Documenting Thrust‐Related Exhumation of the Avawatz Mountains, Southern California: Implications for the Kinematic History of the Eastern Terminus of the Garlock Fault

Abstract The left‐slip Garlock fault, southern California, is oblique to the right‐lateral Pacific‐North American plate boundaries, and its role in accommodating plate motion remains unresolved. The timing and kinematics of deformation within the Avawatz Mountains, located at the eastern tip of the Garlock fault, can help evaluate competing Garlock fault models. In this region, the east‐striking Garlock fault intersects the northwest‐striking right‐slip Southern Death Valley fault (SDVF). The Avawatz Mountains were constructed via late Cenozoic contractional deformation involving active thrust and/or oblique‐slip faults. Contrasting structural models suggest the Avawatz Mountains formed as a fault‐termination thrust belt at the eastern tip of the Garlock fault or as a transpressional restraining bend along the SDVF. We conducted geologic mapping, structural analysis, and low‐temperature thermochronology to test these models. Field observations show numerous subvertical west‐striking strike‐slip faults in the western portion of the range and a prominent west‐dipping reverse fault along the eastern rangefront. New zircon (U‐Th)/He thermochronology (ZHe) from a ∼1 km vertical transect in the hanging wall of a major east‐directed thrust suggests that exhumation initiated ca. 15 Ma. Based on the observed dip of the west‐dipping thrust, exhumation rates imply east‐directed horizontal shortening rates of 0.4–0.9 mm/yr across the Avawatz Mountains since the mid‐Miocene. These results are consistent with exhumation initiating in the middle Miocene (ca. 20–15 Ma), synchronous with the initiation of slip on the Garlock fault as a clockwise rotating bookshelf fault. The Avawatz Mountains reflect strain transfer from the left‐lateral Garlock fault to an east‐directed termination thrust system.