Tectonics of the Mattinata fault, offshore south Gargano (southern Adriatic Sea, Italy): Implications for active deformation and seismotectonics in the foreland of the Southern Apennines

摘要

The Mattinata fault is an E-W-trending feature, ～50 km long, that cuts across the Gargano Promontory in the foreland of the Southern Apennines. Most researchers agree that it is a strike-slip fault, although the timing of activity is not well known, mainly because of the scarce occurrence of Cenozoic sediments. This contribution aims to describe the eastward extent of the Mattinata fault in the Adriatic Sea using a grid of multichannel seismic profiles specifically acquired for this study and taking advantage of the occurrence of offshore Oligocene to Quaternary sediments to help date the deformation. Results indicate that from the late Miocene to the Quaternary, compression dominated, and only a limited component of strike slip occurred along the fault A strike-slip tectonic regime, on the other hand, was likely dominant during the Late Cretaceous to Paleogene. Seismicity affects Gargano at basement depth and extends northward into the central Adriatic, suggesting that the offshore extent of the Mattinata fault may not currently represent the main site of foreland deformation within the Adriatic region. Although the Mattinata fault probably originated as a crustal-scale strike-slip fault, it has been subsequently reactivated in different tectonic regimes. The strike-slip Ml = 5.4 2002 San Giuliano (Molise) earthquake, located ～70 km west of the Mattinata fault outcrop, seems to have been related to the reactivation of a set of preexisting foreland faults, and it does not characterize the seismotectonics of the entire Mattinata fault. Our reconstruction has wide implications, not only for a better understanding of the Tertiary evolution and active tectonics of the Adriatic foreland, but also for general rela- tionships among preexisting structures, foreland tectonics, and seismotectonics.