Abstract Grainsize, coarse-fraction analyses, and depositional environment are related to continuity and character of sparker reflections at the location of nine core holes drilled by Exxon, Chevron, Gulf, and Mobil on the continental slope of the northern Gulf of Mexico. Continuous sparker reflections are correlated with slowly deposited, evenly bedded sediments containing bathyal faunas. The coarse fraction is dominated by the tests of foraminifers. Discontinuous, discordant reflections and diffractions are correlated with sediments more rapidly emplaced in the bathyal environment of the continental slope by slumping and sliding from the continental shelf. These sediments contain neritic faunas that lived on the continental shelf. Their coarse fraction is dominated by terrigenous sand grains. A large part of the volume of continental-slope sediments appears to consist of these “displaced” sediments, including an area 3 to 24km wide and 80 km long, southeast of Corpus Christi, Texas, and much of the Mississippi Fan southeast of New Orleans.