226 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
of the old Chippewa location, 5. W. 4, Sec. 22 of the same township, evi- 
dently belongs with the main mass underlying the porphyry. 
When the Montreal is reached, instead of finding one broad conglom- 
erate between the outer or Carp Lake trap, and the belt next the por- 
phyry, we meet with a succession of alternations of sandstone or red shale 
and diabase. It has already been indicated that even in the Porcupine 
Mountains the inner conglomerate may hold an interstratified diabase band, 
and a few miles west of the Presqu’ Isle there certainly is one. Further 
west the sandstone and beds of basic crystalline rocks must dovetail into 
one another in some such manner as indicated on the map of Plate XXII. 
Exposures belonging to these trap bands are met with on the west line of 
the N. W. 4 of Sec. 34, T. 49, R. 47 W.; on the west line of the S. W. 4 of 
Sec. 31 of the same township; and on the south line of See. 34 of T. 49, R. 
48 W. Further back from the lake shore there are other exposures belong- 
ing to the Main Trap Range, as far south as and nearly in contact with the 
underlying iron-bearing slates. 
The section displayed on the Montreal River is next to be described. 
Ascending the Montreal River from the mouth, vertically placed ledges of 
red sandstone and red sandy shale belonging to the main body of the Upper 
Division, are the only rocks seen up to the 8. E. 4 of the N. E. 4 of See. 20, 
T. 47, R. 1. E. (Wisconsin), two and a half miles above the mouth. Here 
begin exposures of the black shale and its interstratified sandstones. The 
shale of these alternations is dark-purple to black, very soft and clayey, 
and quite regularly laminated. The shale layers run from ten to fifty feet 
or more in thickness, and are quite subordinate in abundance and thickness 
to the associated sandstones into which they grade. The sandstone is dark- 
gray to brown, very close-grained and compact, and often appears macro- 
scopically like a fine-grained, crystalline rock. This rock forms massive 
ledges in the bed and on the sides of the stream Under the microscope it 
appears much the same as the sandstones at the same horizon in the Poreu- 
pine and Ontonagon regions, but some sections show an unusually small 
amount of porphyry detritus, being almost wholly made up of basic frag- 
ments, with the calcite cement. 
