144 SOUTHERN CALIFO'RNIA GEOLOGY 



INTERIOR EAST-WEST FAULTS OF THE 

 MASTER HIGHLANDS 



Several subordinate ridges and valleys of the sum- 

 mit region of the San Bernardino Highlands extend 

 in east-west directions, as will be seen on the topo- 

 graphic maps. These may be the vestiges of ancient 

 folds and faults of similar directions, which prevailed 

 in the ancient peneplain, of which the summit region 

 represents a remnant, before it was dismembered into 

 segments and certain of its blocks elevated into the 

 present master highlands. 



There are also several suggestions of the east-west 

 rifts in the San Gabriel Range, for some of its peaks 

 survive along east-west lines, while many of the val- 

 leys have similar directions and are followed by the 

 heads of the San Gabriel, Bouquet and other canyons. 

 The great east-west Cucamonga fault which makes 

 the south border of the east half of this highland 

 has been previously mentioned as a portion of the 

 Anacapa lineament. 



Minor evidences of the east-west structure system 

 are seen in the trends of some smaller features, such 

 as the Eagle Rock Valley and the Raymond Hill fold 

 south of Pasadena, the First Street anticline and Sun- 

 set Boulevard faults in Los Angeles, and probably the 

 axial directions of the San Jose and Montebello hills. 



SUGGESTED EAST-WEST RIFTS OF THE 



DESERT SIDE 



The newly made topographic sheets of the Desert 



Side contribute many new and unsuspected data. They 



enable us to show some hitherto unrecorded lineaments 



in the physiography, which confirm some of the deduc- 



