PhD: The origin of animals: Building a precise timeline from the geological record

The Ediacaran–Cambrian transition saw the evolutionary appearance of complex macroscopic life and animal-dominated ecosystems. Yet, basic questions on the timing and sequence of evolutionary events during that period remain unresolved, due to the challenge of correlating a geological record that straddles multiple continents. Signatures of ocean chemistry, such as stable carbon isotopes (δ13C), in principle allow for the correlation of fossil-bearing sedimentary sections from different locations. However, such chemostratigraphic signals are typically aligned by visual inspection, and may not exclusively represent a global oceanic signature. As such, this inherently subjective approach often produces multiple possible alignments, and gives no rigorous way of determining the most likely alignment, or quantifying uncertainty.

This project will use the StratoBayes correlation software to produce an objective stratigraphic framework of late Ediacaran–early Cambrian deposits, which will provide a definitive timeline of early animal evolution at an unprecedented temporal resolution. StratoBayes is a novel tool developed by members of the supervisory team; it uses innovative Bayesian models to derive correlations between stratigraphic sections based on the geochemical signatures they record.

Starting from our existing compendium of Cambrian data, the successful student will compile a database of geochemical signals from the upper Ediacaran period. These data will be combined with new high resolution geochemical and radioisotopic data from Namibian cores obtained from the international GRIND drilling project (co-led by Rose), which offer a continuous and pristine record through the upper Ediacaran. StratoBayes will allow stratigraphic data to be combined across different palaeocontinents within a Bayesian framework, yielding precise dates (and associated uncertainties) for poorly constrained fossil sites and clarifying the sequence of the key evolutionary events that set the stage for complex animal ecosystems. Evaluating candidate index fossils and constraining Ediacaran–Cambrian stratigraphy will enable evolutionary research to resolve fundamental questions, such as whether early animal evolution was concentrated in one or multiple bursts; and inform how environmental changes served as triggers for, or were consequences, of animal evolution.