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Articles 3331 - 3360 of 4541

Full-Text Articles in Earth Sciences

Oldest Cretaceous Sequence, Giralia Anticline, Carnarvon Basin, Western Australia: Late Hauterivian-Barremian, S. Mcloughlin, D. W. Haig, J. Backhouse, Mary Anne Holmes, G. Ellis, J. A. Long, K. J. Mcnamara Jan 1995

Oldest Cretaceous Sequence, Giralia Anticline, Carnarvon Basin, Western Australia: Late Hauterivian-Barremian, S. Mcloughlin, D. W. Haig, J. Backhouse, Mary Anne Holmes, G. Ellis, J. A. Long, K. J. Mcnamara

Department of Earth and Atmospheric Sciences: Faculty Publications

Outcrop of the oldest Cretaceous sequence in the Giralia Anticline and the Giralia No. 1 well, penetrating the same sequence, are described and biostratigraphically assessed in detail. The Cretaceous rocks lie on an erosion surface cut into Permian strata. A 10 m thick basal sand unit, the Birdrong Sandstone, is overlain by 56 m of carbonaceous siltstone-mudstone (Muderong Shale). The Birdrong Sandstone in the anticline belongs to the Muderongia australis Zone of late Hauterivian-Barremian age, as does the lower part of the Muderong Shale. The age of the upper Muderong Shale is uncertain, as is the age of a 10 …

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Foreshock Sequence Of The 1992 Landers, California, Earthquake And Its Implications For Earthquake Nucleation, Douglas A. Dodge, Gregory C. Beroza, W. L. Ellsworth Jan 1995

Foreshock Sequence Of The 1992 Landers, California, Earthquake And Its Implications For Earthquake Nucleation, Douglas A. Dodge, Gregory C. Beroza, W. L. Ellsworth

United States Geological Survey: Staff Publications

The June 28, 1992, Landers, California, earthquake(Mw=7.3) was preceded for about 7 hours by a foreshock sequence consisting of at least 28 events. In this study we examine the geometry and temporal development of the foreshocks using high-precision locations based on cross correlation of waveforms recorded at nearby stations. By aligning waveforms, rather than trying to obtain travel time picks for each event independently, we are able to improve the timing accuracy greatly and to make very accurate travel time picks even for emergent arrivals. We perform a joint relocation using the improved travel times and reduce the …

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Geomorphic And Geochemical Evidence For The Source Of Sand In The Algodones Dunes, Colorado Desert, Southeastern California, Daniel R. Muhs, Charles A. Bush, Scott D. Cowherd, Shannon Mahan Jan 1995

Geomorphic And Geochemical Evidence For The Source Of Sand In The Algodones Dunes, Colorado Desert, Southeastern California, Daniel R. Muhs, Charles A. Bush, Scott D. Cowherd, Shannon Mahan

United States Geological Survey: Staff Publications

The Algodones dunes of southeastern California comprise one of the largest active dune fields in the United States. The source of sand of the Algodones dunes is controversial, and the source of stabilized aeolian sand in the adjacent East Mesa area has not been investigated at all. We used mineralogical compositions and trace element concentrations to ascertain the most likely source of sand for these active and stabilized dunes. Results indicate that alluvium derived from the San Bernardino Mountains, which enters the Salton trough to the northwest of the dune fields, and alluvium derived from the Chocolate Mountains, which is …

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Carbonate Deposition, Pyramid Lake Subbasin, Nevada: 2. Lake Levels And Polar Jet Stream Positions Reconstructed From Radiocarbon Ages And Elevations Of Carbonates (Tufas) Deposited In The Lahontan Basin, Larry Benson, Michaele Kashgarian, Meyer Rubin Jan 1995

Carbonate Deposition, Pyramid Lake Subbasin, Nevada: 2. Lake Levels And Polar Jet Stream Positions Reconstructed From Radiocarbon Ages And Elevations Of Carbonates (Tufas) Deposited In The Lahontan Basin, Larry Benson, Michaele Kashgarian, Meyer Rubin

