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United States Geological Survey: Staff Publications

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Articles 691 - 720 of 1026

Full-Text Articles in Earth Sciences

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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Weathering Of Sulfidic Shale And Copper Mine Waste: Secondary Minerals And Metal Cycling In Great Smoky Mountains National Park, Tennessee, And North Carolina, Usa, Jane M. Hammarstrom, Robert R. Seal Ii, Allen L. Meier, John C. Jackson Jan 2003

Weathering Of Sulfidic Shale And Copper Mine Waste: Secondary Minerals And Metal Cycling In Great Smoky Mountains National Park, Tennessee, And North Carolina, Usa, Jane M. Hammarstrom, Robert R. Seal Ii, Allen L. Meier, John C. Jackson

United States Geological Survey: Staff Publications

Metal cycling via physical and chemical weathering of discrete sources (copper mines) and regional (non-point) sources (sulfide-rich shale) is evaluated by examining the mineralogy and chemistry of weathering products in Great Smoky Mountains National Park, Tennessee, and North Carolina, USA. The elements in copper mine waste, secondary minerals, stream sediments, and waters that are most likely to have negative impacts on aquatic ecosystems are aluminum, copper, zinc, and arsenic because these elements locally exceed toxicity guidelines for surface waters or for stream sediments. Acid-mine drainage has not developed in streams draining inactive copper mines. Acid-rock drainage and chemical weathering processes …

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Groundwater Flow Andwater Quality – A Flowpath Study In The Seminolewell Field, Cedar Rapids, Iowa, Douglas J. Schnoebelen, Michael J. Turco, John D. North Jan 2003

Groundwater Flow Andwater Quality – A Flowpath Study In The Seminolewell Field, Cedar Rapids, Iowa, Douglas J. Schnoebelen, Michael J. Turco, John D. North

United States Geological Survey: Staff Publications

In Iowa, alluvial aquifers near major rivers are a source of water for many communities. The City of Cedar Rapids withdraws water from wells completed in the Cedar River alluvium, a shallow alluvial aquifer adjacent to the Cedar River. The City of Cedar Rapids is located within Linn County in east-central Iowa, and water for the City is supplied by four well fields (East, Northwest, Seminole, and West well fields) along the Cedar River. The City has a population of about 121,000, and several large industries are major water users. Currently, per capita water usage in the City is nearly …

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Nebraska Birds In Recorded History, Fritz L. Knopf Jan 2003

Nebraska Birds In Recorded History, Fritz L. Knopf

United States Geological Survey: Staff Publications

The critical image of historical perspective is lacking in much of conservation biology's dialogue on protecting biotic diversity. Some biologists offer that the vision for bird conservation on the Central Grasslands of North America is to secure at least fragments of the avian assemblage that coexisted with Native Americans when Europeans first arrived. Nowhere, however, has anyone really tried to re-create such a historical image in any biological arena, until now.

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Eolian Sand Transport Pathways In The Southwestern United States: Importance Of The Colorado River And Local Sources, Daniel R. Muhs, Richard L. Reynolds, Josh Been, Gary Skipp Jan 2003

Eolian Sand Transport Pathways In The Southwestern United States: Importance Of The Colorado River And Local Sources, Daniel R. Muhs, Richard L. Reynolds, Josh Been, Gary Skipp

United States Geological Survey: Staff Publications

Geomorphologists have long recognized that eolian sand transport pathways extend over long distances in desert regions. Along such pathways, sediment transport by wind can surmount topographic obstacles and cross major drainages. Recent studies have suggested that three distinct eolian sand transport pathways exist (or once existed) in the Mojave and Sonoran Desert regions of the southwestern United States. One hypothesized pathway is eolian sand transport from the eastern Mojave Desert of California into western Arizona, near Parker, and would require sand movement across what must have been at least a seasonally dry Colorado River valley. We tested this hypothesis by …

