COALESCING DETACHMENT FAULTS IN THE CURRANT GAP AREA OF THE WHITE PINE RANGE, EAST CENTRAL NEVADA; AN ALTERNATIVE TO THE CURRANT SUMMIT STRIKE SLIP FAULT

Horizontal separation in Paleozoic strata between the White Pine and Horse Ranges, east central Nevada, is better explained by detachment faulting than by the presence of a left lateral strike slip fault such as the supposed Currant Summit fault (CSF). Detailed field mapping of the White Pine Detachment fault (WPD) on the east side of the White Pine Range, using differential GPS to locate points within 10 feet, constrains the location of the trace of the previously proposed CSF to a narrow zone and shows that the WPD terminates at that zone. Seismic refraction analysis reveals a low angle surface, probably Cambrian carbonate, located 30 feet below the surface, that spans the entire zone where the trace of the CSF should occur. Interpretation of gravity data also do not support the presence of a steeply dipping interface at this location. Surface mapping farther west near Currant Gap also reveals Ordovician patches resting on Cambrian Pole Canyon Limestone with slivers of Cambrian Lincoln Peak (shale) between them. In the areas mapped there is no evidence of a steeply dipping fault exhibiting left lateral horizontal separation.

Previous mapping of the supposed CSF, going back to 1968, shows the trace of the fault only in alluvium. Areas of exposed Paleozoics, where our mapping is concentrated, showed low angle faults in these earlier maps. The previously mapped trace of the CSF has a right step just north of Currant Gap, but instead of a pop-up structure as would be expected in that location, alluvium occurs, along with Paleozoic outcrops that were not uplifted relative to surrounding areas.

Our mapping is consistent with an interpretation involving two coalescing detachments, the White Pine Detachment involving the Mississippian Chainman Shale and a second detachment involving the Cambrian Lincoln Peak Formation. Coalescence occurs at the point where the WPD apparently terminates. Apparent horizontal separation of Paleozoic strata is explained by uplift of offset domes in the metamorphic core infrastructure.