Abstract: Seismic Facies and Variations in Channel Evolution, Eastern Mississippi Fan (Pleistocene), Northeastern Deep Gulf of Mexico

Barrett T. Dixon, Paul Weimer

The eastern Mississippi Fan is a moderate size, Pleistocene submarine fan in the northeastern deep Gulf of Mexico. Analysis of 6900 km of multifold seismic data identified nine discrete depositional sequences coeval to sequences 8-16 in the western Mississippi Fan (Weimer, 1989). Each sequence consists of a channel-levee system; six of the channel-levee systems are derived from submarine canyons located in the Viosca Knoll and Mississippi Canyon lease areas. The three remaining channel-levee systems are downfan continuations of systems previously described in the western Mississippi Fan.

Typical evolution of a channel-levee system consists of an erosional surface at the base, overlain by hummocky to mounded reflections (interpreted as disorganized slides and debris flows), which in turn are overlain by the aggradational channel-levee deposition. Each channel-levee system includes one to several channels. Their physical characteristics are described using four parameters: aggradation, lateral migration, sinuosity, and bifurcation. Values for these parameters differ both between and within individual channel-levee systems. Maximum aggradation values for channels range from 250 to 650 m, whereas lateral migration values for channels range from 0 to 4.5 km. Channel sinuosities range from low to high amount, and the number of downfan channel bifurcations ranges from 0 to 3 Significant in-situ slides deform large portions of five discrete channel-levee systems, indicating significant post depositional deformation of fan sediments on low-dipping surfaces (<½ degree). Two channel-levee systems, sequences 9 and 15, are described in detail to illustrate the variabilities in channel-levee evolution.

AAPG Search and Discovery Article #90983©1994 GCAGS and Gulf Coast SEPM 44th Annual Meeting, Austin, Texas, October 6-7, 1994