Evaluating Atmospheric Oxygen Levels During the Great Oxidation Event

富氧大气的建立对生物进化过程产生了深远的影响，为真核细胞的出现铺平了道路，并最终使包括人类在内的大型动物的进化成为可能。这些条件并不总是存在的：大量的地质证据表明，在24亿年前的地球历史早期，大气和海洋中没有氧气，但随后的氧合历史没有得到很好的解决。这项研究解决了氧气首次出现后的一个关键时间间隔，大约在22亿到20亿年前，当时诱人的地质证据表明，氧气水平可能已经上升到甚至超过现代水平，然后下降到更低的水平，然后又持续了10亿年半，然后再次上升到足以支持动物进化的水平。最近在芬诺斯坎迪亚岩石中钻探的岩芯(由NSF资助)显示的特征似乎反映了地下水的极端氧化，地下水渗透到了古老的火山景观中。这些岩芯将使用各种微观和地球化学技术进行仔细检查，以检验它们暴露在高含氧量水中的假设，这些水本身就是大氧化事件期间大气氧“过冲”的结果。参与这一项目的将是一名博士生，一名正在撰写高级论文的本科生，以及一名暑期研究实习生，他们参与了我们正在进行的向少数族裔服务机构的本科生推广地球科学研究的计划。这个合作小组将与他们在威斯康星大学和欧洲的同事合作，探索地球遥远过去的深地核和环境变化的性质。

The establishment of an oxygen-rich atmosphere had a profound influence on the course of biological evolution, paving the way for the advent of eukaryotic cells and ultimately enabling the evolution of large animals, including humans. These conditions did not always exist: a substantial body of geologic evidence indicates that the atmosphere and oceans were free of oxygen during early part of Earth's history, prior to 2.4 billion years ago, but the subsequent history of the oxygenation is poorly resolved.This study addresses a key interval just after the first appearance of oxygen, from about 2.2 to 2.0 billion years ago, a time when tantalizing geologic evidence suggests that oxygen levels may have risen to levels that even exceeded modern levels before falling to lower levels that persisted for another billion and a half years before rising again to levels high enough to support the evolution of animals. Cores recently drilled in Fennoscandian rocks (with NSF funding) display features that appear to reflect extreme oxidation by groundwaters that permeated an ancient volcanic landscape. These cores will be scrutinized using a variety of microscopic and geochemical techniques to test the hypothesis that they were exposed to highly oxygen charged waters, themselves the consequence of an "overshoot" of atmospheric oxygen during the Great Oxidation Event.Participating in this project will be a Ph.D. student, an undergraduate working on a senior thesis, and a summer research intern participating in our ongoing program promoting earth sciences research to undergraduates from minority-serving institutions. This collaborative group will partner with their colleagues at the University of Wisconsin and in Europe in their exploration of the FAR-DEEP cores and the nature of environmental change in Earth's distant past.