Relating sulfate and methane dynamics to geology: Accretionary prism offshore SW Taiwan

摘要: Geochemical data (CH4, SO42−, I−, Cl−, particulate organic carbon (POC), δ13C-CH4, and δ13C-CO2) are presented from the upper 30 m of marine sediment on a tectonic submarine accretionary wedge offshore southwest Taiwan. The sampling stations covered three ridges (Tai-Nan, Yung-An, Good Weather), each characterized by bottom simulating reflectors, acoustic turbidity, different types faulting anticlines. Sulfate iodide concentrations varied little seawater-like values in 1–3 at all stations; feature that is consistent with irrigation seawater gas bubbles rising through soft surface sediments. Below this depth, sulfate was rapidly consumed within 5–10 anaerobic oxidation methane (AOM) sulfate-methane transition. Carbon isotopic imply mainly biogenic source. A numerical transport-reaction model used to identify supply pathways estimate depth-integrated turnover rates ridges. Methane ascending deep layers, facilitated thrusts faults, far dominant term budget sites. Differences proximity sites faults anticlines accounted for variability fluxes AOM rates. By comparison, produced situ POC degradation modeled column unimportant. This study demonstrates geochemical trends continental margins SW Taiwan closely related geological settings.