Oceanic anoxic events are geologically abrupt phases of extreme oxygen depletion in the oceans that disrupted marine ecosystems and brought about evolutionary turnover. Typically lasting ~1.5 million years, these events occurred frequently during the Mesozoic era, from about 183 to 85 million years ago, an interval associated with continental breakup and widespread large igneous province volcanism. One hypothesis suggests that anoxic events resulted from enhanced chemical weathering of Earth’s surface in a greenhouse world shaped by high volcanic carbon outgassing. Here we test this hypothesis using a combination of plate reconstructions, tectonic–geochemical analysis and global biogeochemical modelling. We show that enhanced weathering of mafic lithologies during continental breakup and nascent seafloor spreading can plausibly drive a succession of anoxic events. Weathering pulses collectively gave rise to substantial releases of the nutrient phosphorus to the oceans, stimulating biological primary production. This, in turn, enhanced organic carbon burial and caused widespread ocean deoxygenation on a scale sufficient to drive recurrent anoxia. This model complements volcanic outgassing-centred hypotheses for triggering these events by demonstrating well-quantified basaltic sources of phosphorus release during periods of intense weathering related to climate warmth. Our study highlights a close coupling between the solid Earth and biosphere during continental reorganization.

海洋缺氧事件是海洋中氧气极度消耗的地质突变阶段，它破坏了海洋生态系统并带来了进化更替。这些事件通常持续约 150 万年，经常发生在大约 183 至 8500 万年前的中生代，这一时期与大陆分裂和广泛的大型火成岩省火山活动有关。一种假设认为，缺氧事件是由于高火山碳排放形成的温室世界中地球表面化学风化加剧造成的。在这里，我们结合板块重建、构造地球化学分析和全球生物地球化学建模来检验这一假设。我们表明，在大陆破裂和新生海底扩张过程中，镁铁岩岩性的增强风化可能会导致一系列缺氧事件。风化脉冲共同导致营养物质磷大量释放到海洋中，刺激了生物初级生产。这反过来又增强了有机碳的埋藏，并导致大范围的海洋脱氧，其规模足以导致周期性缺氧。该模型通过证明在与气候变暖相关的强烈风化期间磷释放的充分量化的玄武岩来源，补充了以火山放气为中心的假设，以触发这些事件。我们的研究强调了大陆重组过程中固体地球与生物圈之间的紧密耦合。