Anaerobic oxidation of methane in a cold-water coral carbonate mound from the Gulf of Cadiz

• Published in: International journal of earth sciences : Geologische Rundschau Vol. 100; no. 6; pp. 1413 - 1422
• Main Authors: Maignien, L., Depreiter, D., Foubert, A., Reveillaud, J., De Mol, L., Boeckx, P., Blamart, D., Henriet, J.-P., Boon, N.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-09-2011; Springer Nature B.V; Springer Verlag
• Subjects: Biodiversity and Ecology; Coral reefs; Dissolved inorganic carbon; Earth and Environmental Science; Earth Sciences; Environmental Sciences; Escarpments; Geochemistry; Geology; Geophysics/Geodesy; Marine; Methane; Mineral Resources; Mounds; Ocean floor; Original Paper; Oxidation; Sedimentology; Structural Geology; Sulfate reduction; Sulfates; Sulfides; Transition zone; Volcanic fields; Volcanoes; Gulf of Cadiz; ANE, Atlantic, Cadiz Gulf; Cold-water carbonate mound; Methane; Anaerobic oxidation of methane; Gulf of Cadiz
• ISSN: 1437-3254; 1437-3262
• DOI: 10.1007/s00531-010-0528-z

The Gulf of Cadiz is an area of mud volcanism and gas venting through the seafloor. In addition, several cold-water coral carbonate mounds have been discovered at the Pen Duick escarpment amidst the El Arraiche mud volcano field on the Moroccan margin. One of these mounds -named Alpha mound- has been studied to examine the impact of the presence of methane on pore-water geochemistry, potential sulphate reduction (SR) rate and dissolved inorganic carbon (DIC) budget of the mound in comparison with off-mound and off-escarpment locations. Pore-water profiles of sulphate, sulphide, methane, and DIC from the on-mound location showed the presence of a sulphate to methane transition zone at 350 cm below the sea floor. This was well correlated with an increase in SR activity.
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C-depleted DIC at the transition zone (−21.9‰ vs. Vienna Pee Dee Belemnite) indicated that microbial methane oxidation significantly contribute to the DIC budget of the mound. The Alpha mound thus represents a new carbonate mound type where the presence and anaerobic oxidation of methane has an important imprint on both geochemistry and DIC isotopic signature and budget of this carbonate mound.