Reconstructing natural and human-induced environmental change in central Italy since the late Pleistocene The multi-proxy records from maar lakes Albano and Nemi

Following the final phase of Pleistocene volcanism in the Latium region, the main craters of Albano and Nemi in the Colli Albani volcano started to accommodate a sedimentary sequence in both lakes of variable thickness. In the mid-1990s, an EU-funded interdisciplinary project (PALICLAS) investigated the palaeoenvironmental record of the sedimentary sequences of Lakes Albano and Nemi using a multi-proxy approach. A set of up to 14-m-long cores was recovered from the two maar lakes following a seismic survey. Detailed petrophysical (magnetic), sedimentological and geochemical analyses, combined with a large palaeoecological dataset including algal and bacterial pigments, biological remains such as pollen, diatoms, Cladocera, chir- onomids and ostracods were carried out in three selected sites in Lake Albano and one site in Lake Nemi. A robust chronology was established by integrating accelerator mass spectrometry (AMS) radiocarbon datings, pollen analysis and secular variation record of the magnetic field together with the identification of two tephra layers correlated with the Late Pleistocene Etnean eruption of Bian- cavilla (Y1; 17.2 cal ka BP) and the late Holocene Pomici di Avellino (4.1 cal ka BP). The com- piled results of these investigations provide a detailed chronicle of the response of both lacustrine basins to climate- and anthropogenically triggered environmental changes in central Italy for the past c. 28 cal ka. The Lake Albano record further demonstrate that at least the earliest changes reflect distinct warm/cold cycles that triggered major lake level changes of millennial to centennial duration as a major response of the lacustrine basin to climate forcing. Alternatively, these dramatic lake level variations - also identified during the Holocene - could have been driven by CO2 injec- tions of possible magmatic origin. However, flickering interannual to interdecadal variations further identified within these cycles can be correlated to oscillations of the North Atlantic (NAO) as observed in Greenland ice cores, marine and other lacustrine records. The latter, thus, would favour the climatic rather than volcanic cause for these changes. The Holocene record in both lakes is characterized by organic-rich sediments with a variable development of lamination. Although human activity in the catchment is evident since the mid-Holocene, the global signal indicates that changes in climatic variables such as wind intensity, precipitation and temperature are the most probable factors producing these environmental changes. The response of both lake systems to probable warm/cold episodes during the late Holocene, however, is difficult to disen- tangle from the often-contemporaneous human impact on their catchments.