From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, January 27, 2006
Stratigraphic and Hydrodynamic Concepts Learned from a
Slope channels are common bathymetric features on continental slopes. Often sinuous, they are inherently related to levees, crevasse splays, and terminal lobes. Slope channels have long been recognized as conduits for sediment transported into the abyssal plain, and their levees constitute a significant volume of slope sediment. Slope channels are significant oil and gas reservoirs on many of Earth's continental margins, including West Africa. Outcrops provide a unique scale of observation with which to study slope channels.
The Beacon Channel exposure is a rare example of a three-dimensional outcrop of a sinuous slope channel. The channel, 20 m thick and 250 m wide, is exposed on five separate cliff faces in an area of 1 km 2. An integrated data set consisting of lidar, paleocurrent measurements, stratigraphic columns, and photopanels was used to characterize the stratigraphy of the Beacon Channel.
This talk will focus on stratigraphic and hydrodynamic concepts learned from this unique exposure. Concepts include (1) sweep, swing, and sinuosity; (2) channel evolution and channel hierarchy; (3) symmetry; (4) secondary flow; (5) levees; (6) aspect ratios; (7) distribution of facies; and (8) matrix for relating seismic scale stacking patterns to subseismic scale attributes. These concepts offer significant contributions to our knowledge of sinuous slope channels. Many of these concepts cannot be addressed using any other form of data (seismic, seafloor, or flume).