CATUTTO C., CENCETTI C. & GREGORI L.
Il bacino di Pornello – Frattaguida e l’evoluzione idrografica plio – pleistocenica tra il fiume Paglia e il fiume Tevere – The Pornello – Frattaguida Iacustrine basin and plio-pieistocenic hydrographic net’s evolution between Paglia River and Tiber River
Pages 161-169
Abstract
The geomorphological, morphoneotectonie and hydrographic characterist ics of the area between rive rs Paglia and Tiber allowed to understand the evolutio n of th at zone from che Pliocene. In the Upper Pliocene the hilly belt which links the limestone Apennine to the sea was drained by two main rivers {palecl’[e store and paleof cr sinone); these rivers, flowing towards SW, builded two di stinct hut close delta s in the pliocen ic sea. The beginning of the dis tcnsive tectonics leaded to a general tiltin g of the area towards ENE. Th e maximum raising happened near to the coast-line and the sea regressed \’(festward , wi th an almost complete emersion of the delt a of the paleobl estore. At the same t ime the Northern-cemrel sector of the same area sinked , caus ing an inversion of the flow of the paleo-Nestore and the format ion of the TavemcllePietr afitra lacustrin e basin. A fault , corresponding to the Migliari creek, interrupted the flow of the paleoFer sinone ; thi s caused the formati on of the Pornello-Fran aguida lacust rine basin. At East two other depressions (S. Fortunato and Ripalvella swamps) formed ; these basins have been filled and dr ained by the presen t hydrographi c net. At West the definitive marine regression left a dep ressed area where the Fabro swamp was formed ; at South the sea regression was followed by the sett ing up of the present hydrogr aphi c net, which dr ained the Fab ro swamps (T. Chiani).