Dinoflagellate cyst biogeography and biostratigraphy as a tool for palaeoceanographic reconstructions: An example from the Oligocene of western and northwestern Europe

The Last Occurrence (LO) pattern of the wetzelloid dinoflagellate cysts Wet zeliella symmetrica WEILER 1956, Wetzeliella gochtii COSTA & DOWNIE 1976, a nd Rhombodinium draco GOCHT 1955 in Early Oligocene sediments from western and northwestern Europe shows a strong diachronism. Oldest LOs are observed in the southern Dart of this region (i.e., in the Upper Rhine Graben and M ainz Embayment), wheras LOs in the Northwest European Tertiary Basin are yo unger. This diachronism is interpreted to reflect palaeoenvironmental and p alaeoceanographic changes within the seaway connecting the Tethys with the Northwest European Tertiary Basin. The dependence of W. symmetrica, W. goch tii, and R. draco LOs on regional palaeoenvironmental conditions demonstrat es the need to analyze the palaeoecology of fossil dinoflagellate cysts pri or to using them for long-distance correlations.