Aeolian abrasion is an important erosional process in arid regions, but abrasion rates on crystalline bedrock are not well quantified beyond instrumental timescales. This is partly because few measurements can reconstruct this erosional history. Recent developments in optically stimulated luminescence (OSL) and cosmogenic radionuclide measurements (CRN), however, offer two independent and complementary methods for determining hard rock erosion rates on timescales of decades to millennia. In this study, our team has collected rock samples from across the surfaces of ten boulder-sized ventifacts, located at two field sites in the deserts of southern California: Silver Lake, north of Baker, and Garnet Hill, north of Palm Springs. OSL samples, which are sensitive to centimeter-scale erosion, were collected inside and outside of erosional features (e.g., flutes, scallops) and along the broad surfaces of abrading and nonabrading boulder faces. CRN samples, which are sensitive to decimeter-scale erosion, were collected from the abrading faces. We have also estimated modern rock hardness values across these ventifacts and used stereophotogrammetry to develop 3-D models of rock morphology. Initial results are consistent with the hypothesis that ventifact erosion rates in southern California peaked in the early Holocene and have decreased substantially until present. Finally, I discuss the promise and limitations of this new way of understanding ventifact erosion.
