Unpaginated      |      Vol_I-0365                                                                                                                  
EA-I. (J. Tuzo Wilson)

GEOLOGY OF ARCTIC CANADA

       

CONTENTS

	Page
Introduction	1
The Major Geological Provinces	3
The Canadian Shield	6
Palezoic Outliers on the Canadian Shield	15
The Arctic Archipelago	19
The Arctic Coastal Plains and Interior Plains	30
The Cordilleran Region	32
Economic Geology	34
Bibliography	39

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EA-I. (J. Tuzo Wilson)

       

GEOLOGY OF ARCTIC CANADA

       

Introduction

        Most physical and biological phenomena change with latitude. For

example, polar climates and polar flora can be defined and readily dis–

tinguished from their tropical counterparts. In geology such a distinction

is to be observed only in the youngest rocks. There are at present no

general criteria known by which a majority of the rocks, fossils, and geo–

logical structures of polar regions can be identified and distinguished

from the geology of equatorial or temperate parts of the world. Although

some fossils have been found only in northern latitudes, it has not yet been

demonstrated that they are all peculiarly arctic in character. On the con–

trary, fossil evidence suggests that the polar regions have not always been

as cold as they are at present, while indications of former areas of glaciations

have been found in many parts of the world no longer cold. Too little is yet

known to explain these observations, but they suggest that the earth has

usually had a more uniformly distributed climate than at present, and that ice

ages such as the recent Pleistocene glaciation have been exceptional events.

        The cause of these periodic glaciations is not known. The more important

periods of glaciation, at least, have followed active mountain building, but

astronomic and atmospheric influence seem also to have been a factor in

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causing and controlling them.

        It has been suggested that the earth’s poles have migrated with

respect to its surface or that continents have drifted on the earth’s surface

and so moved with respect to the poles, but the paleontological grounds for

advancing these views are not conclusive. Physicists who have examined the

forces available in the earth to produce such movements are unanimous in

believing that they could not have occurred in Paleozoic and more recent times

to the extent postulated and required by some paleontological theories. They

consider that some other explanation not involving continental movements is

needed. It is quite probable, therefore, that since the time of their origin

the northern countries have been arranged about the pole in the same way that

they are today. Many aspects of this subject are still obscure and await

investigation, but this much is certain. No general characteristics are

known of the fossils and the materials of the earth by which the geology of

Arctic Canada can be differentiated from that of the rest of North America.

The geology of those regions will, therefore, be discussed as an arbitrarily

chosen part of that of the whole continent.

        Our lack of knowledge of the arctic regions makes it doubly desirable to

consider the geology thus, so that we can extrapolate from extensive studies

in the south to tie together isolated observations farther north.

        No one is familiar with the geology of all parts. The great areas re–

quiring examination and difficulties of travel have resulted in separate

groups of geologists working without much intercommunication, in the Yukon

Territory, in the Mackenzie River Basin, and in Labrador. The District of

Keewatin and the Arctic Islands have been studied only by occasional expeditions.

For the same reasons, the relationship between the geology of Greenland and

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that of adjoining parts of northern Canada is scarcely known at all, but the

geology of adjoining parts of Alaska and of Yukon Territory are reasonably

well correlated across the 141st meridian of west longitude which forms the

political boundary but follows no natural division.

        Among all these groups, working in different parts of the North American

Arctic, geological interpretations have differed, and it has been possible

for differences to be intensified where little has been studied and where

regional descriptions depend upon scanty observations. These differences of

opinion and gaps in our knowledge make summarization difficult, but the task

of generalization has been simplified by the general reports upon the state of

geological knowledge in several of these regions which have been prepared by

leading authorities and issued during the last few years. Excellent geological

maps of North America and of Canada have been published recently. No other as per author ltr 23 march 50

geological map of the Canadian Arctic as a whole has been published for many

years. The descriptive parts of this article are largely based upon those

papers which are listed at its close and also upon others listed in the

bibliographies which they contain. On the mainland most of the work has been

done by the Geological Survey of Canada, but information about the Arctic

Islands has been gathered by many exploring expeditions. In this paper, wome

theories not published in these descriptions are introduced in an endeavor to

interpret the history of this part of the earth.

       

The Major Geological Provinces

        Like all continents, North America can be considered to be made up of

three types of geological structures. These are exposed shields of disturbed

and ancient basement rocks, plains of generally flat-lying, younger rocks

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overlapping these shields, and ranges of relatively young mountains. In

North America, the arrangement of these elements is approximately symmetrical.

The center of the continent is occupied by the Canadian Shield of basement

rocks, which is a comple s x of pre-Cambrian rocks representing the eroded and ✓

leveled roots of former, vanished mountains. It forms a complete ring of

moderately uniform width right around Hudson Bay, for pre-Cambrian rocks form

the surface of practically all parts of the mainland lying north and east of the

Gulf of St. Lawrence, Lake Superior, Lake Winnipeg, and the Mackenzie Great

Lakes (Great Bear and Great Slave lakes), and also form most of Baffin Island

to the north.

        Around these pre-Cambrian rocks in another ring are the plains of the

covered shield. These are underlain by fairly flat-lying sedimentary rocks,

only a few thousands of feet , thick , resting upon basement rocks. This province ✓

includes the St. Lawrence River valley, the plains of the north-central United

States, the Prairie Provinces, and the Mackenzie River valley a large part

of the Arctic Archipelago is also included in this province, for these islands

are divided by only shallow arms of the sea.

        Sues included most of Greenland in the Canadian Shield, but Baffin Bay

is so much wider and deeper than any of the other waters spread upon the con–

tinent that it seems probable Greenland should be regarded as a separate

continental structure. In any case, our knowledge of those parts is very

limited due to great extent of the Greenland ice sheet and ignorance of

the geology of the pre-Cambrian rocks of the northeastern Canadian Arctic.

        Around the margin of the North American continent are younger mountain

ranges. The Cordilleran and Appalachian ranges of folded and faulted

sedimentary rocks are arranged in the pattern of an upright V. The Cordillera

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reach the Arctic in the Yukon and Alaska, but the Appalachians are cut off

by the sea on the north coast of Newfoundland. In the Arctic, two other

ranges of mountains disposed in the shape of an inverted V enclose the

northern part of the continent. In comparison with the Cordilleran and

Appalachian Mountains, these are neither so large and well known nor so

continuous, but they are by no means negligible. The mountains of Northern

Ellesmere Island, which form the northwest border facing the Arctic Sea,

reach altitudes of 11,000 feet. They extend into Axel Heiberg Island and

are perhaps continuous with those which cross North Greenland. According

to the view adopted in Canada, the other northern range forms the eastern

parts of Ellesmere Island and Devon Island, reaches altitudes of 10,000 feet

in Baffin Island, of which it forms the backbone, and continues down the

Labrador coast where the range is known as the Torngat Mountains. On the

other hand, if Suess’ view be followed, that Greenland is geologically part

of North America, the arctic part of the continent is still enclosed by

mountains, because another range, rising above 12,000 feet, forms the whole

eastern coast of Greenland. If this view be adopted, Baffin Bay and the

mountain range through Baffin Island and Labrador would have to be regarded

as disturbances within the Canadian Shield. In either case, the continent

may be said to be roughly in the shape of a great diamond of pre-Cambrian

rocks partly covered by later plains and faced on four sides by higher and

younger mountains of which the Western Cordillera are by far the greatest.

        This concentric regularity of the continent suggests that it was built

by simple, systematic, subcrustal forces, but this article must cut across

the divisions into shield, plains, and mountains, and describe only the arctic

parts of each. It will deal in turn with the northern parts of the Canadian Shield

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(excepting that part in Greenland), the Paleozoic outliers on the shield, the

Arctic Archipelago, the Canadian arctic coastal plains and Interior Plains,

and those parts of the Western Cordillera lying within the Yukon. The

economic geology of all parts will be treated last.

