8
edge of the area where the syncline pitches southeast. Southeast of Quartz
creek the McLeod series outcrops along the centre of the syncline, but
northwest of Quartz creek the series has been removed by erosion. :

The Cassiar batholith intrudes the southwestern limb of the syncline
and cuts across the structural trend of the older rocks at an acute angle.
Paleozoic rocks of the Dease series are exposed next to the batholith in
the northwestern part of the area, but to the southeast this band of
Paleozoic sediments narrows and disappears, and at Fourmile creek the
granite is in contact with the McLeod series at the axis of the syncline.

The sedimentary and volcanic rocks between the Cassiar and Hotailuh
batholiths strike north 30 degrees to 80 degrees west, and, as a rule, dip
at medium to high angles to the northeast. The regional structure appears
at first glance to be a simple homocline, but the distribution of rocks proves
that this is not so. The McLeod series forms the northern side of Hotailuh
mountains and appears to dip under the older Dease series to the north.
Farther to the north, around the headwaters of Eagle river, a band of the
McLeod series outcrops between northeasterly dipping sediments of the
Dease series. The Dease-McLeod contact along the northern edge of this
band is slightly overturned to the southwest. If the structure of the Dease
series were homoclinal the massive limestones that outcrop along the
northern side of the wide valley between Cassiar and Hotailuh mountains
should be the oldest beds of the series. However, poorly preserved fossils
of Upper Triassic age have been found along the strike of these limestones
some 20 miles to the west in Dease Lake area, indicating that those
massive limestones may be near the top rather than near the base of the
Dease series.

Although this structure has not been interpreted it probably resulted
from close folding and overturning on a large scale, combined with some
faulting. Faulting on a small scale is common in both the Dease and
McLeod series. However, there is little direct evidence of large-scale
faulting unless the alined valleys along the southern Dease-McLeod con-
tact be regarded as topographic evidence of a major fault in the under-
lying rocks.

The contact between the batholithic rocks and the McLeod series is,
as a rule, fairly flat dipping in Hotailuh mountains. Bordering the con-
tact the intruded rocks are in many places overturned and disrupted by
minor thrust faults with displacements of as much as 100 feet. The strike
of the McLeod series in this part of the area commonly parallels the con-
tact of the Hotailuh batholith. Along at least a part of the northern
boundary of the Cassiar batholith the contact with the McLeod series is
believed to be a steep, northeasterly dipping, normal fault. The McLeod
series is unaltered and its contact with the granite is marked by cleft-like
depressions in the hill-sides and by saddles in the ridges.

INTRUSIVES

The intrusives of the area may be divided into three groups, namely:
serpentine and related basic rocks; granitic rocks of the Cassiar and
Hotailuh batholiths; dykes and plugs. Granitic rocks cut the serpentine
and the granites in turn are cut by basaltic dykes.