Neogene-Quaternary evolution of the central Apennine orogenic system (Italy): a structural and palaeomagnetic approach in the Molise region

We report on new palaeomagnetic and magnetic fabric analyses of mainly Upper Miocene sedimentary sequences from the external central Apennine fold and thrust belt (Molise area), where the principal compressive structures are clearly non-coaxial. The sampling was can-led out on the E-W-oriented Matese-Frosolone thrust sheet, that for its geographical position and structural setting (superposition of thrusting, strike-slip and extensional tectonics since Late Miocene to present-day) represents a key structure for the comprehension of the Neogene-Quaternary evolution of the entire Molise area. Palaeomagnetic results suggest that the Matese-Frosolone thrust sheet counterclockwise rotated at least 35 degrees after Messinian times. These data confirm that the present-day trend variability observed in the main compressional structures in the Apennine chain can be related to rotations about vertical axes rather than to changes in the stress field orientation, at least since Late Miocene times. Magnetic fabric analyses indicate that the studied sediments were subjected to very mild deformation, suggesting that the surface emergence of the thrust front of the Matese-Frosolone unit is located farther north, far from the studied area. Well-defined magnetic lineations of tectonic origin were only observed in sites close to localised belts of strike-slip deformation. (C) 1998 Elsevier Science B.V. All rights reserved.