TY - JOUR

T1 - Early Ediacaran Positive C-Isotope Anomaly in Limestones of the Chernaya Rechka Formation, Igarka Uplift (Northwestern Siberian Platform)

AU - Kochnev, B. b.

AU - Pokrovsky, B. g.

AU - Kuznetsov, A. b.

AU - Marusin, V. v.

AU - Kaurova, O. k.

AU - Bykova, N. v.

AU - Ivanova, N. a.

N1 - Field works and chemical study of the rocks were supported by the Russian Foundation for Basic Research (project nos. 17-05-00418 and 20-05-00101). The study of carbon and oxygen isotope composition was supported by the Russian Science Foundation (project no. 20-77-10 066). The isotope composition of organic carbon and strontium was studied in the framework of the government-financed tasks (FMMG-2022-0002, FMUW-2021-0003, and FWZZ-2022-0002). Data generalization and manuscript preparation were made with support of the Russian Science Foundation (22-77-10 096). Публикация для корректировки.

PY - 2023/6

Y1 - 2023/6

N2 - The Precambrian Chernaya Rechka Formation (Igarka Uplift) hosts a high-amplitude positive carbonate carbon and dispersed organic matter δ13С isotope anomaly (up to +12.4‰) spanning over 500 m of the section. Variations of δ13Сcarb and δ13Сorg are synchronous and do not depend on local sedimentary environments, since the studied anomaly-bearing carbonates were accumulated in different zones of the carbonate ramp. The oxygen isotope composition of these carbonates and other geochemical criteria indicate an insignificant impact of postsedimentary processes on the preservation of isotope systems. Variations of trace elements in the carbonate fraction from the stratotype section of the Chernaya Rechka Formation indicate its accumulation in alternating anoxic and oxic environments that did not affect the carbon isotope composition. It is shown that the limestones, which outcrop on Plakhinskii Island and contain widespread molar-tooth structures, also belong to the Chernaya Rechka Formation in terms of the chemical and isotope composition. The profound positive δ13С anomaly was putatively caused by a global deficiency of 12С in the paleo-ocean related to the accumulation of methane hydrates and the burial of nonoxidized organic matter. Together with the geochronological and stratigraphic data, minimum 87Sr/86Sr values (0.7074) in the Chernaya Rechka Formation reveal the lower Ediacaran (lower Vendian) age of the unit (635–580 Ma). Among the closest stratigraphic analogues of the Chernaya Rechka Formation are the Dal’nyaya Taiga Group (Patom Basin) and coeval stratigraphic sequences in the southern Siberian Platform. The global nature of the positive δ13С anomaly provides its correlation with other coeval C-isotope events worldwide.

AB - The Precambrian Chernaya Rechka Formation (Igarka Uplift) hosts a high-amplitude positive carbonate carbon and dispersed organic matter δ13С isotope anomaly (up to +12.4‰) spanning over 500 m of the section. Variations of δ13Сcarb and δ13Сorg are synchronous and do not depend on local sedimentary environments, since the studied anomaly-bearing carbonates were accumulated in different zones of the carbonate ramp. The oxygen isotope composition of these carbonates and other geochemical criteria indicate an insignificant impact of postsedimentary processes on the preservation of isotope systems. Variations of trace elements in the carbonate fraction from the stratotype section of the Chernaya Rechka Formation indicate its accumulation in alternating anoxic and oxic environments that did not affect the carbon isotope composition. It is shown that the limestones, which outcrop on Plakhinskii Island and contain widespread molar-tooth structures, also belong to the Chernaya Rechka Formation in terms of the chemical and isotope composition. The profound positive δ13С anomaly was putatively caused by a global deficiency of 12С in the paleo-ocean related to the accumulation of methane hydrates and the burial of nonoxidized organic matter. Together with the geochronological and stratigraphic data, minimum 87Sr/86Sr values (0.7074) in the Chernaya Rechka Formation reveal the lower Ediacaran (lower Vendian) age of the unit (635–580 Ma). Among the closest stratigraphic analogues of the Chernaya Rechka Formation are the Dal’nyaya Taiga Group (Patom Basin) and coeval stratigraphic sequences in the southern Siberian Platform. The global nature of the positive δ13С anomaly provides its correlation with other coeval C-isotope events worldwide.

KW - Ediacaran

KW - Igarka Uplift

KW - Siberian Platform

KW - Vendian

KW - chemostratigraphy

KW - stable isotope geochemistry

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85160055061&origin=inward&txGid=528ec2788a4c862b516f3c10b50e0808

UR - https://www.mendeley.com/catalogue/e3e42f54-930b-3910-be67-7fb6d94a701c/

U2 - 10.1134/S0024490223700086

DO - 10.1134/S0024490223700086

M3 - Article

VL - 58

SP - 235

EP - 257

JO - Lithology and Mineral Resources

JF - Lithology and Mineral Resources

SN - 0024-4902

IS - 3

ER -