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54 sediments were sampled at 5 sites, 1244, 1245, 1246, 1250 and 1251 from ODP Leg 204, Hydrate Ridge, Cascadia Margin. The stable carbon and nitrogen isotopic composition, δ C of 13 organic matter and δ N, have been used to characterize the depositional variation of sediments with 15 gas hydrate bearing. Values of δ C of bulk organic matter range between ?22.37‰ and ?24.72‰ 13 PDB, with a mean value of ?23.54±1.17‰ PDB; δ N of the same sedimentary samples range from 15 3.30‰ to 5.68‰, with a mean value of 4.49±1.19‰; Values of C/N ratio range from 4.53 to 9.26, with a mean value of 6.90±2.37. The occurrence of gas hydrate changed the diagenetic evolution trend of the carbon and nitrogen in organic matter. The δ N and C/N ratio depletion suggest that the nitrogen 15 fixation related with the bacteria/archaea maybe occurred in the sediments near the hydrate. The stable carbon and nitrogen isotopic composition could be used to evaluate the depositional environ- ment in the study area.
54 sediments were sampled at 5 sites, 1244, 1245, 1246, 1250 and 1251 from ODP Leg 204, Hydrate Ridge, Cascadia Margin. The stable carbon and nitrogen isotopic composition, δ C of 13 organic matter and δ N, have been used to Characterize the depositional variation of sediments with 15 gas hydrate bearing. Values of δ C of bulk organic matter range between · 22.37 ‰ and · 24.72 ‰ 13 PDB, with a mean value of · 23.54 ± 1.17 ‰ PDB; δ N of the same sedimentary Samples of range 15 3.30 ‰ to 5.68 ‰, with a mean value of 4.49 ± 1.19 ‰; Values of C / N ratio range from 4.53 to 9.26, with a mean value of 6.90 ± 2.37. The occurrence of gas hydrate changed the diagenetic evolution trend of the carbon and nitrogen in organic matter. The δ N and C / N ratio depletion suggest that the nitrogen 15 fixation related with the bacteria / archaea maybe occurred in the sediments near the hydrate. The stable carbon and nitrogen isotopic composition could be used to evaluate the depositional environ ment ment i n the study area.