A ~125° post-early Serravallian counterclockwise rotation of the Gorgoglione Formation (Southern Apennines, Italy): New constraints for the formation of the Calabrian Arc

Abstract

The Southern Apennines, Calabro-Peloritane block, and Sicilian Maghrebides form a ~700 km long orogenic bend, known as Calabrian Arc (Cifelli et al., 2007). The bending of this orogenic system was realized progressively through opposite-sense rotation of the two limbs, counterclockwise (CCW) in the Southern Apennines and clockwise (CW) in the Sicilian Maghrebides, synchronous to the Miocene-to-Present opening of the Tyrrhenian Sea. Despite the wealth of paleomagnetic data from the Southern Apennines, the main Miocene rotational phase still remains poorly constrained in time and, more importantly, data from the most internal paleogeographic domains of the belt are completely lacking. The Gorgoglione Formation, a middle Miocene piggy-back deposit of the Southern Apennines, unconformably resting over the internal Sicilide Unit, offers the unique opportunity to document the deformation pattern of the most internal units, and reconstruct the incipient tectonic phases leading to the formation of the Calabrian Arc. New paleomagnetic and biostratigraphic data from the Gorgoglione Fm. reveal a post-early Serravallian ~125° CCW rotation with respect to stable Africa. Such a large rotation, affecting the Gorgoglione Fm. (and consequently the underneath allochthonous Sicilide nappe) exceeds by ~45° the maximum mean CCW rotation previously reported for the Southern Apennines. We propose that the additional ~45° CCW rotation measured in the Sicilide Unit is the result of an earlier, late Miocene phase of deformation related to the onset of the Tyrrhenian Sea opening and affecting the most internal paleogeographic domains of the Southern Apennines. Our reconstructed tectonic scenario confirms and emphasizes the central role of the Ionian slab in the geodynamic evolution of the central Mediterranean.