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Quaternary Sedimentation And Subsidence History Of Lake Baikal, Siberia, Based On Seismic Stratigraphy And Coring, S. M. Colman, E. B. Karabanov, C. H. Nelson Iii Jan 2003

Quaternary Sedimentation And Subsidence History Of Lake Baikal, Siberia, Based On Seismic Stratigraphy And Coring, S. M. Colman, E. B. Karabanov, C. H. Nelson Iii

United States Geological Survey: Staff Publications

The long, continuous, high-latitude, stratigraphic record of Lake Baikal was deposited in three broad sedimentary environments, defined by high-resolution seismic-reflection and coring methods: (1) turbidite depositional systems, by far the most widespread, characterizing most of the margins and floors of the main basins of the lake, (2) large deltas of major drainages, and (3) tectonically or topographically isolated ridges and banks. Holocene sedimentation rates based on radiocarbon ages vary by more than an order of magnitude among these environments, from less than about 0.03 mm/yr on ridges and banks to more than about 0.3 mm/yr on basin floors. Extrapolating these …

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Birth Of The Modern Chesapeake Bay Estuary Between 7.4 And 8.2 Ka And Implications For Global Sea-Level Rise, John F. Bratton, Steven M. Colman, E. Robert Thieler, Robert R. Seal Ii Jan 2003

Birth Of The Modern Chesapeake Bay Estuary Between 7.4 And 8.2 Ka And Implications For Global Sea-Level Rise, John F. Bratton, Steven M. Colman, E. Robert Thieler, Robert R. Seal Ii

United States Geological Survey: Staff Publications

Two major pulses of sea-level rise are thought to have taken place since the last glacial maximum – meltwater pulses (mwp) 1A (12 cal ka) and 1B (9.5 cal ka). Between mwp 1B and about 6 cal ka, many of the complex coastal ecosystems which ring the world’s oceans began to form. Here we report data for rhenium, carbon isotopes, total organic carbon, and fossil oysters from Chesapeake Bay which span the transition from fresh to brackish water conditions in the bay in the mid- Holocene. These data constrain sea-level change and resulting environmental change in the bay. They indicate …

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Acquisition And Evaluation Of Thermodynamic Data For Morenosite-Retgersite Equilibria At 0.1 Mpa, I-Ming Chou, Robert R. Seal Ii Jan 2003

Acquisition And Evaluation Of Thermodynamic Data For Morenosite-Retgersite Equilibria At 0.1 Mpa, I-Ming Chou, Robert R. Seal Ii

United States Geological Survey: Staff Publications

Metal-sulfate salts in mine drainage environments commonly occur as solid solutions containing Fe, Cu, Mg, Zn, Al, Mn, Ni, Co, Cd, and other elements. Thermodynamic data for some of the endmember salts containing Fe, Cu, Zn, and Mg have been collected and evaluated previously, and the present study extends to the system containing Ni. Morenosite (NiSO4•7H2O)-retgersite (NiSO4•6H2O) equilibria were determined along five humidity buffer curves at 0.1 MPa and between 5 and 22 °C. Reversals along these humidity-buffer curves yield ln K = 17.58–6303.35/T, where K is the equilibrium constant, …

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Effects Of Crustal Stresses On Fluid Transport In Fractured Rock: Case Studies From Northeastern And Southwestern Usa, Roger H. Morin, William Z. Savage Jan 2003

Effects Of Crustal Stresses On Fluid Transport In Fractured Rock: Case Studies From Northeastern And Southwestern Usa, Roger H. Morin, William Z. Savage

United States Geological Survey: Staff Publications

The link between stress and hydrologic properties was examined at two sites that are distinguished by different rock types and different stress states. This investigation is based upon the analysis and interpretation of geophysical logs obtained in water wells at the two locations. At the northeast site (Newark Basin), the hydrologic characteristics of sedimentary rocks are dependent upon the relationship to the current regional stress field of two primary types of orthogonal features that serve as preferential pathways for fluid flow. Subhorizontal bedding-plane partings are highly transmissive near the surface and delineate transversely isotropic fluid flow at shallow depths. With …

