THE FIRST FIND OF CONODONTS IN ARVYAK FORMATION FROM URALTAU ZONE (SOUTH URALS)

Ordovician conodonts from the Arvyak Formation in the Southern Urals have been obtained for the first time. The conodonts are represented by Periodon aff. aculeatus Hadding, Staufferella? sp. and two conical elements. A scolecodont was found together with the conodonts. The Arvyak formation is part of the metamorphic Suvanyak complex of Uraltau zone and is dated to the Early Ordovician. The Arvyak Formation of the Uraltau zone is compared by authors with the Bakty Formation of the Yuryuzan structure and the Tirlyan-Kaginskaya strata of the West Zilair zone, which formed in the Ordovician in shallow-water shelf conditions along the eastern framing of the Bashkir anticlinorium. Biostratigraphic confirmation of the Ordovician age of the conglomerates and sandstones of the Arvyak Formation indicates a connection between part of the Ordovician deposits of the Uraltau zone and the eastern framing of the Bashkir anticlinorium. The Ordovician deposits of the Uraltau zone are facies represented by shallow-water shelf and deep-water deposits of the continental slope. The finding of conodonts in the deposits of the Arvyak formation allows us to change its age to Middle-Upper Ordovician and consider it an analogue of the Baktin formation and the Tirlyan-Kagin strata.