Atmosphere–ocean oxygen and productivity dynamics during early animal radiations

Significance We have discovered 2 major oceanic anoxic events (OAEs) in the early Cambrian at the time when animals markedly diversified. We present a multiproxy constraint on the global biogeochemical cycles to show that these events, in contrast to most younger OAEs, could have been driven by declining atmospheric O 2 levels, plausibly set off by the appearance of bioturbating animals. Pulses of animal appearances may have occurred at different times on different continents, but the last pulse occurred after the OAEs and at a time when we predict higher marine productivity and O 2 levels in the surface oceans suggesting energy supply into the marine food chain was maximal.