2G2 J. E. SPURR — ORIGIN AND STRUCTURE OF THE BASIN RANGES 



in post-JnraPsic time; the other, of strictly vertical action, presumably within the 

 Tertiary, in which there are few evidences or traces of tangential compression." 



Major Button, in 1880,* followed closely the coni promise views of 

 King. He discussed the folding in the Great Basin ranges of Utah as 

 follows : 



** These flexures are not, so far as can he discerned, associated with the building 

 of the existing mountains in such a manner as to justify the inference that the 

 flexing and the rearing of the ranges are correlatively associated. On the contrary, 

 the flexures are in tiie main older than the mountains, and the mountains were 

 blocked out by faults from a platform which had been plicated long before, and 

 after the inequalities due to such pre-existing flexures had been nearly obliterated 

 by erosion. It ma}' well l)e that this anterior (inrvation of the strata has been 

 augmented and complicated by the later orographic movements. But it is not 

 impossible to disentangle the distortions which antedate the uplifting from the 

 bending and warping of the strata which accompanied it, and it is only the latter 

 that we can properly associate and correlate with the structures of the present 

 ranges. These present no analogy to what is usually understood by plication. 

 The amount of bending caused by the uplifting of the ranges is just enough to 

 give the range its general profile and seldom anything more." 



It will be seen that Button's views favored more strongly the fault 

 hypothesis than did King's. King believed that plication had been an 

 important factor in creating the ranges, while Button supposed that the 

 surface effects of folding were obliterated by erosion, which reduced the 

 country to a comparatively level platform. Subsequently this plicated 

 ])latform was broken by powerful faults, like those of the Colorado 

 plateau, into a number of l)locks, which w^ere uplifted and tilted so as to 

 form ranges. These ranges, according to this idea, are actually raono- 

 clinal blocks in origin, although not necessarily or even generally so in 

 structure. 



The explanations of Button were adopted almost exactl}^ by Professor 

 I. C. Russell. In 1884 he wrote as follows : f 



" The whole of the Great basin thus far explored is remarkable for the persistency 

 of a single type of mountain structure. This is the simplest of orographic forms, 

 and has been already mentioned as a tilted block, bounded })y faults. The whole 

 immense region lying between the Sierra Nevada and Rocky Mountain systems 

 has been broken by a multitude of fractures, having an approximately north-and- 

 south trend that divides the region into long, narrow orographic blocks. These 

 have been tilted so as to form small but extremely rugged mountain ranges, often 

 from 50 to 100 miles in length, with a width of but a few miles. This region may 

 be classed as a ' zone of diverse displacement' of vast dimensions.! If we draw 



* Geology of the High Plateaus of Utah : U. S. Ueog, and Geol. Surveys of the Rocky Mountain 

 Region, p. 47. 

 t Fourth Ann. Rept. U. S. Geol. Survey, p. 443. 

 X For types of displacements consult "Geology of the Uintah Mountains," Powell, pp. IG, 17. 



