82

Alteration.
Considerable; feldspar always partly Very slight; small amounts of kao-
or wholly kaolinized; augite linization; much of feldspar and
altered to chlorite, etc. augite quite fresh.

SUPERFICIAL DEPOSITS.

GLACIAL DRIFT.

Glacial drift, both stratified drift and till, occurs in abund-
ance on Graham island. The relative distribution and amounts
of each cannot be determined with any degree of accuracy owing
to the absence of exposures.

Inthology. The stratified drift is composed of laminated
fine blue clays, sand, and gravel. Much of the clay is suitable
for brickmaking.

The unstratified till is made up of angular, subangular, and
rounded boulders of varying sizes up to about 3 feet in diameter,
embedded in a matrix composed of sand and gravel in varying
amounts. The boulders consist of several varieties of igneous
rocks and of rocks of the Queen Charlotte series, and many of
them show glacial scratches and striations.

Origin. The stratified glacial drift has been laid down in
water and probably was formed in lakes or estuaries caused by
glacial damming, as it seems improbable that a sufficient uplift
has occurred to make it possible that the stratified drift seen
can be of marine origin. The unstratified drift has all the char-
acteristics of boulder till, and was formed by the usual accumu-
lation of heterogeneous material. Some of the till is slightly
sorted, and perhaps modified by water action.

DAWSON’S DESCRIPTION OF THE SUPERFICIAL DEPOSITS.

The following description of the superficial deposits as
exposed in the cliffs on the east coast of Graham island is taken
from Dawson’s report.!

1 Dawson, G. M., Geol. Sury., Can., Ann. Rept., 1878-79, pp. 91B-93B.