New evidence of active transtensional deformation in apulia foreland (n-ionian sea).

Abstract

The response of continental forelands to subduction and oblique collision is a widely investigated topic in geodynamics. The deformation occurring within a foreland shared by two opposite-verging chains, however, is not very common and poorly understood. The Apulia block, at the southern end of the Adria microplate, Central Mediterranean, represents one of these latter cases, being the common foreland of the Dinarides and Apennines orogens. In its southern part, the Apulian foreland has preserved the Mesozoic paleomargin at the transition with the old oceanic Ionian crust that conversely underwent subduction under the Calabrian and Hellenic arcs. For these reasons, Apulia represents an interesting and rare case of study where double orogens and subduction have interacted with the foreland block. As described by various authors, the almost symmetrical bending of the Apulia foreland due the opposite load of the adjacent chains, produced a system of NW-SE trending normal faults. The precise age and the role of these faults have not been yet determined due to the lack of available information. In this contribution we investigated the internal deformation of the Apulia foreland using geophysical data at various resolutions and scales over a wide area. We used multichannel seismic profiles, part of which are provided in the collaborative framework between Spectrum Geo and INGV, recorded up to 12 s and provide a consistent imaging of the upper crustal setting of the Apulia foreland. High-resolution multichannel seismic profiles, multibeam high-resolution bathymetry and CHIRP profiles recently acquired by R/V OGS Explora provide constraints on the recent activity of the major fault systems identified. The analysis of this multiscale dataset highlights the presence and the role of a major NW-SE oriented active fault system which obliquely cuts the Apulia foreland. The presence of this fault system has already been hypothesized based on sparse seismic profiles, but its lateral continuity has never been documented. From the seismic viewpoint, this structure lies in a relatively silent area. Nonetheless, it hosts the 1743 Southern Apulia Mw 6.8 earthquake which widely damaged the Salento (S-Italy) and Ionian Islands (Greece) regions and whose source is still a matter of debate. This new geophysical dataset allowed us to reconstruct the 3D geometry of this fault system, whose architecture suggests a transtensive kinematics, and to analyse the syn-tectonic basins associated with the major faults which recorded the Late Quaternary to Holocene deformation. This work is being developed in the frame of the project “FASTMIT”, funded by the Italian Ministry of University and Research.