The Plio-Pleistocene Bradano basin and the Southern Apennine Orogenic Wedge: evidences of accretion collision and segmentation of Apulian continental plate

The Pliocene-Pleistocene tectono-stratigraphic evolution of the Bradano Basin in the Gulf of Taranto is investigated by means of multi-scale, high-resolution seismic reflection profiles combined with exploration wells and seafloor bathymetry. Being located between the Ionian Calabrian Margin, to the West, and the Apulian Margin, to the East, the Bradano Basin is the site of pervasive tectonic deformations part of the southward and seaward prolongation of the Southern Apennines orogenic wedge. Within the Gulf of Taranto, five main domains surround the Bradano Basin: the Calabrian Arc, the Calabrian Accretionary Wedge, the Southern Apennines and the subducting Apulian Foreland Ramp. The external fronts of the Calabrian Accretionary Wedge and Southern Apennines progressively migrated toward ESE overriding and colliding with the subducting Apulian lithosphere during the Pliocene-Pleistocene. As previously recognized, this collisional setting has been responsible for the formation of the Pliocene-Pleistocene Bradano Foreland Basins System while the Apulian Foreland Ramp was uplifted and down-flexed toward west but generally considered as an “undeformed” foreland area. The multi-scale analyses of geophysical data reveals active deformation involving the foreland ramp which was affected by different tectonic phases: contraction and transcurrent deformations along E-W trending faults active from the Miocene to recent times; thrusts and thrust-related anticlines even underneath the Southern Apennine fronts; NW-SE and N-S striking thrust-related folds affecting the whole Apulian continental plate, likely inverting inherited Mesozoic-Pliocene extensional faults and gently folding the Pliocene-Recent deposits. Two main transcurrent systems have been recognized to segment the continental margin: the Amendolara Transpressive System and the new Apulian Transtensive System on the foreland ramp never described before this study. The above structures played a major role in the Bradano basin tectonic evolution during two main tectono-stratigraphic events. During middle-upper Pliocene, the Amendolara Transpressive System, a left-lateral strike-slip zone, segmented the Southern Apennine thrust fronts actively moving toward E onto the Apulian plate along a shallow detachment surface. At the end of this stage, the Southern Apennines frontal thrusts could thrust over the Pliocene Bradano Foredeep Basin as well as the underlying western portion of the Apulian Plate. The Apulian Transtensive System was active and, locally, extensional faults were inverted. During the second event (from Pleistocene to Present), the compressional deformations were localized at depths deeper than the subducted Bradano Foredeep Basin. Out-of-sequence thrusting reshaped the Southern Apennines orogenic wedge while, to the east, the Apulian Transpressive System and the inversion of extensional faults were still active. The proposed evolutionary model suggests that Bradano Basin, laying on top of the western margin of Apulian Plate, and the Apulian Foreland ramp are part of the Southern Apennines orogenic wedge whose outermost front can be located in the Apulian Foreland Ramp since Pliocene.