GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 - POSTER GNGTS 2023 In this contribution, we present a reconstruction from the western to eastern sectors of the southern Tuscany offshore between Elba Island and Monte Argentario promontory (Italy) based on a new interpretation of a public data set of seismic reflection profiles, specifically re-elaborated push their resolution and interpretability. We focused on the evolution of the sedimentary basins from the middle Miocene to Pleistocene time to provide a more comprehensive and robust picture of the evolution of those areas to shed new light on the first phases of the evolution of the Tyrrhenian Sea. The seismic profiles show an articulated topography of the pre-Neogenic deformed acoustic basement, organized in thrust-related structural highs and narrow, mostly N-S and NNW-SSE trending basins filled by sedimentary successions separated by unconformities. We identified an intimate relationship between the thrust-related structural highs and the position of the basins located at the forelimb and backlimb of the antiforms. Indeed, the Tuscan Shelf neogenic basins started to develop as intermontane basins along the flanks of the inherited antiforms. Such a setting influenced the asymmetrical or symmetrical evolution of the basins. The Tyrrhenian extension was set up probably during the middle Miocene over the Tuscan Shelf, while the extensional front migrated from west to east, progressively activating and deactivating the high-angle faults controlling the basins deposition. From the Messinian, a more regional collapse leads to the deepening and widening of the basins. During the lower Pliocene, the deactivation of all normal faults is recorded. After the late-Pliocene/early Pleistocene, the area turned into a passive and widespread sinking stage without any frank tectonic activity. . Intriguingly, and partially in contrast with previous works, no evidence of low-angle normal fault was observed. Such a model poses new questions on the crustal-scale mechanisms responsible for the extensional process, also establishing a new starting point for a full unraveling of the Tuscan Shelf evolution. References Bartole, R., 1995. The north Tyrrhenian–Northern Apennines postcollisional system: constraints for a geodynamic model. Terra Nova 7, 7-30. Bonini, M., Sani, F., Stucchi, E.M., Moratti, G., Benvenuti, M., Menanno, G., Tanini, C., 2014. Late Miocene shortening of the Northern Apennines back-arc. Journal of Geodynamics, 74, 1–31. Buttinelli, M., Scrocca, D., De Rita, D., Quattrocchi, F., 2014. Modes of stepwise eastward migration of the northern Tyrrhenian Sea back-arc extension: Evidences from the northern Latium offshore (Italy). Tectonics, 32, 187–206, doi:10.1002/2013TC003365.