71 



material of similar size range occvirs on the shelf off the 

 Malibu coast, the median value and the arithmetic mean of 

 the median diameters are almost identical. Also, the range 

 of values for this parameter are not extreme. However, the 

 values for sediments in other depth ranges are widely diver- 

 gent, where considerable relic material is known to exist 

 and where there are abundant organic remains. The effect of 

 relic material is not evident in the depth range of 125 to 

 175 feet as it is in all other depth ranges of the shelf. 

 This, then, is the depth zone on the shelf where sedimentation 

 is probably taking place at the present time and where this 

 Recent material has covered older deposits. 



The coarse sediment occurring nearshore on the shelf 

 south of Redondo Canyon has been identified as relic red 

 sand which is possibly a submarine outcrop of the Palos 

 Verdes formation. This may be kept free of Recent sediments 

 by currents which flow from the center of the bay impinging 

 against the coast in this area or by the action of waves in 

 shallow water. The outer portion of this shelf is evidently 

 an area of deposition. The sediment there contains coarse 

 fractions of authigenic minerals and shell fragments similar 

 to the coarse fractions of sands on the outer shelf. Currents 

 sweeping over this portion of the shelf may create conditions 

 of slow or intermittent deposition and a removal of fine- 

 grained sediment similar to that postulated for the central 

 shelf projection as discussed later in the report. 



