107

massive, but in places is earthy and thin-bedded and holds narrow bands of
dolomitiec limestone. Thin veins and beds of satin spar are common and
anhydrite is Occasionally present in rounded nodules and thin beds. The
gypsum is overlain by a fractured and broken bed of limestone, but in many
places it reaches to the top of the cliff and is covered by only 5 to 15 feet of
drift. The deposit is very favourably situated for quarrying.

1Gypsum outcrops at several points in the escarpment west and south of
the brine springs at the forks of Salt river. Four miles south of the springs,
thin-bedded, white or greyish gypsum, containing occasional narrow layers of
anhydrite or beds of dolomite, is exposed in the cliffs for a length of half a mile
and with a thickness of 40 to 50 feet. North of this it appears to decrease in
thickness and is overlain by beds of grey, crystalline dolomite. At Little Buffalo
river 10 feet of impure gypsum is exposed at the base of the escarpment. At a
point in the escarpment 8 miles southwest of Fitzgerald there 1s an exposure
of 20 feet of thin-bedded, white gypsum overlain by 10 feet of dolomitic lime-
stone. The prevalence of sink-holes on the top of this escarpment, lying to the
west of Slave river, indicates that this mineral occurs throughout the greater
part of its length.

Ten feet of somewhat earthy, thin-bedded gypsum, of white, grey, or bluish
colour, overlain by 20 feet of limestone, outcrops on the west side of Slave river
a few miles below La Butte. Immediately below point Ennuyeux, on the same
river, thin-bedded, impure gypsum 4 feet thick is exposed near the water level
at a medium stage of the water, and at Bell rock, 7 miles below Fort Smith,
gypsum is said to have been struck in an excavation.

The numerous exposures in the Slave River country and the topographical
features indicate that the mineral is very widely distributed.

At Gypsum point on the north shore of Great Slave lake and along the
southwest shore of the north arm of the same lake, thin seams of flesh-coloured
gypsum occur between the bedding planes of caleareous sandstone and arenaceous
limestone.’

A bed of gypsum 130 feet thick is said to have been struck at a depth of
590 feet in well No. 1 of Athabaska Oils, Limited, located on Athabaska river
9 miles below MacKay.

In a section exposed by a small stream in the heart of Bear rock at the
mouth of Great Bear river the lowest beds seen consist of reddish and greenish
shales, alternating with layers of pink-coloured gypsum and cut by numerous

veins and seams of a white, fibrous variety of the same mineral. Thin layers of ©

gypsum interstratified with dark grey, shaly dolomite occur in several places on
mount Charles, on Great Bear river,® and a bed of gypsum more than 100 feet
thick has been observed.*

IRON
No important deposits of iron ore have yet been discovered in the Mackenzie

basin.
Hematite is found interbedded with quartzite of the Tazin series on Beaver-

lodge bay on the north shore of lake Athabaska. The quartzite here forms a

1 Camsell, C., Geol. Surv., Can., Ann. Rept., vol. XV, pp. 159 A, 167 A.
Geol. Surv., ‘Can., Sum. Rept., 1916. ;

2Cameron, A. E., Geol. Surv., Can., Sum. Rept., 1916.

3 Bell, J. M., Geol. Surv., Can., Ann. Rept., vol. XII, p. 25 C.

4Personal communication from EH. M. Kindle.

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