GEOMORPHIC AND STRUCTURAL EVIDENCE FOR SIGNIFICANT NEOTECTONIC CONTRACTIONAL STRAIN WITHIN SOUTHERN DEATH VALLEY AND BORDERING AREAS, EASTERN CALIFORNIA

We present geomorphic, stratigraphic, and structural data indicating that neotectonic (post 4 Ma) deformation in the southern Death Valley (SDV) region includes a significant contractional component associated with major translational strain characteristic of the Eastern California Shear Zone (ECSZ). Neotectonic deformation in the SDV area is dominated by sets of strike-slip faults that complexly intersect with one another. These include three regional strike-slip fault systems (the NW-trending right-lateral southern Death Valley [SDVF] and southern Panamint Valley [SPVF] faults and the EW-trending, left-lateral eastern Garlock fault [EGF]), plus several smaller NE-trending left-lateral faults. The resulting strain field comprises not only large translations along the major strike-slip fault systems, but widespread contraction evidenced in thrust faults and folds as well as areas of downwarping, tilting, and uplift. This deformation affects Quaternary deposits along with older rocks and is a major control on landform development (especially relief and depositional-incision patterns). Specific contractional elements include: (a) blind to emergent thrust faults, commonly associated with superjacent fault-propagation folds; (b) zones of domal warping, folding, and thrusting related to positive flower structures developed on sections of the major strike-slip faults; (c) isolated, asymmetric doubly-plunging folds, many resembling pop-up structures likely related to buried faults; and (d) large-scale, very broad areas of downwarping and uplift that control many depositional basins and highlands in the SDV area (including SDV itself). Most of the small to intermediate-scale contractional features appear to be related to some combination of: (a) transpressive strain along the SDVF, EGF, and SPVF; (b) on- and off-fault deformation near the intersections of two or more large strike-slip faults; and (or) (c) internal deformation of some crustal blocks bounded by intersecting sets of faults. However, the scale of the larger uplifts and downwarps suggest an additional relation to more far-field, regional strain patterns, perhaps related to a NE-directed component of contraction, oriented transverse to this part of the southern ECSZ, evident in recently collected GPS data in the SDV region.