THE POSSIBLE FORMATION OF MAGNETIC ANOMALIES VIA METHANE-FUELED SULFATE REDUCTION AT A THERMOGENIC METHANE SEEP
We further hypothesize that sulfate reduction at this site is driven by microbially mediated anaerobic methane oxidation (AMO), whereby CH4 serves as the electron source and sulfate as the ultimate electron acceptor. Several studies in marine settings have identified a bacterial consortium of SRB and methanogen-like archaebacteria believed responsible for AMO. Previous evidence for this consortium in marine settings includes the detection of archaebacteria biomarker lipids with d13C values between -100 and -130 and iso- and anteiso-C15:0 phospholipid-derived fatty acids (PLFAs) indicative of SRB with d13C values between -63 and -75. Iso- and anteiso-C15:0 PLFAs have been detected in the soils overlying the methane seep with d13C values depleted by as much as -60. These results are consistent with SRB utilizing the thermogenic methane (-47) as a carbon and energy source. We are currently investigating whether a consortium similar to that found in marine settings is responsible for the sulfate reduction observed above the thermogenic methane seep by analyzing soils for 13C-depleted archaebacteria lipids.