ABSTRACT

Carbonates of shallow water origin have been recovered from an area of some 39,000 square miles in the Gulf of Mexico abyssal plain. These carbonates occur most commonly as layers of variable thickness (2-120 cm) in cores of Pleistocene-Recent sediments.

Cores from the southern edge of the abyssal plain reveal a remarkable lithologic simplicity and orderliness, characterized in general by a vertical repetition of three members: (1) a basal white or light gray, medium calcilutite, 30 cm in average thickness, which is commonly cross-laminated and contains an abundant shallow water benthonic fauna; overlain by (2) a light olive-gray, fine calcilutite, some 35 cm in average thickness, which is commonly bioturbated and consists of a mixture of comminuted shells, micrite, and argillaceous lutite, and which contains both planktonic and shallow water benthonic fauna; (3) an olive gray-olive black argillaceous lutite, 50 cm in average thickness, which may be bioturbated or structureless, and which contains a scattered planktonic fauna. Each co e consists of several such sequences, each of which represents deposition from a mature turbidity-current that originated on the Campeche Shelf, and which was followed by a period of characteristic abyssal plain sedimentation of argillaceous lutites.

Areal distribution of the turbidites suggests that occasionally the flows travelled beyond the present northern limits of the abyssal plain--a total travel path of 350 miles. The tremendous quantities of detrital sediment that originated from the Mexico and Texas continental shelves, as well as from the Mississippi River, either buried the carbonate turbidites beyond coring depths or diluted these flows in the southwest, northwest, and east of the abyssal plain.