GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 385-22
Presentation Time: 9:00 AM-6:30 PM

ACTIVE DISPLACEMENT TRANSFER BETWEEN THE HUNTER MOUNTAIN – SALINE VALLEY FAULT SYSTEM AND THE FURNACE CREEK – FISH LAKE VALLEY FAULT SYSTEM VIA THE EUREKA VALLEY PULL-APART BASIN, EASTERN CALIFORNIA


LANDRENEAU, Lauren, SOKOL, Sarah, OLDOW, John S. and MUELLER, Nicholas J., Department of Geosciences, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080, lal140330@utdallas.edu

The northern Eastern California Shear Zone is bounded on the east by the northwest-trending Furnace Creek – Fish Lake Valley (FC-FLV) fault system that has accommodated ~23-28 km of right-lateral motion since ~4 Ma. The FC-FLV fault system is distorted by an 8-10 km left-step formed by the Cucomungo Canyon Restraining Bend, a marked 1.2 km topographic high flanked to the west by the north-northwest trending Eureka Valley. The Hunter Mountain – Saline Valley (HM-SV) fault system lies ~45 km to the southwest of the FC-FLV fault system and accommodated ~10 km of right-lateral displacement since 4 Ma. The HM-SV and FC-FLV fault systems are linked by north-northeast trending structures that pass displacement through Eureka Valley. On the west, Eureka Valley is bounded by north-northeast striking faults and to the east by north-south to north-northwest trending faults. To assess the subsurface geometry of Eureka Valley, we collected 529 gravity stations at a spacing of 300m along several transects using two Scintrex CG-5 gravimeters with Leica GNSS receivers providing positioning of 2.5 cm or better. The gravity data were merged with 40 existing measurements and, using a reference density of 2.67 g/cm3, reduced to a complete Bouguer anomaly. A residual complete Bouguer anomaly was computed and inverted for depth in three dimensions using Geosoft Oasis Montaj GYM-SYS 3D software. Eureka Valley is underlain by two gravity lows of -18 mGal in the north separated from a -14 mGal low in the south by a northeast trending high of –7 mGal; with corresponding basin depths of ~1.7, 1.1, and 0.6 km, respectively. The northern basin deep coincides with major fault trends and reflects a transition from northeast to north-northwest strike as the northern segment of the FC-FLV fault is approached from the west. The southern sub-basin marks the same change in trajectory but is not directly linked to the FC-FLV fault system and is connected through a 10 km wide belt of north-northeast faults. Estimated minimum vertical displacements of ~2.6 km and ~2.2 km were determined by restoring basement depths to a pre-extensional datum. Using the regional extension direction of N65W and a fault dip of 60°, we calculated an aggregate horizontal extension of ~2.85 km across Eureka Valley. With extension starting after 4 Ma, the average displacement rate is 0.7 mm/yr.