PLEISTOCENE DEXTRAL FAULT SLIP ALONG THE WHITE MOUNTAINS FAULT ZONE, CALIFORNIA

Geologic and geodetic studies show that dextral shear within the Eastern California Shear Zone accounts for 20-25% of the relative plate motion between the Pacific and North America plates. A significant component of this dextral shear is accommodated along the Owens Valley-White Mountains fault system. A published kinematic model for the Eastern California Shear Zone suggests that 1.4-4.1 mm/yr of Owens Valley fault slip continues northward along the White Mountains fault zone. New geologic mapping, geomorphic, and geochronologic investigations along the White Mountains fault zone shed light on its Quaternary dextral fault slip history and allow us to test this kinematic model. Drainages, shutter ridges, and ridgelines show dextral offsets that range from ~5 to 559 ± 7 meters. Beryllium-10 cosmogenic radionuclide dating methods used on in situ boulders demonstrate that the age of the oldest fan surface is 225 ± 25 ka. Minimum offset of drainages developed within the oldest fan surface is 559 ± 7 meters, yielding a minimum late Pleistocene slip rate of 2.5 ± 0.3 mm/yr. Our new data refine a kinematic model proposed for the recent evolution of dextral fault slip in the Eastern California Shear Zone.