The palaeolake deposits of Piànico (Southern Alps, Bergamo, Italy) include a continuous succession of ca 15,500 exceptionally preserved calcite varves that formed under peak interglacial conditions. The varved sequence, which has been tephrochronologically dated to ca 400 ka ago, allows reconstructing natural climate variability of an interglacial period. A multi-proxy approach including varve microfacies, detrital layers, stable isotopes and geochemistry was chosen for this sequence. The unique combination of microfacies and high-resolution isotope analyses allowed, for the first time, detecting an abrupt 1000 year cold oscillation that took place after at least 10,000 years of peak interglacial conditions; such an oscillation has not been so far observed in the Holocene. Therefore, from the Piànico interglacial sequence evidences for so far unknown mechanisms controlling interglacial climate dynamics are emerging. The ongoing work focuses on the long sequence of detrital layers, proxy for extreme precipitation events, in order to analyse their recurrence pattern and seasonality.

Partner: A. Moscariello (field geology, University of Cambridge, UK), A. Lotter (diatoms, University of Utrecht, The Netherlands), S. Rossi (palynology, Universita degli Studi dell' Insubria, Italy)