Carbon isotope evidence for large methane emissions to the Proterozoic atmosphere

Type Article
Date 2020-10
Language English
Author(s) Cadeau Pierre1, Jézéquel Didier1, Leboulanger Christophe2, Fouilland Eric4, Le Floc’h Emilie4, Chaduteau Carine1, Milesi Vincent1, Guélard Julia1, Sarazin Gérard1, Katz Amandine1, D’amore Sophie1, Bernard Cecile3, Ader Magali1
Affiliation(s) 1 : Université de Paris, Institut de physique du globe de Paris, CNRS, 75005, Paris, France
2 : MARBEC Sète, France, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France
3 : UMR 7245 MCAM, Muséum National D’Histoire Naturelle - CNRS, Paris, France
4 : MARBEC Sète, France, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France
Source Scientific Reports (2045-2322) (Springer Science and Business Media LLC), 2020-10 , Vol. 10 , N. 1 , P. 18186 (13p.)
DOI 10.1038/s41598-020-75100-x
WOS© Times Cited 5
Abstract

The Proterozoic Era records two periods of abundant positive carbon isotope excursions (CIEs), conventionally interpreted as resulting from increased organic carbon burial and leading to Earth’s surface oxygenation. As strong spatial variations in the amplitude and duration of these excursions are uncovered, this interpretation is challenged. Here, by studying the carbon cycle in the Dziani Dzaha Lake, we propose that they could be due to regionally variable methane emissions to the atmosphere. This lake presents carbon isotope signatures deviated by ~  + 12‰ compared to the modern ocean and shares a unique combination of analogies with putative Proterozoic lakes, interior seas or restricted epireic seas. A simple box model of its Carbon cycle demonstrates that its current isotopic signatures are due to high primary productivity, efficiently mineralized by methanogenesis, and to subsequent methane emissions to the atmosphere. By analogy, these results might allow the reinterpretation of some positive CIEs as at least partly due to regionally large methane emissions. This supports the view that methane may have been a major greenhouse gas during the Proterozoic Era, keeping the Earth from major glaciations, especially during periods of positive CIEs, when increased organic carbon burial would have drowned down atmospheric CO2.

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Cadeau Pierre, Jézéquel Didier, Leboulanger Christophe, Fouilland Eric, Le Floc’h Emilie, Chaduteau Carine, Milesi Vincent, Guélard Julia, Sarazin Gérard, Katz Amandine, D’amore Sophie, Bernard Cecile, Ader Magali (2020). Carbon isotope evidence for large methane emissions to the Proterozoic atmosphere. Scientific Reports, 10(1), 18186 (13p.). Publisher's official version : https://doi.org/10.1038/s41598-020-75100-x , Open Access version : https://archimer.ifremer.fr/doc/00656/76784/