Influence of Inversion Tectonics in the Bending of a Foreland Fold-and- Thrust Belt: The Case of the Northern Apennines (Italy).

The outer Northern Apennines fold-and-thrust belt has been interpreted in the literature either as an orocline, a primary or a progressive arc, with a thin- or thick-skinned tectonic style. This paper reviews prior theories on the origin of the curve-shaped Northern Apennines belt and integrates these past findings with more recent geologic, structural, and paleomagnetic data collected from the Northern Apennines area. Documenting the presence of inversion tectonics is particularly important in identifying the origins of this foreland belt. The inversion tectonics evidences indicate that the foreland Northern Apennines chain is a progressive arc whose shape is strongly influenced by the architecture of the Mesozoic Adria paleomargin, as documented by a correlation between structural units and paleodomains. The arc curvature was accentuated during orogenesis by the occurrence of tectonic rotations. We propose that the curve-shaped Northern Apennines foreland fold-and-thrust belt evolved as a progressive arc under the influence of inversion tectonics and demonstrates a thick-skinned deformation style with a conservative amount of shortening. In the context of the Apennine-Maghrebide orogen, the Northern Apennines Arc is clearly distinguishable from the Southern Apennines-Calabrian Arc by differences in paleogeographic domains, stratigraphic successions, tectonic style and rotations, and geodynamic evolution.