TETHYAN HERITAGE IN THE DEVELOPMENT OF THE NEOGENE UMBRIA-MARCHE FOLD-AND-THRUST BELT, ITALY - A 3D APPROACH

The Umbria-Marche fold-and-thrust belt (Northern Apennines, Italy), pr ovides excellent opportunities to evaluate the structural heritage of the opening of the Mesozoic Tethys Ocean in the 3D geometry of the Neo gene compressional structures related to the Alpine Orogeny. ?he struc ture and evolution of a portion of the southernmost belt, between the Nera River and the Rieti Basin, are described as a field example, and the kinematics along well-exposed Mesozoic extension structures are pr ovided. Cross-section restoration shows a close coincidence between th ese extension structures and the Neogene thrust ramps, thus suggesting that the geometry of the latter was controlled by the map distributio n of the former. Sequential balancing also allows for the definition o f the geometrical pattern of pre-existing normal faults, which were pr oduced in response to a uni-directional or a two-directional extension stress field. The inferred direction of principal extension, correcte d for the effects of late deformation, is consistent with that propose d for the northern margin of the Adria Promontory in global-scale plat e tectonic reconstructions.