       

The Canadian Shield

        The Canadian Shield is one of the largest areas of exposed basement

rocks in the world. The southern and western parts have been reasonably

well covered by geological mapping, but the northern and eastern parts have

been examined only along the routes of reconnaissance traverses. Because of

the complexity of these rocks, mapping of rock types has greatly outstripped

interpretation even in those limited areas which have been well examined.

Important summaries of the present state of knowledge have been made by the

Geological Survey of Canada, and by Morley E. Wilson and H. C. Cooke. The

most recent attempts to interpret structure, using geophysical information,

have been made by J. E. Gill and J. T. Wilson.

        The annular shape of the Canadian Shield has already been mentioned.

Within it, there is further symmetry. The center, in Hudson Bay, is the

lowest part and toward it the surface slopes gently inward on all sides.

The height of land is generally near the outer margin of the shield. In

Baffin Island, mountains as high as 10,000 feet form the rim, while in the ✓

Torngat and Adirondack Mountains the margin is more than 5,000 feet high.

Other highlands occur north of the St. Lawrence River and Lake Superior,

around the eastern ends of the Mackenzie Great Lakes, along the Coppermine

River, beside Bathurst Inlet, on Boothi s a Pe l n insula, and near Wager Bay. ✓

Important valleys which cross the rim of the shield are those of the Nelson

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and Ottawa rivers and of Hudson Strait. No heights equal to those common

around the rim are reached anywhere in the interior nor around the shores

of Hudson and James bays. The shores around three sides of these bays are

among the most gently sloping to be found anywhere. Only on the east coast

are there any hills. These reach 1,500 feet near Richmond Gulf. There are

slightly higher hills inside the western entrance to Hudson Strait.

        It is true that Hudson Bay and the region around it were depressed in

recent times by ice loading which accentuated the basin shape, but the

land has already risen hundreds of feet since the ice melted. It is widely

supposed that this rise is still continuing and that Hudson Bay may eventually

be drained, but that is by no means certain. There appears to have been little

or no rise at Churchill since 1940 when an official and reliable tide gauge

was installed. Since the time of Tyrrell it has been the opinion of all

Canadian geologists who have examined the field evidence that no rise of the

land there has taken place in historical times. In any case, whether this

rise continues or not, there is abundant evidence that the central basin is

a feature of great antiquity. No future uplift great enough to destroy it has

been postulated. The previous existence of this basin in shown by the presser–

vation on the islands and around the shores of Hudson Bay of extensive deposits

of late pre-Cambrian, Paleozoic, and lacustrine Cretaceous deposits. There

appears to have been another smaller basin of deposition in the Foxe Basin.

        The nature of the contact between the shield and younger rocks which

surround it and lie upon it has not been the subject of close examination in

most places. In some areas the contact is an overlap, as it is north of Lake

Ontario, but in many other places the contact is faulted. In the interior

basin, this seems to be the case on Southampton Island, in Richmond Gulf,

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and south of James Bay. Around the outer margin, there are fault contacts

along the St. Lawrence and Ottawa rivers, on Boothi s a Peninsula, and perhaps ✓

in places along the Slave River. The isolated patches of Paleozoic rocks,

which are widespread over the shield and which will be described later, are

also generally infaulted on at least one side. There is no indication that

any of these post-Cambrian fau tl lt s are of great magnitude. It is not unusual ✓

for there to be normal faulting around the margins of sedimentary basins.

        A generalized description of the rocks of which the shield is composed

in the Arctic is almost impossible. The types are very variable and the

areas which have been examined are small. Some principles can, however, be

stated with fair certainty.

        The first of these is that the same geological processes operated in

pre-Cambrian times as have subsequently. There may have been gradual and

slight changes so that the conditions under which the earliest rocks were

laid down may have been a little different, but there is no evidence of pro–

found cataclysms nor of violent disturbances. On the contrary, at intervals

all over the shield there is evidence of the operation in these old rocks of

those geological processes of erosion, deposition, and glaciations which occur

today. There is no evidence of any original crust of the earth, nor much of

any unusual rocks except some anorthosite masses. There is no suggestion

that the temperature of the surface was not approximately the same as today.

For the past two thousand million years it seems to have been between the

freezing and boiling points of water at all times. These facts suggest that

the different appearance of most pre-Cambrian areas is not because conditions

then were different, but because the rocks are older and have been more deeply

eroded. The Archean type of rocks of the shield are the roots of vanished.

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mountains, not differing in any marked way except in elevation from the

rocks now exposed in the cores of the Cordilleran and the older Appalachian

Mountains.

        The second principle is that pre-Cambrian time was vastly long and that

events occurred during it as complex as those observed in the youngest rocks.

The record of these things is now obscured and foreshortened so that there

has been a tendency to oversimplify pre-Cambrian history.

        Geological evidence and radioactive age determinations both suggest that

pre-Cambrian time was much longer, probably at least three times as long, as

all subsequent time. When it is remembered that there have been two major

post-Cambrian orogenies in the Appalachian and Cordilleran parts of North

America respectively, it can be appreciated that there is likely to be

evidence of several important periods of mountain building preserved in the

pre-Cambrian rocks.

        The danger of supposing that pre-Cambrian time is divided into only two

great divisions is thus obvious. It has been shown that no universal or even

general disturbance nor stratigraphic break marks the close of pre-Cambrian

time. Leith has similarly pointed out t r hat no universal break exists between

the Archean and Proterozoic (or Algonkian) types or rocks; that properly

these are not divisions of time, but rather that they should be used to refer

to two types of rock assemblage, the one profoundly disturbed and extensively

intruded by granites, the other only gently folded and containing only limited

bodies of intrusives. Without doubt, the less altered Proterozoic rocks are

often the younger, but that cannot be stated as a general proposition.

        This distinction is most important in the Arctic. Although it is convenient

to consider the gently dipping Proterozoic type of rocks of the northwestern

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shield, of the Belcher Islands, and of the Labrador Trough together with

those which they resemble near Lakes Superior and Ruron, there are no grounds

known why they should all be considered to be of the same age nor even why

they should all have to be considered late pre-Cambrian in age. Unfortunately,

this assumption has often been made.

        Because there is a lack of fossils in pre-Cambrian rocks, the few radio–

active age determinations will have to be supplemented by a proper understanding

of the structure of the shield in order to arrive at even a rough time scale.

It is considered that the Archean type of rocks are the cores or roots of old

mountain ranges. Fortunately, mountains are built in definite belts and

during periods of time limited to a few [ ?] hundreds of millions of years.

Thus, the coast ranges of the Cordilleran have been built during the past 100

million years while the Appalachian Mountains were folded and intruded by

igneous rocks during the Paleozoic period from 200 to 600 million years ago.

It is considered that shields can be divided into similar belts which can be

roughly dated. In the south and northwest the pattern is emerging, elsewhere

it has yet to be discovered.

        A third principle which appears to be true is that these mountain belts

are concentrically arranged about continental centers or nuclei. The arrange–

ment is such that mountain belts generally parallel the margin of the continent

with younger rocks toward the outside.

        The only exception known to this arrangement parallel to the margin of

the continent is the great belt of sedimentary, volcanic, and metamorphic

rocks which strike southwest from Chesterfield and Churchill to the margin of

the prairie overlap south of Lake Athabaska. So completely does this great

belt of rocks appear to violate the rule of arrangement which prevails elsewhere,

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that it has been suggested that the mountains they represent were formed like

the Urals, between two old continental masses and the shield started as two

centers, one north of Lake Superior and the other north of Great Slave Lake.

Greenland likely had a third center and others may be found.

        A fourth principle, advanced by Lawson, is that the continents have

grown by the formation of these marginal mountain ranges. This is the reason

why the provinces become younger toward the margins of continents.

