Sedimentary Evolution Influencing Methane Generation in Coastal Sediments of the Northern South China Sea
Description
Methane intermittently occurs along a 52-meter sedimentary core from the coastal sediments of the northern South China Sea, offering an opportunity to comprehend better the sedimentary factors that influence methane generation. The sediment core was categorized into seven distinct sedimentary facies (U1-U7) based on different sedimentary characteristics at varying depths and dating test results (14C dating and optically stimulated luminescence dating). Sedimentary unit U4 is the primary layer for methane generation. This unit was found to be high in total organic carbon (TOC) and trace metals associated with methanogenesis, while maintaining a low carbon-to-nitrogen (C/N) ratio, which is favorable for biological methane generation. Further analyses showed that intense chemical weathering in the onshore catchment provided the key metallic elements, i.e. Fe, Ni, Mo, and Co, during the deposition of Unit 4. Therefore, biological methane generation is jointly controlled by supplies of organic carbon and trace elements from chemical weathering. Within the file "DataTable.zip", there is an "DataTable.xlsx" file, which contains two sheets: "Sediment Geochemistry" and "Microbial Communities". In the "Sediment Geochemistry" sheet, the carbon isotope data (δ13C) are expressed in per mille (‰) relative to the Pee Dee Belemnite (PDB) and the stable isotope ratios of hydrogen (δD) are conventionally expressed as a per mil (‰) deviation from Standard Mean Ocean Water (VSMOW). Geochemistry of gas along sedimental depth includes data of CH4 content, δ13CCH4 (‰), and δDCH4 (‰). and δDH2O (‰) of the pore water, δ13CCO2 (‰), δ13Ccarbonates (‰) and δ13CTOC (‰). Geochemistry of water along sedimental depth includes data of Cl- and sulfate concentration (mM). Solid sediment along sedimental depth includes data of median grain size (D50, Φ), total carbon content (wt%, TC content), total organic carbon content (wt%, TOC content), total inorganic carbon content (wt%, TIC), total nitrogen content (wt%, TN), δ13C-TOC (‰), δ13C-TIC (‰), Al2O3 (wt%), CaO (wt%), MgO (wt%), K2O (wt%), Na2O (wt%), SiO2 (wt%), TiO2 (wt%), MnO (wt%), TFe2O3 (wt%), Ni (ppm), W (ppm), Mo (ppm), Co (ppm), V (ppm), U (ppm), S (ppm), Sr (ppm), and Ba (ppm). ND means no data. The “Microbial Communities” sheet delineates the variation in percentage of the relative abundance of microbial phyla with significant representation, constituting a substantial proportion of the total microbial population, across different depths. Examples of such phyla include Proteobacteria, Crenarchaeota, Actinobacteriota, Chloroflexi, Firmicutes, Campylobacterota, Acidobacteriota, Bacteroidota, Desulfobacterota, and Planctomycetota. The relative abundance of seven critical functional microbial groups is also enumerated herein, including Euryarchaeota, methanogens, hydrogen-producing organisms, methane-consuming organisms, metal-reducing bacteria, sulfate-reducing bacteria, and nitrate-reducing bacteria.