, William Ellsworth Jan 2004

Introduction To Special Section: Preparing For The San Andreas Fault Observatory At Depth, Stephen Hickman, Mark D. Zoback, William Ellsworth

United States Geological Survey: Staff Publications

The San Andreas Fault Observatory at Depth (SAFOD) is a comprehensive project to drill into the hypocentral zone of repeating M ~ 2 earthquakes on the San Andreas Fault at a depth of about 3 km. The goals of SAFOD are to establish a multi-stage geophysical observatory in close proximity to these repeating earthquakes, to carry out a comprehensive suite of downhole measurements in order to study the physical and chemical conditions under which earthquakes occur and to exhume rock and fluid samples for extensive laboratory studies. In the vicinity of SAFOD, the San Andreas is moving through a combination …

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Stress Orientations And Magnitudes In The Safod Pilot Hole, Stephen Hickman, Mark D. Zoback Jan 2004

Stress Orientations And Magnitudes In The Safod Pilot Hole, Stephen Hickman, Mark D. Zoback

United States Geological Survey: Staff Publications

Borehole breakouts and drilling-induced tensile fractures in the 2.2-km-deep SAFOD pilot hole at Parkfield, CA, indicate significant local variations in the direction of the maximum horizontal compressive stress, SHmax, but show a generalized increase in the angle between SHmax and the San Andreas Fault with depth. This angle ranges from a minimum of 25 ± 10 ° at 1000–1150 m to a maximum of 69 ± 14 ° at 2050–2200 m. The simultaneous occurrence of tensile fractures and borehole breakouts indicates a transitional strike-slip to reverse faulting stress regime with high horizontal differential stress, although there is considerable uncertainty in …

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Stress-Induced, Time-Dependent Fracture Closure At Hydrothermal Conditions, N. M. Beeler, S. H. Hickman Jan 2004

Stress-Induced, Time-Dependent Fracture Closure At Hydrothermal Conditions, N. M. Beeler, S. H. Hickman

United States Geological Survey: Staff Publications

Time-dependent closure of fractures in quartz was measured in situ at 22–530 °C temperature and 0.1–150 MPa water pressure. Unlike previous crack healing and rock permeability studies, in this study, fracture aperture is monitored directly and continuously using a windowed pressure vessel, a long-working-distance microscope, and reflectedlight interferometry. Thus the fracture volume and geometry can be measured as a function of time, temperature, and water pressure. Relatively uniform closure occurs rapidly at temperatures and pressures where quartz becomes significantly soluble in water. During closure the aperture is reduced by as much as 80% in a few hours. We infer that …

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In Situ Stress, Fracture, And Fluid Flow Analysis In Well 38c-9: An Enhanced Geothermal System In The Coso Geothermal Field, Judith M. Sheridan, Stephen H. Hickman Jan 2004

In Situ Stress, Fracture, And Fluid Flow Analysis In Well 38c-9: An Enhanced Geothermal System In The Coso Geothermal Field, Judith M. Sheridan, Stephen H. Hickman

United States Geological Survey: Staff Publications

Geoscientists from the Coso Operating Company, EGI-Utah, GeoMechanics International, and the United States Geological Survey are cooperating in a multi-year study to develop an Enhanced Geothermal System (EGS) in the Coso Geothermal Field. Key to the creation of an EGS is an understanding of the relationship among natural fracture distribution, fluid flow, and the ambient tectonic stresses that exist within the resource in order to design a hydraulic and thermal stimulation of an east-flank injection well, the first step in the creation of a heat exchanger at depth. Well datasets from the east flank of the Coso Geothermal Field are …

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Persistence Of Pharmaceutical Compounds And Other Organic Wastewater Contaminants In A Conventional Drinking-Water-Treatment Plant, Paul E. Stackelberg, Edward T. Furlong, Michael T. Meyer, Steven D. Zaugg, Alden K. Henderson, Dori B. Reissman Jan 2004

Persistence Of Pharmaceutical Compounds And Other Organic Wastewater Contaminants In A Conventional Drinking-Water-Treatment Plant, Paul E. Stackelberg, Edward T. Furlong, Michael T. Meyer, Steven D. Zaugg, Alden K. Henderson, Dori B. Reissman

