Deciphering the Interconnected Roles of Climate and Tectonics in Reconstructing the Early Evolution of a Rifted Continental Margin

摘要[9909308]陆缘从早期的构造和火山活动演化到成熟后的被动阶段。这些地质事件发生在当地和全球气候条件的背景下，这些气候条件可能与大陆向不同纬度漂移有关。因此，构造和气候都可能对裂谷作用产生的沉积物的组成产生重大影响。在这方面，在大陆分裂期间和之后沉积的硅屑沉积岩的组成不仅记录了烃源岩组成和相对于裂谷两侧的位置的演变，而且记录了分离期间的主要气候条件。拟议的调查努力严格检查美国西南部新元古代和寒武纪的硅质碎屑岩，这些岩石是在Rodinia分裂期间和之后沉积的。一个目标是确定构造和气候在形成沉积物组成方面的相对重要性。这些信息，再加上现有的沉积学和地层学数据，将被用来建立一个全面的数据库，用来破译这个裂谷大陆边缘的早期地质历史，它的演变仍然存在很大的争议。本研究收集的数据主要是岩石学、地球化学和同位素，目的是通过考虑化学风化和成岩过程，跟踪从烃源岩向沉积物转移的矿物和元素丰度。研究还将侧重于确定整个岩石和碎屑长石的同位素组成（Sm-Nd, Pb/Pb），以及单晶锆石U-Pb分析，作为确定特定烃源岩和位置的机制，以及它们随时间的相对丰度。

ABSTRACT9909308FedoRifted continental margins evolve from tectonically and volcanically active early in their history, to a more passive phase once the margin matures. Such geologic events occur on a backdrop of local and global climatic conditions that may be linked to the drifting of continents into different latitudes. Consequently, both tectonics and climate could exert significant influence on the composition of sediments that result from rifting processes. In this regard, the composition of siliciclastic sedimentary rocks deposited during and subsequent to the fragmentation of a continent serve as a recording of not only evolving source rock compositions and positions relative to rift flanks, but also of the prevailing climatic conditions during the time of separation. The proposed investigation endeavors to critically examine Neoproterozoic- and Cambrian-aged siliciclastic rocks in the southwestem United States that were deposited during, and in the wake of, the fragmentation of Rodinia. A goal is to determine the relative significance of tectonics and climate in shaping the composition of the sediments. This information, coupled with extant sedimentologic and stratigraphic data, will then be used to build a comprehensive data bank in which to decipher the early geologic history of this rifted continental margin, whose evolution is still in great debate. Data collected in this study will be principally petrographic, geochemical, and isotopic, and aimed at tracking mineral and elemental abundances transferred from source rocks to sediments by considering chemical weathering and diagenetic processes. The study will also focus on determining the whole-rock and detrital feldspar isotopic compositions (Sm-Nd, Pb/Pb), as well as single-crystal zircon U-Pb analyses, as mechanisms to identify specific source rocks and localities, and their relative abundances through time.