True and Apparent Polar Wander From Sluggish to Active Lid Tectonics

Abstract

It has been proposed that to satisfy a wide range of geological observations, early Earth mantle convection operated in “sluggish-lid” tectonics before transitioning to modern-day, “active-lid” tectonics. The former is the result of a weaker asthenosphere relative to the latter and manifests itself in a partially decoupled plate-mantle system. This transition is required to produce reasonable apparent polar wander (APW) plate velocities over Earth history. Since these tectonic regimes are dictated by the thermo-mechanical structure of the mantle, they should also influence true polar wander (TPW). Here, we explore the relative importance of TPW within a mantle that transitions from sluggish-to active-lid tectonics to provide some context on how to interpret paleomagnetic observations over Earth history. We find that TPW rates are faster when Earth's mantle operates in sluggish-lid tectonics than active-lid, contrary to previous results that appear to only be appropriate for active-lid TPW. We also find that if subduction initiated during sluggish-lid tectonics, this could also lead to high, intermittent rates of TPW.