150 The American Geologist. September, 1895 
[Cructal points in the geology of the Lake Superior region. No. 7.] 
A RATIONAL VIEW OF THE KEWEENAWAN. 
By N. H. WiNCHELL, Minneapoli.'f, Minn. 
The following further difficulties stand in the way of the 
Wisconsin idea of the separateness of the horizontal Lake Su- 
perior sandstones from the tilted. 
1. There is no permanent petrographic distinction between 
them. The red shales and red sandstones, which are said to 
prevail in the tilted beds, are found in great volume in the lower 
portion of the horizontal beds. This may be seen in consult- 
ing the sections of the horizontal beds recorded by the Minne- 
sota survey,* and by the descriptions of Mr. Sweet in volume 
III of the Wisconsin report, as well as by those of the eastern 
sandstone for many miles east of Keweenaw point by C. Rom- 
inger. 
2. The tilted beds are sometimes horizontal or nearly so, 
and the horizontal beds are sometimes tilted at high angles. f 
3. The top of the Keweenawan sandstones has never been ob- 
served. 
4. The bottom of the overlying sandstones has never been 
observed except where by regional subsidence it is non-con- 
formable upon the tilted traps or the older crystallines. 
5. In various places the horizontal sandstones, and even 
some of the higher associated magnesian limestones, have been 
seen non-conformable on the traps of the lower portion of the 
Keweenawan, indicating a progressive submergence after the 
tilting of the traps. 
6. The non-conformable contact which is assumed to have 
taken place between the base of the horizontal sandstones and 
the Keweenawan tilted sandstones has never been observed. 
7. The whole region in which this question centers is one of 
disturbance and eruptive action. Ever since some of the hor- 
izontal sandstones were deposited there have been such move- 
*N. H. WiNCHELL, Tenth Minnesota report, pp. 30-34, 1881. 
tSwEET, Trans. Wis. Acad. Sci., vol. iii, p. 46. Irving, in Am. Jour. 
Sci., (3), vol. VIII, July, 1874, p. 50, describes briefly horizontal red sand- 
stones and shale on Silver creek, but in Copper Bearing Rocks of Lake 
Superior, Mon. V, U. S. Geol. Survey, he includes these in his upper 
member of the Keweenawan. See plate xxii. See also p. 411, where 
Irving speaks of the " comparative flatness of the northward dip." 
Brooks, Geol. Sur. of Mich., vol. i, p. 185, 1873. 
At nearly all the points where the horizontal sandstone lies non-con- 
formably upon the traps it is locally highly tilted away from the traps. 
