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

Thomas W Wong Hearing,Thomas H P Harvey,Thijs R A Vandenbroucke,Mark Williams,Christopher R Scotese,Alexandre Pohl,Yannick Donnadieu,Alain Franc,Pierre Sepulchre

doi:10.1038/s41467-021-24141-5

Abstract

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.

Highlights

Marine ecosystems with a diverse range of animal groups became established during the early Cambrian (~541 to ~509 Ma)
The Fast Ocean Atmosphere Model (FOAM) general circulation model (GCM) is frequently applied in deeptime palaeoclimate studies[42,43,44,45], and is well-suited to our purpose because its high throughput means that it can be used to produce the large number of simulations needed to test the wide range of boundary conditions plausible for the early Cambrian
As with most earlier generation GCMs, FOAM has a relatively low equilibrium climate sensitivity and tends to simulate colder average temperatures for the same pCO2 forcing than most recent models used in the Coupled Model Intercomparison Project (CMIP)[46]

Summary

Introduction

Marine ecosystems with a diverse range of animal groups became established during the early Cambrian (~541 to ~509 Ma). 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. The spatial distributions of fossil plankton have been used to reconstruct early Palaeozoic climatic belts[10], but the limited development of planktic ecosystems in the early Cambrian hinders their use here[11] Sensitive lithologies, such as evaporitic, lateritic, and glaciogenic deposits, are another valuable source of ancient climate data and can provide greater temporal and palaeogeographic coverage than can geochemical proxy data. Accurate early Cambrian reconstructions of the configuration of Earth’s continents, typically derived from palaeomagnetic and palaeobiogeographic data, are required to compare geological data with climate model simulations. There is latitude for debate over the positions of even major continents in the early Cambrian, e.g. ref

Methods

Results

Conclusion