OFF-FAULT DEFORMATION, UPLIFT AND SEDIMENTATION IN PILOT KNOB VALLEY, CALIFORNIA -- PIECING TOGETHER COMPLEX STRUCTURAL AND KINEMATIC PROCESSES BETWEEN THE GARLOCK FAULT AND PANAMINT VALLEY FAULT

The intersection of the dextral (2-3 mm/yr) Panamint Valley fault (PVF) with the sinistral (5-15 mm/yr) Garlock fault (GF) in eastern Pilot Knob Valley (PKV) controls the active off-fault tectonic deformation in the southern Slate Range (SSR) and northern PKV. We suggest here that rapid uplift of the Pleistocene Christmas Canyon Formation (CCF) and overlying fanglomerates, from a base (valley floor) elevation of 670 m, to a peak of 1100 m (adjacent to the SSR), accommodates decreased slip on the southern PVF near the GF. We present preliminary data that constrain exhumation and rock uplift in the SSR and northern PKV over Quaternary time: (1) new Be-10 cosmogenic and soil development data from offset geomorphic surfaces, (2) sedimentological data from the CCF, and (3) pending thermochronometric data for the SSR.

The structural makeup of the study area includes three blocks, from north to south: (1) SSR cored by Mesozoic metamorphic rocks, (2) uplifted and northerly tilted Pleistocene and Holocene sediments between the SSR and GF, and (3) buried (flat-lying?) late Neogene sediments south of the GF in PKV. Sedimentological evidence for an evolving strain field includes three provenance facies within the CCF: (1) a basal, distal fanglomerate with Eagle Crags-derived volcanic clasts; (2) a medial, inter-basinal lacustrine facies; and (3) an upper, SSR-derived sandstone and conglomerate. During CCF deposition, the topographic low within PKV migrated progressively southward from its formal position adjacent to the SSR. Finally, a 50 ± 13 ka Be-10 cosmogenic profile age for a 15-m-high terrace tread adjacent to the GF suggests a minimum throw rate of ~0.3 ± 0.08 during the late Pleistocene.

A three-stage model is invoked to explain the present structural and sedimentological configuration here: (1) an early Pleistocene period of minimal uplift of the SSR, with the topographic low of PKV north of the present GF; (2) a middle Pleistocene period of moderate uplift of the SSR and CCF north of the GF, to explain the influx of SSR-derived sediments above the lacustrine CCF facies; and (3) rapid uplift of the SSR, and basin inversion of the CCF and capping fanglomerates during last 200-300 ky. We attribute the change in structural and kinematic style to recent strain accommodation at the southern terminus of the PVF on the GF in eastern PKV.