Primary deposition and early diagenetic effects on the high saturation accumulation of gas hydrate in a silt dominated reservoir in the Gulf of Mexico

On continental margins, high saturation gas hydrate systems (>60% pore volume) are common in canyon and channel environments within the stability zone, where reservoirs dominated by coarse-grained, porosity sand deposits. Recent studies, including results presented here, suggest that rapidly deposited, silt-dominated channel-levee can also host accumulations. Here we present several sedimentological data sets, sediment composition, biostratigraphic age from calcareous nannofossils, grain size, total organic carbon (TOC), C/N elemental ratio, ?13C-TOC, CaCO3, sulfur (TS), ?34S-TS sediments collected with pressure cores a rich, turbidite system Gulf of Mexico during 2017 UT-GOM2-1 Hydrate Pressure Coring Expedition. Our indicate reservoir is composed three main lithofacies, which have distinct size distributions (type A-silty clay to clayey silt, type B-clayey C-sandy silt silty sand) characteristic variable turbidity current energy regimes Pleistocene (< 0.91 Ma) environment. We document TOC terrestrial origin contained fine fraction each while CaCO3 primarily reworked grains, Cretaceous part detrital load. The lack biogenic grains finest grained intervals throughout suggests interevent hemipelagic not preserved, resulting sequence dominated, stacked turbidites. observe two zones enhanced TS at top bottom correspond enriched bulk ?34S, indicating stalled or slowly advancing paleo-sulfate-methane transition zone (SMTZ) positions likely driven relative decreases sedimentation rate. Despite these diagenetic zones, low abundance precipitates allowed primary remain largely intact, thus better preserving for subsequent pore-filling hydrate. In canyon, channel, levee environments, early diagenesis may be regulated via rates, rates result rapid progression through SMTZ minimal mineralization stalling SMTZ, enhancing mineralization. Here, observed some pyritization implicate potential rate changes, but enough consume porosity, reservoir. These emphasize important implications sedimentary processes, on distribution marine along margins.