Early-Middle Frasnian (Late Devonian) carbon isotope Event in the Timan-Pechora Basin (Chernyshev Swell, Pymvashor River section, North Cis-Urals, Russia)

Biostratigraphically constrained carbonate (δ¹³C_carb) and organic carbon (δ¹³C_org) variations in the Early-Middle Frasnian boundary interval in the Pymvashor River section (Timan-Pechora Basin, Cis-Urals, in the far north of European Russia) were considered. The studied interval of section is represented by the lower part of the Domanik Formation (Fm.) comprising alternations of limestones and shales. The presence of organic-rich black shales and the absence of bioturbation and benthic organisms indicate an oxygen-depleted depositional environment. Detection of isorenieratene derivatives in organic matter indicates that anoxia was present in the photic zone during deposition. The Pymvashor River section demonstrates clear manifestation of the two-fold Mid-Frasnian isotope Event in both δ¹³C_carb and δ¹³C_org isotope records. Similarity between the Cis-Uralian and Chinese δ¹³C_carb oscillations, including the two-step pattern of major positive excursions, suggests high correlative potential for the Late Devonian ‘punctata Event’ and minor intra-event excursions. Positive trends in carbon isotope composition of organic matter in conodont elements in the transitans-punctata interval is distinguished in the Pymvashor section. This carbon isotope pattern is similar to that of bulk δ¹³C_org in the Appalachian Basin and may prove to be a useful stratigraphic marker.