Reviewing chronostratigraphic uncertainty of the Ediacaran-Cambrian transition

Fred Toby Bowyer, Lyle Nelson

The Ediacaran-Cambrian transition archives the widespread disappearance of ‘Ediacaran-type’ soft-bodied biota and the appearance of most modern animal body plans, including a major diversification of skeletal animals and styles of animal-substrate interaction. Despite over a century of study, our ability to confidently reconstruct the series of macroevolutionary events that inform origination and extinction rates across the Ediacaran-Cambrian transition is challenged by underlying ambiguity in global stratigraphic correlation. Here, we review the chronology of events recorded by the successions that are currently the most temporally well-constrained, discuss major uncertainties, and use this perspective to reconstruct plausible global age frameworks for published biostratigraphic and chemostratigraphic data. Current models support minor temporal overlap of classically Ediacaran and Cambrian calcified animal fossils, aid assessments of eustatic sea-level and drivers of carbon isotope instability, contextualize regional datasets, and highlight the approaches required for further refinement. While there remains ~5 million years of uncertainty, holistic evaluation of existing chronostratigraphy suggests that the GSSP for the Ediacaran-Cambrian boundary falls between 538 and 533 Ma.