Nuovi dati stratigrafici e geocronologici sul Bacino di Leffe (Prealpi Lombarde, Bergamo)

Abstract

The stratigraphic succession of the Leffe Basin is assessed on the basis of a new coring, which reached the base of the basin infill. Five stratigraphic units have been distinguished. The bedrock consists of saprolite in porphyrite covered by slope deposits including pedoreiicts. The lower unit consists of a fan delta sequence of gravel, diamict and clay. Mainly biogenic sediments follow, which are referred to as middle (biogenic) unit. They are composed of lacustrine shell marl, brown coal and gyttja, which include mammal fauna and a rich microflora and macroflora. The upper part of the fill is composed by coarse fluviatile gravel and turbiditic abiotic lacustrine deposits, at the top of which a thick rubefied soil overlain by loess occurs. Paleontological data, together with the results of new paleomagnetic investigations, indicate an upper Pliocene and lowermost Pleistocene age for the Leffe sequence.