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Influence Of The Pacific Decadal Oscillation On The Climate Of The Sierra Nevada, California And Nevada, Larry Benson, Braddock Linsley, Joe Smoot, Scott Mensing, Steve Lund, Scott Stine, Andre Sarna-Wojcicki Jan 2003

Influence Of The Pacific Decadal Oscillation On The Climate Of The Sierra Nevada, California And Nevada, Larry Benson, Braddock Linsley, Joe Smoot, Scott Mensing, Steve Lund, Scott Stine, Andre Sarna-Wojcicki

United States Geological Survey: Staff Publications

Mono Lake sediments have recorded five major oscillations in the hydrologic balance between A.D. 1700 and 1941. These oscillations can be correlated with tree-ring-based oscillations in Sierra Nevada snowpack. Comparison of a tree-ring-based reconstruction of the Pacific Decadal Oscillation (PDO) index (D’Arrigo et al., 2001) with a coral-based reconstruction of Subtropical South Pacific sea-surface temperature (Linsley et al., 2000) indicates a high degree of correlation between the two records during the past 300 yr. This suggests that the PDO has been a pan-Pacific phenomena for at least the past few hundred years. Major oscillations in the hydrologic balance of the …

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Age Of The Mono Lake Excursion And Associated Tephra, Larry Benson, Joseph Liddicoat, Joseph Smoot, Andrei Sarna-Wojcicki, Robert M. Negrini, Steve Lund Jan 2003

Age Of The Mono Lake Excursion And Associated Tephra, Larry Benson, Joseph Liddicoat, Joseph Smoot, Andrei Sarna-Wojcicki, Robert M. Negrini, Steve Lund

United States Geological Survey: Staff Publications

The Mono Lake excursion (MLE) is an important time marker that has been found in lake and marine sediments across much of the Northern Hemisphere. Dating of this event at its type locality, the Mono Basin of California, has yielded controversial results with the most recent effort concluding that the MLE may actually be the Laschamp excursion (Earth Planet. Sci. Lett. 197 (2002) 151). We show that a volcanic tephra (Ash #15) that occurs near the midpoint of the MLE has a date (not corrected for reservoir effect) of 28,620 ± 300 14C yr BP (~32,400 GISP2 yr BP) …

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Aeolian Cliff-Top Deposits And Buried Soils In The White River Badlands, South Dakota, Usa, J. Elmo Rawling Iii, Glen G. Fredlund, Shannon Mahan Jan 2003

Aeolian Cliff-Top Deposits And Buried Soils In The White River Badlands, South Dakota, Usa, J. Elmo Rawling Iii, Glen G. Fredlund, Shannon Mahan

United States Geological Survey: Staff Publications

Aeolian deposits in the North American Great Plains are important sources of Holocene palaeoenvironmental records. Although there are extensive studies on loess and dune records in the region, little is known about records in aeolian cliff-top deposits. These are common on table (mesa) edges in the White River Badlands. These sediments typically have loam and sandy-loam textures with dominantly very fine sand, 0.5–1% organic carbon and 0.5–5% CaCO3. Some of these aeolian deposits are atypically coarse and contain granules and fine pebbles. Buried soils within these deposits are weakly developed with A-C and A-AC-C profiles. Beneath these are …

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Quaternary Loess-Paleosol Sequences As Examples Of Climate-Driven Sedimentary Extremes, Daniel R. Muhs, E. Arthur Bettis Iii Jan 2003

Quaternary Loess-Paleosol Sequences As Examples Of Climate-Driven Sedimentary Extremes, Daniel R. Muhs, E. Arthur Bettis Iii

