Late-Holocene alluvial events in the Central Apennines, Italy

A stratigraphic sequence was identified in the Gran Sasso Massif (Central Apennines, Italy), consisting of alluvial sediments and buried soils. The soils, dated by the radiocarbon method, enabled various alluvial phases that have occurred in the last 2500 years to be chronologically framed. These phases were then correlated with the frequency of the Tiber floods at Rome and with the progradation of its delta. The phases of soil burial by alluvial sediments coincide with the periods of intense flooding of the Tiber at Rome (between the second century Bc and the second century AD, between the sixth and the ninth centuries AD, and between the fifteenth and the nineteenth centuries AD) and with periods of strong progradation of the river delta. On the basis of the chronological correlation between alluvial phases, glacial variations, and oscillations in the levels of Lakes Fucino and Trasimeno, it was then possible to establish that, corresponding to the alluvial phases, the hydrological balance of the lakes was positive and, in two of the three cases, the increased flood frequency coincided with the phases of advance of the only glacier located in the Apennines.