        These principles are not yet universally agreed upon and there is a lack

of knowledge of pre-Cambrian geology in the Arctic. It is, therefore, not yet

possible to subdivide the pre-Cambrian of the Canadian Arctic into belts. One

can only give brief notes upon the more outstanding local features of pre-Cambrian

rocks of the Arctic.

        The greater part of Baffin Island and the eastern portions of Devon and

Ellesmere Islands consist of gneisses and granites containing bands of schists,

but the rocks of the south coast of Baffin Island include much crystalline

limestone, the general assemblage resembling in petrology and in foliated

structure that of the Grenville province of the St. Lawrence river valley.

In northwestern Baffin Island and in the islands to the north, flat-lying

sedimentary beds overlie the granites and gneisses. The lowest of these beds

are frequently unfossiliferous sandstones which have sometimes been referred

to the late pre-Cambrian and sometimes to the Paleozoic, because the next

overlying beds are frequently conformable and contain fossils of Ordovician

and Silurian age.

        At Arctic Bay, close to Admiralty Inlet, these flat-lying unfossiliferous

beds are cut by large basic dikes having a general east-west strike.

        The basal complex of Labrador and Ungava consists mainly of gneiss and

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granite, commonly intermixed in different proportions to form migmatites.

Rose and there are scattered, clearly recognizable remnants of metamorphosed

sedimentary rocks, conglomerates, quartzites, limestones, and schists. Meta–

morphosed remains of volcanic tuffs, greenstones, and amphibolites are also

found. It is clear that these sedimentary and volcanic rocks were formerly

widely spread over that part of the earth’s surface now forming Labrador,

but that they have been [ ?] extensively transformed into crystalline schists

and gneisses and removed by erosion.

        Associated with these gneisses in a broad band extending inland from the

Labrador coast and from the north shore of the St. Lawrence River are large

masses of anorthosite with associated gabbro and other basic rocks. The

origin and history of these unusual masses of basic felspar rocks is not yet

understood.

        Resting upon the basement complex and locally younger than it are several

series of much less altered sedimentary rocks. How these are to be correlated

with one another and with rocks in other regions is as yet unknown.

        At Ramah, near the northern end of the Labrador coast, black slates,

quartzites, and impure dolomites rest conformably upon the gneisses and upon

basic dikes. Farther south on the coast, similar rocks with a large proportion

of interbedded volcanic rocks are known as the Kaumajet series. Other flat-lying

or gently folded sedimentary rocks, chiefly cross-bedded quartzites, crop out

at intervals around Lake Melville and northwest from it up Naskaupi River as

far as Lake Mishikamau.

        In the interior of Labrador and Ungava, a belt of younger rocks, known as

the Labrador Trough, extends up to 40 miles wide and at least 350 miles long

from the head q w aters of the Hamilton River to the west side of Ungava Bay. ✓

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These rocks, which bear a general lithological resemblance to Huronian rocks of

Lake Superior district, contain extensive beds of iron formation. They have

been thrust-faulted and closely folded with axes in a northwest-southeast

direction. To the west, these beds lie unconformably upon gneisses of Grenville

type, while to the east, they are succeeded by a belt of predominantly volcanic

rocks some 25 miles wide, which, in turn, gives way to granite-gneisses. The

volcanic rocks are also faulted but the nature of their contact with the

gneisses to the east is still uncertain, although some reconnaissance wor l k ✓

suggests that the gneisses are thrust over the volcanic rocks.

        On Richmond Gulf, two gently folded formations are separated by a slight

unconformity. The lower formation consists of arkose and sandstone with some

basic lavas, while the upper consists of dolomite with algal structures, basic

flows, sandstone, slate, and iron formation. These formations are cut by

intrusions of diabase. It has been suggested that these beds have all been

preserved by subsidence faulting closely parallel with the curved coast of

Hudson Bay. On the Belcher Islands, 8,000 feet of beds similar to those in

the upper series at Richmond Gulf have been preserved in beds folded in a

regular and striking manner. Inliers of diabase and other rocks similar to

these crop out through Paleozoic limestones along Winisk and Sutton rivers in

northern Ontario. Other flat-lying rocks of generally similar character have

been preserved by infaulting around Lake Mistassini and Lake Chibougamau in

Quebec.

        In the western Arctic, the pre-Cambrian succession is better known and more

complete. The oldest known rocks are the Yellowknife series which consist

mainly of altered graywackes with basic lavas. They crop out over extensive

areas north of Great Slave Lake. They have been correlated with similar rocks

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at Indin Lake, Point Lake, and near Lake Athabaska. They are separated by

faulting and unconformity from another younger series of rocks, the Snare

group, which is also intensely folded and altered. The Snare group, which

extends northwest from Indin Lake to Great Bear Lake, contains ores of radio–

active elements which have been shown to be 1,400 million years old. Both are

cut and surrounded by great areas of granite and gneiss which is known in

some places to be of more than one age. In the East Arm of Great Slave Lake,

the Great Slave group is well developed and resembles the Snare group. Both

groups consist of thick beds of quartzite, argillite, and dolomite which bear

algal structures. South of Great Soave Lake, there are thick beds of arkose

and conglomerate called the Nonacho series. They are gently folded, but are

cut by some granites. On the north shore of Lake Athabaska, similar rocks

are known as the Beaverlodge group.

        Along the Arctic coast in the vicinity of Bathurst Inlet are the Epworth

dolomite, Kanaryak formation, and Goulburn quartzite. Along the coast these

are flat-lying beds cut by granites in at least one place; along Bathurst

Inlet they are folded parallel with the inlet up which they extend but their

southern limit has not been mapped.

        Farther west and possibly of the same age as the Goulburn quartzite, or

perhaps younger, the Coppermine series with an estimated thickness of up to

48,000 feet dips gently north along the arctic coast of Coronation Gulf and

Amundsen Gulf. The lower rocks are chiefly basaltic lava flows separated by

thin beds of conglomerate, while the middle portion is characterized by red

and brown sandstones passing upward into red sandstone, shale, limestone, and

dolomite cut by diabase sills.

        Other gently dipping trap and sedimentary rocks f ro or m Kent Peninsula and ✓

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parts of both the southern and northern coasts of Victoria Island. It has

been suggested by O’Neill that all these gently dipping rocks are of

similar late pre-Cambrian age and form a gigantic syncline dipping east

toward Boothia Peninsula.

        Underlying these sedimentary rocks along the arctic coast and in most

places in the interior of the Northwest Territories which have been examined,

the oldest rocks are granite and gneiss.

        In the district of Keewatin, a belt of old, much-folded and altered

sedimentary and volcanic rocks of Archean type extend from Chesteffield Inlet

southwest to the eastern end of Lake Athabaska. Concerning this belt little

has been published, but it is known to contain thick beds of quartzite inter–

bedded with basic lavas. These rocks are cut by granites. Overlying these

old rocks along the shores of Lake Dubawnt and Thelon River are flat-lying

white and red sandstones. The boundaries of these areas of younger rocks are

not yet well established, but they are generally similar to the rocks cropping

out over a large area south of Lake Athabaska.

       

Palezoic O utliers on the Canadian Shield.

        The center of the Canadian Shield is now occupied by Hudson Bay, but

around its shores are preserved areas of Paleozoic rocks which show that the

depression is of great antiquity and not solely a result of incomplete recovery

from isostatic sinking under a Pleistocene ice sheet. The two main areas in

which these rocks are now exposed are in the Hudson Bay lowland, which extends

along the southwest coasts of Hudson and James bays, and on several islands in

the northern part of Hudson Bay.

        Large areas of Paleozoic rocks are also preserved around the shores of

Foxe Basin. Akpatok Island in Ungava Bay consists entirely of Paleozoic strata.

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Small outliers have been found at many scattered places across the Canadian

Shield.