United States Geological Survey: Staff Publications

Loess is a widespread, wind-transported, silt-dominated deposit that contains geologic archives of atmospheric circulation and paleoclimate on continents. Loess may cover as much as 10% of the Earth’s land surface. It is composed mainly of quartz, feldspars, and clay minerals, with varying amounts of carbonate minerals. The geochemistry of loess differs from region to region, depending on source materials, but all loess is very high in SiO2 with lesser amounts of other major elements. Trends in loess downwind from source areas include systematic decreases in thickness and amounts of sand and coarse silt, and increases in amounts of fine silt …

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Mississippi River Blufflands And Bird Conservation, Eileen M. Kirsch Jan 2003

Mississippi River Blufflands And Bird Conservation, Eileen M. Kirsch

United States Geological Survey: Staff Publications

The "rubber hits the road" in conservation when the landowning public involved. Researchers and amateur birders know that populations of many species of neotropical migrant birds are declining because of habitat loss and many natural- and human-caused dangers. However, the landowners may not know what neotropical migrants are or that they are in peril. This excellent booklet and enclosed pamphlet are intended to educate landowners along the Mississippi River blufflands in Iowa, Illinois, Wisconsin, and Minnesota about neotropical migrant birds and their plight. Furthermore, it tactfully attempts to inspire concern about neotropical migrants and explains how management can help. While …

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Seasonal Distribution Of Migratory Tree Bats (Lasiurus And Lasionycteris) In North America, Paul M. Cryan Jan 2003

Seasonal Distribution Of Migratory Tree Bats (Lasiurus And Lasionycteris) In North America, Paul M. Cryan

United States Geological Survey: Staff Publications

Despite evidence of migration in North American tree bats (genera Lasiurus and Lasionycteris), details regarding seasonal movements in these widely distributed species are few. This study attempted to clarify patterns of seasonal distribution by mapping museum occurrence records by month. Monthly changes in the distribution of records indicate seasonal movements of tree bats. Northward migration during spring by Lasiurus cinereus appears to stem from wintering grounds in California and Mexico. During summer, male L. cinereus is mainly distributed in western North America, whereas females dominate samples from eastern regions. Lasiurus borealis winters in southeastern areas and expands its range …

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Eutrophication And Carbon Sources In Chesapeake Bay Over The Last 2700 Yr: Human Impacts In Context, John F. Bratton, Steven M. Colman, Robert R. Seal, Ii Jan 2003

Eutrophication And Carbon Sources In Chesapeake Bay Over The Last 2700 Yr: Human Impacts In Context, John F. Bratton, Steven M. Colman, Robert R. Seal, Ii

United States Geological Survey: Staff Publications

To compare natural variability and trends in a developed estuary with human-influenced patterns, stable isotope ratios (δ13C and δ15N) were measured in sediments from five piston cores collected in Chesapeake Bay. Mixing of terrestrial and algal carbon sources primarily controls patterns of δ13Corg profiles, so this proxy shows changes in estuary productivity and in delivery of terrestrial carbon to the bay. Analyses of δ15N show periods when oxygen depletion allowed intense denitrification and nutrient recycling to develop in the seasonally stratified water column, in addition to recycling taking place in surficial …

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New Record Of The Rare Emballonurid Bat Centronycteris Centralis Thomas, 1912 In Costa Rica, With Notes On Feeding Habits, Neal Woodman Jan 2003

New Record Of The Rare Emballonurid Bat Centronycteris Centralis Thomas, 1912 In Costa Rica, With Notes On Feeding Habits, Neal Woodman

United States Geological Survey: Staff Publications

The shaggy sac-winged bat, Centronycteris centralis (Chiroptera: Emballonuridae), occurs mainly in lowland forests from Veracruz, Mexico, to Peru, although it has been reported from elevations as high at 1450 m in Panama (Simmons and Handley 1998; Hice and Solari 2002). Most captures of the species are of single individuals, and throughout its distribution, this bat is rare and poorly-known (Emmons 1997; Reid 1997; Simmons and Handley 1998). Centronycteris centralis generally has been assumed to be an aerial insectivore, capturing flying insects on the wing (Starrett and Casebeer 1968; Wilson 1973; Timm et al. 1989; LaVal and Rodrı´guez 2002). However, direct …

