bluuebunny/crossref_metadata_2025 huggingface dataset:
The polar continent-ocean transition in Canada (Corridor G)
Authors: Sweeney J. F. , Mayr U. , Sobczak L. W. , Balkwill H. R.
Published: April 2015

The Canadian Arctic transect corridor (Corridor G) extends across a wide range of geologic settings. In the south at Somerset Island, Archean crystalline rocks of the craton are exposed (Fig. 1). Northward across Cornwallis and Devon Islands the crystalline rocks are covered by Proterozoic and early Paleozoic platform deposits that were uplifted, eroded, and deformed in Silurian through Early Carboniferous time. Overlying these rocks between Devon and Ellef Ringnes Islands are late Paleozoic and Mesozoic strata of the Sverdrup Basin. These strata were locally deformed by evaporite diapirism and repeated episodes of mafic igneous intrusion and, east of Corridor G, were regionally deformed in latest Cretaceous and Paleogene time. Northwest of Ellef Ringnes Island the corridor traverses the latest Cretaceous and younger clastic terrace wedge that covers the continental margin of the Canada Basin. The corridor terminates at abyssal depths over the continental rise.

The corridor was selected to incorporate deep crustal seismic results between Cornwallis and northern Ellef Ringnes Islands (Sander and Overton, 1965; Hobson and Overton, 1967) and offshore refraction and reflection work along the east coast of Ellef Ringnes Island (Sobczak, 1982; Sobczak and Overton, 1984). Phanerozoic strata are almost completely represented along the corridor, and reflection seismic data (courtesy of Panarctic Oils Ltd., Calgary) locate stratigraphic horizons at several points. Borehole data are available for Cornwallis, Bathurst, Amund Ringnes, and Ellef Ringnes Islands, and there is regional coverage by gravity (Sobczak, 1978) and aeromagnetic (Coles and others, 1976) data, including detailed measurements in the Sverdrup Basin
Rifted continental margins of North America
Authors: Sawyer Dale S.
Published: April 2015

During the late 1970s, the study of rifted margins was changed fundamentally by the recognition that simple models of thinning of continental lithosphere could account for many features of the subsidence observed on rifted or passive continental margins (McKenzie, 1978). The 1980s have produced at least three major new foci of research in the study of such margins and continental rifting in general. These new directions have emerged partly as a result of new data acquisition, primarily deep penetration seismic reflection profiling and complementary long offset seismic reflection-refraction experiments on rifted margins worldwide, and partly as a result of the application of land geologic observations of continental rifts to the study of margins.

The first of these new directions was the recognition of the importance of low-angle normal faulting in continental rifting. This avenue of research has changed our expectations of the large-scale patterns of rifting and rifted margin formation. We had come to expect that most rifts should be symmetric and that, upon plate reconstruction, conjugate rifted margins would also show symmetry at the time of initiation of sea-floor spreading. A number of investigators (Wernicke, 1981Wernicke, 1985; Lister and others, 1986) observed asymmetry in the shallow structures in continental rifts, and extended this idea to the whole lithosphere scale. The new model, usually referred to as the simple shear or delamination model, concentrates shearing along narrow zones at low angle to the surface and through the continental lithosphere. Most of the strain during continental extension takes place within this
Transects of the ancient and modern continental margins of eastern Canada
Authors: Haworth Richard T. , Keen Charlotte E. , Williams Harold
Published: April 2015

The continental margin transect program evolved through a desire to define the specific characteristics of North America’s modern continental margins and to compare the modern margins with Paleozoic examples, now found within the continent. Thus, the features of modern margins can be used to locate and elucidate the structures of ancient analogues. Conversely, the exposed rocks of ancient margins provide an insight into the evolution and deep structures of modern examples. Ocean-continental transitions, rifting mechanisms, development of sedimentary basins, processes of continental breakup, and ancestral controls are all features that warrant comparison between modern and ancient examples.

The Atlantic coast has the best-known passive margin of North America. Inboard of it is the Appalachian Mountain chain, which records a clear history of late Precambrian rifting and the passive development of a Paleozoic continental margin. Transects across both these modern and ancient examples provide information on scale and detail that is useful for comparisons.

The modern continental margin of eastern Canada (Fig. 1a, 1b) has a wider variety of ages and styles than that of its eastern United States counterpart. Segments of the margin southeast of Nova Scotia and east of Labrador are typical of rifted margins, though of different ages. Between them lies the tortuous segments of the northern and eastern Grand Banks where rifting and subsidence occurred over a broad area of the continental shelf. In contrast, the southern boundary of the Grand Banks is a transform segment. Rocks of the Appalachian Paleozoic margin are best preserved and exposed
Proterozoic rocks east and southeast of the Grenville front
Authors: Chiarenzelli J. R. , Drake A. A. , Goldsmith Richard , Hall L. M. , Hinze W. J. , Isachsen Y. W. , Lidiak E. G. , McLelland James , Mosher Sharon , Ratcliffe N. M. , Secor D. T. , Whitney P. R.
Published: April 2015

This chapter describes the Grenville orogen as it is preserved in areas of outcrop as well as in the subsurface in the United States, Late Proterozoic continental rifting that fragmented that orogen, and Precambrian rocks within terranes accreted to the rifted eastern and southern margins of Laurentia (earliest Paleozoic North America). The accretion of terranes to the eastern and southern margins of Laurentia formed the Paleozoic Appalachian (Caledonide)-Ouachita orogen. Outliers of the Grenville orogen, variously deformed by Paleozoic orogenies, crop out within the western part of the Appalachian orogen.

