A Cenozoic Shift From Extensional to Strike-Slip Tectonics in the Central Mediterranean Sea

High-resolution 3D seismic reflection data, structural interpretations and expansion index analyses are combined in this work to explain the mechanisms that drove a newly discovered shift from extensional to strike-slip tectonics in the central Mediterranean region. In the Crotone Basin, Early Pliocene extension predominated at first as proven by the nucleation of N- to NE-striking normal faults bounding half-graben basins and tilt blocks. Fault length reached ∼13 km, with associated half-grabens being 5–8 km wide and up to 2.5 s two-way time deep. Extensional tectonics at this stage followed tectonic collision between the Calabrian margin and the Apulian foreland; the removal of dense lithospheric mantle induced sharp elevation gradients and a rapid uplift of continental crust in the study area, promoting isostatic imbalances that ultimately led to extensional orogenic collapse. This same phase of extension was accompanied by the reactivation of inherited fault systems, which occurred together with the forward migration of the Calabrian Arc and oceanization of the Tyrrhenian Sea. Conversely, normal-oblique to strike-slip faulting has predominated offshore Crotone since the Late Pliocene as recorded by the development of elongated (up to ∼22 km long) and narrow (∼3 km wide) NW-trending pull-apart basins. Structural styles have since then been influenced by rheological contrasts between the continental Apulian foreland and Ionian oceanic lithosphere, which activated a broad WNW-striking shear corridor. As a corollary of this work, modern structural and kinematic evidence indicates that fault segments within this shear corridor are arranged in an en echelon geometry and act as conjugate structures accommodating the progressive fragmentation of the overriding Apulian plate. On a broader scale of analysis, the transition from pure extension to strike-slip tectonics documented offshore Crotone is associated with the differential subduction of heterogeneous foreland domains, a phenomenon that reflects the dynamic evolution of the central Mediterranean backarc system as a whole.