The enduring Ediacaran paleomagnetic enigma

Abstract

The Ediacaran Period was an interval of significant global transformation, marked by major changes in the biosphere, cryosphere, hydrosphere and atmosphere, and possibly the solid Earth. A better understanding of this interval is thus important to an understanding of the diversification of complex life, the history of long-term climatic change and the evolution of global geochemical cycles. Increasingly detailed temporal records are being acquired from Ediacaran rocks to investigate these changes in time, but we still lack a robust paleogeographic framework to study them in space. Paleomagnetic data—which are used to quantitatively determine the ancient position of continents—appear unusually complex and often contradictory throughout this period. The nature of these complex data remains elusive and four distinct hypotheses have been forwarded to explain them: 1) the tectonic plates were moving especially fast, 2) many of the paleomagnetic data have been corrupted in some as-yet unrecognized way, 3) the solid Earth underwent rapid bouts of true polar wander, or 4) the magnetic field was behaving abnormally. Each of these hypotheses have far-reaching implications. Hypotheses 1, 3 and 4 reflect processes which differ dramatically from their present-day counterparts and defy prevailing paradigms of secular change, whereas hypothesis 2 raises questions about the reliability of existing paleomagnetic interpretations and their paleogeographic derivatives. Significant advances will be garnered through resolution of this enigma, but its endurance reflects its intricacy, and any solution is going to require a collective effort. With the aim to stimulate additional community efforts toward solving it, we probe these multiple working hypotheses, elaborate how they may be further tested and discuss the implications of their possible validation.