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

24亿年前，含氧大气的形成预示着在接下来的4亿年里，环境变化的进展永久性地改变了全球生物地球化学循环。从Fennoscandia获得的新岩心提供了一个无与伦比的机会，通过该段建立一个更连续的事件年表。一组具有同位素、地球化学分析和数值模拟专业知识的研究人员将通过岩心层段产生一套海洋和大气组成的环境代用物，并在一系列关于大气氧合速度和建立强氧化还原层状全球海洋的假设背景下，通过数值模拟对其进行定量解释。这一建议的智力价值集中在重建地球历史上这一关键时期全球环境变化序列的重要性上。当太古宙典型的带状铁地层沉积停止时，广泛的，甚至可能是赤道的冰川作用发生了。随后，海洋碳酸盐中出现了一段较长时间的13C富集期，这是地球历史上第一次出现这种富集期，也是最大、最长的一次，但并没有预期的大量有机物沉积的证据。矛盾的是，当碳同位素组成恢复正常时，大量的有机物和海相磷矿沉积了下来。各种替代指标表明，氧化风化作用仅在这一渐进式生物圈变化区间结束时才变得重要。来自南非的岩心，加上在南非、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。Fennoscandian钻井岩心提供了最好的机会来填补这些空白，解决这个时间间隔的复杂矛盾，并根据Re-Os建立精确的年表，评估大气和海洋氧化还原演化的速度。虽然公众对地下有普遍的兴趣和好奇心，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利用地下作为地球历史的档案。为了改善这种情况，同时解决项目更广泛的影响目标，研究人员将与他们的学生、博物馆和专业外联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展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显示器，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工业界对富有机质沉积岩Re-Os系统学领域的兴趣，以及一个由学生和研究人员组成的团队参与到一个真正的国际、跨学科、多研究者的项目中。本科研究助理将从不同的申请者中抽取到我们的机构？少数族裔外展计划，例如十大会议？夏季研究机会计划。

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.