Linking thrust system, back-arc extension, rift inheritance, and crustal delamination in the Tyrrhenian basin–Apennines thrust belt system.

In this contribution, we present a kinematic reconstruction for the Tyrrhenian back-arc basin–central Apennines fold-and-thrust belt system during the last 25 Myr, illustrating how its evolution is driven by the interplay between slab rollback and the inherited rifted margin architecture of the lower plate.

After an initial stage of oceanic subduction and slab rollback, which led to the formation of the Liguro-Provençal back-arc basin and the development of the thin-skinned Liguride accretionary wedge, soft collision was established around 20 Ma with the arrival of Adria’s rifted margin at the subduction zone. The transition from subduction to soft collision altered the orogenic system’s dynamics, decelerating slab rollback and slowing down the velocity of thrust migration. By 12–10 Ma, with the hard collision stage already established, the subduction interface migrated from the base of the sedimentary cover into the ductile middle crust, coevally with the onset of lower crust delamination, the renewal of slab rollback, the acceleration of forelandward thrust propagation, and the onset of back-arc extension in the axial zone of the belt. Since then, extensional and compressional deformation are migrating toward the foreland at a constant velocity. We propose a "zip-like" tectonic model for the Apennines over the last 10 Myr, in which delamination of the lower crust spreads from a forelandward-migrating singularity point. Areas of compression and extension are pinned to this migrating singularity point, providing a unified explanation for the seismicity patterns, low-angle normal faults, and Moho depth variations observed in the Apennines.