THE 



CANADIAN NATURALIST 



SECOND SERIES. 



ON THE GEOLOGICAL FORMATIONS OF LAKE 

 SUPERIOR* 



By Thomas Macfarlane. 



III. Upper Copper-bearing Series. 



The name of the Upper Copper-bearing Rocks of Lake Superior 

 was given to this series by Sir W. E. Logan, to distinguish it from 

 the Huronian or Lower Copper-bearing Rocks. The geographical 

 and geological position, lower altitude, regular .bedding, and pecu- 

 liar lithological character of these Upper Rocks cause them to be 

 easily recognised and readily distinguished from the Huronian. 

 They have been separated into an upper and lower group, the 

 latter of which seems, however, to be confined to the north-west 

 parts of the lake. Along its eastern shore, between Sault St. 

 Marie and Michipicoten, there are frequently found, betwixt the 

 water and the high Huronian or Laurentian hills, narrow strips 

 or patches of the rocks of the upper group, which often jut out as 

 small islands into the lake, and doubtless extend out great distances 

 beneath its waters. Such limited strips of these rocks are found, 

 for instance, skirting the base of Gros Cap, along the south shore 

 of Bachewahnung Bay and at Cape Gargantua. But besides 

 these and much more important for the study of the upper group 

 of the Upper Copper-bearing series, there are occasional extensive 

 developments of its rocks, many thousand feet in thickness, such 

 as at Cape Mamainse, Michipicoten Island, and Point Keweenaw 



* Continued from page 201. 

 Vol. III. P ;no. 4. 



