Open Access. Powered by Scholars. Published by Universities.®

Earth Sciences Commons™

Open Access. Powered by Scholars. Published by Universities.®

2014

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 931 - 960 of 1044

Full-Text Articles in Earth Sciences

Analysis Of A Sponge Bioherm From The Hermosa Group, Molas Lake Area, Colorado, Joanna Hamilton Jan 2014

Analysis Of A Sponge Bioherm From The Hermosa Group, Molas Lake Area, Colorado, Joanna Hamilton

Honors Projects

The Hermosa Group is a Pennsylvanian (~310 Ma) rock package found in the southwestern San Juan Mountains and the Paradox Basin. The Paradox Basin was an evaporite basin in which alternating carbonate, sandstone and siltstone layers were deposited at the margins. Within the carbonate layers, ancient phylloid algal mounds and sponge bioherms can be found. In this project I document fossil sponges and algae from a Hermosa Group locality in southwestern Colorado. I look at the environments in which the sponges lived, those being relatively deep water, above wave-base; as well as inter-sponge growth habits, where one is dominant and …

Go to article

Dune Formation On Late Holocene Sandy Bay Barriers Along Lake Michigan’S Door Peninsula: The Importance Of Increased Sediment Supply Following The Nipissing And Algoma High Lake-Level Phases, J. Elmo Rawling Iii, Paul R. Hanson Jan 2014

Dune Formation On Late Holocene Sandy Bay Barriers Along Lake Michigan’S Door Peninsula: The Importance Of Increased Sediment Supply Following The Nipissing And Algoma High Lake-Level Phases, J. Elmo Rawling Iii, Paul R. Hanson

Department of Earth and Atmospheric Sciences: Faculty Publications

This study focuses on the geomorphology and geochronology of dunes formed on three sandy barrier systems at Clark, Europe and Kangaroo Lakes in Wisconsin’s Door Peninsula. The Lake Michigan shoreline in the peninsula contains abundant evidence for fluctuations in lake level with paleo-shoreline features that lie up to ~7 m above the present shoreline. Dunes are not very common along the Lake Michigan shoreline in Wisconsin, but the three bay barriers studied contain beach ridges that were buried by varying depths of eolian sand in the form of low relief sandsheets as well as parabolic and transverse dunes that have …

Go to article

A Numerical Testbed For Remote Sensing Of Aerosols, And Its Demonstration For Evaluating Retrieval Synergy From A Geostationary Satellite Constellation Of Geo-Cape And Goes-R, Jun Wang, Xiaoguang Xu, Shouguo Ding, Jing Zeng, Robert Spurr, Xiong Liu, Kelly Chance, Michael I. Mishchenko Jan 2014

A Numerical Testbed For Remote Sensing Of Aerosols, And Its Demonstration For Evaluating Retrieval Synergy From A Geostationary Satellite Constellation Of Geo-Cape And Goes-R, Jun Wang, Xiaoguang Xu, Shouguo Ding, Jing Zeng, Robert Spurr, Xiong Liu, Kelly Chance, Michael I. Mishchenko

Department of Earth and Atmospheric Sciences: Faculty Publications

We present a numerical testbed for remote sensing of aerosols, together with a demonstration for evaluating retrieval synergy from a geostationary satellite constellation. The testbed combines inverse (optimal-estimation) software with a forward model containing linearized code for computing particle scattering (for both spherical and non-spherical particles). a kernel-based (land and ocean) surface bi-directional reflectance facility, and a linearized radiative transfer model for polarized radiance. Calculation of gas absorption spectra uses the HITRAN (HIgh-resolution TRANsmission molecular absorption) database of spectroscopic line parameters and other trace species cross-sections. The outputs of the testbed include not only the Stokes 4-vector elements and their …

Go to article

Prolonged Instability Prior To A Regime Shift, Trisha L. Spanbauer, Craig R. Allen, David G. Angeler, Tarsha Eason, Sherilyn C. Fritz, Ahjond S. Garmestani, Kirsty L. Nash, Jeffrey R. Stone Jan 2014

Prolonged Instability Prior To A Regime Shift, Trisha L. Spanbauer, Craig R. Allen, David G. Angeler, Tarsha Eason, Sherilyn C. Fritz, Ahjond S. Garmestani, Kirsty L. Nash, Jeffrey R. Stone

