Signatures and Stages of AOM in the Tectonic Active and Passive Margin, southwest of Taiwan

Glacial and interglacial sea level changes have been suggested as a major mechanism in shifting the stability of gas hydrate at depth and subsequent gas migration induced AOM (anaerobic oxidation of methane) reactions. AOM is an important microbial mediated process controlling methane and sulfur biogeochemical cycle. In marine sediments under stable condition with large quantity of methane migrating from dissociated gas hydrate, sulfate depletion and accompanied isotopic fractionation registered strong signatures in sediments near the SMTZ (sulfate methane transition zone). In this study, we present geochemical data showing differences and stages of AOM induced minerals formation in sediments at active and passive margins offshore southwestern Taiwan. Our results show that multiple stages of AOM may have occurred in the active part of the northeast South China Sea near Taiwan, an accretionary wedge, whereas only one or none was found in the passive margin adjacent to the study active margin. At present day SMTZ, rapid sulfate depletion always accompany with higher concentration of methane beneath a dissolved sulfide peak. The depth of SMTZ varied at different sites, but that in deep water passive margin sites was deeper than those in the active margin. Our results indicated that gas migration in the active margin may controlled by the tectonic and/or local seismic activity.