Late Miocene Strain Transfer and Core-Complex Formation in the Silver Peak-Lone Mountain Extensional Complex in the Central Walker Lane, Nevada
University of Kansas, Department of Geology Lawrence, KS
In the late Miocene, strike-slip displacement in the northern part of the Eastern California Shear Zone (ECSZ) was concentrated on the Furnace Creek fault system and was coeval with displacement on northwest-trending transcurrent faults in the Central Walker Lane (CWL). Displacement transfer from the ECSZ to the CWL was localized within the Silver Peak-Lone Mountain (SPLM) extensional complex, which stretches 85 km northeast from the northern end of the Furnace Creek fault. The central SPLM consists of a series of northwest-trending turtleback structures exposing lower-plate amphibolite-facies metamorphic tectonites that are separated from structurally overlying non-metamorphic upper plate rocks by a folded detachment fault in the Silver Peak Range, Weepah Hills, and Lone Mountain. Systematic apatite and zircon (U-Th)/He thermochronometry was undertaken to investigate the timing of onset and slip rates along this detachment fault. Samples were collected from the lower-plate of the SPLM along horizontal transects sub-parallel to slip direction. These new zircon and apatite (U-Th)/He age data generally decrease in slip direction and indicate an onset of rapid fault slip and footwall exhumation at ~7-8 Ma. The timing of deformation in the SPLM transfer zone appears to be in good agreement with the initiation of motion along the Furnace Creek fault and the notion that deformation in parts of the central Walker Lane changed from east-west extension to right-lateral strike-slip displacement at ~8 Ma; at a time corresponding to a change in relative motion between the Pacific and North American plates.
AAPG Search and Discovery Article #90070 © 2007 AAPG Foundation Grants in Aid