Late Cretaceous Flora of the Zyryanka Coal Basin in Northeastern Russia: Composition, Age, and Plant Communities

Plant fossils collected by O.V. Grinenko on the right bank of the Vstrechnaya River in the Zyryanka coal basin (Northeastern Russia) in 1989 have been studied. The Vstrechnaya taphoflora includes 25 species of fossil plants assigned to ferns, cycadaleans, ginkgoaleans, leptostrobaleans, conifers, gymnosperms of an uncertain systematic position, and angiosperms. The presence of advanced conifer taxa and angiosperm plants in the Vstrechnaya taphoflora enables the determination of its age as Late Cretaceous, most probably Turonian and Coniacian. The significant difference between the Vstrechnaya floristic assemblage, as well as the Vstrechnaya flora as a whole, and the Buor-Kemus Formation flora enabled us to regard the plant-bearing sediments as an independent local stratigraphic unit, the Vstrechnaya Formation. The Vstrechnaya taphoflora includes plants that probably formed distinct Mesophytic and Cenophytic plant communities. The composition of the former was inherited from the more ancient, Early Cretaceous, floras of the region; the latter include advanced conifer taxa and angiosperm plants and thus reflect the gradual invasion of the evolutionarily new Late Cretaceous vegetation into the continental interior of Northeastern Asia.