i 



{ 157 



\ 

 accumulation of finer material. Fine sediment may ^e deposited 



in this area, but is removed or reworked more of ten^ than in the 



areas close to shore o \ 



The central shelf projection contains an area oi rock and 



I 



gravel, and the sediment distribution is patchy over Vthe entire 

 area,, Topographic evidence indicates mounds and depressions. 

 Sediments here contain authigenic mineral grains and s^ell 

 fragments which are often considered to indicate an environ- 

 ment of non-deposition, yet the sediment containing these 

 components is often fine grained with appreciably amounts of 

 silt and clay. It is, therefore, an inescapable conclusion 

 that a large portion of this area is receiving sediment. In 

 all probability, deposits are accumulating in depressions on 

 this surface, and the small prominences which are the loci of 

 formation of authigenic minerals and of shelled animals are 

 being swept free of sediment. Most of the gravel area is 

 probably covered by fine-grained material, and gravel at the 

 surface is limited to the vicinity of the rock outcrops. 



The percentage of calcium carbonate increases in an off- 

 shore direction. It is generally low over most of the shelf 

 and slightly higher on the offshore slopes. The exceptions to 

 this distribution are the high percentages found in patches 

 on the central shelf between Santa Monica and Redondo Canyons, 

 Almost all the czilcium carbonate is derived from shell debris. 

 High percentages indicate that deposition in these regions is 

 slow and that little sediment derived from land is deposited. 



The highest values of organic carbon are found beyond 

 the shelf break. The distribution follows closely the 



