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of an older batholith and some of the stocks of Portland Canal area may
be associated with it.

The exact age of the Coast Range intrusives is not determinable in Port-
land Canal area. They intrude the Hazelton group rocks and these are
probably not younger than Jurassic. The intrusive may, therefore, be late
Jurassic or younger.

DYKES

Dykes cut the Hazelton group rocks and the Coast Range intrusives.
The sediments of the Hazelton group are cut by more dykes than the vol-
canics and these by more dykes than the Coast Range intrusives. The
dykes range in age from Jurassic to Tertiary, in composition from gabbro
to quartz porphyry, and in width from 1 inch to 100 yards or more. They
have not been studied systematically and many more types than those to be
mentioned may exist. It seems fairly certain that the dykes were not all
from one source.

Commencing in the western part of Salmon River district a zone of
closely spaced dykes of quartz porphyry and quartz diorite extends south-
eastward across Bear River ridge and Bear River valley to the Cambria
snowfield. This zone has a width of about 14 miles. Outside the zone
country rock predominates, whereas within the zone dykes form 50 per cent
or more of the whole assemblage.

In Salmon River district the dykes in the belt are hardly as closely
spaced as in Bear River valley. Where the belt traverses the argillites
north of Slate mountain in Salmon River valley only about half as many
dykes are present as in volcanic rocks on either side of the argillites. The
tops of several dykes in the argillites can be seen, the dykes being partly
roofed by argillites. These tops are very blunt. One 20-foot dyke pinches
out in a distance of 8 or 4 feet. The argillites are horizontal and may not
have fractured as readily as the volcanics. It is unlikely that the upper-
most argillites are younger than any of the dykes.

On the upper part of Bear River ridge the individual dykes are dis-
tinct bodies separate from one another. On the lower slopes of the ridge,
in Bear River valley, the dykes are more closely spaced and due to coales-
cence are larger. Still lower down the slopes the dykes so coalesce that
the assemblage has the aspect of a stock. Farther southeast, in the vicinity
of mount Dickie, the dykes become more and more widely spaced, narrower,
and fewer, until the zone loses its identity.

Most of the dykes are vertical, strike parallel to the trend of the
zone, and are between 50 and 150 feet wide, but narrower dykes are fairly
numerous and wider dykes exist. Most of the dykes have approximately
the mineral composition of the Coast Range batholithic rocks. They con-
tain less orthoclase, however, and are mostly quartz diorites. Some are
quartz porphyries and a few small dykes resemble gabbro.

The dykes of this zone may be the top of an elongated stock. It is
possible that a zone of weakness developed parallel with the border of
the Coast Range batholith during its intrusion and that magma from the
batholith riddled this zone with dykes. If this idea is correct the dykes
will coalesce with the batholith in depth.