Extensional Quaternary faulting and basin development in the southern Campania-Lucania arc (Italy): architecture and kinematics constrained by field and seismic reflection data

A well-known evolutionary feature of the Italian Apennines is the superimposition of Quaternary extensional deformations on the Mio-Pliocene orogen. The Campania-Lucanian area is no exception, and both west and east-dipping Pleistocene normal faults, with the associated continental basins, have been recognized to dissect the thrust and fold belt. Most of these faults have been investigated in detail in their geometric parameters (attitude, length, and dip-angle at the surface), associated stratigraphic omission, chronology of deformation, and Quaternary slip rates. The association with recent strong earthquakes (e.g., the Irpinia Faults) or low to medium-magnitude instrumental seismicity (e.g., the Mercure-Morano Calabro fault alignment) demonstrates that some of them are presently active and seismogenic. Nevertheless, uncertainties about some significant aspects remain unsolved as f.i.: i) the subsurface geometry of extensional faults, ii) the depth and sense of dip of their decollement level, iii) the hierarchy between conjugate faults (i.e., which structures - the west- or the east-dipping – represent the master faults?), and iv) the relationships occurring at depth between the normal faults and the major thrust surfaces (the former throughout displace the second or locally invert them?). In addition, most of the known faults have been described as individual structures, without being contextualized in the framework of a crustal-scale regional array related to the geodynamics of the TyrrhenianApennine system. In this work, the above crucial issues are addressed by studying a ~4400 square km wide sector of the Campania-Lucanian Apennines, bordered to the north by the Sele Valley and to the south by the Mt CervatiMontemurro transect. In this area, we have studied a grid of 12 seismic lines, for a total length of ~380 km, constrained at the surface with original field data, and calibrated at depth with the available well logs. The depth-conversion of the lines, which show quite good quality down to 5sec twt, was the base for the drawing of a series of geological transects across the entire area. The whole set of geological and seismic sections, interpreted down to the top of the Apulian platform, allowed the building of a three-dimensional subsurface geological model. This latter is mainly focused on the geometries and amount of displacement of the extensional faults but also takes into account their relationships with the main thrust sheets. The model also defines the reciprocal interplay between the antithetic boundary faults of the quaternary depressions (Auletta, Vallo di Diano, and Agri Valley), the geometry of the sin-tectonic sedimentary infill, and the locations of their depocenters. The 3D Quaternary faults here reconstructed for the Campania-Lucania area are an integral part of a larger tri-dimensional geological model extended to the entire southern Apennines, which is one of the main expected products of the MUSE 4D PRIN project.