Structural, morphotectonic and thermo-chronological constraints to the Late Miocene-Quaternary tectonic evolution and exhumation in the southern Apennines (Italy)

In the southern Apennines fold and thrust belt, thermal indicators record exhumation of sedimentary units from depths locally in excess of 5 km. The belt is made of allochthonous sedimentary units that overly a 6 8 km thick, carbonate footwall succession. The latter is deformed by reverse faults involving the underlying basement. Therefore, a switch from thin-skinned to thick-skinned thrusting occurred as the Apulian Platform carbonates - and the underlying continental lithosphere - were deformed during the latest shortening stages. Apatite fission track data, with cooling ages ranging between 9.2 ± 1.0 and 1.5 ± 0.8 Ma, indicate that exhumation marks these late tectonic stages, probably initiating with the buttressing of the allochthonous wedge against the western margin of the Apulian Platform. Pliocene-Pleistocene foreland advancing of the allochthonous units exceeds the total amount of slip that could be transferred to the base of the allochthon from the underlying thick-skinned structures. This suggests that emplacement of the allochthon above the western portion of the Apulian Platform carbonates was followed by gravitational readjustments within the allochthonous wedge, coeval - and partly associated with - thick-skinned shortening at depth. The related denudation processes have played a primary role in tectonic exhumation.