690 DESCRIPTIVE GEOLOGY. 



the Havallah Range, they almost invariably approach more or less closely 

 to a north and south course. This change in the strike of the beds, 

 approaching a right angle to the main trend of the range, shows itself in a 

 marked manner in the detailed topographical structure, where the main 

 drainage-channels are developed in north and south lines, traversing the 

 course of the beds, which are inclined at high angles. On the east and west 

 slopes, the sulcations lying with the strike of the rocks are of only second- 

 ary importance, never reaching up as far as the higher summits and ridges. 

 The present water-channels naturally follow the main cations of the mount- 

 ain to the base, where they turn, flowing toward the valleys along the incli- 

 nation of the later Mesozoic beds. 



It is worth observing here that the strike indicated by the mass of 

 Granite Mountain is again hinted at by the recurrence of Archaean schists in 

 Wright's Canon, West Humboldt Eange, where they have a strike of north 

 50° east, and again in both branches of the Havallah Range, with a trend 

 northeast and southwest. The granite appearing directly under the Koipato 

 and Star Peak Triassic in all three of these uplifts, the Havallah, Pah-Ute, 

 and West Humboldt, indicates either a broad granite range, or else a high 

 granite plateau, during the period of deposition of the Triassic formations. 

 There is some reason to believe that it was simply a high granite range, for 

 the same conditions of direct superposition of the Triassic over the granites 

 are not observed either to the northeast or southwest of these three ranges. 

 In fact, with the limited exposures near New Pass in the Desatoya Mount- 

 ains, one or two isolated localities in the Augusta Mountains, and the 

 broken masses which rise above the general overflows of igneous rocks to 

 the west, these three ranges form the entire development of Triassic rocks in 

 this part of Nevada. That they extend southward beyond the limits of this 

 exploration into the lone region is known. They have been described as 

 occurring in Plumas County, California, by Prof. J. D. Whitney,^ and have 

 been observed by Mr. Clarence King in the Blue Mountains of Oregon. 

 The most interesting problem connected with their occurrence is the cause of 

 their discontinuance to the eastward beyond the Havallah Range Whether 

 there has been an absolute unconformity between the Triassic of the Haval- 

 ' Geological Survey of California, vol. i, 309. 



