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Introduction This report contains a new geologic map at 1:50,000 scale, derived from a set of geologic map databases containing information at a resolution associated with 1:24,000 scale, and a new description of geologic map units and structural relationships in the mapped area. The map database represents the integration of previously...

The USGS is currently leading an effort to compile published geological information on Quaternary faults, folds, and earthquake-induced liquefaction in order to develop an internally consistent database on the locations, ages, and activity rates of major earthquake-related features throughout the United States. This report is the compilation for such features in the Central and...

This study shows the lithology, thickness, distribution, and correlation of Lower and Upper Cretaceous rocks in central and eastern Montana. The described stratigraphic units range from the Aptian Kootenai Formation (oldest) to the Maastrichtian Hell Creek Formation (youngest). An included text report describes the units, and most formations or members...

The introduction of nutrients from chemical fertilizer, animal manure, wastewater, and atmospheric deposition to the eastern Iowa environment creates a large potential for nutrient transport in watersheds. Agriculture constitutes 93 percent of all land use in eastern Iowa. As part of the U.S. Geological Survey National Water Quality Assessment Program,...

The Southern California Areal Mapping Project (SCAMP) of Geologic Division has undertaken regional geologic mapping investigations in the Lucerne Valley area co-sponsored by the Mojave Water Agency and the San Bernardino National Forest. These investigations span the Lucerne Valley basin from the San Bernardino Mountains front northward to the basin...

Geologic mapping shows Middle Proterozoic strata form two packages of strata north and south of the Tertiary Lem Peak normal fault. Strata north of the fault, the main focus of this report, contain thicknesses and lithofacies of the Big Creek and Apple Creek formations of the Lemhi Group that contrast...

An integrated assessment of the water quality in streams and aquifers in the Wapsipinicon, Iowa, Cedar, and Skunk River basins was conducted in 1996 through 1998 as part of the Eastern Iowa Basins (EIWA) study unit of the U.S. Geological Survey's National Water-Quality Assessment Program (NAWQA). The EIWA study unit...

Three new U-Pb zircon ages and the Pb-Sr-Nd isotopic systematics of 24 whole-rock samples from mainly plutonic rocks of the Sierra Madre and Medicine Bow Mountains near the Colorado-Wyoming border help establish the Green Mountain magmatic arc as a Paleoproterozoic, variably eroded, island arc terrane. The Green Mountain magmatic arc,...

Twenty-five new 40Ar/39Ar ages from volcanic rocks and veins in the western San Juan Mountains clarify relationships between volcanism and mineralization in this classic area. Five calc-alkaline ash-flow sheets erupted from caldera sources (Ute Ridge, Blue Mesa, Dillon Mesa, Sapinero Mesa, and Crystal Lake Tuffs) from 28.6 to 27.6 Ma. This is a...

This paper compares four permanent displacement models based on Newmark's sliding-block analogy for assessing regional seismic slope-performance. The models vary primarily by the ground motion descriptor used to correlate with Newmark displacement. The first uses peak ground-acceleration (PGA). The second uses PGA but normalizes displacements by predominant period and equivalent...

Severe and prolonged droughts between 1961 and 1988, combined with increased demands for freshwater supplies in the United States, have resulted in a critical need to assess the potential for development of ground- and surface-water supplies. Rapid industrial growth and urban expansion have caused existing freshwater supplies to be used...

Simulations of future climate using general circulation models (GCMs) suggest that rising concentrations of greenhouse gases may have significant consequences for the global climate. Of less certainty is the extent to which regional scale (i.e., sub-GCM grid) environmental processes will be affected. In this chapter, a range of downscaling techniques...

The Nevada Test Site (NTS), in southern Nye County, Nevada, straddles significant pre-Tertiary structural and stratigraphic boundaries. Detailed stratigraphy and biostratigraphy of the Upper Paleozoic section delineates the regional trust sheets and constrains their burial histories. The Paleozoic rocks record three phases of contractional deformation, overprinted by strike-slip faulting. These...

This field trip provides an overview of the stratigraphic and structural evolution of the northern Sierra terrane, which forms a significant part of the wall rocks on the western side of the later Mesozoic Sierra Nevada batholith in California. The terrane consists of a pre-Late Devonian subduction complex (Shoo Fly...

The accumulation and melting of mountain snowpacks are major drivers of ecosystem processes in the Rocky Mountains. These include the influence of snow water equivalent (SWE) timing and amount of release on soil moisture for annual tree growth, and alpine stream discharge and temperature that control aquatic biota life histories....

The "World Map of Major Active Faults" Task Group is compiling published fault data, developing a digital database of the fault data, and preparing a series of maps for the United States and other countries in the western Hemisphere. The data is intended to portray the locations, ages, and activity rates of...

From 1985 through 1992, the Summitville open-pit mine produced gold from lowgrade ore using cyanide heap-leach techniques, a method to extract gold whereby the ore pile is sprayed with water containing cyanide, which dissolves the minute gold grains. Environmental problems due to mining activity at Summitville include significant increases in...

Compared to the Guadalupe Mountains of Texas and New Mexico the depositional environments of the Permian strata of the Glass Mountains (and adjacent Del Norte Mountains) are less well known. In general, the Guadalupian facies in the the Glass and Del Norte mountains changes from predominantly carbonate facies in the...

The filling history, hydrologic budget, and geomorphic development of ancient Lake Creede and its tributary basin are evaluated to determine the factors that controlled its character. The lake filled the Creede caldera that formed in the late Oligocene as a consequence of the eruption of the Snowshoe Mountain Tuff. The...

Sensitive, high-resolution, ion microprobe (SHRIMP) U-Pb zircon ages from a sample of the high-grade, hornblende-feldspathic Big Creek gneiss of the southeastern Sierra Madre, along with samples of a quartz monzonitic phase of the Boulder Creek batholith, help define timing of three major Paleoproterozoic thermo-tectonic events within the northern Colorado province...

Hemlock ravines in Delaware Water Gap National Recreation Area (DEWA) are highly valued because of their distinctive aesthetic, recreational and ecological qualities. We conducted a comparative study designed to determine the potential long-term consequences to aquatic communities of the suspected transition from hemlock-dominated forests to mixed hardwood forests as a result of hemlock woolly adelgid (HWA; Adelges...

Neotropical migrants are birds that breed in North America and winter primarily in Central and South America. Long-term population studies of birds in the Eastern United States indicated declines of some forest-dwelling birds, many of which winter in the Neotropics (Peterjohn and others 1995). These declines were attributed to loss...

We reexamine original felt reports from the 1811–1812 New Madrid earthquakes and determine revised isoseismal maps for the three principal mainshocks. In many cases we interpret lower values than those assigned by earlier studies. In some cases the revisions result from an interpretation of original felt reports with an appreciation...

The Okefenokee Swamp is a 160,000 ha freshwater wetland in Southeast Georgia, USA that developed in a landscape basin. Hydrologic variability across the swamp suggests that water-surface elevations are not uniform across the swamp. The topographic surface map discussed herein was developed to describe the swamp topography at local to...

Concentrations of naturally occurring arsenic in ground water vary regionally due to a combination of climate and geology. Although slightly less than half of 30,000 arsenic analyses of ground water in the United States were 1 μg/L, about 10% exceeded 10 μg/L....