GEOMETRIC AND GEOMORPHIC CONSTRAINTS ON THE GROWTH OF THE AVAWATZ MOUNTAINS FOOTHILLS, EASTERN CALIFORNIA

The Avawatz Mountains are an actively growing range near the intersection of the Garlock and southern Death Valley Fault Zones in eastern California. This study evaluates the growth of the Avawatz foothills using field relationships, neotectonic geomorphology, and geophysical imaging, with the aim to constrain the style and timing of deformation. The Sheep Creek Thrust marks the active range front bounding the north eastern edge of Avawatz Mountains which are uplifting along a shallow, blind thrust fault. Neotectonic folding is well expressed by Quaternary gravels that overly more complexly deformed Proterozoic metasedimentary and igneous rocks with complex tectonic histories. Fold geometries are constrained using ground-based photogrammetric modeling of gravel beds to quantify bedding geometries. This approach provides a safe and robust means of measuring precise attitudes in gravel beds, which are difficult to measure in the field. Quaternary deformation is also expressed in warping of older geomorphic surfaces which were enumerated by high-resolution topographic surveying using small unmanned aerial vehicles (sUAS) and photogrammetric modeling of acquired aerial photos. Preliminary ages of geomorphic surfaces are estimated using rebound-hammer measurements calibrated in the nearby Noble Hills. The final component of this project involves a shallow seismic reflection profile approximately 800 meters long to determine the subsurface location of the fault tip. Amalgamating the field associations, geomorphic evidence, and geophysical imaging will assist in determining the nature of progression of the blind thrust along the Avawatz front. Constraining the timing and development of this active thrust on a smaller scale will further contribute insight into the structural evolution of considerably larger, complex thrust fault systems, as well as contribute the regional earthquake hazard.