5

There are several extensive exposures of the limestone and cherty
quartzite on the east slope of Thornhill mountain, and fossil shells and
Crinoid stems may be seen in the limestone in this locality. Other expo-
sures occur on the south slope of Kleanza mountain. There are several
isolated outcrops of limestone in the granodiorite on the south side of
Williams creek above an elevation of 3,700 feet. Here the limestone is
considerably altered with a development of epidote and garnets, and small
amounts of magnetite, pyrite, and chalcopyrite are found along the con-
tacts of the limestone. Three miles west of Amsbury flag station a con-
siderable thickness of finely bedded, crystalline limestone and marble out-
crops a few hundred feet north of the railway. ‘These occurrences are all
roof pendants in the Coast Range granodiorite. The contact of the series
with the overlying Hazelton group has not yet been observed and it is not
known whether the two formations are conformable.

HAZELTON GROUP

The Hazelton volcanic rocks of Jurassic age consist mainly of ande-
sites, tuff, and breccia. This formation outcrops along Skeena river
between Pitman and Kitsalas and underlies the greater part of the area
east of Skeena river from Zymoetz river north to mount Sir Robert. Beds
of argillite outcrop in Phillips creek at Brusk’s cabin 2 miles from the
Skeena and are probably interbedded with andesite. Along the Skeena
the andesitic lavas are massive and their structure is difficult to interpret,
but in general the flows dip in a northeast direction at moderate to steep
angles, and farther north they dip more northerly and appear to underlie
the Hazelton sedimentary rocks. On Kitsalas mountain at Usk the vol-
canics have an observed thickness of about 5,000 feet and the original
thickness must have been several thousand feet greater.

The Hazelton sediments, considered to be of Middle Jurassic age, are
principally sandstone, argillite, quartzite, greywacke, slate, tuffs, tuffaceous
sandstone, and conglomerate. This formation extends across the northern
part of the area, roughly from the vicinity of Kitsumgallum lake eastward
to the Canadian National railways and beyond, a distance of over 20 miles.
On the west and south these sediments are intruded by the batholith of
Coast Range intrusives which swings around in a series of apophyses.
Excellent sections of these rocks are exposed on Maroon mountain, Goat
mountain, and mount Couture. The formation is gently folded and strikes
east and west. The dips range from 30 to 75 degrees and average 40 degrees
to the north or south. The observed thickness of the sediments on Goat
mountain is 7,500 feet and the original thickness must have been greater
than 10,000 feet. A conglomerate horizon about 75 feet thick occurs at an
elevation of 4,000 feet on Maroon mountain. It has been traced around
the west side of Goat mountain and then east to where it crosses Douglas
creek at an elevation of 2,700 feet. Both the sedimentary and volcanic
divisions of the Hazelton group are cut by the Coast Range intrusives and
contain a great number and variety of mineral deposits.