Department of Earth and Atmospheric Sciences: Faculty Publications

Regime shifts are generally defined as the point of ‘abrupt’ change in the state of a system. However, a seemingly abrupt transition can be the product of a system reorganization that has been ongoing much longer than is evident in statistical analysis of a single component of the system. Using both univariate and multivariate statistical methods, we tested a longterm high-resolution paleoecological dataset with a known change in species assemblage for a regime shift. Analysis of this dataset with Fisher Information and multivariate time series modeling showed that there was a ~2000 year period of instability prior to the regime …

Go to article

The Emerging Field Of Geogenomics: Constraining Geological Problems With Genetic Data, Paul A. Baker, Sherilyn C. Fritz, Christopher W. Dick, Andrew J. Eckert, Brian K. Horton, Stefano Manzoni, Camila C. Ribas, Carmala N. Garzione, David S. Battisti Jan 2014

The Emerging Field Of Geogenomics: Constraining Geological Problems With Genetic Data, Paul A. Baker, Sherilyn C. Fritz, Christopher W. Dick, Andrew J. Eckert, Brian K. Horton, Stefano Manzoni, Camila C. Ribas, Carmala N. Garzione, David S. Battisti

Department of Earth and Atmospheric Sciences: Faculty Publications

The development of a genomics-derived discipline within geology is timely, as a result of major advances in acquiring and processing geologically relevant genetic data. This paper articulates the emerging field of “geogenomics,” which involves the use of large-scale genetic data to constrain geological hypotheses. The paper introduces geogenomics and discusses how hypotheses can be ad-dressed through collaboration between geologists and evolutionary biologists. As an example, geogenomic methods are applied to evaluate competing hypotheses regarding the timing of the Andean uplift, the closure of the Isthmus of Panama, the onset of trans-Amazon drainage, and Quaternary climate variation in the Neotropics.

Go to article

Daily Area Of Snow Melt Onset On Arctic Sea Ice From Passive Microwave Satellite Observations 1979–2012, Angela C. Bliss, Mark R. Anderson Jan 2014

Daily Area Of Snow Melt Onset On Arctic Sea Ice From Passive Microwave Satellite Observations 1979–2012, Angela C. Bliss, Mark R. Anderson

Department of Earth and Atmospheric Sciences: Faculty Publications

Variability in snow melt onset (MO) on Arctic sea ice since 1979 is examined by determining the area of sea ice experiencing the onset of melting during the melt season on a daily basis. The daily MO area of the snow and ice surface is determined from passive microwave satellite-derived MO dates for the Arctic Ocean and sub-regions. Annual accumulations of MO area are determined by summing the time series of daily MO area through the melt season. Daily areas and annual accumulations of MO area highlight inter-annual and regional variability in the timing of MO area, which is sensitive …

Go to article

Cenomanian Through Basal Coniacian Calcareous Nannofossil Biostratigraphy Of Themancos Shale Reference Section, Mesa Verde National Park, Co, Matthew J. Corbett, David K. Watkins Jan 2014

Cenomanian Through Basal Coniacian Calcareous Nannofossil Biostratigraphy Of Themancos Shale Reference Section, Mesa Verde National Park, Co, Matthew J. Corbett, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

Upper Cenomanian through lower Coniacian calcareous nannofossil biostratigraphy is integrated with macrofossil and lithostratigraphic correlations at the reference section for the Mancos Shale in Mesa Verde National Park, CO. Interpretations of key biostratigraphic events and δ13C values from bulk-rock carbonate fit well with the placement of stage boundaries by Leckie et al. (1997) and observations of nannofossil biostratigraphy in equivalent successions in the Western Interior. Tethyan nannofossil zone CC10b brackets the Cenomanian-Turonian boundary between 22.7–27.6m. Anannofossil zonal boundary between CC13 and CC14 is placed at 200.4-201m supporting the existence of an unconformity in the basal Smoky Hill Member …

Go to article

Ashfall Tephra In The Ogallala Group Of The Great Plains: Characteristics And Significance, Michael E. Perkins, Robert F. Diffendal Jr., Michael R. Voorhies, Barbara P. Nash, Bruce E. Bailey Jan 2014

Ashfall Tephra In The Ogallala Group Of The Great Plains: Characteristics And Significance, Michael E. Perkins, Robert F. Diffendal Jr., Michael R. Voorhies, Barbara P. Nash, Bruce E. Bailey