United States Geological Survey: Staff Publications

Most of the tufas in the Pyramid Lake subbasin were deposited within the last 35,000 yr, including most of the mound tufas that border the existing lake. Many of the older tufas (> 21,000 yr B.P.) contained in the mounds were formed in association with ground-water discharge. The radiocarbon (14C) ages of the older tufas represent maximum estimates of the time of their formation. Lake Lahontan experienced large and abrupt rises in level at ~ 22,000, 15,000, and 11,000 yr B.P. and three abrupt recessions in level at ~ 16,000, 13,600, and 10,000 yr B.P. The lake-level rises …

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Fault Healing Inferred From Time Dependent Variations In Source Properties Of Repeating Earthquakes, Chris Marone, John E. Vidale, William L. Ellsworth Jan 1995

Fault Healing Inferred From Time Dependent Variations In Source Properties Of Repeating Earthquakes, Chris Marone, John E. Vidale, William L. Ellsworth

United States Geological Survey: Staff Publications

We analyze two sets of repeating earthquakes on the Calaveras fault to estimate in-situ rates of fault strengthening (healing). Earthquake recurrence intervals t, range from 3 to 803 days. Variations in relative moment and duration are combined to study changes in stress drop, rupture dimension, rupture velocity, and particle velocity as a function of tr. Healing rates and source variations are compared with predictions of laboratory derived friction laws. Two interpretations of event duration τ are used: one in which τ: is given by the ratio of slip to particle velocity and one in which it scales as …

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Kinetics Of Pressure Solution At Halite-Silica Interfaces And Intergranular Clay Films, Stephen H. Hickman, Brian Evans Jan 1995

Kinetics Of Pressure Solution At Halite-Silica Interfaces And Intergranular Clay Films, Stephen H. Hickman, Brian Evans

United States Geological Survey: Staff Publications

Pressure solution is widely regarded as a potentially important deformation
mechanism along crustal faults and during a diagenesis, yet the mechanisms and kinetics of this process remain highly controversial. To better understand the fundamental factors controlling the rates of pressure solution at the grain-to-grain scale, we conducted experiments in which convex halite lenses were pressed against fiats of fused silica in brine. Fluid pressures were maintained at 0.1 MPa; temperatures and mean contact normal stresses ranged from 8.3 ° to 90.2 °C and 0.5 to 13.5 MPa, respectively. The geometry and growth rate of the contact spot between the two …

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Nebraska Groundwater In Storage, Conservation Survey Division Jan 1995

Nebraska Groundwater In Storage, Conservation Survey Division

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Self-Study Report 1995 Jan 1995

Self-Study Report 1995

Conservation and Survey Division: Faculty and Staff Publications

This Self-Study Report for the Conservation and Survey Division (CSD) is a profile of the unit at this point in time. It is presented in three major sections: (1) Background; (2) Current Programs and Achievements; and (3) A Vision of the Future. All sections draw heavily upon documents, staff input, and committee activities going on within the division.

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Resource News-Winter 1995 Jan 1995

Resource News-Winter 1995

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Guidelines For Decommissioning Water Wells, How To Plug Water Wells, Duane A. Eversoll, Delynn R. Hay, Rod J. Tremblay Jan 1995

Guidelines For Decommissioning Water Wells, How To Plug Water Wells, Duane A. Eversoll, Delynn R. Hay, Rod J. Tremblay

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Annual Outflow And Annual Inflow Of Water From/To Nebraska, 1950-1994, Conservation And Survey Division Jan 1995

Annual Outflow And Annual Inflow Of Water From/To Nebraska, 1950-1994, Conservation And Survey Division

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Static Pressure At The Ground Under Atmospheric Flow Across A Windbreak, James R. Brandle Jan 1995

Static Pressure At The Ground Under Atmospheric Flow Across A Windbreak, James R. Brandle

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Design Of A Multi-Level Monitoring Well For Continuous Sample Collection, J. F. Ayers, D. C. Gosselin Jan 1995

Design Of A Multi-Level Monitoring Well For Continuous Sample Collection, J. F. Ayers, D. C. Gosselin

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Thayer County Test Hole Logs, Raymond R. Burchett, Frank A. Smith Jan 1995

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

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Boyd County Test Hole Logs, Susan Olafsen Lackey, Frank A. Smith, Raymond R. Burchett Jan 1995

Boyd County Test Hole Logs, Susan Olafsen Lackey, Frank A. Smith, Raymond R. Burchett

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Dissociation Quotients Of Succinic Acid In Aqueous Sodium Chloride Media To 225°C, Richard Kettler, Donald A. Palmer, David J. Wesolowski Jan 1995

