PLIOCENE TO CONTEMPORARY DISPLACEMENT TRANSFER AND THE SOUTH TO NORTH DECREASE IN SLIP RATES ALONG THE FURNACE CREEK – FISH LAKE VALLEY FAULT SYSTEM, WESTERN GREAT BASIN

The northwest-striking Furnace Creek – Fish Lake Valley fault zone (FC-FLVFZ) stretches for >250 km from southeastern California to western Nevada, forms the eastern boundary of the northern segment of the Eastern California Shear Zone, and has Miocene to contemporary displacement. The FC-FLVFZ shows a south to north decrease in aggregate displacement from a maximum of 75-100 km to 40-50 km in southern Fish Lake Valley (FLV). Dextral offset of 28 ± 1 km is accommodated on FLV segment of the FC-FLVFZ prior to a major kinematic reorganization at ~3.7 Ma with an additional 17 ± 6 km accumulated after ~3.7 Ma. This estimate compares favorably to a 6.1 +1.3/-1.0 mm/yr slip-rate along the southern FLV fault, extrapolated over 3.7 Ma. Along the FLV fault, slip-rates determined from offset geomorphic features dated from 6 to 94 ka have a stepwise south to north decrease that coincides with intersections of the FLV fault with two major west-northwest striking faults, the Palmetto Mountain (PMF) and Sylvania Mountain (SMF) faults. The PMF and SMF stretch east for 60 km where they are kinematically linked to north-northeast striking extensional faults bounding deep basins and ultimately merge into north-northwest structures forming the eastern boundary of the southern Walker Lane. Across intersections with the SMF, and PMF, respectively, rates along the FLV fault decrease from 6.1 +1.3/-1.0 mm/yr to 3.1 +0.5/-0.4, and from 3.1 +0.5/-0.4 to 2.5 +0.4/-0.3 mm/yr. Based on the history of displacement on basin-bounding faults kinematically linked to the PMF, 5-10 km of transcurrent offset occurred after ~3.7 Ma, consistent with a rate decrease of 1.3-2.7 mm/yr on the FLV fault. No incremental timing constraints exist for the SMF, but the cumulative displacement of 24 ± 1 km occurred on the fault after 7.6-8.5 Ma and readily accounts for the slip-rate decrease along the southern FLV fault. Based on the compatibility of late Quaternary to Holocene slip-rates and post-Pliocene cumulate offset on the FLV fault, we estimate that the SMF accounts for 5-17 km (slip-rates of 1.4-4.7 mm/yr) of displacement decrease along the FLV fault over ~3.7 Ma. Our results indicate that 10-27 km of Pliocene to Holocene displacement on the northern FC-FLVFZ is transferred east to north-northeast striking extensional faults and thence to the central Walker Lane.