Using chemical compositions of sediments to constrain methane seepage dynamics: A case study from Haima cold seeps of the South China Sea
|Author(s)||Wang Xudong1, 6, Li Niu1, Feng Dong1, 2, Hu Yu3, Bayon Germain4, Liang Qianyong5, Tong Hongpeng3, Gong Shanggui1, 6, Tao Jun5, Chen Duofu2, 3|
|Affiliation(s)||1 : Chinese Acad Sci, CAS Key Lab Ocean & Marginal Sea Geol, South China Sea Inst Oceanol, Guangzhou 510301, Guangdong, Peoples R China.
2 : Qingdao Natl Lab Marine Sci & Technol, Lab Marine Mineral Resources, Qingdao 266061, Peoples R China.
3 : Shanghai Ocean Univ, Coll Marine Sci, Shanghai Engn Res Ctr Hadal Sci & Technol, Shanghai 201306, Peoples R China.
4 : IFREMER, Lab Geophys & Enregistrements Sedimentaires, Unite Rech Geosci Marines, F-29280 Plouzane, France.
5 : China Geol Survey, MLR Key Lab Marine Mineral Resources, Guangzhou Marine Geol Survey, Guangzhou 510070, Guangdong, Peoples R China.
6 : Univ Chinese Acad Sci, Beijing 100049, Peoples R China.
|Source||Journal Of Asian Earth Sciences (1367-9120) (Pergamon-elsevier Science Ltd), 2018-12 , Vol. 168 , P. 137-144|
|WOS© Times Cited||35|
|Keyword(s)||Cold seep, Anaerobic oxidation of methane, Carbon and sulfur isotopes, South China Sea|
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 (δ13Corganic carbon and δ34Sacid-insoluble), and δ34S values of chromium reducibility sulfur (δ34SCRS), as well as carbon isotopes of TIC (δ13CTIC) 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 δ13CTIC values and high TS content, high TS and CRS contents, and high δ34Sacid-insoluble and δ34SCRS 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.