Collaborative Research: Calibrating the end-Ediacaran Extinction with U-Pb Geochronology & Chemostratigraphy at a New Precambrian-Cambrian Boundary Site in Namibia & South

在寒武纪（约5.4亿年前）的黎明，复杂的多细胞动物的首次出现和快速多样化可以想象是地球生命进化中最重要的一幕，因为它为今天存在的绝大多数生命形式奠定了最初的蓝图。理解寒武纪“大爆发”的驱动机制一直具有挑战性，因为在前一时期占主导地位的生命形式，埃迪卡拉纪，有一个稀疏的化石记录。此外，保存埃迪卡拉-寒武纪过渡期的海洋沉积岩现在分散在各大洲，阻碍了在地质历史的这一关键转折点上明确重建生命和环境。这项研究的重点是埃迪卡拉-寒武纪海洋沉积物的关键露头，这些沉积物具有壮观的化石和在纳米比亚-南非边境附近以前未勘探过的地区进行精确同位素测年的高潜力。这些结果将为在这一关键时间间隔内古环境和海洋化学变化的速率提供新的见解。除了公开演讲和学术出版物外，还计划开展一项全面的教育、培训和外联活动。该项目采用了野外制图、沉积学、在纳米比亚和南非橙子河两侧新发现的富含碳酸盐和含碳酸盐的埃迪卡拉-寒武纪剖面上进行了化学和生物地层学研究，Pb年代学它将提供一个高分辨率的记录，将有助于解开模式和速率的生物和同时代的环境变化在结束的元古代。这些结果将是检验这一假设的重要一步，即存在全球同步的环境扰动，这些扰动与埃迪卡拉-寒武纪边界的生物更替在遗传上有关，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，更广泛的影响审查标准。

The first appearance and rapid diversification of complex, multicellular animals at the dawn of the Cambrian (~540 million years ago) is conceivably the single most significant episode in the evolution of life on Earth, as it laid out the initial blueprints for the vast majority of life forms that exist today. Understanding the driving mechanisms of the Cambrian 'explosion' have been challenging because life forms that dominated the preceding period, the Ediacaran, have a sparse fossil record. In addition, the marine sedimentary rocks that preserve the Ediacaran-Cambrian transition are now scattered across the continents, hampering an unequivocal reconstruction of life and the environment at this crucial junction of the geologic history. This study focuses on key outcrops of the Ediacaran-Cambrian marine deposits with spectacular fossils and high potential for precise isotopic dating in a previously unexplored region near the Namibia-South Africa border. The results will provide new insights into the rates of paleoenvironmental and ocean chemical change during this critical time interval. In addition to public presentations and scholarly publications, a comprehensive program of educational, training, and outreach activities are planned.This project employs an integrated program of field mapping, sedimentology, chemo- and bio-stratigraphy on newly discovered marine carbonate-rich and fossiliferous Ediacaran-Cambrian sections on either side of the Orange River in Namibia and South Africa with abundant intercalated ash beds suitable to U-Pb geochronology. It will provide a high-resolution record that will help to unravel the mode and rates of biotic and coeval environmental changes at the close of the Proterozoic. The results will be a major step forward in testing the hypothesis that there were globally synchronous environmental perturbations that were genetically associated with biotic turnover across the Ediacaran-Cambrian boundary, and will lead to a better understanding of the driving mechanisms of the Cambrian radiation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.