Late quaternary palaeohydrology of Lake Pergusa (Sicily, southern Italy) as inferred by stable isotopes of lacustrine carbonates

Ten metres of lacustrine deposits retrieved from Lake Pergusa (Sicily, southern Italy) were investigated through stable isotope composition (carbon and oxygen) of authigenic carbonate (calcareous muds) and freshwater shells. The core chronology was established through three AMS dates, and by correlation with a previously dated nearby core. Stable isotope data show that the lake water evolution was mainly dominated by evaporation. Between ca. 20 and 28 ka the recovered sediments have very high delta 18O values, likely corresponding to very dry climatic conditions. The observed rapid oscillations in the delta 18O of the recovered sediments during this period also suggest important climatic fluctuations. More humid conditions dominated during the Holocene period, with the wettest interval occurring between ca. 9000 and 3000 years BP. Late Holocene sediments represent a substantial return to drier conditions. The available pollen data from a nearby core substantially confirm this general climatic trend during the Holocene. The positive correlation between delta 13C of the calcareous muds and carbonate content suggests that biological activity played a key role in the carbon isotope evolution of dissolved inorganic carbon. However, a clear climatic signal is not evident from the delta 13C record