Sulfate-methane interface

The biogenic methane is generated from anaerobic degradation, accompanied by a sulfate-methane interface (SMI), which can be used to determine the upper boundary of hydrate formation depth (Pauli et al., 2005). 

Figure 7.6 Samples from ODP Leg 164 Hole 994 at Blake Bahama Ridge, showing the sub-bottom reduction in sulfate until the depth of the Sulfate-Methane Interface (SMI), and the increase in methane concentrations below the SMI. (Pauli, Personal Communication, October 25, 2001.)...

Fig. 14.22 Schematic illustration of gas hydrate deposits and biogeochemical reactions in near-surface sediments on southern Hydrate Ridge. High gradients in pore water sulfate and methane are typical of methane hydrate-rich environment close to sulfate-rich seawater. At the sulfate-methane interface (also named sulphate-methane transition in earlier chapters of the book) a microbial consortium of methanothrophic archaea and sulfate-reducing bacteria (Boetius et al. 2000) perform anaerobic oxidation of methane (AOM) leading to carbonate precipitation. AOM rates influence hydrogen sulfide fluxes and gradients, which are reflected on the seafloor by the distribution of vent communities around active gas seeps and gas hydrate exposures (Sahling et al. 2002).

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