HOLOCENE AGGRADATION/EROSION OF A TUFA DAM AT TRIPONZO (CENTRAL ITALY)

The C-14 dating of organic-rich layers from the backfill sequences of the Triponzo village tufa dam (Tiber River basin) allows us to outline the Holocene aggradation/erosion stages of fluvial tufa in Central Italy. Here, the deposition of tufa first occurred prior to 8240 +/- 75 C-14 yr BP (7480-7070 cal bC) and continued, even if with different rates, giving rise to a lacustrine/swampy basin upstream. Since 3760 +/- 60 C-14 yr BP (2350-2010 cal bC) a sequence of alternating periods of dam erosion and aggradation occurred. After 2825 +/- 60 C-14 yr BP (1160-830 cal bC) fluvial incision eventually cut the dam down to the present valley bottom, being only interrupted by a short-lived phase of dam aggradation which caused the formation of a strath terraces covered with gravels and tufa sands. A comparable evolution pattern is shown by other tufa dams in Central Italy. This paper deals with the control factors of tufa deposition/erosion during the Holocene with a particular reference to the role of climate changes.