Tectonic evolution of arcuate mountain belts on top of a retreating subduction slab: The example of the Calabrian Arc

In this paper, new paleomagnetic results from the Calabrian Arc are presented, together with a critical review of all paleomagnetic data collected in the last decades in southern Italy. Our study is focused on the upper Miocene to middle Pleistocene deposits of the Crati extensional basin, a sector of the arc where an abrupt change in the sense of paleomagnetic rotations is observed. Paleomagnetic data indicate that the Crati basin underwent a uniform clockwise (CW) rotation of about 15 degrees-20 degrees in its central and southern part, whereas the northern sector is organized in small-scale fault-bounded blocks, which rotated independently. We interpret this pattern of deformation as the evidence of the complex nature of this area, which represents the boundary between two domains characterized by opposite rotations: the southern Apennines, which rotated counterclockwise, and the Calabria and Sicily, which rotated CW. Integrating these new paleomagnetic data with paleomagnetic data from southern Italy, we reconstruct the history of paleomagnetic rotations through time. Paleomagnetic rotations highlight the peculiarity of the formation of the Calabrian Arc curvature and imply that either an oroclinal bending model or a progressive arc model cannot be simply applied to the Calabrian Arc formation. We describe a realistic tectonic-geodynamic model, where the progressive curvature of the Calabrian Arc is framed within the space-time evolution of the Ionian subduction system.