110 



deep water probably represents a deposit laid down in the 

 geologic past? (3) The occurrence of rocks bored by organisms 

 gives strong evidence of a littoral or shallow water environ- 

 ment at the time the rocks were inhabited by animals. If the 

 depth is now considerably greater than the depth-habitat of 

 the boring organisms, it ratist be presumed that sea level has 

 risen and that little sediment has subsequently accumulated; 

 (4) the presence of coarse terrigenous sands separated from 

 the shore by finer sediments probably indicates at least two 

 periods of deposition? (5) the presence of glauconite, phos- 

 phorite, and high percentages of CaC03 are indicative of slow 

 or no deposition^ On the other,hand, much of the area in 

 Santa Monica Bay which exemplifies the above criteria also 

 has up to 30% silt and clay in the sedimentary material. 

 Deposition, then, does occur, but is either extremely slow 

 or is intermittent with a periodic resuspension of the 

 material. 



As pointed out by Fleming and Revelle (1939), and Revelle 

 and Shepard (1939), the primary force necessary to transport 

 sediment is the "static bottom friction" on sedimentary par- 

 ticles. If some force lifts a sediment particle even for a 

 brief moment, then any resultant force (current or turbulence) 

 acting in a constant direction, no matter how small its magni- 

 tude, will effectively transport the particle. On a topo- 

 graphic high, the net result would be a winnowing of the 

 detrital material of a size determined by the force which is 

 competent to put the particle in suspension. Thus, the sedi- 

 ment would be transported from a topographic high area to a 



