Alpine compressional tectonics in the Southern Alps. Relationships with the N-Apennines

The southern Alps orogenic development has been produced by non-cylindrical accretion of arcuated thrust belts. The western-northern sector of the chain is occupied by the Orobic Arc, an Eoalpine to Mesoalpine structural system including the Grigna and Presolana overthrusts. The radiometric age of the dykes cutting the overthrusting contacts suggests Late Cretaceous as the age of the principal tectonic emplacement. Apart from the Dinaridic influence in the eastern sector, the remaining parts of the Southern Alps were deformed mainly by the Oligo-Miocene, Miocene and Pio-Pleistocene events. The Chattian to Burdigalian tectonic phase (mainly Aquitanian in age) produced the backthrust system during the Gonfolite l.s. sedimentation. This WNW-trending compressions] belt predominates in the Po Plain subsurface between the Piedmont and Lombardy regions. Prominent tectonic structures belonging to this system also outcrop in eastern Lombardy. The structures of «Dinaric phase» in the Dolomites may be referred mainly to this event; in this picture the Mt. Parei conglomerates could be an equivalent of the Lombardian Gonfolite. The Middle-Late Miocene compressional events produced widespread deformation in the central and eastern regions of the Southern Alps with ENE-trending prevailing structures, including the NNE trending thrusts of the Giudicarie region. The Messinian to Plo-Pleistocene compressional structures mainly affected the eastern regions of the Southern Alps along the southernmost border in the Friuli external arc. This last belt is probably kinematically linked to the buried frontal Apennine chain. A comparison between the neoalpine tectonic accretion of the Southern Alps and the Northern Apennines is attempted in the frame of the geodynamic evolution of the Western Mediterranean domains.