Late Quaternary catchment evolution and erosion rates in the Tyrrhenian side of central Italy

This work assessed the geomorphological evolution and erosion rates in a small clayey catchment of Tyrrheniancentral Italy, providing chronological constraints for the fluvial deposits of the area for the first time. The studyarea is the catchment of the Formone stream, a left tributary of the Orcia River (Tuscany, Italy). A 5 km-longsection of the valley, up to its confluence with the Orcia, was studied. It has an area of ca. 12 km2 and elevationsbetween ca. 300 and 600 m a.s.l. Two soil samples have been radiocarbon dated. One was located at the top of afluvial terrace (~20 m above the present thalweg), and the other was located near the water divide of a smalltributary catchment: they yielded ages of 2780 ± 40 and 14,050 ± 70 yrs B.P., respectively.These chronological constraints allowed us to reconstruct the geomorphological evolution of the area throughtopographic and GIS analyses, and to estimate late Quaternary erosion rates. The ages provided a chronologicalreference for the terraced fluvial deposits of the Formone and the upper Orcia catchments. The resultant erosionrates are consistent with those in the literature both for the Tyrrhenian side of central Italy and forMediterraneanEurope. Moreover, the results confirmed that very intense erosion processes occurred as a consequence of thePleistocene–Holocene climatic change, as observed in the peri-Adriatic belt of central Italy.