334 W. H. C. SMITH — A.RCHEAN ROCKS WEST OF LAKE SUPERIOR. 



Pmk< 



A folded Syncline 345 



Its Thickness 345 



Its Relation to the Laurentian and Keen at in 345 



Etl'eet n | ion it of orographic Movement 345 



Older than 1 he Ani mi kie 345 



Its Unconformability not always observable 346 



The Unconformity a .Measure of geologic Time 346 



Its Relation to the Atie < >ban Series 346 



Economic Geology of the Airhean 1)47 



Present Knowledge superficial 347 



Iron Ores 348 



Gold 3 18 



Nickeliferous Diorite • .'54 s 



The Nomenclature Adopted. 



In this paper I shall adopt the nomenclature employed for many years 

 in the publications of the Canadian Geological Survey without at present 

 making any attempt to justify it. The term ''Archean." then, will be 

 used, not in the restricted sense advocated by Geikie* nor in that held 

 by Van Hise,f but in its broadest application, as embracing all the rocks 

 stratigraphically inferior to the Animikie rocks of Lake Superior. 



The Region Studied. 



Its Boundaries. — The portion of the Dominion of Canada to which at- 

 tention is here drawn may be briefly described as the southern half of 

 Rainy River district, in the province of Ontario, lying between our trans- 

 continental highway and the international boundary, and the Lake of 

 Woods, in the west, to the western boundary of Thunder Bay district. 



Geologically complex. — It would lie difficult to imagine a more interest- 

 ing field or one that offers such facilities for geologic investigation, yet 

 from the complexity of the structure of the rocks ; from their antiquity ; 

 the tremendous movements they have suffered, as well as the changes 

 they have undergone, and from the absence of all fossil remains, there is 

 perhaps no part of the country about which so many difficulties cluster 

 or in which lie so many pitfalls for the feet of the unwary, the hasty, or 

 the dogmatic geologist. 



Its topographic character. — Physically, the country presents a vast 

 network of lakes which with their connecting streams, afford a ready 



* Anniversary address before the Geol. Soc. of London on the volcanic rocks of England by 

 Archibald Geikie, V. R. S., February, L891. 

 •f-Arn. Jour. Sci., vol. xii, p. 1 17. 