Although protoliths as old as Archean have been identified along the northwestern margin of the Grenville orogen in Canada, as far as we know, no rocks in the areas covered by this chapter are older than Middle Proterozoic. Some rocks, however, indicate ties to older source areas. Quartzites from the Adirondack Lowlands contain detrital zircons with minimum ages of 1.65 Ga, 1.8 Ga, and 1.95 Ga (McLelland and others, 1988a). Recent work by Dunning and Cousineau (1990) and Olszewski and others (1990) on rocks of the Chain Lakes block, Maine-Quebec, and correlatives to the north in the Canadian Appalachians has shown that some zircons, possibly detrital, in diamic-tite are as old as 2.8 Ga. Sinha and Bartholomew (1984) report a discordia intercept of 1.87 ± 0.2 Ga for zircons, probably detrital, from layered gneiss of the Blue Ridge Grenvillian outlier in Virginia. Zartman and Hermes (1987) report a Late Archean inheritance in zircon from Permian granites in the southeastern New England Avalonian terrane; they attribute this to the under-plating of the Avalonian microplate by Archean crustal components, possibly of Africa, in the late Paleozoic during the collision of Gondwanaland with Avalonia.
Middle and Late Proterozoic stratified rocks of the western U.S. Cordillera, Colorado Plateau, and Basin and Range province
Authors: Christie-Blick Nicholas , Devlin William J. , Elston Donald P. , Horodyski Robert J. , Levy Marjorie , Miller Julia M. G. , Pearson Robert C. , Prave Anthony , Stewart John H. , Winston Don , Wright Lauren A. , Wrucke Chester T.
Published: April 2015

The distribution of Middle and Late Proterozoic sedimentary and metasedimentary cover that lies unconformably on Early Proterozoic and Archean crystalline basement has been known for decades, but recent work, employing techniques of paleomagnetic correlation, sedimentology, sequence stratigraphy, and analysis of tectonic subsidence has led to modifications of some long-accepted correlations and tectonic models. Within the context of both older classical studies and this new work, the stratigraphy, correlation, tectonic setting, fossil content, and mineral potential of Middle and Late Proterozoic rocks of parts of the Rocky Mountain, Colorado Plateau, and Basin and Range provinces of the United States are discussed.

A problem common to interpretation of all Proterozoic strata is a widespread lack of fossil control on age and paleoecology, which makes correlations inherently uncertain and interpretation of depositional environments more difficult. We present current hypotheses about these topics and stress the uncertainty of some of our conclusions. The apparent polar wander path for the North American craton, as derived from the Middle and Late Proterozoic sedimentary cover, is central to our modifications of stratigraphie correlation, especially of Middle Proterozoic rocks.

The reader is asked to view the work and summaries presented here in the light of ongoing scientific debate about strata that are chronically stubborn in yielding information. The authors of sections of this chapter include both those who have performed classical studies, which are the foundation of our present understanding, and younger geologists who have been busy refining and modifying early interpretations, using different methods of study. The treatment in this chapter is therefore variable depending on which generation of investigators is speaking.
Geological Exploration of the Interior Plains
Authors: Stott D.F. , Aitken J.D.
Published: April 2015

Geological exploration has greatly influenced the development of western Canada, particularly the growth of the petroleum and natural gas, coal, and mineral industries. During the late nineteenth century when railroads were being built across the plains, settlers were encouraged by geological reports on the favorable agricultural prospects and the availability of water and fuels. The prosperity of the prairie provinces, based on their rich natural resources, would not have been achieved without the determination, enterprise, and knowledge of dedicated explorers.

This abbreviated account outlines the history of exploration and contributions of some of the notable individuals, particularly during the early years. The more recent history involves many more people, and it is not possible to acknowledge each and every one. Additional details on recent investigations may be found in the following chapters.

This subchapter has been prepared from a variety of sources in addition to original reports. It draws on a history of the Geological Survey of Canada by Zaslow (1975) and accounts of the development of the petroleum industry in western Canada by Gray (1970), de Mille (1970), Gould (1976), and a group of authors whose papers appear in Hilborn (1968).
Carboniferous
Authors: Richards B.C. , Bamber E.W. , Higgins A.C. , Utting J.
Published: April 2015

The Carboniferous System in Western Canada Basin (Fig. 4E.1-4E.3) is a thick succesion of strata deposited on the downwarped and downfaulted western margin of the ancestral North American plate, the central to western cratonic platform, and southern Yukon Fold Belt. This succession, representing the upper Kaskaskia sequenceand lower Absaroka sequence of Sloss (1963), comprises two main lithofacies assemblages. The lower assemblage is basinal shale and generally thickens southwestward or basinward (see Fig. 4 E . 9 - 4 E . 1 3) . Upward and northeastward, it passe into an upper assemblage of platform and ramp carbonates (Fig. 4E.4, 4E.5, 4E.9-4E.13) and sandstone-dominated siliciclastic facies, deposited in deep-water slope to continental settings. Both assemblages consist of numerous formations, some separated by regional disconformities. Subaerial erosion during the Late Carboniferous, Permian, and subsequent periods removed large parts of the succession, particularly in the Interior Plains, the region west of the Rocky Mountain Front Ranges, and the Cordillera between southwestern District of Mackenzie and northern Yukon Territory. Where the Carboniferous remains, it is generally unconformably overlain byeither Permian or Mesozoic strata.

