Basins and Troughs 



225 



as organic carbon or nitrogen) than the finer- 

 grained muds that overlie and underlie it 

 (Fig. 192). For basins bordering the main- 

 land, calcium carbonate is less abundant in 

 the coarse-grained layers than in the finer 

 muds; for Santa Catalina, San Nicolas, and 

 San Clemente Basins at intermediate dis- 

 tances from shore some layers have more 

 and some less carbonate than the muds; and 

 for the far-ofl'shore basins carbonate is gen- 

 erally more abundant in the sand layers than 

 in the muds. Shallow-water Foraminifera 

 (Crouch, 1952) and glauconite in sands from 

 the offshore basins closely resemble these 

 components in sands from bank tops and 

 island shelves. Detrital heavy minerals of 

 West Cortes Basin are dominated by augite 

 as are sands on the nearby Cortes Bank, but 

 heavy minerals in sands from San Pedro and 

 Santa Monica Basins are dominated by 

 hornblende like the sands from the adjacent 



mainland shelf. Among the light minerals 

 feldspar is so abundant that the sands are 

 properly termed arkose. 



Table 16 



Apparent Depth of Burial of Two Sand Layers 

 (Apparently Sand) in San Diego Trough 



West of San Diego 

 AS Read from Precision Depth Recorder 



Figure 1 92. Analytical data for 

 core from Santa Cruz Basin. 

 Note the effects of grain size 

 on other parameters. From 

 Emery and Rittenberg (1952, 

 Fig. 9). 



0.050 0.075 0.100 0.125 



490 CM CRAY SAND 



776 CM SILTY MEDIUM GREEN SAND 



784 CM MEDIUM GREEN SAND 



7S8 CM COARSE CRAY SAND 



7. N 

 %C/|o-A 



50-4/Cl- 



CORE 1941 



LAT. 33° 44' 10" 

 LONG. 119° 30' 30" 

 DEPTH -6420 FEET 



