Was the Great Oxidation Event a sharp or an oscillating build-up of free atmospheric oxygen? A combined S-Mo-Se isotope study of continuous drill core records through the Duitschland/ Rooihoogte and Timeball Hill Formations, Transvaal Basin, South Africa

大氧化事件是大气中游离氧的急剧积累还是振荡积累？

• 批准号: 404683989
• 负责人: Professor Dr. Ronny Schönberg, Ph.D.
• 金额: --
• 依托单位: Institut für Geologie und Paläontologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/404683989?language=en
• 关键词: Was; Great; Oxidation; Event; sharp

The first permanent rise in atmospheric oxygen levels occurred during the Paleoproterozoic Great Oxidation Event (GOE) during which oxygen concentrations rose from less than ca. 0.001% to ~1.5 % of the present atmospheric level, which paved the way for the development of all higher life forms. The disappearance of mass-independently fractionated sulfur isotopes (MIF-S) defines the GOE, but the correlation of various sedimentary successions from different parts of the Transvaal Basin make an exact timing of the GOE difficult. The current existence of two contrasting models about the onset and the timing of the GOE further complicate defining a precise timing. The first model places the onset of the GOE at 2.33 Ga that is characterized by a sharp and rapid increase in oxygen levels, whereas the second model places the onset of the GOE more than 100 million years earlier and identifies the GOE as an oscillating oxygenation event. It is therefore extremely crucial to study a continuous succession of sediments. New drill cores intersecting the entire Duitschland Formation and the overlying Lower Timeball Hill Formation allow for the first to investigate this key oxygenation event. The major goal of this project is to perform combined multiple S, Mo and Se isotope analyses on the new drill core material, which will lead to a more comprehensive understanding about the onset, the timing and the oxygen dynamics during the GOE. The combination of multiple S, Mo and Se isotopes further allows investigating the oxygenation of the oceans at that time. Of particular interest is to identify whether the mobilization of redox-sensitive elements are the result of oxidative continental weathering due to increasing atmospheric oxygen levels or result from the accumulation of oxygen in shallow-marine oxygen oases.

大气中氧气水平的第一次永久性上升发生在古元古代大氧化事件（GOE）期间，在此期间氧气浓度从低于大约上升到大约100％。目前大气水平的 0.001% 至 ~1.5%，这为所有高等生命形式的发展铺平了道路。与质量无关的分馏硫同位素 (MIF-S) 的消失定义了 GOE，但来自德兰士瓦盆地不同部分的各种沉积序列的相关性使得 GOE 的准确计时变得困难。目前关于 GOE 的开始和时间存在两种截然不同的模型，这使得精确时间的定义变得更加复杂。第一个模型将 GOE 的起始时间设定为 2.33 Ga，其特征是氧气水平急剧且迅速增加，而第二个模型将 GOE 的起始时间提前一亿多年，并将 GOE 识别为振荡氧合事件。因此，研究连续的沉积物序列极为重要。与整个 Duitschland 地层和上覆的 Lower Timeball Hill 地层相交的新钻芯可以首次调查这一关键的氧化事件。该项目的主要目标是对新的钻芯材料进行多种硫、钼和硒同位素分析，这将有助于更全面地了解GOE过程中的起始、时间和氧动力学。多种硫、钼和硒同位素的组合进一步可以研究当时海洋的氧化情况。特别令人感兴趣的是确定氧化还原敏感元素的动员是否是由于大气中氧气水平增加而导致的氧化大陆风化的结果，还是浅海海洋含氧绿洲中氧气积累的结果。