Evoluzione paleoidrografica della pianura veneta meridionale e rapporto Uomo-Ambiente nell'Olocene

This multidisciplinary research studies the palaeohydrography of the distal part of the Adige and Po alluvial plain (north-eastern Italy) for understanding man-environment relations during the Late Holocene. The southern Venetian plain corresponds to the distal tracts of the Adige and Po alluvial systems. Archaeological investigations in this area, indicate the existence of a complex settlement network, starting in the Bronze Age (2200-1000 B.C.) (Bellintani & Zerbinati, 1984; Bellintani, 1986; Salzani, 1992) and continuing in the Iron Age (1000-200 B.C.) and Roman times (200 B.C.-476 A.D.) (Peretto, 1986) with a well-preserved Roman centuria. The reconstruction of the palaeoenvironmental conditions during the Late Holocene has been mainly based on remote sensing interpretation and archaeological data (Peretto, 1986; Marcolongo, 1987; Marcolongo & Zaffanella 1987, Cremonini, 2007). In this reseach, new geomorphological, chronostratigraphical and petrographical data are presented, in order to provide better insights on the man-environment relationships in the study area. In Cona some drills reached the caranto palaeosoil that represents the limit between Pleistocene and Holocene sequences allover the Venetian-Friulian Plain (Fontana et al., in stampa). The radiocarbon dating of the back-swamp peats indicates that the depositional rate was low in the Early and Middle Holocene, whereas it was higher after 2763-2192 B.C. Geomorphological, stratigraphical and petrographical results confirm the presence of a Po branch from Fratta Polesine through Sarzano to Cona which activity began in the same period and produced the Villadose crevasse splay. The palaeochannel deactivation dates back in the Late Bronze Age as confirmed by archaeological settlement in Saline that lies on the natural levee deposits. In the Roman times, the Decumanus Maximum of the centuriation and the Ca' Motte villa were settled over the Villadose crevasse deposits. Both Saline and Ca' Motte are located in places characterized by high geomorphological and good drainage conditions. Modern Adige River cuts the alluvial ridge of the Po northern branch in San Martino di Venezze. Pettorazza chronostratigraphic and petrographic evidences of a buried sand body of Adige River show that a first activity dates back since the Roman Age to the Early Middle Age whereas the deposition of the modern alluvial ridge started at the beginning of the second millennium A.D. Some authors (Peretto, 1986; Balista, 2004) have suggested the presence of a southern branch of Adige River active during the Roman Age, that produced the alluvial ridge cut, in more recent times, by the Adigetto channel. Stratigraphical results show that, in Ramalto, no important sand body in correspondence of the Adigetto alluvial ridge.