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Mississippi Fan Construction and Sea Level Fluctuation Relationships

A. H. Bouma, C. E. Stelting, J. M. Coleman, B. Kohl

The Mississippi fan consists of individual fanlobes that are not stacked vertically but overlap each other partly. Fan-wide seismic reflectors separate successive fanlobes. Each fanlobe can be defined as a channel-overbank complex that changes in characteristics in a downfan direction and therefore permits a natural division into a submarine canyon, upper fan, middle fan, and lower fan. The canyon and upper fan channel are erosive and primarily result from retrogressive slope failure during a relative lowering of sea level. The middle and lower fans are constructive, and deposition occurs primarily during the last stage of sea level lowering and the initial rise of sea level. Late in the sea level rise, fine-grained sediments are deposited in the canyon and upper fan chan el. Sand deposition is restricted principally to the migratory midfan channel, the set of ephemeral channels on the lower fan, and the sheet deposits at the end of the channels.

Sea level fluctuations determine the timing of transport of sand to the submarine environment; the amount of relative lowering dictates the relative amounts.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.