macks, where production began in 1900 and where it rose
to a peak of 16,185 tons in 1910. These mines owe their
development to their easy accessibility, but production
has been held down by the limitations of the local market.

Petroleum

A few basins within the Cordillera may have oil possi-
bilities, but the prospects of most are not attractive. The
Northern Foothills area, astride the Alberta-British Columbia
boundary and extending to the Lower Liard River, is, how-
ever, believed to contain some 40,000 square miles of potential
oil-bearing territory. East of the Rockies, the great basin
of the Mackenzie River is, at present, regarded as the most
favourable ground for oil prospecting in the Dominion.
In the immediate valley of the river, extending 1,000 miles
from Great Slave Lake to the Arctic, the essentials for
potential oilfields exist in an area of 150,000 square miles.

Throughout the length of the Mackenzie Valley,
sedimentary formations aggregating several thousand feet
in thickness overlie the complex of Precambrian rocks.
These sediments are dominantly marine and of Palaeozoic
age. In places, the Paleozoic rocks are overlain uncon
formably by Cretaceous and Tertiary beds. The strata
have been folded, but, in general, the dip of the beds is
comparatively gentle.

Here, then, we have conditions essential for huge
potential oilfields—probably the largest comparatively
unexplored potential petroleum region in.North America.
Surface evidence of oil in the form of seepages occurs at
numerous points, mainly, if not entirely, in Devonian rocks.
Some of these seepages were known to the early explorers,
but the remoteness of the region, the huge distances involved,
the lack of modern transport facilities, dependence on river
transport, and the short summer season have been retarding
factors, and development in the region has been slow.
Some exploratory surveys had been carried out by the
Geological Survey, but it was not until 1920, when a test
well drilled about 50 miles northwest of Fort Norman
brought in oil in commercial quantities, that serious atten-
tion was paid to oil prospecting.

In the succeeding four years, a number of parties sent
out by the Geological Survey made investigations in various
parts of the area and their results, together with concurrent
geological work carried out by Imperial Oil, Limited, formed
the basis of infomation up to the beginning of the Canol
development in 1942. ;

In this far-flung region, four general areas have been
indicated as offering good oil prospects:

(1) The Great Slave Lake Area.

(2) The Fort Norman Area.

(3) Arctic Red River and Mackenzie River Delta Area.

(4) The Peel and Porcupine Rivers Area.

Seepages are recorded in the Great Slave, Fort Norman,
and Peel River areas, but none has yet been discovered in
Arctic Red River and Porcupine River areas.

O_O ee :

Great Slave Lake Area—The eastern end of Great
Slave Lake is underlain by Precambrian rocks, but west of
Slave River and the North Arm of the lake the Precambrian
formations are overlain by Silurian and Devonian Paleozoic
rocks that dip to the west. Farther west, in Horn Mountains
north of Fort Providence, Cretaceous strata overlie the
Paleozoic. Throughout the Great Slave Lake area the
sediments are either flatlying or gently folded. The
best sections of Middle and Upper Devonian rocks are
found along Hay River, which enters Great Slave Lake from
the southwest. The Middle Devonian limestone beds,
which contain the most promising potential oil-productive
strata, are very porous and give large seepages of oil at
their outcrops along the northwest shore of Great Slave
Lake.

Wells have been drilled at only two localities in the
Great Slave Lake area, and at neither was oil in commercial
quantity discovered. One locality was on the north shore
at Windy Point, and the other on Hay River, 15 miles
south of the lake. One of these wells drilled at the latter
locality encountered a strong artesian flow of water from
Middle Devonian beds. As there is no obvious head for
this water, the suggestion is that it may Owe its pressure
to gas on the crest of the structure.

Fort Norman Area.—In the Mackenzie basin and mount-
ains of the Fort Norman area, strata comprising beds of
Silurian, Middle and Upper Devonian, Cretaceous, and
Eocene age are known to be present. Seepages of oil are
common in the Devonian beds, and all production so far
obtained comes from strata of this age.

The Upper Devonian in the Fort Norman area consists
of about 1,800 feet of dark shales of the Fort Creek formation,
overlain by 800 to 2,000 feet of the Bosworth formation of
sandstoneand shales. Incertainareas, large lenses of limestone
and sand occur in the Fort Creek shales. The overlying
Bosworth formation is predominantly sandstone and shale,
and many of its sand beds are favourable as oil reservoirs.
The Cretaceous rocks consist largely of non-marine strata
with coal. The marine shales of the Fort Creek formation
offer excellent cover for the retention of oil under favourable
structura conditions.

The valley of Mackenzie River in the Fort Norman area
is a large syncline about 20 miles wide between the Norman
Range east of the river and the Carcajou Mountains to
the west. The anticlinal fold of the Norman Range is
faulted and eroded, and exposes Silurian strata at its core.
Successively higher formations of Devonian age outcrop
to the west, and the eroded edges of the Bosworth formation
provide the abundant oil seepages common in the area.
West of the river, the Upper Devonian Bosworth formation
is covered by Cretaceous sandstone and shale. Norman
basin may be considered to extend along Mackenzie River
from 100 miles south of Fort Norman to the Mackenzie
Ramparts, a total distance of not less than 250 miles.

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