1922] Vaughan: Geology of San Bernardino Mountains 



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to be observed that those on the north strike N 35° E and dip 40° NW 

 while those on the south strike N 45° W and dip 50° SW ; the schists 

 on the north seem almost entirely fine-banded while some strata on 

 the south are as much as two feet thick ; the general color effect pre- 

 sented by those on the north is a medium dead grey while those on 

 the south have a decided bluish cast. These differences, particularly 

 those of strike and dip, are such as can best be explained by faulting. 



At the mouth of Big Morongo Creek there is a triangular block 

 of fanglomerate jutting into the range. That it has been dropped in 

 by faulting is evident; for the fault contacts with the schists are easily 

 seen on the north and east sides. The northern fault cuts across Big 

 Morongo Creek and dips 75° north so that the schists are overthrust 

 on the fanglomerate, which here dips 5° to 10° to the north. Farther 

 east the latter is warped so that the dips vary from horizontal to 

 28° south. The southeast side of this block is along the Mission Creek 

 scarp and it seems likely that it is the result of a subordinate move- 

 ment associated with the greater fault. 



The Mission Creek fault is of further interest because of its asso- 

 ciation with the San Andreas. In the uplift of the ridge between 

 San Gorgonio and San Bernardino peaks there has been movement on 

 both faults while to the northwest only the San Andreas was active 

 and east of Dry Morongo Creek only the Mission Creek. It thus 

 seems probable that the latter represents the eastern continuation of 

 the same line of weakness in the earth's crust as the San Andreas. 

 Details of the adjustments between these two faults are not clear, but 

 there is reason to believe that there is a fault down Stubby Canon 

 and another down Whitewater, and there may be others. 



Stubby Canon is remarkably straight and lines up with another 

 which drains to the north. In consideration of the heterogeneity of 

 the rocks, this, while not conclusive, suggests faulting. No actual 

 displacement could be observed in any strata, but on the other hand 

 no particular mass of rock could be followed across the canon. There 

 is even more evidence of a fault down "Whitewater Canon. On the 

 west side the metamorphic rocks rise rather abruptly to a consider- 

 able height above the basalt and Coachella formation on the east. 

 Furthermore, the latter is itself much faulted (pi. 22A). 



In Santa Ana Canon there has been faulting the nature of which 

 is not entirely clear. The presence of the Santa Ana sandstone-shale 

 formation at the bottom of a deep canon with steep walls of granite 

 and gneiss cannot be explained in any other way since such sediments 

 are deposited only in a country of low relief. This formation consists 