Robert F. Diffendal, Jr., Publications

The Miocene Ogallala Group blankets the Great Plains east of the Rocky Mountains. This sheet of largely fluvial deposits, lying downwind of major silicic volcanic fields to the west, was ideally located to receive and preserve tephra from these fields. This investigation brings modern methods of tephrochronlogy to bear on the age and identity of Ogallala tephra. Results indicate that ~40 separate tephra layers, ranging in age from ~16.5–5.0 Ma, in the Ogallala. Most tephra came from Yellowstone hotspot sources. The relative frequency of hotspot tephra in the Ogallala matches that in more proximal regions to the west with peak …

Go to article

Nongeocentric Axial Dipole Field Behavior During The Mono Lake Excursion, Robert M. Negrini, Daniel T. Mccuan, Robert A. Horton, James D. Lopez, William S. Cassata, James E. T. Channell, Kenneth L. Verosub, Jeffrey R. Knott, Robert S. Coe, Joseph C. Liddicoat, Steven P. Lund, Larry Benson, Andrei M. Sarna-Wojcicki Jan 2014

Nongeocentric Axial Dipole Field Behavior During The Mono Lake Excursion, Robert M. Negrini, Daniel T. Mccuan, Robert A. Horton, James D. Lopez, William S. Cassata, James E. T. Channell, Kenneth L. Verosub, Jeffrey R. Knott, Robert S. Coe, Joseph C. Liddicoat, Steven P. Lund, Larry Benson, Andrei M. Sarna-Wojcicki

United States Geological Survey: Staff Publications

A new record of the Mono Lake excursion (MLE) is reported from the Summer Lake Basin of Oregon, USA. Sediment magnetic properties indicate magnetite as the magnetization carrier and imply suitability of the sediments as accurate recorders of the magnetic field including relative paleointensity (RPI) variations. The magnitudes and phases of the declination, inclination, and RPI components of the new record correlate well with other coeval but lower resolution records from western North America including records from the Wilson Creek Formation exposed around Mono Lake. The virtual geomagnetic pole (VGP) path of the new record is similar to that from …

Go to article

Wetland Reserve Program Enhances Site Occupancy And Species Richness In Assemblages Of Anuran Amphibians In The Mississippi Alluvial Valley, Usa, Susan C. Walls, J. Hardin Waddle, Stephen P. Faulkner Jan 2014

Wetland Reserve Program Enhances Site Occupancy And Species Richness In Assemblages Of Anuran Amphibians In The Mississippi Alluvial Valley, Usa, Susan C. Walls, J. Hardin Waddle, Stephen P. Faulkner

United States Geological Survey: Staff Publications

We measured amphibian habitat use to quantify the effectiveness of conservation practices implemented under the Wetland Reserve Program (WRP), an initiative of the U.S. Department of Agriculture’s Natural Resources Conservation Service. From February to June 2007, we quantified calling male anurans in cultivated cropland, former cultivated cropland restored through the WRP, and mature bottomland hardwood forest. Sites were located in two watersheds within the Mississippi Alluvial Valley of Arkansas and Louisiana, USA. We estimated detection probability and site occupancy within each land use category using a Bayesian hierarchical model of community species occurrence, and derived an estimate of species richness …

Go to article

Mapping Irrigated Areas In Afghanistan Over The Past Decade Using Modis Ndvi, Md. Shahriar Pervez, Michael Budde, James Rowland Jan 2014

Mapping Irrigated Areas In Afghanistan Over The Past Decade Using Modis Ndvi, Md. Shahriar Pervez, Michael Budde, James Rowland

United States Geological Survey: Staff Publications

Agricultural production capacity contributes to food security in Afghanistan and is largely dependent on irrigated farming, mostly utilizing surface water fed by snowmelt. Because of the high contribution of irrigated crops (> 80%) to total agricultural production, knowing the spatial distribution and year-to-year variability in irrigated areas is imperative to monitoring food security for the country. We used 16-day composites of the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor to create 23-point time series for each year from 2000 through 2013. Seasonal peak values and time series were used in a threshold-dependent decision tree …

Go to article

Maintaining Resilience In The Face Of Climate Change, Alejandro E. Camacho, T. Douglas Beard Jan 2014

Maintaining Resilience In The Face Of Climate Change, Alejandro E. Camacho, T. Douglas Beard

United States Geological Survey: Staff Publications

Climate change, when combined with more conventional stress from human exploitation, calls into question the capacity of both existing ecological communities and resource management institutions to experience disturbances while substantially retaining their same functions and identities (Zellmer and Gunderson 2009; Ruhl 2011). In other words, the physical and biological effects of climate change raise fundamental challenges to the resilience of natural ecosystems (Gunderson and Holling 2002). Perhaps more importantly, the projected scope of ecological shifts from global climate change-and uncertainty about such changes-significantly stresses the capacity of legal institutions to manage ecosystem change (Camacho 2009). Existing governmental institutions lack the …