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An Approach For Mapping Large-Area Impervious Surfaces: Synergistic Use Of Landsat-7 Etm+ And High Spatial Resolution Imagery, Limin Yang, Chengquan Huang, Bruce K. Wylie, Michael J. Coan Jan 2003

An Approach For Mapping Large-Area Impervious Surfaces: Synergistic Use Of Landsat-7 Etm+ And High Spatial Resolution Imagery, Limin Yang, Chengquan Huang, Bruce K. Wylie, Michael J. Coan

United States Geological Survey: Staff Publications

A wide range of urban ecosystem studies, including urban climate, land use planning, and resource management, require current and accurate geospatial data of urban impervious surfaces. We developed an approach to quantify urban impervious surfaces as a continuous variable by using multisensor datasets. Subpixel percent impervious surfaces at 30-m resolution were mapped using a regression tree model. The utility, practicality, and affordability of the proposed method for large-area imperviousness mapping were tested over three spatial scales (Sioux Falls, South Dakota, Richmond, Virginia, and the Chesapeake Bay areas of the United States). Average error of predicted versus actual percent impervious surface …

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Calibration Of Remotely Sensed, Coarse Resolution Ndvi To Co2 Fluxes In A Sagebrush–Steppe Ecosystem, Bruce K. Wylie, Douglas A. Johnson, Emilio Laca, Nicanor Z. Saliendra, Tagir G. Gilmanov, Bradley C. Reed, Larry L. Tieszen, Bruce B. Worstell Jan 2003

Calibration Of Remotely Sensed, Coarse Resolution Ndvi To Co2 Fluxes In A Sagebrush–Steppe Ecosystem, Bruce K. Wylie, Douglas A. Johnson, Emilio Laca, Nicanor Z. Saliendra, Tagir G. Gilmanov, Bradley C. Reed, Larry L. Tieszen, Bruce B. Worstell

United States Geological Survey: Staff Publications

The net ecosystem exchange (NEE) of carbon flux can be partitioned into gross primary productivity (GPP) and respiration (R). The contribution of remote sensing and modeling holds the potential to predict these components and map them spatially and temporally. This has obvious utility to quantify carbon sink and source relationships and to identify improved land management strategies for optimizing carbon sequestration. The objective of our study was to evaluate prediction of 14-day average daytime CO2 fluxes ( Fday) and nighttime CO2 fluxes (Rn) using remote sensing and other data. Fday …

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Rare-Earth Elements And Nd And Pb Isotopes As Source Indicators For Labrador Sea Clay-Size Sediments During Heinrich Event 2, Larry V. Benson, Don Barber, John T. Andrews, Howard E. Taylor, Paul Lamothe Jan 2003

Rare-Earth Elements And Nd And Pb Isotopes As Source Indicators For Labrador Sea Clay-Size Sediments During Heinrich Event 2, Larry V. Benson, Don Barber, John T. Andrews, Howard E. Taylor, Paul Lamothe

United States Geological Survey: Staff Publications

Elemental abundances and Nd and Pb isotope ratios were determined on samples from the carbonate-free, clay-size fractions of sediments from intervals above, within, and below Heinrich event 2 (H-2) in core HU87-9 from the Northwest Labrador Sea slope. In HU87-9, rare-earth element (REE) distributions and elemental concentrations within the H-2 event are distinct from those outside this event. ɛNd(0) and 206Pb/204Pb data also indicate different values for sediments deposited within and outside the H-2 event. Comparisons of REE patterns from the H-2 interval with those from bedrock units in Baffin Island, northern Quebec, and Labrador …

