Pangea Migration

We confirm the proposition of Le Pichon et al (2019, ) that Pangea was ringed by a hemispheric subduction girdle from its formation 400 Ma to its dispersal 100 Ma. We quantify the northward migration, that we attribute to True Polar Wander (TPW), of its axis of symmetry, between 400 and 150 Ma, from southern latitudes to the equatorial zone. The spatial stabilizing within the equatorial zone of the axis of symmetry in a fixed position with respect to the lower mantle was marked by alternating clockwise and counterclockwise oscillations between 250 and 100 Ma that we relate to tectonic events. A subduction girdle is predicted to set up lateral temperature gradients from the relatively warm sub-Pangean mantle to a cooler sub-oceanic mantle. Over time, this effect acts to destabilize the Pangea landmass and its associated subduction girdle. Quantitatively, a scaling theory for the stability of the subduction girdle against the mantle overturn constrains the maximum magnitude of sub-Pangean warming before breakup to be order 100 degrees C, consistent with constraints on the Pacific-Atlantic oceanic crustal thickness differences. Our predictions are in line with the recent analyses of the Jurassic-Cretaceous climate change and with the existing models for potential driving forces for a TPW oscillation of Pangea across the equator. The timing and intensity of the predicted sub-Pangean warming potentially contributed to the enigmatically large Siberian Traps and CAMP flood basalts at 250 Ma and 201 Ma, respectively.

Automated summary

This study confirms that Pangea was surrounded by a hemispheric subduction girdle from its formation to dispersal, and quantifies the northward migration of its symmetry axis. The article also predicts the destabilizing effect of warming on the Pangea landmass and subduction girdle, and its potential contribution to geological events such as the Siberian Traps and CAMP flood basalts.