Carboniferous formations are preserved in twomain regions. The southern one, which includes much of the eastern Cordillera andsouthern to western Interior Plains, extends from southwestern Manitoba to southwestern District of Mackenzie. The northern area includes the eastern Cordillera ofnorthern Yukon Territory and northwestern District of Mackenzie (Fig. 4E.1). Betweenthese regions, erosional remnants are present in the Mackenzie and Selwyn Mountains of east-central Yukon and west-central District of Mackenzie.
Permian
Authors: Henderson C.M. , Bamber E.W. , Richards B.C. , Higgins A.C. , McGugan A.
Published: April 2015

Permian rocks are preserved throughout most of the eastern Cordillera and locally, in the Peace River-Liard River area, on the Interior Platform (Fig. 4F.1, 4F.2, 4F.3). They are absent from the remainder of the Interior Platform and from most of the Mackenzie Mountains through truncation at several disconformities beneath Mesozoic strata.

Permian sediments were deposited mainly along the margin of the North American plate in a Permian depositional basin, here named Ishbel Trough, extending from the 49th parallel to the Ancestral Aklavik Arch in northern Yukon Territory. The trough occupies approximately the same position as the Carboniferous Prophet Trough (Richards et al., Subchapter 4E in this volume). In the Peace River-Liard River area, Permian sediments were also deposited on the western cratonic platform. The western margin of Ishbel Trough has not been identified. It (Fig. 4F.2, 4F.3) may have been in the area presently occupied by Cariboo Terrane (Struik and Orchard, 1985; Struik, 1986), which lacks Permian strata and may have been partly subaerially exposed during the Permian Period. A marginal basin to the west of Cariboo Terrane (Barkerville Subterrane of Kootenay Terrane; Monger and Price, 1979) contains a remnant of Permian strata (Sugar Limestone). The eastern margin of Ishbel Trough was a broad hinge-line along the western margin of the cratonic platform. In northeastern British Columbia and southwestern District of Mackenzie the hinge coincided with a zone of normal faulting, but generally the position of the eastern trough margin is unclear, because of eastward truncation of Permian strata (Fig. 4F.2, 4F.3).
Metallic Deposits
Authors: Aitken J.D. , Stott D.F.
Published: April 2015

The main metallic mineral deposits, with the important exception of Pine Point, lie within the eastern Cordillera and most are not being produced currently. Ferrous deposits of sedimentary origin and placer gold, both of low commercial interest at present, occur within the Plains. The metallic mineral deposits are outlined only briefly; additional detail may be found in the companion volumes on “Geology of the Cordilleran Orogen in Canada” (Gabrielse and Yorath, 1991) and “Mineral Deposits of Canada” (Geology of Canada, no. 8, Thorpe and Eckstrand, in prep.).
Hudson Platform – Geology
Authors: Norris A.W.
Published: April 2015

The Phanerozoic rocks of Moose River Basin are separated from those of Hudson Bay Basin by a northeast-trending Precambrian basement high, the Cape Henrietta Maria Arch (Fig. 8.1; see also Fig. 7.1). Because of the close similarity of facies and faunas, both basins were almost certainly connected with the Williston, Michigan, and Appalachian basins to the south during various intervals of Paleozoic time. The character of Ordovician and Silurian outliers on the Canadian Shield (Caley and Liberty, 1957), at Clearwater Lake (Kranck and Sinclair, 1963), Waswanipi (Clark and Blake, 1952), Lake Timiskaming (Hume, 1925), Mattawa, Lake Nippissing, and others, tends to support this hypothesis.

The northern boundary of Hudson Bay Basin is Bell Arch, trending northwestward through Southampton Island and bordering Foxe Basin of the southeastern Arctic Platform (see Fig. 7.1). The Phanerozoic rocks of Hudson Platform are separated from Williston and Elk Point basins to the southwest by Precambrian rocks of Severn Arch. To the south, Fraserdale Arch separates Moose River Basin from St. Lawrence Platform and Michigan Basin.

A basin concept for the offshore regions of Hudson Bay, inferred from sea-magnetometer profiles, was firmly established by Hood (1964). On the basis of refraction seismic data, Hobson (1964a, b) confirmed a basin of major proportions beneath Hudson Bay. Seismic profiles suggest that about 2000 m of Phanerozoioc strata are present in Hudson Bay Basin, and 600 to 800 m in the deeper parts of Moose River Basin.

Two structural provinces of the Canadian Shield, Superior and Churchill, border and
Hudson Platform – Economic Geology
Authors: Sanford B.V. , Norris A.W. , Cameron A.R
Published: April 2015

Hudson Platform underlies an area of 971 250 km2, more than half of which is covered by the waters of Hudson Bay, James Bay, Hudson Strait, and Foxe Basin. the region has potential for a variety of economic commodities, including petroleum and natural gas, oil shale, lignite, lead and zinc, and industrial minerals such as salt, gypsum, and limestone.

