Collaborative Research: Environmental and Biogeochemical Reorganization during the Rise of Atmospheric Oxygen

24亿年前富氧大气的建立预示着在接下来的4亿年里环境变化的进展，永久地改变了全球生物地球化学循环。从Fennoscandia新获得的钻芯提供了一个无与伦比的机会，可以在这段时间内建立更连续的事件年表。一组在同位素、地球化学分析和数值模拟方面有专长的研究人员将通过岩心区间产生一套海洋和大气成分的环境替代物，并在一系列关于大气氧化速度和建立强氧化还原层结的全球海洋的假设的背景下，通过数值模拟对其进行定量解释。这一提议的智力优势集中在重建这一地球历史关键时期全球环境变化序列的重要性。随着太古宙特有的带状铁质地层的沉积停止，广泛的、甚至可能是赤道冰川发生了。随后在海相碳酸盐中出现了长时间的13C富集期，这是第一次，也是地球历史上规模最大、持续时间最长的一次，没有丰富的有机质沉积的预期证据。各种替代物表明，氧化风化只在生物圈渐进性变化的这段时间结束时才变得重要。来自南非的钻探岩心，加上那里以及加拿大、美国、西澳大利亚和芬诺斯坎迪亚的实地研究，记录了这些事件，但记录并不完整。芬诺斯坎迪亚钻探岩芯提供了最好的机会来填补这些空白，解决这一时间间隔的令人困惑的悖论，并建立基于Re-Os的精确年代表，评估大气和海洋的氧化还原演化速度。尽管公众普遍对地下地质结构感兴趣和好奇，但大多数人对地下地质结构的复杂性知之甚少，也不知道地质学家如何将地下地质结构用作地球历史的档案。为了改善这种情况，同时满足该项目更广泛的影响目标，调查人员将与他们的学生、博物馆和专业外展工作人员一起构建一个互动的博物馆展览。参观者将能够从三维显示的复杂地质结构中提取岩芯的长度，并从这些岩芯中重建该地区的地质历史。宾夕法尼亚州立大学地质墙上的3D显示，以及参观者按下按钮生成的合成地震仪，将有助于理解。该项目的其他更广泛的影响包括加强业界对富有机沉积岩的Re-Os系统学领域的兴趣，以及一组学生和研究人员参与一个真正国际化的、跨学科的、多人参与的项目。本科生研究助理将从不同的申请者池中挑选到我们的机构？少数民族外展计划，如十大会议？S暑期研究机会计划。

The establishment of an oxygenated atmosphere 2.4 billion years ago was heralded by a progression of environmental changes over the next 400 million years that permanently transformed global biogeochemical cycling. Newly obtained drillcore from Fennoscandia provides an unparalleled opportunity to establish a more continuous chronology of events through this interval. A team of investigators with expertise in isotopic and geochemical analysis and numerical modeling will produce a suite of environmental proxies of oceanic and atmospheric composition through the cored interval and interpret them quantitatively through numerical modeling in the context of a set of hypotheses concerning the pace of atmospheric oxygenation and the establishment of a strongly redox-stratified global ocean.The intellectual merit of this proposal centers on the importance of reconstructing the sequence of global environmental change during this critical interval of Earth history. Widespread, perhaps even equatorial glaciation occurred as the deposition of banded iron formations, so characteristic of the Archean, ceased. A protracted interval of 13C enrichment in marine carbonates ensued, the first of its kind and the largest and longest in Earth history, without the expected evidence for abundant organic matter deposition.Paradoxically, as carbon isotopic compositions returned to normal, tremendous quantities of organic matter and marine phosphorites were deposited. Various proxies indicate that oxidative weathering only became important toward the end of this interval of progressive biospheric change. Drill core from South Africa, complemented by field studies there and in Canada, the United States, Western Australia and Fennoscandia, have documented these events but the records are incomplete. Fennoscandian drillcore presents the best opportunity yet to fill these gaps, address the perplexing paradoxes of this time interval, and, with the establishment of a precise chronology based on Re-Os, assess the tempo of redox evolution of the atmosphere and ocean.While there is general public interest in and curiosity about the subsurface, most people have little appreciation for the complexity of subsurface geologic structures and have no idea how geologists use the subsurface as an archive of the history of Earth. To improve this situation while addressing the broader impacts goals of the project, the investigators, together with their students, and museum and professional outreach staff will construct an interactive museum exhibit. The visitor will be able to extract lengths of rock core from a complex geologic structure displayed in three dimensions, and from these cores, reconstruct the geologic history of the area. Understanding will be aided by 3-D displays on the Penn State GeoWall, together with synthetic seismographs generated by the visitor at the push of a button. Additional broader impacts of this project include strengthening industry interests in the area of Re-Os systematics of organic-rich sedimentary rocks, and the involvement of a team of students and researchers in a truly international, interdisciplinary, multi-investigator project. Undergraduate research assistants will be drawn from diverse pools of applicants to our institutions? minority outreach program, e.g., the Big Ten Conference?s Summer Research Opportunities Program.