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The second division of Ingenika group rocks in the northern part of the
map-area embraces a belt composed dominantly of limestone, which extends
northwest from the westernmost ridges of the Butler Range east of Tomias
Lake, through Lookout Hill and Ingenika Crag, and includes Forres Moun-
tain, the valley of Pelly Creek, and probably the Espee Range. Blue-grey,
massive to thick-bedded limestones predominate, although almost all large
exposures show a few beds of brown to ivory-coloured, sugary material,
which in places contains considerable muscovite. A few limestone beds,
particularly the impure, carbonaceous or argillaceous varieties, are thin
bedded. Oolitic beds have been found in each of the main areas of lime-
stone outcrops within this belt. A few bed-like bands of limestone breccia
outcrop east of Pelly Creek and on Forres Mountain. On the south slope
of Forres Mountain, in Pelly Creek canyon, and east of Pelly Creek near
the north border of the map-area, several beds of limestone are strongly
pyritic; one bed about 10 feet thick, on Forres Mountain, appears to con-
tain about 10 per cent pyrite for a distance of nearly half a mile. Other
beds in this massif show a polygonal fracture pattern, confined to bedding
surfaces, which may be mud-cracks. Where they occur in thicknesses
greater than 100 or 200 feet, the limestones of this division are almost
invariably highly contorted, and commonly isoclinally folded; consequently,
no estimate of their true thickness can be made. The chloritic phyllites,
schists, and quartzites interbedded with the limestones are in relatively
minor proportion, and are in general similar to those typical of Ingenika
group rocks elsewhere.

In the Espee Range, the main limestone member is overlain by at least
3,000 feet of finely interbedded, sedimentary rocks that exhibit a wide range
of composition. Included in this assemblage are chloritic slate and schist,
chloritic quartzite, quartz-pebble conglomerate, greywacke, siltstone, fine-
grained light green shale or tuff, beds of green and purplish impure lime-
stone, and relatively pure, grey, oolitic limestone.

The limestones of Mount Tsaydizkun and adjacent ridges in the north-
east corner of the map-area are in most respects similar, and may be strati-
graphically equivalent, to the rocks of the limestone division exposed on
Ingenika Crag and east of Pelly Creek. The Mount Tsaydizkun rocks
include a relatively high proportion of limestone breccia.

Sink holes were observed in the limestone at the north end of Butler
Range and on Lookout Hill. The largest explored sink hole, whose mouth
is near the summit of Lookout Hill, leads to a series of small caverns and
tortuous passages. The passages follow both joint systems and bedding
planes.

The third division of Ingenika group rocks is exposed in an irregular
area extending northwest from Ingenika Cone and Flood Creek to the north
border of the map-area, including Mount Isola, Barrier Peak, and most of
the Russel Range. This division is characterized by a predominance of
quartzite, interbedded with fine conglomerate, grit, chloritic slate, and schist.
At least 60 per cent of the lower 7,000 feet of strata exposed in the Barrier
Peak area and in the Russel Range is estimated to consist of quartzite,
which in this area ranges from pale golden brown to pure white, and is com-
pact and massive to sugary in texture, with grain size ranging up to sy
inch. Most of the quartzites contain more than 90 per cent quartz; in many
beds no other mineral, except very minor stains of limonitic material, can