Èзó÷åí óãëåвîдîðîдíый ñîñòàв îðãàíè÷åñкîãî вåщåñòвà дîìàíèкîвых îòëîжåíèй èз åñòåñòвåííых выхîдîв íà ð. Пыìвàшîð в ñåвåðíîй ÷àñòè ãðяды Чåðíышåвà. Пîкàзàíы ðàзëè÷èя в ðàñпðåдåëåíèè óãëåвîдîðîдîв-бèîìàðкåðîв в зàвèñèìîñòè îò ëèòîëîãè÷åñкîãî ñîñòàвà пîðîд è óñëîвèй íàкîпëåíèя îðãàíè÷åñкîãî вåщåñòвà. Бèòóìîèды èзвåñòкîвèñòых àðãèëëèòîв îòëè÷àюòñя пðîфèëåì ðàñпðåдåëåíèя í-àëкàíîв (ìàкñèìóì пðè n-С 13-n-С 18), пîвышåííыì îòíîшåíèåì Pr/ Ph è пîвышåííыìè ñîдåðжàíèяìè ãîпàíîв. Êàòàãåíåòè÷åñкàя пðåîбðàзîвàííîñòь îðãàíè÷åñкîãî вåщåñòвà, îöåíåííàя пî дàííыì ñòåðàíîвых, ãîпàíîвых è àðîìàòè÷åñкèх óãëåвîдîðîдîв, ñîîòвåòñòвóåò ñåðåдèíå ãëàвíîй зîíы íåфòåãåíåðàöèè (R o ~ 0.6-0.75 %). Дàííый óðîвåíь кàòàãåíåзà òàкжå пîдòвåðждàåòñя èíдåкñàìè îкðàñкè кîíîдîíòîвых эëåìåíòîв (ÈОÊ 2.5-3). Ó÷èòывàя íåîдíîðîдíîñòь ðàñпðåдåëåíèя бèîìàðкåðîв, ãåíåðèðîвàííыå îðãàíè÷åñкèì вåщåñòвîì дîìàíèкîвых îòëîжåíèй íåфòяíыå óãëåвîдîðîды бóдóò îбëàдàòь ðàзëè÷íыìè пàðàìåòðàìè. Ключевые слова: гðяäà Чåðíышåвà, îðгàíè÷åскîå вåщåствî, äîìàíèкîвый гîðèçîíт, бèîìàðкåðы.

No 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.

––The study area is located within the Chernyshev Ridge, a fold–thrust structure, which is a promising area for oil and gas exploration in the Timan–Pechora province. Petroleum source rocks of Paleozoic (from Upper Ordovician to lower Carboniferous) deposits stripped by the Vorgamusyurskaya-1 well in the Tal’bei block of the Chernyshev Ridge were studied by lithological, petrographic, organic-petrology, and organic-geochemistry methods. Most of the section is characterized by low values of Corg (<0.5%), genetic potential (S1 + S2 < 0.5 mg HC/g rock), and hydrogen index (HI < 100 mg HC/g Corg). Petroleum source rocks with elevated values of Corg (up to 0.9%), S1 + S2 (up to 2.1 mg HC/g rock), and HI (up to 277 mg HC/g Corg) were identified at different stratigraphic levels of the section: Upper Devonian (D3tm–sr), upper Silurian (S2gj), and Upper Ordovician (O3mt). The maceral composition of organic matter (OM) and the distribution of hydrocarbons in the saturated fraction of bitumens indicate that petroleum source rocks include only marine OM (type II kerogen). The degree of catagenesis of OM was estimated based on the bituminite reflectance (RVeq), Rock-Eval pyrolysis (Tmax), and conodont color alteration index (CAI). The available RVeq (0.63–0.84%), Tmax (430–443 °C), and CAI (1.5–2.0) data indicate that the entire Paleozoic well section is in the oil window (MC1–MC3). The new data refined the catagenetic zoning of the sedimentary section, according to which the OM reached the following gradations: MC1 in the lower Carboniferous and Famennian deposits, MC2 in the interval from the Frasnian to the upper part of the lower Silurian, and MC3 in the lower part of the lower Silurian and in the Upper Ordovician. The results of the study of petroleum source rocks and the type and maturity of OM will be the basis for basin modeling, which will increase the reliability of reconstructions of oil and gas formation at the Chernyshev Ridge.