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

复杂的多细胞动物在寒武纪(约5.4亿年前)的黎明首次出现并迅速多样化，可以想象是地球生命进化中最重要的一个插曲，因为它为今天存在的绝大多数生命形式勾勒出了最初的蓝图。理解寒武纪“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--只有很少的化石记录。此外，保存埃迪卡拉纪-寒武纪过渡期的海相沉积岩现在分散在各大洲，阻碍了对地质史这一关键交汇点上的生命和环境的明确重建。这项研究的重点是埃迪卡拉纪-寒武纪海相沉积物的关键露头，这些沉积物具有壮观的化石和高潜力的精确同位素测年，位于纳米比亚-南非边界附近一个以前未勘探的地区。这些结果将对这一关键时间间隔内古环境和海洋化学变化的速度提供新的见解。除了公开演讲和学术出版物外，还计划了一项教育、培训和推广活动的综合计划。该项目在纳米比亚和南非奥兰治河两侧新发现的富含海相碳酸盐和埃迪卡拉纪-寒武纪化石的剖面上采用了野外测绘、沉积学、化学和生物地层学的综合计划，这些剖面具有丰富的夹层火山灰层，适合U-Pb年代学。它将提供高分辨率的记录，有助于解开元古界末期生物和同时代环境变化的模式和速率。这一结果将是检验这一假设的重要一步，该假设认为存在全球同步的环境扰动，这些扰动在遗传上与埃迪卡拉纪-寒武纪边界上的生物周转有关，并将有助于更好地理解寒武纪辐射的驱动机制。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.