冷湧水炭酸塩岩中の嫌気的メタン酸化を示すバイオマーカー

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The biomarkers and their specific carbon isotopic compositions (δ^<13>C) have been analyzed in Cretaceous carbonate rocks collected from four areas in Hokkaido, Japan. Anaerobic oxidation of methane (AOM) might occur in Tappu-Kanajirizawa and Teshionakagawa-Abeshinaigawa carbonate rocks, which have found to be related to cold-seep biological fossil communities. The biomarker distributions and their δ^<13>C values showed that these carbonates were presumably linked to Archaea and bacteria associated with AOM in these cold-seep environments. These carbonate samples contained the "tail to tail" linked isoprenoid hydrocarbons, crocetane (2, 6, 11, 15-tetramethylhexadecane), PME (2, 6, 10, 15, 19-pentamethyleicosane), and their unsaturated derivatives. Squalane (2, 6, 10, 15, 19, 23-hexamethyltetracosane), C_<40> acyclic and cyclic isoprenoid hydrocarbons were also detected. The occurrence of these compounds indicates that Archaea clearly play an important role during carbonate precipitation in the cold-seep environments. Archeal biomarkers were depleted in ^<13>C, indicating that archaeal isoprenoids were biosynthesized from isotopically depleted carbon such as that derived from methane. In addition to the archaeal markers, the isotopically ^<13>C-depleted iso -and anteiso -alkanes, which were most likely derived from sulfate-reducing bacteria, were identified. These results support the model that the sulfate-reducing bacteria might be closely linked to Archaea responsible for the AOM, although these organisms were generally competitive. The Manji-Shikorozawa and Yubari-Utagoezawa carbonates, which were lacking the cold-seep fossil biological communities, showed similar biomarker distribution. Biomarker analyses indicated these carbonates could have potential as cold-seep carbonate, and biomarker is possibly a useful indicator of cold-seep carbonate.
日本地球化学会の論文
2004-06-05

著者

荻原成騎
東京大学大学院理学系研究科地球惑星科学専攻

冷湧水炭酸塩岩中の嫌気的メタン酸化を示すバイオマーカー

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