Alps in the Apennines?

Abstract

In the Southern Apennines and Calabria outcrop metamorphic slices of hercynian and/or alpine age. The reconstructions by Glauco Bonardi and co-authors of an alpine subduction-related origin for the emplacement of those rocks is still supported by a number of tectonic and geodynamic constraints. Alps and Apennines are two end members of opposite subduction zones (i.e., “E”-ward and “W”-ward), having different depth and evolution of the accretionary prism basal decollement. The PTt evolution of the metamorphic rocks of Calabria can be better reconciled with an earlier alpine-type evolution, where the continental and oceanic slices of crust have been subducted and re-exhumed by the deepening of the decollement planes into both the upper and lower plates and accreting the orogen. The early alpine emplacement of those metamorphic rocks is testified by their high structural elevation, the HP/LT assemblages and by stratigraphic constraints (e.g., Bonardi et alii, 2005). Therefore it can be interpreted that the earlier alpine subduction was gradually substituted by the opposite W-directed Apennines subduction, having in its hangingwall the boudinated relics of the alpine history.