THE UPPER DIVISION OF THE KEWEENAW SERIES. 153 
waters of Lake Superior, whose basin has been in some measure carved in 
them, but they form the outer part of Keweenaw Point, attaining, in the 
neighborhood of Portage Lake, a considerable surface width. Westward 
from Portage Lake they underlie the flat land north of the Trap Range, 
sloping at a low angle lakeward, and are well exposed at a number of points 
along the shore to the Poreupine Mountains. The Porcupine Mountain 
fold throws them well out into the lake, but farther west they form a belt 
along the edge of the land, and, since they are here standing at high angles, 
a large thickness is embraced in this narrow belt. On the Montreal the 
angle reaches ninety degrees, and nearly the whole thickness of the Upper 
Division is crossed by the lower reaches of the river. Here the Upper Divi- 
sion consists of some 12,000 feet of red sandstone and shale, about 500 feet 
of black shale alternating with hard, gray, nearly quartzless sandstone, both 
shale and sandstone being composed largely of basic detrital material, and 
about 1,200 feet of very coarse bowlder-conglomerate. The same succes- 
sion seems to hold all the way to where, on Keweenaw Point, the base of 
the Upper Division runs out-into the lake—the only difference being that 
the basal conglomerate at times passes into a sandstone. 
Westward from the Montreal River, also, the same succession seems to 
hold, the conglomerate and shale at the base, however, thinning out. The 
last seen of these northward-dipping sandstones and shales, which have 
thus been traced all the way from Keweenaw Point, is on the Brunschweiler 
River, in the western part of Ashland County, Wisconsin. West of this 
they have not been observed, the country which would be occupied by 
them being everywhere drift-covered. The underlying diabases, however, 
appear all across Wisconsin with a flattened dip, while on the upper Saint 
Croix River there is a large development of sandstones dipping southward, 
which are evidently the same that we have been following, forming now the 
other side of the great synclinal which here crosses the whole northern part 
of Wisconsin. The same southward-dipping sandstones are to be seen in 
the northern part of Ashland County. 
The Apostle Islands and the adjoining coast of Wisconsin are under- 
lain by horizontal sandstones. These are to be regarded as an overlying, 
unconformable formation belonging with the horizontal sandstones of the 
