12

that the sediments overlie the volcanics to the east, and they are correlated
on structural grounds with the easterly band of Salmon River district and
with the upper part of the Hazelton group.

Another northerly striking band of sediments begins at the south end
of Summit lake and extends in a widening band northward beyond the
mapped area. This body, although argillaceous, contains much lighter
coloured sediment and in many places has been severely sheared and con-
verted into light-coloured sericite schists. The shearing and conversion
to schists is, however, local and is a notable feature only in the vicinity
of Tide Lake flats. Judging from the alteration exhibited it might be con-
cluded that these sediments are older than any previously described. The
attitude of the beds furnishes little reliable information, but in the northern
part of the area the dips on the eastern side are away from the adjacent
volcanic rocks. In the southern part the dips are vertical. The dips, there-
fore, suggest that the sediments occupy an overlying position with. respect
to the volcanics on the east. In the vicinity of Tide Lake flats the rocks of
the volcanic series are in the main intrusive. Small bodies of granite also
occur there and it is quite possible that the metamorphic changes in the
sediments could have been affected by these later intrusives. Though this
body of sediments cannot be correlated with assurance with the upper part
of the Hazelton group, it is believed to form part of the group. The prob-
lem can probably be solved by geological work farther north on Bowser
river.

The upper part of the Hazelton group sediments south and east of
Portland Canal area is not known to contain mineral deposits. Sediments
that seem to be well down in the group, however, as at Alice Arm and in
Bear and Marmot Rivers districts, contain numerous mineral deposits. The
western belt of sediments in Salmon river and those to the north in upper
Bowser river also contain mineral deposits. The sediments east of Portland
Canal area are in general farther from intrusives and their lack of mineral
deposits probably depends more on their greater distance from possible
mineral sources than on any innate unfavourable nature of the rocks.

The prevailing rock amongst the Hazelton Group sediments is black
argillite which through addition of coarser clastic grains varies to quartzite
and greywacke. The argillites are mostly black and contain as a rule pyrite
in fine grains. The quartzites vary in grain from cherty rocks to coarser
types which by addition of small rock fragments grade to greywacke. The
quartzites commonly contain some feldspar, pyrite, iron oxide, and apatite,
some contain considerable biotite, and some have much calcite cement. The
rock at the falls on Canyon creek is a black quartzite holding much biotite.
The greywackes commonly have a calcite cement. Many hold grains of a
porphyritic rock. Others contain pebbles of argillite and chert. The
fossiliferous rocks at the head of Kitsault river are calcareous greywackes.

Some of the sediments have formed very quickly and consist of rock
fragments and crystals and broken crystals of hornblende, augite, feldspar,
and quartz. The conglomerates carry pebbles of varous rock types usually
in a sandy, argillaceous base. Conglomerates holding pebbles of slate and
chert are the commonest types. On a ridge northwest of LeRoy mountain
a fine pebble conglomerate has a calcareous cement. Conglomerates by
admixture of voleanic ejectamenta grade into breccias.