The principal emphasis over the years has been placed on exploration for oil and gas, first in the onshore areas of Moose River Basin, and in more recent years in the onshore and offshore regions of Hudson Bay Basin. Lignite deposits that have long been known to occur along the extreme southern margins of Moose River Basin have also been investigated from time to time for about a century, but have not been exploited commercially. Promising industrial mineral deposits including salt, gypsum, clay, sand, and limestone are known in widely separated parts of the platform, but have remained undeveloped owing to their great distance from densely populated regions of the country.
Introduction to Interior Platform, Western Basins, and Eastern Cordillera
Authors: Stott D.F. , Aitken J.D.
Published: April 2015

The Interior Platform, underlain by Phanerozoic sedimentary rocks, is the northwestern part of the North American Craton, the stable interior region of the continent (Fig. 2A.1; see also Fig. 1.1). Essentially flat-lying rocks of the Interior Platform extend into the eastern Cordillera where they are thrust-faulted and folded (see Fig. 5.5, in pocket), but have undergone little or no metamorphism nor plutonism during the orogenic phases. This area of undeformed and deformed sedimentary rock commonly is called the Western Canada Basin. The Interior Platform is linked to Michigan Basin and St. Lawrence Platform of southeastern Canada through the central U.S.A. and merges with Arctic Platform in the north. It is separated from Hudson Platform by a broad expanse of the Canadian Shield.

The area of nearly horizontal bedrock, forming the Interior Plains physiographic province, comprises plains and plateaux covered by a thick mantle of glacial drift. It is a region of grassland, forest, and tundra, some 2 000 000 km2 in area, that embraces parts of the prairie provinces of Manitoba, Saskatchewan, and Alberta, the northeast corner of British Columbia, and much of the western District of Mackenzie, Northwest Territories. In the southern region, clastic, carbonate, and evaporite strata of Paleozoic age rest on a basement of Precambrian crystalline rocks. The Paleozoic sediments are overlain by a relatively thick blanket of Mesozoic and Tertiary clastic rocks. The southern part of Interior Platform is the main oil-producing region of western Canada; it has been extensively drilled and its geology is well
Geomorphic Regions
Authors: Dawes P.R. , Christie R.L.
Published: April 2015

The geomorphic regions of the Canadian Arctic Archipelago1, one of the great archipelagos of the world, and of northern Greenland are described and illustrated in this chapter. Also included in the description are two large peninsulas, Melville and Boothia, that extend from mainland North America northward into the Arctic Islands. The land forms of this region are controlled, to some extent, by the lithology and structure of the bedrock, and therefore the geomorphic subdivisions distinguished here (Fig. 3.1) correspond fairly closely to the stratigraphic-structural provinces delineated in Chapter 4 (Fig. 4.3). The influence of Tertiary to recent events (uplift, erosion, glaciation, and sea level changes) on the genesis of these land forms is discussed in Chapters 18 and 19.

The region measures about 3000 km from east to west and 2000 km from the southern islands to the northern tip of Ellesmere Island. Several large ice caps occur on the eastern Canadian Arctic Islands, and the region is bordered to the east by the great Greenland ice sheet — The Inland Ice. The land area described here exceeds 1450 000 km2. A network of channels divides the Canadian islands; many of the channels are broad seaways whereas others are narrow and resemble drowned river systems. Baffin Bay and Nares Strait separate the islands of Canada from Greenland. Baffin Bay and Nares Strait separate the islands of Canada from Greenland. Northern Greenland and the Arctic Islands are characterized by glacier-covered mountains, towering sea cliffs, dark canyons, rolling lowlands, and immense, icefilled
Carboniferous and Permian History of the Sverdrup Basin, Arctic Islands
Authors: Davies G.R. , Nassichuk W.W.
Published: April 2015

Upper Paleozoic carbonates and evaporites with associated basal redbeds, marine shales and minor chert and basic volcanic rocks form the initial fill of the Sverdrup Basin. These rocks are exposed in spectacular fiord cliff faces on northwestern Ellesmere and northern Axel Heiberg islands, and in more subdued terrain on southern Ellesmere, northwestern Devon, northern Melville, Cameron, and Helena islands (Fig. 13.1; for geographic names and regional geology see Fig. 1 and 2 [in pocket]). They also have been penetrated, totally or in part, by 35 exploratory wells, most of which are in the western sector of the basin, on and between Melville and Cameron islands.

Carboniferous evaporites deposited in the centre of the basin have generated halite-cored diapirs and other linear intrusive bodies that influenced the structural development of the basin, deformation of the Mesozoic section, and localization of oil and gas accumulations. Similarity with the upper Paleozoic section on Svalbard and northern Greenland extends the regional implications of upper Paleozoic strata in the Sverdrup Basin in terms of circum-Arctic tectonics and paleoclimates.

