1922] Vaughan: Geology of San Bernardino Mountains 385 



the older rocks to the north. They contain a notable proportion of 

 rounded material, but this, since it may be true locally of any fan- 

 glomerate, is unimportant. The upper also contains strata of sand- 

 stone quite comparable to that in the Hathaway. 



In consideration of the foregoing facts it seems probable that the 

 fanglomerate above the basalt was laid down under conditions some- 

 what similar to those which controlled that below, i.e., before the 

 uplift of the mountain mass, or before this uplift had become of great 

 importance. 



The older desert deposits. — In the desert along the north side of 

 the range there are isolated outcrops of sedimentary rocks whose age 

 is rather uncertain. They have been cut by recent erosion and in 

 some cases, where the nature of the material indicates the conditions 

 of deposition, the time with regard to the uplift may be inferred. 



Horizontal sediments are exposed on the east side of the hill a 

 mile west of Cushenbury Springs. In the lower fifty feet the deposit 

 consists of grains of quartz and flakes of biotite in a fine earthy matrix 

 of light brownish color. Toward the top there are a few strata of 

 coarse detritus, the larger fragments being about two inches in diam- 

 eter. This is unconformably overlain by nearly horizontal beds of 

 coarse fanglomerate, some portions of which are firmly cemented with 

 lime, but on the whole similar to that now being deposited along the 

 foot of the mountains. The sequence indicates that the lower strata 

 were laid down before the uplift of the mountains to the south and 

 the uppermost strata after this uplift was well advanced. The finer 

 material could hardly have been laid down at the base of a steep scarp, 

 but rather in a country of low relief, while the fanglomerate is typi- 

 cally laid clown in such a position. 



East of Old Woman Springs the basalt just before it disappears 

 is overlain by coarse sandstone containing fragments of quartzite. 

 Above this there is a soft sandy shale and still higher a fanglomerate 

 which makes up a large part of the bench as it continues to the south- 

 east. The sandstone immediately above the basalt has a clip to the 

 south of 5° to 15°. Just north of the basalt similar strata dip to the 

 north at about the same angles. The outcropping basalt does not dip 

 beneath them, but abuts against the strata, so that either there must 

 be a fault or the basalt was much eroded before the deposition of the 

 sediments. In considering the structure other evidence will be pre- 

 sented which seems to indicate faulting. These finer beds were evi- 

 dently laid down before the mountain mass to the south attained its 



