Resolving how Earth surface redox conditions evolved through the Proterozoic Eon is fundamental to understanding how biogeochemical cycles have changed through time. The redox sensitivity of cerium relative to other rare earth elements and its uptake in carbonate minerals make the Ce anomaly (Ce/Ce*) a particularly useful proxy for capturing redox conditions in the local marine environment. Here, we report Ce/Ce* data in marine carbonate rocks through 3.5 billion years of Earth’s history, focusing in particular on the mid-Proterozoic Eon (i.e., 1.8 – 0.8 Ga). To better understand the role of atmospheric oxygenation, we use Ce/Ce* data to estimate the partial pressure of atmospheric oxygen (pO₂) through this time. Our thermodynamics-based modeling supports a major rise in atmospheric oxygen level in the aftermath of the Great Oxidation Event (~ 2.4 Ga), followed by invariant pO₂ of about 1% of present atmospheric level through most of the Proterozoic Eon (2.4 to 0.65 Ga).

解决地球表面氧化还原条件如何通过元古代 Eon 演变是了解生物地球化学循环如何随时间变化的基础。铈相对于其他稀土元素的氧化还原敏感性及其在碳酸盐矿物中的吸收使得 Ce 异常 (Ce/Ce*) 成为捕获当地海洋环境中氧化还原条件的特别有用的代表。在这里，我们报告了 35 亿年地球历史中海相碳酸盐岩中的 Ce/Ce* 数据，特别关注元古代中期（即 1.8 – 0.8 Ga）。为了更好地理解大气氧合的作用，我们使用 Ce/Ce* 数据来估算大气氧分压 (pO ₂) 通过这段时间。我们基于热力学的模型支持在大氧化事件 (~ 2.4 Ga) 之后大气中的氧气水平显着上升，随后_在元古代的大部分时间（2.4 至 0.65嘎）。