DEFORMATION IN THE PACIFIC BORDER REGION. 47 



erous and Cretaceous formations (the Laramie included) make the chief 

 part. Both are regions of great mountain-making displacements of post- 

 Cretaceous occurrence. Both are the courses of high and bold mountains 

 dependent for their origin on these displacements. 



But there is a contrast in the extent and results of the displacements. 

 South of the Archaean bend, the mountain-system is in part that well called 

 the Plateau system by Major Powell ; north of the bend, in British 

 America, it is the Appalachian system, according to the results of the geolo- 

 gists of the Canadian survey, Dr. G. M. Dawson, and more definitely Mr. 

 R. G. McConnell. Mr. McConnell, in his report of 1886 on the region 

 about the pass through " the Rocky Mountains " of the Canadian Pacific 

 Railway, describes and figures ordinary and overthrust flexures, and 

 upthrust faults of 1,000 to 15,000 feet, precisely, says Mr. McConnell, like 

 those " in the Appalachian region of East Tennessee, described by Prof. Saf- 

 ford " ; and in one section, which he figures, there is a vertical displacement 

 of 15,000 feet, and also a shoving of Carboniferous limestone almost horizon- 

 tally over Cretaceous beds to the eastward for " a distance of nearly two 

 miles." From the observations, the whole amount of horizontal displace- 

 ment in this fault was estimated by Mr. McConnell to be seven miles. The 

 resemblance to the Appalachian system includes the fact that the upthrusts 

 and overthrusts were, in each observed case, landward in direction. Dr. 

 Dawson's facts from the region south, nearer the 49th parellel, published also 

 in the Canadian Geological Report for 1886, are similar as to the character 

 of the flexures and faults except that some of the faults appear to be up- 

 thrusts westward. Mr. J. B. Tyrrell has obtained supplementary facts from 

 northern Alberta. Further, the report of Mr. O. H. St. John, in the Hayden 

 volume for 1877, contains a plate of sections across the Wyoming mountains 

 in western Wyoming, south of the Archaean bend, representing flexures 

 and faults like those described by Mr. McConnell. 



I have not, myself, studied the region with reference to the transitions ; 

 but in view of the facts that the mountain-making to the north and south 

 involved the same rocks to the top of the Laramie, and that these rocks were 

 involved, therefore, in the same great subsidence attending the thickening of 

 the accumulation of the Mesozoic beds as well as those beneath, I think we 

 can hardly doubt that all is one in general system, orographically not less 

 than stratigraphically, although successive portions of the summit belt may 

 have had a degree of independence in the movements. 



We learn from the facts, as we have also from those of Lower Silurian 

 history, that an Archaean protaxis is not necessarily a fast boundary with 

 regard to geological work. The Cretaceous seas spread among the Archaean 

 heights, and in the region south of Montana for a long distance beyond them, 



