Glendonites track methane seepage in Mesozoic polar seas
Morales, C.; Rogov, M.; Wierzbowski, H.; Ershova, V.; Suan, G; Adatte, T.; Föllmi, K.B.; Tegelaar, E.; Reichart, G.-J.; de Lange, G.J.; Middelburg, J.J.; van de Schootbrugge, B. (2017). Glendonites track methane seepage in Mesozoic polar seas. Geology (Boulder Colo.) 45(6): 503-506. https://doi.org/10.1130/G38967.1 In: Geology. Geological Society of America: Boulder. ISSN 0091-7613; e-ISSN 1943-2682, more |  |
| Authors | | Top | - Morales, C.
- Rogov, M.
- Wierzbowski, H.
- Ershova, V.
| - Suan, G
- Adatte, T.
- Föllmi, K.B.
- Tegelaar, E.
| - Reichart, G.-J., more
- de Lange, G.J.
- Middelburg, J.J., more
- van de Schootbrugge, B.
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| Abstract | During the Phanerozoic, Earth has experienced a number of transientglobal warming events associated with major carbon cycle perturbations.Paradoxically, many of these extreme greenhouse episodesare preceded or followed by cold climate, perhaps even glacial conditions,as inferred from the occurrence of glendonites in high latitudes.Glendonites are pseudomorphs of ikaite (CaCO3·6H2O), a hydratedcarbonate mineral increasingly stable at low temperatures. Here,we show that methane seepage and oxidation provide an overridingcontrol on Mesozoic glendonite formation (i.e., ikaite fossilization).Geochemical and petrological analyses of 33 Early Jurassic to EarlyCretaceous glendonites from five sections in Siberia (Russia) revealthat most of their infilling carbonate phases are reminiscent of methane-derived authigenic carbonates. Bulk glendonites and surroundingsediments exhibit exceptionally high and low carbon isotope values(+20‰ to −45‰ VPDB [Vienna Peedee belemnite]), typical for carbonsources linked to methane generation and oxidation. Gas inclusiondata confirm the presence of methane and longer-chain hydrocarbongases, suggesting a thermogenic source for the methane. Glendonitebearinglayers can be traced for hundreds of kilometers, suggestingwidespread trapping of methane in the sub-seafloor during the Jurassic.As such, glendonites constitute an unexplored archive for detectingpast episodes of methane release and oxidation in polar settings. |
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