Published: Jan. 1, 2023

Subsurface shallow gas, primarily composed of biogenic methane (>95%), is commonly found in nearshore sediments worldwide. The redox conditions pore fluid play a crucial role shaping the geochemical signatures associated with anaerobic oxidation (AOM) and vertical displacement sulfate-methane transition zones (SMTZs) within deep sedimentary records. However, complete understanding these archives limited by depth collected sediment samples. In this study, we employed combination mineralogical methods to investigate dynamics Zhoushan offshore area. profiles water provided evidence for occurrence AOM presence multiple SMTZs, which were attributed flow methane-rich fluid. Analysis sulfur content characteristics authigenic pyrite different facies revealed four intervals impacted core JC-1. Notably, marine (<40 meters below seafloor) exhibited positive peaks δ34S-CRS values, reaching up 27‰. These overflow resulting from unstable conditions, such as changes sedimentation rate, intense physical reworking, and/or biological activity influencing mud. Interestingly, covariation molybdenum (Mo) uranium (U), indicated (Mo/U)EF ratios, proved be valuable tool providing insights into intensity past seepages, thereby constraining conditions. AOM-derived H2S led suboxic sulfidic occurring narrow zone close seafloor proximity seawater. Consequently, enrichments Mo U. This Mo-U proxy particularly recommended use methane-impacted seabed sediments, where diagenetic processes make sulfide minerals’ δ34S values tracers SMTZ fluctuations challenging.

Language: Английский