ABSTRACT

The Eastern Mississippi Fan is a moderate size, Pleistocene submarine fan in the deep northeastern Gulf of Mexico. Analysis of 4,290 mi (6,900 km) of multifold seismic data identified nine discrete depositional sequences coeval to sequences 7-11 and 13-16 previously described in the Western Mississippi Fan. Each of the eight youngest sequences consists of a channel-levee system; five 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 aggradational channel-levee deposition. Each channel-levee system includes one to several channel valleys. 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 channel valleys range from 980 to 2,125 ft (300 to 650 m), whereas lateral migration values for channel valleys range from 0 to 2.0 mi (0 to 3.0 km). Channel valley sinuosities range from low to high, and the number of downfan channel bifurcations ranges from 0 to 3. A single channel-levee system, sequence 9, is described in detail to illustrate the variabilities in channel-levee evolution.