Parts of six submarine canyons and canyon complexes on the shelf of the northwest Gulf of Mexico were studied using seismic stratigraphic techniques. These canyons were eroded during the late Pleistocene, probably by subaqueous processes acting on channels formed subaerially during a low stand of sea level. They have since been infilled and are now buried beneath as much as 6,000 ft (1,830 m) of sediment. The reflection patterns produced by the sediments infilling the channels range from parallel to mildly chaotic, and the reflections are variable in intensity. The sediments appear to have undergone considerable modification by slumping or flowage. They are mostly shale with some silt and lesser amounts of sand nearshore. The sediments that were deposited at the mouths of the canyons are mostly shale and, where undisturbed, display subparallel reflections. Individual canyons ranged in size from 2 to 20 mi (3.2 to 32 km) wide and were as much as 3,500 ft (1,068 m) deep before being infilled.

Oil or gas accumulations may be associated with these canyons in two ways. First, there may be hydrocarbon accumulations within the sediments deposited in deeper water at the mouths of the canyons. Second, the

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fine-grained sediments infilling the channels may have acted as a seal, entrapping the oil or gas in the reservoir rocks through which the canyons cut.

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