New high-resolution topographic data and updated tectonic geomorphology at Wheeler Ridge, California

Abstract:

Wheeler Ridge is an eastward propagating and north-vergent fault-bend fold (10km axis, 330m relief) at the front of the Transverse Range thrust system, southern San Joaquin Valley, CA. The occurrence of wind and water gaps along tear faults as well as elevated, distinct geomorphic surfaces along the fold axis show that Wheeler Ridge is actively growing over the kyr-timescale. The soils, tectonic geomorphology, structural modeling, and slip rate estimations were research foci in the 1990’s. Previous studies used total station surveys, contour maps, trenches (5m deep), RASCAL (RAster SCanning Airborne Lidar) scanning (~1pnt/1.54m, ~0.8 km²) on the forelimb, and aerial photographs to map distinct geomorphic surfaces & features, and generate topographic profiles perpendicular and parallel to the fault axis. In September 2014, a ~40 km² area of high resolution (>4pnts/m²) light detection and ranging (lidar) data will be collected at Wheeler Ridge by the National Center for Airborne Laser Mapping (NCALM) via a graduate student Seed grant. The new topographic data will enable us to build on previous studies of meter scale topography on the 10km fold and refine the geometric characterization of identified landforms that have been used to infer uplift, east fault tip propagation, and fold geometry in the last 250 kyr. These features include 5 geomorphic surfaces, stream channel geometry, alluvial terraces on the forelimb as well as wind and water gaps. This initial work will refine the representation of these features with high resolution topography as well as apply additional morphometric techniques to the hillslopes and channels, examine the spatial variation of landforms with independently determined uplift rates, create an updated, detailed geomorphic map of the 10km fold axis of Wheeler Ridge, and use previous subsurface modeling and these new constraints to inform an updated structural model for the growth history of Wheeler Ridge.