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

地球环境对诸如全球变暖等不断变化的条件的响应建模的不确定性源于对这些环境动力学的了解不足。可以确定的是，在过去的2万年里，撒哈拉经历了剧烈的变化，从比今天更广阔的沙海发展到现在有了常见的湖泊和河流。虽然这些波动与米兰科维奇周期相对应，但我们在过程-反应模型中理解这些波动的基础直到最近才开始出现。撒哈拉地区从阿特拉斯山脉延伸到突尼斯的撒哈拉地台，提供了多种环境的缩影，那里的沉积物被安置在一个下沉的槽中。遥感首先用于绘制当前环境，识别遗迹特征，并为详细的野外工作定位特定的沉积中心。野外工作包括通过实地测绘土壤地貌和地层关系、相分析和地球物理方法，为该地区的风成、河流和湖泊沉积物建立一个不整合边界的地层格架。随后的实验室分析包括序列的年代测定，以便将它们与气候事件联系起来。由于风成和相关沉积体系对气候和其他因素的响应是层序地层学的基础，因此这些结果有望有助于制定一个通用的过程响应风成层序模型，该模型将具有预测外部控制变化的能力。

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.