Conclusion
Data about maximum burial and exhumation history from key areas of the Apennines and North-eastern Sicily are presented in this paper through maps based on an ArcGIS database, providing information on paleo-thermal and thermochronological constraints derived from organic matter optical analyses, X-ray diffraction of clay-rich sediments, fission tracks and (U-Th)/He dating.
In synthesis, main results concerning the single areas may be summarised as follows:
In the Northern Apennines, burial conditions (mainly detected through organic matter analyses) and timing of exhumation (through a huge dataset of thermochronological data) progressively decrease eastwards from the inner toward the outer zones and through the nappes from the lowermost to the uppermost unit. Apart from large outcrops of metamorphic rocks well exposed in Tuscany, most of the rocks of the Northern Apennines reached only diagenetic conditions.
In the Central Apennines, organic matter analysis and X-ray diffraction of clay-rich sediments are mainly provided for both pre-orogenic and syn-orogenic successions with subordinate apatite fission tracks data in the external zones. Low levels of diagenesis are recorded for both Meso-Cenozoic carbonate hanging-walls and siliciclastic footwalls of regional thrust sheets in the stage of immature to early mature stages of hydrocarbon generation. These results suggest a thick-skinned compressive style prevailing on thin-skinned style with strong influence of pre-existing paleogeography on thrust localisation and geometries that enhanced scarce tectonic loading during Upper Miocene-Lower Pliocene chain building.
In the Southern Apennines, both thermal and thermochronological data are available mainly for the axial portion of the chain comprising the outcropping tectonic units derived from the Apenninic Platform, the Mesozoic portion of the Lagonegro basin and the Apulia Platform.
Main novelties concern the detection of a jump in thermal maturity between the Apenninic Platform (shallow burial of tectonic origin in Basilicata with an along strike increase of tectonic loads toward the South at the Calabria-Basilicata border) and the outcropping Lagonegro basin-Apulian carbonate Platform (deep burial of tectonic origin locally exceeding 4 km). Data distribution suggests a switch from thin-skinned (Miocene) to thick-skinned (Pliocene-Quaternary) compressive tectonics as a result of influence in paleogeography at the passive margin scale coupled with the buttressing of the allochthonous wedge against the Apulia Carbonate platform margin. Exhumation of the Lagonegro derived units due to gravitational collapse through extensional detachments in the axial zone may be kinematically linked to severe shortening in the external portions of the chain.
In North-eastern Sicily, localised exhumation different in time and amounts develops in a general trend of decreasing thermal maturity from hinterland to foreland with the lowest values for syn-orogenic siliciclastics (mainly thrust-top basins). Compressive reactivation at the rear of the chain with creation of a few kilometres tectonic burial and subsequent exhumation since Serravallian times due to extension is also suggested in the Peloritani Mts. Accretionary prism made up of Sub-ligurian unit (namely Sicilidi) in the footwall of the Peloritani Mts. mainly exhumed in Burdigalian times (17-19 Ma) from depths of a few kilometers due to erosion, gravitational collapse and backthrusting. Frontal thrust stack derived from late deformation of Mesozoic passive margin successions mainly exhumed in Tortonian-Pliocene times from depths of about three kilometers.
Data from the crystalline units of Calabria manly concerning thermochronology are still too scarce to draw a burial-exhumation evolutionary scenario.