Sedimentological evidence for environmental changes since 34,000 years BP from Lago di Mezzano, central Italy

Sediment cores recovered from Lago di Mezzano, central Italy, were petrogra phically and geochemically (dry densitity, total organic carbon) investigat ed. A floating chronology was established with sedimentation rates derived from varve thickness measurements, and this chronology was both supported a nd extrapolated with calibrated AMS-C-14-datings. The profile has a length of 29.7 m and comprises a total of 34,000 years. Late Pleistocene sediments consist of minerogenic-organic mud with few bent hic diatoms and an organic carbon content of 2%, thus suggesting a high all ochthonous input. The onset of the Late Glacial at 14,580 cal BP is documen ted by a lithologic change to more organic-dominated sedimentation. The You nger Dryas cold event is recorded between 12,650 and 11,400 cal BP and exhi bits higher dry densities and minerogenic input. These dates agree with rec ords from other lacustrine archives in Europe and the Greenland ice cores. The early Holocene comprises a laminated organic diatom gyttja deposited at a time of climatic amelioration and increased primary productivity. The es tablishment of an anoxic hypolimnion enhanced the varve and organic matter preservation. Since 3700 varve years BP the sedimentation pattern has been strongly influenced by human impact, as documented by the increase in miner ogenic sediments and turbidites as well as higher sedimention rates. The on set of this influence coincides with a Bronze Age settlement at the lake sh ore.