BELLS GRAHAM ISLAND 23 B

TERTIARY.

The Tertiary rocks of Graham island are divisible into two parts, viz.:
the sedimentary, comprising sandstones, shales and conglomerates, with
occasional beds of lignite; and the igneous, which form a large part of the
western coast north of Rennell sound, and are exposed at intervals along
the north shore, west of Masset inlet. The rocks of the second division

will be discussed under the head of igneous.

The general distribution of the Tertiary sediments must be, to some ex-
tent, inferred. So great is the mantle of drift, and so extensive the
forest growth, that rock outcrops are rarely seen. From the evidence ob-
tainable it would appear that the part of the island east of a line drawn
from a point a short distance east of the Indian village of Skidegate,
across country to near the village of Masset, is underlaid by these rocks,
outcrops of which are seen at Chinookundl brook, between Skidegate and
Lawn hill on the south, and at Skonun point, about four or five miles east of
Masset entrance. These rocks are also seen on the north shore of Tow
hill, underlying the trap rocks which form that headland, and on the shore
of Yakan point, two miles west. On the east coast no rock exposures are
seen, with the exception of those in the brook just mentioned and the ig-
neous mass of Lawn hill; but, from the fact that pieces of lignite, which
may be torn by storms from beds which lie out to sea, are frequently seen
along this shore, it is possible that a portion of the wide passage between
this island and the group of islands lying along the British Columbia
coast is underlaid by the Tertiary sandstones and coals.

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~ The character of the sandstones belonging to this formation can be well
seen at the points on the north shore east of Masset. Thus, at Yakan
point, two miles west of Tow hill, the rocks are generally coarse greyish
quartzose grits, having a calcareous cement and holding scattered pebbles.
They show much false bedding and irregularity of deposition, so that the
exact dip of the formation at this point cannot be accurately determined.

Thin beds of shale also occur, both grey and blackish, on the whole
similar to those seen at Skonun point to the west, except that no lignite is
seen here; as a whole, however, the rocks are quite distinct from those of
the Cretaceous as exposed along the Skidegate shore and about the Honna
river. The sandstones are often perforated by holes, apparently the work

of rock borers.

The outcrops at Skonun point, about five miles east of the en-
trance to Masset inlet, are mostly of a grey grit with bands of shale