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Comparing Stratal Architectures in Confined and Weakly Confined Turbidite Channel Systems

Fernandes, Anjali M.1; Henriksen, Sverre 2; Steel, Ron 1; Mohrig, David 1
1 Jackson School of Geosciences, Department of Geological Sciences, University of Texas at Austin, Austin, TX.
2 StatoilHydro Research Center, StatoilHydro ASA, Trondheim, Norway.

Confinement in turbidite channel systems can be erosional in origin, constructional in origin or have a mixture of both elements. We present a comparison of architectures found in two slope channel systems from offshore West Africa, imaged in a 3-D high resolution seismic volume. The first channel system is erosionally confined, restricted to a conduit that is 1-1.5km wide and 150m deep. The second channel system is only weakly confined; moving from an early stage of erosional confinement to a later stage where confinement was generated by channel-bounding depositional levees. The dimensions and consequences of confinement in the stratigraphic evolution of these systems is evaluated.

The planform patterns of channels seen throughout the stratigraphy of the erosionally confined system are remarkably similar, with only some variation in sinuosity. In this case, the pre-existing, 150m-deep confinement does not provide much flexibility to modify the planform pattern, except through a limited amount of erosion against the canyon walls and through the natural upward widening of the confinement. We conclude that where the planform of channels closely mimics the planform of the confinement, channel migration and stacking patterns are quite predictable.

In the levee-confined system, a variety of planform patterns are visible in horizon slices, with changes in planform becoming less drastic in the younger channel complexes. This is attributed to the behavior of the levee-generated confinement. The levees create partial confinement while providing some freedom, as they themselves are evolving adjacent to the channels. In this channel system, down-system and lateral migration styles are observed, and stacking styles are hard to predict.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009