x 
1907-8.] THE GEOLOGY OF THE LAKE WENDIGOKAN REGION. 361 
was spent in examining them because our work in the region was chiefly 
that of examining the iron ranges. 
The most interesting glacial features observed in the region are the 
sand plains formed by the glacial lakes. These plains are well developed 
near Lake Nipigon, and can be seen all along the Sturgeon River beyond 
the high banks of sand. Around the foot of the long rapids on this river 
there are some ridges of stratified silt which may have developed by the 
cutting away of portions of the plain by erosion, thus leaving these ridges 
as remnants, but I think, after as careful an examination as could be made, 
since the sands were thickly covered with vegetation, that these ridges 
represent sand bars which were formed by the waves and shore currents 
of the glacial lake across the opening of its bay which stretched inland a 
short distance to the northeast, and a long way up the channel now occu- 
pied by the Sturgeon River. In this same region and a little farther 
south along the river there is some well stratified silt, coarse, and very 
coarse sand quite typical of the beach or shallow water deposits of a lake. 
On the portage between the Sturgeon River and Lake Corrigan, the sand 
plains reach an elevation of about 125 feet above the foot of the long rapid 
and 1,035 feet above sea-level. These plains are found farther east beyond 
‘the highest part of the diabase outcrop and may be seen around Lake 
Wendigokan at between -10 and 30 feet above the lake, while around 
Clear Lake they are mostly not more than -10 or 15 feet above that lake 
and about 1,040 feet above sea-level. There seems to be some difference 
of opinion among geologists as to which of the glacial lakes formed these 
sand plains. At least some of the Canadian geologists* hold the opinion 
that Lake Warren was responsible for them, while the Americansf do not 
consider that Lake Warren ever covered that part of the country but that 
the lakes which extended over Lake Superior and the surrounding region 
were Lakes Algonquin and the great Nipissing Lakes, the former being 
more extensive than the latter and extending as far north as Lake Nipigon. 
These sand deposits represent the shallow water formations of one 
of these great glacial lakes, and although during the summer of 1907 we 
found sand plains with greater elevation than those extending to the east 
as far as Battle Island Lake, on the Sturgeon River, at the time these plains 
around Wendigokan were studied, they proved that a great bay of the 
glacial lake extended up the present channel of the Sturgeon River and 
farther inland from Lake Superior than in any region then explored. 
* Coleman, Bureau of Mines, 1907, p. 135. 
+ Chamberlin & Salisbury, Geology III, Earth History, pp. 399-400. 
Goldthwait, Bull. XVII, Wis. Geological Survey, 1907. 
