Evolution of gas hydrates inventory and anaerobic oxidation of methane (AOM) after 40ka in the Taixinan Basin, South China Sea

Abstract

Gas hydrates are the largest carbon sink on the earth and have an important impact on global climate and the environment. We studied theδ34S,δ13C, major trace elements and P –Fe dates at station 973-4 which acquired from the cold seep area of the Taixinan Basin. The results showed that during the Last Glacial Maximum (LGM), Younger Dryas (YD), and the Last Deglaciation, Gas hydrate inventory (GHI) was significantly reduced. And during the LGM, anaerobic oxidation of methane played an important role in preventing methane from leaking into seawater and the atmosphere. Because that there was no acidification of seawater or increase in PCO2. Meanwhile, rapid rate of sediment accumulation caused by isobaric flow provided accumulated material for Anaerobic Oxidation of Methan (AOM) during the LGM. The rapid rate of sediment accumulation also created a good environment for the formation of PCFA and vivianite below the sulfate methane transition zone (SMTZ). And according to changes of elements with depth, we conclude that the effect of methane anaerobic oxidation on redistribution of elemental P–Fe is divided into three processes: SMTZ rapid movement (material accumulation); SMTZ gradually stable; and SMTZ fixation process. In this paper, the effects of sedimentary evolution and hydrate evolution on AOM are studied in detail, which is of great significance for further understanding of anaerobic oxidation of methane.