408 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
of the Nipigon Lake region as described by Bell, precisely the same reason 
might be advanced for their absence in the region of folded Huronian schists 
north of Lake Superior. 
The Keweenawan rocks, or Nipigon Series, as they are termed by him, 
are represented by Bell as lying in the Nipigon Lake basin, directly athwart 
the course of several belts of folded schists, and with a general horizontal 
attitude. These schists Bell regards as Huronian, and maps them as 
directly continuous with the schistose belts of the country immediately 
north of Thunder Bay. (See Fig. 34.) If these rocks are indeed Huro- 
i Ey 
nian, and their relation to the 
Keweenawan is as stated by 
Bell, no doubt can remain as to 
the existente of a genuine un- 
conformity between the two sys- 
tems.  LBell’s detailed descrip- 
tions, however, do not fully bear 
out his reference of the schistose 
rocks in question to the Huro- 
nian, nor his general statement 
as to the horizontal attitude of 
the Keweenawan rocks them- 
selves. 
In conclusion, then, it is to 
Keweenawan rocks are linked 
together by the lithological affin- 
ii il be said that the Huronian and 
TL — ities of their basic eruptive mem- 
bers, and by the close approach 
Fic. 35.—Outline geological map of the Nipigon Lake ° 
Region, after a manuscript map by R. Bell. to conformity between them 
which obtains throughout the whole western half of the Lake Superior basin; 
and that they are separated from one another by the lithological contrast 
between their sedimentary members; by an intervening erosion, which has 
plainly taken place, even where there is a close approach to conformity; 
