Tectonic Controls on Alluvial Fan Dissection in the El Paso Mountains

The localized dissection of alluvial fans along the western El Paso Mountains is under question. A relatively minor, south dipping normal fault, previously unmentioned in scientific literature, cuts across Quaternary terraces and alluvial fans in the piedmont of the El Paso Mountains. The linear trend of footwall uplift and the pattern of stream incision into the footwall adjacent to the linear trend of footwall uplift reveal that fan dissection is a result of base level fall caused by ongoing tectonism along the El Paso fault system. The regional importance is discussed as the timing of faulting reveals relatively recent uplift of the El Paso Mountains, and a model of extensional strain partitioning is argued for to account for this uplift in the tectonically complex Garlock Fault Zone