Dextral slip on the Sheephead Fault during late Miocene extension, Southeastern California

Abstract

The Sheephead Fault Zone (SFZ) is exposed at Sheephead Pass and bounds the China Ranch Basin (CRB) to the north, and its role in accommodating late Miocene northwest-directed extension within the Death Valley region has been unclear. New sedimentological studies of fanglomerate stratigraphy along the northern margin of the CRB and other field relations show that 20 km of right-lateral translation occurred on the SFZ. Two new 40Ar/39Ar ages for tuffs within the fanglomerate show that displacement initiated prior to 11.12 Ma and was coincident with the opening of the CRB. Provenance studies of northern sourced fanglomerates combined with new age constraints yield a minimum slip rate of 4 mm/yr on the SFZ between 12.4 – 8.9 Ma. Results also show that rapid exhumation of the Kingston Peak granitic pluton occurred earlier than previously recognized, and was also coincident with the opening of the CRB, with an estimated uplift rate of 3.0 – 3.2 mm/yr. Right-lateral slip on the SFZ is viewed as translational, and it accommodated plate boundary dextral shear distributed across the Death Valley region.