Neotectonics and Structural Development of the Northern Walker Lane

Abstract:

The Walker Lane is a major element of the San Andreas fault system and by itself one of the most accessible and well-known intraplate shear zones in the world. This northwest trending zone of discontinuous active faults and disrupted topography that sits between the Sierra Nevada on the west and the north-northeast trending faults and ranges of the Great Basin to the east is associated with a geodetically well-defined zone of northwest-directed right-lateral shear ranging from ~ 5 to 10 mm/yr. It is the northern section of the Walker lane that includes the Lake Tahoe, Carson, Smith, Mason, Antelope, Bridgeport and Walker Lake basins and Carson and Wabuska structural lineaments that is currently the focus of our investigation. Here, right-lateral shear strain of at least 20-30 km has resulted in the development of this set of roughly en echelon normal fault basins in the absence of any major northwest-directed strike-slip faults. Synthesis of available geologic and geodetic data also shows that geodetic deformation is outpacing the late Quaternary slip rate on active faults across the region. The observations may be explained as the result of inadequate geologic fault slip rate data, by the accommodation of slip by vertical-axis block rotations, or some measure of both. The research presented here describes our initial efforts and findings resulting from collection and analysis of Lidar for evidence of strike-slip along the major structures of the region, the application of cosmogenic, optically stimulated luminescence (OSL) and radiocarbon dating to identified offset surfaces to better quantify the rate at which faults are slipping in the region, and the collection of gravity and paleomagnetic observations to clarify both the current and long-term structural development of the basins and intervening fault blocks.