| This thesis presents estimates of gas hydrate distribution and saturation utilizing data from the four IODP Expedition 311 drilling sites, located at the northern Cascadia Margin. The objectives are to constrain geologic models of hydrate formation by determining mechanisms controlling magnitude and distribution of hydrate occurrences, finding pathways enabling fluid migration, and examining the effect of hydrate on physical properties of the sediment. Well log and core data are used to calculate hydrate concentrations, complemented by pore-fluid geochemical data. Correlation of seismic and logging data is achieved through synthetic seismograms. Lithology and faulting appears to control hydrate occurrences, which contradicts established hydrate formation models. Individual sedimentary layers (e.g. turbidites) and abundant faults act as migration pathways for fluids and gas explaining the high hydrate concentrations at shallow depths of less than 100 meters below seafloor, instead of the previously predicted enrichment near the base of the hydrate stability zone. |
