7

The Tertiary rocks have been deformed to some extent,
and locally dip at high angles.

Surface formations on Graham island consist of glacial
stratified drift, till, and alluvium. Over large areas the bed-
rock is deeply buried, rendering the deciphering of the structure
difficult.

ECONOMIC GEOLOGY.

The deposits of economic value found on Graham island
comprise coal, lignite, clay, building stone and limestone, pos-
sibly oil-shale, and gold. Deposits of black tar also are found,
but are not considered to indicate the presence of petroleum.

Coal is found in the Haida formation of the Queen Char-
lotte series, of Upper Cretaceous age. The coal has been ex-
posed at several localities, and the seams show considerable
variation, caused by original differences in deposition as well
as by later changes. Coal seams have been prospected at
Cowgitz and in the Slatechuck valley on Skidegate inlet; at
Camps Robertson, Anthracite, Trilby, and Wilson, and near
Yakoun lake, all in the interior.

On Skidegate inlet the seams dip at high angles and are
much disturbed and the measures are intruded by volcanic
rocks, which have changed the coal, which is ordinarily bitum-
inous, to an anthracitic variety. Somewhat similar relations
are found near Yakoun lake, where the coal is also altered.
At Camp Robertson the coal is well exposed in several prospect
openings. One seam is found, which is folded and faulted in
such a way that previous investigators have supposed that two
or three seams existed. The maximum thickness of this seam
is nearly 9 feet, and the maximum thickness of coal it contains
is 3 feet 103 inches, in several bands. The coal is hard and
black, and is a low grade bituminous variety, high in ash. The
horizon of the seam extends over a considerable area south and
west of Camp Robertson, but some parts of this area may not
contain coal. At Camp Anthracite south of Camp Robertson,
the same seam is also exposed. At Camp Wilson the best seam
of the district is exposed in several openings. It is from 4 to