General Geology

Certain greenstones at the northeast end of Troitsa Lake and on
Kasalka Butte and Huckleberry Mountain may belong to the Takla group
but, due to lack of definite evidence and the possibility they may be lower-
most Middle Jurassic, they have been included with the Hazelton group.

Lithology
Upper Triassic Rocks on Verdun Hill

The rocks composing Verdun hill consist of andesitic and basaltic
flows, greenish grey to red andesitic breccia and tuff, fine-grained green to
grey fossiliferous greywacke, and dark argillite. The whole assemblage has
undergone metamorphism, and chlorite and epidote are common secondary
minerals. The flow rocks are slightly porphyritic with prominent feldspar
laths up to 4 inch in length. Thin sections show the feldspars and ferro-
magnesian minerals to be broken down with the production of zoisite, sericite,
calcite, chlorite, magnetite, and epidote. Both pyroxene and amphibole are
present as primary minerals. Feldspars are rarely zoned. Feldspar laths in
the groundmass show flow structure around the larger phenocrysts.

The fragmental nature of the breccias is best observed on a weathered
surface where the fragment boundaries are accentuated. Commonly on a fresh
surface it is difficult to distinguish fragment from matrix. Fragments vary
in colour from greenish grey to brown and red, and in size from a fraction
of an inch to 10 inches, most fragments are from 4 inch to 14 inches across.
The matrix consists of fragments of tuff size but of the same material as the
larger fragments.

The tuffs interbedded with the breccias are hard, dense, fine-grained,
red to green rocks with banding as fine as ;'; inch. The fossiliferous grey-
wackes or water-lain tuffs are fine-grained, grey to grey-green rocks, thinly
bedded, with minor bands of chert and narrow partings of argillite.

Rocks near Eutsuk and Tetachuck Lakes

Rocks in the vicinity of Eutsuk and Tetachuck Lakes assigned to the
Takla group are massive, green, andesite and basalt flows and minor argillite
and limestone. The flow rocks, which form the greater part of the group,
are similar to those described from Verdun hill. Some impure, narrow
limestone beds and minor argillites occur between the flows. Some of the
flows contain sufficient pyrite to present a rusty appearance on the weathered

surface.

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