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Response Of North American Great Basin Lakes To Dansgaard–Oeschger Oscillations, Larry Benson, Steve Lund, Robert M. Negrini, Braddock Linsley, Mladen Zic Jan 2003

Response Of North American Great Basin Lakes To Dansgaard–Oeschger Oscillations, Larry Benson, Steve Lund, Robert M. Negrini, Braddock Linsley, Mladen Zic

United States Geological Survey: Staff Publications

We correlate oscillations in the hydrologic and/or cryologic balances of four Great Basin surface-water systems with Dansgaard– Oeschger (D–O) events 2–12. This correlation is relatively strong at the location of the magnetic signature used to link the lake records, but becomes less well constrained with distance/time from the signature. Comparison of proxy glacial and hydrologic records from Owens and Pyramid lakes indicates that Sierran glacial advances occurred during times of relative dryness. If our hypothesized correlation between the lake-based records and the GISP2 δ18O record is correct, it suggests that North Atlantic D–O stades …

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Late-Holocene Climate And Ecosystem History From Chesapeake Bay Sediment Cores, Usa, Debra A. Willard, Thomas M. Cronin, Stacey Verardo Jan 2003

Late-Holocene Climate And Ecosystem History From Chesapeake Bay Sediment Cores, Usa, Debra A. Willard, Thomas M. Cronin, Stacey Verardo

United States Geological Survey: Staff Publications

Palaeoclimate records from late-Holocene sediments in Chesapeake Bay, the largest estuary in the USA, provide evidence that both decadal to centennial climate variability and European colonization had severe impacts on the watershed and estuary. Using pollen and dinoflagellate cysts as proxies for mid-Atlantic regional precipitation, estuarine salinity and dissolved oxygen (DO) during the last 2300 years, we identified four dry intervals, centred on ad 50 (P1/D1), ad 1000 (P2/D2), ad 1400 (P3) and ad 1600 (P4). Two centennial-scale events, P1/D1 and P2/D2, altered forest composition and led to increased salinity and DO levels in the estuary. Intervals P3 and P4 …

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Apparent Break In Earthquake Scaling Due To Path And Site Effects On Deep Borehole Recordings, Satoshi Ide, Gregory C. Beroza, Stephanie G. Prejean, William L. Ellsworth Jan 2003

Apparent Break In Earthquake Scaling Due To Path And Site Effects On Deep Borehole Recordings, Satoshi Ide, Gregory C. Beroza, Stephanie G. Prejean, William L. Ellsworth

United States Geological Survey: Staff Publications

We reexamine the scaling of stress drop and apparent stress, rigidity times the ratio between seismically radiated energy to seismic moment, with earthquake size for a set of microearthquakes recorded in a deep borehole in Long Valley, California. In the first set of calculations, we assume a constant Q and solve for the corner frequency and seismic moment. In the second set of calculations, we model the spectral ratio of nearby events to determine the same quantities. We find that the spectral ratio technique, which can account for path and site effects or nonconstant Q, yields higher stress drops, …

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Topographically Driven Groundwater Flow And The San Andreas Heat Flow Paradox Revisited, Demian M. Saffer, Barbara A. Bekins, Stephen Hickman Jan 2003

Topographically Driven Groundwater Flow And The San Andreas Heat Flow Paradox Revisited, Demian M. Saffer, Barbara A. Bekins, Stephen Hickman

United States Geological Survey: Staff Publications

Evidence for a weak San Andreas Fault includes borehole heat flow measurements that show no evidence for a frictionally generated heat flow anomaly and the inferred orientation of σ1 nearly perpendicular to the fault trace. Interpretations of the stress orientation data remain controversial, at least in close proximity to the fault, leading some researchers to hypothesize that the San Andreas Fault is, in fact, strong and that its thermal signature may be removed or redistributed by topographically driven groundwater flow in areas of rugged topography, such as typify the San Andreas Fault system. To evaluate this scenario, we use …

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