Collaborative Research: Deformation Rates and Kinematics of Ancient and Active Displacement Transfer, Central Walker Lane, Western Great Basin Grant uri icon

Overview

abstract

  • Late Cenozoic deformation is broadly distributed across the North American plate margin of the conterminous western United States and stretches from the San Andreas fault system eastward across the Mojave Desert and into the Basin and Range. The eastern California shear zone and Walker Lane of the western Great Basin form an active belt of structures accommodating about 25% of the relative motion between North America and the Pacific plate.
    From the Mojave Desert, the displacement is carried north, east of the southern Sierra Nevada, in a narrow zone of deformation bound on the west and east by the Owens Valley and Furnace Creek fault systems. North from the latitude of the central Sierra Nevada, the zone of deformation broadens to include the Walker Lane and central Nevada seismic belt in the northwestern Great Basin. The Sierra Nevada behaves as a coherent tectonic block with a northwest-directed motion of 10-14 mm/yr and forms the western boundary of the zone of distributed deformation in the Great Basin. A complex pattern of active structures underlies west-central Nevada where displacement is transferred from the eastern California shear zone to the Walker Lane and the central Nevada seismic belt. Integrated geologic, seismological, and GPS geodetic results indicate that the central Walker Lane (CWL) serves as an displacement transfer system linking stepped northwest-trending transcurrent faults. The displacement transfer system evolved over a period of ~13 Ma and carried at least 50 km right-lateral motion from the Furnace Creek fault system of eastern California to the right-lateral faults of the CWL. Ancient displacement transfer was accompanied by exhumation of mid-crustal rocks in the extensional stepover between transcurrent structures and was accompanied by vertical axis rotation and tilt of both upper- and lower-plate assemblages. The transfer system is still active and underlies a region 50 by 120 km immediately northwest of the ancient structures. Based on existing work, the comparison of a geodetically determined velocity field for the CWL is not easily reconciled with the current understanding of fault displacements in the region and points out the difficulty in comparing geodetic and geologic displacement fields. Furthermore, the continued activity of the displacement transfer system since inception at ~13 Ma offers presents the opportunity to assess ancient and active rates of deformation using geologic and geodetic techniques.
    The PI's propose an integrated geodetic and geologic investigation of the central Walker Lane to address two questions: (1) What is the three-dimensional geometry and displacement history of extensional transfer developed within a transcurrent fault system stepover?, and (2) Are displacement rate and kinematic estimates comparable between geodetic, seismological, and geologic investigation of ancient and active structures within the transfer system? The central Walker Lane is ideally suited for this study for several reasons: (1) the region is seismically active and well defined earthquake focal mechanisms exist for the displacement transfer fault system, (2) the faults are well exposed and have produced preliminary fault-slip estimates of deformation kinematics, (3) a complex present-day displacement field with ~10 mm/yr of differential slip is recorded by a GPS geodetic network, (4) the geologic evolution of the displacement transfer system is preserved in the exhumation history of well-exposed extensional turtleback structures, (5) synorogenic volcanic and sedimentary rocks in the upper-plate assemblage of the extensional complex record a history of progressive tilt associated with fault displacement, (6) regionally extensive domains of differential tilt and vertical axis rotation associated with displacement transfer are recognized in preliminary paleomagnetic investigation, and (7) regional geologic compilation of the region is mature and provides excellent control for displacement-history reconstruction. These elements will allow characterization of the kinematics of displacement transfer and offer the opportunity to directly compare deformation kinematics and rates over geologic and geodetic time intervals. The PI's will address the tasks listed above with an integrated study utilizing detailed geologic mapping, structural analysis, GPS geodesy, paleomagnetic analysis, geochronology, and thermobarometric investigation. The research team (Oldow, Geissman, McClelland, McIntosh, and Selverstone) have the expertise to address the various research topics and two of the researchers (Oldow and Geissman) have substantial experience working in the area. By building on previous studies, this integrated investigation will establish the areal limits of the transtensional fault system, document variable geometric relations between major and secondary fault systems, define the kinematic history of fault block motion, and develop first-order estimates of recent and ancient displacement.

date/time interval

  • June 15, 2002 - May 31, 2006

total award amount

  • 180,611

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