The Ellesmerian Orogeny (Chapters 10, 12) probably extended into the earliest Carboniferous (Tournaisian), but appears to have terminated before the deposition of the Visean Emma Fiord Formation. Too little of this formation is preserved to obtain a clear picture of tectonic conditions just prior to the subsidence of the Sverdrup Basin, which commenced in the Namurian and continued to the Late Cretaceous. Structures formed during the initial phase of subsidence, and geophysical evidence for crustal thinning below
Mesozoic History of the Arctic Islands
Authors: Embry Ashton F.
Published: April 2015

Mesozoic strata are widespread in the Canadian Arctic Islands and occur in diverse tectonic-stratigraphic settings (Fig. 14.1). The Sverdrup Basin, which was a major depocentre in the Arctic Islands from Carboniferous to early Tertiary, contains the thickest and most complete Mesozoic succession in the region. In the central portion of the basin Triassic to Cretaceous deposits are up to 9 km thick (Fig. 14.1 ; for well sites and geographic names see Fig. 1, in pocket). Mesozoic rocks in eastern Sverdrup Basin were folded and faulted by regional compression in early Tertiary, and excellent exposures occur in mountainous terrain. To the west, the structures and terrain have much lower relief and outcrop is mainly Cretaceous or younger in age.

Banks Basin on Banks Island (Fig. 4.3) contains a gently-dipping, 1200 m succession of Upper Jurassic to uppermost Cretaceous strata. Scattered outliers of flatlying to tilted Cretaceous strata occur in the Franklinian mobile belt, Arctic Platform and Canadian Shield geological provinces. These outliers are areally restricted and thin, and commonly lie in grabens. Cretaceous strata are also interpreted to occur beneath thick Tertiary deposits along the continental shelf northwest of the Arctic Islands, in eastern Lancaster Sound, and on the continental shelf east of Baffin Island. The nature and thickness of these offshore and deeply buried strata are unknown owing to a lack of data.

The Mesozoic succession in the Arctic Islands consists almost entirely of clastic sediments. In Sverdrup Basin, sandstone units occur mainly on the basin margins with shale-siltstone
Late Cretaceous – Early Tertiary Deformation, Arctic Islands
Authors: Okulitch A.V. , Trettin H.P.
Published: April 2015

Four major phases of deformation with partly overlapping age ranges affected different parts of the Innuitian Orogen and Arctic Platform in late Mesozoic – Tertiary time:

(1) Middle Jurassic (Aalenian) to Early Cretaceous (Barremian): mild uplift and extensional faulting (i.e. rifting) along the northwestern margin of the Arctic Islands;

(2) Early Cretaceous (Neocomian) to earliest Oligocene: normal faulting in the southeastern part of the Arctic Platform and in the Boothia Uplift, accompanied by local transcurrent faulting;

(3) Paleogene (and possibly latest Cretaceous): compressional deformation in the northeastern part of the Arctic Islands (Eurekan Orogeny);

(4) Middle and Late Tertiary (Oligocene-Pliocene): widespread differential uplift, most pronounced in the eastern part of the Eurekan Orogen and around Baffin Bay, accompanied by some normal faulting.

Event 1, known mainly from the stratigraphic record, is discussed in Chapter 14 by Embry, who relates it to rifting in the Amerasian Basin (Fig. 14.60). Structural treatment of this region, including Late Cretaceous and Tertiary events, will have to await systematic analysis of available geophysical information. However, normal faulting, such as on Banks Island (Miall, 1979a), recurred in the Tertiary.

Event 4, inferred from limited geological and geomorphic information, is discussed in Chapter 18.

This chapter is concerned with the Eurekan Orogeny (event 3) and the partly coeval but longer ranging extensional event 2. Kerr’s (1967) hypothesis that the two are related in origin — having been caused by counterclockwise rotation of Greenland — now is widely accepted, and therefore his term, Eurekan Deformation (Kerr, 1977)is
Tectonic Framework
Authors: Trettin H.P
Published: April 2015

This chapter summarizes the major geological components and inferred tectonic events of the Arctic Islands and North Greenland and explains the currently used terms. References are mostly restricted to historical remarks and original definitions; additional references and details are given in later chapters.

Basic elements of the present framework were introduced by Schuchert (1923), who made the first synthesis of North American geology that included the Arctic (Fig. 4.1). The results of the vigorous exploration in the Canadian Arctic Islands in the 1950s and early 1960s were compiled by Fortieretal. (1954), Fortier(1957), Douglasetal. (1963), and by Thorsteinsson and Tozer (1960, 1970), whose “geological provinces” (Fig. 4.2) have served as the basis for all subsequent syntheses. Comprehensive later accounts of this region include Trettin et al. (1972), Drummond (1973, 1974), Stuart Smith and Wennekers (1977), Trettin and Balkwill (1979), and Kerr (1981). Syntheses of the geology of North Greenland were made by Koch (1925, 1935, 1961), Dawes (1971, 1976), Dawes and Soper (1973), and Dawes and Peel (1981).

The first-order elements of the present tectonic framework, all introduced previously, are Canadian Shield, Arctic Platform, and Innuitian Tectonic Province.

The Canadian Shield borders the Arctic Platform on the southeast and extends into it as salients and inliers, such as the core of the Boothia Uplift1, Minto Arch, Melville Horst, and the Wellington and Duke of York highs, exhumed hills on the Late Proterozoic – Cambrian erosion surface (Chapter 3). It consists of a metamorphic-plutonic basement and unconformably overlying sedimentary and volcanic successions
The North American plate boundary
Authors: Eldholm Olav , Karasik A. M. , Reksnes P. A.
Published: April 2015

In the Norwegian-Greenland Sea and the Arctic Ocean the present-day North American plate boundary exhibits great variety in morphology and structural style. From the neovolcanic rift zone in Iceland the plate boundary extends into the Norwegian-Greenland Sea and the Eurasian Basin of the Arctic Ocean as a system of mid-oceanic ridge segments and transform faults, but becomes less distinct beneath the Siberian continental margin (Fig. 1). The asymmetry in the location of some of the active spreading axes, as well as the existence of extinct spreading centers, microcontinents, and volcanic plateaus and ridges imply a complex structural evolution of the surrounding ocean basins. It is reasonably well documented that the oldest oceanic crust formed by sea-floor spreading between Greenland, Lomonosov Ridge, and Eurasia dates back to the negative polarity interval between magnetic anomalies 24B and 25 (late Paleocene/early Eocene).

