Petes ede en
LE GIG? UOT COME EEA Pe

Sahn pa TASS alee

76

river the Peel has cut a valley 500 to 700 feet deep in these sediments, and about
5 miles below the canyon a section in the bank shows 200 feet of yellow and red
shales, which towards the base are interbedded with layers of sandstone. This is
succeeded downward by massive sandstone 50 feet thick, underneath which occur
about 150 feet of very fissile, rusty, pyritous shale. The glacial drift in this
section is about 40 feet thick. Northward the shales gradually increase in
thickness until they predominate over the sandstones. The sediments lie in
gentle undulations. A good section of Cretaceous rocks is obtained in mount
Goodenough, which is 3,000 feet high and lies to the west of the Mackenzie
delta, 2 miles from Huskie river, the western branch of the Peel. The strata
are horizontal or only slightly folded. “At the base is a thick series of black
shales, which towards the top contain beds of very hard clay ironstone. These
weather red, and the outcrop can be traced by its colour for miles along the
eastern face of the mountains. These red beds contain remains of Ammonites,
while the underlying and enclosing black shales are also fossiliferous. The
shales are gradually replaced upwards by argillaceous sandstones, and these
again by siliceous sandstones. These latter become metamorphosed to quartzites
and constitute the upper members of the series.’

Nearly horizontal Cretaceous sediments surround the western and northern
portions of Great Bear lake, reaching to within 30 miles of Fort Confidence,
and extending down Great Bear river to within 7 or 8 miles of its mouth, being
replaced, however, at the rapid by Paleozoic strata that form the range of
mountains cut by the river. Around the lake there are few outcrops of rocks
of this formation. Shales and sandstones are exposed along Smith bay, and
the Scented Grass hills represent a low anticline, composed of hard sandstone,
which forms Gros Cap peninsula. Above the rapid on Great Bear river there are
numerous exposures of rocks in which some fossils are found2 The western
part of the peninsula north of McTavish bay is probably underlain by Cretaceous
sediments, and Richardson’s notes indicate that Cretaceous sediments are
exposed in Grizzly Bear mountain which forms the promontory between MeVicar
and Keith bays.

Tertiary

Tertiary sediments occupy a few small areas in the Mackenzie basin.

The Paskapoo formation is exposed on Pembina river near longitude 115
degrees west, where a thickness of 50 feet or more of yellowish-grey sandstones
overlies 70 feet of concealed rock resting upon a seam of coal. The formation
extends some distance to the west.? Shales and sandstones of this formation are
exposed on the summits of Swan hills south of Lesser Slave lake.

“Tertiary beds occur at the mouth of (Great) Bear river and occupy a basin
of about thirty to forty miles in length and twenty to thirty in breadth. They res¢
unconformably on the underlying Cretaceous shales and Devonian limestones.
They are lacustral in origin and consist largely of discordantly bedded sand, sandy
clays, clays, and gravels. Beds of purely argillaceous material, usually somewhat —
plastic in character, are also present, and seams of lignite and carbonaceous shales
not infrequently constitute a considerable portion of the BCGHION «cee fo
The beds have an anticlinal attitude on the whole, but are usually nearly hori-
zontal. They have a minimum thickness of 600 feet.”

1 Camsell, C., Geol, ‘Surv., Can., Ann. Rept., vol. XVI, p. 46 CC.

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

3McEvoy, James, Geol. Surv., Can., Ann. Rept., vol. XI, p. 24.D.
#McConnell, R. G., Geol. Surv., CGan., Ann. Rept., vol. IV, p. 22° 1p. é