Principal Facts for Gravity Stations in the Dry Valley Area, West-Central Nevada and East-Central California

In June, 2002, the U.S. Geological Survey (USGS) established 143 new gravity
stations and 12 new rock samples in the Dry Valley area, 30 miles north of
Reno, Nevada, on the California - Nevada border (see fig. 1). This study
reports on gravity, magnetic, and physical property data intended for use in
modeling the geometry and depth of Dry Valley for groundwater analysis. It is
part of a larger study that aims to characterize the hydrologic framework of
several basins in Washoe County. Dry Valley is located south of the Fort Sage
Mountains and south-east of Long Valley, on USGS 7.5 quadrangles Constantia
and Seven Lakes (fig. 2). The Cretaceous granitic rocks and Tertiary volcanic
rocks that bound the sediment filled basin (fig. 3) may be especially important
to future modeling because of their impact on groundwater flow. The granitic
and volcanic rocks of Dry Valley exhibit densities and magnetic
susceptibilities higher than the overlaying sediments, and create a
distinguishable pattern of gravity and magnetic anomalies that reflect these
properties.