RED RIDGE REVERSE FAULT, NORTHERN PANCAKE RANGE, CENTRAL NEVADA

The north to NNE trending, high angle, 15 km long Red Ridge fault (RRF) system in the northern Pancake Range Paleozoic window area is associated with structures consistent with a compressive tectonic environment, reverse displacement with easterly vergence. It lies in an area of greater shortening accommodation than areas to the mapped by Nolan and others (1974) to the north. The RRF has been mapped as a normal fault by most workers.

The RRF allochthon terminates on the north against a N45W trending oblique fault. To the RRF's east lies a steep Diamond Spring FM (DPF) ramp (autochthon) along its entire strike. The northern 6 km RRF segment soles an “eyelid structure” of Chainman Shale, Kinkhead Spring – Tripon Pass, Joana LS, Pilot Shale and a fragment of the uppermost Devils Gate Limestone. A few DPF conglomerate horses are embedded along the fault trace.

The eyelid pinches out to the south and the Chainman Shale lies along the trace to its southern terminus. The southern RRF trend also hosts a 6 KM long DPF horse – a detached limb of an anticline scavenged from an 8 KM long, easterly-verging fold in the autochthon. The southern RRF terminus is a fault system with possible oblique displacement against Oligocene volcanic flows.

The RRF allochthon continues from Red Ridge to the northwest in the form of a NW trending folded, ‘panel' with an east-dipping ?RRF daylight on its western edge. This part of the RRF allochthon terminates to the south against a tip line or fault within the Chainman-DPF mud lithosome. South of this more complexly deformed panel, the allochthon dips gently to the west possibly reflecting changes in the underlying autochthon from folded carbonate to the north to shales to the south.

RRF age is constrained by two features of the autochthon: an unnamed post-RRF pre-Sheep Pass FM monolithologic breccia (Late Cretaceous or older)and an undeformed, 2 KM wide, 108 MYO (Albian) dacite plug. The RRF must be post-Permian, pre-late Early Cretaceous in age. This fault system is most likely associated with a late phase, Early Jurassic expression of the Sonoma Orogeny.