Hydrodynamic model of the Blake Outer Ridge

Formation of the Blake outer ridge by differential deposition of sediment on a relatively flat-lying floor (horizon A) is discussed on the basis of the hydrodynamic interaction of two oppositely directed currents, which are decelerated in the interaction zone and diverted to a final direction taken to be the trend of the Blake outer ridge. If one or both of the currents carry sediment, deposition occurs preferentially in the region of decelerated flow, so that sediment distribution is governed by the steady-state velocity field. Streamlines and isotachs computed from a model of two-dimensional streamline flow are found to be consistent with the known sediment distribution; they require upstream current widths in substantial agreement with estimated widths of the Florida Current and the Western Boundary Undercurrent. The results suggest further that the Florida Current contributes relatively coarse sediment; the undercurrent, very fine sediment.