In this chapter we focus on a description of the present plate boundary in terms of morphology, relative plate motion, variation in geological and geophysical parameters, and seismicity. For practical purposes we restrict ourselves to the youngest crust and primarily discuss the crust formed during the past 10 m.y. More comprehensive treatments of the ocean basins and their plate tectonic evolution are presented by Eldholm and others (this volume) and by Kristoffersen and others (this volume). Various aspects of the plate boundary north of Iceland have also been discussed in the Western North Atlantic synthesis volume of this series (Einarsson, 1986; Melson and O’Hearn, 1986; Schilling, 1986; Srivastava and Tapscottt, 1986; Vogt, 1986).
The North Greenland Continental Margin
Authors: Dawes Peter R.
Published: April 2015

Physiographically, the North Greenland margin is an eastward extension of the passive rifted continental margin of the Canadian Arctic Islands (see Sweeney and Sobczak, this volume); however, geologically it has a very different setting. It is a transform-rifted margin and represents the only part of the margin that borders the relatively young, oceanic, and seismically active part of the Arctic Basin—the Eurasia Basin. This is in contrast to the extensive western margin that faces the older and seemingly more complex Amerasia (Canada-Makarov) Basin (Fig. 1).
Chukchi Borderland
Authors: Hall John K.
Published: April 2015

The Chukchi Borderland occupies a rectangular area about 600 by 700 km, or some 4 percent of the Arctic Ocean. It juts out into the deep Amerasia Basin north of the Chukchi Sea, between eastern Siberia and western Alaska (Fig. 1). This area encompasses three approximately north-south-trending segmented ridges: the Northwind Ridge, the Chukchi Cap and Rise, and the western (Arlis, Sargo, and T3) plateaus. Their plateau-like crests rise, in some cases, as much as 3,400 m above their surroundings and they are relatively shallow (depths between 246 and 1,000 m). The ridges have steep flanks, which in some places exhibit remarkable linearity over hundreds of kilometers, especially along the east side of the Northwind Ridge. Between these ridges lie the Northwind, Chukchi, and Mendeleev abyssal plains. These lie at depths between 2,100 and 3,850 m. To the south, the Chukchi Borderland is bounded by the broad and shallow Chukchi Shelf.

Although Figures 1a and b show the Chukchi Borderland to be one of the better-mapped features in the Arctic Basin, its existence was unknown until the 1950-1951 drift of the Soviet ice station North Pole–2 (NP-2; Somov, 1954-1955), when it was discovered by wire soundings. In fact, in the map of Emery (1949), the borderland appears as the deepest part of the Arctic Basin, primarily as a result of an erroneous sounding of 5,455 m from an aircraft landing in 1927, reported by Wilkins (1928). Following its initial discovery in 1950, the general morphology of the plateau
Eurasia Basin
Authors: Kristoffersen Yngve
Published: April 2015

The Arctic Ocean is divided into the Eurasia Basin and the Amerasia Basin by the submarine transpolar Lomonosov Ridge (Fig. 1; Plate 1). This chapter provides current knowledge about the geology and geophysics of the Eurasia Basin and its surroundings, derived primarily from ice station and polar expedition data obtained during the past 25 years.

Nansen’s pioneering drift with FRAM in 1893 to 1896 (Fig. 2) provided the first soundings, pendulum gravity, and magnetic measurements together with geological samples from the Eurasia Basin (Nansen, 1906). The deployment of the Soviet ice station Northpole-I in 1937 set an operational strategy in Arctic research still followed today, and many Soviet drifting ice camps have entered the Eurasia Basin carrying out a wide range of scientific observations (Fig. 2).

Arlis-II in 1964 was the first United States ice station to traverse the southern end of the Eurasia Basin. With the FRAM I-IV temporary ice stations in 1979 to 1982 and the Canadian LOREX Expedition and two smaller expeditions in 1966 and 1969, the data base in the Eurasia Basin comprises more than 1,700 km of seismic reflection, depth, and gravity measurements. In addition, 22 seismic refraction experiments have been carried out, about two dozen short sediment cores have been recovered, and a dozen heat-flow measurements have been made. The data collected by Soviet scientists has to be added to this inventory.

Traverses by nuclear submarines since 1957 have contributed to mapping of the major bathymetric features in the Arctic Ocean
Structure and dynamics of the Arctic Ocean ice cover
Authors: Untersteiner Norbert
Published: April 2015

At its maximum extent in February/March, sea ice covers about 10% of the total ocean surface in the Northern Hemisphere (Fig. 1). Except for some narrow bands along the North American and Siberian coasts, the Central Arctic Basin is ice covered throughout the year. Seasonal ice (winter only) occurs in the marginal seas: Okhotsk, Bering, Kara, Barents, Baltic, Southern Greenland, Baffin Bay-Davis Strait, Hudson’s Bay, and Canadian Archipelago (Plate 1).

