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Very High Middle Miocene Surface Productivity On The U.S. Mid-Atlantic Shelf Amid Glacioeustatic Sea Level Variability, Marci M. Robinson, Harry J. Dowsett, Timothy D. Herbert
Very High Middle Miocene Surface Productivity On The U.S. Mid-Atlantic Shelf Amid Glacioeustatic Sea Level Variability, Marci M. Robinson, Harry J. Dowsett, Timothy D. Herbert
United States Geological Survey: Staff Publications
The Miocene Climatic Optimum (MCO) provides important insights into how the climate system operates under elevated temperatures and atmospheric CO2 levels. Few western North Atlantic paleotemperature or paleoecological records exist from the MCO, despite their importance for understanding both regional and global climate dynamics. Here we present quantitative MCO paleoecological data from the western North Atlantic, specifically from the Baltimore Gas & Electric (BG&E) marine sediment core from southern Maryland, USA. We examine alkenones and planktic foraminifera and document the first sea surface temperature (SST) and productivity estimates for the MCO and the Middle Miocene Climate Transition (MMCT) from …
Hawaiian Forest Birds: The Past, Present And Future Status Of An Endangered Avifauna, Dennis A. Lapointe, Carter T. Atkinson, Paul C. Banko, Richard J. Camp, P. Marcos Gorresen, James D. Jacobi, Thane K. Pratt, Michael D. Samuel
Hawaiian Forest Birds: The Past, Present And Future Status Of An Endangered Avifauna, Dennis A. Lapointe, Carter T. Atkinson, Paul C. Banko, Richard J. Camp, P. Marcos Gorresen, James D. Jacobi, Thane K. Pratt, Michael D. Samuel
United States Geological Survey: Staff Publications
The Hawaiian forest birds are among the most endangered avifauna of the world. Entire bird groups have disappeared from the Hawaiian Islands, and of the more than fifty, historically-known species of Hawaiian honeycreeper, only 17 remain. Due to the extreme geographical isolation, few birds colonized the Hawaiian Islands but, released from direct competition, predation, and disease, these founders flourished and evolved amid the heterogeneous geography of the archipelago. This process of colonization and speciation is best characterized by the honeycreepers; the largest radiation of endemic forest birds in the Hawaiian Islands, or for that matter, birds on any oceanic archipelago. …
Change In Atmospheric Mineral Aerosols In Response To Climate: Last Glacial Period, Preindustrial, Modern, And Doubled Carbon Dioxide Climates, Natalie M. Mahowald, Daniel R. Muhs, Samuel Levis, Philip J. Rasch, Masaru Yoshioka, Charles S. Zender, Chao Luo
Change In Atmospheric Mineral Aerosols In Response To Climate: Last Glacial Period, Preindustrial, Modern, And Doubled Carbon Dioxide Climates, Natalie M. Mahowald, Daniel R. Muhs, Samuel Levis, Philip J. Rasch, Masaru Yoshioka, Charles S. Zender, Chao Luo
United States Geological Survey: Staff Publications
Desert dust simulations generated by the National Center for Atmospheric Research’s Community Climate System Model for the current climate are shown to be consistent with present day satellite and deposition data. The response of the dust cycle to last glacial maximum, preindustrial, modern, and doubled-carbon dioxide climates is analyzed. Only natural (non-land use related) dust sources are included in this simulation.
Fine-Scale Structure Of The San Andreas Fault Zone And Location Of The Safod Target Earthquakes, C. Thurber, S. Roecker, H. Zhang, S. Baher, W. Ellsworth
Fine-Scale Structure Of The San Andreas Fault Zone And Location Of The Safod Target Earthquakes, C. Thurber, S. Roecker, H. Zhang, S. Baher, W. Ellsworth
United States Geological Survey: Staff Publications
We present results from the tomographic analysis of seismic data from the Parkfield area using three different inversion codes. The models provide a consistent view of the complex velocity structure in the vicinity of the San Andreas, including a sharp velocity contrast across the fault. We use the inversion results to assess our confidence in the absolute location accuracy of a potential target earthquake. We derive two types of accuracy estimates, one based on a consideration of the location differences from the three inversion methods, and the other based on the absolute location accuracy of ‘‘virtual earthquakes.’’ Location differences are …
Distribution, Speciation, And Transport Of Mercury In Stream-Sediment, Stream-Water, And Fish Collected Near Abandoned Mercury Mines In Southwestern Alaska, Usa, John E. Gray, Peter M. Theodorakos, Elizabeth A. Bailey, Ralph R. Turner
Distribution, Speciation, And Transport Of Mercury In Stream-Sediment, Stream-Water, And Fish Collected Near Abandoned Mercury Mines In Southwestern Alaska, Usa, John E. Gray, Peter M. Theodorakos, Elizabeth A. Bailey, Ralph R. Turner
United States Geological Survey: Staff Publications
