The paper reports the results of a geomorphologic and stratigraphic study of the NW portion of the Upper Tiber Basin (Central Italy), and focuses on the terraced alluvial deposits which are grouped into late Middle-Upper Pleistocene (MUP) and Holocene (HOL) units. The drainage development in the basin was deeply influenced by an active tectonic setting characterized by orthogonal fault systems, which forced river deviations and attracted alluvial deposition in the subsiding portions of the basin. The occupation of this intermountain territory by ancient human communities is recorded by late Prehistoric-Protohistoric archaeological findings collected within or on the surfaces delimiting these units. This archaeological dataset allowed an indicative dating of the major stages of the fluvial evolution between the end of the middle Pleistocene and the late Holocene. The chronological constraint indicates that the morphostratigraphic events recorded in the MUP and HOL units, have reasonably occurred within the two last glacial-interglacial cycles. Rapid climate changes, affecting the surface hydrology and the sediment supply to the river systems, and the active tectonic setting, thus, may account for the gaps in the local archaeological record, including most of the late Paleolithic, the Mesolithic and the early Neolithic. Late Pleistocene and the early Holocene stages of relevant alluvial deposition in a subsiding basin may have caused the burial of the missing cultural stages or may have prevented the human occupation of hydraulically unsafe valley floors.
Alluvial terraced deposits, Intermontane basin, Archaeology, Middle Pleistocene-Holocene, Central Italy.