NSF Award
1321763
Modern deformation between the North American and Pacific plates is distributed across a wide zone of western North America from the San Andreas fault eastward into the western Basin and Range Province. The eastern Mojave Desert and the region between the Sierra Nevada and Great Basin form a zone of distributed deformation that accommodates about 25 percent of the relative motion between the Pacific and North American plates. Deformation to the south is localized within the Eastern California Shear Zone and to the north in the Walker Lane Belt, which today is characterized by northwest-trending faults with associated earthquake focal mechanisms and GPS velocities that are indicative of transtensional deformation. This project tests the hypothesis that deformation associated with the transtensional system during the early to mid-Miocene was located east of the Sierra Nevada front in the area of the Mono Basin prior to stepping east into the Mina Deflection in the late Miocene. To do so the research team is carrying out a detailed paleomagnetic study of the Oligocene to Pliocene mafic to intermediate lava flows, rhyolitic ignimbrites, sediments in the Mono Basin area (Huntoon Valley, Adobe Hills, Antelope Mountains, Cowtrack Mountains) to determine the spatial and temporal patterns of vertical axis rotation. Field structural studies coupled with 40Ar/39Ar geochronology of volcanic and intrusive rocks are used to constrain the fault geometry, kinematics, magnitude of fault slip, and the timing of deformation.<br/><br/>The Eastern California Shear Zone and Walker Lane Belt, a zone that stretches from the Mojave Desert to northern California/northwestern Nevada, are important fault systems that accommodate a substantial portion of the motion of between the North American and Pacific plates, with most of the motion taken up by the San Andreas fault. However, the tectonic evolution of this complex fault zone remains poorly understood. This project aims to resolve an important part of the puzzle in that it would contribute to a better understanding of how deformation shifts through time. The project has a significant component of student involvement. Improving students' technological and basic science skill-sets will train and foster research endeavors for minority and underrepresented students.
