During Neogene extension in the southwest US extensive systems of detachment faults have developed. During crustal thinning and extension sedimentary basins formed and were filled above the mobile and detached fault blocks. The strata in these basins have the potential to reveal many of the details of the dynamic evolution of these extending terranes. This study will examine a well-exposed example-the shadow valley basin in southern California that developed above the Halloran Hills detachment complex. The objectives are to characterize the deposition of these sediments and sources active during basin filling, to develop models of interactions between faulting, uplift and extension, tectonic and erosional patterns and character within the supra-detachment basins. Results are expected to provide insights into the rates and processes associated with the development of detachment systems.
