CHAPTER XXVI 

 A LATER STUDY OF THE BASIN RANGES 



THE BASIN RANGES ARE LONG NEGLECTED 



There is little published indication that the origin of the basin ranges continued to occupy 

 Gilbert's attention after he left the Wheeler survey. He saw many of the ranges while he was 

 studying irrigation problems under Powell and Bonneville problems under King; but other 

 duties appear to have been so engrossing that the basin-range problem was laid aside. His 

 habit seems to have been to discharge past problems from his mind and to concentrate his 

 attention upon problems in hand. In any case he took no public part in the discussion that the 

 problem aroused during the years just before and just after the organization of the national 

 survey. Very little mention of it is found in his writings for a period of 25 years after he left the 

 Wheeler survey, most of his work during that time being in the East; nevertheless he must have 

 followed the discussion while it was conducted by others, and in particular the additions con- 

 tributed by Powell and Dutton to his tersely outlined views of 1875 must have been known to 

 him. Nevertheless, such brief mention as he made of the basin ranges in connection with 

 studies of other subjects took no account of these additions; the only novel elements in his 

 own brief statements concerned the recent and low fault scarps in the piedmont alluvium and 

 the much larger signs of faulting seen in the spur-end facets, as will appear from the follow- 

 ing extracts, the first of which, however, merely repeat his original understanding of the 

 problem. In connection with the possible occurrence of earthquakes in the district of Salt Lake 

 City, the brief statement was made in 1884 that "a majority of the mountain ranges [of the 

 Basin] have been upraised by the aid of a fracture at one side or the other, and in numerous 

 instances there is evidence that the last increase of height was somewhat recent." ' Similarly, 

 the chapters prepared by Gilbert on the Salt Lake region in the guidebook for the western 

 excursion that followed the International Geological Congress at Washington in 1891 concisely 

 announced: 



The mountain ridges of the Great Basin are due directly to uplift [(p. 263); . . . the mountains of the 

 Great Basin are, in large part, carved from orogenic blocks uplifted along fault planes. The displacements, 

 which were probably initiated in Mesozoic time, were continued during various Cenozoic epochs, and are now in 

 progress. The steeper faces of most of the mountain ranges are rugged escarpments primarily due to faulting 

 and at their bases are frequently to be found smaller [alluvial] escarpments of so recent date that the traces of 

 subsequent erosion are scarcely perceptible (p. 376). 



The [Wasatch] mountains towering above the Utah valley are of wonderful boldness and beauty, and their 

 precipitous faces are such as result from no orogenic process save that of faulting (p. 396) 



A somewhat more explicit statement was made elsewhere: 



A range consisting of a faulted block generally has a bold front on the side of the fault, and is less abrupt on 

 the opposite slope. On the side of the bold front the line separating the rock of the mountain from the alluvium 

 of the valley [intermont trough] is simple and direct, while on the opposite side it is tortuous. 8 



At the time of the International Geological Congress and excursion, Gilbert's attention 

 seems to have been given less to the larger features of the range margins than to the little fault 

 scarps in the alluvium near the base of the ranges. This was perhaps natural because the 

 little scarps had not been understood, even if they had been seen, by Gilbert during his service 

 on the Wheeler survey; he first noticed them in 1876, when he was in Utah for the second 

 season of work on the Powell survey. Brief reference is made to them in the address on the 

 "Inculcation of scientific method," above analyzed; it is there announced that their "discovery 

 was something more than the finding of a post-Bonneville fault; it was the discovery of a new 

 method of recognizing faults — of a peculiar type of cliff produced by faulting, which tho by no 

 means obscure had previously been overlooked by geologists." The occurrence of similar 



' Amer. Journ. Sci., xxvii, 1884, 49-53. 



• Lake Bonneville. U. S. Qeol. Surv. Monogr. 1, 1S90, 340. 



20154°— 26— 22 235 



