Structural and Geochronological Investigations of Neoproterozoic Rifting in Southwestern Laurentia

寒武纪大爆发及其新元古代的前兆发生在异常的环境扰动的背景下，包括温暖和寒冷气候之间的极端波动，可能的真极地漫游，至少一次重大的撞击事件，以及超大陆的重组和最终解体。 构造事件可能是气候和极移事件的主要原因。 尽管在过去的十年中取得了重大进展，但缺乏对关键继承的绝对年龄控制，严重限制了发展可靠的全球相关性和与中生代相当的裂谷和大陆板块运动年表。 在这个项目中，研究人员正在获得碎屑锆石上自生磷钇矿过度生长的U/Pb年龄，以及碎屑锆石的标准U/Pb年龄，从西南劳伦（金斯顿和帕纳明特山脉，南加州）相对完整的新元古代序列的砂岩。 这一系列包含了丰富的记录，多个裂谷事件和随后的被动边缘沉降，穿插着记录的冰川和随后的变暖事件，切口，和可能的影响事件。 研究人员对关键区域进行了采样，这些区域包含许多对裂谷和冰川作用相对时间的结构和地层限制，并正在测试最近的一个假设，即被动边缘序列中的特定砂岩层包含来自Accident撞击结构的碎屑，这将提供东冈瓦纳和劳伦特之间的关键时间相关层位，并建议在沉降期间靠近澳大利亚南部和西南劳伦蒂亚。

EAR-0107123WernickeThe 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, at least one significant impact event, and the reorganization and eventual breakup of a supercontinent. The tectonic events may have been a primary cause of both climatic and polar wander events. Despite significant progress over the last decade, the lack of absolute age control on key successions has severely limited developing reliable global correlations and a chronology of rifting and continental plate motions on a par with the Phanerozoic. For this project, the investigators are obtaining U/Pb ages of authigenic xenotime overgrowths on detrital zircons, as well as standard U/Pb dating on detrital zircons, on sandstones from the relatively complete Neoproterozoic succession in southwestern Laurentia (Kingston and Panamint Ranges, southern California). This succession contains a rich record of multiple rifting events and subsequent passive margin subsidence, interspersed with a record of glaciations and subsequent warming events, incisions, and a possible impact event. The investigators have sampled key areas that contain a number of structural and stratigraphic constraints on the relative timing of rifting and glaciation, and are testing a recent hypothesis that a particular sandstone horizon in the passive margin sequence contains detritus derived from the Acraman impact structure, which would provide a key time-correlative horizon between East Gondwana and Laurentia, and suggest proximity of southern Australia and southwestern Laurentia during subsidence.