BRISTOL MOUNTAINS WILDERNESS/SOUTH BRISTOL MOUNTAINS FAULT ZONE GEOLOGIC MAP

The South Bristol Mountains(SBM) and the Bristol Mountains Wilderness Area are located within the central Mojave Desert between the eastern California shear zone(ECSZ) and the Colorado River extensional corridor, near the eastern limit of active seismicity within the ECSZ, and within the zone of Neogene to Quaternary deformation (~23 Ma to present) that has accommodated relative motion between the Pacific plate and the North American plate during the onset of strike slip plate boundary motion. The magnitude and timing of Neogene deformation within the SBM has not been studied in detail. The SBM display a prominent NW-SE trend imposed in part by multiple strands of the South Bristol Mountains fault zone (SBMFZ). The accumulated slip along the SBMFZ is presently poorly constrained by the use of plutonic offset markers. Previous workers within the SBM have not subdivided the Neogene strata, nor documented in detail the complex fault zone (Kupfer, 1962; Bishop, 1963; Dibblee, 2008; Howard and Miller, 1992; Miller et al, 1993). The Mesozoic plutonic rocks have been mapped in more detail (Fox and Miller, 1990; Miller and Howard, 1994; unpublished mapping by Dave Miller). Identifying piercing points in the bedded strata across the SBMFZ would produce a higher-confidence determination for total accumulated plate boundary shear accounted for by the SBMFZ. Detailed geologic mapping of the bedded volcanic and sedimentary rock units within the south Bristol Mountains is necessary to identify such markers. Here we present a compilation of the prior basement mapping and new detailed mapping of the Miocene volcanic strata.