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Preliminary lithogeochemical map showing near-surface rock types in the Chesapeake Bay watershed, Virginia and Maryland

This preliminary experimental lithogeochemical map shows the distribution of rock types in the Virginia and Maryland parts of the Chesapeake Bay watershed. The map was produced digitally by classifying geologic-map units according to composition, mineralogy, and texture; rather than by age and stratigraphic relationships as shown on traditional geologic maps. This map differs from most lithologic
Authors
John D. Peper, Lucy McCartan, J. Wright Horton, James E. Reddy

Gypsum-karst collapse in the Black Hills, South Dakota-Wyoming, USA

No abstract available.
Authors
Jack B. Epstein

The East Range, northwestern Nevada: A neglected key to the tectonic history of the region

The East Range occupies a strategic position at the western edge of the exposed western facies terrane near the Paleozoic continental margin. There a Cambrian and Ordovician deep-water sequence including the Preble and Valmy Formations is overlain by middle to upper Paleozoic strata that are assigned to three separate stratigraphic sequences on published geologic maps of the range. The three seque
Authors
Keith B. Ketner, Bruce R. Wardlaw, Anita G. Harris, John E. Repetski

Constraints on timing and rates of late Cenozoic incision by the Colorado River in Glenwood Canyon, Colorado: A preliminary synopsis

No abstract available.
Authors
Robert M. Kirkham, Michael J. Kunk, Bruce Bryant, Randall K. Streufert

Hydrogeologic setting and potential for denitrification in ground water, Coastal Plain of southern Maryland

The types and distribution of Coastal Plain sediments in the Patuxent River Basin may contribute to relatively low concentrations of nitrate (typically less than 1 milligram per liter) in stream base flow because of the chemical reduction of dissolved nitrate (denitrification) in ground water. Water chemistry data from synoptic stream base-flow surveys in the Patuxent River Basin show higher disso
Authors
David E. Krantz, David S. Powars

Climatic variability in the eastern United States over the past millennium from Chesapeake Bay sediments

Salinity oscillations caused by multidecadal climatic variability had major impacts on the Chesapeake Bay estuarine ecosystem during the past 1000 yr. Microfossils from sediments dated by radiometry (14C, 137Cs, 210Pb) and pollen stratigraphy indicate that salinity in mesohaline regions oscillated 10-15 ppt during periods of extreme drought (low fresh-water discharge) and wet climate (high dischar
Authors
Thomas M. Cronin, Debra A. Willard, A. Karlsen, S. Ishman, S. Verardo, John McGeehin, R. Kerhin, C. Holmes, S. Colman, A. Zimmerman

Digital airborne time domain electromagnetic data from surveys over Cochiti Pueblo, Rio Puerco, and Rio Rancho, New Mexico

The Albuquerque-Santa Fe region is rapidly growing. The Santa Fe Group aquifer in the Middle Rio Grande Basin (MRGB) is the main source of municipal water for the greater Albuquerque metropolitan area and is more limited than previously thought (Thorn et al., 1993). The MRGB, as defined hydrologically and used here, is the area within the Rio Grande Valley extending from Cochiti Dam downstream to
Authors
Maria Deszcz-Pan, B. D. Rodriguez, J. P. Doucette, Michel Godbout, J. M. Williams, D. A. Sawyer, B. D. Stone, V. J. Grauch

Digital geologic map of the Harpers Ferry National Historical Park

No abstract available.
Authors
Scott Southworth, D. K. Brezinski, Randall C. Orndorff, Kerry M. Lagueux, Peter G. Chirico

Isotopic ages from intrusive rocks near the Stuyahok gold placer deposits, south-central Holy Cross quadrangle, Alaska: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1998

In the Stuyahok area of the south-central Holy Cross quadrangle, Alaska, felsic to intermediate dikes and sills intrude Lower Cretaceous volcanic and volcaniclastic rocks of the Koyukuk terrane. These previously undated intrusions are the probable source of at least 933 kg (30,000 oz) of past placer gold production. Additional placer, and perhaps lode, resources are likely present at Stuyahok. New
Authors
Marti L. Miller, Robert D. Tucker, Paul W. Layer, Thomas K. Bundtzen

Preliminary stratigraphic database for the subsurface Tertiary and uppermost Cretaceous sediments of Dorchester County, South Carolina

No abstract available.
Authors
Gregory Gohn, Laurel M. Bybell, Peter G. Chirico, R. A. Christopher, Lucy E. Edwards, N. O. Frederiksen, D. C. Prowell, Jean Self-Trail, Robert E. Weems