44

and 389. In 1943, Williams collected fossils of the Nathorstites fauna on
the top of a high hill north of mile’ 383-2 and just west of the bridge over
Tetsa River. He also collected specimens of this fauna in a road-cut at
about mile 387 on the Highway and at higher elevations in that vicinity.

Age and Correlation

The age and correlation of the Liard formation will be discussed
subsequently, when dealing with the ‘Grey beds’, where also the age of the
Nathorstites fauna will be considered.

‘FLAGSTONES’
Definition

‘Flagstones’ is a provisional name assigned by McLearn (1947A) to a
well-defined unit between the Toad formation and the ‘Dark siltstones’ in
Halfway and Sikanni Chief Valleys, and in other parts of northeastern
British Columbia. The unit consists of 235 to 380 feet of grey, flaggy,
thin-bedded, calcareous siltstones, and in places fine, massive, calcareous
sandstones and limestones. It lies, apparently conformably, between the
Toad formation and the ‘Dark siltstones’.

Halfway River Valley

A good section of the ‘Flagstones’ is exposed on the Fourth Gully of
Mount Wright, on the north side of Halfway Valley (See Plate III B).
About 200 feet of flaggy, calcareous siltstone and fine sandstone are overlain
by 180 feet of massive, grey, thick-bedded, calcareous, fine sandstone and
limestone containing ‘Coenothyris’ (McLearn 1947A, 1948).

The structure is almost flat, and the ‘Flagstones’ are underlain down
the gully by the Toad formation and up the gully by the ‘Dark siltstones’.

Sikanni Chief River Valley

The ‘Flagstones’ are exposed on Hage Creek (See Figure 6) on the west
slope of Mount Hage, on the south side of the Sikanni Chief River Valley
(McLearn, 1947A). They consist of about 235 feet of unfossiliferous,
thin-bedded, flaggy and massive siltstone. The grey, massive, thick-
bedded, fine, calcareous sandstone and limestone of the Mount Wright

section do not appear to be present on Hage Creek.

The ‘Flagstones’ probably occur in other parts of northeastern British
Columbia but have not yet been recognized.

Age and Correlation

It is probable that the ‘Flagstones’ of Halfway and Sikanni Chief
River Valleys are equal to some lower part of the Liard formation in Tetsa
and Liard Valleys. They lie between beds of the Middle Triassic, Anisian,
Toad formation and those of the Middle Triassic, Ladinian ‘Dark siltstones’.

The species of ‘Coenothyris’ in the upper part of the ‘Flagstones’ ‘of
Mount Wright resemble species of the same genus in the ‘Dark siltstones’,
and suggest an age nearer to that of the ‘Dark siltstones’ than to the Toad
formation.