Go to article

Riverbank Filtration Potential Of Pharmaceuticals In A Wastewater-Impacted Stream, Paul M. Bradley, Larry B. Barber, Joesph W. Duris, William T. Foreman, Edward T. Furlong, Laura E. Hubbard, Kasey J. Hutchinson, Steffanie H. Keefe, Dana W. Kolpin Jan 2014

Riverbank Filtration Potential Of Pharmaceuticals In A Wastewater-Impacted Stream, Paul M. Bradley, Larry B. Barber, Joesph W. Duris, William T. Foreman, Edward T. Furlong, Laura E. Hubbard, Kasey J. Hutchinson, Steffanie H. Keefe, Dana W. Kolpin

United States Geological Survey: Staff Publications

Pharmaceutical contamination of shallow groundwater is a substantial concern in effluent-dominated streams, due to high aqueous mobility, designed bioactivity, and effluent-driven hydraulic gradients. In October and December 2012, effluent contributed approximately 99% and 71%, respectively, to downstream flow in Fourmile Creek, Iowa, USA. Strong hydrologic connectivity was observed between surface-water and shallow-groundwater. Carbamazepine, sulfamethoxazole, and immunologically related compounds were detected in groundwater at greater than 0.02 mg L^-1 at distances up to 6 m from the stream bank. Direct aqueous-injection HPLC-MS/MS revealed 43% and 55% of 110 total pharmaceutical analytes in surface-water samples in October and December, respectively, with 16% …

Go to article

Biogeochemical Aspects Of Uranium Mineralization, Mining, Milling, And Remediation, Kate M. Campbell, Tanya J. Gallegos, Edward R. Landa Jan 2014

Biogeochemical Aspects Of Uranium Mineralization, Mining, Milling, And Remediation, Kate M. Campbell, Tanya J. Gallegos, Edward R. Landa

United States Geological Survey: Staff Publications

Natural uranium (U) occurs as a mixture of three radioactive isotopes: 238U, 235U, and 234U. Only 235U is fissionable and makes up about 0.7% of natural U, while 238U is overwhelmingly the most abundant at greater than 99% of the total mass of U. Prior to the 1940s, U was predominantly used as a coloring agent, and U-bearing ores were mined mainly for their radium (Ra) and/or vanadium (V) content; the bulk of the U was discarded with the tailings (Finch et al., 1972). Once nuclear fission was discovered, the economic importance of U increased greatly. The mining and milling …

Go to article

Parameter Estimation For Groundwater Models Under Uncertain Irrigation Data, Yonas Demissie, Albert Valocchi, Ximing Cai, Nicholas Brozovic, Gabriel Senay, Mekonnen Gebremichael Jan 2014

Parameter Estimation For Groundwater Models Under Uncertain Irrigation Data, Yonas Demissie, Albert Valocchi, Ximing Cai, Nicholas Brozovic, Gabriel Senay, Mekonnen Gebremichael

United States Geological Survey: Staff Publications

The success of modeling groundwater is strongly influenced by the accuracy of the model parameters that are used to characterize the subsurface system. However, the presence of uncertainty and possibly bias in groundwater model source/sink terms may lead to biased estimates of model parameters and model predictions when the standard regression-based inverse modeling techniques are used. This study first quantifies the levels of bias in groundwater model parameters and predictions due to the presence of errors in irrigation data. Then, a new inverse modeling technique called input uncertainty weighted least-squares (IUWLS) is presented for unbiased estimation of the parameters when …

Go to article

Comparing Cropland Net Primary Production Estimates Frominventory, A Satellite-Based Model, And A Process-Based Model In Themidwest Of The United States, Zengpeng Li, Shuguang Liu, Zhengxi Tan, Normann B. Bliss, Claudia J. Young, Tristram O. West, Stephen M. Ogle Jan 2014

Comparing Cropland Net Primary Production Estimates Frominventory, A Satellite-Based Model, And A Process-Based Model In Themidwest Of The United States, Zengpeng Li, Shuguang Liu, Zhengxi Tan, Normann B. Bliss, Claudia J. Young, Tristram O. West, Stephen M. Ogle

