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ISOTOPIC AGE DETERMINATION OF ZIRCON FROM TUFFS FORMARTION OF THE TSAGAYAN GROUP STRATOTYPE (AMUR REGION, CRETACEOUS-PALEOGENE BOUNDARY)

Any study of the boundaries of stratigraphic units in continental sequences always encounters difficulties. A sample was taken from a stratotype of the Tsagayan formation and a typical locality of the Tsagayan flora in the Amur region from crystalloclastic tuffs at the Cretaceous-Paleogene boundary to study zircon and determine its absolute age. The age of the zircons from tuffs was estimated as 68.6 ± 0.8 Ma by the lower intersection with the concordia and can be considered as close to the rock sedimentation time.