In the southern Apennines fold-and-thrust belt, thermal indicators record exhumation of sedimentary units from depths locally in excess of 5 km. The thrust belt is made of allochthonous sedimentary units that overlie a 6-8-km-thick, carbonate footwall succession. The latter, continuous with the foreland Apulian Platform, 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 thick continental lithosphere-were deformed during the latest shortening stages. Apatite fi ssion track data, showing 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, based on cross-section balancing and restoration, 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 are interpreted to have played a primary role in tectonic exhumation.

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MonteAlpi represents the only area of the southern Apennines where Apulian carbonates, elsewhere buried beneath a several-km thick allochthon, are exposed at the surface. These rocks also represent the reservoir interval in southern Italy’s major oil fields. The tectonic evolution of this substantially exhumed area of the fold-and-thrust belt, derived from conventional structural and stratigraphic considerations via integration into the regional framework, has been tested and detailed by the analysis of vitrinite reflectance, clay mineralogy, apatite fission track, and fluid inclusion data. The Apulian carbonates of Monte Alpi underwent significant tectonic burial as a result of thin-skinned thrusting in early Pliocene times. Simplified burial and thermal modeling suggests that the thickness of allochthonous material emplaced on top of Monte Alpi was probably in excess of 5 km. Exhumation is envisaged to have started in the late Pliocene, when the area emerged and the tectonic load started to be eroded off Monte Alpi. A significant stage of exhumation is inferred to have taken place in uppermost Pliocene-early Pleistocene times as a result of thick-skinned reverse faulting at depth and coeval thin-skinned extension within the overlying allochthon. After shortening ceased throughout the whole southern Apennines, middle Pleistocene-Holocene tectonic exhumation of Monte Alpi was essentially controlled by thick-skinned extensional tectonics. This process is still active and controls the present-day seismicity of the study area

Temperature-dependent clay-mineral as semblages, vitrinite refl ectance, and apatite fi ssiontrack data have been used to investigate levels of diagenesis and time of exhumation of the double-verging Sicilide-Antisicilide accretionary wedge in Eastern Sicily. The integration of organic and inorganic thermal indicators allowed us to distinguish parts of the accretionary wedge with different thermal signature and evolution. We recognize a warmer core made up of the Mount Soro and Troina units and two colder rims (Antisicilide and far-traveled Sicilide units). The Antisicilide unit was thrust back toward the hinterland, and the far-traveled Sicilide units were gravity-driven toward the Hyblean Plateau.In detail, the highest percentages of vitrinite refl ectance (VR o ) values (0.60%-0.96%) and percentages of illite layers in illite-smectite (I-S; 60%-85%) are found in the Mount Soro and Troina units. Apatite fi ssion-track data, together with the paleotemperature estimates from vitrinite-refl ectance data and clay-mineral-based geothermometers, indicate that fi ssion tracks were partially to totally annealed during wedge accretion and that the subsequent exhumation occurred mainly in Burdigalian times.Low VR o values (0.35%-0.50%) and percentages of illite layers in I-S (30%-60%) occur in early thrust-top deposits (Reitano Flysch) that unconformably overlie the Sicilide Complex, as well as the far-traveled Sicilide and Antisicilide units. Apatite fi ssion-track data for the Antisicilide unit confi rm low paleotemperature values. Thus the far-traveled Sicilide and Antisicilide units were probably at higher structural levels in the original accretionary prism and were remobilized since late Aquitanian-Burdigalian times.