[MIS16-P08] Geochemistry of methane in surface sediment of shallow gas hydrate deposits
in the Oki Trough and Joetsu Basin, Japan Sea
Keywords:shallow gas hydrate, Japan Sea
The depths of SMI are shallow and δ13C values of methane below the SMI are high in the Joetsu Basin compared to the Oki Trough, reflecting that higher methane flux is caused by higher contribution of thermogenic gas. The δ13C values show negative peaks around the SMI, which are relatively large in the Joetsu Basin, reflecting the carbon recycling between anaerobic methane oxidation and microbial methane production around there. The rapid decreases of C1/(C2+C3) ratios around the SMI are also caused by the anaerobic oxidation of methane. The C1/(C2+C3) ratios are entirely high in the Joetsu Basin, resulting mainly from ethane enrichment in the Oki Trough. Differences of gas source is one of the important factors controlling shallow biogeochemical processes.
This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by the Ministry of Economy, Trade and Industry, Japan.