Geochemistry of sediments from Quaternary sand ramps in the southeastern Mojave Desert, California
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Trace element analyses of sediment from sand ramps in the Bristol Trough and Clark's Pass aeolian corridors of the Mojave Desert, California were conducted to determine their depositional history and relation to sources of sediment within sand transport corridors. Sand ramps are topographically controlled depositional systems consisting of amalgamated accumulations of aeolian, fluvial and talus deposits. These landforms contain a variety of deposits formed in different environments and arc, therefore, a valuable source of paleoenvironmental information. Sediments were studied from three sand ramps, the Iron Mountain, Big Maria, and Dale Lake sand ramps; and from two sand sheets, Rice Valley and Cactus Plain. Cactus Plain is located on the eastern side of the Colorado River, in Arizona, but previous researchers have suggested that it is related to the corridors of the western (California) side. Geochemical data from units within individual sand ramps indicate that sources for each sand ramp changed through time, probably as sediment availability from different local fluvial/playa systems changed in response to climate fluctuations. Analyses also indicate that each sand ramp is composed of sediment from discrete, local sources. Sand deposits in the Bristol Trough are not integrated, and thus the corridor does not act as a coherent sand transport pathway. Comparisons of sand from Cactus Plain and sediment from the Bristol Trough and Clark's Pass corridors indicates that the Cactus Plain sand, on the east side of the Colorado River was not derived from sources on the west side of the river. 2002 Elsevier Science Ltd and INQUA. All rights reserved.
