Whitesail Lake Map-Area

This extension of the Takla group to include Middle and Upper Jurassic
strata caused some confusion with the Hazelton group, which is itself com-
posed largely of Jurassic rocks. It might be noted here that fossils collected
from the Middle Jurassic, Hazelton group rocks of the Whitesail Lake area,
were similar to those collected by Lord from the Middle Jurassic strata of
the McConnell Creek area.

The discovery by Tipper (1955) in Nechako River map-area of an
erosional break between the Lower and Middle Jurassic beds provides a
definite marker as a basis of separation between the Takla and Hazelton
groups. In Nechako River area the base of the Middle Jurassic beds is a
medium to coarse conglomerate, commonly containing numerous chert
pebbles. Tipper believed this to be a shoreline deposit with the landmass
to the east. He was able to follow this zone of coarse clastics down the
length of Nechako River map-area, along its western border. It outcrops
only in the northeast corner of Whitesail Lake map-area, where it swings
westward from its northerly trend in Nechako River area. Tipper considered
this erosional break to be the logical horizon for the division between the
Takla and Hazelton groups, at least in the Nechako River area, and this line
of demarcation applies equally well to Whitesail Lake area. Therefore, in
Whitesail Lake area, the boundary between the two groups is placed at the
close of the Lower Jurassic, and the Takla group will be restricted to Upper
Triassic and Lower Jurassic strata.

Distribution

Outcrops in Whitesail Lake map-area that have been correlated with
the Takla group occur only along the eastern boundary of the map-area,
and are westward extensions of much larger areas of similar rock occurring
in Nechako map-area. In Whitesail Lake map-area rocks of this group form
a prominent hill in the northeast corner, about 7 miles north of Ootsa Lake,
which is used by the British Columbia Forest Service as a lookout station,
known as Verdun. There an upfaulted block brings these older rocks to
the surface over an area of about 6 square miles adjacent to the eastern
boundary of the map-area.

Farther south, near the east end of Eutsuk Lake and the west end of
Tetachuck Lake, a series of massive green andesites with some minor lime-
stone, tuff and breccia is present, which has been included with the Takla
group. These rocks occur both north and south of the lakes and underlie
an area of about 100 square miles.

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