63 



slope north of Santa Monica Canyon . The sand on the shelf 

 south of Redondo Canyon contains a high percentage of 

 glauconite and is similar to the material on the slope off 

 the outer shelf. 



The accumulation of glauconite sand is limited to the 

 zone of variable micro-relief on the outer edge of the shelf 

 and on the basin slopes. 



Median Diameters 



Definition and Significance 



The median diameters of the bay sediments have been deter- 

 mined from graphs of the cumulative frequency by weight of the 

 diameters of particles occurring in the sediment samples. The 

 median diameter is the diameter of the central grain separating 

 equal weights of particles coarser and finer than the median 

 grain. 



The median diameter can be used to determine the manner 

 of formation of a sediment as it relates to the strength of 

 currents which transport and deposit the individual particles. 

 However, transportation and deposition of sediments are 

 complex procedures with many variables, and the relation be- 

 tween median diameters and the agencies of transportation and 

 deposition are too little known at present to allow rigorous 

 analysis in this fashion. The main use of median diameters 

 is to indicate the relative size of the sediment for mapping 

 purposes, and for the determination of the distribution patterns 

 which can be used in conjunction with other components, such as 

 composition. In this manner, known processes in the ocean 



environment can be related to the occurrences of different 

 .tvoes of sediment o 



