9404718 DORN Alluvial fans are semi-conical landforms comprised of stream deposits and debris-flow materials. Alluvial fans generally form where canyons exit mountain ranges. Although fans may be found in other environments, they usually are associated with drylands. Although considerable attention has focused on the processes that produce alluvial fans, full understanding has not yet been achieved regarding the ways that different environmental factors influence their development. Both tectonic and climatic forces have been identified as playing important roles, although research has been inconclusive regarding which are the most important factors, how the influences of different factors can be identified and distinguished from each other. This doctoral dissertation research project will focus on analyses of varnish layering from rocks gathered in selected sites on alluvial fans in Death Valley, California. The layers in rock varnish, which are analogous to stratigraphic deposits, will be analyzed through the use of high-powered light microscopes, back-scatter electron microscopes, and electron microprobes in order to correlate and date the timing of events producing the varnishes. Once calibrated, information from these analyses will be used to record paleoclimate changes in Death Valley as well as to associate different fans in the area. Spatial generalization of this information will be undertaken using data from the SPOT and Landsat TM satellites. This research will make a number of important contributions. It will add to knowledge of the degree to which climatic and tectonic factors affect alluvial fan development. It will make methodological contributions by establishing interpretation of rock-varnish layering as a tool for correlating alluvial fans. The project will yield a new rock-varnish record of paleoclimatic changes for the Death Valley region, and it will result in a map of Quaternary alluvial fans in the region. As a doctoral d issertation improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.
