A Phanerozoic-style icehouse climate in the middle Ediacaran

Abstract. Geological evidence points to icehouse conditions during the Ediacaran Period (635 to 538.8 Ma) both before and during the emergence of animals in the fossil record. However, the temporal and spatial distributions of Ediacaran ice sheets are not well constrained due to uncertainties in palaeogeography, chronostratigraphy, and the depositional settings of candidate glaciogenic deposits. Here, we systematically evaluate the evidence for the depositional ages of candidate Ediacaran glaciogenic deposits and establish the likelihood that each deposit was formed by ice-driven processes using observation-driven weighting criteria. Our analysis supports the existence of discrete mid- and late Ediacaran icehouse intervals (MEIH and LEIH respectively), each followed by greenhouse conditions. Focussing on the older MEIH, we integrate our quality-controlled geological dataset with climate and ice sheet model simulations to characterise glacial conditions during this interval (~593 to 579 Ma), which encompasses the ‘Gaskiers glaciation’. Our results indicate that the MEIH was a Phanerozoic-style icehouse, with latitudinally-constrained and fluctuating ice sheets, marking a break from the preceding Cryogenian snowball Earth motif, and occurring before the first known appearance of animals in the fossil record. By mapping robustly identified glaciogenic deposits onto contrasting middle Ediacaran palaeogeographic reconstructions, we show how these deposits can be used to constrain hypotheses of Ediacaran continental configuration.