Concentrations of total Hg, Hg(II), and methylmercury were measured in stream-sediment, stream-water, and fish collected downstream from abandoned mercury mines in southwestern Alaska to evaluate environmental effects to surrounding ecosystems. These mines are found in a broad belt covering several tens of thousands of square kilometers, primarily in the Kuskokwim River basin. Mercury ore is dominantly cinnabar (HgS), but elemental mercury (Hg °) is present in ore at one mine and near retorts and in streams at several mine sites. Approximately 1400 t of mercury have been produced from the region, which is approximately 99% of all mercury produced from …
Geochemical And Mineralogical Evidence From Eolian Sediments For Northwesterly Mid-Holocene Paleowinds, Central Kansas, Usa, Alan F. Arbogast, Daniel R. Muhs
Geochemical And Mineralogical Evidence From Eolian Sediments For Northwesterly Mid-Holocene Paleowinds, Central Kansas, Usa, Alan F. Arbogast, Daniel R. Muhs
United States Geological Survey: Staff Publications
A prominent (4500 km2) dune field in the Great Plains is the Great Bend Sand Prairie of south-central Kansas. Dunes here overlie late Quaternary alluvium and were reactivated extensively in the late Holocene. Geomorphic and soil evidence suggests that the most likely eolian sand source is the Arkansas River valley to the northwest. Nevertheless, orientations of stabilized dunes indicate that the most recent dune-forming winds came from the south or southwest, in agreement with modern wind data.
Mineralogy and trace element concentrations in eolian sands of the Great Bend Sand Prairie are similar to those of the Arkansas …
A Memorial For William V. Sliter, Robert G. Douglas, Jere H. Lipps, James C. Ingle Jr., John Barron
A Memorial For William V. Sliter, Robert G. Douglas, Jere H. Lipps, James C. Ingle Jr., John Barron
United States Geological Survey: Staff Publications
William V. (Bill) Sliter, an internationally known micropaleontologist and research geologist for the U.S. Geological Survey, passed away suddenly, October, 1997, while talking to a colleague in his office. In his honor, B. Huber, T. Bralower, and M. Leckie organized a keynote symposium ‘‘Paleoecological and Geochemical Signatures of Cretaceous Anoxic Events’’ at the 1998 annual meeting of the Geological Society of America in Toronto, Canada. This theme issue of the Journal of Foraminiferal Research contains the published papers from the symposium and is dedicated to his memory.
An Evaluation Of Methods For Identifying And Interpreting Buried Soils In Late Quaternary Loess In Alaska, Daniel R. Muhs, Thomas A. Ager, Josh M. Been, Joseph G. Rosenbaum, Richard L. Reynolds
An Evaluation Of Methods For Identifying And Interpreting Buried Soils In Late Quaternary Loess In Alaska, Daniel R. Muhs, Thomas A. Ager, Josh M. Been, Joseph G. Rosenbaum, Richard L. Reynolds
United States Geological Survey: Staff Publications
The presence of buried soils in Alaskan loess is controversial, and therefore criteria for identifying buried soils in these deposits need to be evaluated. In this paper, morphologic and chemical criteria for identifying buried soils are evaluated by studying modern soils developed mostly in Holocene loess under tundra, boreal forest, and transitional coastal-boreal forest vegetation in different parts of Alaska. Data from modern Alaskan soils that developed under vegetation similar to that of the present indicate that soil morphology, organic-matter concentrations, and P concentrations can be useful diagnostic tools for identifying buried soils. Soil morphologic criteria, particularly horizon colors and …
Three-Dimensional Upper Crustal Velocity Structure Beneath San Francisco Peninsula, California, Tom Parsons, Mary Lou Zoback
Three-Dimensional Upper Crustal Velocity Structure Beneath San Francisco Peninsula, California, Tom Parsons, Mary Lou Zoback
United States Geological Survey: Staff Publications
This paper presents new seismic data from, and crustal models of the San Francisco Peninsula. In much of central California the San Andreas fault juxtaposes the Cretaceous granitic Salinian terrane on its west and the Late Mesozoic/Early Tertiary Franciscan Complex on its east. On San Francisco Peninsula, however, the present-day San Andreas fault is completely within a Franciscan terrane, and the Pilarcitos fault, located southwest of the San Andreas, marks the Salinian-Franciscan boundary. This circumstance has evoked two different explanations: either the Pilarcitos is a thrust fault that has pushed Franciscan rocks over Salinian rocks or the Pilarcitos is a …
Sr-Isotope Record Of Quaternary Marine Terraces On The California Coast And Off Hawaii, Kenneth R. Ludwig, Daniel R. Muhs, Kathleen R. Simmons, James G. Moore
Sr-Isotope Record Of Quaternary Marine Terraces On The California Coast And Off Hawaii, Kenneth R. Ludwig, Daniel R. Muhs, Kathleen R. Simmons, James G. Moore
United States Geological Survey: Staff Publications
