150 



tilting proposed by Poland, e_t al, also is responsible for the 

 tilting of the northern flank of Santa Monica Canyon. 



A large percentage of submarine canyons have streams or 

 former streams entering into the head of the canyon. No 

 problem is involved in the origin of Santa Monica Canyon since 

 Ballona Creek is known to have flowed into the bay until 1825, 

 and probably flowed directly into the head of Santa Monica 

 Canyon when sea level was lower. Redondo Canyon, on the other 

 hand, has no historic, topographic, nor sedimentary record of 

 a former stream landward of the canyon. The only evidence 

 known which indicates that the region at the head of Redondo 

 Canyon may have had a stream is the existence of marsh or 

 lagoonal deposits at about sea level one-half mile inland. 



Although faulting may have played some role in the control 

 of Redondo Canyon, some additional agent is necessary to cut 

 the gorge. Two theories which are most commonly argued for 

 the origin of submarine canyons are? (1) subaerial erosion by 

 streams, and (2) erosion by turbidity currents. A detailed 

 discussion of these theories and others are unnecessary here; 

 however, it is necessary to briefly state the turbidity current 

 hypothesis. Sediments acctimulating on the shelf or in the 

 upper reaches of the submarine canyon periodically sltimp or 

 slide into deeper water. The material that slumps has a very 

 high water content and travels at a high velocity which is 

 assumed to have the power to erode the bottom and walls of the 

 canyons , 



It is obvious that there is no apparent abundant source of 

 sediments which could form turbidity currents; therefore, both 