United States Geological Survey: Staff Publications

Accurately quantifying the spatial and temporal variability of net primary production (NPP) for crop-lands is essential to understand regional cropland carbon dynamics. We compared three NPP estimates for croplands in the Midwestern United States: inventory-based estimates using crop yield data from the U.S. Department of Agriculture (USDA) National Agricultural Statistics Service (NASS); estimates from the satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) NPP product; and estimates from the General Ensemble biogeochemical Modeling System (GEMS) process-based model. The three methods estimated mean NPP in the range of 469–687 g C m−2yr−1and total NPP in the range of318–490 Tg C yr−1for croplands in …

Go to article

Humic Substances Interfere With Detection Of Pathogenic Prion Protein, Christen B. Smith, Clarissa J. Booth, Tyler J. Wadzinski, Giuseppe Legname, Rick Chappell, Christopher J. Johnson, Joel A. Pedersen Jan 2014

Humic Substances Interfere With Detection Of Pathogenic Prion Protein, Christen B. Smith, Clarissa J. Booth, Tyler J. Wadzinski, Giuseppe Legname, Rick Chappell, Christopher J. Johnson, Joel A. Pedersen

United States Geological Survey: Staff Publications

Studies examining the persistence of prions (the etiological agent of transmissible spongiform encephalopathies) in soil require accurate quantification of pathogenic prion protein (PrPTSE) extracted from or in the presence of soil particles. Here, we demonstrate that natural organic matter (NOM) in soil impacts PrPTSE detection by immunoblotting. Methods commonly used to extract PrPTSE from soils release substantial amounts of NOM, and NOM inhibited PrPTSE immunoblot signal. The degree of immunoblot interference increased with increasing NOM concentration and decreasing NOM polarity. Humic substances affected immunoblot detection of prion protein from both deer and hamsters. We also establish that after interaction with …

Go to article

Structural Equation Models Of Vmt Growth In Us Urbanised Areas, Reid Ewing, Shima Hamidi, Frank Gallivan, Arthur C. Nelson, James B. Grace Jan 2014

Structural Equation Models Of Vmt Growth In Us Urbanised Areas, Reid Ewing, Shima Hamidi, Frank Gallivan, Arthur C. Nelson, James B. Grace

United States Geological Survey: Staff Publications

Vehicle miles travelled (VMT) is a primary performance indicator for land use and transportation, bringing with it both positive and negative externalities. This study updates and refines previous work on VMT in urbanised areas, using recent data, additional metrics and structural equation modelling (SEM). In a cross-sectional model for 2010, population, income and freeway capacity are positively related to VMT, while gasoline prices, development density and transit service levels are negatively related. Findings of the cross-sectional model are generally confirmed in a more tightly controlled longitudinal study of changes in VMT between 2000 and 2010, the first model of its …

Go to article

Merging Remote Sensing Data And National Agricultural Statistics To Model Change In Irrigated Agriculture, Jesslyn F. Brown, Md Shahriar Pervez Jan 2014

Merging Remote Sensing Data And National Agricultural Statistics To Model Change In Irrigated Agriculture, Jesslyn F. Brown, Md Shahriar Pervez

United States Geological Survey: Staff Publications

Over 22 million hectares (ha) of U.S. croplands are irrigated. Irrigation is an intensified agricultural land use that increases crop yields and the practice affects water and energy cycles at, above, and below the land surface. Until recently, there has been a scarcity of geospatially detailed information about irrigation that is comprehensive, consistent, and timely to support studies tying agricultural land use change to aquifer water use and other factors. This study shows evidence for a recent overall net expansion of 522 thousand ha across the U.S. (2.33%) and 519 thousand ha (8.7%) in irrigated cropped area across the High …

Go to article

Comparing Crop Land Net Primary Production Estimates From Inventory, A Satellite-Based Model, And A Process-Based Model In The Midwest Of The United States Zhengpeng, Zhengpeng Li, Shuguang Liu, Zhengxi Tan, Normann B. Bliss, Claudia J. Young, Tristram O. West, Stephen M. Ogle Jan 2014

Comparing Crop Land Net Primary Production Estimates From Inventory, A Satellite-Based Model, And A Process-Based Model In The Midwest Of The United States Zhengpeng, Zhengpeng Li, Shuguang Liu, Zhengxi Tan, Normann B. Bliss, Claudia J. Young, Tristram O. West, Stephen M. Ogle

United States Geological Survey: Staff Publications

Accurately quantifying the spatial and temporal variability of net primary production (NPP) for crop-lands is essential to understand regional cropland carbon dynamics. We compared three NPP estimates for croplands in the Midwestern United States: inventory-based estimates using crop yield data from the U.S. Department of Agriculture (USDA) National Agricultural Statistics Service (NASS); estimates from the satellite-based Moderate Resolution Imaging Spectro radiometer (MODIS) NPP product; and esti-mates from the General Ensemble bio geochemical Modeling System (GEMS) process-based model. The three methods estimated mean NPP in the range of 469–687 g C m−2yr−1and total NPP in the range …

