From continental subduction to contintenal collision: geological, geophysical and thermochronometric constraints from the southern Apennines (Italy)

Integrated geological data sets from the southern Apennines indicate that Miocene subduction of the distal part of the Adriatic continental margin followed that of Neotethyan oceanic lithosphere without significant breaks in the accretion process. Subsurface data point out that the Apennine accretionary wedge forms an allochthon overlying carbonate platform strata (Apulian Platform) continuous with those exposed in the foreland. Buttressing of the accretionary wedge against the western margin of the Apulian Platform, wedge uplift and final emplacement on top of the Apulian carbonates are marked by vigorous exhumation recorded by apatite fission track data (cooling ages clustering around 5.5 Ma). The tectonically buried portion of the Apulian Platform was involved in the final shortening phases, giving rise to reverse-fault-related, open, long-wavelength folds forming hydrocarbon traps. Geophysical data provide evidence that deep-seated reverse faulting involves the basement, while interpretation of high-quality seismic profiles, cross-section balancing and restoration of the buried Apulian carbonates favour an inversion tectonics model involving reactivation of pre-existing basement normal faults, the related deformation being characterized by limited horizontal displacements. Therefore, a switch from thin-skinned thrusting to thick-skinned inversion appears to have occurred in the southern Apennines at the transition form continental subduction to true collisional stages.