Main biotic and climatic events in Early Permian of the Western Urals, Russia, as exemplified by the shallow-water biota of the early Kungurian lagoons

Abstract

The paper deals with the Early Permian (mostly early Kungurian) biotas of the Cis-Urals (Perm region, Russia). Taxonomic composition of the early Kungurian biota of the stratotype area (close vicinity of the City of Kungur) includes algae Algites philippoviensis Naugolnykh, A. shurtanensis Naugolnykh, tracheophytes (higher plants), i.e., equisetophytes Paracalamites spp., conifers Shaidurodendron columnaris Naugolnykh, Walchia appressa Zalessky, vojnovskyaleans Rufloria derzavinii (Neuburg) S. Meyen etc.; invertebrates: coelenterates of uncertain affinity, bivalves Permophorus costatus (Brown), Permophorus sp., Netschajewia sp. cf. N. tschernyshowi (Licharew), gastropods Goniasma angulata (Stuckenberg), terebratulid brachiopods Dielasma sp. cf. D. moelleri Tschernyschew, arthropods (limulids Paleolimulus kunguricus Naugolnykh); vertebrates: chondrichthyan and actinistian fishes.Paleogeographically, the studied area belonged to the near-shore zone of a large lagoon basin disposed along the western-southern part of the Paleo-Urals during the Kungurian time. The main events in evolution of this basin reflect the final phases of the Artinskian sea basin with normal salinity, the transition to an early Kungurian (Philippovian) lagoon, then the appearance of intercalations of evaporate conditions and episodic incursion of marine faunas, and finally a gradual transition to semi-terrestrial environments with the cyanophyte communities in early Ufimian (Solikamskian, early Roadian) time. Climatic conditions in this area changed from semi-humid to semi-arid. A new genus and species of algae Dichothallus divaricatus Naugolnykh n. gen. n. sp. is described on the basis of material originated from the stratotype of the Philippovian Horizon of the Kungurian stage, Lower Permian.