Go to article

Summary Of The Snowmastodon Project Special Volume: A High-Elevation, Multi-Proxy Biotic And Environmental Record Of Mis 6–4 From The Ziegler Reservoir Fossil Site, Snowmass Village, Colorado, Usa, Ian M. Miller, Jeffrey S. Pigati, R. Scott Anderson, Kirk R. Johnson, Shannon A. Mahan, Thomas A. Ager, Richard G. Baker, Maarten Blaauw, Jordon Bright, Peter M. Brown, Bruce Bryant, Zachary T. Calamari, Paul E. Carrara, Michael D. Cherney, John R. Demboski, Scott A. Elias, Daniel C. Fisher, Harrison J. Gray, Danielle R. Haskett, Jeffrey S. Honke, Stephen T. Jackson, Gonzalo Jiménez- Moreno, Douglas Kline, Eric M. Leonard, Nathaniel A. Lifton, Carol Lucking, H. Gregory Mcdonald, Dane M. Miller, Daniel R. Muhs, Stephen E. Nash, Cody Newton, James B. Paces, Lesley Petrie, Mitchell A. Plummer, David F. Porinchu, Adam N. Rountrey, Eric Scott, Joseph J.W. Sertich, Saxon E. Sharpe, Gary L. Skipp, Laura E. Strickland, Richard K. Stucky, Robert S. Thompson, Jim Wilson Jan 2014

Summary Of The Snowmastodon Project Special Volume: A High-Elevation, Multi-Proxy Biotic And Environmental Record Of Mis 6–4 From The Ziegler Reservoir Fossil Site, Snowmass Village, Colorado, Usa, Ian M. Miller, Jeffrey S. Pigati, R. Scott Anderson, Kirk R. Johnson, Shannon A. Mahan, Thomas A. Ager, Richard G. Baker, Maarten Blaauw, Jordon Bright, Peter M. Brown, Bruce Bryant, Zachary T. Calamari, Paul E. Carrara, Michael D. Cherney, John R. Demboski, Scott A. Elias, Daniel C. Fisher, Harrison J. Gray, Danielle R. Haskett, Jeffrey S. Honke, Stephen T. Jackson, Gonzalo Jiménez- Moreno, Douglas Kline, Eric M. Leonard, Nathaniel A. Lifton, Carol Lucking, H. Gregory Mcdonald, Dane M. Miller, Daniel R. Muhs, Stephen E. Nash, Cody Newton, James B. Paces, Lesley Petrie, Mitchell A. Plummer, David F. Porinchu, Adam N. Rountrey, Eric Scott, Joseph J.W. Sertich, Saxon E. Sharpe, Gary L. Skipp, Laura E. Strickland, Richard K. Stucky, Robert S. Thompson, Jim Wilson

United States Geological Survey: Staff Publications

In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean–atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010–2011, construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a nearly continuous, lacustrine/wetland sedimentary sequence that preserved evidence of past plant communities between ~140 and 55 ka, including all of MIS 5. At an elevation of 2705 m, the Ziegler Reservoir fossil site also contained thousands of well-preserved bones …

Go to article

Radiocarbon Dating Loess Deposits In The Mississippi Valley Using Terrestrial Gastropod Shells (Polygyridae, Helicinidae, And Discidae), Jeffrey S. Pigati, John Mcgeehin, Daniel R. Muhs, David A. Grimley, Jeffrey C. Nekola Jan 2014

Radiocarbon Dating Loess Deposits In The Mississippi Valley Using Terrestrial Gastropod Shells (Polygyridae, Helicinidae, And Discidae), Jeffrey S. Pigati, John Mcgeehin, Daniel R. Muhs, David A. Grimley, Jeffrey C. Nekola

United States Geological Survey: Staff Publications

Small terrestrial gastropod shells (mainly Succineidae) have been used successfully to date late Quaternary loess deposits in Alaska and the Great Plains. However, Succineidae shells are less common in loess deposits in the Mississippi Valley compared to those of the Polygyridae, Helicinidae, and Discidae families. In this study, we conducted several tests to determine whether shells of these gastropods could provide reliable ages for loess deposits in the Mississippi Valley. Our results show that most of the taxa that we investigated incorporate small amounts (1–5%) of old carbon from limestone in their shells, meaning that they should yield ages that …

