118 



deposition surfaces is not yet clearly understood, but it is 

 known that in most cases it is due to by-passing of fine sedi- 

 ments by currents or turbulence. 



If HjulstrcJm's calculations are approximately correct, 

 then the average velocity of the bottom currents on the outer 

 shelf is not sufficiently strong to cause erosion in the area 

 nor prevent the deposition of fine sediments. This does not 

 mean that strong currents or turbulent action do not, at times 

 occur. There are insufficient data to determine whether the 

 sediment by-passes the region of nondeposition or is deposited 

 and periodically removed by occasional strong turbulence and 

 current action. Since much greater velocities are required 

 to move sediment after it has been deposited than to transport 

 sediment in suspension, it might be reasonable to conclude 

 that the sediment by=passes the area. 



Turbulence resulting from internal waves and eddy currents 

 are possibly the cause in this case for nondeposition. However, 

 it is also possible that occasional storm waves, shore wave 

 reflection, and to a minor extent tidal currents may be impor- 

 tant. 



SOURCE, TRANSPORTATION, AND DEPOSITION OF 

 SEDIMENTS IN SANTA MONICA BAY 



Source of Sediments 



The principal sedimentological studies undertaken during 

 the course of this survey have been descriptive in nature. 

 As a result, the discussion of sources of sediments is primarily 

 based on published and unpublished data. 



