BAST AND WEST CONTINUATIONS OF THE PORCUPINE BELTS, 225 
paratively small thickness which they are observed to possess east of the 
Ontonagon. In T.50, R. 40 W., the exposures indicate the continuance of 
the same conditions. The shale shows in the N. W. 4 of the S. W. 4 of See. 
18, again in the the N. W. 4 of the N. E. 4 of Sec. 15, and again near the 
south quarter-post of section 11. These exposures, with those already noted 
on the other side of the Ontonagon, in See. 7, T. 50, R. 39 W., serve to fix 
the course of the shale belt across this township at a little north of east for 
the first two miles, then about N. 15° E. for two and a half miles, and then 
N.30° E. to the Ontonagon River. ‘Red slaty trap and conglomerate” are 
marked on the township plat as occurring within a mile of the shale, and the 
succession is evidently the same as already noted to the east of the Ontona- 
gon, viz: black shale, sandstone and conglomerate, traps, conglomerate, 
traps, porphyry. North of the black shale the main body of sandstone is 
everywhere the surface rock to the lake shore. 
Westward from the Porcupine Mountains the upper belts are more 
easily traced. Following the coast line westward from the mouth of the 
Presqw’ Isle, the main sandstone of the Upper Division forms the coast as 
far as the west line of T. 49, R. 46 W., just beyond which the black shale, 
which may also be seen a short distance up Black River from the mouth, 
appears at the coast for a short time, soon retreating from it again. From 
this point the main body of sandstone forms the coast continuously to the 
Montreal River. In this distance the layers trend more to the south than 
the coast line, which thus is constantly reaching a higher horizon. At the 
same time the dip angle rapidly steepens, being 45° about midway in range 
47, and néarly 90° at the mouth of the Montreal River. It thus results 
that on the Montreal as much as 10,000 feet of the main sandstone is crossed 
by the lower reaches of the river, for some ten miles to the east of which stream 
it often forms bold cliffs forty to seventy feet high. On Black River there 
are falls in the N. W. 4 of Sec. 15, T. 49, R. 46 W., over conglomerate and 
sandstone, which belong with the broad conglomerate beneath the shale. 
The conglomerate at the falls near the S. W. 4 of the 8. W. 4 of the same 
section belongs with the Carp Lake band, and the “trap” at the falls just 
above in the N. E. } of Sec. 21 with the underlying diabases of the band fol- 
lowing just above the porphyry of the Porcupine region. The “ trap-rock” 
15L8s 
