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Effects of oceanographic changes on controlling the stability of gas hydrates and the formation of authigenic carbonates at mud volcanoes and seepage sites on the Iberian margin of the Gulf of Cadiz

Magalhaes, V. H., Buffett, B., Archer, D., McGuire, P. C., Pinheiro, L. M. and Gardner, J. M. (2019) Effects of oceanographic changes on controlling the stability of gas hydrates and the formation of authigenic carbonates at mud volcanoes and seepage sites on the Iberian margin of the Gulf of Cadiz. Marine Geology, 412. pp. 69-80. ISSN 0025-3227

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To link to this item DOI: 10.1016/j.margeo.2019.03.002

Abstract/Summary

The Gulf of Cadiz is characterized by extensive active and inactive fluid escape structures which manifest as mud volcanoes, diapiric ridges, pockmarks and cold seeps. The high methane content and the presence of gas hydrates in the shallow sediments of the most active fluid escape structures indicate that these are areas of preferential migration and escape of fluids enriched in hydrocarbons and methane. Extensive fields of methane-derived authigenic carbonates are found at fluid escape structures along the upper and mid-continental slope, where the Mediterranean Outflow water is in direct contact with the seafloor, at water depths generally <1400 m. These methane-derived authigenic carbonates occur in much higher abundance at these shallower depths than in the fluid escape structures of the deeper (>1400 m) parts of the basin. The estimated U/Th ages of the authigenic carbonates, suggest that they were probably formed during discrete episodes of gas hydrate activity that may have occurred as a result of rapid climatic changes (such as the termination of the last glacial stage.) Numerical modelling indicates that seafloor temperature variations, associated with glacial/interglacial cycles and the changes of the Mediterranean Outflow pathway, could have restricted or eliminated the gas hydrate stability zone at the mud volcanoes shallower than 1400 m, resulting in intense fluxes of methane-rich fluids to the shallow sediments or even the seafloor. This fluid flux was recorded by the microbially mediated precipitation of authigenic carbonates.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Archaeology, Geography and Environmental Science > Department of Geography and Environmental Science
Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:83482
Publisher:Elsevier

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