Pollen stratigraphy, vegetation and climate history of the last 215 ka in the Azzano Decimo core (plain of Friuli, north-eastern Italy)

The pollen record of the long succession of marine and continental deposits filling the subsident north-Adriatic foredeep basin (NE Italy) documents the history of vegetation, the landscape evolution and the climate forcing during the last 215 ka at the south-eastern Alpine foreland. The chronology relies on several 14C determinations as well as on estimated ages of pollen-stratigraphical and sea-level event tie-points derived from comparison with high-resolution marine records, speleothemes and ice cores. Mixed temperate rainforests persisted throughout MIS 7a–7c, being replaced by conifer forests after the local glacioeustatic regression during early MIS 6. The Alpine piedmont facing the Adriatic foredeeep was glaciated at the culmination of the penultimate glaciation, as directly testified by in situ fluvioglacial aggradation related to the building of a large morainic amphitheatre. The pollen record allows correlation with other European records and with the IRD from N-Atlantic and off Iberia, thus the duration of the penultimate glacial culmination at the southalpine fringe is estimated less than 13 ka between 148 ± 1 and >135 ka. The site was not reached by the Last Interglacial maximum sea transgression and enregistered a typical, though incomplete, Eemian forest record, lacking Mediterranean evergreen trees. A complex sequence of stadial–interstadial episodes is reconstructed during the Early and Middle Würm: major xerophyte peaks match IRD maxima occurred during Heinrich events in deep-sea cores offshore Iberia and in the N-Atlantic and allows to frame lumps of interstadial phases, marked by Picea peaks, each one including several DO warm events. Broad-leaved thermophilous forests disappeared from the north-eastern plain of Italy at the end of the Early Würm, whereas reduced populations of Abies and Fagus probably sheltered even during the Last Glacial Maximum. A renewed fluvioglacial in situ deposition between 30.4 ± 0.4 and 21.6 ± 0.5 ka cal BP sets the time and duration of the last glacial culmination in the pedemontane morainic amphitheatre. Palynomorphs from Plio-Pleistocene marine successions were reworked by glacier erosion and deposited in the lowland during both the penultimate and the last deglaciation phases. This explains a bias affecting previous pollen records from the region.