Pliocene climatic cycles and altitudinal forest development from 2.7 Ma in the Northern Apennines (Italy): evidence from the pollen record of the Stirone section (~ 5. 1 to ~ 2.2 Ma)

Marine Pliocene deposits from Northern Apennines (Italy) have been submitted to palynological studies in order to obtain a floristic, vegetational, and climatic record. The history of the Pliocene land environment and climate has been reconstructed on the basis of the chronostratigraphic framework available for the Stirone section. The Zanclean is characterized by long and relatively stable subtropical to warm-temperate climatic conditions. During the Piacenzian and Gelasian, a cooling is testified by both the reduction as well as the disappearance of some mega-mesothermic elements and the increase of microthermic ones. Laminated sediments, calibrated at ca 2.8 Ma, indicate a wet period characterized by repeated warmer/cooler fluctuations. Cyclic alternations between mega-mesothermic and meso-microthermic elements, starting after ca 2.7 Ma, are characterized by the opposition of coniferous (Picea mainly) and deciduous forests elements. The major increase of Picea has been stratigraphically correlated with the maximum expansion of the Arctic ice.