332 University of California Publications hi Geology [Vol.13 



The valley southwest of Smart's Ranch probably belongs to the 

 third cycle, for it is cut down sharply below the east end of Bear 

 Valley and its walls are more rugged and rise more steeply. 



A broad valley floored with fanglomerate lies southeast of Mound 

 Spring. It forms the divide between separate drainage systems, and 

 is therefore not a feature of the present cycle. The upper portions 

 of the hills to the north are rounded and compare favorably with those 

 around Bear Valley and the upper Santa Ana. On the crest of the 

 ridge immediately to the south there is a large stretch of even topog- 

 raphy extending nearly to the head of Antelope Canon. This may 

 well be a remnant of an earlier cycle or subcycle. The top of the 

 ridge east of the valley is also flat. In both of these cases the tops of 

 the ridges are quite distinct from the sides and in no way can they be 

 considered merely the rounded hilltops of a topography of consider- 

 able relief, but rather the remnants of a very old surface. Because 

 of the way in which it is cut down below these older rounded features 

 the valley is believed to belong to the third rather than to the second 

 cycle. 



The valley east of The Pipes has almost identically the same rela- 

 tionships to the surrounding country as that near Mound Spring. It 

 is floored with fanglomerate, and remnants of an older topography are 

 found on the hills south and west of The Pipes and also to the east. 

 Between this valley and Rock Corral there is a plateau which is re- 

 markably like the Bluff Lake country. It is covered with low hum- 

 mocks of granite which are being buried in their own detritus, and 

 north of Saddlerock Spring for about two miles there are areas where 

 the granite is completely buried recalling the panfan or end stage of 

 desert erosion. The streams are meandering and of low gradient, but 

 along the north front of the range they drop off precipitously, sug- 

 gesting faulting. The bareness of the hummocks in the northern por- 

 tion of the plateau is probably due to the removal of detritus by these 

 streams. West of this plateau the hills rise rather abruptly, but not 

 in a straight line as would be expected if due to faulting. This feature 

 is far more likely due to one of the phases of desert erosion. North- 

 west of Negro Butte there is an extensive granite surface sloping very 

 gently to the north and disappearing under the alluvium. Where it 

 first emerges from the alluvium it is almost unbroken, but farther to 

 the north numerous small gullies cut across it ; and finally these gullies, 

 while not deep, become conspicuous with low but rugged ridges be- 

 tween, identically like the plateau north of Saddlerock Spring. This 