Go to article

Geologic Setting And Stratigraphy Of The Ziegler Reservoir Fossil Site, Snowmass Village, Colorado, Jeffrey S. Pigati, Ian M. Miller, Kirk R. Johnson, Jeffrey S. Honke, Paul E. Carrara, Daniel R. Muhs, Gary Skipp, Bruce Bryant Jan 2014

Geologic Setting And Stratigraphy Of The Ziegler Reservoir Fossil Site, Snowmass Village, Colorado, Jeffrey S. Pigati, Ian M. Miller, Kirk R. Johnson, Jeffrey S. Honke, Paul E. Carrara, Daniel R. Muhs, Gary Skipp, Bruce Bryant

United States Geological Survey: Staff Publications

The geologic setting of the Ziegler Reservoir fossil site is somewhat unusual—the sediments containing the Pleistocene fossils were deposited in a lake on top of a ridge. The lake basin was formed near Snowmass Village, Colorado (USA) when a glacier flowing down Snowmass Creek Valley became thick enough to overtop a low point in the eastern valley wall and entered the head of Brush Creek Valley. When the glacier retreated at about 155–130 ka, near the end of Marine Oxygen Isotope Stage 6, the Brush Creek Valley lobe left behind a moraine that impounded a small alpine lake. The lake …

Go to article

Toxicity Of Pb‐Contaminated Soil To Japanese Quail (Coturnix Japonica) And The Use Of The Blood–Dietary Pb Slope In Risk Assessment, W. Nelson Beyer, Yu Chen, Paula Henry, Thomas May, David Mosby, Barnett A. Rattner, Valerie I. Shearn-Bochsler, Daniel Sprague, John Weber Jan 2014

Toxicity Of Pb‐Contaminated Soil To Japanese Quail (Coturnix Japonica) And The Use Of The Blood–Dietary Pb Slope In Risk Assessment, W. Nelson Beyer, Yu Chen, Paula Henry, Thomas May, David Mosby, Barnett A. Rattner, Valerie I. Shearn-Bochsler, Daniel Sprague, John Weber

United States Geological Survey: Staff Publications

This study relates tissue concentrations and toxic effects of Pb in Japanese quail (Coturnix japonica) to the dietary exposure of soil‐borne Pb associated with mining and smelting. From 0% to 12% contaminated soil, by weight, was added to 5 experimental diets (0.12 to 382mg Pb/kg, dry wt) and fed to the quail for 6 weeks. Benchmark doses associated with a 50% reduction in delta‐aminolevulinic acid dehydratase activity were 0.62mg Pb/kg in the blood, dry wt, and 27mg Pb/kg in the diet. Benchmark doses associated with a 20% increase in the concentration of erythrocyte protoporphyrin were 2.7mg Pb/kg in …

Go to article

Testing Metapopulation Concepts: Effects Of Patch Characteristics And Neighborhood Occupancy On The Dynamics Of An Endangered Lagomorph, Mitchell J. Eaton, Phillip T. Hughes, James E. Hines, James D. Nichols Jan 2014

Testing Metapopulation Concepts: Effects Of Patch Characteristics And Neighborhood Occupancy On The Dynamics Of An Endangered Lagomorph, Mitchell J. Eaton, Phillip T. Hughes, James E. Hines, James D. Nichols

United States Geological Survey: Staff Publications

Metapopulation ecology is a field that is richer in theory than in empirical results. Many existing empirical studies use an incidence function approach based on spatial patterns and key assumptions about extinction and colonization rates. Here we recast these assumptions as hypotheses to be tested using 18 years of historic detection survey data combined with four years of data from a new monitoring program for the Lower Keys marsh rabbit. We developed a new model to estimate probabilities of local extinction and colonization in the presence of nondetection, while accounting for estimated occupancy levels of neighboring patches. We used model …

Go to article

Probit Models For Capture-Recapture Data Subject To Imperfect Detection, Individual Heterogeneity And Misidentification, Brett T. Mcclinktock, Larissa L. Bailey, Brian P. Dreher, William A. Link Jan 2014

Probit Models For Capture-Recapture Data Subject To Imperfect Detection, Individual Heterogeneity And Misidentification, Brett T. Mcclinktock, Larissa L. Bailey, Brian P. Dreher, William A. Link

