Glaciers,

Rock ex-
posures,

Landslip.

Rocks at

Black Cajon.

Laramie
rocks.

22 ¢ FINLAY AND OMENICA RIVERS.

The valley here has a width of about a mile and a half, and is
bordered by mountains, 4000 to 5000 feet above the river, belonging
to the Peak Range. Numerous small isolated glaciers, descending to
a height of about 2500 feet above the river, occur in the depressions
between the summits, but no extended ice-field was noticed. The ex-
panded lake-like portion of the Finlay has a length of about eighteen
miles. Near its head, the river divides into several branches, none
of which were explored by us. The western branch (called Thucatade
by Finlay) was ascended by Mr. Finlay, and is stated by him, in the
journal referred to before, to be thirty-five miles in length and to head
in a narrow lake, sixteen to twenty miles long, called Lake Thutade
by the Indians.

GEOLOGICAL OBSERVATIONS.

Omenica River Section.

Rock exposures on the Omenica commence at the Black Caifion, five
miles above its mouth. Below the Black Cafion the valley is cut
through the glacial and alluvial deposits which floor the narrow plain
bordering the Finlay. A good section of the latter, consisting here of
clays, sands and gravels, was observed about a mile above the mouth of
the river. A landslip of considerable magnitude occurred at this
point not long ago, by which material from the north bank of the
valley was carried right across the main channel of the river and
deposited on the further side. No permanent change in the course of
the stream was effected by this slide, as the blocked channel was
quickly cleared by the rapid river.

At the Black Cafion, the valley for half a mile is bordered by sharp.
rocky walls consisting of medium-grained muscovite gneisses, micaceous
and chloritic schists, and quartzites. At the upper end of the cafion
the gneisses and schists are overlaid by a bed of hard grayish limestone,
filled with mica, quartz, and other impurities. The general strike of
the rocks at the cafion is 8. 58° E. and the dip is south-westerly at an
angle of 28°. The gneiss and mica-schists of the Black Cation
represent the oldest rock series found in the Omenica district and are
undoubtedly of Archean age. They run in anorth-westerly direction
parallel to the course of the Finlay for many miles. Their extension
southward has not been worked out.

The Archean gneisses and schists of the Black Cafion, are succeeded
in the valley of the Omenica by a series of shales, sandstones and
conglomerates of Laramie age. These rocks occur in several places in