During the R/V GYRE cruise 80-G-4 in May-June 1980, the U.S. Geological Survey conducted high-resolution seismic studies over five intraslope basins and over one selected area of special interest in the northern Gulf of Mexico (fig. 1). Data from each area suggest that the intraslope basins are directly related to past and present salt-diapir activities and sea-level changes. The study areas had been selected on the basis of results of previous high-resolution seismic studies in the northern Gulf of Mexico.