Publications
Publications from the staff of the Geology, Minerals, Energy, and Geophysics Science Center
Filter Total Items: 2354
Magnetostratigraphic correlations of Permian-Triassic marine-to-terrestrial sections from China
We have studied three Permian–Triassic (PT) localities from China as part of a combined magnetostratigraphic, 40Ar/39Ar and U–Pb radioisotopic, and biostratigraphic study aimed at resolving the temporal relations between terrestrial and marine records across the Permo-Triassic boundary, as well as the rate of the biotic recovery in the Early Triassic. The studied sections from Shangsi (Sichuan Pro
Authors
J.M.G. Glen, S. Nomade, J.J. Lyons, I. Metcalfe, R. Mundil, P.R. Renne
Geomorphic controls on mercury accumulation in soils from a historically mined watershed, Central California Coast Range, USA
Historic Hg mining in the Cache Creek watershed in the Central California Coast Range has contributed to the downstream transport of Hg to the San Francisco Bay-Delta. Different aspects of Hg mobilization in soils, including pedogenesis, fluvial redistribution of sediment, volatilization and eolian transport were considered. The greatest soil concentrations (>30 mg Hg kg-1) in Cache Creek are asso
Authors
J.M. Holloway, M. B. Goldhaber, J.M. Morrison
Evidence for prolonged mid-Paleozoic plutonism and ages of crustal sources in east-central Alaska from SHRIMP U-Pb dating of syn-magmatic, inherited, and detrital zircon
Sensitive high-resolution ion microprobe (SHRIMP) U–Pb analyses of igneous zircons from the Lake George assemblage in the eastern Yukon–Tanana Upland (Tanacross quadrangle) indicate both Late Devonian (∼370 Ma) and Early Mississippian (∼350 Ma) magmatic pulses. The zircons occur in four textural variants of granitic orthogneiss from a large area of muscovite–biotite augen gneiss. Granitic orthogne
Authors
Cynthia Dusel-Bacon, I.S. Williams
Audiomagnetotelluric investigation of Snake Valley, eastern Nevada and western Utah
Audiomagnetotelluric (AMT) data along four profiles in western Snake Valley and the corresponding two-dimensional (2-D) inverse models reveal subsurface structures that may be significant to ground-water investigations in the area. The AMT method is a valuable tool for estimating the electrical resistivity of the earth over depth ranges from a few meters to less than one kilometer. The method has
Authors
Darcy McPhee, Keith Pari, Frank Baird
Processes that initiate turbidity currents and their influence on turbidites: A marine geology perspective
How the processes that initiate turbidity currents influence turbidite deposition is poorly understood, and many discussions in the literature rely on concepts that are overly simplistic. Marine geological studies provide information on the initiation and flow path of turbidity currents, including their response to gradient. In case studies of late Quaternary turbidites on the eastern Canadian and
Authors
David J. W. Piper, William R. Normark
Late Quaternary paleoclimate of western Alaska inferred from fossil chironomids and its relation to vegetation histories
Fossil Chironomidae assemblages (with a few Chaoboridae and Ceratopogonidae) from Zagoskin and Burial Lakes in western Alaska provide quantitative reconstructions of mean July air temperatures for periods of the late-middle Wisconsin (~39,000-34,000 cal yr B.P.) to the present. Inferred temperatures are compared with previously analyzed pollen data from each site summarized here by indirect ordina
Authors
Joshua Kurek, Les C. Cwynar, Thomas A. Ager, Mark B. Abbott, Mary E. Edwards
Rapid measurement of field-saturated hydraulic conductivity for areal characterization
To provide an improved methodology for characterizing the field‐saturated hydraulic conductivity (Kfs) over broad areas with extreme spatial variability and ordinary limitations of time and resources, we developed and tested a simplified apparatus and procedure, correcting mathematically for the major deficiencies of the simplified implementation. The methodology includes use of a portable, fallin
Authors
J. R. Nimmo, K. M. Schmidt, K. S. Perkins, J. D. Stock
Hydrologic characterization of desert soils with varying degrees of pedogenesis: 1. field experiments evaluating plant-relevant soil water behavior
To assess the eff ect of pedogenesis on the soil moisture dynamics infl uencing the character and quality of ecological habitat, we conducted infi ltration and redistribution experiments on three alluvial deposits in the Mojave National Preserve: (i) recently deposited active wash sediments, (ii) a soil of early Holocene age, and (iii) a highly developed soil of late Pleistocene age. At each, we p
Authors
John R. Nimmo, Kim S. Perkins, Kevin M. Schmidt, David M. Miller, Jonathan D. Stock, Kamini Singha
New fusulinids from Lower Permian turbidites at Conglomerate Mesa, southeastern inyo Mountains, east-central California
Seven previously unrecognized fusulinid species from Lower Permian (Wolfcampian and Leonardian) turbidites near Conglomerate Mesa in east-central California, four of which are named as new species, are here described and figured. The four new species are Schwagerina merriami, S. wildei, Parafusulina mackevetti, and Skinnerella rossi. These fusulinid species have close affinities to similar taxa in
Authors
C. H. Stevens, P. Stone
Assessment of undiscovered oil and gas in the arctic
Among the greatest uncertainties in future energy supply and a subject of considerable environmental concern is the amount of oil and gas yet to be found in the Arctic. By using a probabilistic geology-based methodology, the United States Geological Survey has assessed the area north of the Arctic Circle and concluded that about 30% of the world’s undiscovered gas and 13% of the world’s undiscover
Authors
Donald L. Gautier, Kenneth J. Bird, Ronald R. Charpentier, Arthur Grantz, David W. Houseknecht, Timothy R. Klett, Thomas E. Moore, Janet K. Pitman, Christopher J. Schenk, John H. Schuenemeyer, Kai Sorensen, Marilyn E. Tennyson, Zenon C. Valin, Craig J. Wandrey
Past climate variability and change in the Arctic and at high latitudes
Paleoclimate records play a key role in our understanding of Earth's past and present climate system and in our confidence in predicting future climate changes. Paleoclimate data help to elucidate past and present active mechanisms of climate change by placing the short instrumental record into a longer term context and by permitting models to be tested beyond the limited time that instrumental me
Authors
Richard B. Alley, Julie Brigham-Grette, Gifford H. Miller, Leonid Polyak