17

Miocene epoch, perhaps extending into the Pliocene, the north-
eastern portion of Graham island was the scene of littoral sedi-
mentation which was, as in the Upper Cretaceous, in part
estuarine and fresh water; so that vegetable accumulations
formed, now represented as beds of lignite. This sedimentation
was cut short by aresumption of volcanic activity on a tremen-
dous scale, by which the Masset formation was built up.

It is probable that at this time several volcanoes were in
action, vomiting showers of fragments and floods of lava. This
vulcanism is best placed in the early or mid-Pliocene, and the
close of this epoch was marked by a recurrence of deforming
forces which have locally severely flexed the Tertiary formations,
but in general have disposed them in broad open folds. This
deformation uplifted the sediments of northeastern Graham
island a few score feet to their present position a short distance
above sea-level and is probably responsible for the narrow
trench which the Honna river now occupies in its broad valley.

Since the close of the Tertiary, the area has been subjected
to subaérial erosion which in a large measure shaped the present
topography. During the Pleistocene, the Queen Charlotte
range was covered in part at least with an ice cap; and glaciers
flowed from the range along the fiords of the west coast and also
through Skidegate inlet, where strong glacial scouring has been
noted. That ice occupied at least part of the lowlands also is
indicated by the occurrence of till in so many localities. The
well stratified glacial sands and clays found in several places
indicate lacustrine conditions during part of the glacial occupa-
tion.

There are some evidences of a recent uplift having affected
Graham island. Near the mouth of the Yakoun river, in a bank
of stratified clay and gravel, numerous recent shells were found,
identical with those now living below high tide level in Masset
inlet. The highest position of these shells in the bank was from
15 to 18 feet above high tide. Dawson! describes similarly
uplifted shell banks at Naden harbour and on the Mamin river.
He also? mentions seeing terraces in‘ Skidegate and Masset

1Geol. Surv., Can., Ann. Rept., 1878-79, pp. 94-95B.
2 Loc. cst.