        The Hudson Bay lowland borders James Bay on the south and west and

extends along Hudson Bay as far west as Churchill. It is a low, nearly

featureless plain, with a seaward slope of less than four feet per mile which

continues out under James Bay, forming an intertidal zone as much as several

miles wide. The plain is covered with drift and muskeg so that rock outcrops

are mainly along river banks and occasionally on the coast.

        South of James Bay, the contact of the Paleozoic limestones with the

older pre-Cambrian rocks may be faulted, for the margin of the basin rises

in an escarpment down which the several tributaries of the Moose River descend

in a series of falls and rapids.

        According to the Geological Survey of Canada, the oldest sedimentary rocks

are the Nelson River and Shamattawa limestone formations, together 150 feet

thick. These have been correlated with Red River and Ston e y Mountain forma–

tions of the Lake Winnipeg region. Formerly, they were regarded as Trenton

(Middle Ordovician), but they are now classed as Richmond (Upper Ordovician),

although some Trenton fossils recur. This has led to confusion. The Lower

and Middle (Niagaran) Silurian epochs are represented by about 300 feet of

limestones. These are overlaid by about the same thickness of Devonian rocks

divided into five formations representing all three epochs of that period.

They have been correlated most closely with formations of New York State.

        In two small areas there are lacustrine deposits of clay, sand, and

lignite, probably of Lower Cretaceous age.

        Diagonally across Hudson Bay are other important areas of Paleozoic rocks.

Southampton Island may be divided into two parts, of which the larger southwestern

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portion is a lowland underlain by Upper Ordovician (Richmond) and Middle

Silurian (Niagaran) rocks. These are separated, probably by faulting, from

the northeast plateau of granite and gneiss. According to Manning, one patch

of limestone has been preserved near Seahorse Point on this plateau at a

height of several hundred feet above the main limestone plain to the southwest.

        In the entrance of Hudson Strait, southeast of Southampton Island, are

Coats of and Mansel Islands, each a low flat plain underlain by limestone, ✓

probably similar in age to that on Southampton Island. A ridge of pre-Cambrian

gneiss crosses the northern end of Coats Island.

        The shores of Foxe Channel, which leads north from Hudson Bay, are all of

pre-Cambrian age, but to the north much of the coast line of Foxe Basin con–

sists of Paleozoic rocks.

        In the Putnam Highland, which lies west of Amadjuak Lake and north of

Foxe Peninsula on Baffin Island, Gould has described 600 feet of unfossiliferous

shale which rests upon pre-Cambrian gneiss and schists intruded by some granite.

The shale is overlain by 100 feet of limestone containing a rich fauna. Both

Hussey and Foerste have stated that this is typical Arctic Richmond. Soper

also made collections on Baffin Island which have been examined by Alice Wilson.

She agrees with the correlation with Red River (Richmond) formation, but has

found some Collingwood (Middle Ordovician) fossils as well.

        On the east shore of Amadjuak Lake and again on Silliman Fossil Mount, a

small outlier near the head of Frobisher Bay, the same Arctic Richmond fauna

has been found.

        On the north coast of Foxe Basin are several large islands and peninsulas

underlain by Paleozoic rocks, while a large part of Melville Peninsula and of

the adjacent islands are underlain by shaly limestone from which Richmond faunas

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have been identified.

        Akpatok island is an isolated island in Ungava Bay. It is 550 square

miles in extent and cliffed all around its shores. A large collection of

the fauna was made by Cox and carefully studied by him and others. It is

considered to be Arctic Richmond corresponding to Nelson River and

Shamattawa formations of Manitoba. Some of the trilobites have some relation

to those of the Utica formation of Middle Ordovician epoch.

        In addition to these main outliers, there are a large number of small

ones. The best known of these are the Ordovician and Silurian outliers

which extend up the Ottawa River valley as far as Lake Nipissing and Lake

Timiskaming where Richmond and Niag a ran limestones are preserved. There ✓

are also four or five small occurrences in Quebec, all of Ordovician age.

These are at Lake St. John and at Arvida on the Saguenay River, at Lake

Waswanipi p at the headwaters of the Broadbak River and at Lake Manikouagan

on the river of the same name. There are several reports of loose blocks

with Collingwood fauna from near Cape Chidley at the north end of Labrador.

        The most isolated occurrence was reported by J. B. Tyrrell who collected

Richmond fossils from Limestone Island on Lake Nicholson near Lake Dubawnt,

in the heart of the Northwest Territories west of Hudson Bay.

        It is now possible to summarize the Paleozoic and subsequent history of

the Canadian Shield.

        Outliers of Paleozoic age are widespread over the Canadian Shield. These

are all flat-lying and generally downfaulted. Only a few formations are

represented. Of these, Arctic Richmond (Upper Ordovician) corresponding to

the Nelson River and Shamattawa formations of the Hudson Bay lowland and to

the Red River and Stony Mountain formations of Lake Winnipeg region is the

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most widespread. Great confusion has been caused in the literature by the

fact that these formations were at one time correlated with the Middle

Ordovician (Trenton) of eastern Canada. Other formations found in several

places are the Middle Ordovician (Collingwood) and Middle Silurian (Niag a ran). ✓

Devonian and lacustrine Cretaceous formations have been found only near

James Bay. The fact that flat-lying remnants of a very few formations have

been found so widely and that the great majority of epochs and periods are

not represented at all plainly suggests that the Canadian Shield was a low

plain throughout this great interval, that it was exposed in the Cambrian

period and most of the time subsequently, and that it was only occasionally

and for short intervals covered by shallow seas. At some time since the

Devonian, possibly at the time of the Appalachian revolution, the shield

underwent slight normal faulting.

        The Canadian Shield thus generally formed an effective barrier to the

migration of marine life between the Arctic and the rest of North America.

It is therefore, not surprising that A a rctic faunas can more often be ✓

correlated with those from western North America or from Europe than they can

with those of the eastern and central United States and southeastern Canada.

       

The Arctic Archipelago

        The Canadian Arctic Islands form an unique assemblage of large islands

separated by comparatively narrow channels and fjords whose pattern is in

some parts almost rectilinear and elsewhere gently curved. Nowhere is there

another group of islands so peculiarly divided. No other archipelago except

Oceania contains so many large islands. Indeed, it is seldom realized how

huge these islands are. Baffin Island, which is nearly 1,000 miles long,

would reach from Ontario to Florida. Three of the islands are each larger

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than England. In view of their size, inaccessibility, and the present lack

of economic incentive, it is not surprising that their interiors are largely

unexplored, but from a scientific viewpoint it is unfortunate that the whole

interesting area is so little known. Although the pattern suggests that the

islands may be partly divided by faulting, it would be interesting to know

how this could have occurred without causing more disturbance tha t n is evident ✓

on the existing maps.

        The archipelago forms a great flat basin of covered shield, mountainous

in the north but open to the Arctic Sea on the west and resting to the south

and east upon Archean rocks of the mainland and of Baffin, Devon, and wsouth–

east Ellesmere Islands. The prominent rocks in the basin are pre-Cambrian

quartzites, Ordovician, Silurian, and Carboniferous or Permian limestones with

lesser outcrops of other Paleozoic, Triassic, and Tertiary sedimentary rocks.

        The general geology of the islands of the Arctic Archipelago has been

described and mapped on a small scale by the Geological Survey of Canada,

but the detailed geology is known in only a very few small areas. Systematic

mapping of the region has hardly begun. Only a general account of the geology

can be given and that may require modification by subsequent more detailed

exploration.

        The chief cause of this uncertainty is that, although systematic explora–

tion of the northern islands may be said to have been begun by Parry in 1820,

the first extensive geological work to be done was that by Schei between

1898 and 1902. Few expeditions have been accompanied by geologists, and

fossils brought back on many other expeditions may have often been picked up loose or,

if collected from cliffs, the specimens from different horizons may have been

mixed. Some of the older collections were described by contemporary geologists

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who used names no longer current; others were not described until as much

as a century after they had been collected. The importance of the Canadian

Shield as a barrier was not at first understood by the paleontologists who

described the collections. They did not in all cases realize that the fauna

of the Arctic Archipelago was thus isolated from the developed differently

from the faunal assemblages to which they were accustomed. It will thus be

understood that the limited knowledge available has been reduced in value

by an element of confusion and uncertainty.

