TIMING CONSTRAINTS ON CENOZOIC FAULTING BASED ON NEW GEOCHRONOLOGICAL DATA IN EASTERN QUEEN VALLEY, NEVADA

The Queen Valley pull-apart structure is one of several extensional structures characteristic of the central portion of the Walker Lane Belt, known as the Mina Deflection. These pull-apart structures are tectonically controlled by NE-trending normal faults that transfer slip from the southern to the northern Walker Lane belt. The Queen Valley fault zone consists of NE-trending normal faults which are responsible for the pull-apart basin located at the northern termination of the right-lateral Owens Valley/White Mountains fault system. Previous structural and thermochronological studies have documented the inception of extensional faulting in the Queen Valley pull-apart basin at ~3 Ma. This study presents new detailed mapping, geochronological and geochemical data investigating the kinematic, temporal, and spatial relationship between Cenozoic volcanism and complex faulting in eastern Queen Valley. A well-preserved volcanic stratigraphy, including Oligocene ash-flow tuffs (~26 Ma), Miocene andesites (~13 Ma), and Pliocene basalts and rhyolites (~2-4 Ma), allows us to constrain the timing of Cenozoic fault activity on individual fault strands. The northern margin of Queen Valley is characterized by an ENE-trending strike-slip fault zone with ~1.2 km of left-lateral displacement based on offset ~3 Ma basalt. Toward the east, several of these faults merge with the left-lateral Coaldale fault in the Montgomery Pass area transferring strain eastward out of Queen Valley. Along the southeastern margin of the pull-apart structure, the main strand of the Queen Valley normal fault undergoes a transition from a NE-SW to a N-S trend while continuing to transfer displacement eastward into the footwall block along several ENE-trending normal faults. These top-down-to-the-NW relay faults offset Oligocene rhyolite (~26 Ma) and Miocene andesite (~13 Ma) and juxtapose them against Jurassic granodiorite. Locally these structures appear to reactive pre-existing Oligocene normal faults and are capped by late Pliocene rhyolitic ash-flow tuffs. Ongoing (U-Th)/He and Ar⁴⁰/Ar³⁹ dating will further constrain the stratigraphy of the abundant volcanic units in the area and continue to allow us to reconstruct multiple stages of faulting and magmatism in the field area.