Kedzydshor Formation and conodonts of the Lower Frasnian on the Izyayu River (South of the Tchernyshev Uplift)

Abstract

Research subject. Conodonts of the Lower Frasnian Kedzydshor Formation of the southern part of the Tchernyshev Uplift. Materials and methods. Materials obtained during a study of the section of the Kedzydshor Formation located on the Izyayu River were used. The biostratigraphic subdivision of the section was based on taxonomic definitions of conodonts and correlations with the Standard and Frasnian conodont zones. Results. In comparison with the stratotype of the Kedzydshor Formation, carbonate-argillaceous deposits cropping out on the Izyayu River are represented by fragments of the middle and upper parts of the Kedzydshor Formation in the stratigraphic range of the Lower falsiovalis Zone of the standard conodont zonation of the Lower Frasnian. The predominantly carbonate interval of the section is conventionally correlated with the FZ1 conodont zone, while the overlying terrigenous interval – with FZ2. The polygnatid and polygnatid-ancyrodellid conodont biofacies dominate in the section under study. Conclusions. New data on the distribution of cono donts across the Kedzydshor Formation in the Izyayu River section were obtained. The obtained data were compared with the local stratigraphic units of the Timan-North Urals Region. The Kedzydshor Formation is one of the most complete sequences of the Middle-Upper Devonian transition, thus representing the basis for searching and substantiating the position of the debatable lower boundary of the Frasnian Stage of the Upper Devonian.