[MACKENZIE] HISTORICAL AND STRUCTURAL GEOLOGY 



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tory to the east. This hypothesis is considered in some detail, and 

 the reasons for dissenting from it are given. An hypothesis based on 

 a single episode of compression is presented, which considers the 

 Lewis overthrust and the steep reverse faults of the Mesozoic rocks 

 of the foothills to have developed in connection with "soles" of the 

 Scottish type. Relaxation following this single episode of compression 

 completed the present structures of the mountains. 



Historical Geology 



The earliest events in the history of this part of the Rocky 

 mountains are recorded in a great mass of sediments divided by Daly 

 into the Lewis and the Galton series (I2,a) which Schofield has stated 

 to be wholly of Precambrian age (36). These rocks are of various 

 characteristics, and the section of the Lewis series given by Daly 

 (12, b) will serve to give an idea of their composition. 



Diverse opinions are held as to the origin of this series by those 

 who have worked on it. The Kintla, Grinnell, and probably the 

 Appekunny are certainly of continental origin as shown by their 

 unmistakable characteristics. The dolomites are stated by Daly 

 (12,c) to be chemical precipitates in marine basins, while Walcott 

 suggests that they are of epicontinental origin and precipitated in 

 fresh water through the agency of algae (43, a). Whatever its origin 

 this Precambrian sedimentary series forms a unit, though opinions 

 differ as to how distinct it is from the succeeding Palaeozoic series. 

 Thus Walcott considered them to be sepa ated by a lengthy period 

 of uplift and erosion (43,b), while Daly states the view that these 

 two series form "a simple Palœozoic-Beltian géosynclinal prism, which 