        The formations exposed in the Arctic Archipelago are successively younger

from the edge of the Canadian Shield toward the northwest. The formations

also thicken in that directions, so that the most complete sections have been

measured on Ellesmere Island, where the Paleozoic strata alone have a thickness

of at least 10,000 feet. As these rocks in the northern islands have been

studied by competent geologists, it will be convenient to describe them first.

        The Mountains of Northern Ellesmere Island . In the extreme northern

parts of Greenland and Ellesmere Island there are high mountains, believed to

reach 11,000 feet in Ellesmere Island and 6,000 feet in Greenland. These

mountains are divided by Kennedy and Robeson Channels, which have a minimum

width of about 13 miles, and by several large fjords which penetrate the

north coast of Greenland. Parts of them have been called the Challenger,

United States, and British Empire ranges, and other names by different

explores, but the extent of and divisions between these ranges is not yet

known. From the air, the northern part of Ellesmere Island appears as a

complex of peaks deeply [ ?] dissected by glacial erosion and still to a large

extent engulfed by ice which fills the valleys. The mountains continue across

Nansen Sound into Axel Heiberg Island. On the east and west coasts of that

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island are ranges of mountains rising to 7,000 feet. Between them is an

unbroken icecap which is about the same elevation and from which glaciers

flow to fill the valleys. Here the mountains end, for the Ringnes Islands

are not over 1,000 feet in altitude.

        Very few of the peaks on any these islands have been climbed or

even seen except from the air. The area constitutes one of the least known

and most fascinating regions in North America.

        The very limited studies that have been made show that these mountains

are composed of schists, slates, sandstones and limestones lying in folds

with axes striking northeast and southwest. Granite pebbles have been picked

up by both the expeditions that have explored the north coast of Ellesmere

Island, but the age of the intrusive and of the sedimentary rocks in the

mountains is unknown.

        Sch i u chert suggested that in Proterozoic time a geosynclines, which he ✓

named Franklinian, formed striking northeast across these islands and

northern Greenland. He believed that its sediments were derived from an

active rising land mass, Peary Land, which at that time lay to the north.

Teichert, however, has suggested that the Canadian Shield was the source of

the sediments. Very recently, Eardley has again postulated that the whole

basin of the Arctic Sea was filled by a land mass, Ancient Arctica, which

started to sink only in Carboniferous time. The geological arguments he

advances are not convincing and may have some other explanation. He

suggests no physical reason nor mechanism for depressing a vast area by at

least 15,000 feet while the adjacent Canadian Shield remained quite stable.

The proposal runs counter to all seismic, isostatic, and other physical

evidence. In fact, from a geophysical viewpoint it seems hardly possible that

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the whole area of the arctic basin sank as recently as he has suggested,

but it is probable that there have been extensive alterations of shore

lines within the limits of the shallow continental seas. These may be

regarded as sufficient to answer the geological arguments he has put forward.

        There is no doubt, however, that throughout Paleozoic and Mesozoic times

there was in those parts a geosynclinal or marginal sea in which a great

thickness of deposits was laid down. No section has been measured within

the area of folded mountains but south of them along both coasts of Ellesmere

Island excellent exposures have been studied, especially by Schei and Bentham.

        Ellesmere and Axel Heiberg Islands . Pre-Cambrian gneiss and schist

cut by granite, syenite, and gabbro are exposed along the coast of the

southeastern quarter of Ellesmere Island and have also been observed at

the head of Bay Fjord in the center of the west coast. Along the south coast

these rocks are characterized by a high content of hypersthene.

        Overlying the gneiss at Bach Peninsula in the center of the east coast

are 400 feet of red and white unfossiliferous sandstones resting upon a flat

erosion surface. These rocks resemble the Thule sandstone in Greenland, are

cut by diabase sills, and pass upward conformably into about 3,000 feet of

shales and limestones containing Middle or Upper Cambrian and Lower Ordovician

fossils.

        North of Bache Peninsula and on Bay and Vendome Fjords on the west coast

and near the center of the south coast are exposures containing the well-known

Arctic Richmond fauna which is widespread through the Canadian Arctic. This

has been correlated with the Red River fauna of Manitoba and the Cape Cal b h oun —

of east west Greenland, but, confusingly enough, was generally called Trenton until

1920.

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        Both in Kane Basin on the east coast of Ellesmere and on Goose Fjord

in the southwest, dark shale and limestone containing the Lissatrypa phoca

fauna follow. These beds have been referred both to the Silurian and to

the Devonian, but Foorste places them in the basal Devonian in spite of a

survival of a great percentage of Silurian fossils. This is a northern fauna

which is found in a belt from north Greenland as far south as Boothia

Peninsula, but which is nowhere found together with the Niag a ran (Middle ✓

Silurian) fauna which only reaches as far north as Southampton and King

William Islands.

        In southwestern Ellesmere Island these are succeeded by 950 feet of

unfossiliferous shale and sandstone which pass upward into 1,600 feet of

richly fossiliferous shale and limestone containing Lower, Middle, and Upper

Devonian formations. These pass upward into 2,000 feet of sandstone contain–

ing Upper Devonian plant remains. Similar Devonian beds crop out along the

fjords of the west coast and on Devon Island. Holtedahl has described Schei’s

collections from these areas. Unfortunately, the succeeding beds were nowhere

examined, but on Bear Cape in southwest Ellesmere Island collections were made

from a limestone containing a rich fauna corresponding closely to that called

Upper Carboniferous in Russia, although it would be classed as Permian in

America. This is another formation widespread in the Arctic. It also occurs

in northeastern El l esmere Island, at the north end of Axel Heiberg Island, and ✓

in Peary Land in n N orth Greenland, as well as widely in the Parry Islands. ✓

        The chief known area of Mesozoic rocks in the Canadian Arctic is on both

shores of Eureka Sound, which separates Axel Heiberg from Ellesmere Island.

These shales contain both marine and plant fossils, both probably of Middle

Triassic age and related to that of Sp ti it sbergen. In the same area are local ✓

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deposits of thick light-colored sandstone, shale, and layers of lignite of

Miocene age.

        Between the deposition of these two formations very numerous diabase

dikes and sills were intruded. They are probably of the same age as other

diabase intrusives on the eastern and southern coasts of Ellesmere Island

and on Ellef Ringnes Island.

        The basic intrusives accompanied mountain building of late Mesozoic

age, for the Triassic beds were steeply folded before the undisturbed

Cenozoic beds were deposited. It is possible, but not certain, that this

was the orogeny that formed the mountains of northern Ellesmere Island.

        Some indefinite evidence of an earlier period of folding has been found

in three areas. About 100 miles south of Eureka Sound , in the southwestern ✓

part of Ellesmere Island, folded Ordovician and Silurian rocks crop out along

the north coast of Baumann Fjord. On the south side of the fjord are com–

paratively undisturbed Devonian and Carboniferous limestones. Bentham ✓

believed, bu r t could not prove, that these overlie the earlier strata on the

opposite side of Baumann Fjord, indicating a Caledonian or late Silurian

disturbance in the area lying immediately to the southeast of the Mesozoic

ranges.

