Paper No. 7
Presentation Time: 10:30 AM


KATOPODY, David, KERSTETTER, Scott, OLDOW, John S. and GEISSMAN, J.W., Department of Geosciences, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080,

The Palmetto Mountain fault zone is part of an active displacement transfer system linking the north-northwest striking, right-oblique Fish Lake Valley fault system in southwest Nevada to right-lateral transcurrent faults in the central Walker Lane. The Palmetto Mountain fault stretches east from the Fish Lake Valley fault for about 60 km and consists of left-oblique, west-northwest striking fault strands that form a belt of structures 2 to 5 km wide. The Palmetto Mountain fault has a cumulative left-lateral displacement of 8 to12 km based on the lateral offset of mid-Paleozoic thrust-faults and Mesozoic granitoids. Displacement on the Palmetto Mountain fault decreases from west to east and is successively transferred northeast via a system of north-northeast striking faults. The north-northeast faults emanate from the eastern half of the Palmetto Mountain fault system and are linked to the west-northwest striking Palmetto Mountain fault zone through curvilinear fault segments. The north-northeast faults are dominated by extensional displacement and control basins filled with late Miocene to Holocene volcanic and sedimentary rocks. A 30 km long segment of the Palmetto Mountain fault exposed along the northern flank of the Palmetto Mountains localized deposition of thick assemblage of mid- to late Miocene andesite and younger tuffaceous sediments and ashflow tuffs. This segment of the fault system records two directions of extension determined by fault-slip inversion. An early history of north-south extension was followed by northwest extension, with the sequential development of extension directions determined by superposed slip-lineations found on both west-northwest and north-northeast striking faults. The timing of the extension-direction reorganization is estimated by the restricted development of north-south slip-directions to volcanic and sedimentary rocks older than 6.0 to 4.0 Ma. Slip-directions associated with northwest extension are found in rocks of all ages and are consistent with contemporary displacements recorded by earthquake focal mechanisms and geodetic velocities.