Publications
Publications from the staff of the Geology, Minerals, Energy, and Geophysics Science Center
Filter Total Items: 2354
Lower crustal deformation beneath the central Transverse Ranges, southern California: Results from the Los Angeles Region Seismic Experiment
We present a P wave velocity model derived from active source seismic data collected during the 1994 Los Angeles Region Seismic Experiment. Our model extends previously published upper crustal velocity models to mantle depths. Our model was developed by both ray tracing through a layered model and calculating travel times through a gridded model. It includes an 8-km-thick crustal root centered ben
Authors
N. J. Godfrey, Gary S. Fuis, Victoria E. Langenheim, David A. Okaya, Thomas M. Brocher
Geochemistry of Mesozoic plutons, southern Death Valley region, California: Insights into the origin of Cordilleran interior magmatism
Mesozoic granitoid plutons in the southern Death Valley region of southeastern California reveal substantial compositional and isotopic diversity for Mesozoic magmatism in the southwestern US Cordillera. Jurassic plutons of the region are mainly calc-alkaline mafic granodiorites with εNdi of –5 to –16, 87Sr/86Sr i of 0.707–0.726, and 206Pb/204Pb i of 17.5–20.0. Cretaceous granitoids of the region
Authors
O.T. Ramo, J. P. Calzia, P.J. Kosunen
An upwelling model for the Phosphoria sea: A Permian, ocean-margin sea in the northwest United States
The Permian Phosphoria Formation, a petroleum source rock and world-class phosphate deposit, was deposited in an epicratonic successor basin on the western margin of North America. We calculate the seawater circulation in the basin during deposition of the lower ore zone in the Meade Peak Member from the accumulation rates of carbonate fluorapatite and trace elements. The model gives the exchange
Authors
D. Z. Piper, P. K. Link
Net ecosystem production: A comprehensive measure of net carbon accumulation by ecosystems
The conceptual framework used by ecologists and biogeochemists must allow for accurate and clearly defined comparisons of carbon fluxes made with disparate techniques across a spectrum of temporal and spatial scales. Consistent with usage over the past four decades, we define "net ecosystem production" (NEP) as the net carbon accumulation by ecosystems. Past use of this term has been ambiguous, be
Authors
J. T. Randerson, F. S. Chapin, J. W. Harden, J. C. Neff, M. E. Harmon
Characterization of arsenic species in microbial mats from an inactive gold mine
Filamentous cyanobacterial mats and Fe oxyhydroxide-rich bacterial mats collected near an inactive gold mine in California are enriched in arsenic (As) approximately 1000-fold relative to the waters in contact with them. The predominant organism in the cyanobacterial mat could not be identified using morphological characteristics, but the unique morphology of the sheath-forming β protobacterium Le
Authors
A. L. Foster, R. P. Ashley
Valley-fill alluviation during the Little Ice Age (ca. A.D. 1400-1880), Paria River basin and southern Colorado Plateau, United States
Valley-fill alluvium deposited from ca. A.D. 1400 to 1880 is widespread in tributaries of the Paria River and is largely coincident with the Little Ice Age epoch of global climate variability. Previous work showed that alluvium of this age is a mappable stratigraphic unit in many of the larger alluvial valleys of the southern Colorado Plateau. The alluvium is bounded by two disconformities resulti
Authors
Richard Hereford
A reconnaissance method for delineation of tracts for regional-scale mineral-resource assessment based on geologic-map data
The U.S. Geological Survey (USGS) is proposing to conduct a global mineral-resource assessment using geologic maps, significant deposits, and exploration history as minimal data requirements. Using a geologic map and locations of significant pluton-related deposits, the pluton-related-deposit tract maps from the USGS national mineral-resource assessment have been reproduced with GIS-based analysis
Authors
Gary L. Raines, Mark J. Mihalasky
Lower Colorado River: Framework, neogene deposits, incision, and evolution
No abstract available.
Authors
Keith A. Howard, Robert G. Bohannon
Magnetostratigraphy of the Eocene-Oligocene San Lorenzo and Vaqueros Formations, Santa Cruz Mountains, California: Implications for California biostratigraphic zonations
No abstract available.
Authors
D.R. Prothero, Joey Sutton, E. E. Brabb
Sedimentology of the Pennsylvanian and Permian Strathearn Formation, Northern Carlin Trend, Nevada; with a section on microfossil controls on age of the Strathearn Formation
Two framework-supported, poorly bedded conglomerate units of the middle Upper Pennsylvanian and middle Lower Permian Strathearn Formation belonging to the overlap assemblage of the Antler orogen are prominent in the northern Carlin trend. These horizons stratigraphically and temporally bracket thrust emplacement of a major allochthonous thrust plate of mainly quartzarenite of the Ordovician Vinini
Authors
Vladimir I. Berger, Donald A. Singer, Ted G. Theodore, Anita G. Harris, Calvin H. Stevens
Statistical compilation of NAPAP chemical erosion observations
In the mid 1980s, the National Acid Precipitation Assessment Program (NAPAP), in cooperation with the National Park Service (NPS) and the U.S. Geological Survey (USGS), initiated a Materials Research Program (MRP) that included a series of field and laboratory studies with the broad objective of providing scientific information on acid rain effects on calcareous building stone. Among the several e
Authors
Victor G. Mossotti, A. Raouf Eldeeb, Michael M. Reddy, Terry L. Fries, Mary Jane Coombs, Ron L. Schmiermund, Susan I. Sherwood
Digital database of mining-related features at selected historic and active phosphate mines, Bannock, Bear Lake, Bingham, and Caribou counties, Idaho
This report provides a description of data and processes used to produce a spatial database that delineates mining-related features in areas of historic and active phosphate mining in the core of the southeastern Idaho phosphate resource area. The data have varying degrees of accuracy and attribution detail. Classification of areas by type of mining-related activity at active mines is generally de
Authors
J. Douglas Causey, Phillip R. Moyle