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Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans
Shen, B.; Dong, L.; Xiao, S.; Lang, X.; Huang, K.; Peng, Y.; Zhou, C.; Ke, S.; Liu, P. (2016). Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans. Nature Comm. 7(10317): 6 pp. hdl.handle.net/10.1038/ncomms10317
In: Nature Communications. Nature Publishing Group: London. ISSN 2041-1723, more
Peer reviewed article  

Available in  Authors 

Keyword
    Marine

Authors  Top 
  • Shen, B.
  • Dong, L.
  • Xiao, S.
  • Lang, X.
  • Huang, K.
  • Peng, Y.
  • Zhou, C.
  • Ke, S.
  • Liu, P.

Abstract
    Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (~2,5000-750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end.

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