INTRODUCTION 219 



The inoiiocliiial rid^e of erosion 257 



Tlie anticlinal ritljze of tlefurniation 257 



Relative ascendency of fanltin<j: and erosion 257 



rrincii)al ascertained fanlts of (ireat basin 257 



General relations of faults to topography 25H 



Relation of faults to Great Basin topography 259 



History of the development of the fault theory as ai)plied to the Basin ranges. 200 



Analysis of the fault hypothesis 2()4 



iSuniinary . . 265 



Explanation of plates 207 



Introduction 



Investigation of the structure of the desert ranges which lie between 

 the Wasatch and the Sierra and extend southward into California is no 

 easy task. In the past difTerent views have been held, some seeing in 

 them a series of parallel folds in which the anticlines protruding above 

 the surface formed the ranges, while others considered them a series of 

 unfolded blocks, broken by parallel faults, and upheaved along these 

 faults so as to form ridges. Besides these entirely opposed theories a 

 compromise view has been entertained, namely, that the ranges were 

 first folded and subsequently broken into blocks by faults and upheaved 

 into mountains. Even in this compromise there has been great diversity 

 of opinion as to the relative importance of the two chief agents in 

 mountain-building. King,* for example, considered that folding has 

 been most potent, while Russell f believed that the ranges as they now 

 stand are entirely due to faulting and that the faulted blocks have been 

 tilted so that each block is essentially a monoclinal mountain, even 

 when the strata are considerably folded. 



In view of all this, the writer proposes to approach the problem with- 

 out any preconceived theory, to examine the observed facts gathered by 

 himself or by previous investigators, and to deduce from these facts 

 what shall appear to him to be the natural conclusion. 



Examination of the Structure of Individual Ranges 



banqes of northwestern utah 



Tintic range. — This range has been carefully studied by Messrs Tower 

 and Smith. I According to these writers the Tintic mountains were up- 



* Explorations of the Fortieth Parallel, vol. i, Systematic Geology, p. 735. 

 t Monograph xi, U. S. Geol. Survey, p. 26. 



X Geology and mining industry of the Tintic district, Nineteenth Ann. Kept. U. S. Geol. Survey, 

 part iii. 