        The interior of Ellesmere Island has never been examined, but on its

northeast corner, 300 miles diagonally across the island, are the folded and

unfossiliferous Cape Rawson beds which Bentham and Koch believed to be a

continuation of the Silurian beds in Baumann Fjord. Fielden had found these

Cape Rawson beds to pass beneath flat-lying Carboniferous strata, but did

not observe the contact, which may be an overthrust. Koch supported his

correlation by identifying with the Cape Rawson beds other folded and metamorphosed

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rocks which occur across Kennedy Channel in Greenland and from which he

reported doubtful Silurian Fossils. Schei, on the other hand, believed the

Cape Rawson beds to be a continuation of the Triassic beds he studied in

Eureka Sound, and that, therefore, no evidence had yet been found for any

but post-Triassic folding and mountain building, but he did not deny that

evidence for earlier orogenies might yet be found. In any case, the Plaeozoic

strata toward the southeastern part of the island are only gently folded, but

probably underwent faulting during the Tertiary period.

        The Parry Islands. These islands form the central part of the archipelago.

The largest of them are Prince Patrick, Melville, and Bathurst Islands, all

of which are fairly flat islands with broken or cliffed shore lines up to

1,000 feet high. The greater part of them, of the small islands around them,

and of the adjacent peninsulas or Cornwallis and Devon Islands are underlain

by flat-lying rocks of probable Permian age. These consist of 1,000 feet of

shales overlain by the “sandstone series” and “limestone series” of

greater thickness. White sandstones containing thick seems of coal and both

fossil plants and invertebrates crop out on the south coast of Melville Island

and over most of Bathurst Island. The younger “limestone series” has been

found on Grinnell Peninsula of Devon Island and on the north coasts of Bathurst

and Melville Islands.

        The fossils in both series have been ascribed to the Carboniferous and

resemble and Upper Carboniferous of Russia, but are generally regarded as more

closely allied to those of Permian age in the United States. Volcanic rocks

of probably the same age occur in southeastern Bathurst Island.

        Mesozoic marine fossils have been found on Prince Patrick and Bathurst

Islands, and fossil wood of Miocene age on w s outhwestern Prince Patrick Island. ✓

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        A few fossil ammonites have been brought from the Ringnes Islands and

from those discovered by Stefansson. These fossils and the similar topog–

raphy make it appear likely that they are underlain my Mesozoic and perhaps

Permian rocks similar to those on Axel Heiberg and the Parry Islands.

        Devon, Cornwallis, and Somerset Islands. The eastern part of Devon

Island is underlain by pre-Cambrian granite and gneiss rising above 3,000

feet and covered by a small icecap. The pre-Cambrian surface dips toward

the western part of the island, where it is overlain by a succession of

younger beds which form magnificent cliffs of gradually decreasing height.

On the north coast, Cambrian, Arctic Richmond (Upper Silurian), and Devonian

formations have been definitely identified, while Grinnel Peninsula which

extends to the northwest is underlain by flat-lying Permian of the “sandstone

series.” On the south coast, the cliffs have generally been described as

Silurian in age, but a large part of them contain the Lissatrypa phoca fauna

whose age is disputed and may be basal Devonian. Shaly limestones containing

the same fauna probably underlie most of Cornwallis Island except the northern

tip.

        A ridge of pre-Cambrian gneiss extends north from Boothai Peninsula along

the west coast of Somerest Island, but the greater part is underlain by a

plateau of flat-lying Ordovician and Silurian or Devonian limestones which

form cliffs up to 1,000 feet high. Fossils of the Arctic Richmond and Lissatrypa

phoca faunas have been found around the north, east and south coasts.

        Boothia Peninsula, Prince of Wales Island, and King William Island. A

rugged and unexplored ridge of pre-Cambrian rocks forms the greater part of

Boothia Peninsula and extends northward to underlie the west shore of Somerset

Island and the east coast of Prince of Wales Island. The southern arctic

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islands are thus divided into two basins of Paleozoic rocks, but too little

is known of the rocks which they contain to be able to state whether there

are significant differences between them. Along the east coast of Boothia

Peninsula, Richmond (Upper Ordovician), and Lissatrypa phoca (Silurian or

Devonian) faunas have been found. Inland, granite cliffs rise up to 1,500

feet above these limestones, suggesting that the ridge has been upfaulted.

On the west coast of Boothia Peninsula fossils from the same two formations

as on the east coast have been identified. According to Foerste this is

the most southern occurrence of the Lissatryp o a phoca fauna. ✓

        To the southeast, the Simpson Peninsula is also underlain by undifferen–

tiated Paleozoic limestone which has also been described as being faulted

against granite gneiss.

        Very little is known of the geology of Prince of Wales Island. Except

along the east coast where pre-Cambrian rocks occur, it is low and underlain

by limestone from which Silurian fossils of unknown period have been reported.

        King William is an extremely flat, low-lying island covered with a

multitude of lakes. At the western end of it, fossils of Upper Ordovician

age have been collected by Washburn as well as earlier explorers. Middle

Silurian (Niag a ran) fossils were collected by Rasmussen along the south coast. ✓

        Victoria Island . Only the south coast and western part of this great

island have yet been explored. The geology is chiefly known from the reports

of O’N d e ill and Washburn, although the island has also been examined by ✓

several parties of prospectors.

        O’Neill suggested that the rocks of the Coppermine series of late

pre-Cambrian age formed a great syncline whose parallel limbs extended across

northern and southern Victoria Island and met on the mainland west of Dolphin

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and Union Strait. Certainly in all these areas there are gently dipping

sedimentary series of great thickness, cut by diabase sills and containing

basalt flows. The basal strata are predominantly reddish sandstone and

conglomerate, but are more calcareous toward the top, where dolomite beds

contain the digitate forms of stromatolites (gymnosolen) which have been

described by Cloud.

        Between the north and south limbs of this easterly plunging syncline,

and especially on the west coast of Wollaston Peninsula, around Prince Albert

Sound, and on Read, Sutton, and Liston Islands in Dolphin and Union Strait

there are Upper Ordovician and possibly Silurian limestones. There may be

limestones of the same ages at places along the south and southeastern coasts.

        Sedimentary rocks containing coal have been reported from the northwest

coast of Victoria Island on the shore of Prince of Wales Sound. The presence

of coal indicates a post-Silurian age, probably Permian, since strata of that

age containing coal are known to occur on Banks and Melville Islands nearby.

The strata may, however, be in part Tertiary in age.

        The Princess Royal Islands, between Victoria and Banks Islands, have been

classed as Silurian or Devonian on the basis of a single fossil collected by

M’Clure and preserved. Washburn favors a Devonian age on account of descriptions

of coal and petrified wood on the islands, but admits that there is no certainty

that these latter came from the same horizon as the fossil.

        Banks Island . The stratigraphy of Banks Island is very little known except

that limestone, sandstone, and coal of probable Permian age occur along the

north coast where they were described by Alexander Armstrong in 1857.

        Stefansson found coal a little south of the center of the island which

from his description is almost certainly of Tertiary age. Other loose pieces

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of coal which may be of any post-Silurian age have been found at several

localities. As a result of assigning these occurrences to different ages,

the various authorities have produced maps which show a wider disagreement

in the geology of Banks Island than for any area of similar size in the

Canadian Arctic.

        From the striking cliffs at Nelson Head, in the extreme south, the land

rises steeply to 3,000 feet or more to form the highest land in a very large

region. On lithological grounds these rocks have been assigned to the

Coppermine series, but Washburn has indicated the uncertainty of this correlation.

       

The Arctic Coastal Plains and Interior Plains

        The wide plain which forms the arctic coast of Alaska narrows toward the

International Boundary, where it is only about ten miles wide between the

Richardson Mountains and the sea. It immediately broadens in Canada and

merges up the Mackenzie River valley with the Interior Plains of North America.

The western boundary of this province is the border of the Canadian Shield.

This extends from Darnley Bay on the arctic coast southward through Great

Bear and Great Slave lakes.

        The only truly arctic part of the Interior Plains province is a narrow

strip along the coast, in which outcrops are scarce and which has been little

studied. A large part of it is covered by alluvial deposits of the Mackenzie

River delta.

