Untangling Ediacaran Paleomagnetism to Contextualize Immense Global Change

The Ediacaran-early Cambrian (~635-520 Ma) was an interval of immense global change with fundamental state shifts occurring in the bio-cryo- and atmosphere. Such changes included the abrupt appearance and rapid diversification of modern metazoan life (the Ediacaran fauna and Cambrian ‘explosion’), the end of protracted, global-scale glaciations (Snowball Earth), the rise of atmospheric oxygen to present-day levels, and the perturbation of carbon isotopic records to extremes otherwise unknown to Earth history. Given the immensity and abruptness of those changes, they are clearly essential to an understanding of the development of life, the history of climatic change and the evolution of the oxygen and carbon cycles. Accordingly, great effort has been dedicated to acquiring detailed temporal records to investigate those changes through time, but we still lack a robust paleogeographic framework to study them in space. This is because paleomagnetic data—which are used to determine the ancient positions of continents—exhibit aberrant behaviour at this time, the meaning of which is unknown. Four alternative hypotheses have been formulated to explain them: 1) rapid rotations of the entire solid Earth (true polar wander), 2) an unstable magnetic field, 3) pervasive data corruption, or 4) ultra-fast plate motion. Each of these hypotheses has far-reaching implications: Hypotheses 1, 2 & 4 reflect dramatic non-uniformitarian processes that would defy our understanding of geodynamics, whereas hypothesis 3 poses grave challenges to the interpretation of paleomagnetic data in Precambrian time. My vision with EPIC is to investigate and identify the origin(s) of the aberrant paleomagnetic data of this age, and to use that knowledge to directly reconstruct Ediacaran-early Cambrian paleogeography for the first time. EPIC will thus transform one of geophysics’ most outstanding enigmas into one of our greatest assets in understanding this critical time in Earth’s development.