Strontium-isotopic ratios of dated corals have been obtained from submerged reefs formed during Quaternary glacial periods off the Hawaiian islands. These data, combined with data from deep-sea sediments, tightly constrain the secular variation of marine 87Sr/86Sr for the past 800,000 yr. Although long-term trends are apparent, no significant (>0.02‰), rapid (<100,000 yr) excursions in 87Sr/86Sr were resolved nor did we observe any samples with 87Sr/86Sr greater than that of modern seawater. Strontium in mollusks from elevated marine terraces formed during interglacial periods on the southern California coast show resolvable and consistent variations in …
State Of Stress And Modern Deformation Of The Northern Basin And Range Province, Mary Lou Zoback
State Of Stress And Modern Deformation Of The Northern Basin And Range Province, Mary Lou Zoback
United States Geological Survey: Staff Publications
Constraints on the current stress regime of the actively extending northern Basin and Range province are provided by deformation data (focal mechanisms and fault slip studies), hydraulic fracturing in situ stress measurements, borehole elongation ("breakouts") analyses, and alignment of young volcanic vents. The integrated data indicate significant variations both in principal stress orientations and magnitudes. An approximately E-W least principal stress direction appears to characterize both the eastern and western margins of the Basin and Range province, whereas in the active interior parts of the province extension occurs in response to a least principal stress oriented NW to N60 °W. …
Sedimentology Of The Upper Triassic Chinle Formation Southeastern Utah: Paleoclimatic Implications, Russell F. Dubiel
Sedimentology Of The Upper Triassic Chinle Formation Southeastern Utah: Paleoclimatic Implications, Russell F. Dubiel
United States Geological Survey: Staff Publications
The Upper Triassic Chinle Formation in southeastern Utah was deposited in a complex fluvial-deltaic-lacustrine system. The Chinle records the evolution of a continental system in response to variations in climate, tectonics, and sediment supply. Chinle strata represent deposits of fluvial channels and floodplains, lacustrine deltas, lacustrine basins, and lacustrine and playa mudflats. These rocks include a variety of vertebrate, invertebrate, and plant fossils, trace fossils, and paleosols that provide information on depositional environments, water tables, and paleoclimate.
Sedimentologic and paleontologic interpretations both support an interpretation of abundant lakes, streams, and marshes with high, but fluctuating water tables for all but …
Diatom Stratigraphy Of The Lower Pliocene Part Of The Sisquoc Formation, Harris Grade Section, California, John A. Barron, Jack G. Baldau
Diatom Stratigraphy Of The Lower Pliocene Part Of The Sisquoc Formation, Harris Grade Section, California, John A. Barron, Jack G. Baldau
United States Geological Survey: Staff Publications
Lower Pliocene diatoms were studied from the Sisquoc Formation and lowermost Foxen Mudstone, exposed along Hams Grade north of Lompoc, California, to refine the diatom biostratigraphy of post-Monterey Formation sediments in California. Sixty-seven diatom taxa were identified in the 25 samples examined from the 790-m thick (2950-ft) section. The diatoms are assignable to the uppermost Nitzschia reinholdii Zone and Thalassiosira oestrupii Zone of Damn (1981), and five tentative subzones for local correlation are proposed. Regional correlations and taxon occurrence are discussed, and the base of the Nitzschia reinholdii Zone is redefined as at the last occurrence of Thalassionema schraderi.
The Distribution Of Natural Fractures And Joints At Depth In Crystalline Rock, Donald A. Seeburger, Mark D. Zoback
The Distribution Of Natural Fractures And Joints At Depth In Crystalline Rock, Donald A. Seeburger, Mark D. Zoback
United States Geological Survey: Staff Publications
This paper presents the results of studies of the natural fracture distribution encountered in 10 test wells drilled in three areas of the United States. Seven of the wells were drilled to depths of 200-250m, while three were drilled to depths of about 1 km. Using an ultrasonic borehole televiewer, fracture depths, strikes, and dips were determined. Steeply dipping fractures were found throughout each of the wells, and in general, few horizontal fractures were observed. Statistically significant fracture pole concentrations were found for each well which were basically invariant with depth, although some variation of fracture orientation with depth was …
Miocene Mammals And Central American Seaways, Frank C. Whitmore Jr., Robert H. Stewart
Miocene Mammals And Central American Seaways, Frank C. Whitmore Jr., Robert H. Stewart
United States Geological Survey: Staff Publications
The fossil mammal faunas of North and South America indicate that the two continents were separated from Paleocene or earlier time until the late Pliocene. Unfortunately our almost complete ignorance of the Tertiary land mammals of Central America, the geology of this large area, makes reconstruction of the Tertiary zoogeography of the region between the continents an exercise involving considerable speculation.