Gneiss.

Archean
rocks.

Bow River

series.

Castle Moun-

tain lime-
stones.

Order of suc-

cession.

24 ¢ FINLAY AND OMENICA RIVERS.

to the Castle Mountain group, a series which includes beds ranging
from the Middle Cambrian to the Cambro-Silurian.*

Above the limestone outcrops just referred to, exposures are want-
ing for a distance of over two miles and then hard garnetiferous gneiss:
appears in the banks of the valley. The Bow River series: of con-
glomerates, quartzites and argillites which usually separates the Castle
Mountain limestone from the Archean was not observed andi may be:
cut off by a fault.

Archean rocks commence about a mile and a half below the mouth
‘of the Oslinca and are exposed along the river for a distance of twelve
miles. The principal variety consists of a medium graimed biotite
gneiss. Muscovite- and hornblende-gneisses are also present, but are
less abundant. A felspathic augen-gneiss occurs in one section and
garnetiferous gneisses were observed at several horizons. Lustrous
mica-schists and soft hydro-mica schists alternate with the gneisses in
bands and beds, and constitute a considerable proportion of the forma-
tion. The Archean outcrop crossed by the Omenica has the form
of a great anticline, with its eastern limb dipping in a north-easterly
direction at angles ranging from 30° to 70° and the western limb
dipping in a south-westerly direction at correspondingly steep angles,
The strike is 8. 48° E,

The Archean gneisses and schists are overlain by the Bow River
series consisting here, as elsewhere, of grayish conglomerates and
quartzites, and hard dark slates. The conglomerates are rather fine-
grained, the pebbles seldom exceeding a third of an inch in diameter,
and are crushed and altered in places into a schistose condition. The
pebbles consist principally of quartz and felspar. The Bow River
rocks are exposed along the river for two miles. They are succeeded
and overlain in turn by grayish unfossiliferous limestone similar in
character to that exposed below the mouth of the Tchutetzeca, and,
like it, probably belonging to the Castle Mountain group. It dips to
the south-west at angles ranging from 40° to 50°.

The three series of rocks briefly described above, viz., the Archean
gneisses and schists (Shuswap series), the Bow River conglomerates,
quartzites and slates, and the Castle Mountain limestones, occur in a
similar succession to that on the Omenica, so far as observed, all along
the Rocky Mountain range. In the section previously examined on
the Bow River the lower beds do not come to the surface, and in other
places the relationship is obscured by faults and overturns, but when-

*For a definition of this and the Bow River series, see Annual Report, Geol. Surv.
Can., vol. IL. (N.S.), pp. 240, 29 p.