Abstract: Geologic Implications from Gravity Anomaly Maps of the Crescent Valley 1/2° × 1° Quadrangle Including Pine Valley, Nevada

Stephen L. Robbins, Courteney Williamson, Howard W. Oliver

Four hundred and twenty new gravity stations have been added to the data set (USGS, OF 91-386) for the Crescent Valley quadrangle, north-central Nevada (lat 40°00^prime to 40°30^primeN., long 116°00^prime to 117°00^primeW). These combined data provide new subsurface structural constraints in an area of geologic and economic importance. The quadrangle contains the mid-Miocene northern Nevada rift and the middle Paleozoic Roberts Mountains thrust. Pine Valley is one of only two valleys within Nevada that is currently producing oil. One of the largest gold discoveries in recent years was made at the southwestern end of Crescent Valley.

Complete Bouguer, isostatic residual (IRA), and horizontal gradient anomaly gravity maps have been generated and are included in this study. The IRA map shows that the Blackburn and Three Bar oil fields lie near a gravity saddle across the middle of the large (-32 mGal) gravity low over Pine Valley. At least three of the oil fields in Pine Valley were discovered on small gravity anomalies (Nevada Petroleum Society, 1990 Fieldtrip Guidebook). Interpretations of the IRA map, seismic data, and Jachens and Moring's (USGS, OF 90-404) density-depth model show Pine Valley to be the deepest basin in the quadrangle, with an estimated 5 km of Cenozoic fill. In the southwest portion of this quadrangle, a -28 mGal gravity low is centered over what may be a Tertiary caldera. The recent gold discov ry appears to be located near the northeastern boundary of the caldera.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994