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Seismic Stratigraphy of Northern Green Canyon Area, Gulf of Mexico

Robert G. Mann, William R. Bryant

The Green Canyon area of the Gulf of Mexico is an active frontier exploration area of the continental slope underlain by relatively shallow salt or shale diapirs and ridges forming large intraslope basins and troughs. Analysis of more than 200 multichannel seismic profiles in this area show several seismic sequences within each basin or trough. The depositional history of the area is interpreted from the seismic sequences and seismic facies distribution within each basin. These facies are based on reflection configuration and include parallel to subparallel reflections, prograding clinoforms, hummocky clinoforms, chaotic zones, and acoustically semitransparent zones. Sigmoid and oblique progradational clinoforms are found at the shelf edge where outbuilding and aggradatio occur. Hummocky clinoforms are widespread in each basin and occur in thick sequences. These grade vertically and laterally into parallel or semi-transparent zones resulting in alternating reflection patterns. The parallel reflections can be interpreted as low-energy turbidites deposited during lower sea level. Chaotic zones show contorted stratal surfaces suggesting mass movement deposits.

The evolution of each basin is unique. Structure and isopach maps of each sequence along with the facies distribution indicate several depositional mechanisms. These are possibly related to sea level fluctuations and shifting sediment supply. Correlation of sequences between basins and troughs is hampered in the western half of the area because of the presence of shallow subsurface diapirs and ridges, and large growth faults, and the absence of well data. Diapirs in the eastern half are less numerous and more isolated, with thicker sedimentary troughs between them because of the eastward migration of the Mississippi fan across this area in the Pliocene and Pleistocene.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.