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Collection 3FA, from quartzite outcrop on south shore of Tsayta Lake,
approximately 1 mile west of the narrows; includes Pustula sp. and a
large striated brachiopod suggestive of Meekella kueichowensis Huang.
Age: probably Permian.

Upper Triassic

The Upper Triassic rocks consist essentially of interbedded
argillite, greywacke, and tuff with, here and there, beds of con-
glomerate and limestone. ‘The argillites are black, carbonaceous rocks
in beds a fraction of an inch to 6 inches thick. The tuffs and grey-
wackes weather blue-grey to buff, are fine- to medium-grained, and
form beds that vary from less than an inch to 10 feet in thickness.
They consist largely of fragments of cherty and volcanic rocks, quartz
and feldspar, in varying proportions. Intermediate types, best termed
tuffaceous greywackes, are the most widespread. Many beds grade from
coarse-prained, tuffaceous greywacke at the bottom to argillite at
the top, These rocks also exhibit good crossbedding. Beds of con-
glomerate, 10 to 25 feet thick, outcrop on Halobia Creek. Pebbles in
the conglomerate are angular to rounded, ana up to 3 inches in diameter.
Most of them are of grey chert and black argillite; a few are of grey-
wacke, limestone and volcanic rocks. The matrix is gritty. Beds of
grey limestone, 15 to 20 feet thick, outcrop along Rottacker Creek.

The maximum thickness of the Upper Triassic section is probably
well over 2,000 feet. The diagnostic Upper Triassic fossil Halobia
was identified from argillite outcropping along Halobia Creek.

Jurassic’ «

The Jurassic formations consist of lavas, tuffs, and sedimentary
rocks. The lavas are best exposed in the mountains east of Silver Creek,
and are green, grey, black, and red porphyritic and non-porphyritic
andesites and basalts. The porphyritic types contain phenocr)sts of
feldspar, pyroxene and amphibole. Intercalated with the lavas are
green and grey andesitic tuffs and breccias. About 4 miles south of
Omineca River opposite Duckling Creek, a lens of grey, massive lime-
stone, 2,200 feet long and 400 feet thick, is interbedded with lavas.

A medium-grained, green andesitic tuff outcrops east of Indata
Lake. It consists of angular fragments of andesite, basalt, volcanic
glass, pyroxene, amphibole, pink and white feldspar, chlorite, and
quartz. Fragments of volcanic glass constitute more than 50 per cent
of the rock. In places the tuff grades into an andesitic breccia, in
which the larger fragments range from 3 to 1 inch in diameter and in-
clude a few of limestone and chert.

The section exposed along Silver Creek consists of at least
200 feet of limestone and shale overlain conformably by 1,000 feet
or more of tuffs and lavas with intercalated sandstone. shale, and
conglomerate. The basal limestone is a compact, lavender-grey rock
in a bed 150 feet thick. Associated shales are black, carbonaccous
rocks in beds 1 to 6 inches thick. These rocks may be of Upper Triassic
age. The overlying volcanic rocks comprise buff, red, green, purple,
grey and black, compact tuffs and red and green porphyritic andesites.
At least 300 feet of conglomerate, sandstone, and shale are interbedded
with them. The conglomerate consists chiefly of sub-rounded to angular
pebbles of argillite and quartzite in a pinkish grey siliceous matrix.
Pebbles up to 4 inches across were observed. The sandstone and shales
are grey and black, thinly bedded rocks. Beds average % inch to 4 inches
in thickness, the sandy beds being the thicker.