Sequential Mesozoic and Cenozoic Tectonic Events in Grant Range and Railroad Valley, Nye County, Nevada

Donna M. H. Flanigan

A series of palinspastic geologic cross sections were constructed for the Grant Range-Railroad Valley (GR-RRV) area. This palinspastic reconstruction differs from previously published interpretations in two major ways. First, new granite age dates and a chronological framework deduced by Fryxell in 1984 in the central and southern Grant Range were applied, where possible, to the northern Grant Range. Second, recent drilling was correlated to outcrop interpretations. Results of this reconstruction suggest that significant tectonism affected the GR-RRV area earlier than previously believed.

Mesozoic compression produced east-vergent folding in the GR-RRV area, followed by Late Cretaceous intrusion. Local, possibly blind thrusting may have been associated with the intrusion. Above the granite dome, shallow, brittle, listric faulting and deeper low-angle attenuation faulting accommodated intrusion. After intrusion, relative quiescence prevailed during the deposition of the Sheep Pass Formation and the lower Garrett Ranch Group ignimbrite. Uplift in the middle and late Oligocene produced pervasive listric, normal, east-dipping faulting that may in part be represented by apparent growth faults within volcanics. Subsequent west-dipping listric faulting was in part gravity driven. High-angle Miocene normal faulting initiated the present structure.

All commercial oil fields in Railroad Valley are producing from Miocene and younger structures. However, an understanding of older structures will allow more accurate prediction of reservoirs within a particular, prospective, younger structure.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.