Recently, methane seepage related to the dissociation of natural gas hydrates has attracted much attention, which has a significant impact on the study of the global carbon and nitrogen cycles. Based on the detailed geochemical analyses of sediments (core Q6) from the Qiongdongnan Basin, South China Sea, three methane seepage activities were identified and the exact horizons of anaerobic oxidation of methane (AOM) were defined. Furthermore, organic carbon isotopic (δ13CTOC) levels ranged from ?23.6‰ – ?20.6‰ PDB; nitrogen isotopes (δ15NTN) of the same sedimentary samples ranged from 1.8‰ – 5.3‰. We also found obvious simultaneous negative excursions of organic carbon isotopes (δ13CTOC) and nitrogen isotopes (δ15NTN) in the horizons of methane seepages. Com-pared with the normal sediments, their maximum negative excursions were 2.6‰ and 2.5‰, respectively. We discuss in detail the various characteristics of δ15NTN and δ13CTOC levels in sediments and their coupling responses to methane seepage activities. We believe that the methane seepage events changed the evolution trajectory of δ15NTN and δ13CTOC levels in sediment records, which resulted in the simultaneous negative excursions. This phenomenon is of great significance to reveal the historical dissociation of natural gas hydrates and their influence on the deep-sea carbon and nitrogen pool.

MIAO Xiaoming;FENG Xiuli;HU Limin;LI Jingrui;LIU Xiting;WANG Nan;XIAO Qianwen;WEI Jiangong

College of Marine Geosciences,Ocean University of China,the Key Laboratory of Submarine Geosciences and Prospecting Techniques,Qingdao 266100,China;Deep-Sea Multidisciplinary Research Center&Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266037,China;MLR Key Laboratory of Marine Mineral Resources,Guangzhou Marine Geological Survey,Guangzhou 510075,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China

中国海洋大学学报（自然科学英文版）

[1]MIAO Xiaoming;FENG Xiuli;HU Limin;LI Jingrui;LIU Xiting;WANG Nan;XIAO Qianwen;WEI Jiangong-.Coupled δ15NTN and δ13CTOC Insights into Methane Seepage Activities in Bulk Marine Sediments of the Qiongdongnan Basin, South China Sea)[J].中国海洋大学学报（自然科学英文版）,2022(06):1495-1503

15NTN,13CTOC,seepages

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