Ediacaran coupling of climate and biosphere dynamics

Abstract

Climate change is demonstrably linked to radiations, extinctions, and turnovers in the biosphere throughout the Phanerozoic (538.8 Ma to present). Here, we suggest this connection existed as early as the late Ediacaran (~579 to 538.8 Ma), the first interval in Earth’s history to host complex macroscopic organisms including early animals. We systematically evaluate the dating, correlation, and likely glaciogenicity of candidate Ediacaran glaciogenic deposits to produce a first-order climatic framework for the middle to late Ediacaran. In contrast to previous studies, we account for uncertainties in chronostratigraphy, correlation, and depositional interpretation of candidate glaciogenic deposits and thereby reduce the error envelopes that supported previous interpretations of either one long (>20 Myr) or up to four short (1 to 5 Myr) icehouse intervals. Despite large uncertainties regarding the precise ages of many late Ediacaran deposits, we show that the most parsimonious explanation of available data identifies two intervals of icehouse climate (mid-Ediacaran, ~593 to 579 Ma; and late Ediacaran, ~565 to ~550 Ma) that alternated with greenhouse climates (late Ediacaran, ~579 to 565 Ma; and terminal Ediacaran, ~550 Ma to Cambrian). Sedimentological data suggest that both icehouse intervals were characterized by geographically restricted glaciations with repeated expansion and contraction of ice sheets. The changes in climate state we propose are contemporaneous with turnovers in the late Ediacaran biosphere. Further data collection is required to test our climate framework, but current evidence supports a Phanerozoic-style coupling of global climate and biosphere during the early stages of animal evolution.