Dissociation Quotients Of Succinic Acid In Aqueous Sodium Chloride Media To 225°C, Richard Kettler, Donald A. Palmer, David J. Wesolowski

Department of Earth and Atmospheric Sciences: Faculty Publications

The first and second molal dissociation quotients of succinic acid were measured potentiometrically with a hydrogen-electrode, concentration cell. These measurements were carried out from 0 to 225"C over 25 ° intervals at five ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The dissociation quotients from this and two other studies were combined and treated with empirical equations to yield the following thermodynamic quantities for the first acid dissociation equilibrium at 25°C: logK1a = -4.210±0.003; Δ H1̊a = 2.9±0.2 kJ-mol - 1 ; ΔS1̊a = -71±1 J-mol - 1 -K -1; and ΔCp̊,1a = -98±3 …

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Campanian Dwarf Calcareous Nannofossils From Wodejebato Guyot, Elisabetta Erba, David K. Watkins, Jörg Mutterlose Jan 1995

Campanian Dwarf Calcareous Nannofossils From Wodejebato Guyot, Elisabetta Erba, David K. Watkins, Jörg Mutterlose

Department of Earth and Atmospheric Sciences: Faculty Publications

Calcareous nannofossils occur in lagoonal sediments recovered from Sites 873, 874, and 877 drilled on Wodejebato Guyot in the central Pacific Ocean. Nannofloras are present only in a few layers, from which several smear slides were prepared. All the specimens were counted, and the relative abundance of taxa was computed as percentages. Assemblages are characterized by excellent preservation, very high diversity (= number of taxa), but extremely low abundance. Both diversity and abundance decrease from the inner perimeter ridge along the northern edge of the atoll (Sites 877 and 874) to the inner lagoon (Site 873), but the assemblage composition …

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19. Pedogenic Alteration Of Basalts Recovered During Leg 144, Mary Anne Holmes Jan 1995

19. Pedogenic Alteration Of Basalts Recovered During Leg 144, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

Basalts erupted to form the atolls and guyots of the Western Pacific have been altered in various ways, ranging from hydrothermal alteration to subaerial weathering by meteoric waters in a tropical environment. Subaerial weathering has been moderate to extreme. Moderate subaerial weathering is expressed by dissolution or replacement of primary minerals (olivine, pyroxenes, plagioclase feldspar) and alteration of glassy or aphanitic matrix to clay minerals, goethite, and hematite. The clay minerals are kaolinite or a brown smectite. Kaolinite concentrations decrease downhole and smectite concentrations increase. Although primary minerals are generally not preserved, primary structures, such as vesicles (generally filled by …

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Converted Railroad Corridors As Avian Habitat In Southeast Nebraska, Kevin L. Poague Dec 1994

Converted Railroad Corridors As Avian Habitat In Southeast Nebraska, Kevin L. Poague

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

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Springtime Microwave Emissivity Changes In The Southern Kara Sea, Robert G. Crane, Mark R. Anderson Jul 1994

Springtime Microwave Emissivity Changes In The Southern Kara Sea, Robert G. Crane, Mark R. Anderson

Department of Earth and Atmospheric Sciences: Faculty Publications

Springtime microwave brightness temperatures over first-year ice are examined for the southern Kara Sea. Snow emissivity changes are revealed by episodic drops in the 37- to 18-GHz brightness temperature gradient ratio measured by the Nimbus 7 scanning multichannel microwave radiometer. We suggest that the negative gradient ratios in spring 1982 result from increased scatter at 37 GHz due to the formation of a near-surface hoar layer. This interpretation is supported by the results of a surface radiation balance model that shows the melt signature occurring at below freezing temperatures but under clear-sky conditions with increased solar input to the surface. …

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Drought Profile: Haryana State In North India, K. Kailasa Nathan Jun 1994

Drought Profile: Haryana State In North India, K. Kailasa Nathan

Drought Network News (1994–2001)

Haryana state is considered the breadbasket of India, along with the Punjab state. The effects of drought (and mitigation of those effects) are, therefore, of considerable importance for the state. This article considers the state’s drought profile through a study of six drought years in Haryana.

