388 University of California Publications in Geology [ VoL - 13 



a few low ridges are left. Just west of Pine Lake there is an outcrop 

 of rather well cemented fanglomerate dipping 10° to the north and 

 containing unsorted angular boulders up to eight inches in diameter. 

 Its exact significance is not known, but it lies beneath the other fan- 

 glomerate and may represent an earlier phase of the same deposition. 

 On the north side of the valley, between Poligue and Van Dusen 

 canons, there is considerable fanglomerate, but it is of recemented 

 limestone fragments, the same sort of material to which the Spanish 

 term ' ' caliche ' ' is applied. 



Holcomb Valley is nearly surrounded by flat ridges of fanglom- 

 erate. Those on the south and east sides are particularly conspicuous 

 and consist of limestone, granite, and quartzite from the surrounding 

 hills. The quartzite, because of its greater resistance to erosion, is the 

 most prominent constituent over a large part of the area. On the 

 north side of the valley from Caribou Creek northwestward for a mile 

 this fanglomerate has been worked for placer gold. 



The nature of the erosion of the fanglomerate deserves particular 

 attention. The flat between Rathbone Creek and Erwin Lake is cut 

 up with gullies, but there are no alluvial fans at their mouths. In 

 some of these gullies there are grassy meadows and the floor of the 

 valley is loamy meadow land. In Holcomb Valley the same condition 

 obtains. It thus appears that the erosion here is more of the nature 

 of that taking place under humid conditions than that which is active 

 along the flanks of the mountains or was active in the mountains at 

 the time the fanglomerate was deposited. The dependence of this 

 on the uplift of the mountains has already been discussed and needs 

 no further mention. 



The fanglomerate in Bear and Holcomb valleys is only a local 

 representative of a widespread deposition during the third cycle of 

 erosion. Similar fanglomerates are found in many other valleys and 

 canons and along the flanks of the mountains. 



In Santa Ana Canon fanglomerate unconformable overlies the 

 sandstone-shale formation and, although deeply incised by recent 

 streams, it still has the general appearance of being the valley floor. 

 It consists largely of somewhat angular granitic and gneissic boulders, 

 some of which are as much as eight feet across, from the ridges on 

 either side, with a matrix of similar material differing only as to size 

 of fragments. The whole mass is but loosely consolidated and the 

 color is usually reddish or yellow. The fanglomerate extends high up 

 on the sides of the canon and on the south side there are numerous 

 talus cones along the upper edge. This is an important feature in 



