The southern Apennines thrust belt is NE-directed and, except for the remnants of units from the Internal Zone (e.g., ophiolite-bearing Ligurian units) that occur on top of the thrust pile, it is composed entirely of Mesozoic and Cenozoic sedimentary rocks of the External Zone (e.g., Cello and Mazzoli, 1999; Patacca and Scandone, 2007). The Apulian promontory represents the orogenic foreland. Collectively, the Apulian foreland and the deformed strata of the Apennines represent a telescoped continental margin with complex sub-basins of different ages (e.g., Mostardini and Merlini, 1986; Sgrosso, 1998; Cello and Mazzoli, 1999, and references therein).
Large amounts of subsurface data, particularly oil wells, demonstrate large-scale thin-skinned thrusting in the shallow part of the southern Apennines. The thrust belt forms a displaced allochthon that has been carried onto a footwall of foreland strata essentially continuous with the Apulian platform (e.g., Mostardini and Merlini, 1986; Carbone et al., 1991; Mazzoli et al., 2000; Menardi Noguera and Rea, 2000; Butler et al., 2004; Fig. 6 cross section C). The detachment between the allochthon and the buried Apulian shallow-water carbonates is marked by a mélange zone up to several hundred meters thick. It consists mainly of intensely deformed and overpressured deepwater mudstones and siltstones of Miocene to Lower Pliocene age, including blocks of material derived from the overlying allochthon (Mazzoli et al., 2001; Butler et al., 2004; Shiner et al., 2004). Beneath the mélange zone, under a thin but variable thickness of Pliocene shales stratigraphically overlying the Mesozoic-Tertiary platform carbonates, the hinterland portion of the Apulian unit was involved in the final phases of compression (late Pliocene - early Pleistocene; e.g., Cello and Mazzoli, 1999, and references therein). This resulted in reverse-fault-related, open, long-wavelength, high-amplitude folds that form the hydrocarbon traps for the significant oil discoveries in this area (Shiner et al., 2004). All recent, geologically realistic interpretations based on subsurface data indicate that deep-seated thrusting within the Apulian carbonates is characterized by relatively limited horizontal displacements, and probably by involvement of the underlying basement (Mazzoli et al., 2000; Menardi Noguera and Rea, 2000; Speranza and Chiappini, 2002; Butler et al., 2004; Shiner et al., 2004). Therefore, during the late Pliocene, a switch from thin-skinned to thick-skinned thrusting appears to have occurred in the southern Apennines as the Apulian carbonates - and the underlying thick continental lithosphere - were involved in deformation (Mazzoli et al., 2000; Butler et al., 2004).
Neogene thrusting in the Calabrian Arc and in the southern Apennines was accompanied by back-arc extension and sea-floor spreading in the southern Tyrrhenian Sea (e.g., Kastens et al., 1988; Faccenna et al., 1996, 1997, and references therein; Mattei et al., 1999). Around the early-middle Pleistocene boundary (ca. 0.8 Ma B.P.), however, SW-NE-directed shortening ceased in the frontal parts of the southern Apennines, too. A new tectonic regime established itself in the chain and adjacent foothills (e.g., Cello et al., 1982; Cinque et al., 1993; Montone et al., 1999). The structures related to this new regime, characterized by a NE-SW oriented maximum extension, consist of extensional and transcurrent faults that postdate and dissect the thrust belt (e.g., Cello et al., 1982; Butler et al., 2004).