Extension and compression in the Northern Apennines (Italy) hinterland: Evidence from the Late Miocene-Pliocene Siena-Radicofani Basin and relations with basement structures

The Northern Apennines (NA) hinterland area is characterized by a complex Neogene-Quaternary tectonics where both crustal extension, associated with the Tyrrhenian Basin opening, and crustal shortening in the onshore area took part in the deformation. Analysis of synorogenic deposits preserved in the NNW trending Siena-Radicofani Basin (SRB), extending along a large part of the NA hinterland, documents the evolution of deformation of this sector during the last 9 Ma. Information from subsurface geology (deep seismic lines, commercial seismic lines, and deep wells), surface geology (mapping and structural analysis), and from analogue modeling was integrated and used to infer the tectono-sedimentary history of the SRB and its relation with structures in the substratum, as well as the possible implications for the evolution of the NA hinterland. The results we obtain indicate that the SRB and the adjoining hinterland basins were bounded by thrust anticlines controlling basin development and deformation. Seismic lines across the SRB display various examples of compressional structures affecting the basin fill and the substratum, such as thrust anticlines and reverse faults. Notably, these basin-scale structures exhibit a good correlation with those observed in the field and are consistent with the kinematics of the outcrop-scale compressional structures.