262 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
Section I—THE MINNESOTA COAST. 
In the following account of the geology of that portion of Minnesota 
bordering Lake Superior, I have not availed myself of any previous work, 
save where the fact is especially mentioned. Except in these few instances, 
the statements made are based exclusively on my own observations for the 
coast line from the Dalles of the Saint Louis River to Thunder Bay, and, 
so far as locations, trends, and dip are concerned, upon those of my 
assistants, Messrs. Chauvenet, Campbell, and McKinlay, for the back 
country along the Cloquet, Lester, French, Split Rock, Beaver, Baptism, 
Cascade, Devil’s Track, and Brulé rivers. The rock specimens collected 
by these gentlemen I have studied myself. 
Along this coast the rocks dip almost constantly lakeward, either trend- 
ing with the general direction of the coast line or cutting it at a small angle. 
The only exception to this is the group of beds in the angle of the lake at 
Duluth, where the strike is at first even slightly west of north, but rapidly 
changes to north and east of north within a distance of three miles along the 
coast, which here trends N. 50° EK. Except in the same place, where the 
dips reach 45° eastward, lessening to 15° or 20° within the same distance, 
the lakeward dips are at a low angle. The same flat lakeward dips prevail 
for miles back of the coast line. 
The actual western termination of Lake Superior is near the village of 
Fond du Lace, Sec. 8, T. 48, R. 15 W. In this vicinity, on both sides of the 
Saint Louis River, are sandstones trending from north to north-northeast, 
with an eastward slant of 5° to 10°. Following the Saint Louis upwards 
these sandstones are found overlying slates of the Animikie Group (Huro- 
nian), on the southeast quarter of Sec. 11, T. 48, R. 6 W., three miles due 
west of the sandstone at Fond du Lac. The slates continue for many miles 
up the Saint Louis. Both slate and sandstone are described on a subse- 
quent page. The same slates and sandstones appear on Mission Creek, 
north of Fond du Lac, beyond which to the northeast is a gap of three miles 
without exposures. Then begins a long series of bold rocky hills which 
continue along the north side of the Saint Louis to Duluth. These are 
composed of gabbro, associated with which is much of two kinds of red 
