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Geology of Arctic Canada: Encyclopedia Arctica Volume 1: Geology and Allied Subjects
Stefansson, Vilhjalmur, 1879-1962

Geology of Arctic Canada

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

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

EA-I. Wilson: Geology of Arctic Canada

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

EA-I. Wilson: Geology of Arctic Canada

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

EA-I. Wilson: Geology of Arctic Canada

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

EA-I. Wilson: Geology of Arctic Canada

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

EA-I. Wilson: Geology of Arctic Canada

(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

EA-I. Wilson: Geology of Arctic Canada

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,

EA-I. Wilson: Geology of Arctic Canada

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.

EA-I. Wilson: Geology of Arctic Canada

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

EA-I. Wilson: Geology of Arctic Ohio Canada

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,

EA-I. Wilson: Geology of Arctic Alaska Canada

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

EA-I. Wilson: Geology of Arctic Alaska Canada

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.

EA-I. Wilson: Geology of Arctic Alaska Canada

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

EA-I. Wilson: Geology of Arctic Alaska Canada

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

EA-I. Wilson: Geology of Arctic Alaska Canada

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.

EA-I. Wilson: Geology of Arctic Alaska Canada

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

EA-I. Wilson: Geology of Arctic Alaska Canada

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

EA-I. Wilson: Geology of Arctic Alaska Canada

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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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

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

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

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.

EA-I. Wilson: Geology of Arctic Canada

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
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