The emergence and diversification of early animals is commonly thought to have coincided with atmosphere and ocean oxygenation across the terminal Neoproterozoic and early Paleozoic, during which oxygen levels on Earth’s surface were sufficient to support the metabolism of early multicellular metazoans in the ocean. Although surface oxygen levels are likely to have broadly risen through the Paleozoic, ocean oxygenation levels during this period are still disputed and poorly constrained. While the community is actively developing high time-resolution records of redox proxies in marine sediments, uncertainties remain about how these records can be used to reconstruct the global marine redox landscape. In this review, we compile newly published molybdenum and uranium isotope data from the late Neoproterozoic to the early Paleozoic (ca. 680–480 Ma) to provide an updated look at the secular changes in global ocean redox state and the potential drivers of these shifts. Integrations of Mo and U isotope records suggest a gradual transition from a pervasive anoxic condition to a highly dynamic condition for global marine redox state from the late Neoproterozoic to the Cambrian. We further concentrate on the marine redox landscape of early Cambrian, by comparing the carbon, sulfur, nitrogen and uranium isotope records and reproducing the variations in carbon-sulfur-uranium isotope records with biogeochemical box models. Changes in marine primary productivity under a relatively low atmospheric oxygen level, are proposed to play a first-order control on the early Cambrian ocean redox dynamics.

人们普遍认为，早期动物的出现和多样化与新元古代末期和古生代末期的大气和海洋氧合同时发生，在此期间，地球表面的氧气水平足以支持海洋中早期多细胞后生动物的代谢。尽管通过古生代，地表氧水平可能已普遍上升，但在此期间海洋的氧合水平仍存在争议，且约束较弱。在社区积极开发海洋沉积物中氧化还原代理的高时间分辨率记录的同时，如何使用这些记录来重建全球海洋氧化还原景观仍存在不确定性。在本综述中，我们汇总了新元古代晚期至古生代早期的新出版的钼和铀同位素数据（ca. 680–480 Ma）以提供全球海洋氧化还原状态的长期变化以及这些变化的潜在驱动因素的最新信息。钼和铀同位素记录的整合表明，从晚期新元古代到寒武纪，全球海洋氧化还原状态从普遍的缺氧条件到高动态条件逐渐过渡。通过比较碳，硫，氮和铀同位素记录，并利用生物地球化学盒模型再现碳硫铀铀记录的变化，我们进一步关注寒武纪早期的海洋氧化还原景观。建议在相对较低的大气氧气水平下改变海洋初级生产力，以对寒武纪早期海洋氧化还原动力学起一阶控制作用。