Integrated Biostratigraphy of Eocene Deposits in the Gubs Section (Northern Caucasus) with special Attention to the Ypresian/Lutetian Boundary and to the Peritethyan-Tethyan Correlation

Zakrevskaya, Elena; Beniamovsky, V. N.; Less, György; Báldi-Beke, Mária

doi:10.3906/yer-1005-4

Cited by 2 publications

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“…1). The studied section contains a succession of middle-late Eocene sediments divided into the Cherkessk, Keresta, Kuma, and Belaya Glina Formations (Zakrevskaya et al, 2011;Beniamovski, 2012), which were deposited in a continental shelf setting (van der Boon et al, 2019). Here, we defined the base of the section (0 m) as the sharp transition from the green clays of the Cherkessk Formation to the white marls of the Keresta Formation (Fig.…”

Section: Geological Setting and Stratigraphymentioning

confidence: 99%

Deoxygenation and organic carbon sequestration in the Tethyan realm associated with the middle Eocene climatic optimum

et al. 2022

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The middle Eocene climatic optimum (ca. 40 Ma) stands out as a transient global warming phase of ∼400 k.y. duration that interrupted long-term Eocene cooling; it has been associated with a rise in atmospheric CO2 concentrations that has been linked to a flare-up in Arabia-Eurasia continental arc volcanism. Increased organic carbon burial in the Tethys Ocean has been proposed as a carbon sequestration mechanism to bring the middle Eocene climatic optimum to an end. To further test these hypotheses, we assessed the sedimentary and geochemical expression of the middle Eocene climatic optimum in the northern Peri-Tethys, specifically, the organic-rich Kuma Formation of the Belaya River section, located on the edge of the Scythian Platform in the North Caucasus, Russia. We constructed an age-depth model using nannofossil chronobiostratigraphy. Throughout the studied middle Eocene interval (41.2−39.9 Ma), we documented sea-surface temperatures of 32−36 °C based on the tetraether index of tetraethers consisting of 86 carbons (TEX86), depending on proxy calibration, and during the early middle Eocene climatic optimum, we observed sea-surface warming of 2−3 °C. Despite the proximity of the section to the Arabia-Eurasia volcanic arc, the hypothesized source of volcanic CO2, we found no evidence for enhanced regional volcanism in sedimentary mercury concentrations. Sedimentary trace-element concentrations and iron speciation indicate reducing bottom waters throughout the middle Eocene, but the most reducing, even euxinic, conditions were reached during late middle Eocene climatic optimum cooling. This apparent regional decoupling between ocean warming and deoxygenation hints at a role for regional tectonics in causing basin restriction and anoxia. Associated excess organic carbon burial, extrapolated to the entire regional Kuma Formation, may have been ∼8.1 Tg C yr−1, comprising ∼450 Pg C over this ∼55 k.y. interval. Combined with evidence for enhanced organic carbon drawdown in the western Peri-Tethys, this supports a quantitatively significant role for the basin in the termination of the middle Eocene climatic optimum by acting as a large organic carbon sink, and these results collectively illustrate that the closing Tethys Ocean might have affected global Paleogene climate. Moreover, this study highlights the importance of the interplay between global climate and regional oceanic gateway evolution in determining local climate and oceanographic change.

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Section: Geological Setting and Stratigraphymentioning

confidence: 99%