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water in submarine canyons below the surface of the surrounding 

 shelves is relatively quiet. Here, fine-grained sediments can 

 accumulate o Coarser sediments that are transported across the 

 shelf also have a tendency to accvimulate in depressions such 

 as these canyons. Along the axis of a canyon, finer material 

 is often interspersed with coarse material that has slumped 

 down the canyon walls or has been trapped as noted above. 

 This is the case in Redondo Canyon (Fig, 13). 



Fine-grained deposits in the submarine canyons may be 

 carried there by density currents. The axis of the pattern 

 formed by the median diameters in Santa Monica Canyon is 

 shifted to the north from the topographic axis of the canyon. 

 This may be due to the fact that the south wall of the can- 

 yon is steeper than the north slope j, resulting in considerable 

 slumping of material from the south slope, but allowing sedi- 

 ment to accumulate normally on the north side with a minimum 

 of movement by slumping. 

 Relation of Median Diameters to Depth 



The expected pattern of sedimentation on a continental 

 shelf, and to some extent on the steeper slopes at the edge of 

 the shelf, is that median diameters will decrease with depth. 

 This is due to increasing distance from shore, the source of 

 the detrital material, and to a reduced competency of trans- 

 porting agencies with depth. Thus, an ideal isopleth map of 

 median diameters in this environment should show them decreasing 

 with depth and more or less closely related to submarine topo- 

 graphy, Detrital material of sand size which is moved by 

 traction and saltation should show an offshore decrease. 



