Sand and silt interbeds in cores from the continental slope, rise and abyssal plain of the Gulf of Mexico, may be composed of either detrital or carbonate sediments. Because of the insensitivity of the detrital minerals to transport distance and environment, the sand and silt interbeds from the deep portions of the Gulf may be related to specific source areas on the continental shelf. These source areas include (1) the Mississippi, (2) the Rio Grande, and (3) the rivers of northeast Mexico. Vertical variations in mineralogy show no significant trend with increasing depth in any core, indicating that relative contributions from each source remained constant. Carbonate sands and silts of the abyssal plain were derived from the shallow waters of the Campeche Shelf. Transportation along the axis of the Campeche Canyon carried these shelf carbonates northward into deeper water areas. in some instances through the medium of turbidity currents.