The Southern Apennines case history: thermal constraints and reconstruction of tectonic and sedimentary burials

The reconstruction of the thermal history of folded and thrust units is crucial to define the pattern of tectonic loading and the time-space evolution of an orogen where tectonic exhumation processes occurred at shallow crustal levels. In the present study, the combined use of different thermal indicators in diagenesis allowed the reconstruction of the thermal maturity in the axial zone of the southern Apennines. Our major results include: (i) the documentation of a break in thermal maturity from the Apenninic Platform derived tectonic unit (from immature to early mature stages of hydrocarbon generation) to the Lagonegro Basin derived tectonic units (late diagenetic stage). This jump may be attributed to different amounts of tectonic loading that were emplaced on top of the different stratigraphic-structural units during Neogene chain building; (ii) the documentation, within the Lagonegro units, of along-strike variations of thermal maturity (thus maximum burial temperatures). This can be related to changes in the amount of tectonic burial associated with lateral variations of thrust sheet thickness; (iii) the recognition of different ages of exhumation characterizing the southern and northern sectors of the study area. In the southern sector exhumation is younger, and post-dates the emplacement of the allochthonous units onto the Apulian Platform carbonates (here in the late mature stage of hydrocarbon generation) exposed in the Mt. Alpi area. The latter is interpreted as a sector of localized, intense exhumation within the orogenic chain. In the northern sector, exhumation is older, thus an independent tectonic evolution of the allochthonous units appears to have occurred prior to their final emplacement in the present position on top of the buried Apulian Platform carbonates.