552 C. R. KEYES PROFILES AND STRUCTURES IN DESERT RANGES 



miles to the south of this point the axis passes 2 miles to the east of the 

 creek under the basalt field (figure 3). 



The inclination of the Tertiary beds is further emphasized by near-by 

 faulting. It seems very doubtful whether normal flexing has taken place 

 to any appreciable extent. 



At the south end of the Grapevine Mountains, and about 8 miles east 

 of the last mentioned locality, is a similar phase involving Tertiary strata. 



Figure 4. — Tilted Tertiaries of the Grapevine Range 



The rocks are highly tilted and rise 2,000 to 3,000 feet above the plains. 

 They are composed largely of coarse materials, gravels and sands, more 

 or less firmly cemented. Their high inclination appears to be due en- 

 tirely to faulting. This mass of rock forms an integral part of the tilted 

 block constituting the main range (figure 4). The structure is that 

 which is commonly called simple monoclinal. 



M 



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Figure 5. — Ancient Structures of the Vegas Range 



Like phenomena, also involving hard Tertiary gravel deposits of great 

 thickness, are seen 60 miles to the southward at the south end of the 

 Funeral range. 



The A^egas group of mountains is rather complicated. While there is 

 some gentle flexing, the principal tilting of the strata appears clearly to 

 be the result of deformation accompanying faulting. It is not improb- 



