Pliocene-quaternary thrusting, syn-orogenic extension and tectonic exhumation in the Southern Apennines (Italy): Insights from the Monte Alpi area

Monte Alpi 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 thickskinned extensional tectonics. This process is still active and controls the present-day seismicity of the study area.