[MIS32-P03] Total organic carbon in subsurface sediment off Abashiri, the Sea of Okhotsk
Keywords:TOC, gas hydrate, methane
Natural gas hydrates were retrieved in the sediment cores of HKS1807 and HKS1808 using a hydrostatic corer, and 1KYPS1701-04 using a push corer with ROV. The content of total organic carbon was 1.3-1.6% in HKS1807 and HKS1808, 0.8-2.3% in 1KYPS1701-04, and generally less than 1% for other sediment cores off Abashiri. It is reasonable to say that hydrate-bound sediment cores are rich in organic matter. On the other hand, C061-GC1803 off Tokachi showed around 2% and cores of GA18 and GA19 partly exceeded 3%, suggesting that the content of organic matter is not a sufficient condition for gas hydrate formation. δ13C of total organic carbon distributed around -25‰ for all samples, however, some samples of 1KY17 showed less than -30‰. Because sediment cores of 1KY17 (1KYPS1701-04) were short (up to 25 cm) and obtained from the gas seepage, the organic matter might be affected by oxidized methane.
Waseda A (1998) Organic carbon content, bacterial methanogenesis, and accumulation processes of gas hydrates in marine sediments. Geochem J 32: 143-157