Its eastern boundary here, as well-as north of Great Slave
Lake, is the border of the Precambrian Shield. Its western
boundary is the Mackenzie Mountains and the escarpment
of the Peel Plateau. It embraces the basin of the western
end of Great Slave Lake and continues thence down the
valley of Mackenzie River to the Arctic Coast. A re-
entrant extends up the valley of the Liard as far as Fort
Liard. North of Nahanni River, the lowland is divided
into two parts by the long, narrow ridge of Franklin
Mountains, the highest summit of which, Mount Clark,
has an elevation of 4,733 feet. The Franklin Range is
sometimes referred to as an outlier of the Mackenzie
Mountains. Other elevations are those of Horn, Grizzly
Bear, Scented Grass, and Reindeer Mountains.

Rocks of Ordovician and Silurian age form the base
of the Paleozoic section along the eastern edge of the low-
land belt where the sediments overlap the Precambrian
basement. These rocks form an escarpment that probably
continues northward to Great Bear Lake: Silurian strata
are also exposed in the low mountain ranges near the mouth
of the North Nahanni River, in Bear Mountain near Fort
Norman, and on Great Bear River. Shale beds believed

to be of Silurian age are also exposed at the base of Mount
Kindle east of Wrigley.

The Silurian strata are overlain unconformably by
beds of Middle Devonian age. These and the succeeding
Upper Devonian beds form the surface rocks over the
greater part of the Mackenzie Lowlands.

Sandstones and shales of Cretaceous age cover con-
siderable areas. They outcrop on the Liard River, along
the Mackenzie River north of Dahadinni River, on Peel
River, and on the western shores of Great Bear Lake. At
the mouth of Bear River, a basin of partly consolidated
Tertiary sands and clay with lignite beds covers a large
area. The beds are lacustrine and of Eocene age.

In Pleistocene time, the region was covered by ice,

and deposits of glacial drift conceal the underlying rocks
over much of its area.

GEOLOGICAL Surveys

In the huge area of the North Pacific Region, covering
some 1,000,000 square miles, approximately 100,000 square
miles have been geologically mapped in some degree of
detail, but mostly by reconnaissance. In the remainder
of the region, only the main travelled routes have been

explored geologically, so that for the greater part of the
area information on the geology
meagre.

and mineral resources is

During the field seasons of 1944 and 1945, the Dominion
Department of Mines and Resources had e

parties and eight topographical survey parties working in

the Region. The work of these parties was directed

principally to the areas regarded as most promising for
oil developments.

ight geological

These surveys included the following:

A. geological reconnaissance of a belt 5 to 10 miles
wide along the Canol pipeline. In addition to potential
oil-bearing country, this road traverses areas favourable
to metallic mineral occurrences in the Yukon and the
adjacent part of the Northwest Territories.

A. geological reconnaissance in the area west of
Great Slave Lake. Oil seepages are known in this
locality, and the investigation had for its objective the
establishment of more complete information on strati-
graphy and structure.

A study of the stratigraphy and paleontology
of the Triassic formations between the Peace and
Liard Rivers in northeastern British Columbia to
establish standard sections for correlation with surface
formations as an aid to exploration for oil.

A similar study west of the foothills adjacent to
the Canadian National Railways line.

An extension of previous work in the Entrance area
of the Alberta foothills, seeking structures favourable
to the occurrence of oil.

Continuation of a geological reconnaissance in the
Takla, Manson Creek, and McConnell Creek areas of
north central British Columbia. These are localities
favourable to metallic mineral occurrences.

Topographical surveys in the Whitehorse and

. Dezadeash Lake districts of Yukon and adjacent parts of

British Columbia, and in the areas north of Entrance
and about the Wapiti River in Alberta.

Topographical surveys in the Mackenzie River
basin with the object of providing base maps for future

work in’ the development of the petroleum resources
of the district.

In addition to the work of the Department of Mines
and Resources, air surveys of vast areas in the North Pacific
Region were carried out by the Royal Canadian Air Force

under the direction of the Interdepartmental Committ

ee
on Air Surveys.

This air mapping will greatly assist and
expedite the investigation and development of the natural
resources of the Region.

Minera Deposits

Most metallic mineral deposits are related in origin to
intrusive rocks, and in the North Pacific area all the rocks
from Precambrian to Mesozoic time, and from the Pacific
Coast as far east as the eastward limit of intrusion, offer
promise of metallic mineral deposits. The large areas of
Paleozoic rocks east and northward, from the Rockies and
the Mackenzie Mountains, present the essentials for
potential oil and gas fields, and the Mesozoic rocks east

of the area cut by intrusions are favourable

for the occurrence
of coal, oil, and gas.

Mesozoic rocks also contain coal in

the large area affected by intrusive rocks. The Tertiary

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