Abstract: Channel Complex Architecture of Fine-Grained Submarine Fans at the Base-of-Slope

Arnold H. Bouma, Gwang H. Lee, Oscar Van Antwerpen, Timothy W. Cook

The fan-valley or upper fan channel connects the submarine canyon on the outer shelf-upper slope to the basin proper. It is an erosionally-formed channel that is a conduit for sediment transported to the basin. The valley may widen where it enters the base-of-slope area. Most of the density flows are much smaller than the initial flow and therefore will not occupy the entire width of the upper fan channel. Smaller individual channels will be constructed resulting in a massive fill comprised of amalgamated sandstones. Sand-rich levees and overbank deposits flank each channel. Channel switching may take place toward locations with a slightly steeper gradient. These switches most likely result from irregular flow successions and different flow sizes. Erosion between successi e channels is common, removing part of the channel fill and levee-overbank deposits. This results in a disorderly distribution of low-permeability barriers creating local obstruction to connectivity.

A study of the sedimentological architecture of the updip mid-fan channel complex was conducted on cliff sections of the Permian Tanqua Karoo subbasin in South Africa, and in Big Rock Quarry in North Little Rock, Arkansas. Seismic records of the base-of-slope of the Mississippi Fan show a widening pattern, and of the Bryant Canyon Fan Complex south of the Sigsbee Escarpment the channel complexity.

Integration of seismic data and outcrop observations improves our understanding of the complexity of many good reservoir sands, typically overlain by slope shales.

AAPG Search and Discovery Article #90955©1995 GCAGS 45th Annual Meeting and Gulf Section SEPM, Baton Rouge, Louisiana