A New Look at Subsea Gas Emissions from the Barbados Accretionary Complex

We study newly identified gas plumes in the water column from the Barbados Accretionary Complex using multibeam echo soundings from cruise AT21-02. The multibeam data were used to define a region with several ~600 – 900 m tall gas plumes in the water column directly above cratered hummocky regions of the sea floor that have relatively high backscatter, at a water depth of ~1500 m. The natural gas hydrate stability zone reaches a minimum depth of ~600 m in the water column, similar to that of the tallest imaged bubble plumes, implying hydrate shells on the gas bubbles. Maximum tilt of the plume shows current shear in a direction from northwest to southeast (~128°), similar to the transport direction of North Atlantic Deep Water. The source of hydrocarbons, determined from existing geochemical data, suggests the gas source was subjacent marine Cretaceous source rocks. North-south trending faults, craters and mud volcanoes associated with the gas plumes point to the presence of a deep plumbing system and indicate that gas is a driver of mud volcanism. The widespread occurrence of seafloor morphology related to venting indicates that subsea emissions from the Barbados Accretionary Complex are substantial.