Quantitative study of a Magdalena submarine channel (Caribbean Sea): implications for sedimentary dynamics

The quantitative analysis of the most recently active channel located on the tectonically active margin off Colombia (Caribbean Sea), provides for a tentative estimation of flow behaviour and its characteristics. The channel displays a sudden geometry change at the inflection point of the margin profile, changing from a channel with well to poorly developed levees. This does not differ from other channels developed on passive margins, except that levee upbuilding is relatively enhanced in the upper reaches and accentuated by sharp decrease in margin gradients. The inferred loss of most of the suspended fine grained fraction and the decrease in margin gradients favoured a flow evolution to sand-rich turbidity currents, a decrease in spill-over deposition and a consequent poor development of levees in the lower channel course. Local changes in flow thickness, concentration and velocity occur at avulsion points, scarps and deeps on the channel floor, as well as recent deposition due to the entrance of mass flow deposits into the channel. The breaks-of-slope produces local variations in flow thickness, concentration and velocity. Flows passing over small-scale slope breaks may have undergone hydraulic jumps leading to a decrease in flow velocity and competency, which in turn leads to erosion immediately after the slope break and increased deposition down slope.