NEW SURFICIAL GEOLOGIC MAP OF THE OWLSHEAD MOUNTAINS 30' X 60' QUADRANGLE IN THE SOUTHERN DEATH VALLEY AREA, EASTERN CALIFORNIA, USA

A new surficial geologic map for the Owlshead Mountains 30’ x 60’ Quadrangle has been compiled from both new and existing geologic mapping. The map highlights spatial patterns of Quaternary sedimentation, erosion, and active deformation affecting landscape evolution in the area, and represents the first detailed synthesis of physiographic, geologic, and tectonic elements in the transition region of southern Death Valley (SDV) and environs. Key elements of the map are a complex suite of (a) aggradational single and composite surficial units classified by both geologic age and genetic process (e.g., alluvial- and debris-flow fan, wash, axial valley, eolian, playa, lacustrine, groundwater discharge, and mass-wasting deposits,) and (b) degradational units (pediment surfaces). The surficial units overlie a generalized set of pre-Quaternary map units recognized for their potential relevance to physical and genetic attributes of the Quaternary deposits. The map also identifies an array of faults and folds, including several fault-related folds, that are differentiated by geometry and (or) slip type.

Map compilation emphasized the systematic depiction of surficial units and structures essential to time-space interpretations of deposition and dissection, surface-drainage evolution, and neotectonic deformation across this region. The mapped distribution and age of alluvial and fluvial deposits clearly define spatial and temporal patterns of deposition, mainly concentrated in the central trough of SDV, that contrast with areas in adjoining highlands where drainage incision is persistent. These data provide input to time-space reconstructions of regional drainage such as the lower Amargosa River. Mapped traces of faults and folds define complex and widespread neotectonic deformation centered in SDV and areas to the south and west. Active deformation is characterized by: (a) three to four regional sets of commonly intersecting dextral and sinistral translational faults (including the SDV and eastern Garlock faults); (b) zones of contraction (thrust faults and associated folds, transpressive structures, and fold belts) and uplift commonly concentrated at major fault intersections, and (c) zones of downwarping and uplift that form many of the basinal troughs (e.g. SDV) and adjoining highlands.