LATE NEOGENE SLIP TRANSFER AND EXTENSION WITHIN THE CURVED WHISKY FLAT FAULT SYSTEM, CENTRAL WALKER LANE, WEST-CENTRAL NEVADA

The central Walker Lane fault system is characterized by a system of northwest-striking, right-lateral transcurrent faults that, in the Mina deflection of west-central Nevada, abruptly swing to the west-southwest where the faults merge with north-northwest trending structures of the northern Eastern California Shear Zone. The Whisky Flats fault system (WFFS) forms the apex of curved array of faults that bounds an extensional basin (Whisky Flat) separating the southern Wassuk Range on the west from the Garfield Hills and Excelsior Mountains to the east. Extensional deformation in the WFFS began at ~3 Ma based on (U-Th)/He thermochronology of footwall rocks exposed along the eastern flank of the Wassuk Range. Gravity stations with 300 m spacing along transects normal and parallel to the axis of the basin were measured using two Scintrex CG5 gravimeters and located with a vertical control of 2.0 cm or better achieved by using Leica dual frequency GNSS receivers. A residual complete Bouguer anomaly using a density of 2.67 g/cm² was inverted in 3D for depth using GMSYS modeling software and provides a maximum depth estimate for the extensional basin of ~1.2 km. The deepest part of the basin stretches east-west across the center of the valley and depths progressively decrease the north and south. The basin is bounded on all sides by exposed bedrock and has a prismatic geometry consistent with the curved array of faults that constitute the WFFS. The faults of the WFFS change strike, progressively from north to south, through nearly 110° and have right-oblique, dip-slip, and left-oblique displacement around the curvature. Fault-slip inversion records two directions of contemporaneous extension indicative of nonplane strain conditions during deformation. The primary extension direction of N65°W is responsible for the large-scale structures, including opening of the Whisky Flat basin. Secondary extension is oriented N20°E and typically forms relatively small displacement features that accommodate finite flattening. The nonplane deformation is attributed to the curvature of the faults in the WFFS.