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

Details of the Early-Middle Frasnian boundary interval of the Pymvashor River section (Timan-Pechora Basin, Cis-Urals, in the far north of European Russia) are revealed by biostratigraphically constrained carbonate (d13Ccarb) and organic carbon (d13Corg) stable data. The studied interval corresponds to the lower part of the Domanik Formation, which consists of interbedded limestone and shale beds. Organic-rich black shale that lacks bioturbation and benthic organisms indicates 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 contains d13Ccarb and d13Corg isotope records related to the Early-Middle Frasnian isotope Event. The similarity between the Cis-Uralian (this study) and the Chinese d13Ccarb and d13Corg oscillations, including the twostep pattern of the recorded major positive excursions, suggests a robust correlation of the Late Devonian Early-Middle Frasnian isotope Event and minor intra-event excursions. Magnitude of variations and values of d13Corg and d13Ccarb in the punctata Zone in the Pymvashor River section are minor than those observed in the North American, Polish, and Chinese successions. Such difference may reflect specific variation of the local environments. [ABSTRACT FROM AUTHOR]