Three Swedish borehole cores and three Danish outcrop sections, spanning the Upper Maastrichtian and Danian, have been analyzed for dinoflagellates. Variations in the relative abundances of certain dinoflagellate species have been used to establish a quantitatively defined, high-resolution zonation for the Upper Maastrichtian of southern Scandinavia. Relative abundance data and ranges of species have been combined in order to expand and refine the existing Danian dinoflagellate zonation. The results of these biostratigraphic studies suggest, in contrast to previous studies, that the C-T boundary layers are more completely developed in Sweden than in Denmark.

A detailed study of the Danish Fish Clay indicates that this layer is biostratigraphically older in eastern Denmark than in western Denmark. Also, the strong dominance of peridiniacean dinoflagellates in the Fish Clay in eastern Denmark suggests that the clay in eastern Denmark may be deposited in a low-salinity environment.

Four dinoflagellate variables and one planktonic foraminiferal variable are shown to respond to the regression that took place in the Upper Maastrichtian and are suggested to represent paleobathymetrical indices. They are used to investigate regional differences in water depth in the topmost Maastrichtian.

A description of the dinoflagellate flora is given. Seventeen new dinoflagellate species are described and illustrated. Also, an organic- walled dinoflagellate cyst is shown to represent the inner organic membrane of a calcareous dinoflagellate, which raises questions about the supra- generic classification of dinoflagellate cysts.