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



The cross-section of the Hot Creek range (figure 8), as given by Spurr, 

 presents almost conclusive evidence of the perfect independence of the 

 rearing of the mountains and the flexing of the region. In a broad way 

 a part of the range may be regarded as a low arch repeatedly faulted and 

 covered on one side by an immense thickness of eruptives. The profile is 

 mainly erosional, not structnral. 



That there was some orogenic movement of the region of the nature 

 of faulting rather than flexing is shown in the dislocations which the 



Figure 8. — Faulted Arch in Hot Greek Range 



very late basalt flows have undergone. This phase of the subject has 

 also been taken up by Lauterback^^ in western Nevada. This author's 

 Muttleberry Canyon cross-section (figure 9) of the Humboldt range is 

 well worth careful examination in this connection. 



Numerous examples other than those mentioned above are given by 

 Spurr.^* 



So far as the Great Basin province is concerned the accumulated testi- 

 mony goes to show that the characteristic fiexure structures of the moun- 



FiGURE 9. — Ancient and Recent Tectonics of Humtoldt Range 



tain ranges that are displayed at the present time are mainly those of an 

 ancient system of tectonics, in no way genetically related to the rearing 

 of the mountains as they now appear, as noted by Button and Eussell 

 especially; that in some of the ranges the rock-complex, with its ancient 

 tectonic features, has been faulted in comparatively recent times, and 

 that these minor slippings have more or less clearly impressed themselves 

 upon the local relief by producing tilted block-ridges, as lately described 

 by Spurr, Lauterback, and Davis ; that in the majority of cases the great 



13 Bulletin of the Geological Society of America, vol. 15, 1904, pp. 289-364. 

 " Bulletin of the Geological Society of America, vol. 12, 1901, p. 217. 



