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

裂谷大陆边缘从其历史早期的构造和火山活动演变为更被动的阶段，一旦边缘成熟。这些地质事件发生的背景是当地和全球的气候条件，可能与大陆漂移到不同的纬度有关。因此，构造和气候都可能对裂谷作用产生的沉积物的成分产生重大影响。在这方面，在大陆碎裂期间和之后沉积的硅屑沉积岩的成分不仅记录了源岩成分的演变和相对于裂谷侧翼的位置，而且还记录了分离期间的主要气候条件。拟议的调查致力于严格检查美国西南部新元古代和寒武纪时代的硅质碎屑岩，这些碎屑岩是在罗迪尼亚碎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成分方面的相对重要性。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，在其中破译这一裂谷大陆边缘的早期地质史，其演化仍存在巨大争议。这项研究收集的数据将主要是岩相学、地球化学性质和同位素，目的是通过考虑化学风化和成岩过程来追踪从源岩转移到沉积物的矿物和元素丰度。这项研究还将侧重于确定全岩和碎屑长石的同位素组成(Sm-ND、铅/铅)以及单晶锆石U-Pb分析，以此作为识别特定源岩和地点及其随时间变化的相对丰度的机制。

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.