Constraining the oxygen history of Earth's middle years using redox sensitive tracers

使用氧化还原敏感示踪剂限制地球中年的氧气历史

• 批准号: RGPIN-2016-05401
• 负责人: Partin, Camille
• 金额: $ 2.11万
• 依托单位: University of Saskatchewan
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=661639
• 关键词: Constraining; oxygen; history; Earth; middle

Reconstructing past oxygen: Sedimentary rocks, if interpreted correctly, can provide a timeline of the tumultuous oceanic and atmospheric conditions on the evolving Earth. The first long-lived accumulation of atmospheric oxygen began ~2.4 billion years ago (Ga), classically known as the Great Oxidation Event. Although this event has been documented for some time, mounting evidence points to more dynamic oxygen trends than previously thought. High oxygen levels at this time are implied by several lines of evidence, including high, modern-like concentrations of elements sensitive to oxidation and reduction (redox) reactions and high organic carbon in marine shales. Recent research shows a reversal of these oxygenation trends after ~2.05 Ga—contrary to a long-held view that oxygen increased with time. This de-oxygenation event is poorly-resolved, but might provide important links to understanding how surface conditions were inadequate for complex biological evolution. It could also provide analogues for rapid changes in ocean chemistry reminiscent of that attendant with modern climate change.***Objectives: My research program aims to reveal the early developmental stages of the air we breathe. This research integrates advanced analytical techniques that address globally significant questions, including the causes and consequences of Earth's fledgling surface oxygen conditions. A robust record of oxygen history provides insight into the co-evolution of life or impediments to it. “Chicken and egg” arguments remain in the literature regarding the cause and effect of atmospheric oxygen rise, global glaciations, and biological evolution, including the advent of oxygenic photosynthesis.*** ***Scientific Approach: Past environmental conditions will be reconstructed using complementary geochemical methods, including isotopes of uranium, chromium, and molybdenum, coupled with redox-sensitive element concentrations. This research will track early oxygen conditions using these tools to illuminate the extent of anoxic conditions in ocean waters. Stratigraphic and radiometric dating methods will help determine the rate and timing of these changes.***Impact: The Earth system experienced a major disturbance that derailed a trend towards modern-like environmental conditions, but possible mechanistic explanations for this reversal are lacking. This research will investigate hypotheses related to both increasing and decreasing oxygen trends and concentrations of bioavailable elements in the oceans during key times in the geologic past. Piecing together Earth's path to its current oxygenated state is pivotal to unraveling biogeochemical feedbacks in the Earth system. Feedback mechanisms in past oceans have the potential to provide insights into the long-term consequences of modern-day oxygen-starved ocean waters that are increasing in conjunction with modern climate change. **

重建过去的氧气：如果正确解释，沉积岩石可以在不断发展的地球上提供动荡的海洋和大气条件的时间表。大气氧的首次长期积累始于约24亿年前（GA），通常被称为大氧化事件。尽管该事件已记录了一段时间，但越来越多的证据表明，比以前想象的要多的动态氧趋势。目前，高氧气水平由几条证据暗示，包括对氧化和还原（氧化还原）反应敏感的元素的高浓度和海洋阴影中的有机碳。最近的研究表明，在〜2.05 GA之后，这些氧合趋势的逆转 - 对持续的观点，即氧气随时间增加。这种脱氧事件的分辨率很差，但可能会提供重要的联系，以了解表面条件如何不足以进行复杂的生物学进化。它还可以为海洋化学的快速变化提供类似物，以提醒人们随着现代气候变化的范围。***目标：我的研究计划旨在揭示我们呼吸的空气的早期发育阶段。这项研究集成了晚期分析技术，这些技术解决了全球重要的问题，包括地球果落表面氧气条件的原因和后果。氧气历史记录的强大记录为生命的共同发展或障碍提供了深入的了解。文献中仍然存在有关大气氧升高，全球冰川和生物进化的原因和影响的“鸡肉和鸡蛋”的论点，包括氧气光合作用的发展。这项研究将使用这些工具来追踪早期氧气状况，以阐明海水中的缺氧条件的程度。分层和辐射测年方法将有助于确定这些变化的速度和时机。这项研究将调查与地质过去关键时期海洋中氧气趋势的增加和降低相关的假设。将地球通往其当前的氧化状态的路径拼凑在一起对于揭示地球系统中生物地球化学反馈的关键。过去海洋中的反馈机制有可能洞悉现代氧气含量的海水的长期后果，这些海水随着现代气候变化而增加。 **