Calcareous nannoplankton zonation of the Cenomanian Stage in Central North Bulgaria

For the first time in this country calcareous nannoplankton zonation is made of the Upper Cretaceous rock. The subject of the study are nannofossils from the sediments of the Sanadinovo Marl Formation (Cenomanian) which outcrop along the Osâm river between the villages of Sanadinovo and Novačene Northeastern from Pleven. Three nannofossil zones are described: E. turriseiffeli Zone (Upper Albian-Lower Cenomanian), L. acutum Zone (Lower-Upper Cenomanian) and M. decoratus Zone (Upper Cenomanian).