58

In the part of the Yakoun basin exposed on the Tlell river
the beds are coarse arkoses derived from the underlying vol-
canics, with shales, some bands of massive sandstone, and a great
deal of fine quartzose conglomerate.

Farther north in the same basin the rocks are variable in
their nature, at the base consisting of volcanic arkoses, overlain
by shales and about 250 feet of fine massive sandstone. The
sections are not constant even over small areas. The section
found in the bore-hole of the Graham Island Coal and Timber
Syndicate, in the eastern part of section 36, is given in the ap-
pendix, together with other partial sections of the formation
obtained from cores of bore-holes.

East of Alliford point in Skidegate inlet a narrow sandstone
dyke was found cutting fine dense black shaly sandstones of
the Haida formation. The dyke, which is 4 inches wide in places,
is lenticular and splits into ramifying branches. It is vertical
in attitude and has a very sharp contact with the shales.!

In thickness, the Haida formation varies. At Skidegate
inlet, it is from 2,000 to 3,500 or 4,000 feet, while near Camp
Robertson it is nearly 5,500 feet. Here, the lower member is
from 2,500 to 3,000 feet thick, and the upper massive sandstones
are about 2,300 feet. The coal seam here occurs about 200 feet
below the base of the upper massive sandstones. The thickness
exposed in the Yakoun basin is probably under 1,000 feet.

Folding and Faulting. Folding in the Haida formation,
while locally severe, is gentle on the whole. Near the base
and in the vicinity of the coal seams and without doubt else-
where, close folds are found representing the relief of stress in
the less competent beds. Faulting is also a local phenomenon,
and several small faults, usually reverse, have been noted in the
coal openings at Camp Robertson and Camp Wilson (See Figures
12 and 22).

Relation to the Vancouver Group. The Haida formation
rests unconformably on the rocks of the Vancouver group and
includes fragments of these rocks. This relationship was noted
at Haida point, the Channel islands, and Maude island in

1 Cf. Clapp, C. H., Geol. Surv., Can., Mem. 51, p. 75.