Reactivation of the Alpine Nappe Stack During the Late‐Orogenic Collapse of the Peloponnese (Greece)

Abstract Using new morpho‐structural observations from field studies and digital terrain analysis, combined with a reinterpretation of literature data, we reassess the role of late‐orogenic collapse in shaping the present‐day morphology of the Peloponnese (Greece). Located in the External Hellenides, the region was primarily structured by the stacking of alpine tectonic nappes since the Paleogene. From the Miocene onward, the underplating of crustal slivers progressively thickened the crust, leading to the exhumation of deep units and the formation of turtle‐back domes within the nappe pile. This uplift triggered the gravitational collapse of the superficial units along low‐angle normal faults and toe thrusts, which reactivated alpine décollements. These detachments, widespread along the periphery of exhumation domes, indicate multi‐directional upper‐wedge collapse, though partially controlled by the geometry of the wedge. In the central Peloponnese, superficial nappes were delaminated, forming large tectonic windows that exposed deeper units, while detached material accumulated at the base of the domes. Since the Pliocene, due to oceanic slab rollback resumption, major normal faults have overprinted these syn‐ and late‐orogenic structures, shaping the characteristic “four‐fingers” morphology of the Peloponnese. The presence of a free boundary at the Matapan Trough, the WNW‐striking alpine structural inheritance and the late‐orogenic exhumation domes largely influenced the location and southwestward direction of this post‐orogenic extension.