380 University of California Publications in Geologij [Vol. 13 



As noted above, the fanglomerate is somewhat thinner on the north 

 side of the hill. On the next hill to the north the basalt rests directly 

 on the granite, and it therefore seems evident that, at the time the 

 detritus was deposited, the country sloped to the south. 



Between the basalt flows a stratum of similar material occurs, but 

 it is rather small and pinches out to the northwest. 



The Pipes fanglomerate is believed to be upper Pliocene or lower 

 Quaternary because it is older than the basalt flows ; yet it cannot be 

 much older, for it is parallel to them and similar material is found 

 between them. 



Basalt 



Areas of basalt are found along the south flank of the San Ber- 

 nardino Mountains, in the vicinity of The Pipes, and in the desert to 

 the north. They are merely the remnants of flows which probably 

 extended over a much larger part of the region previous to the uplift 

 of the mountain range. Several varieties are found and it is impos- 

 sible in any case to check different areas as portions of the same flow. 



Olivine basalt overlies the Hathaway sandstone between Hathaway 

 Canon and San Gorgonio River. Due to alteration it has a reddish 

 color, but a few rounded grains of olivine can still be recognized. It 

 dips to the west and is overlain by horizontal beds of fanglomerate. 

 On a small hill one mile west of Millard Canon volcanic rocks rest on 

 sandstone and are overlain by fanglomerate. For the most part the 

 volcanic material is basalt, the upper portion of which is vesicular. 

 Above this there is a thin stratum of soft, white, decomposed tuff. 

 Both are nearly horizontal. 



Between Millard and Deep canons the basalt lies across the eroded 

 edges of the Hathaway sandstone. The basalt and sandstone form an 

 anticline here, the south limb of which disappears before it reaches 

 Deep Canon, possibly due to faulting, while the north limb continues 

 east of Deep Canon for about half a mile. Fanglomerate overlies the 

 basalt and has been tilted with it. 



Red Dome in Whitewater Canon is an outcrop of olivine basalt. 

 About half a mile to the northeast there is a small area of schist 

 exposed to view by the stripping of the overlying fanglomerate and 

 on this there are several small patches of basalt. Practically all of 

 this is of a deep reddish color due to weathering and the resultant 

 oxidation of iron. Near the upper portions of some of these small 

 masses of basalt there are amygdules of chalcedony. 



