About the problem of the Middle-Upper Devonian boundary in the East European platform

A brief overview of the history of the identification of the Frasnian Stage (Upper Devonian) and the determination of its lower boundary in the stratotype region is presented. The characteristics of the Givetian-Frasnian boundary deposits in the East European platform and the stratigraphic significance of the regional event levels are considered. Debatable issues on the age definition of the boundary deposits are discussed; tasks for the further investigations are set.