EAR-PF: What drove localized pyrite formation and taphonomic bias in the fossil record?

EAR-PF：是什么推动了化石记录中局部黄铁矿的形成和埋藏学偏差？

• 批准号: 2203550
• 负责人: Kelsey Moore
• 金额: $ 18万
• 依托单位: Moore, Kelsey R
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-01 至 2025-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2203550&HistoricalAwards=false
• 关键词: EAR; PF; What; drove; localized

Dr. Kelsey Moore has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out research and education activities at Johns Hopkins University under the mentorship of Professors Emmy Smith and Maya Gomes. For the first 2-3 billion years of Earth history, life was dominated by microbes—simple organisms like bacteria and early unicellular eukaryotes. This early life played a fundamental role in in setting life on its evolutionary course and in driving the evolution of our atmosphere and our planet. To learn about this ancient life, how it evolved, and how it interacted with the early Earth, we turn to the fossil record. However, this record is biased because the processes that facilitate fossilization require special circumstances that often selectively fossilize only certain organisms. Fossilization of soft, microbial organisms is especially rare. Luckily, some minerals, like pyrite (FeS2), did preserve a record of ancient soft-bodied microbes. An important example is an assemblage of pyritized Obruchevella, cyanobacterial fossils preserved in the Neoproterozoic Ikiakpuk Formation. These are fossils of photosynthetic bacteria that thrived in the aftermath of a global glacial event—the Sturtian glaciation of the Snowball Earth event. But how these cyanobacteria interacted with the environment and became fossilized remains unclear. This project seeks to better understand the microbial biosphere in the aftermath of this extreme climatic event, how it coped with environmental stresses, and how it became fossilized. It is possible that the cyanobacteria may have played a role in their own fossilization. Modern cyanobacteria produced sulfur-rich organic compounds in responses to environmental stresses and these compounds may have contributed to the formation of pyrite and fossilization in the past. This project will test this hypothesis by conducting fossilization experiments with living organisms that are similar to the fossils. These experiments will be paired with in-depth analysis of the Ikiakpuk Formation and the pyritized fossils that it contains. The aim of this work is to determine how the organisms became fossilized and what biological and abiotic factors contributed to pyrite formation. With these insights, it may be possible to paint a more complete picture of the shallow marine environments after this global glaciation, the microbial communities that thrived in the aftermath of the glaciation, and how those microbes evolved and coped with environmental stresses. While different models for pyritization have been suggested, little attention has been given to the organic compounds produced by the organisms being fossilized and their role in sulfur cycling and iron sulfide nucleation. In particular, the fossils preserved by pyrite in the Ikiakpuk Formation are similar to modern cyanobacteria that produce sulfated polysaccharides, organosulfur compounds that may play a key role in localized pyrite formation. To address this, this project will test the contribution of organosulfates to local pyritization. Through a combination of taphonomy experiments and fossil analysis of pyritized fossil assemblages, this study seeks to determine (1) whether or not organosulfates can be used as a sulfate source for MSR, (2) whether or not this specific localized sulfate source can account for localization of pyritization and preferential preservation of some organisms over others, and (3) whether organosulfur imparts a characteristic sulfur isotope composition in fossil pyrite. This work will take place at Johns Hopkins University in collaboration with Professors Emmy Smith and Maya Gomes, as well as external collaborators Sara Pruss (Smith College) and Francis Macdonald (University of California at Santa Barbara). Experiments with modern microbes will help constrain how microbial biogeochemical makeup, nutrient cycling, and ecological interactions drive fossilization, taphonomic bias, and sulfur isotope fractionation. Analysis of analog fossil assemblages then provides a means of applying these findings to the fossil record and testing hypotheses related to organism diversity and abundance as they relate to taphonomic bias. These combined analyses also provide a means of applying sulfur isotope fingerprints to test the application of a pyritization model that accounts for organosulfates to the rock record. The combination of experimental taphonomy and fossil analyses provides a novel approach to gain insight into ancient microbial communities, seawater chemistry, and the global biosphere beyond the information offered by a single fossil assemblage. This is especially important as we attempt to understand the evolution of environments and the biosphere following a global glacial event like the Sturtian Glaciation. More broadly, this work will inform how we interpret pyritized fossil assemblages in the rock record during other intervals in Earth history and reveal what the isotopic signatures can tell us about ecology, cell physiology, and preservation of organic matter.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.

