161 



location during the present cycle of sedimentation. It was 

 probably transported and deposited in the littoral zone during 

 a Pleistocene lowering of the sea. Its source was the bedrock 

 outcrops nearby and/or fluvial transport to its present 

 location by streams flowing from the east - presumably Ballona 

 Creeko The gravel is flanked by coarse-to medium-grained 

 sand containing a great proportion of rock fragments. These 

 rock fragment sands are thought to have been deposited at 

 the same time as the gravels. 



Phosphorite 



Phosphorite occurs in the sediment over the outer shelf 

 and on the outer edge of the shelf south of Redondo Canyon, 

 The presence of phosphorite is indicative of slow or non- 

 deposition of sediment in these areas. 



Geologic Structure 



The increase of the thickness of overbtirden in a shore- 

 ward direction from the central shelf projection indicates 

 that the bedrock area is high and that a trough exists near- 

 shore where great thicknesses of sediments have accumulated 



Two theories are presented to explain the geologic 

 structure of the outer shelf? (1) a continuation of the Palos 

 Verdes fault zone into the bay in which the outer shelf has 

 been uplifted in relation to the nearshore area, or (2) the 

 underlying consolidated rock dips gently toward shore with 

 bedrock exposed on the outer shelf. 



The absence of schist among the rocks dredged from Santa 

 Monica Canyon by other investigators may indicate that the 



