Kinematic Evolution of a Deep-Water Channel-Levee System, Eastern Gulf of Mexico

Abstract:

Deep-water channel systems represent the primary conduits of terrestrial sediment to the continental margins and ocean basins. They play an important role in the construction of continental margins, can host valuable resources, and act as repositories of organic carbon.

Initial work has suggested that deep-water channels develop their sinuosity early on, reach a planform equilibrium, and then undergo near-vertical aggradation during which channel migration is limited and cutoffs are rare. High-resolution 3D seismic-reflection data of a deep-water channel system located in the Eastern Gulf of Mexico presents a unique opportunity to document its kinematic evolution and test these ideas.

By mapping individual channel forms, we document how the sinuosity of the channel through the evolution of the belt increased from an initial 1.2 through to 2.2, just prior to abandonment. The channel appears to laterally migrate and translate downstream during its evolution, and it becomes sinuous enough that a neck cutoff develops. We demonstrate how this cutoff induced a rapid shift in the direction of lateral migration of the channel in its immediate vicinity. In addition, the planform morphology of the earliest channel seems to be a key determinant on the location of the cutoff.

Using the concept of channel trajectories we show similarities in planform kinematic processes between submarine and fluvial systems. A key difference is the much higher degree of aggradation occurring in deep-water channels. We quantify how variable lateral migration rates along channel drive variations in stacking architecture through the belt. As a result, the aspect ratio (belt-width/belt-height) of the entire channel belt varies between 2.7 and 31. Such a large range suggests that the intra-system variability can be as high as the variability across multiple systems.