凯尔西·摩尔博士获得了美国国家科学基金会地球科学博士后奖学金，在艾美·史密斯和玛雅·戈麦斯教授的指导下，在约翰·霍普金斯大学开展研究和教育活动。在地球历史的最初 2-30 亿年里，生命占据了主导地位。微生物——细菌和早期单细胞真核生物等简单生物体，在决定生命的进化过程以及推动我们的大气层和地球的进化方面发挥了重要作用。进化，以及它如何与早期地球相互作用，我们求助于化石记录。然而，这种记录是有偏见的，因为促进化石化的过程需要特殊的环境，通常选择性地仅使某些软体微生物形成化石，这种情况尤其罕见。幸运的是，一些矿物，如黄铁矿（FeS2），确实保存了古代软体微生物的记录，一个重要的例子是黄铁矿化的 Obruchevella 的组合。新元古代 Ikiakpuk 地层中保存的蓝藻化石是在全球冰川事件（雪球地球事件的斯图尔特冰川作用）之后繁盛的光合细菌化石，但这些蓝藻如何与环境相互作用并变成化石仍不清楚。该项目旨在更好地了解这次极端气候事件后的微生物生物圈，它如何应对环境压力，以及它是如何变成这样的现代蓝藻可能在其自身的石化过程中发挥了作用，以应对环境压力，这些化合物可能在过去促进了黄铁矿的形成和石化。将通过与化石相似的生物体进行化石化实验来验证这一假设。这些实验将与对 Ikiakpuk 地层及其所含黄铁矿化石的深入分析相结合。这项工作的目的是确定生物体是如何变成化石的，以及哪些生物和非生物因素促成了黄铁矿的形成。有了这些见解，就有可能描绘出全球冰川作用后的浅海环境、微生物群落的更完整的图景。尽管人们提出了不同的黄铁矿化模型，但人们很少关注化石化生物体产生的有机化合物及其在冰川作用后的作用。特别是，Ikiakpuk 地层中黄铁矿保存的化石与产生硫酸多糖和有机硫化合物的现代蓝细菌相似，这些化合物可能在局部黄铁矿形成中发挥关键作用。通过埋藏学实验和黄铁矿化石分析相结合，了解有机硫酸盐对当地黄铁矿化的贡献。本研究旨在确定 (1) 有机硫酸盐是否可以用作 MSR 的硫酸盐来源，(2) 这种特定的局部硫酸盐来源是否可以解释黄铁矿化的局部性以及某些生物体相对于其他生物体的优先保存， (3) 有机硫是否赋予黄铁矿化石中特有的硫同位素组成 这项工作将在约翰·霍普金斯大学与艾美·史密斯 (Emmy Smith) 和玛雅 (Maya) 教授合作进行。戈麦斯以及外部合作者萨拉·普鲁斯（Sara Pruss）（史密斯学院）和弗朗西斯·麦克唐纳（Francis Macdonald）（加州大学圣巴巴拉分校）对现代微生物进行的实验将有助于限制微生物的生物地球化学组成、营养循环和生态相互作用如何驱动化石化、埋藏学偏差和然后，对模拟化石组合的分析提供了一种将这些发现应用于化石记录并测试与埋藏学相关的生物多样性和丰度相关假设的方法。这些组合分析还提供了一种应用硫同位素指纹来测试黄铁矿化模型的应用的方法，该模型解释了岩石记录中的有机硫酸盐。实验埋藏学和化石分析的结合提供了一种了解古代微生物群落的新方法。 、海水化学和全球生物圈超出了单一化石组合提供的信息，当我们试图了解像冰川这样的全球冰川事件后环境和生物圈的演变时，这一点尤其重要。更广泛地说，这项工作将告诉我们如何解释地球历史上其他时期岩石记录中的黄铁矿化化石组合，并揭示同位素特征可以告诉我们有关生态学、细胞生理学和有机物保存的信息。通过使用基金会的智力价值和更广泛的影响审查标准进行评估，NSF 的法定使命被认为值得支持。