Abstract

New geologic mapping and high-resolution seismic data from east-central Nevada shed light on the evolution of the northern Snake Range decollement (NSRD) and its relation to the present basins and ranges. We suggest that the NSRD originated in Oligocene time as a flat, 20-km-wide, 7-km-deep zone of decoupling between localized ductile stretching below and more widely distributed, high-angle normal faulting above. Younger east-dipping normal faults cut the western part of the NSRD, forming the tilted fault blocks and highly asymmetric grabens that constitute the Duck Creek Range-Duck Creek Valley and Schell Creek Range-Spring Valley, and folded the NSRD to its present antiformal geometry. These youngest faults flatten into pervasive subhorizontal reflectors at a depth of 10 to 15 km that we interpret as the youngest ductile-brittle transition.

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