Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
AAPG Annual Convention, Houston, Texas, April 9–12, 2006
Insights into Reservoir Characteristics of Sinuous
Deepwater Channel Fills from Outcrop Analogs—Part I: Stratigraphic
and Sedimentologic Evolution of a Sinuous Slope Channel-Fill,
Beacon Channel outcrop is a rare, three-dimensional exposure of a sinuous slope channel-fill. The channel is 10m thick, 250m wide and is exposed on five separated cliff faces in 1 km2 area. In plan view the channel has a sinuosity of 1.2. The scale and geometry of Beacon Channel is similar to the smallest-scale, seismically resolved stratigraphic features in W. African slope channel complexes.
The stratigraphy of the Beacon Channel is subdivided into four packages, each recording a distinct phase of evolution. From oldest to youngest they are: (1) sandstone-rich strata that precede channelization, (2) point-bar package, (3) plug package, and (4) bedded package. The sandstone-rich strata that precede channelization are interpreted to be lobes associated with a basinward-propagating channel. The point-bar package contains laterally accreting sandstone-rich bars, similar in cross section and plan-form to fluvial point bars. The bars record a phase of down-cutting, bypass, and increasing channel sinuosity. Paleocurrents from the bars record a secondary flow cell that rotates in an opposite direction to secondary flow cells in rivers. The plug package contains thickly bedded, structureless and cross-bedded sandstones. These strata lap out onto the lateral margins of the channel. The plug package records a time of minimal sediment bypass and decreasing thalweg depth due to filling of the channel. The bedded package contains strata that lap out against the lateral margins of the channel. These are the finest grained strata in the channel and they record the final fill and abandonment of the channel.