A strongly oxidizing Paleoproterozoic era Two billion years ago, marine sulfate concentrations were around one-third as high as modern ones, constituting an oxidizing capacity equivalent to more than 20% of that of the modern ocean-atmosphere system. Blättler et al. found this by analyzing a remarkable evaporite succession more than 1 billion years older than the oldest comparable deposit discovered to date. These quantitative results, for a time when only more qualitative information was previously available, provide a constraint on the magnitude and timing of early Earth's response to the Great Oxidation Event 2.3 billion years ago. Science, this issue p. 320 The oxidizing capacity of the ocean was one-fifth of modern values in the Paleoproterozoic era. Major changes in atmospheric and ocean chemistry occurred in the Paleoproterozoic era (2.5 to 1.6 billion years ago). Increasing oxidation dramatically changed Earth’s surface, but few quantitative constraints exist on this important transition. This study describes the sedimentology, mineralogy, and geochemistry of a 2-billion-year-old, ~800-meter-thick evaporite succession from the Onega Basin in Russian Karelia. The deposit consists of a basal unit dominated by halite (~100 meters) followed by units dominated by anhydrite-magnesite (~500 meters) and dolomite-magnesite (~200 meters). The evaporite minerals robustly constrain marine sulfate concentrations to at least 10 millimoles per kilogram of water, representing an oxidant reservoir equivalent to more than 20% of the modern ocean-atmosphere oxidizing capacity. These results show that substantial amounts of surface oxidant accumulated during this critical transition in Earth’s oxygenation.

中文翻译：

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20 亿年前的蒸发岩捕获了地球的巨大氧化

强氧化性古元古代 20 亿年前，海洋硫酸盐浓度约为现代的三分之一，其氧化能力相当于现代海洋-大气系统的 20% 以上。布莱特勒等人。通过分析比迄今为止发现的最古老的可比矿床早 10 亿年以上的显着蒸发岩序列，发现了这一点。在以前只有更多定性信息可用的时候，这些定量结果限制了早期地球对 23 亿年前大氧化事件的反应的幅度和时间。科学，这个问题 p。320 在古元古代，海洋的氧化能力是现代值的五分之一。大气和海洋化学的主要变化发生在古元古代（2. 5 到 16 亿年前）。氧化的增加极大地改变了地球表面，但对这一重要转变几乎没有定量限制。这项研究描述了俄罗斯卡累利阿奥涅加盆地 20 亿年前、约 800 米厚的蒸发岩系列的沉积学、矿物学和地球化学。该矿床包括一个以岩盐为主的基底单元（~100 米），其次是以硬石膏-菱镁矿（~500 米）和白云石-菱镁矿（~200 米）为主的单元。蒸发矿物将海洋硫酸盐浓度严格限制在每公斤水至少 10 毫摩尔，代表一个氧化剂库，相当于现代海洋大气氧化能力的 20% 以上。