The malacological record from the Plio-Pleistocene Leffe Basin (Bergamo, Northern Italy)

The Plio-Pleistocene Leffe Basin (Southern Alps, north of Bergamo) has been the object of malacological studies since the 19th century. The present work represents the first extensive analysis of the molluscan assemblages recorded in the Leffe Formation. Two exposed sections and a drilled core crossing the entire sedimentary succession have been investigated. Mollusc remains are found in shell–marls and gyttja. Brown coal layers lack molluscs. The molluscan fauna, dominated by freshwater prosobranchs, heterobranchs and pulmonates, proved to be significant for palaeoenvironmental and biostratigraphical reconstructions of palustrine–lacustrine environments subject to oscillations in water deepness and changing sediment deposition through time. Alternating warming and cooling climate phases are also recognized. The molluscan assemblages, represented mostly by modern species, reveal European affinity. The occurrence of a biostratigrafically significant extinct freshwater species confirmed the chronostratigraphical attribution of the “biogenic unit” of the Leffe Formation to the Early Pleistocene, in accordance with other palaeontological (vertebrates and pollen) and magnetostratigraphical data.