        The boundary with the Canadian Shield is very poorly exposed between the

arctic coast and Great Bear Lake, where its position has best been determined

by Bateman who made a reconnaissance survey for that purpose. From Great Bear

to Great Slave Lake the contact of flat-lying Ordovician shale and dolomite with

underlying granite-gneiss is well exposed along a chain of lakes. Farther west,

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Silurian rocks have been found north of Great Slave Lake and underlie the

Mackenzie lowlands. They have been best studied in the vicinity of the oil

field at Norman Wells, there 1,500 feet of hard, dolomitic limestone inter–

bedded with anhydrite and shale have been included in the Ronning group.

This is overlain by 400 feet of brecciated dolomite of uncertain age. These

are succeeded by Middle Devonian strata.

        No strata of Lower Devonian age have been recognized in the Mackenzie

valley region, but the Middle Devonian is represented by as much as 3 2 ,000 feet ✓

of limestone and shale which is succeeded by Upper Devonian deposits of shale,

limestone, and sandstone. These beds thicken to as much as 3,000 feet in the

northern part of the valley, where shale predominates. The Devonian strata

thus form an important part of the section in the Mackenzie River valley and

occupy a wide belt along the entire course of the Mackenzie River except where

they are overlain by Cretaceous beds or thick alluvium.

        No beds of any age from Carboniferous to Jurassic have been found in the

Mackenzie River valley, but it is not known whether this is due to erosion or

whether beds of these ages were never deposited. In any case, Cretaceous

strata rest directly upon Devonian beds in many places and overlap onto the

edge of the Canadian Shield north of Great Bear Lake, which they surround on

all shores except the eastern. During the Lower Cretaceous epoch the southern

part of the Eastern Cordillera was a land mass, but north of Athabaska River

to the arctic marine shale of the Sans Sault group, nearly 4,000 feet thick,

rests on an eroded surface of Devonian rocks. In the vicinity of Norman Wells,

the Upper Cretaceous is 2,500 feet thick and has been divided into three formations,

which, in ascending order, are the Slater River, Little Bear, and East Fork. The

Slater River is formation, which rests upon the Lower Cretaceous Sans Sault

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group, is composed of black fissile shale with a few thin beds of bentonite.

The Little Bear formation consists of sandstone, shale, and lignite of alter–

nating brackish and fresh-water origin, while the East Fork formation consists

of gray marine shale. Farther north, extensive deposits of Cretaceous age

which have not been studied in detail emerge from either side of the Mackenzie

delta to fringe the arctic coast. Recent work by Bostook suggests that they

underlie only a narrow strip of the north Yukon coast, and that the Paleozoic

rocks of the Richardson Mountains approach the cost more closely than is

shown on existing maps.

        Resting unconformably on the Upper Cretaceous in a small area around

Fort Norman are shale, soft sandstone, and conglomerate of Paleocene age.

These beds attain a maximum thickness of about 1,600 feet and contain seams

of coal up to ten feet thick. Other small areas of Tertiary strata occur on

the coast of Darnley Bay and in the valleys of the Porcupine and Red rivers.

        The western border of the Interior Plains province is marked by the

rise of the foothills of the Cordilleran province.

       

The Cordilleran Region .

        The eastern part of this province is the only one that enters the arctic

regions and there it is divided into the Richardson, Mackenzie, and Franklin

ranges which are the northern counterparts of the Rocky Mountains. Only the

northern end of the Richardson Mountains reaches the true Arctic.

        The Richardson Mountains extend south from the narrow coastal plain

opposite Herchel Island, near the Alaskan boundary, as a nearly straight

range up to 5,000 feet in height, more than 40 miles wide, and nearly 200 miles

long. They truncate the east-west ranges and structures that prevail across

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the northern part of Alaska, but the geology of the hinterland between them

in northern Yukon has scarcely been examined. Indeed, most of the structure

of the Richardson Mountains has been interpreted only from a study of air

photographs by Bostook.

        Southeast of the Richardson Mountains is the Peel Plateau, a triangular

plain rising in a scarp several hundred feet above the Mackenzie valley. It

is crossed by the entrenched valleys of the Peel and Arctic Red rivers. South

of this plateau stretch the Mackenzie Mountains in a broad crescent rising

abruptly from the Interior Plains. They consist of well-stratified ridges of

sedimentary rocks, without intrusives and are reported to rise as high as

10,000 feet. Across the Mackenzie River, and between it and Great Bear Lake,

is the narrow range of the Franklin Mountains which rise at Fort Good Hope and

for 400 miles to the south parallel to the river and never more than 30 miles

wide. The highest peaks reach 5,000 feet.

        All these ranges were folded at the same time out of the same geosynclinal

basin so that it will be convenient to treat their stratigraphy together. The

few igneous rocks yet found in the Eastern Cordillera are confined to the

ranges farther south.

        Unfossil if erous strata thought to be of late pre-Cambrian age have been ✓

found in the Franklin and Mackenzie Mountains. These are overlain by shale

and sandstone at least 200 feet thick in which Middle Cambrian fossils have

been found. It is doubtful if Lower and Upper Cambrian are represented in

these ranges.

        Limestone of Upper Ordovician age have been found in the Mackenzie

Mountains, containing a Richmond fauna similar to that so widespread in all

Arctic Canada. Silurian beds are well exposed in the Franklin and Mackenzie

Mountains, forming the chief part of the former.

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        No Lower Devonian strata have been identified in any part of the Rocky

Mountain region, but up to 2,000 feet of limestone and shale of Middle

Devonian age and 3,000 feet of Upper Devonian shale, limestone, and sandstone

form an important part of the section in the Mackenzie valley and in the

Mackenzie Mountains.

        Carboniferous and Permian rocks occur along the Liard River and Alaska

Highway but have not been found in the Mackenzie valley region. Triassic

rocks also thin out and are not found far north of the Liard River, but they

do reappear on the Alaska boundary between the Porcupine River and the arctic

coast. Jurassic strata have not been found between the Alaska Highway and

the Richardson Mountains, but marine Jurassic beds have been found in that

range and along the Firth River near the Alaska boundary. Cretaceous rocks

have not been found in the Mackenzie Mountains, but, according to the Geological

Survey of Canada, occur on the Peel Plateau on the banks of the Arctic Red and

Peel rivers, in Richardson Mountains, and on Porcupine River to the west,

but have not yet been studied in detail.

        In the early part of the Tertiary period and perhaps earlier in the

north, the thick deposits of the Rocky Mountain geosyncline were folded and

large blocks wee thrust eastward. The Mackenzie and Franklin Mountains were

subjected to broad folding with subordinate thrust faulting which produced

their arcuate shape. No detailed work has been done in the Richardson

Mountains, but they are reported to be characterized by straight north–

trending folds.

       

Economic Geology

        The question of the possibility of economic development of the arctic

regions is frequently raised. As far as mineral and oil production is concerned,

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EA-I. Wilson: Geology of Arctic Canada

the answer is no longer problematical, for in Canada several mining areas

and one oil field are already in economic production in the subarctic close

to the border of the arctic regions and it is only a matter of time until

some of the mineral resources known to occur in the Arctic are brought into

production also. There has been a rapid northward spread of mining activity

which has temporarily been halted by the increased costs incidental to

operations beyond the tree line. Every year some prospecting is done and

some claims are held within the Arctic. The most northern of the Canadian

subarctic mining areas and the prospects of developing camps beyond them

will be discussed from west to east.

        Until the recent discoveries of oil near Edmonton (see articles on

bituminous sands of northern Alberta), Canada’s second largest oil field was

the one at Norman Wells, on the Mackenzie River about 90 miles south fo of the ✓

Arctic Circle. Since it was discovered in 1920 by drilling in the vicinity

of oil seeps, this field has supplied oil to a local refinery to serve the

requirements of the district. In 1942, development was accelerated by the

Alaska Highway and Canol projects which resulted in the drilling of about

60 productive wells and the construction of a pipe line to Whitehorse, where

a refinery was supplied with 3,000 barrels of oil from Norman Wells daily for

a short period. As a result, the production rose to 1,200,000 barrels of

crude oil in 1944, but with the end of the war and the abanoning of the Canol

Project in 1945 it was reduced again to serve only local consumption in the

Mackenzie River valley. (See “Development of Oil Fields in Canada’s North.)

