L'impronta del "Younger Dryas" e degli "Heinrich Events" nell'evoluzione climatica e ambientale dell'Italia centrale

Abstract

Palaeoclimatic studies conducted in Central Italy on various sedimentary environments, have as their objective the identification of the palaeoclimatic changes contemporaneous with Heinrich Events, H1 (14,300 y B.P.) and H2 (21,000 y B.P.), and YD (ca. 11,000 y B.P.). Morphological and stratigraphical studies conducted in different Central Apennine sites, have identified the presence of lacustrine, eolian, alluvial, and stratified slope deposits, phases of pedogenesis, as well as evidence of discountinuous permafrost. The deposits taken into consideration are those which yielded a radiocarbon date between ca. 21,000 and 10,000 years ago. Correlation between sites and the dating of particular horizons was made possible by the presence of three tephra layers interposed within the various sediments that form the stratigraphical series. In correspondence with Heinrich Events and Younger Dryas, lake level oscillations, phases of fluvial and eolian activity (which allow an evaluation of the hydrological balance), stratified slope deposits (linked to arid phases, and also, in the Late Pleistocene, to intense gelifraction), solifluc-tions (indicators of cold-wet climates), traces of discontinuous permafrost at high elevations (which indicate that the annual mean temperature, at the moment of their formation, was around -1 - -2 °C), have been identified. From the data obtained, it is possible to state that climatic cooling and drying in Central Italy are contemporaneous with both Heinrich Events and the Younger Dryas. It has also been assumed the approximate value of the annual mean temperature difference compared to present-day values and the time when occurred HI (-6,7 - -7,7 °C) and YD (-6 - -7 °C).