Doctoral Dissertation Research: A Tectonoclimatic Interpretation of Alluvial-Fan Development in Death Valley, California

9404718多恩冲积扇是由河流沉积和泥石流物质组成的半锥形地貌。冲积扇一般形成在峡谷离开山脉的地方。虽然在其他环境中也可以找到扇子，但它们通常与旱地有关。尽管人们对冲积扇的形成过程给予了相当大的关注，但对于不同环境因素对冲积扇发育的影响方式还没有得到充分的了解。构造和气候力量都被认为起着重要作用，尽管对于哪些是最重要的因素，以及如何识别和区分不同因素的影响，研究还没有定论。这项博士论文研究项目将集中于对加州死亡谷冲积扇上选定地点收集的岩石进行清漆分层的分析。岩石清漆中的层类似于地层沉积物，将通过使用高倍光学显微镜、背向散射电子显微镜和电子探针进行分析，以关联产生清漆的事件的时间并确定其日期。一旦校准，来自这些分析的信息将被用来记录死亡谷的古气候变化，以及将该地区的不同扇子联系起来。将利用Spot和Landsat TM卫星的数据对这一信息进行空间推广。这项研究将做出一些重要的贡献。这将增加对气候和构造因素影响冲积扇发育程度的了解。它将通过建立岩石清漆分层的解释作为对比冲积扇的工具来做出方法论上的贡献。该项目将为死亡谷地区的古气候变化创造一个新的岩石清漆记录，并将产生该地区第四纪冲积扇的地图。作为博士论文改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究事业。

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.