Rise of metazoan ecosystem complexity in the early Cambrian has been hypothesized to link with enhanced oceanic oxygenation and nutrient availability. However, despite extensive empirical datasets, quantitative assessments that mechanistically link environmental perturbations to biological innovations remain scarce. By integrating newly generated iron-phosphorus data from three shallow-water sections with published contemporaneous records, here we reconstruct the spatiotemporal evolution of paleoredox and nutrient dynamics across the Yangtze Platform spanning Cambrian Stages 2–3 (ca. 522–514 Ma). Integration of these data into the SCION Earth Evolution model indicates that although the basin-scale eutrophication induced form phosphorus recycling transiently amplifies marine anoxia during late Stage 2, net oxygen release from enhanced organic carbon burial ultimately oxygenated the deep ocean on broader spatial and temporal scales, providing the essential environmental impetus for Earth’s first major diversification of animal phyla.