380 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
The following is Bell’s stratigraphical scheme for the Animikie Group, 
n1 
or “Lower Group of the Upper Copper Bearing Rocks. 
1. Conglomerates composed of pebbles of quartz, jasper, and greenish slate, in a 
greenish arenaceous matrix. Seen on the north shore of Thunder Bay. Es- 
timated thickness = = sc \eyesjesrcyot ister co oleate ates eee ene eerie 
2. Chert layers, mostly thin and having a ribbon-like appearance in cross-section. 
The mass is generally dark, but some light-colored layers occur. Thin beds 
of dolomite sometimes separate the chert layers from one another, and argil- 
laceous layers are also occasionally interstratified; while bands of dolomite, 
which are themselves sometimes separated by argillaceous beds, are inter- 
stratified with the foregoing. The chert bands contain iron pyrites in specks, 
nodules, and thin interrupted layers. A mineral resembling anthracite also 
occurs in the rocks of this and the following division. Seen at the eastern 
extremity of Thunder Bay, and near the five-mile post on the Red River 
road.- Estimated! thickness: 2-22 2.222) -ce eee eens eee eee aire 
3. Darkly-colored massive argillites and flaggy black shales, the mass being charac- 
terized by numerous vertical joints, running in two directions, and dividing it 
into blocks of a very symmetrical character. The shaly portions hold regu- 
larly formed spheroidal concretions of various sizes. Trap beds are associ- 
ated with these rocks along the north shore of Thunder Bay, at the Thunder 
Bay mine, and in the township of McIntyre. The shales are seen on this part 
of the Kaministiquia River, especially at the Grand Falls, and along the coast 
of Lake Superior, between Fort William and Pigeon River, while an example 
of the massive may be seen in the workings of the Thunder Bay mine. Es- 
timated thickness =... 1252132 teste Heer Doe eee eee eae eee sme 
4, Grey argillaceous sandstones and shales, mostly thinly and evenly bedded, fine- 
grained, and slightly calcareous. Examples of both of these rocks may be 
observed on each side of Thunder Cape, and in the township of McIntyre. In 
the southern part of this township, and at the northwestern corner of Neebing, 
bands of sandstone, supposed to belong to this division, occur, containing a 
large percentage of magnetic iron ore. Estimated thickness.......-.....--. 
This scheme, which is pretty much that of Logan, is obtained 
Feet. 
450 
by 
building up from the exposures near the underlying gneiss in the northeast 
corner of Thunder Bay. But gneiss and granite evidently do not always 
come against the same horizon of the Animikie slates, so that such a scheme 
would be unsatisfactory in any case, even were its truth not distinctly dis- 
proved by the occurrences along Pigeon River and thence west and south, 
where itis plain, from the constant southward dip and broad area occupied, 
that there is a thickness of fully 10,000 feet. Even at the Silver Islet 
1 Geol. Survey of Canada, Rep’t for 186869, p. 318. 
