102 



One dredge haul (station number 3268) made on the outer 

 shelf contained schist. Since the fragments were large and 

 freshly fractured,, it is probable that the dredge struck bed- 

 rock. This dredge haul was somewhat unique in that all other 

 hauls from this part of the shelf recovered only sedimentary 

 rock or well-rounded gravel. None of the gravel was composed 

 of schist, but occasional small fragments of schist were found 

 adhering to pieces of shale. 



Gravel 



Most of the gravel on the shelf is well-rounded and 

 ranges in size from granules to cobbles. It is composed 

 mainly of igneous rock, but raetamorphic and sedimentary rocks 

 are also represented. The Appendix lists the transported 

 rocks according to lithology, and Figures 14 and 32 show the 

 areal distribution of gravel recovered from the surface of 

 the sea floor. 



Most of the sampling in the bay was done with a snapper 

 sampler which gathers about two to four cubic inches of sedi- 

 ment. The Hayward grab, used for obtaining biological speci- 

 mens, collects up to three cubic feet of sediment. The material 

 collected by both sampling devices appeared to have similar 

 characteristics, but after screening the samples obtained by 

 the grab, there frequently remained considerable quantities 

 of gravel which was not always recovered in nearby snapper 

 samples. Most of the gravel does not exceed a few centimeters 

 in diameter. Gravel is evident in the wash-borings made along 

 the proposed and old outfall lines shown in Figure 31. From 



