
Bi i ole 
Pe P , oe 3. “= aie in ee , 
‘ 2 eee 
68 B. N. A. BOUNDARY COMMISSION. ~ = 
as “ah ae ; 
E. Amygdaloidal trap; dark coloured and hard. 50 to 100 feet. = ee) 
D. Compact bluish limestone, somewhat magnesian, and weathering» Bhs 
brownish. This forms some of the boldest crags and peaks of the Fi 
mountains, and apparently rests unconformably on Series nies par 
1,000 feet. PANG Se 
C. Sandstones, quartzites and slaty rocks, of various tints, but aiétal 
reddish and greenish-grey ; the individual beds seldom of great — 
thickness, and the colour and texture of approximate beds rapidly _ 
alternating. In this series occurs a band of bright-red rocks, of 
inconstant thickness, also two or more zones of coarse mati 
grit. 2,000 feet or more. he 
B. Limestone, pale-grey, cherty and highly magnesian; hard, much- 
altered and weathering white. It includes at least one band of 
coarse magnesian grit like that found in the last series, which 
weathers brown. 200 feet. | 
A. Impure dolomites and fine dolomitic quartzites; dark purplish and 
4 | grey, but weathering bright brown of various shades. 700 feet or 
> more. 
bs . 145. The trap E. is remarkable for its continuity over an extensive 
area without any great variation in thickness or character. It is repre- 
Be ee, sented along the eastern side of the mountains for probably at least 
twenty-five miles, holding always the same position in the series. It 
v occurs also in the Boundary Mountain, and in Mt. Yarvell almost at the 
extreme western margin of the range. In a bold peak standing in the 
angle between the two branches of the pass at the East Fork, what 
appears to be a thin bed of a similar trap occurs among the limestones of 
Series D. It can there be traced for a long distance on the cliffs, but was 
i not elsewhere observed. 
146. No granitic or gneissic rocks were found in this part of the 
mountains; and, as elsewhere shown, they even disappear as constituents 
of the drift before the foot-hills are reached in this latitude. These rocks 
are not known to occur in any part of the eastern range of the mountains 
as the basal rocks of the series, and in Colorado are quite extensively 
exposed, and hold in association with them the ores of the precious 
metals. In some cases these rocks are observed to be clearly overlapped 
i by the Potsdam sandstone; and if not the equivalent of the Laurentian of 
4 
| : north of the forty-ninth parallel. Southward, they appear in some places 
qq the east, are at least Eozoic. 