United States Geological Survey: Staff Publications

In a study conducted by the US Geological Survey and the Centers for Disease Control and Prevention, 24 water samples were collected at selected locations within a drinking-water-treatment (DWT) facility and from the two streams that serve the facility to evaluate the potential for wastewater-related organic contaminants to survive a conventional treatment process and persist in potable-water supplies. Stream-water samples as well as samples of raw, settled, filtered, and finished water were collected during low-flow conditions, when the discharge of effluent from upstream municipal sewage-treatment plants accounted for 37–67% of flow in stream 1 and 10–20% of flow in stream …

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Uranium-Series Coral Ages From The Us Atlantic Coastal Plain–The ‘‘80 Ka Problem’’ Revisited, John F. Wehmiller, Kathleen R. Simmons, Hai Cheng, R. Lawrence Edwards, Jamie Martin-Mcnaughton, Linda L. York, David E. Krantz, Chuan-Chou Shen Jan 2004

Uranium-Series Coral Ages From The Us Atlantic Coastal Plain–The ‘‘80 Ka Problem’’ Revisited, John F. Wehmiller, Kathleen R. Simmons, Hai Cheng, R. Lawrence Edwards, Jamie Martin-Mcnaughton, Linda L. York, David E. Krantz, Chuan-Chou Shen

United States Geological Survey: Staff Publications

Uranium series coral ages for emergent units from the passive continental margin US Atlantic Coastal Plain (ACP) suggest sea level above present levels at the end of marine oxygen isotope stage (MIS) 5, contradicting age-elevation relations based on marine isotopic or coral reef models of ice equivalent sea level. We have reexamined this problem by obtaining high precision 230Th/238U and 231Pa/235U thermal ionization mass spectrometric ages for recently collected and carefully cleaned ACPcorals, many in situ. We recognize samples that show no evidence for diagenesis on the basis of uranium isotopic composition and age …

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Testing Density-Dependent Groundwater Models: Two-Dimensional Steady State Unstable Convection In Infinite, Finite And Inclined Porous Layers, Douglas Weatherill, Craig T. Simmons, Clifford I. Voss, Neville I. Robinson Jan 2004

Testing Density-Dependent Groundwater Models: Two-Dimensional Steady State Unstable Convection In Infinite, Finite And Inclined Porous Layers, Douglas Weatherill, Craig T. Simmons, Clifford I. Voss, Neville I. Robinson

United States Geological Survey: Staff Publications

This study proposes the use of several problems of unstable steady state convection with variable fluid density in a porous layer of infinite horizontal extent as two-dimensional (2-D) test cases for density-dependent groundwater flow and solute transport simulators. Unlike existing density-dependent model benchmarks, these problems have well-defined stability criteria that are determined analytically. These analytical stability indicators can be compared with numerical model results to test the ability of a code to accurately simulate buoyancy driven flow and diffusion. The basic analytical solution is for a horizontally infinite fluid-filled porous layer in which fluid density decreases with depth. The proposed …

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Holocene Loess Deposition And Soil Formation As Competing Processes, Matanuska Valley, Southern Alaska, Daniel R. Muhs, John P. Mcgeehin, Jossh Beann, Eric Fisher Jan 2004

Holocene Loess Deposition And Soil Formation As Competing Processes, Matanuska Valley, Southern Alaska, Daniel R. Muhs, John P. Mcgeehin, Jossh Beann, Eric Fisher

United States Geological Survey: Staff Publications

Although loess–paleosol sequences are among the most important records of Quaternary climate change and past dust deposition cycles, few modern examples of such sedimentation systems have been studied. Stratigraphic studies and 22 new accelerator mass spectrometry radiocarbon ages from the Matanuska Valley in southern Alaska show that loess deposition there began sometime after ~6500 14C yr B.P. and has continued to the present. The silts are produced through grinding by the Matanuska and Knik glaciers, deposited as outwash, entrained by strong winds, and redeposited as loess. Over a downwind distance of ~40 km, loess thickness, sand content, and sand-pluscoarse- …

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Great Plains Ecosystems: Past, Present, And Future, Fred B. Samson, Fritz L. Knopf, Wayne Ostlie Jan 2004

Great Plains Ecosystems: Past, Present, And Future, Fred B. Samson, Fritz L. Knopf, Wayne Ostlie

United States Geological Survey: Staff Publications

Little questions exists that the main bodies of North American prairie (i.e., the tall-grass, mixed, and shortgrass) are among the most endangered resources on the continent. The purpose of this paper is to provide a past and present biological base- line by which to understand North American prairies and to provide a platform for future conservation. Events both immediate to the end of the Pleistocene and historic suggest that the present grassland conditions are different from those within which most of the grassland organisms evolved. Our analysis suggests that few grassland landscapes remain adequate in area and distribution to sustain …

