432 THE VERMILION IRON-BEARING DISTRICT. 



Archean jasper are surrounded by valleys in the softer rocks of Lower 

 Huronian age. The numerous anticlinal hills of Archean greenstone 

 between Moose Lake and the Kawishiwi River, in Ts. 63 and 64 N., R. 9 W., 

 and those between Knife Lake and Grobbemichigamma Lake, in Ts. 64 

 and 65 N., Rs. 6 and 7 W., show similar relationships, being surrounded 

 by sedimentaries of Lower Huronian age. Somewhat less characteristic 

 are the numerous small anticlines shown on the islands of Vermilion Lake 

 and the adjacent shores, with Ely Island, the point south of Mud Creek 

 Bay, and the point east of Stuntz Bay as the most striking cases. Just 

 across the international boundary in Ontario there is an area reconnoitered 

 by the United States geologists where a great Archean anticline is found 

 separating the Lower Huronian Knife Lake slates from the Archean iron- 

 bearing Soudan formation in Emerald and Big Rock lakes, and another 

 Archean anticline separates the iron formation of these last two lakes from 

 the Lower Huronian syncline in That Mans, This Mans, the Other Mans, 

 and Agawa lakes. These four narrow, aligned lakes are the most striking 

 cases of synclinal lakes found in this region. 



The shapes of the lakes depend also to. a very great extent upon the 

 structural features of the rocks surrounding the lakes. They lie, as has 

 already been intimated, in structural basins which are occupied by the 

 younger rocks. Examining the large lakes in detail one finds that the 

 prominent salients are formed by the anticlines of older rocks, while the 

 reentrants are sj^nclines occupied by the younger ones. This condition is 

 very noticeable on the east end of Vermilion Lake. Beginning at the south 

 with Stuntz Bay we find the east side of this bay, which continues to the 

 east in a marked depression, is in a syncline of Lower Huronian sediments 

 with an anticline of Archean greenstone and jasper forming Soudan Hill to 

 the south, and a corresponding anticline of Archean jasper to the north, 

 which forms a salient. The western side of the bay shows clearly the 

 relation between the differential erosion of rocks of the same series. It lies 

 in a syncline of Lower Huronian slates with the underlying conglomerate 

 of the same series forming the north arm, and Archean jasper with occa- 

 sional patches of unremoved Lower Huronian conglomerate forming the 

 south arm. Armstrong Creek and Bay is another case of a syncline occu- 

 pied by the Lower Huronian slates with Lower Huronian conglomerates on 

 both flanks, and forming ridges Still farther south and north of the con- 



