The late Devonian Upper Kellwasser event in the deep-water deposits of the western slope of the Subpolar Urals (Kozhym river section)

The Upper Kellwasser Event is recognized for the first time in the deep-water succession of the Kozhym River section on the Western slope of the Subpolar Urals, based on conodont biostratigraphy, lithological changes and positive shifts of the carbon isotope value (d13C) across the Frasnian-Famennian (F-F) boundary interval. Conodonts are abundant in the Frasnian Upper rhenana Subzone, but show a low diversity at the level of transgressive Upper Kellwasser Event in the linguiformis Zone, and are almost absent in the Famennian subperlobata Zone. Black shale horizons associated with the global Upper Kellwasser Event were identified in the linguiformis Zone in the Kozhym River section. Positive shifts in the carbon isotope ratio during the linguiformis Zone to the Lower triangularis Subzone (lower part) are observed, similar to those reported from elsewhere around the world (positive d13Ccarb shifts ~ from 3 to 4 ‰). The data obtained allow the black shales associated with the Upper Kellwasser Event and carbon isotope fluctuations to be precisely dated and correlated.