The Oloy floristic assemblage from the Cretaceous deposits of the Il’guveem river head, Northeastern Russia
The Oloy floristic assemblage comes from volcanic-sedimentary deposits of the Teleneut Unit, distributed in the Il’guveem river head, at the Oloy, Great Anuy and Yablon Rivers interfluve area. This area belongs to the Anadyr segment of the Okchotsk-Chukotka volcanic belt (Belyi, 1977). The Oloy floristic assemblage consists of 15 species. Equisetopsida: Equisetum sp. Polypodiopsida: Cladophlebis sp., Coniopteris sp., Tchaunia tchaunensis Samyl. et Philipp. Czekanowskiopsida: Phoenicopsis ex gr. angustifolia Heer. Cycadophytes: Heilungia oloensis Samyl. et Philipp., Taeniopteris sp., Pterophyllum sp. Ginkgoopsida: Ginkgo sp., Sphenobaiera sp. Pinopsida: Pagiophyllum zhuravlevii Golovn., Araucarites sp., Taxodium sp., Sequoia sp., Pityophyllum sp. Among them gymnosperms predominate. Angiosperms are not revealed. Cycadophytes are represented by three genera (Heilungia, Taeniopteris and Pterophyllum). Taxonomic composition of the Oloy floristic assemblage most closely resembles the composition of the Chaun flora, which comes from the Coniacian deposits of the Chaun Group of Central Chukotka. From 15 species of the Oloy assemblage 13 species are common with the Chaun ones (besides Taeniopteris иPterophyllum). Among common taxa there are the characteristic endemic plants of the Chaun flora: Tchaunia tchaunensis and Pagiophyllum zhuravlevii. The great systematic similarity of these floras indicate that they were even-aged and belonged to the single phytogeographic area – the Chukotka subprovince of the Mountain Okchotsk-Chukotka province (Golovneva, 2014b).