The late cretaceous flora from volcanogenic deposits of northern Priokhotie (The Okhotsk-Chukotka volcanogenic belt)

Abstract

Assemblage of fossil plants from the Gydra, Yum and Kananyga Formations (the Villigha and Toomahni Rivers interfluve, Okhotsk-Chukotka volcanogenic belt) are joined in the Aleeki flora. The systematic description of main species is given and floristic and phytostratigraphical analysis of this flora is carried out. New species Lobifolia alikensis Golovn. et Shczep. is described. The Aleeki flora is typical flora of the Okhotsk-Chukotka volcanogenic belt. It contain few angiosperms and significant amount relic elements among ferns (Hausmannia, Lobifolia), cycadophytes (Heilungia), czekanowskiales (Phoenicopsis) and ginkgoales (Sphenobaiera, Ginkgo ex gr. sibirica). In consequence of its stratigraphical position the Aliky flora is slightly younger than the Chingandzha flora (the Turonian-Coniacian) and it is compositionally similar with the Chaun flora (Coniacian). On this basis the age of the Aleeki flora is estimated as the Coniacian. The common taxa of the Aleeki and Chingandzha floras are Coniopteris tschuktschorum, Asplenium dicksonianum, Cladophlebis inaequipinnulata, Birisia sp., Ginkgo ex gr. adiantoides, G. ex gr. sibirica, Sequoia, Metasequoia, Menispermites, Dalembia and Trochodendroides. The common genera of the Aleeki and Chaun floras are Coniopteris, Asplenium, Arctopteris, Cladophlebis, Ginkgo, Sphenobaiera, Heilungia, Phoenicopsis, Picea, Sequoia, Metasequoia, Menispermites, Dalembia and Trochodendroides. Besides that the Aleeki flora contains some species, which were believed as endemic of the Chaun flora: Tchaunia lobifolia, Cladophlebis grandis and Araucarites subacutensis. The Aleeki and Chaun floras are now considered as contemporaneous regional floras, which were distributed in the northern part of the Okhotsk-Chukotka volcanogenic belt.

The composition and age of the Ul’ya flora (Okhotsk-Chukotka volcanic belt, North-East of Russia): paleobotanical and geochronological constraints

“…These floras are most reliably dated by both paleobotanical and isotopic data (Kelley et al 1999, Akinin & Miller 2011. In the last few years, new paleobotanical data were published also for the Aliki, Chingandzha, Kholochovchan, Yana, Zarya, Ust'-Emuneret and Kholchan floristic assemblages (Shczepetov & Golovneva 2010, 2014, Moiseeva 2014.…”

“…The results of these methods were imprecise and often contradictory. The Cretaceous floras of the OCVB significantly differ from the contemporaneous floras of adjacent coastal lowlands along the eastern margin of the volcanic belt (Philippova & Abramova 1993, Shczepetov & Golovneva 2010, Herman 2013. The OCVB floras were formed in montane environments and are marked by high endemism, predominance of ferns and conifers, a minor share of angiosperms, and considerable numbers of Early Cretaceous relicts in all plant groups.…”