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

Abstract

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 (δ13Ccarb) and organic carbon (δ13Corg) 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 δ13Ccarb and δ13Corg isotope records related to the Early-Middle Frasnian isotope Event. The similarity between the Cis-Uralian (this study) and the Chinese δ13Ccarb and δ13Corg 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 δ13Corg and δ13Ccarb 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.

Drowning, extinction, and subsequent facies development of the Devonian Hönne Valley Reef (northern Rhenish Massif, Germany)

“…nonaginta Group. Most recently, Kotik et al (2021) used the generic name "Lagovina" (not Lagovidina, a Famennian prioniodinid genus), which appears to be a nom. nud.…”

Interregional Correlation of the Middle Frasnian (Upper Devonoian) of the North-West of the Russian Plate and the East of the Pechora Plate: An Ecogeochemical Aspect

“…Коллекция конодонтов, характеризующая относи тельно глубоководные доманикоидные фации домани кового горизонта франского яруса востока Печорской плиты, «происходит» из опорного разреза на р. Пымва шор (север гряды Чернышева) [Kotik et al, 2021] (см. рис.…”

“…Биостратиграфические построения, использованные в настоящей работе, были подробно изложены ранее в работах [Zhuravlev et al, 2006;Kotik et al, 2021;Zhuravlev, 2021a]. В качестве биостратиграфической основы использованы зоны по конодонтам, выделенные в МонтаньНуар [Klapper, 1988[Klapper, , 1997.…”

“…Информация по распределению изотопного состава углерода конодонтов в среднем фране севера гряды Чернышева приведена по [Kotik et al, 2021] с дополнением новыми данными для верхней части разреза. Анализ этой информации показал облегчение изотопного состава до -27.0 ‰ в пограничном нижнесредне франском интервале (верхи зоны MN4) с последующим утяжелением до -26.2 ‰ в нижней части зоны punctata (зона MN5) (рис.…”