        The Norman Wells oil occurs in a reef limestone of Upper Devonian age at

a depth of from 1,000 to 2,000 feet. Petroliferous shales and oil seepages

are widespread in the district so there is a probability that other fields

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EA-I. Wilson: Geology of Arctic Canada

are hidden, but so far neither geological nor geophysical methods have been

able to locate any of them. Farther north, the arctic coastal plain, although

narrow in Canada, offers possibilities, for it is underlain by Cretaceous

strata similar to those in which oil has been discovered near Point Barrow

in Alaska.

        On the east shore of Great Bear Lake, a few miles south of the Arctic

Circle, is the Eldorado mine at Port Radium. Before the war, the value of

production had reached one million dollars a year, mostly in radium, of which

the mine was one of two major world sources. In 1944, this property was

taken over by the Canadian Government and for some years its output and

activities have been secret. The mine has since been stated to be a major

source of uranium for atomic energy. At the time it was discovered in 1930,

several other prospects for uranium, silver, and other metals were reported

in the same general area but no others were developed.

        Northeast of Great Bear Lake, along the Coppermine River and Bathurst

Inlet, is a great thickness of late pre-Cambrian sandstone with interbedded

lava flows and intruded sills and dikes of diabase and gabbro, all dipping

gently north. At many places these beds contain native copper and chalcocite,

which has attracted prospectors at intervals since 1771. Large blocks of

claims have been held at times. Between 1944 and 1946, extensive geological

and drilling exploration was carried out at many places in the Coppermine area

but it was found that the deposits could not yet be profitably developed.

        On the north shore of Great Slave Lake, and hence some distance from the

Arctic, is Yellowknife, now in process of becoming one of the largest gold–

mining camps in Canada. Although gold was first discovered in the vicinity

in 1898, production did not begin until 1938 and the chief development has

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EA-I. Wilson: Geology of Arctic Canada

taken place since 1945. The country rocks are lavas and tuffs, ranging in

composition from rhyolitic to basaltic, interbedded and overlain with

sediments which are chiefly impure quartzite. The rocks of the Yellowknife

group are isoclinally folded and have been intruded and metamorphosed by

granite batholiths. They are cut by two important sets of later faults.

The important ore bodies are in wide shear zones, striking north-northeast

and up to 150 feet wide. Northeast of Yellowknife gold has been discovered

near Courageous, Mackey, and Point Lakes and also near the headwaters of the

Back River at Began Lake. Besides gold, certain rare elements occur in

pegmatites in the same region. From specimens found by natives it is sus–

pected that other pegmatites occur near the west end of Contwoyto Lake.

        In the years 1928 to 1930, the District of Keewatin that lies west of

Hudson Bay was the scene of active and widespread prospecting by four companies.

Although the only production that resulted was from a pocket a gold on the

coast of Term Point, interest has never entirely ceased, and a wide belt of

Archean sedimentary and volcanic rocks, which extends for five hundred miles

southwest from Rankin Inlet, has been prospected form time to time since.

Several blocks of claims, including a nickel deposit at Rankin Inlet, have

been held for many years. Another belt of volcanics and iron formation at

Baker Lake, also known for many years, was again prospected in 1946.

        In Labrador, the main interest has been in the subarctic where very

large deposits of high-grade iron ore are now being developed in a belt of

late pre-Cambrian sedimentary rocks. This belt extends north to the west

of Ungava Bay where it is being prospected, but the richest ore bodies reported

to date have been from the southern part of the belt and there has been no

announcement of plans to develop properties in Ungava. Other sedimentary

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EA-I. Wilson: Geology of Arctic Canada

and volcanic belts in Ungava have been prospected. There has been interest

in lead and iron deposits at Richmond Gulf, while iron deposits on the

Belcher Islands have been examined without success.

        On Baffin Island, Frobisher Bay was the scene of the first prospecting

in Canada, in 1576-1578, but the reputed gold was found to be worthless

pyrite and there has been no production from any part of Baffin Island except

for insignificant amounts of graphite and mice. In 1945, prospectors examined

a number of conspicuous gossans in southern Baffin Island, which had been

seen during the war, but could only find rusted gneisses. The area generally

held to be most interesting is in the vicinity of Arctic Bay, where minerali–

zation was reported by Bernier and where claims were staked in 1937. Lignite

is mined for local use in Tertiary beds at Pond Inlet.

        In the other Arctic Islands little prospecting has been done. Oil seeps

have been reported on Melville Island and coal on many islands. Concerning

the possibility of obtaining coal for local use on the islands, Mackay has

stated that estimates must be regarded simply as wild guesses due to the meager

data pertaining to the various occurrences. Most of these occurrences are of

float coal, but in a number of the islands several such occurrences have been

reported so that it appears fairly safe to assume that the coal is of local

origin and probably underlies a considerable area.

        It will thus be appreciated that the geological study of the Canadian

Arctic has scarcely begun. Since the war, improved means of transport and the

establishment of permanent meteorological stations has greatly facilitated

access to these regions. The important economic developments at Norman Wells,

Eldorado, Yellowknife, and in Labrador, although all in the subarctic, have

stimulated prospecting and geological surveying within the Arctic.

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---

BIBLIOGRAPHY

1. Bentham, A. : “Structure and glaciers of southern Ellesmere Island,”

Geogr.J . vol.97, no.1, pp.36-50, 1941.

2. ✓ Canada. Geological Survey. Geological Map of the Dominion of Canada . 1945.

Map 820 A,

3. Eardley, A.J. “Ancient Arctica,” J.Geol . vol.56, no.8, pp.409-37, 1948.

4. Foerste, A.F. “The Ordovician and Silurian of America, arctic and sub-arctic

regions,” Denison Univ.Sci.Lab. J . vol.24, pp.27-80, 1929.

5. Geological Society of America. Geological Map of North America . 1946.

✓ 6. Holtedahl, Olaf. Summary of Geological Results . Kristiania, Brøgger, 1917.

Report of the Second Norwegian Arctic Ex e p edition in the “Fram ”,

7. Kindle, E.M. “Geology of the arctic archipelago and the interior plains of

Canada,” Ruedemann, Rudolf, and Balk, Robert, eds. Geology of North

America . Berlin, Borntraeger, 1939, vol.1, pp.176-231.

8. ✓ Retty, J.A., and Moss, A.E. “Iron ore deposits of central Labrador and New

Quebec,” Geol.Soc.Amer. Bull . Vol.58, p.1220, 1947. (Ab w s tract only)

9. Ruedemann, Rudolf, and Balk, Robert, eds. Geology of North America . Berlin,

Borntraeger, 1939. Vol.1. Geologie der Erde .

10. Tanner, V. Outline of the Geography, Life and Customs of Newfoundland-

Labrador. Helsinki, Helsingfors, 1944. Acta Geogr ., Helsingf. Vol.8, no.1.

11. Washburn, A.L. Reconnaissance Geology of Portions of Victoria Island and

Adjacent Regions, Arctic Canada . Baltimore, Md., 1947. Geol.Soc.Amer.

Mem . 22.

12. Wilson, M.E. “The Canadian shield, ” Ruedemann, Rudolf, and Balk, Robert, eds.

Geology of North America . Berlin, Borntraeger, 1939, vol.1, pp.232-311.

13. Young, G.A. Geology and Economic Minerals of Canada . 3d ed. Ottawa, Acland,

1947. Canada. Geological Survey. Economic Geology Series no.1.

       

J. Tuzo Wilson