Chemostratigraphic insights on the evolution of surface environments and life over Earth's history

关于地球历史上表面环境和生命演化的化学地层学见解

• 批准号: RGPIN-2021-02523
• 负责人: Robbins, Leslie
• 金额: $ 1.82万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=755041
• 关键词: Chemostratigraphic; insights; evolution; surface; environments

SUMMARY Since the appearance of microbial life on Earth, as early as 4.1 billion years ago (Ga), its evolution has been tied directly to that of Earth's surface environments. This coupled evolution is the combined result of geological and biological processes that control trace element cycling. A number of trace elements are required by microbial lineages as micronutrients necessary for metabolic activity or as components in enzymes. Variations in trace element abundances in the ancient marine sedimentary record may therefore be tied to biological evolution. Iron formations, iron- and silica-rich chemical sedimentary rocks that precipitated in the Archean (4.0 to 2.5 Ga) and Paleoproterozoic (2.5 to 1.6 Ga) oceans, have been used extensively to reconstruct trace element abundances. These are especially important records, as the bulk of iron formation deposition occurs in the immediate lead up, and aftermath, of the Great Oxidation Event (2.48 to 2.32 Ga); the first permanent rise of oxygen in surface environments and a fundamental biological transition. To date, however, trace element records and chemostratigraphic profiles for Archean to Paleoproterozoic iron formations have been primarily constructed at coarse sampling resolutions and inferences regarding ancient seawater composition have been drawn from empirical models of trace element partitioning to precursor mineral phases. These factors have hindered the identification of environmental or biological controls that drive short-term trace element variability and have led to contrasting estimates for ancient seawater composition. Reconciling such uncertainties is critical to the long-term objective of my research programme: gaining a more robust understanding of coupled marine geochemical and biological evolution over Earth's history. Accordingly, in this NSERC Discovery Grant proposal, I have outlined three short-term objectives that seek to improve our understanding of paleomarine geochemical conditions and the controls on trace element cycling in ancient marine settings. Objectives 1 and 2 will generate new chemostratigraphic records including a chert record that spans 3.8 Ga of Earth's history and high-resolution records from 2.5 Ga iron formations deposited close to the Great Oxidation Event. These novel records will generate insights into trace element availability, which can be integrated with existing records, and constraints on the mechanisms that led to decadal to millennial scale trace element variability during increasing global oxygenation. Objective 3 will use these records alongside thermodynamically grounded surface complexation models for the precursor sediments to iron formations, iron oxyhydroxides and amorphous silica, to elucidate robust estimates for the composition of ancient seawater. These projects are designed to support my long-term goal of constraining how life and Earth's surface environments have evolved in tandem over the last 4 Ga.

总结自从地球上出现微生物寿命以来，早在41亿年前（GA），其演变就直接与地球表面环境息息相关。这种耦合进化是控制痕量元素循环的地质和生物学过程的综合结果。微生物谱系需要许多痕量元素是代谢活性或酶中所需的微量营养素。因此，古代海洋沉积记录中的痕量元素丰度的变化可能与生物进化有关。在大将军（4.0至2.5 GA）和古植物学（2.5至1.6 GA）海洋中沉淀的铁形成，铁和富含二氧化硅的化学沉积岩，已广泛用于重建痕量元素丰度。这些是特别重要的记录，因为大部分铁形成沉积发生在大型氧化事件（2.48至2.32 ga）中的直接引线和后果中；氧在地面环境中的第一个永久性升高和基本的生物学转变。然而，迄今为止，痕量元素记录和化学地层学概况主要是在粗制采样的分辨率上构建的，而对古代海水组成的推论是从痕量元素分配到前体矿物阶段的经验模型中得出的。这些因素阻碍了鉴定环境或生物控制，这些环境或生物控制促进了短期痕量元素的可变性，并导致了古代海水组成的对比估计。调和这种不确定性对于我的研究计划的长期目标至关重要：对耦合的海洋地球化学和生物学进化，对地球历史有了更强烈的了解。因此，在这项NSERC Discovery Grant提案中，我概述了三个短期目标，这些目标旨在提高我们对古玛林地球化学条件的理解以及对古代海洋环境中痕量元素循环的控制。目标1和2将产生新的化学地层学记录，包括CHERT记录，该记录涵盖了3.8 GA的地球历史记录和来自2.5 GA铁地层的高分辨率记录，这些记录被沉积在大氧化事件附近。这些新颖的记录将产生对痕量元素可用性的见解，该元素可与现有记录集成在一起，并限制了导致全球氧合期间千禧年量表痕量元素可变性的机制的限制。目标3将使用这些记录与热力学接地的表面络合模型一起，用于铁层，铁氧化铁和无定形二氧化硅的前体沉积物，以阐明对古代海水组成的强大估计。这些项目旨在支持我的长期目标，即限制了在过去4 GA中生命和地球的表面环境如何串联演变。