GEOLOGICAL POSITION OF THE ANIMIKIR ROCKS. 385 
Thunder Bay—has been placed by Logan' and Bell? at the base of the 
copper-bearing series, the former geologist, in his Geology of Canada, 
speaking of it as the “Lower Group of the Upper Copper-bearing rocks.” 
Macfarlane* and Hunt,‘ on the other hand, regard the Animikie rocks as 
altogether newer than the Keweenawan, which they are believed to 
overlie unconformably. Hunt says that they, together with the overlying 
sandstone of the east side of Thunder Bay, may even be mesozoie for all 
the evidence there is to the contrary... There can be no doubt, however, 
that Logan and Bell are correct in placing the Animikie Group beneath 
the copper-bearing or Keweenawan rocks proper. This seems plainly in- 
dicated by the exposures the east side of Thunder Bay, and thence to 
Black and Nipigon bays, but to any one approaching from the southwest 
along the Minnesota coast becomes so absolutely certain as to admit of no 
question at all. Not only does one in descending the lower part of the 
Minnesota coast constantly cross the Keweenawan beds in descending order 
until the Animikie slates are reached at Grand Portage Bay, but on the 
large island at the mouth of this bay he may see slates underlying Kewee- 
nawan diabases in a continuous cliff exposure. 
So far, then, I agree with Logan and Bell; but from their view that the 
Animikie rocks are but a downward continuation of the Keweenawan I 
must dissent altogether. The erosion which intervened between the two 
formations, as indicated by the already described occurrences on the east 
side of Thunder Bay, and again by those at the east end of the Minnesota 
coast, and the pronounced lithological contrast between the sedimentary 
beds of the two groups, both bear heavily against any such view. Moreover, 
the essential identity between the Animikie rocks and those of the Penokee 
region of Wisconsin, and their close similarity to the South Shore iron- 
bearing schists generally, make it plain to me that we are dealing here with 
the North Shore equivalents of the South Shore iron-bearing formation. 
We have in the Animikie series, as in the South Shore Huronian, sili- 
ceous schists, quartzites, dolomites, chert beds, and magnetite-bearing quartz- 
1Geology of Canada, 1%63. 
? Report of the Geological Survey of Canada for 1866~’69, p. 318. 
3 Canadian Naturalist, New Series, III, 252, LV, 38. 
42d Geol. Surv. Pennsylvania, Azoic Rocks, Part I, p. 240. 
eo On. 1ctt., p. 241. 
25 LS 
