Palaeogeographic evolution of the Terni basin (Umbria, Italy).

In this paper, a study focusing on the geomorphologic elements that characterise the Terni basin has led to underline the close interdependence between tectonic activity and the laeogeographic evolution of this territory. The role of strike-slip faulting is generally inferred in several models of Apennine tructural evolution, but which in this area has not yet been ecognised in a clear structure in the field element. The aim of this paper is to introduce new morphologic elements related with the strain pattern connected to the recent geodynamical volution of central Italy. Unlike the other intermontane basins of central Italy, the Terni basin was formed and has evolved thanks to normal fault set activity, where the dislocations converge east of the city of Terni and diverge towards the west (at the Narnese-Amerina mountain range). Therefore, the activity of these faults seems to indicate that the southern portion of the Martani Mountain range is continuously shifting and opening the Terni basin. The oldest faults (lower Pliocene) border the basin, whereas the more recent ones (Pleistocene) are gradually moving to its centre. Furthermore, other vertical faults, normal like the recent one, unblock the territory, gradually diminishing it and progressively lowering it towards the west.