SAND RAMPS AND LATE QUATERNARY AEOLIAN DYNAMICS, MOJAVE DESERT, CALIFORNIA, USA

Sand ramps provide valuable information on the nature and dynamics of late Quaternary aeolian accumulation, stabilization and reworking in the Mojave Desert, California. Sand ramps consist primarily of aeolian sediments, intermingled with significant contributions from nearby fluvial and mass movement (colluvial) deposits, and are typically found on the western (windward) slopes of mountain ranges that lie astride well-developed aeolian sand transport corridors that extend from source areas in the western and central Mojave Desert toward depositional sinks that lie to the east and south.

These topographically controlled sand accumulations appear to be relict and show no evidence of present day aeolian activity. Most of the sand ramps contain multiple aeolian depositional units, separated by paleosols formed during periods of geomorphic stability. Based on geomorphic, stratigraphic, and paleosol analysis, as well as luminescence ages, aeolian deposition appears to have been rather discontinuous or in discrete pulses and occurred throughout the late Quaternary, with significant emplacements between 35-25 and 15-10 ka.

Aeolian constructional episodes seem to be driven primarily by climatically-driven variations in sediment supply from fluvial and/or lacustrine sources. Significant changes or fluctuations in the regional climate may impact aeolian sediment transport systems via changes in sediment supply, availability and mobility. Trace element geochemistry of sediment from sand ramps indicate that sources for each sand ramp changed through time, possibly as sediment availability from different local fluvial/playa systems changed in response to climatic oscillations.