Dinoflagellate assemblages and depositional environments of the Campanian Bearpaw formation, Alberta

Abstract

Twenty-nine genera and forty-five species of dinoflagellates were recorded from the Upper Cretaceous Bearpaw Formation at surface localities in the Rocky Mountain Foothills and in the southern Alberta Plains, near Calgary, Alberta. The diverse dinoflagellate assemblages indicate that the formation is Late Campanian in the plains and the foothills of southern Alberta. The maximum western extent of the Bearpaw Sea was in the Late Campanian. Stratigraphic trends in diversity and dominance of species in the assemblages are interpreted as indicating a relatively rapid initial transgression and a gradual final regression during the period of deposition. The results demonstrate the applicability of Late Cretaceous dinoflagellates for biostratigraphic determination and paleoenvironmental analysis in a marginal marine situation.