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: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741920
• 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.

自从微生物生命出现在地球上以来，早在41亿年前(GA)，它的进化就直接与地球表面环境的进化联系在一起。这种耦合进化是控制微量元素循环的地质和生物过程的综合结果。微生物谱系需要大量的微量元素作为代谢活动所必需的微量营养素或作为酶的组成部分。因此，古代海洋沉积记录中微量元素丰度的变化可能与生物进化有关。铁建造是在太古代(4.0~2.5Ga)和古元古代(2.5~1.6Ga)大洋中沉积的富含铁和硅的化学沉积岩，已被广泛用于重建微量元素丰度。这些都是特别重要的记录，因为大部分的铁形成沉积发生在大氧化事件(2.48至2.32Ga)的前一段和之后；这是表面环境中氧的第一次永久上升和一次根本性的生物转变。然而，到目前为止，太古代至古元古代铁建造的微量元素记录和化学地层剖面主要是在粗采样分辨率下建立的，关于古代海水成分的推断是从微量元素分配到前体矿物相的经验模型得出的。这些因素阻碍了对驱动短期微量元素变异性的环境或生物控制的识别，并导致了对古代海水成分的不同估计。调和这些不确定性对于我的研究方案的长期目标至关重要：对地球历史上耦合的海洋、地球化学和生物进化有更深入的了解。因此，在NSERC的这份发现赠款提案中，我概述了三个短期目标，旨在提高我们对古海洋环境中的古海洋地球化学条件和对微量元素循环的控制的了解。目标1和目标2将产生新的化学地层学记录，包括跨越3.8Ga地球历史的硅质岩记录，以及来自大氧化事件附近沉积的2.5Ga铁质地层的高分辨率记录。这些新的记录将产生对微量元素可用性的洞察，这些洞察可以与现有的记录相结合，并对在全球氧气增加期间导致十年至千年尺度的微量元素变异性的机制产生限制。目标3将使用这些记录以及前驱沉积物到铁结构、氢氧化铁和无定形二氧化硅的热力学表面络合模型，以阐明对古代海水组成的可靠估计。这些项目旨在支持我的长期目标，即限制生命和地球表面环境在过去4年中如何同步进化。