The early evolutionary and much of the extinction history of marine animals is thought to be driven by changes in dissolved oxygen concentrations ([O₂]) in the ocean^1,2,3. In turn, [O₂] is widely assumed to be dominated by the geological history of atmospheric oxygen (pO₂)^4,5. Here, by contrast, we show by means of a series of Earth system model experiments how continental rearrangement during the Phanerozoic Eon drives profound variations in ocean oxygenation and induces a fundamental decoupling in time between upper-ocean and benthic [O₂]. We further identify the presence of state transitions in the global ocean circulation, which lead to extensive deep-ocean anoxia developing in the early Phanerozoic even under modern pO₂. Our finding that ocean oxygenation oscillates over stable thousand-year (kyr) periods also provides a causal mechanism that might explain elevated rates of metazoan radiation and extinction during the early Palaeozoic Era⁶. The absence, in our modelling, of any simple correlation between global climate and ocean ventilation, and the occurrence of profound variations in ocean oxygenation independent of atmospheric pO₂, presents a challenge to the interpretation of marine redox proxies, but also points to a hitherto unrecognized role for continental configuration in the evolution of the biosphere.

^{海洋动物的早期进化和大部分灭绝历史被认为是由海洋1,2,3}中溶解氧浓度 ([O ₂ ])的变化驱动的。反过来，人们普遍认为 [O ₂ ] 主要受大气中氧气 ( p O ₂ ) ^4,5的地质历史影响。相比之下，在这里，我们通过一系列地球系统模型实验展示了显生宙期间的大陆重排如何推动海洋氧合的深刻变化，并导致上层海洋和底栖生物之间在时间上发生根本性脱钩 [O ₂]。我们进一步确定了全球海洋环流中状态转变的存在，这导致了显生宙早期甚至在现代p O ₂下也出现了广泛的深海缺氧。我们发现海洋氧合在稳定的千年 (kyr) 周期内振荡也提供了一种因果机制，可以解释早期古生代⁶后生动物辐射和灭绝率升高的原因。在我们的模型中，全球气候和海洋通风之间没有任何简单的相关性，并且海洋氧合作用的发生与大气p O _2无关，对海洋氧化还原代理的解释提出了挑战，但也指出了迄今为止大陆配置在生物圈演化中的未被认识的作用。