Print this pageDepositional History of Submarine Channel-Levee Systems Recorded by Levee Growth Patterns
SKENE, KENNETH I.
Submarine channels represent the major conduit for sand to the deep sea, but the history of channel activity is more reliably preserved in their associated levees. Levee growth patterns relate to the character of not only the overbanking turbidity current but also the related through-channel flow. Studies of geologically distinct systems suggest that the predominant levee growth pattern displays exponential thinning of depositional units perpendicular to channel trend. Lack of correlation between paleoslope and variations in the thickness of depositional units suggests that the slope- dependent parameters of turbidity currents, velocity and flow thickness, do not vary significantly across a levee, justifying a simple model for levee deposition. The model suggests that the morphological distinctiveness of channel-levee systems arises from differences in the grain sizes supplied to the levees. Flows moving down steep (or shallow) channels transfer coarser material to the levees than flows moving down lower gradient (or deeper) channels. This study suggests that muddy levees imply at least one of: muddy source, deep channel, and/or low channel slope. Sandier levees imply sandier source, shallower channel, and/or higher channel slope. Muddy levees coincident with a sand-rich source and a steep channel imply efficient transport of sand through the system, concentrating sand deposition on the lobe. Conversely, for comparable channel depths, muddy levees coincident with a sand-rich source and a shallow channel slope imply inefficient sand transport, concentrating sand deposition within the channel.