Episodic back-arc extension during restricted mantle convection in the Central Mediterranean

In the Central Mediterranean, during the last 80 Myr Africa has been slowly converging toward Eurasia, with an average relative velocity of less than 1 cm yr-1. For 50 Myr this slow convergence led to the build-up of the Alpine orogenic belt and to the initiation of consumption of the former Tethys ocean; in the last 30 Myr, however, the whole Central-Western Mediterranean has been swept by rapid episodes of trench migration (up to 6 cm yr-1) and back-arc opening, which consumed the whole former Tethys ocean. We combine plate tectonic history, geological timing, and laboratory modelling to reconstruct the subduction history and the evolution of the Central Mediterranean over the last 80 Myr. We find that the dynamic evolution of the subducting oceanic lithosphere can reconcile the rapid, episodic back-arc migration with the slow African convergence, but only if the subduction process is restricted to the upper mantle.