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Banded Agates, Origins And Inclusions, Roger K. Pabian, Andrejs Zarins Jun 1994

Banded Agates, Origins And Inclusions, Roger K. Pabian, Andrejs Zarins

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Seven Million Years Of Glaciation In Greenland, H. C. Larsen, A. D. Saunders, P. D. Clift, J. Beget, W. Wei, S. Spezzaferri, J. Ali, H. Cambray, A. Demant, G. Fitton, M. S. Fram, K. Fukuma, J. Gieskes, Mary Anne Holmes, J. Hunt, C. Lacasse, L. M. Larsen, H. Lykke-Andersen, A. Meltser, M. L. Morrison, N. Nemoto, N. Okay, S. Saito, C. Sinton, R. Stax, T. L. Vallier, D. Vandamme, R. Werner May 1994

Seven Million Years Of Glaciation In Greenland, H. C. Larsen, A. D. Saunders, P. D. Clift, J. Beget, W. Wei, S. Spezzaferri, J. Ali, H. Cambray, A. Demant, G. Fitton, M. S. Fram, K. Fukuma, J. Gieskes, Mary Anne Holmes, J. Hunt, C. Lacasse, L. M. Larsen, H. Lykke-Andersen, A. Meltser, M. L. Morrison, N. Nemoto, N. Okay, S. Saito, C. Sinton, R. Stax, T. L. Vallier, D. Vandamme, R. Werner

Department of Earth and Atmospheric Sciences: Faculty Publications

Glacial till, glaciomarine diamictites, and ice-rafted detritus found in marine cores collected off the shore of southeast Greenland record multiple Late Cenozoic glaciations beginning in the Late Miocene. Distinct rock assemblages and seismic stratigraphic control correlate the diamictites with glaciation of the southeast Greenland margin. Glaciers advanced to the sea during several intervals in the Pliocene and Pleistocene. North Atlantic glaciation may have nucleated in southern Greenland rather than further north because of the high mountains and the high levels of precipitation in this region.

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Geologic Framework Of The Niobrara River Drainage Basin And Adjacent Areas In South Dakota Generally East Of The 100th Meridian West Longitude And West Of The Missouri River, Robert F. Diffendal Jr., Michael R. Voorhies May 1994

Geologic Framework Of The Niobrara River Drainage Basin And Adjacent Areas In South Dakota Generally East Of The 100th Meridian West Longitude And West Of The Missouri River, Robert F. Diffendal Jr., Michael R. Voorhies

Department of Earth and Atmospheric Sciences: Faculty Publications

General geology and stratigraphy of the Niobrara River drainage basin in Nebraska and adjacent parts of South Dakota generally west of the Missouri River is reviewed. Of particular importance are the correlation of the Long Pine Formation of Pliocene age in Nebraska with the Herrick Gravels in South Dakota, the recognition of the members of the Ogallala Group named by Skinnner, Skinner and Gooris (1968) and by Skinner and Johnson (1984) in the basin, the acceptance of the relationships of the Miocene and older Tertiary units in the basin to those in the part of the study area in South …

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Fundamentals Of Groundwater Contamination, Darryll T. Pederson Feb 1994

Fundamentals Of Groundwater Contamination, Darryll T. Pederson

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

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Environments Of Aeolian Deposition In South-Central Nebraska During The Last Glacial Maximum, Zhao-Dong Feng, William C. Johnson, Robert F. Diffendal Jr. Jan 1994

Environments Of Aeolian Deposition In South-Central Nebraska During The Last Glacial Maximum, Zhao-Dong Feng, William C. Johnson, Robert F. Diffendal Jr.

Robert F. Diffendal, Jr., Publications

The Peoria loess of south-central Nebraska, deposited approximately during the last Glacial Maximum, can be subdivided into three zones: an upper laminated loess and a lower massive loess, separated by a dark gley zone in which bison bones and spruce charcoal are found. The lower Peoria unit is characterized by high organic matter content, relatively high bulk density, and common root channels. The upper Peoria unit has rhythmic patterns of two orders: strongly gleyed and weakly gleyed zones alternating in couplets about 2-5 m thick, and coarse- and fine-grained laminae of second order, about 2-4 mm thick. The strongly gleyed …

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Geomorphic And Structural Features Of The Alliance 1º × 2º Quadrangle, Western Nebraska, Discernible From Synthetic-Aperture Radar Imagery And Digital Shaded-Relief Maps, Robert F. Diffendal Jr. Jan 1994

Geomorphic And Structural Features Of The Alliance 1º × 2º Quadrangle, Western Nebraska, Discernible From Synthetic-Aperture Radar Imagery And Digital Shaded-Relief Maps, Robert F. Diffendal Jr.

