Middle–Upper Ordovician Acritarchs from Baltoscandia (Lisino-10 Borehole, Leningrad Region) and Their Biostratigraphic Implication

The results of a study of acritarch taxonomic diversity and stratigraphic distribution in the Middle-Upper Ordovician deposits from the Lisino-10 borehole in the west of the Leningrad Region are presented. Six successive acritarch assemblages have been established in the interval of the upper Dapingian–lower half Sandbian Ordovician stages. New data make it possible to link the results of previously studied sections of the Lower–Middle Ordovician of the Moscow Syneclise and the Leningrad Region with sections of the Middle–Upper Ordovician of Estonia. This provides the basis for compiling a complete stratigraphic sequence of the Ordovician acritarch assemblages of Baltoscandia. Three new genera and five new species characteristic of the Sandbian Stage of the Upper Ordovician are described. They are: Lititzina cornuta gen. et sp. nov., Paniculaferum prodigiosum sp. nov., Sandbica clavata gen. et sp. nov., Sandbica ornata gen. et sp. nov., and Tadasum florigerum gen. et sp. nov.