Maastrichtian-Paleocene floras of Northeastern Russia and north Alaska and floral changes at the Cretaceous-Paleogene boundary

Taphofloras of the Koryak Upland and the Sagwon Locality of North Alaska are described in terms of their taxonomic composition, stratigraphic ranges, and comparison with coeval floras of Northeastern Russia and Alaska. Causes and amplitude of changes in Arctic floras across the Cretaceous-Paleogene boundary are considered. In its aspect and taxonomic composition, the Late Maastrichtian flora of the Amaam Lagoon (the Koryak Upland) is very close to the early Paleocene Sagwon flora of North Alaska. This is inconsistent with a hypothesis of the global ecological crisis at the Cretaceous-Paleogene boundary. Development of floras was controlled by long-term climatic fluctuations and by evolution and migration of plants