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 cys t successions have been studied from the type area of the Priabonian S tage (northeast Italy). The results allow the recognition of dinoflage llate zones previously defined in bio- and magnetostratigraphically we ll-calibrated pelagic sequences from central Italy, thus providing a f irst order correlation of the Priabonian Stage to the standard chronos tratigraphic scale with unprecedented precision. Within this detailed biostratigraphic framework, successive shifts in the composition of th e dinoflagellate cyst assemblages are interpreted in terms of sea-leve l and sea-surface temperature (SST) fluctuations. The evaluation of ec ologically and sedimentary controlled changes in the composition of di noflagellate cyst assemblages, in combination with sequence stratigrap hic analysis, allows the reconstruction of ''third'' and ''fourth'' or der sea-level fluctuations. The third-order sea-level fluctuations app ear to correspond to ''Exxon'' cycles TA4.1-4.5. The stratigraphically and palaeoenvironmentally important Late Eocene dinoflagellate cyst s pecies Glaphyrocysta priabonensis sp. nov. is formally described.