An inorganic geochemical argument for coupled anaerobic oxidation of methane and iron reduction in marine sediments


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Sabine.Kasten [ at ] awi.de

Abstract

Here, we present results from sediments collected in the Argentine Basin, a non-steady state depositional marine system characterized by abundant oxidized iron within methane-rich layers due to sediment reworking followed by rapid deposition. Our comprehensive inorganic data set shows that iron reduction in these sulfate and sulfide-depleted sediments is best explained by a microbially mediated process—implicating anaerobic oxidation of methane coupled to iron reduction (Fe-AOM) as the most likely major mechanism. Although important in many modern marine environments, iron-driven AOM may not consume similar amounts of methane compared with sulfate-dependent AOM. Nevertheless, it may have broad impact on the deep biosphere and dominate both iron and methane cycling in sulfate-lean marine settings. Fe-AOM might have been particularly relevant in the Archean ocean, >2.5 billion years ago, known for its production and accumulation of iron oxides (in iron formations) in a biosphere likely replete with methane but low in sulfate. Methane at that time was a critical greenhouse gas capable of sustaining a habitable climate under relatively low solar luminosity, and relationships to iron cycling may have impacted if not dominated methane loss from the biosphere.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
34696
DOI 10.1111/gbi.12077

Cite as
Riedinger, N. , Formolo, M. J. , Lyons, T. W. , Henkel, S. , Beck, A. and Kasten, S. (2014): An inorganic geochemical argument for coupled anaerobic oxidation of methane and iron reduction in marine sediments , Geobiology . doi: 10.1111/gbi.12077


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