True Polar Wander: A Key Indicator for Plate Configuration and Mantle Convection During the Late Neoproterozoic

Abstract

AbstractLarge polar motions are observed in the apparent polar wander paths of several continents during the Ediacaran. Among various hypotheses proposed in the literature, one consists of the occurrence of two successive fast and large true polar wander (TPW) episodes, from 615 to 590 Ma and then between 575 and 565 Ma. In this study, we explored the effect of the reactivation of a girdle of subduction to produce such TPW. First, we performed a reconstruction of the main continents between 615 and 520 Ma including Laurentia, Baltica, west and central Gondwana, and Australia‐Antarctica. We then implemented this paleogeography into a simple mantle dynamic model to calculate the TPW during the Ediacaran. Our results show that the reactivation of a girdle of subduction surrounding the continents along with a reduced effect of the return flow rising from the lower mantle can produce two TPW episodes consistent with the paleomagnetic observations. This mechanism is possible if the sinking velocities associated with the girdle of subduction drastically decrease between 635 and 730 Ma. Such a large geodynamic event is consistent with the detrital zircon age distribution of the Neoproterozoic supporting a low subduction activity during the Cryogenian and a boost during the Ediacaran. Decrease of subduction‐related stress induced on the lithosphere may have interrupted the rifting of the supercontinent Rodinia for 100 Ma. Finally, the weakening in subduction magmatism might have strongly reduced the CO2 flux into the atmosphere and played a major role in driving the Neoproterozoic global‐scale glaciations.