Development of a High-Resolution Stromatolite Facies Model: Environmental Impacts at the Dawn of Oxygenation

高分辨率叠层石相模型的发展：氧气黎明时的环境影响拉塞尔·沙皮罗加州州立大学，奇科州立大学阿米基盆地的古元古代含铁地层中有一些保存最完好的微化石和各种叠层石，它们来自地球从缺氧海洋向富氧海洋转换的时期。对于古生物学家、地球化学家和经济地质学家来说，这一间歇期被称为“大氧化事件”，是一个日益重要的研究领域。然而，叠层石沉积的古环境背景仍然存在重要问题，限制了对海洋条件和局部细菌生态系统之间复杂相互作用的了解。这项建议通过将强大的3-D建模软件(Petrel v.2010)应用于一系列非凡的专有钻芯，解决了叠层石如何随着海洋和环境条件的变化而在空间中发生变化。具体地说，这项建议涉及：(1)叠层石在多大程度上可以用来描绘海岸线地貌，加强古环境重建？以及(2)埋藏学在叠层石和微化石保存中的作用是什么？在整个阿米基盆地大约两个米尺度的层位中发现了四种主要的叠层石类型，尽管不一定是连续的层位。露天塔可岩矿壁(现已被淹)的测绘表明，宏观结构的变化出现在10至100米的尺度上。叠层石是生物成因的，是在正常的海洋条件下形成的，在亚氧水域的化学跃层上方。基于这项工作，人们认为叠层石的宏观结构形式，连同稀少但保存完好的微化石记录，可以与沉积学和地层学数据相结合，开发出叠层石生物面模型，这将有助于约束地球历史这一关键时期的独特海洋学变异性。拟议的研究项目将以空间分辨率来研究叠层石的变化和古环境构造含义，这在以前的研究中是没有达到的。该项目的研究结果将对研究其他前寒武纪盆地在“大氧化事件”期间的古生物和生物地球化学模式具有重要价值。传播计划要求开发一系列YouTube短片，向广大观众展示早期氧化地球微生物-沉积物相互作用的动态和复杂世界。这项研究将为一所以本科为主的机构的几名本科生提供关键的初步研究经验。通过更好地了解这一关键的间歇时间和基于项目的学习机会，PI的教学方法将得到改进，这构成了他的教学方法的一个组成部分。

Development of a High-Resolution Stromatolite Facies Model: Environmental Impacts at the Dawn of OxygenationRussell ShapiroCalifornia State University, Chico StateThe Paleoproterozoic iron-bearing formations of the Animikie Basin host some of the best-preserved microfossils and diverse stromatolites from a time when the Earth was switching from anoxic to euxinic oceans. This interval, known as the "Great Oxidation Event," is an increasingly important research area for paleobiologists, geochemists, and economic geologists. However, important questions still exist as to the paleoenvironmental setting of the stromatolitic deposits, limiting the understanding of the complex interplay between oceanic conditions and the localized bacterial ecosystems. This proposal addresses how stromatolites vary in space in response to changing oceanographic and environmental conditions by applying powerful 3-D modeling software (Petrel v.2010) to an extraordinary collection of proprietary drill core. Specifically, this proposal addresses: (1) To what extent can the stromatolites be used to delineate shoreline geomorphology, enhancing paleoenvironmental reconstructions? and (2) What is the role of taphonomy in both stromatolite and microfossil preservation?Four major stromatolite types are found in roughly two, meter-scale horizons throughout the Animikie Basin, though not necessarily as continuous horizons. Mapping of open taconite mine walls (now flooded) demonstrated that macrostructural variability appears at scales of 10 to 100 meters. The stromatolites are biogenic and formed under normal marine conditions, above the chemocline, in suboxic waters. Based on this work, it is believed that the macrostructural forms of stromatolites, together with the sparse but well-preserved microfossil record, can be integrated with the sedimentologic and stratigraphic data to develop a model of stromatolite biofaces that will help to constrain the unique oceanographic variability in this critical interval of Earth history. The proposed research project will address stromatolite variation and the paleoenvironmental tectonic implications at a spatial resolution that has not been achieved in previous studies of this interval.Broader Impacts. The results of this project will be valuable to researchers studying paleontological and biogeochemical patterns in other pre-Cambrian basins during the "Great Oxidation Event." The dissemination plan calls for the development of a series of YouTube short films that will open up the dynamic and complex world of microbial-sediment interactions of the early oxygenated Earth to a broad audience. The research will provide critical primary research experience for several undergraduate students at a primarily undergraduate institution. The teaching methods of the PI will be enhanced with a greater understanding of this critical interval and opportunities for project-based learning which form an integral component of his pedagogy.