New constraints for age determination of the pliocene normal faults affecting the Rapolano-Trequanda ridge (southern Tuscany)

The Rapolano-Trequanda ridge is composed of Triassic- Early Miocene stratigraphic units belonging to the Tuscan Succession, deformed during the tectonic evolution of the Northern Apennines. Early-Middle Pliocene marine sediments and Pleistocene-Holocene continental deposits rest unconformably on the polideformed pre- Neogene substratum. During Neogene and Quaternary, extensional tectonics affected the Rapolano-Trequanda ridge. Extension produced two main superimposed faults populations, different in age. The first is characterised by Early-Middle Pliocene normal and strike-slip faults, NNW-SSE and SW NE striking; the second faults population consists of Pleistocene- Holocene normal faults, about W-E oriented, which reactivated some of the previously developed SWNE striking faults. The age of faulting both of the first and second faults populations has been deduced from faults relationships, as well as by means on tectono-stratigraphical considerations on the pre-Neogene, Pliocene and Quaternary rocks.