Quantitative comparison of geological data and model simulations constrains early Cambrian geography and climate

Marine ecosystems with a diverse range of animal groups became established during the early Cambrian (~541 to ~509 Ma). However, Earth’s environmental parameters and palaeogeography in this interval of major macro-evolutionary change remain poorly constrained. Here, we test contrasting hypotheses of continental configuration and climate that have profound implications for interpreting Cambrian environmental proxies. We integrate general circulation models and geological observations to test three variants of the ‘Antarctocentric’ paradigm, with a southern polar continent, and an ‘equatorial’ configuration that lacks polar continents. This quantitative framework can be applied to other deep-time intervals when environmental proxy data are scarce. Our results show that the Antarctocentric palaeogeographic paradigm can reconcile geological data and simulated Cambrian climate. Our analyses indicate a greenhouse climate during the Cambrian animal radiation, with mean annual sea-surface temperatures between ~9 °C to ~19 °C and ~30 °C to ~38 °C for polar and tropical palaeolatitudes, respectively. There is a lot of uncertainty about what Earth’s climate and geography were like in the early Cambrian, when animal life diversified throughout the oceans. Here we show that numeric comparisons of model simulations and climatically influenced rocks can help constrain geography and climate during this time.