450 University of California Publications in Geology [Vol. 7 



fresh-water mollusks occur at several 

 horizons in the beds. Shallowness and 

 the gradual lowering of the lake 

 level probably explain the scarcity of 

 marked features such as beaches, wave- 

 cut terraces and sea cliffs. A well- 

 defined pebbly beach is, however, re- 

 ported by Mr. W. L. Moody to occur 

 west of Cave Mountain. 



The Manix Beds are but slightly 

 consolidated, and the back-cutting 

 from the Mohave River develops on 

 them a subdued type of bad-land to- 

 pography with smooth slopes. As ex- 

 posed along the Mohave River between 

 Kouns and Afton, they nowhere ex- 

 ceed about seventy-five feet in thick- 

 ness. Their greatest thickness is 

 between Field and Afton. The beds 

 thin out gradually toward the west. 

 (See fig. l.j 



StratigrapMc Relations. — The bed- 

 ding planes of the uppermost fanglom- 

 erates and those of the Manix Beds 

 are very nearly parallel. Since the 

 former are alluvial deposits and the 

 latter lacustral sediments, exact paral- 

 lelism of bedding planes would hardly 

 be expected. The approximate paral- 

 lelism of the two sets of beds and the 

 apparent evenness of the waste-slope 

 surface on which the first lake de- 

 posits were laid down indicates that 

 alluviation, and not erosion, was the 

 dominant process on the fan surfaces 

 at the beginning of deposition of the 

 lake-beds, and therefore that the 



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