The physical constitution of sea ice is that of an aggregate of pieces, ranging in size from small crystals (frazil) and fragments (brash) to solid plates many kilometers in diameter and several meters thick. Winds and ocean currents keep the ice in almost perpetual motion, causing it to diverge, converge, shear, and rotate, thus maintaining its fragmented character. Where thin ice is crushed between two converging heavy floes, pressure ridges are formed with keel depths of up to several tens of meters. Diverging motion exposes the sea surface to the atmosphere and (during the cold season) induces formation of new ice.
Late Mesozoic and Cenozoic paleoceanography of the northern polar oceans
Authors: Thiede Jörn , Clark David L. , Herman Yvonne
Published: April 2015

High-latitude polar regions of the Earth have experienced cold, cool, and temperature paleoclimates in the course of their geologic history, but they have probably always been colder than low-latitude continents and oceans. Extreme climates leading to development of extensive frozen and ice-covered regions at high latitudes can, however, only be documented for a few, relatively short intervals of the Earth’s history, separated by long time spans with little or no ice (Frakes, 1979). The Cenozoic evolution of glacial-type climates during the past 30 to 40 m.y. is the most recent period of extreme climate, and differs from the preceding ones. During the Cenozoic, plate-tectonic processes generated climatically isolated land areas and ocean basins in both the Southern and Northern Hemispheres, which were repeatedly affected by glaciations. For glacial-type paleoclimates older than the Cenozoic, we have only been able to document unipolar glaciation because the opposite high-latitude area was situated in wide and deep ocean basins and was probably relatively ice free due to advection of warmer surface water from lower latitudes.

Despite the apparent similarity of Quaternary high-latitude paleoclimates, the development of glacial-type paleoceanographies of the northern and southern polar oceans have revealed important differences, and they are not easily compared with each other. Our understanding of Cenozoic Southern Hemisphere paleoclimates is much more advanced than it is for the Northern Hemisphere. It is particularly intriguing that the available data appear to indicate that the Southern Hemisphere may have become cold more than 20 m.y. earlier than its northern counterpart.
Historical background; Exploration, concepts, and observations
Authors: Weber J. R. , Roots E. F.
Published: April 2015

The first of the four main parts of this chapter presents a short history of the European discovery of circumpolar lands and the Arctic Ocean from the earliest recorded voyages to the twentieth century. The story of geographic exploration of the Arctic regions has been told many times, and there is an enormous literature dealing with expeditions and geographic discoveries. Particularly useful in providing the historical setting for the growth of scientific knowledge of the Arctic Ocean area is the compilation by Kirwan (1959), who provides insights into the economic, strategic, political, and personal motives behind many of the explorations; and the scholarly analyses edited by Rey and others (1984), which trace the development of geographic and scientific knowledge of the Arctic as a result of myths, conjectures, genuine discoveries, and increasingly precise observations from antiquity to the eighteenth century.

The next part deals with the mapping of the Arctic Ocean basin and floor during the last century, from sparse information that led to a shallow, single-basin concept to the complex sea- floor morphology that gradually emerged as a result of the more detailed surveys beginning with the Soviet explorations in 1937. This section ends with a description of the major modern bathymetric maps and charts that have appeared in print, from Bartholomew in 1897 to Perry and others (Plate 1, this volume).

The third section is an outline of the history of the geoscien- tific work carried out within the Arctic Ocean region, from ships, from drifting stations, and
Offshore hard minerals
Authors: Hale Peter B.
Published: April 2015

Offshore mining for minerals such as barite, coal, calcium carbonate, gold, and tin is a well-established industry in many countries. Although there have been several attempts to develop mining systems to recover manganese nodules in water depths of 4,000 m, commercial mining is at present confined to shallow coastal waters.

Undersea mining for sub-surface deposits dates from at least the early 1600s and accounts for a significant proportion of the total mineral production in some countries. More than 100 undersea mines have been constructed worldwide; with few exceptions they began as onland mines that moved offshore after the onland sources were depleted (Austin, 1967).

In 1977, the last year for which comprehensive global production statistics are available, offshore non-fuel mineral production was worth about $460 million, with most of that coming from sand and gravel, tin, and calcium carbonate (Glasby, 1979). This valuation is conservative because numerous small operations go unreported and the Soviet Union does not make public its production statistics. The Soviet Union has, for several years, dredged cassiterite for tin in the Arctic Ocean, but we have no information regarding the level of production.

Most marine mining activity to date has taken place in temperate or tropical regions, yet the Arctic may host equally exciting mineral deposits, and both tin and sand and gravel are already mined there. The problems of mining in a region covered by ice for much of the year should not, however, be underestimated. New technologies will be required for exploration and mining
A review of tectonic models for the evolution of the Canada Basin
Authors: Lawver L. A. , Scotese C. R.
Published: April 2015

The Arctic Ocean has a nearly continuous ice cover that makes collection of shipborne geological and geophysical data almost impossible. As late as 1907 (Mikkelsen, 1955), expeditions were still being sponsored to discover the elusive northern continent thought to occupy much of the region. Since the plate- tectonic revolution of the sixties, numerous theories concerning the tectonic origin of the Arctic Ocean, and the Canada Basin in particular (Fig. 1), have been proposed.

