53 



clay , they should be used in conjunction with Figure 1^ 

 which shows the location of samples containing gravel. 

 Gravel percentages were not contoured, as the samples with 

 gravel are few in number, and the extent of the distribution 

 is not as general or as well-known as that of the other 

 sediment components. In addition, much gravel apparently 

 is distributed over the entire bay at various depths below 

 the surface sedimentary cover. 



Coarse Fraction 



Properties of the sand fraction of sediments, such as 

 mineral assemblages, distinctive minerals, content and type 

 of organic remains, size, and shape can be used to gain an 

 understanding of the depositional history and source of 



sediments. The sand fractions of all sediments collected 



I 

 in Santa Monica Bay were examined with a binocular micro- 

 scope . From the mineral assemblages and distinctive minerals 

 or components, the following six distinct sand types were 

 established? (1) fine quartz-feldspar sand, (2) rock-fragment 

 sand, (3) glauconite sand, (4) phosphorite-glauconite-shell 

 sand, (5) shell sand, smd (6) red sand (Fig. 19 ). As the 

 classification into types is often based only on distinguishing 

 components, the areas of occurrence are not considered mineral 

 provinces, but rather as areas having acctunulations of dis- 

 tinct minerals or mineral assemblages. 



