LATE EOCENE TO EARLY OLIGOCENE DINOFLAGELLATE CYSTS FROM THE PRIABONIAN TYPE-AREA (NORTHEAST ITALY) - BIOSTRATIGRAPHY AND PALEOENVIRONMENTAL INTERPRETATION

Marginal marine Late Eocene through Early Oligocene dinoflagellate cyst successions have been studied from the type area of the Priabonian Stage (northeast Italy). The results allow the recognition of dinoflagellate zones previously defined in bio- and magnetostratigraphically well-calibrated pelagic sequences from central Italy, thus providing a first order correlation of the Priabonian Stage to the standard chronostratigraphic scale with unprecedented precision. Within this detailed biostratigraphic framework, successive shifts in the composition of the dinoflagellate cyst assemblages are interpreted in terms of sea-level and sea-surface temperature (SST) fluctuations. The evaluation of ecologically and sedimentary controlled changes in the composition of dinoflagellate cyst assemblages, in combination with sequence stratigraphic analysis, allows the reconstruction of ''third'' and ''fourth'' order sea-level fluctuations. The third-order sea-level fluctuations appear to correspond to ''Exxon'' cycles TA4.1-4.5. The stratigraphically and palaeoenvironmentally important Late Eocene dinoflagellate cyst species Glaphyrocysta priabonensis sp. nov. is formally described.