Summary

Mass movement of sediments takes on varying forms, such as slides, slumps, and debris flows. These features are sometimes identified by their chaotic seismic response. Two subsurface geologic features on the Northern Gulf of Mexico slope were initially studied with available 2-D and 3-D seismic. The first has characteristics that according to Shanmugam et at. (1994) would be classified as a slump and is unique in the degree of definition imaged by the 3-D seismic. The occurrence of mass movement during a time of pelagic deposition allowed the preservation of downslope toe thrust and folds, as well as strike/slip boundary zones. Seismic attribute mapping of this feature results in an image that appears as crisp as if on the present seafloor; however, the slump resides at approximately 6000 feet (1830 m) subsea.

The second feature is recognized as a major slope fan channel complex. Previous mapping by Risch et al. (1996) appeared to be on the highstand sequence boundary above the channel. The use of depth-converted color isochron maps based on the top of the channel/levee system deposits more clearly depicts a major channel system that delivered sediment into deeper water over an extended period of time without any major lateral shifts.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah