Geochronologic and thermochronologic constraints on the Mesozoic to Cenozoic deformation history of southeastern California

Abstract

Southeastern California hosts a complex zone of deformation defined by structures related to the San Andreas fault, such as the sinistral Garlock fault and the largely dextral eastern California shear zone, as well as extensional structures of the Basin and Range province. This study aims to better understand how these tectonic regimes interact in the area around Death Valley. Apatite and zircon (U-Th)/He data from two transects in the Kingston and Mesquite ranges are first used to explore the Cretaceous to Pliocene exhumation history of the footwall of the oldest detachment system associated with the southern Death Valley area, the Kingston Range--Halloran Hills detachment. Apatite (U-Th)/He data were also collected from the Kingston Peak pluton, which has played an integral role in the development of the detachment. A nearby structure, the Southern Death Valley fault, is also investigated. This fault zone extends south through Death Valley and intersects with the Garlock fault, but its extent past this intersection and the displacement accommodated by this structure has been debated. Previous studies suggest that the fault extends south of the Garlock fault and continues to accommodate displacement there. A previous study proposed that Miocene strata in the Avawatz Mountains, located at the intersection of the Garlock and southern Death Valley faults, may be sourced from the Halloran Hills, which are now 20 km to the south, suggesting that the southern Death Valley fault extends that distance and has accommodated at least an equivalent amount of displacement. To test this hypothesis, this study uses detrital zircon U-Pb dating of two formations proposed to have shared provenance to establish depositional ages and sediment sources of the units. The results show that these formations are not related and cannot be used as evidence for a continuation of the southern Death Valley fault. Finally, new zircon (U-Th)/He data and existing thermochronology data constrain the exhumation history of the Avawatz Mountains, which uplift at the intersection of the Garlock and Southern Death Valley fault zones. These data record exhumation related to Mesozoic thrusting and subsequent extensional collapse or erosional exhumation, as well as Miocene uplift. Thermal models support a Middle Miocene initiation date of the Garlock fault zone as well as a Late Miocene initiation date of Southern Death Valley fault zone.