MAYALL, MIKE, and IAN STEWART, BP Exploration, Uxbridge, Middlesex, England

Abstract: The Architecture of Turbidite Slope Channels

Extensive 3D seismic data from around the world shows remarkable details on the geometry and facies of Tertiary turbidite channels. In the upper part of the slope the channels are often relatively narrow (<1km) with fairly straight leveed margins which may or may not contain a moderate-high sinuosity channel axis. Downslope the channels become broader (1- 2km), highly sinuous (sinuosity >2) with erosional bases and local levee and crevasse-splay development. In detail, the channels can vary radically over short distances down-stream. The highly sinuous channels show both dominantly vertical aggradation and in other places very marked lateral migration producing features very similar to fluvial point bars. The channels contain high net-gross sandy fills with medium to coarse sand and even pebbles over 200km from the contemporaneous slope entry points.

Ponded basins are not common and generally the channels display continuous complex courses which take them through and beyond irregular sea-floor topography.

Associated with the channels are more sheet-like seismic facies.The origin of these features is less clear, they may be parts of levees of the larger channels, splays which were deposited laterally or at the mouths of channels, or by processes unrelated to the major channels.

These Tertiary channel systems have very similar geometries to those observed in modern fans such as the Amazon and the Zaire and pose many questions regarding the nature of the currents which transported and deposited the sediments.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England