Robert F. Diffendal, Jr., Publications

The digital shaded-relief map of the United States and the synthetic-aperture radar map of the Alliance Nebraska 1º x 2º area prepared by the U.S. Geological Survey (USGS) in the former case and for the USGS in the latter show oriented landforms and lineaments in northwest Nebraska. Parallel and subparallel hills and valleys developed on different geologic materials ranging from shales through sandstones to loess and eolian sand appear to be wind erosional features subsequently modified by running water. The long axes of these hills and valleys generally trend between N40"W and N50"W. Similar features also occur across major areas …

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Geochemical Evidence Of Saharan Dust Parent Material For Soils Developed On Quaternary Limestones Of Caribbean And Western Atlantic Islands, Daniel R. Muhs, Charles A. Bush, Kathleen C. Stewart, Tracy R. Rowland, Russell C. Crittenden Jan 1994

Geochemical Evidence Of Saharan Dust Parent Material For Soils Developed On Quaternary Limestones Of Caribbean And Western Atlantic Islands, Daniel R. Muhs, Charles A. Bush, Kathleen C. Stewart, Tracy R. Rowland, Russell C. Crittenden

United States Geological Survey: Staff Publications

Most previous workers have regarded the insoluble residues of high-purity Quatemary limestones (coral reefs and oolites) as the most important parent material for well-developed, clay-rich soils on Caribbean and western Atlantic islands, but this genetic mechanism requires unreasonable amounts of limestone solution in Quatemary time. Other possible parent materials from external sources are volcanic ash from the Lesser Antilles island arc and Saharan dust carried across the Atlantic Ocean on the northeast trade winds. Soils on Quatemary coral terraces and carbonate eolianites on Barbados, Jamaica, the Florida Keys (United States), and New Providence Island (Bahamas) were studied to determine which, …

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A Metapopulation Approach To Pitcher's Thistle (Cirsium Pitcheri) Recovery In Southern Lake Michigan Dunes, A. Kathryn Mceachern, Marlin L. Bowles, Noel B. Pavlovic Jan 1994

A Metapopulation Approach To Pitcher's Thistle (Cirsium Pitcheri) Recovery In Southern Lake Michigan Dunes, A. Kathryn Mceachern, Marlin L. Bowles, Noel B. Pavlovic

United States Geological Survey: Staff Publications

Successful recovery planning for a rare species relies upon knowledge of its life history and ecology, as well as an understanding of its habitat requirements and disturbance regime (Gilpin & Soule 1986, Lande 1988a). Species that depend upon early-successional or transient habitats in landscape mosaics present unique recovery challenges (Menges 1990). They require perpetuation of multiple populations within a shifting mosaic of local habitats. Recovery plans for these species must be formulated from an understanding of population demography within the context of community and landscape dynamics. Processes that maintain landscape mosaics must be given long-term protection if recovery is to …

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Thorium-230 Ages Of Corals And Duration Of The Last Interglacial Sea-Level High Stand On Oahu, Hawaii, Barney J. Szabo, Kenneth R. Ludwig, Daniel R. Muhs, Kathleen R. Simmons Jan 1994

Thorium-230 Ages Of Corals And Duration Of The Last Interglacial Sea-Level High Stand On Oahu, Hawaii, Barney J. Szabo, Kenneth R. Ludwig, Daniel R. Muhs, Kathleen R. Simmons

United States Geological Survey: Staff Publications

Thorium-230 ages of emergent marine deposits on Oahu, Hawaii, have a uniform dis- tribution of ages from ~114,000 to ~131,000 years, indicating a duration for the last interglacial sea-level high stand of ~17,000 years, in contrast to a duration of ~8000 years inferred from the orbitally tuned marine oxygen isotope record. Sea level on Oahu rose to ≥1 to 2 meters higher than present by 131,000 years ago or ~6000 years earlier than inferred from the marine record. Although the latter record suggests a shift back to glacial conditions beginning at ~119,000 years ago, the Oahu coral ages indicate a …

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