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doi:10.2204/iodp.proc.314315316.209.2013

Results

Concentrations and carbon isotope compositions of methane and methane/ethane (C1/C2) ratios in the void gas samples measured on board and onshore together with headspace gas data measured on board are shown in Table T1 and Figure F1 (see also Table T20 in the “Expedition 315 Site C0001” chapter [Expedition 315 Scientists, 2009]) Methane is the predominant hydrocarbon present in all samples. Concentrations of methane in the void gas samples are 1 order of magnitude higher than those of the maximum range in the headspace gas samples. The C1/C2 ratio is >1000 in most samples, suggesting that methane found at Site C0001 is predominantly of microbial origin (Bernard et al., 1977; Rice and Claypool, 1981).

Carbon isotope compositions of methane in void gas samples measured in the onshore laboratory are shown in Table T1 and Figure F1. The δ13C values of methane in void gas samples range from –74.9‰ to –73.9‰ with an average of –74.2‰, which is consistent with their microbial origin (Fig. F2) (Schoell, 1980; Whiticar et al., 1986).