Resolving the enigmatic Precambrian-Cambrian boundary event

PI Rachel Wood (University of Edinburgh) and additional team members.

Project description

The rise of animals (metazoans) is a seminal event in the history of life. The Cambrian Explosion, starting at ~541 Million years ago (Ma), marks the abrupt appearance of abundant and diverse metazoans in the fossil record . This revolutionary event follows immediately after the high-amplitude Basal Cambrian carbon isotope Excursion (the BACE, ~540-538 Ma), a long-known, but highly enigmatic, negative δ¹³C carbon cycle perturbation. There is no single stratigraphic section that allows an integrated study of δ¹³C, key fossil distributions, and absolute ages at the same site, and thus calibration of this profound evolutionary transition remains fragmented and uncertain.

Many key questions then remain: Is the BACE local or global, diagenetic or primary? What is the mechanistic explanation? And what role did the BACE play in the evolution of metazoans? We will constrain the timing of onset, duration, origin, and implications for the global C cycle of the BACE via a highly integrated, multi-disciplinary programme of novel analyses and modelling using unique, global, unweathered, core data.

This will allow us to test the overarching hypothesis that the BACE was a global, synchronous redox and phosphorus drawdown event that was the driver of the Cambrian Explosion. By distinguishing physical, extrinsic drivers we can address a fundamental and motivating question: what caused animals to evolve and radiate when they did? This unique dataset is likely to be transformative as it will resolve the key processes fundamental to the coupled evolution of the Earth System and the rise of complex life.

We have five main objectives:

To constrain the timing of onset, duration, and global nature of the BACE.
To understand the local redox and phosphorus dynamics of the BACE.
To constrain the origin and drivers of the BACE.
To quantitatively test hypotheses for the cause(s) of the BACE against our new multiproxy data.
To understand the evolutionary implications of the BACE.