Earth’s Great Oxidation Event (GOE), ca. 2.5 to 2.0 Ga, was one of the most extreme environmental perturbations in the history of the planet. In addition to the first sustained accumulation of O₂ in the atmosphere, the latter half of the GOE is associated with a very large positive carbon isotope excursion, both in terms of magnitude and inferred duration. The end of the GOE may have been associated with a decrease in atmospheric oxygen levels, although this transition remains poorly understood. We test if this suggested decline in atmospheric O₂ is reflected in the molybdenum stable isotope compositions (δ⁹⁸Mo) and Ce anomalies of a large number (N=299) of carbonate sedimentary rocks collected from Finnish Lapland and the Canadian Labrador Trough and Belcher Group, which collectively span ca. 2.1 – 1.88 Ga. Clear evidence for a shift in redox conditions across the end-GOE is obscured by coupled stratigraphic variations in δ⁹⁸Mo values, Ce anomalies, and Mn concentrations, suggesting local controls on these redox proxies as a function of depositional environment, likely as a result of particulate shuttling of Mo and Ce associated with Mn redox cycling across a chemocline. The most negative Ce anomalies recorded in the Belcher Group (<0.6) are among the lowest reported in literature from the mid-late Paleoproterozoic to early Neoproterozoic; however, the strong local controls on these proxies hinder direct evaluation of secular trends. These findings highlight the critical role of stratigraphic and paleobasinal context for the robust interpretation of δ⁹⁸Mo values and Ce anomalies for the evolution of marine redox conditions.

地球的大氧化事件（GOE），约。2.5 到 2.0 Ga，是地球历史上最极端的环境扰动之一。除了第一次在大气中持续积累 O _{2 外}，GOE 的后半部分与非常大的碳同位素正偏移有关，无论是在量级还是推断持续时间方面。GOE 的结束可能与大气氧含量的下降有关，尽管这种转变仍然知之甚少。我们测试了这种建议的大气 O ₂下降是否反映在钼稳定同位素组成（δ ⁹⁸从芬兰拉普兰和加拿大拉布拉多海槽和贝尔彻群收集的大量 (N = 299) 碳酸盐沉积岩的 Mo) 和 Ce 异常，它们共同跨越约 2.1 – 1.88 Ga。 δ ^{98 的}耦合地层变化掩盖了整个 GOE 末端氧化还原条件变化的明确证据Mo 值、Ce 异常和 Mn 浓度，表明这些氧化还原代理的局部控制作为沉积环境的函数，可能是由于 Mo 和 Ce 的微粒穿梭与跨越趋化层的 Mn 氧化还原循环相关的结果。Belcher 组中记录的最负的 Ce 异常（<0.6）是在古元古代中晚期到新元古代早期文献报道中最低的；然而，对这些代理的强有力的地方控制阻碍了对长期趋势的直接评估。这些发现强调了地层和古盆地背景对于海洋氧化还原条件演化的δ ⁹⁸ Mo 值和 Ce 异常的稳健解释的关键作用。