General Geology
Age and Correlation

Fossils, as in the type area, are not abundant in the Takla Group of the
Nechako River area. Only three collections were made, two from the main unit
and one, consisting of indeterminate forms, from the marine part of the Red
Beds Unit. From tuffaceous argillites on Verdun Ridge, about 4 miles west of
Spencha Lake in the northwest quarter of the area, pelecypods were collected.
They were identified as Halobia sp. by F. H. McLearn, Geological Survey of
Canada, and are indicative of a Late Triassic age. Another collection of fossils
from the south side of Tetachuck Lake near Bryan Arm contained pelecypods
most of which are indeterminate. Included in this collection was a new species
of Trigoma which McLearn believed to be of Jurassic age, most probably Early
Jurassic.

Upper Triassic and Lower Jurassic rocks are widespread in British Columbia
but as they were laid down under eugeosynclinal conditions lithological variations
are numerous, making correlation of the Takla with other groups difficult. The
Nicola Group of Ashcroft and Nicola areas (Duffell and McTaggart, 1952,
pp. 29-31) closely resembles the Takla in lithology but is only known to be of
Upper Triassic age. Lithologically similar but non-fossiliferous rock occurs in
Anahim Lake map-area (Tipper, 1957) and in Whitesail Lake map-area (Duf-
fell, 1959, p. 33). In the latter area the rocks were mapped as Takla Group. A
strict correlation with other well-known groups in northwestern British Columbia
and in southern British Columbia would be unwise and impractical at present.

Hazelton Group

Hazelton Group was the name proposed by Leach (1910, p. 62) for a thick
section of pyroclastic sedimentary rocks near Hazelton, British Columbia. After
further work he decided to include a succession of lavas, then known as the Por-
phyrite Group, as part of the Hazelton Group (Leach, 1911, p. 93). The group
as a whole may be rather broadly defined as pyroclastic sediments and porphyritic
andesites and basalts of Jurassic age. Later work leads to some modifications, but
the Hazelton Group was never rigidly defined. (See p. 18, and Tipper, 1959a.)

This group is characteristically variegated, red to green bedded tuffs and brec-
cias with red, brown, purple, or green andesite and basalt. Sedimentary rocks include
conglomerate, greywacke, and some argillite. The group was laid down mainly
under marine or near-shore conditions. Non-marine strata although present are
not abundant.

The Hazelton Group was originally thought to be Middle Jurassic, Late Ju-
rassic, and Early Cretaceous, but more recent information suggests that this range
is too broad (Tipper, 1959a, p. 40). Mapping in Bowser Lake area of north-
west British Columbia, Roots (1957) outlined an extensive area of sedimentary
rocks presumably of Late Jurassic to Early Cretaceous age. For the following

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