49

beds, many internal structures as faults, folds, etc., are not
readily observed. The top of the volcanics is nowhere seen,
and no complete sections of the formation have been obtained;
but, from the extent of territory underlain by these beds, it is
probable that their thickness may reach 5,000 feet. Dawson
estimates it at 3,500 feet.

Structure —External—Relations to the Maude Argillites.
On the south side of Maude island, and on the opposite shore of
Alliford bay, the Yakoun volcanics grade conformably down-
ward into the Maude argillites. Near the base of the formation
the rocks are very massive, greenish agglomerates, which form
bold cliffs on Maude island. The lowest strata definitely refer-
able to the Yakoun formation are very thick beds of bright
green agglomerate, made up of angular fragments 1 or 2 inches
across, in a tufaceous green matrix, often replaced by calcite.
These beds are underlain by thinner bedded, finer strata, the
whole clearly waterlain, and gradually passing into the beds
referred to the upper Maude.

Structure.—Relation to the Queen Charlotte Series. ‘The
Yakoun volcanics are unconformably overlain by the basal
marine sediments of the Queen Charlotte series. This re-
lationship is well exposed at Haida point, in the Channel islands,
and at the eastern end of Maude island. At these localities an
irregular surface, developed on the hard, resistant agglomerates
of the Yakoun formation, is seen to be covered by the coarse,
arkosic sediments of the basal Cretaceous. These soft, easily
disintegrated, younger beds fill the cracks and irregularities in
the surface of the older rocks, and include fragments of them.
Believing, as he did, that the sediments of Alliford bay were
Cretaceous, it is not difficult to see how Dawson was led to say
that this unconformity was unimportant.? The “passage beds”
on the east side of Alliford bay, on which he lays stress,’ while
truly transitional in nature, are wholly middle Jurassic in age,
and the passage is between two layers of agglomerate, not from
the Yakoun formation to the Cretaceous. As a matter of fact

1 Dawson, G. M., Geol. Surv., Can,. Rept. of Prog., 1878-79, p. 69B.
2 Dawson, G.M., Geol. Surv., Can., Rept. of Prog., 1878-79, p. 68B.
3Idem, p. 67B-68B.