A kinematic model of the Tyrrhenian-Apenninne system.

A new model is proposed for the kinematic evolution of the Tyrrhenian extension and the formation of the Apennine belt. The model is compatible with boundary conditions represented by the motion of the large plates involved in the Mediterranean tectonics. The kinematic parameters (Euler rotations) are calculated starting from a morpho-tectonic and geologic analysis of the Tyrrhenian sea and the Apennine belt. The morpho-tectonic analysis of the Tyrrhenian multibeam bathymetry and SRTM images of the emerged part of the chain have been used to identify the principal tectonic structures of the Tyrrhenian-Apennine system. This analysis allowed to distinguish four sectors within the Apennine belt: northern Apennine, central Apennine (including the Umbria-Marche Apennine), southern Apennine, and Calabrian Arc. For each sector an Euler pole of rotation relative to the Sardinia-Corsica block was determined starting from the identified morphostructures. The temporal range associated to each stage pole and the rotation angles were determined on the basis of geologic constraints and closure of the kinematic circuit. The model is presented through a series of reconstructions illustrating the genesis of the structures bounding the Apennine sectors, which were associated with different directions of extension within the Tyrrhenian basin. The main geologic implications of the model are represented by the compatibility of the tectonic structures predicted along the boundaries of the Apennine sectors during the rotation and the lateral structural variations that can be observed along the belt. Extension results from diverging directions of migration between two sectors, whereas compression is associated with converging directions. In this model extension along a sector boundary is responsible for the transverse structures which are known as “AntiApennine faults”, for the formation of transverse wedge-top basins, for low-angle faulting not compatible with the Tyrrhenian directions of extension, and for the exhumation of deep parts of thrust belts. Conversely, converging directions of migration between the central and southern sectors of the Apennine chain, which are associated with the kinematic of extension within the Vavilov Basin, form the contractional structures that can be observed along the Ancona-Anzio and Volturno-Sangro lineaments.