248 J. E. SPURK ORIGIN AND STRUCTURE OF THE BASIN RANGES 



perienced a differential epeirogenic movement, measuring as much as 

 350 feet vertically. 



On the hypothetical old fault-faces on the western side of the Wasatch 

 and the eastern one of the Sierra Mr King* thought to have found evi- 

 dence of renewed post-Pliocene movements of 1,000 and 2,000 feet re- 

 spectively. Mr Diller has described several Pleistocene faults in the 

 Sierra Nevada, especially along the eastern front, near Honey lake, where 

 the vertical displacement was about 3,000 feet.f 



In 1872 a violent earthquake in Owens valley, California, signalized a 

 movement which resulted, along the eastern foot of the Sierra, in fault- 

 scarps with a maximum height of 20 feet.J 



In the Colorado plateau are a number of heavy north-and-south faults,^ 

 whose extreme youth is shown by their displacing the probably Ple- 

 istocene basalts and by their having remained unaltered to any great 

 extent by erosion. 



CONCLUSION 



While uplift and subsidence, involving the making of continents, and 

 possibly of mountain ranges, went on in Paleozoic times, the earliest 

 post-Archean mountain-making folding of which we have reliable record 

 occurred in the Great basin at the close of the Jurassic, when many of 

 the Great Basin ranges were probably formed, contemporaneously with 

 the Sierra Nevada. Subsequently, mountain-making movements took 

 place in at least part of the Great basin at the close of the Cretaceous 

 and at several ei)ochs during the Tertiar3\ In fact we may believe that 

 folding and faulting has gone on steadil}^ though spasmodically, froni 

 the close of the Mesozoic until the present day, affecting the whole of 

 the Great basin and extending from its borders to the country south and 

 east. The Colorado plateau has been influenced most by the most re- 

 cent of these movements. Major Powell's || diagrams of the faults in this 

 region show that the monoclinal fold is typically the precursor of the 

 fault, as is so frequently the case elsewhere. Since the fold is mani- 

 festly due to compression, the fault must be also. This is in opposition 

 to the views of Professor Russell,1I who reasoned that a highly faulted 

 district, such tis he conceived the Great basin to be, has experienced ex- 

 tension and not compression. 



In general the period of deformation which lasted from the Mesozoic 



* Explorations of the Fortieth Parallel, vol. i, p. 758. 



t Eighth Ann. Rept. U. S. Geol. Survey, part i, pp. 429, 432 ; Fourteenth Ann. Rept. U. S. Geol. 

 Survey, part ii, p. 4:i2. 

 X G. K. Gilbert : Monograph i, U. S. (ieol. Survey, p. 3G1. 



§ C. E. Dutton : Second Ann. Rept. U. S. Geol. Survey, p. 118 ; also Monograph ii, p. 117. 

 II Explorations of the Colorado River, Washington, 1875, pp. 183, 184, lyo, I'jl, etc. 

 H Fourth Ann. Rept. U. S. Geol. Survey, p. 453. 



