Deposition 



245 



Figure 203. Curves showing variation with facies or generahzed distance from shore of several components of the 

 sediments. Nearshore basins are Santa Barbara. Santa Monica, San Pedro, and San Diego: middle basins are Santa 

 Cruz. Santa Catahna, San Clemente. San Nicolas, East Cortes, and No Name; offshore basins are Tanner, West Cortes, 

 and Long. 



of solution accelerates as they become 

 smaller. Because the rate of deposition is 

 approximately equal to the rate of solution 

 and mechanical removal of grains, bedrock 

 is exposed for long periods of time, thereby 

 allowing slow-growing authigenic minerals 

 to accumulate if they form immovable coat- 

 ings on the rocks such as manganese oxide 

 and phosphorite, or large grains such as 

 glauconite and phosphorite nodules. Owing 



to these various processes, it is no surprise 

 that the sediments of shallow bank tops are 

 coarse-grained, highly calcareous, and con- 

 tain much glauconite and phosphorite but 

 little organic matter. 



The full sequence of major environments 

 and their sediments can be related by a series 

 of curves (Fig. 203). Grain size is coarsest 

 for the shallow sediments that are most ex- 

 posed to wave turbulence — beaches, shelves. 



