5:15 PM - 6:30 PM
[MIS09-P07] Isotopic compositions of Carbon, Oxygen, and Strontium in authigenic carbonates from Umitaka Spur, off-Joetsu, southeast of Japan Sea
Keywords:authigenic carbonates, shallow gas hydrate, Japan Sea
The carbon isotopic values in authigenic carbonate from Umitaka Spur are higher than those of Joetsu Knoll and west off-Tobishima Island. This range corresponds to the δ13C values of thermogenic methane (Bernard et al., 1978). Range of the δ18O values of authigenic carbonates from Umitaka Spur is mostly equal to those of Joetsu Knoll and west off-Tobishima Island.
The 87Sr/86Sr ratios in authigenic carbonates from shallow depth of Umitaka Spur is equal to those of modern surface seawater in off-Joetsu. The Sr-isotopic ratios in authigenic carbonate from deeper depth are lower ratios. This Sr-isotopic trend can be correlated to the global Sr-isotopic trend in seawater from late Pleistocene to present. It indicates that Sr-isotopic ratio of authigenic carbonate reflects the Sr-isotopic ratio of seawater at the time of deposition. The Sr-isotopic ratios in pore water are parallel lower than those of authigenic carbonate. It indicates that pore water includes light Sr by diagenetic procedure.
Acknowledgments: This study was conducted as a part of the shallow methane hydrate exploration project of METI. Isotopic measurement of Strontium was performed in Kochi Core Center, by visiting scientist program of JAMSTEC.