Phytostratigraphic Scale of the Nonmarine Cretaceous of Northeast Asia: Attempts at Elaboration and Results

At the beginning of the 1970s, the paleobotanist V.A. Samylina published her concept of stratofloras: a stratigraphic scale of nonmarine Cretaceous deposits of Northeast Russia based on plant megafossils. This concept derived from the evolution of a systematic composition of plant communities upon the transition from Mesophyte to Cenophyte. Because the accuracy of this scale was similar to that for marine deposits, it almost instantaneously began to be used for the determination of the age and the correlation of continental deposits of the region. The paper considers the changes in views on the evolution of plant world of the region as new data arrive. It is shown that the elaboration of a common scale for the region is impossible, because the paleolandscape environments differed on this territory. The accuracy of scales for various parts of the region with similar paleolandscape conditions is lower than the stages of the General Stratigraphic Chart.