Chronostratigraphic distribution of cetaceans in the Pliocene of Northern Apennines (Italy): palaeoecological implications

A large number of cetacean fossils have been recovered through the time from the Pliocene deposits in Northern Apennines thrust belt, on both the Padan-Adriatic and the Tyrrhenian side. In this work, the cetaceans of Castell'Arquato Basin (Padan-Adriatic side) have been placed within a high-resolution chronostratigraphic framework available for this area. This results in a better assessment of their evolutionary history and of the palaeoecologic factors controlling their diversity and abundance through the time. Our results document a greater diversity between 3.1 and 2.7 Ma time interval, likely due to the development of eutrophic conditions during precessionally-driven insolation maxima at 400 ka eccentricity maxima, which are recorded in deeper depositional settings by sapropel clusters. Eutrophic conditions kept a complex trophic chain, as currently observed in the Ligurian Sea (Corsican-Ligurian-Provençal Basin), an area characterized also by upwelling. A reduction in both number and ecological diversity of cetacean taxa is observed along the Pliocene-Pleistocene transition; this trend, related to the onset of the Quaternary icehouse conditions, appears in good agreement with the recently recognized extinction event that affecting the marine megafauna at the end of the Pliocene.