United States Geological Survey: Staff Publications

As noninvasive sampling techniques for animal populations have become more popular, there has been increasing interest in the development of capture-recapture models that can accommodate both imperfect detection and misidentification of individuals (e.g., due to genotyping error). However, current methods do not allow for individual variation in parameters, such as detection or survival probability. Here we develop misidentification models for capture-recapture data that can simultaneously account for temporal variation, behavioral effects and individual heterogeneity in parameters. To facilitate Bayesian inference using our approach, we extend standard probit regression techniques to latent multinomial models where the dimension and zeros of the …

Go to article

Testing Metapopulation Concepts: Effects Of Patch Characteristics And Neighborhood Occupancy On The Dynamics Of An Endangered Lagomorph, Mitchell J. Eaton, Phillip T. Hughes, James E. Hines, James D. Nichols Jan 2014

Testing Metapopulation Concepts: Effects Of Patch Characteristics And Neighborhood Occupancy On The Dynamics Of An Endangered Lagomorph, Mitchell J. Eaton, Phillip T. Hughes, James E. Hines, James D. Nichols

United States Geological Survey: Staff Publications

Metapopulation ecology is a field that is richer in theory than in empirical results. Many existing empirical studies use an incidence function approach based on spatial patterns and key assumptions about extinction and colonization rates. Here we recast these assumptions as hypotheses to be tested using 18 years of historic detection survey data combined with four years of data from a new monitoring program for the Lower Keys marsh rabbit. We developed a new model to estimate probabilities of local extinction and colonization in the presence of nondetection, while accounting for estimated occupancy levels of neighboring patches. We used model …

Go to article

Probit Models For Capture-Recapture Data Subject To Imperfect Detection, Individual Heterogeneity And Misidentification1, Brett T. Mcclintock, Larissa L. Bailey, Brian P. Dreher, William A. Link Jan 2014

Probit Models For Capture-Recapture Data Subject To Imperfect Detection, Individual Heterogeneity And Misidentification1, Brett T. Mcclintock, Larissa L. Bailey, Brian P. Dreher, William A. Link

United States Geological Survey: Staff Publications

As noninvasive sampling techniques for animal populations have become more popular, there has been increasing interest in the development of capture-recapture models that can accommodate both imperfect detection and misidentification of individuals (e.g., due to genotyping error). However, current methods do not allow for individual variation in parameters, such as detection or survival probability. Here we develop misidentification models for capture-recapture data that can simultaneously account for temporal variation, behavioral effects and individual heterogeneity in parameters. To facilitate Bayesian inference using our approach, we extended standard probit regression techniques to latent multinomial models where the dimension and zeros of the …

Go to article

Loess Records, Daniel R. Muhs, Stephen R. Cattle, Onn Crouvi, Denis-Didier Rousseau, Jimin Sun, Marcelo A. Zárate Jan 2014

Loess Records, Daniel R. Muhs, Stephen R. Cattle, Onn Crouvi, Denis-Didier Rousseau, Jimin Sun, Marcelo A. Zárate

United States Geological Survey: Staff Publications

Loess is aeolian sediment, dominated by silt-sized particles, that is identifiable in the field as a distinct sedimentary body. It covers a significant portion of the land surface of the Earth and as such constitutes one of the most important archives of long-term dust deposition. Large tracts of loess cover Europe, Asia, South America, and North America, and smaller loess bodies are found covering parts of Africa, the Middle East, New Zealand, and Australia. Loess thickness, particle size, and carbonate content decrease downwind from sources, trends that are powerful tools for reconstructing paleowinds. Many loess sections consist of relatively thick …

Go to article

Evidence Of Repeated Wildfires Prior To Human Occupation On San Nicolas Island, California, Jeffrey S. Pigati, John P. Mcgeehin, Gary L. Skipp, Daniel R. Muhs Jan 2014

Evidence Of Repeated Wildfires Prior To Human Occupation On San Nicolas Island, California, Jeffrey S. Pigati, John P. Mcgeehin, Gary L. Skipp, Daniel R. Muhs

United States Geological Survey: Staff Publications

Understanding how early humans on the California Channel Islands might have changed local fire regimes requires a baseline knowledge of the frequency of natural wildfires on the islands prior to human occupation. A sedimentary sequence that was recently discovered in a small canyon on San Nicolas Island contains evidence of at least 24 burn events that date to between ~37 and 25 ka (thousands of calibrated 14C years before present), well before humans entered North America. The evidence includes abundant macroscopic charcoal, blackened sediments, and discrete packages of oxidized, reddish-brown sediments that are similar in appearance to sedimentary features …

Go to article

First Prev Next Last