Methane was found in Recent sediments of two basins on the Labrador continental shelf. These basins are carved in what are believed to be Tertiary and Mesozoic strata resting on Precambrian and possibly Paleozoic rocks. Geochemical and foraminiferal analyses of sediments from one piston core indicate that the gas is a product of anaerobic fermentation of organic matter. Mildly anaerobic conditions existed in subsurface sediments, which were deposited under marine conditions shortly after the retreat of the last Pleistocene glaciation.