Extensional tectonics during the Tyrrhenian back-arc basin formation and a new morpho-tectonic map

We present a new tectonic map focused upon the extensional style accompanying the formation of the Tyrrhenian back-arc basin. Our basin-wide analysis synthetizes the interpretation of vintage multichannel and single-channel seismic profiles, integrated with modern seismic images, P-wave velocity models, and high-resolution morpho-bathymetric data. Four distinct evolutionary phases of the Tyrrhenian back-arc basin opening are further constrained, redefining the initial opening to Langhian/Serravallian time. Listric and planar normal faults and their conjugates bound a series of horst and graben, half-graben and triangular basins. Distribution of extensional faults, active throughout the basin since Middle Miocene, allows us to define an arrangement of faults in the northern/central Tyrrhenian mainly related to a pure shear which evolved to a simple shear opening. At depth, faults accommodate over a Ductile-Brittle Transitional zone cut by a low-angle detachment fault. In the southern Tyrrhenian, normal, inverse and transcurrent faults appear to be related to a large shear zone located along the continental margin of the northern Sicily. Extensional style variation throughout the back-arc basin combined with wide-angle seismic velocity models allows to explore the relationships between shallow deformation, faults distribution throughout the basin, and crustal-scale processes as thinning and exhumation.