Tectonic models for the Canada Basin can be separated into three broad categories: oceanization of continental crust, entrapment of old oceanic crust, and the in situ formation of the oceanic crust by sea-floor spreading. The first category consists of the tectonic model originally suggested by Shatskiy in 1935 and later given prominence by Beloussov in the 1950s and 1960s (Shatskiy, 1935; Beloussov, 1970). They argued that the Canada Basin was a cratonic high that shed debris southward onto Arctic Canada and the north slope of Alaska, and that this high was later oceanized by mantle convection that eroded the root and caused the area to subside. Pogrebitskiy (1976) and Pushcharovskiy (1976) also invoked oceanization of continental crust to explain the formation of the Canada Basin, but Pogrebitskiy and others (1984) later explained the formation of the basin by a combination of lithospheric oceanization and granitization (endogenic differentiation).

The second category of models suggests that much of the Canada Basin resulted from entrapment of older oceanic crust (Churkin, 1970; Churkin and Trexler, 1980; Karasik and others, 1984)
Summary
Authors: Sweeney J. F. , Johnson G. L. , Grantz A.
Published: April 2015

As this volume makes clear, the last 15 years have seen a revolutionary increase in the amount and variety of geoscientific information retrieved from Arctic domains. While the new data have done much to improve the definition of major Arctic crustal and submarine features, it is evident that the latest results provide only modest new constraints on the evolution of the region.

The Eurasia Basin became part of the world ocean about 10 m.y. ago and it has had a significant impact on the Earth’s climate system since that time. The history of this linkage is crucial to the study of global change through time. An understanding of past and present plate movements in the Arctic is needed to build accurate tectonic models of the world during the late Mesozoic and Cenozoic, which in turn, are highly relevant to resource exploration.

In this chapter we summarize the present knowledge of the north polar area from a geoscientific and an environmental point of view, assess some outstanding scientific problems, and pose research targets for the upcoming decade.
Seismicity and focal mechanisms of the Arctic region and the North American plate boundary in Asia
Authors: Fujita Kazuya , Cook David B. , Hasegawa Henry , Forsyth David , Wetmiller Robert
Published: April 2015

Although Arctic earthquakes have been recorded since 1908, detailed study of them has been hampered due to the lack of seismograph stations and the infrequent occurrence of large earthquakes north of the Arctic Circle. Detailed analysis of Arctic earthquakes began during the International Geophysical Year (IGY, 1957–1958), and subsequent studies have been facilitated by the development of the World-Wide Standardized Seismograph Network (WWSSN) starting in 1963.

Many authors have published summaries of Arctic seismicity. The pre-IGY state of knowledge is summarized by Hodgson and others (1965), and epicentral coordinates and magnitude estimates of pre-WWSSN seismicity are given in Gutenberg and Richter (1954), Linden (1961), Hodgson and others (1965), and Rothe (1969). Overview summaries of the distribution and magnitude of Arctic seismicity are presented by Sykes (1965) and Wetmiller and Forsyth (1978). Numerous maps of Arctic seismicity have been published (e.g., Veis-Ksenofontova, 1962; Sykes, 1965; Barazangi and Dorman, 1970; Tarr, 1970; Wetmiller, 1978; Avetisov and Sokolova, 1980). Additional details about Arctic seismicity are given in international bulletins, national seismicity summaries, and annual reports.

In this chapter we summarize the development of seismograph stations in the Arctic, the distribution of seismicity in the Arctic, focal mechanisms that have been determined for the Arctic seismic zone, including northeastern Siberia and Baffin Bay, and the implications of the seismic data for plate tectonic models of the region. In addition, we summarize inferences on crustal structure of the Arctic region based on the propagation characteristics of earthquake waves.
Perspectives on the geology of the North Atlantic Ocean
Authors: Tucholke Brian E. , Vogt Peter R.
Published: April 2015

This volume deals with the geology and geophysics of the western North Atlantic, the basin between the Mid-Atlantic Ridge and the eastern margin of North America. Although the book’s focus is on the “North American Basin” (Fig. 1), individual chapters and charts extend the bounds beyond the “western North Atlantic.” These extensions were dictated by the geology, which cannot be synthesized meaningfully if constrained by artificial geographic or political boundaries. Generally speaking, the content of this volume is contained within the region surrounded by the continental margins of the Antilles, eastern North America, Greenland, and Iceland in the west and north, the Mid- Atlantic Ridge crest on the east, and approximately 10°–15° N latitude to the south. However, in dealing with the Mid-Atlantic Ridge, plate kinematic models, and Atlantic paleogeography, we have extended our scope north into the Arctic region and east into the eastern Atlantic in order to present a complete synthesis of this major plate boundary and its evolution through time. The significance of Iceland for oceanic geoscience often has been overlooked or underrated; to help remedy this, two chapters deal mainly with this remarkable subaerial exposure of the Mid-Atlantic Ridge. One topic, mid-plate seismicity and stress, also demanded a plate-wide treatment covering the entire “stable” lithosphere from the Mid-Atlantic Ridge to the western Cordillera. Placing this treatment in the North Atlantic synthesis presumes that mid-plate stress is closely related to absolute plate motion (which is calculated largely from oceanic data) and/or to “ridge-push” forces from the