sv. JOHN.|] GEOLOGY SOUTH FLANK GROS VENTRE MOUNTAINS. 211 
eneissic ledges. The Quebec limestones also hereshow typical exposures, 
consisting of usually even, thin-bedded layers of a dark gray and dirty 
yellow color, weathered in rough surfaces, with brecciated and odlitic 
layers, the whole attaining an exposed thickness of 300 to 400 feet, more 
or less. . 
A mile or so to the southeast of the above locality, the quartzite com- 
poses the south-facing mountain wall. Intermingled with the débris in 
the talus slopes are huge blocks of quartzite, containing fucoidal mark- 
ings. Inthe vicinity the Quebec limestones, also, are seen folding overthe 
steep south face of the ridge, and in the summit they are overlaid by a 
heavy bed, 200 to 400 feet in thickness, of heavy-bedded light butt-gray, 
vesicular, rough-weathered magnesian limestone. The latter agrees 
well with what elsewhere has been referred to the Niagara epoch, al- 
though search failed to detect confirmatory paleontological evidence 
going to establish this identity. Indications of the above-mentioned 
synclinal were not again met with in the mountain flank, whose slopes 
are heavily loaded with the sedimentary rock débris fallen from the 
ledges perched along the summit of the ridge, concealing even the morai- 
nal deposits which are detected in many of the high benches outlying 
the mouths of gulehes. Thence to the debouchure of the Hoback 
tributary that drains a considerable area of mountain basin on the north- 
east of Station XII ridge, the south slope of this ridge is heavily plated 
with sedimentary deposits. 
In the angle on the west side of the debouchure of the latter stream, 
the mountain flank facing southward is composed of the drab or gray 
limestone of the Carboniferous, steeply rising into the relatively low crest 
in which they fold over, again descending northeast into the depression 
of the mountain course of this stream. The mountain in the opposite 
angle of the debouchure has the appearance of a huge block of Carbonifer- 
ous strata which has been bodily uplifted and but slightly tilted from 
ihe horizental. The south slope does not distinctly reveal the southerly 
flank of the fold, which was here eroded and concealed beneath the ba- 
sin Tertiary deposits. The Carboniferous deposits inthe present mount- 
ain reveal a thickness of several hundred feet of dark gray limestones 
with distinct reddish tint above—the latter color-feature being quite 
prevalent in these beds in this part of the range. 
The exit of this first considerable Hoback tributary shows a rather 
wide canon-debouchure, bordered on either hand by mountains sculp- 
tured out of the Carboniferous ledges, which appear in escarped slopes 
and picturesquely-weathered pinnacles. These deposits are traced well 
up the canon to the northeast, as far as could be seen, forming the 
heights along the mountainous northeast side of the valley. Below the 
exit, the stream, on entering the softer deposits of the basin Tertiary, 
presently forms a low intervale bordered by well-defined terraces. It 
carries a good volume of swift-flowing water, and its bed is composed 
of water-worn fragments of Archean, quartzite and limestone. 
Although it was not with absolute certainty so determined, yet, both 
from the relatively low elevation and nearly horizontal position of the 
block of Carboniferous strata composing the mountain in the east angle 
of the above-mentioned stream, it may be that this mass belongs to the 
north slope of the great south anticlinal fold. This explanation is sug- 
gested by the position of sedimentary occurrences in the loftier crests to 
the northeast, with which this mountain forms an outlying prominent 
spur. In the latter mountain ridge, which may be more or less parallel 
with that of Station XII, the strata are bent up ina great flexure, of 
which the southeast face is that seen from this point of view. This is 
