Structural and Geochronological Investigations of Neoproterozoic Rifting in Southwestern Laurentia

寒武纪大爆发及其新元古代前体发生在异常的环境扰动背景下，包括冷暖气候的极端波动、可能的真极漂移以及超大陆的重组和最终分裂。构造事件可能是气候和极地漂移事件的主要原因。尽管在过去十年中取得了重大进展，但由于缺乏可靠的全球相关性和与显生宙相当的裂谷和大陆板块运动年表，对大多数这些序列缺乏绝对的年龄控制，严重限制了对新想法的检验。项目建议继续开展地质填图、地层学研究和U/Pb定年计划，以确定劳伦西亚西南部相对完整的新元古代演替。到目前为止，他已经在一个关键区域建立了一个基本的构造和地层格架，该剖面记录了两个主要的冰川间隔及其盖层碳酸盐岩序列（可能与澳大利亚的Sturtian和Marinoan事件相关），以及导致西南劳伦森被动边缘发育的构造作用。此外，他还在该层序中发现了三个新的灰层，并在新元古代的10个主要砂体中发现了丰富的自生xenotime。他将尝试用传统的TIMS分析和锆石和xenotime的微束分析技术来确定这些单元的年代。该项目的更广泛影响包括：i)加州理工学院地质学博士生的研究生培训；ii)多个机构的参与，包括圣安德鲁斯大学、加州大学洛杉矶分校、麻省理工学院和亚利桑那大学的研究工作，包括改善国家基础设施，以确定砂岩中自生矿物的年代；特别是，在这项研究过程中，如果我们成功地开发出一种xenotime分析标准，将立即使世界各地的许多研究人员受益；（iii）在死亡谷国家公园向公众作介绍，这将有助于公众更好地了解公园内自然资源的重要性；iv)研究可能有助于理解生物圈如何响应极端的全球变化，从而有助于关于全球变暖及相关问题的国际辩论的演变。

AbstractThe Cambrian explosion and its Neoproterozoic precursors occurred in a context of extraordinary environmental perturbations, including extreme fluctuations between warm and cold climate, possible True Polar Wander, and the reorganization and eventual breakup of a supercontinent. The tectonic events may have been primary causes of both climatic and polar wander events. Despite significant progress over the last decade, the lack of absolute age control on most of these successions has severely limited testing new ideas owing to a lack of reliable global correlations and a chronology of rifting and continental plate motions on a par with the Phanerozoic. The PI proposes to continue a program of geological mapping, stratigraphic studies, and U/Pb dating of the relatively complete Neoproterozoic succession in southwestern Laurentia. Thus far, he has established a rudimentary structural and stratigraphic framework in a key area where the section records two major glacial intervals and their cap carbonate sequences (presumably correlative with the Sturtian and Marinoan events in Australia), as well as tectonism that led to the development of the southwest Laurentian passive margin. In addition, he has discovered three new ash horizons within this sequence, and found abundant authigenic xenotime in some ten major sand bodies spanning the Neoproterozoic. He will attempt to date these units with conventional TIMS analysis and microbeam analytical techniques on both zircon and xenotime.The broader impacts of this project include: i) graduate training of a doctoral student in geology at Caltech; ii) involvement of multiple institutions, including St. Andrews University, UCLA, MIT and the University of Arizona in the research effort, including improvement of national infrastructure for dating authigenic minerals in sandstones; in particular, development of a xenotime analytical standard in the course of this research, if we are successful, will be of immediate benefit to many researchers around the world; iii) presentations to the public in Death Valley National Park, which will contribute to greater public understanding of the significance of the natural resources in the park; and iv) the research may contribute to understanding how the biosphere responds to the extremes of global change, and therefore contribute to evolving international debate regarding global warming and related issues.