期刊
JOURNAL OF ASIAN EARTH SCIENCES
卷 168, 期 -, 页码 137-144出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jseaes.2018.11.011
关键词
Cold seep; Anaerobic oxidation of methane; Carbon and sulfur isotopes; South China Sea
资金
- National Key R&D Program of China [2017YFC0306702]
- National Program on Global Change and Air-Sea Interaction [GASI-GEOGE-05-04]
- Qingdao National Laboratory for Marine Science and Technology [QNLM2016ORP0204]
- NSF of China [41730528, 41761134084, 41773091]
- National Special Project on Gas Hydrate of China [DD20160217]
Cold seeps frequently occur at the seafloor along continental margins. The dominant biogeochemical processes at cold seeps are the combined anaerobic oxidation of methane and sulfate reduction, which can significantly impact the global carbon and sulfur cycles. The circulation of methane-rich fluids at margins is highly variable in time and space, and assessing past seepage activity requires the use of specific geochemical markers. In this study, we report multiple sedimentary proxy records for three piston gravity cores (QDN-14A, QDN-14B, and QDN-31) from the Haima seep of the South China Sea (SCS). By combining total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), total sulfur (TS), acid insoluble carbon and sulfur isotope (delta C-13(organic) carbon and delta S-34(acid-insoluble)), and delta S-34 values of chromium reducibility sulfur (delta S-34(CRS)), as well as carbon isotopes of TIC (delta C-13(TIC)) in sediments, our aim was to provide constraints on methane seepage dynamics in this area. We identified three sediment layers at about 260-300 cm, 380-420 cm and 480-520 cm sediment depth, characterized by particular anomalies of low delta C-13(TIC) values and high TS content, high TS and CRS contents, and high delta S-34(acid-insoluble) and delta S-34(CRS) values, respectively. On this basis, we propose that these sediment horizons correspond to distinct methane release events preserved in the sediment record. While the exact mechanisms accounting for the presence (or absence) of these particular geochemical signals in the sediment are not known, we propose that they correspond to variations in methane flux and their duration through time. Overall, our results suggest that sedimentary carbon and sulfur and their isotopes are useful tracers for better understanding of methane seepage dynamics over time.
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