348 TRANSACTIONS OF THE CANADIAN INSTITUTE. (VoL. VIII. 
schists and slates which occur with the iron formation, and the only defi- 
nite life history to be recorded is that of the recent plants and animals, 
which are similar to those in many other regions and need not be dis- 
cussed in detail here. 
Some recent structures of interest were observed in the diabase at. 
the foot of the long rapids on the Sturgeon River. ‘These were three pot- 
holes from 12 to 18 inches in depth and about six inches in average diameter. 
In each hole a rounded stone and some gravel were found and these had 
been used by the water as tools with which, in its circular motion, it 
ground out the cavities. One of these holes bore a striking resemblance 
to a large iron mortar and pestle used in a laboratory for pulverizing 
rock. In one of them the rounded stone had become so tightly wedged 
that it could not be moved, and the growth of the hole was, therefore, 
terminated. 
CLASSIFICATION OF THE ROCKS. 
From what has been said in the preceding section the rocks can be 
tabulated in ascending order thus:— 
Pleistocene:—Drift and lacustrine sands. 
Keweenawan?:—Basic eruptive. 
ts fetes if Arkose 
wer Huronian: 
| Conglomerate. 
Rocks of the iron formation. 
Carbonate schists. 
Green schists, greenstones and banded arkose 
and slate. 
Keewatin: 
On the accompanying map the greenstones, green schists and banded 
arkose and slate are mapped together because of the impossibility of 
separating them. As the individual formations can best be considered 
separately they will be taken up in ascending order and where necessary 
some further notes on my reasons for placing them in their respective 
positions will be given. 
GREENSTONES 
These rocks may be readily correlated with the ancient greenstones 
so frequently mentioned in the geological reports of the Cobalt, Eastern 
_ Ontario and Michipicoten regions and they lie at the bottom of the rock 
series around Lake Wendigokan. ‘They consist of porphyries with large 
crystals of plagioclase or hornblende, of amygdaloids containing amygdules, 
generally of quartz or calcite and ancient quartz-diorites. A specimen 
. 
bee, 
; - 
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