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A vast accumulation of high-saturation gas hydrates has been hypothesized to be present in the central Gulf of Mexico; the interpretation was based on seismic travel time deficits underlying high velocity Pleistocene coarse-grained turbidites. While these deposits could represent one of the largest-known gas hydrate reservoirs, some workers have concluded that lithologic contrasts are instead the primary cause of observed velocity pull-ups. Here, using cuttings and core, well logs, and seismic data from the Mississippi Fan, we demonstrate that lithologic differences can account for a maximum of similar to 6-33% of the total observed travel time deficits. This conclusion supports the previous interpretation of a gas hydrate province, provides a basis for distinguishing the cause of velocity pull-ups, and suggests that the future of gas hydrate exploration should continue to include the coarsest-grained component of the Earth's largest near-seafloor submarine fans.

Plain Language Summary A large accumulation of gas hydrates, which are frozen hydrocarbons located in near-surface settings, was recently interpreted to exist in the central Gulf of Mexico; the subsurface deposit was inferred on the basis of artifacts related to increased sound wave velocities (i.e., travel time deficits). Although other factors, such as lithologic differences, also can produce changes in the speed of sound, the observed contrasts are too great to be explained by such variations. This observation supports the initial claim of the presence of a vast gas hydrate accumulation and suggests that similar settings worldwide may contain comparable frozen gas-bearing deposits.