Pleistocene slope instability of gas hydrate‐laden sediment on the Beaufort sea margin

Abstract

Abstract The Beaufort Sea continental slope is disrupted by a belt of massive bedding‐plane slides and rotational slumps. This zone coincides with a region of sediment containing gas hydrate, an inclusion compound of gas and water. Quantitative studies suggest that elevated pore‐fluid pressures generated as a by‐product of gas hydrate disassociation during repeated episodes of eustatic sea level lowering during Pleistocene time were a major cause of these slides. Eustatic sea level fall causes reduced pressures acting on seafloor sediment. In oceanic areas underlain by sediment with gas hydrate, the reduction of sea level initiates disassociation along the base of the gas hydrate, which, in turn, causes the release of large volumes of gas into the sediment and creates excess pore‐fluid pressures and reduced slope stability. A quantitative approach was taken to predict excess pressures at the base of the gas hydrate zone, and the stability of the overlying sediment for a variety of sediment types. Our studies suggest that during eustatic sea level fall, fluid diffusion properties dominate the disassociation process in fine‐grained marine sediment. Slope failure appears likely for this sediment type on moderate slopes unless pressures can be adequately vented away from the gas hydrate base. These models give credence to the theory that fluctuations in global climate, manifest in periodic Pleistocene eustatic‐sea level regressions, likely triggered seafloor landslides on the continental slope of the Beaufort Sea and other margins where gas hydrate is present in seafloor sediment.