2008 Joint Annual Meeting (5-9 Oct. 2008): Centennial-Millennial Scale Stability of a Large Gas-Hydrate Field in the Northern Gulf of Mexico: Investigating Linkages to Climate Change and Slope Erosion

Gas hydrates underlie a substantial portion of the Northern Gulf of Mexico margin. It has been proposed that such deposits are subject to catastrophic degassing events, resulting in slope destabilization, and the rapid release of methane into the ocean-atmosphere system. Although methane hydrates constitute a potential control on both climate change and slope sedimentation processes, many important questions remain about the stability of these deposits (e.g., their time scales of variability), and the precise factors that trigger large dissociation events. This study investigates centennial-millennial scale variability of an active gas-hydrate field in the northern Gulf of Mexico (Mississippi Canyon Federal Lease Block 118, or MC-118) during the late Pleistocene and Holocene. A depth transect of twelve sediment cores collected from sites above to below the field comprises a 20,000-year long record of slope sedimentation. A suite of sedimentologic, paleontologic, and geochemical data are used to evaluate (1) variable sedimentation across the study area, (2) the temporal stability of the gas hydrate deposits, and (3) their connection to recent paleoclimate and depositional events in the Gulf of Mexico. Elemental data obtained from X-ray fluorescence (XRF) scanning of the cores indicates pronounced changes in sedimentation across the study area. Contrasting deposition upslope and downslope of MC-118 provides a means to differentiate gas-hydrate induced erosion from regional slope erosion. Finally, analysis of Ba/Al, which has been previously proposed as a proxy for hydrate eruption events, suggests periods of enhanced hydrate dissociation over the past 20,000 years.