Rocky Mountain (56th Annual) and Cordilleran (100th Annual) Joint Meeting (May 3–5, 2004)

Paper No. 16
Presentation Time: 8:00 AM-5:00 PM


LACY, B. and FRANCIS, Robert D., Department of Geological Sciences, California State Univ at Long Beach, 1250 Bellflower Boulevard, Long Beach, CA 90840,

GPS-based mapping at a scale of 1:3000 reveals a detachment involving Cambrian and Ordovician rocks near Currant Gap along Highway 6 (about six miles northeast of the town of Currant) in the southern White Pine Range, east central Nevada. In contrast, previous mappers proposed a strike slip or transfer fault called the Current Summit fault (CSF) to explain juxtaposition of Devonian and Cambrian rocks along a jasperoided contact, and an apparent horizontal separation of Paleozoic strata at the south end of the White Pine Range.

Our mapping shows details along this contact that are inconsistent with the existence of a strike slip fault. Alignment of several jasperoid knobs in some areas along a supposed trace of a steep fault is shown by differential GPS locations (accurate to within 10 feet) not to exist. In Currant Gap, about 1.5 square miles consist of Cambrian Pole Canyon limestone, overlain by isolated patches of Ordovician Eureka Quartzite and Fish Haven Dolomite. Small slivers of Cambrian Lincoln Peak Formation are found under many of the Ordovician patches, along with extensive silicification. Upper Cambrian Dunderberg and Windfall formations are entirely absent in the mapped area. Previous mapping shows more patches of Eureka as many as two miles south of our mapped area. East of Current Gap are mapped patches of Ordovician and Devonian rocks, with extensive brecciation and silicification. Contacts are highly sinuous, and have very low dips. One exception is a small fault that dips at 52 degrees; this fault appears to be right lateral, rather than left lateral as the CSF has been previously described.

We propose the existence of a detachment fault, the Currant Gap detachment, that involves the Cambrian Lincoln Peak formation, a shale, as the ductile unit. The lower plate consists of lower Cambrian units such as Pole Canyon, and upper Cambrian units are completely attenuated, leaving Ordovician as the upper plate.