Response of Eolian and Associated Depositional Systems to Climate and Dynamic External Factors-Toward an Eolian Sequence Stratigraphic Model

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Uncertainty in modeling the response of Eath environments to changing conditions such as global warming arises from a poor understanding of the dynamics of these environments. It is established that over the past 20,000 years the Sahara has undergone dramatic swings from more extensive and sand-sea devlopment than today to being vegetated with common lakes and rivers. While these swings correspond to Milankovitch cycles, our basis for understanding these in a process-reponse model has only recently begun to emerge. The area of the Sahara extending from the Atlas Mountains onto the Sahara Platform in Tunisia offers a microcosm of diverse environments, where deposits are housed in a subsiding trough. Remote sensing is first used to map present environments, recognize relict features, and locate specific depocenters for detailed field work. Field work involves the establishment of an unconformity-bounded stratigraphic framework for eolian, fluvial and lacustrine deposits in the area through field mapping of soil-geomorphic and stratigraphic relationships, facies analysis, and geophysical methods. Subsequent lab analysis involves the dating of the sequences so they can be correlated with climatic events. Because the response of eolian and associated depositional systems to climatic and other factors is the basis for sequence stratigraphy, the results are expected to help formulate a general process-response eolian sequence model that will have predictive capabilities with respect to changing external controls.