Publications

This rapid trip will explore wild fluvial and tectonic events resulting in scenic and rugged topography. The extreme differences in elevation caused valleys to be choked by alluvium and incised by the Colorado River drainage system.

Deposits in lower Mohave Valley and upper Topock Gorge near Topock, Arizona and Park Moabi, California record a succession of depositional and erosional events since late Miocene time that relate to the development of the Colorado River. Upper Miocene alluvial fans were deposited toward a depocenter east of the present valley bottom, indicating there was no valley outlet then through the...

Yellowstone National Park, rimmed by a crescent of older mountainous terrain, has at its core the Quaternary Yellowstone Plateau, an undulating landscape shaped by forces of volcanism, tectonism, and later glaciation. Its spectacular hydrothermal systems cap this landscape. From 1997 through 2003, the United States Geological Survey Mineral Resources Program conducted a multidisciplinary...

The U.S. Geological Survey (USGS) cooperated with the Afghanistan Geological Survey (AGS) of the Afghanistan Ministry of Mines to assess the undiscovered non-fuel mineral resources of Afghanistan between 2006 and 2007. This report presents the results of this work and contains chapters describing and assessing the mineral resources of Afghanistan. An accompanying Geographical Information...

The Newark Valley area, eastern Nevada is one of thirteen major ground-water basins investigated by the BARCAS (Basin and Range Carbonate Aquifer Study) Project. Gravity data are being used to help characterize the geophysical framework of the region. Although gravity coverage was extensive over parts of the BARCAS study area, data were sparse for a number of the valleys, including the...

Successful management of ecosystems containing historical mine wastes requires understanding of processes that are responsible for the distribution, concentration, and bioavailability of potentially toxic elements. U.S. Geological Survey (USGS) scientists recently completed several investigations at historical mine sites in the western United States. These investigations have improved...

This isostatic residual gravity map is part of an effort to map the three-dimensional distribution of rocks in Joshua Tree National Park, southern California. This map will serve as a basis for modeling the shape of basins beneath the Park and in adjacent valleys and also for determining the location and geometry of faults within the area. Local spatial variations in the Earth's gravity...

A geophysical investigation was undertaken as part of an effort to characterize the geologic framework influencing ground-water resources in east-central Nevada and west-central Utah. New gravity data were combined with existing aeromagnetic, drill-hole, and geologic data to help determine basin geometry, infer structural features, estimate depth to pre-Cenozoic basement rocks, and...

The Purisima Formation is an important upper Miocene and Pliocene stratigraphic unit in central California, cropping out from the coast at Point Reyes north of San Francisco to more extensive exposures in the Santa Cruz Mountains to the south. The fine-grained rocks in the lower parts of the Purisima Formation record a latest Miocene transgressive event, whereas the middle and upper...

We conducted geochronologic and pollen analyses from sediment cores collected in solution holes within marl prairies of Big Cypress National Preserve to reconstruct vegetation patterns of the last few centuries and evaluate the stability and longevity of marl prairies within the greater Everglades ecosystem. Based on radiocarbon dating and pollen biostratigraphy, these cores contain...

No abstract available.

Audiomagnetotelluric (AMT) data along thirteen profiles in Spring, Snake, and Three Lakes Valleys, and the corresponding two-dimensional (2-D) inverse models, are presented. The AMT method is a valuable tool for estimating the electrical resistivity of the Earth over depth ranges of a few meters to roughly one kilometer. It is important for revealing subsurface structure and stratigraphy...