Late Quaternary aeolian geomorphology, east-central Mojave Desert, California

Geomorphological and sedimentological methods, including scanning electron microscopy (SEM), contribute towards an understanding of the nature and frequency of late Quaternary aeolian activity in the east-central Mojave Desert, California. In particular, quartz surface microfeatures of aeolian sediments of various ages reveal the relative importance of mechanical and chemical weathering processes during and since deposition. Such evidence provides a basis for relative dating of the aeolian sequence, and for evaluating the environmental conditions under which grains accumulated and weathered. The Cronese Basin, the Kelso Dunes and the Dale Lake Sand Sheet provide the principal field localities, with additional evidence from the Cowhole, Kelso and Calumet Mountains.; Geomorphic, granulometric and soil-stratigraphic analyses indicate a maximum of 8 aeolian episodes during later Quaternary time whereas scanning electron microscopy of grain characteristics suggests 6 episodes. It is probable that 4 or 5 aeolian episodes have occurred since the latest Wisconsinan glacial maximum at about 18 ka, with peak deposition in earlier Holocene time followed by cessation of aeolian activity and the formation of rock varnish around 5 ka. Some deposits could represent pulses of dune deposition during a single major aeolian episode. Most aeolian landforms in the east-central Mojave Desert occur as stabilized fossil sand sheets and contain significant paleosols and other weathering horizons.; Paleoclimatic reconstruction from field evidence and atmospheric general circulation models indicate that the various aeolian episodes recurred primarily in response to climatic fluctuations which generated stronger and more persistent winds, for example during the Pleistocene-Holocene climatic transition, and to the lowering of lake basins and a consequent increase in fine sediment availability.; Analysis of the quartz surface textures indicates that mechanical and chemical weathering processes, such as silica precipitation, dust infiltration, edge abrasion, salt weathering, carbonate influx, and hematite plastering, play a significant role in the post-depositional modification of aeolian sediments. Such evidence permits paleoenvironmental reconstruction during and since deposition.