THE WESTERN SANDSTONE. 365 
ory supposes that between these horizons there exists a thickness of seven 
miles of rock, of which two are of purely sedimentary material. 
It seems to me that the south face of the Keweenaw Range is both 
a fault cliff and a shore cliff, against which the newer Eastern Sandstone was 
laid down, but not until after a large erosion ; and that faulting took place 
again after or else continued until after the deposition of the sandstone. The 
original faulting seems to be demanded on this line by the general structural 
relations of the Keweenaw and South ranges, as shown on a previous 
page, and by the absence of outliers of the immense thickness of rocks of 
the Keweenaw Range to the southward. That the Eastern Sandstone was 
deposited subsequently to this first faulting is evidenced by its containing 
conglomerate layers in which the pebbles are frequently of Keweenawan 
eruptives, basic as well as acid (Béte Grise Bay), and by the way in which 
it cuts across the course of the South Range beds. That faulting motion 
took place along the fault line after or during the deposition of the Eastern 
Sandstone, is indicated by the way in which the sandstone dips southward 
along the junction at the south side of the Keweenaw Range. 
THE WESTERN SANDSTONE. 
The Apostle Islands and the adjoining coast of Bayfield County, Wis- 
consin, are composed of a horizontally placed sandstone, closely resembling 
in character the Eastern Sandstone of Keweenaw Point. I have described this 
sandstone somewhat fully in another place’ From the head of Chaquamegon 
Bay eastward there are no rock exposures on the coast until Clinton Point 
is reached, four miles above the mouth of Montreal River. Here are flat 
ledges of sandstone of some size at the water level. I take them to mark 
the easternmost point of the Western Sandstone, though this cannot, from 
their position only, be regarded as certain. At the mouth of the Montreal 
occurs the vertically placed sandstone of the Upper Division of the Ke- 
weenaw Series, with an immense thickness, as already described. West- 
ward from the Apostle Islands this sandstone has been traced to the 
head of the Jake, and in Douglas County, Wisconsin, may be seen at a 
number of points in direct contact with the south-dipping Keweenawan 
diabases. In all of this region this sandstone preserves its predominatingly 
1Geology of Wisconsin, Vol. III, p. 207. 