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Ancient Maize From Chacoan Great Houses: Where Was It Grown?, Larry Benson, Linda Cordell, Kirk Vincent, Howard E. Taylor, John Stein, G. Lang Farmer, U.S. Geological Survey Oct 2003

Ancient Maize From Chacoan Great Houses: Where Was It Grown?, Larry Benson, Linda Cordell, Kirk Vincent, Howard E. Taylor, John Stein, G. Lang Farmer, U.S. Geological Survey

United States Geological Survey: Staff Publications

In this article, we compare chemical (87Sr/86Sr and elemental) analyses of archaeological maize from dated contexts within Pueblo Bonito, Chaco Canyon, New Mexico, to potential agricultural sites on the periphery of the San Juan Basin. The oldest maize analyzed from Pueblo Bonito probably was grown in an area located 80 km to the west at the base of the Chuska Mountains. The youngest maize came from the San Juan or Animas river floodplains 90 km to the north. This article demonstrates that maize, a dietary staple of southwestern Native Americans, was transported over considerable distances in …

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Spatial And Temporal Variability In The Amount And Source Of Dissolved Organic Carbon: Implications For Ultraviolet Exposure In Amphibian Habitats, Paul D. Brooks, Catherine M. O'Reilly, Stephen A. Diamond, Don H. Campbell, Roland Knapp, David Bradford, Paul Stephen Corn, Blake Hossack, Kathy Tonnessen Aug 2003

Spatial And Temporal Variability In The Amount And Source Of Dissolved Organic Carbon: Implications For Ultraviolet Exposure In Amphibian Habitats, Paul D. Brooks, Catherine M. O'Reilly, Stephen A. Diamond, Don H. Campbell, Roland Knapp, David Bradford, Paul Stephen Corn, Blake Hossack, Kathy Tonnessen

United States Geological Survey: Staff Publications

The amount, chemical composition, and source of dissolved organic carbon (DOC), together with in situ ultraviolet (UV-B) attenuation, were measured at 1–2 week intervals throughout the summers of 1999, 2000, and 2001 at four sites in Rocky Mountain National Park (Colorado). Eight additional sites, four in Sequoia and Kings Canyon National Park/John Muir Wilderness (California) and four in Glacier National Park (Montana), were sampled during the summer of 2000. Attenuation of UV-B was significantly related to DOC concentrations over the three years in Rocky Mountain (R2 = 0.39, F = 25.71, P < 0.0001) and across all parks in 2000 (R2 = 0.44, F = 38.25, P …

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Landscape Change In The Southern Piedmont: Challenges, Solutions, And Uncertainty Across Scales, Michael J. Conroy, Craig R. Allen, James T. Peterson, Lowell Pritchard, Clinton T. Moore Aug 2003

Landscape Change In The Southern Piedmont: Challenges, Solutions, And Uncertainty Across Scales, Michael J. Conroy, Craig R. Allen, James T. Peterson, Lowell Pritchard, Clinton T. Moore

United States Geological Survey: Staff Publications

The southern Piedmont of the southeastern United States epitomizes the complex and seemingly intractable problems and hard decisions that result from uncontrolled urban and suburban sprawl. Here we consider three recurrent themes in complicated problems involving complex systems: (1) scale dependencies and cross-scale, often nonlinear relationships; (2) resilience, in particular the potential for complex systems to move to alternate stable states with decreased ecological and/or economic value; and (3) uncertainty in the ability to understand and predict outcomes, perhaps particularly those that occur as a result of human impacts. We consider these issues in the context of landscape-level decision making, …

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Are Veterinary Medicines Causing Environmental Risks?, Alistair Boxall, Dana Kolpin, Bent Holling-Sorensen, Johannes Tolls Aug 2003

Are Veterinary Medicines Causing Environmental Risks?, Alistair Boxall, Dana Kolpin, Bent Holling-Sorensen, Johannes Tolls

United States Geological Survey: Staff Publications

Recently, low levels of veterinary medicines have been detected worldwide in soils, surface waters, and groundwaters (1,2). Although the impacts of selected compounds – most notably anthelmintics and selected antibacterial compounds – have been extensively investigated (3,4), many other substances found int the environment are less publicly well understood. As a result, researches have raised questions about the impact of veterinary medicines on organisms in the environment and on human health. Several key questions will be addressed in this article. What other veterinary medicines might be in the environment, and should we be concerned about these? How do these substances …

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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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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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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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