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The middle-fan area of the youngest Mississippi fanlobe is a convex-shaped aggradational body with a sinuous, migratory channel located along its apex. The middle-fan/lower-fan boundary corresponds to a change from the sinuous channel pattern to one of lateral switching and abandonment. Sites drilled in the mid-fan channel indicate an upward-fining fill, commencing with gravel and ending with clay. The overbank deposits are primarily muddy with some silty and very-fine sandy turbidites. Sedimentation rates during the Late Wisconsin age for both the channel fill and overbank areas are about 12 m/1000 yr.

Eight different sedimentary facies recognized in the Mississippi Fan sediments drilled during DSDP Leg 96 are defined on the basis of lithology, sedimentary structures, composition, and texture. Pelagic biogenic sediments are of minor importance volumetrically compared with the dominant resedimented terrigenous facies. Clays, muds, and silts are most abundant at all sites, with some sands and gravels within the mid-fan channel fill and an abundance of sand on the lower fanlobe. Facies distribution and vertical sequences reflect the importance of sediment type and supply in controlling fan development.