242 J. E. SPUKR — ORIGIN AND STRUCTURE OF THE BASIN RANGES 



effects. The faults of the Colorado plateau, which have usually formed 

 simple fault-scarps, belong to a recent epoch, and are contemporaneous 

 with recent faults in the Great Basin region. The two provinces, how- 

 ever, differ ver}' widely as to the relation of topography to deformation 

 in each : first, because in the Basin region the influence of ancient de- 

 formation and erosion in mountain-making has been immense, while 

 in the plateau this factor hardly exists, and, second, because the recent 

 faults, which form the striking and almost solitary structural feature 

 in the plateau, are, so far as yet studied, far less abundant and power- 

 ful in the Great basin. 



History of Deformation in the Great Basin Province 

 late cambrian movement* 



In many localities of extreme eastern Nevada and adjacent Oregon 

 and Utah where examination has been made a striking difference in the 

 geologic section, as compared with that ftirther w'est, has been observed. 

 This difference lies in the absence or slight representation of the Silurian 

 and Devonian. The upi:)er horizons of the Cambrian and the lower ones 

 of the Carboniferous are also often missing, so that the Coal Measures 

 may rest on the Lower Cambrian. f 



The general lack or scantiness of deposits representing such important 

 ])eriods, joined to the irregularity in neighboring districts as to the 

 amount of missing strata, indicate that during a large part of the De- 

 vonian and Silurian tbis was an area of non deposition, and that intliis 

 same period the Cambrian, and i)erhaps the Archean,3: was deeply eroded. 



This region is limited in Nevada (except in the northeastern part) by 

 the meridian 114 degrees 80 minutes, west of which are many thousand 

 feet of Silurian and Devonian,§ so the western district was at the bottom 

 of a deep ocean at the period when tbe region farther east was a land 

 mass. The limits of the continent whose existence is thus demonstrated 

 are not yet known, but it was probably of considerable size. The uplift 



*At present tJie obscurity of the record is such that it is ii.irdly profitable to discuss disturbances 

 of earlier (hite than this. 



fS. F. Emmons : (ieoiogical Explorations of the Fortieth Parallel, vol. ii, p. 3C8, 444; fjcomonic 

 Geology of the Mercur Mining District, Utah, Sixteenth Ann. Rept. U. S. Geol. Survey, part ii, p. 3G0 

 (map and cross-section). 



C. D. Walcott: Bull. 30, U. S. Geol. Survey, p. 38. 



E. E. Howell : U. S. Geol. Surveys West of the Hundredth Meridian, vol. iii, pp. 238, 242. 



G. W. Tower and G. O. Smith : Nineteenth Ann. Kept. U. S. Geol. Survey, part iii, p. 028. 



C. E. Dutton : Monograph ii, U. S. Geol. Survey Atlas, sheets ii, xi, xiii, xiv, xxii. 



C. D. Walpott: Am. Jour. Sci., vol. xxvi, p. 437. 



X Arnold Hague : Geological Explorations of the Fortieth Parallel, vol. ii, p. 421. 



Clarence King: Same work, vol. i, p. 139. 



I Arnold Hague : Monograph xx, U. S. Geol. Survey, p. 13. 



