The degree of detachment within the continental crust during collisional deformation has been widely debated for many years. Two extreme models can be applied to the interpretation of thrust belts; one states that the sedimentary cover is detached from the underlying basement along fault planes with ramp-flat geometries (thin-skinned model). The alternative one states that the basement is also involved in the deformation along crustal-scale ramps (thick-skinned tectonic model).
Recent research from the northern Apennines has shown that thick-skinned tectonic interpretations can readily be applied to the external part of the thrust belt. For example according to some Authors the inversion reinterpretation of the Marche area requires five times less shortening than the alternative and more traditional thin-skinned model. However, inversion interpretations cannot universally be applied to the Apennines. A thin-skinned model still fits well for example for the Bologna-Modena sector in the Northern Apennines. Furthermore well data in the southern Apennines clearly demonstrate the presence of allochthonous thrust sheets transported for several tens of kilometers over largely autochthonous Apulian platform carbonates, and this configuration forms an important hydrocarbon play in this region. The buried Apulian carbonates (6-8 km thick) are deformed by relatively low-displacement, high-angle reverse faults involving the basement. Therefore in the Southern Apennines, a switch from thin-skinned to thick-skinned thrusting appears to have occurred as the Apulian carbonates — and the underlying thick continental lithosphere — were deformed. The Central Apennines sector lies between these two main segments of the orogen and its structural style contains elements of both thin-skinned thrusting and thick-skinned inversion.
Thermal and thermo-chronological data from Mesozoic and Tertiary sequences cropping out in key areas of the Apennines — from the Northern segment to Sicily — have been established in order to provide an independent constraint to its structural style and Neogene-Quaternary orogenic evolution. Thermal data were obtained through organic matter optical analyses, X-ray diffraction of clay mineral assemblages and fluid-inclusions micro-thermometry. Thermo-chronological constraints derive from apatite fission tracks and U-Th/He analyses.
The integration of thermal and thermochronometric data with structural and morphotectonic features allowed us to trace the interplay between thin- and thick skinned structural styles and define modes and times of exhumation of the chain in the light of the interaction between the role of gravity-driven processes and thrust tectonics.