The Pannotia Conundrum

Once widely accepted, the existence of Pannotia as an Ediacaran supercontinent has come into question. In the context of the supercontinent cycle, this development is of fundamental importance since the existence (or not) of Pannotia is central to the nature, duration and evolution of the cycle, and dictates the cycle's geodynamic pathway from the breakup of Rodinia to the amalgamation of Pangaea. Contributing to the growing skepticism in Pannotia, geochronology suggests the putative landmass had begun to break up before it was fully assembled, paleomagnetic data for the Ediacaran are notoriously equivocal, and the proxy signals of Ediacaran-Cambrian supercontinent amalgamation and breakup, although collectively compelling, can be individually challenged. Efforts to detect the mantle legacy expected of supercontinent tenure, however, support large-scale mantle upwelling in the wake of Pannotia amalgamation. Hence, whether or not it was a supercontinent, its assembly appears to have influenced global mantle convection patterns in a manner consistent with one. This raises the question of whether a full-scale supercontinent is needed as a geodynamic driver of the supercontinent cycle and, if not, whether other such turnovers in mantle convection are manifest in the geologic record, and whether the cycle more accurately reflects cycles in mantle convection.