FAULT GEOMETRY, BASIN EVOLUTION, AND DISPLACEMENT TRANSFER ALONG THE FISH LAKE VALLEY FAULT ZONE, EASTERN CALIFORNIA-SOUTHWESTERN NEVADA

The NW-striking Fish Lake Valley fault zone (FLVFZ) extends 80 km from southern Fish Lake Valley to its termination in northwestern Fish Lake Valley. The FLVFZ forms the northern segment of the right-oblique Death Valley-Furnace Creek-Fish Lake Valley fault zone, the longest active structure in the Eastern California Shear Zone. Recent geologic mapping and gravity analysis in the region have elucidated new structural links between the FLVFZ and major WNW-trending left-oblique transfer fault systems that stretch for over 60 km to the east. Gravity gradients and depth-to-basement models indicate that southern Fish Lake Valley is segmented into three sub-basins with depths of 1.5 to 1.8 km. The basin segments are bounded by extensions of the WNW-striking transfer fault systems observed in the ranges to the east, which cross the valley and coincide with left-steps in the FLVFZ. The sub-basin morphology changes along strike, with a steep western boundary in the south, a steep eastern boundary in the center, and a steep western margin in the north. Vertical offsets for the sub-basins on observed and inferred faults in Fish Lake Valley restored to a pre-extensional datum are 4.0-5.0 km. At the south end of the FLVFZ, formation of a 15 km-wide restraining bend is due to the interaction of a post-7 Ma WNW-striking left-oblique transfer fault system with the FLVFZ, whereas farther north, interaction of younger ~4-6 Ma to recent WNW-striking left-oblique transfer fault systems creates smaller restraining bends along the FLVFZ. Opening of southern Fish Lake Valley records the interaction of the FLVFZ with the kinematically linked, temporally younger to the north, WNW left-oblique transfer fault systems that reduced slip on the FLVFZ by transferring displacement to the east. The geometry and structure of the FLVFZ was modified by the WNW-striking left-oblique transfer faults, initiating the development of left steps at the intersections of the transfer faults and the FLVFZ, which accommodate simultaneous basin formation and displacement transfer.