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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Arctic Ocean
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Canada Basin (3)
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Arctic region
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Greenland (1)
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Banks Island (1)
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Canada
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Arctic Archipelago (3)
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Nunavut
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Ellesmere Island (1)
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Somerset Island (1)
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Sverdrup Basin (1)
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Sverdrup Islands
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Ellef Ringnes Island (1)
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Queen Elizabeth Islands
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Ellesmere Island (1)
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Sverdrup Basin (1)
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Sverdrup Islands
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Ellef Ringnes Island (1)
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Western Canada
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Northwest Territories (5)
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North America
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Canadian Shield (1)
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United States
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Alaska (1)
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Maine
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Penobscot Bay (1)
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Penobscot County Maine (1)
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geochronology methods
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paleomagnetism (1)
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geologic age
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Cenozoic
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Tertiary (1)
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Mesozoic
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Cretaceous (1)
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Paleozoic
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Devonian (1)
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upper Paleozoic (1)
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igneous rocks
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igneous rocks (1)
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Primary terms
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Arctic Ocean
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Canada Basin (3)
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Arctic region
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Greenland (1)
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Canada
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Arctic Archipelago (3)
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Nunavut
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Ellesmere Island (1)
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Somerset Island (1)
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Sverdrup Basin (1)
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Sverdrup Islands
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Ellef Ringnes Island (1)
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Queen Elizabeth Islands
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Ellesmere Island (1)
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Sverdrup Basin (1)
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Sverdrup Islands
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Ellef Ringnes Island (1)
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Western Canada
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Northwest Territories (5)
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Cenozoic
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Tertiary (1)
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continental shelf (1)
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crust (2)
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faults (1)
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geochemistry (1)
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geomorphology (1)
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geophysical methods (1)
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igneous rocks (1)
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intrusions (1)
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isostasy (1)
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maps (2)
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marine geology (1)
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Mesozoic
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Cretaceous (1)
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metamorphism (1)
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North America
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Canadian Shield (1)
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oceanography (1)
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paleomagnetism (1)
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Paleozoic
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Devonian (1)
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upper Paleozoic (1)
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petrology (1)
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plate tectonics (1)
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sea-floor spreading (1)
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sedimentary rocks
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clastic rocks (1)
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sedimentation (1)
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structural analysis (1)
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structural geology (3)
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tectonics (3)
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tectonophysics (1)
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United States
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Alaska (1)
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Maine
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Penobscot Bay (1)
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Penobscot County Maine (1)
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sedimentary rocks
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sedimentary rocks
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clastic rocks (1)
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Abstract 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
Introduction
Abstract Although a sea voyage to ice-infested northern waters was described in antiquity, and repeated attempts to discover a commercial water route to the north of Eurasia and North America were made from the sixteenth century onward, the physical geography of the north polar region was little studied until systematic scientific investigations were undertaken late in the eighteenth century. The International Polar Year in 1882–1883 marked the beginning of coordinated multinational, interdisciplinary scientific studies around the Arctic, and by the end of the nineteenth century, Nansen had demonstrated that a deep ocean exists beneath the ice pack in the central Arctic. Subsequent delineation of the Arctic sea floor has improved gradually; today, although much of the seabed morphology is unknown in detail, the larger physiographic features have been mapped in reconnaissance fashion. Crustal and marine studies of the area have been underway since the mid-twentieth century. By the 1960s, much new information about these aspects of Arctic science had been acquired and summarized in major volumes such as Raasch (1961). The present volume gives a comprehensive exposition and analysis of geological and geophysical information available from the Arctic Ocean and adjacent seas as of the late 1980s. The information presented is in the public domain. Commercial and military proprietary data are excluded. Also absent is much of the important work done in the Arctic by Soviet scientists who, unfortunately, were unable to participate significantly in this synthesis. This volume covers the Arctic Ocean region and its extension into the Norwegian-Greenland Sea
Abstract 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
Front Matter
Back Matter
Abstract 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.
Arctic Ocean ice cover; Geologic history and climatic significance
Abstract The Arctic Ocean is unique among the world’s oceans because of its perennial ice cover. The geologic and climatologic factors that contributed to development of the Arctic Ocean ice cover are understood in a general way, even though the precise mechanism and time during the Cenozoic that the first ice cover formed are not known. Data concerning climatological processes that encouraged development of an Arctic Ocean ice cover have developed from the general understanding of the paleogeographic sequence of events since the last major time of ice-free conditions during the Cretaceous and early Cenozoic. The lack of facts concerning the precise time, and to some extent the mechanism, of ice cover origin is largely the result of an inadequate data base in the Arctic Ocean. For example, no long sediment core with middle Cenozoic sediment that may represent the time of the initial ice-cover development has been collected. Unfortunately, no research ship with capability for recovery of long sediment cores has been designed for work in the area of year-round Arctic pack ice. Therefore, the only sediment record for the central Arctic Ocean is that recovered from drifting ice stations such as the U.S. T-3 program and the Canadian LOREX and CESAR projects. Offshore drilling on the continental slope of Alaska and Canada has penetrated a more complete Cenozoic section. The sediment is largely non marine and, in the shallow Beaufort Sea area, consists of thick deltaic sediment. Detailed paleoclimato- logic study of this sediment has not been accomplished, but
Abstract The oceanic regions located north of the Arctic Circle are the Arctic Ocean, the Norwegian-Greenland Sea, and Baffin Bay (Plate 1). The latter is described in Keen and Williams (1990). Despite the bold isobaths in Plate 1, the bathymetry of the Arctic Ocean is still poorly known. Most of the Norwegian-Greenland Sea, on the other hand, is quite precisely charted. Exceptions are the areas east of Greenland often covered by the pack ice that exits the Arctic Ocean in the East Greenland current. The names used for the physiographic features in this volume are those shown on Plate 1. Different names that have been applied to these features in the literature are given in Sweeney and others (this volume.)
Seismicity and focal mechanisms of the Arctic region and the North American plate boundary in Asia
Abstract 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.
Gravity from 64°N to the North Pole
Abstract Although gravity observations were made prior to 1960, systematic regional gravity coverage in the Arctic began in earnest in the early 1960s on land and sea ice with the advent of helicopters and reliable portable gravimeters, and was extended in the 1970s over the oceans with ships and reliable marine gravimeters. As a result, about half of the polar area north of 64°N latitude is now covered with regional (spacings 12 km or less) gravity observations for which the data are readily available to the public. Permanently ice-covered regions of the Arctic Ocean, as well as mountainous and glacier-covered areas, are still largely unmapped. Except for a few pre-World War II gravity stations from regions within the Soviet Union (USSR), no gravity data from the USSR are displayed on Plate 3. The observed gravity field of the whole Arctic region north of 60°N was first discussed by Sobczak (1978), who presented maps (scale 1:7,500,000) showing the gravity field derived from mean values based on observed (1/2° latitude × 2° longitude) and predicted (1° latitude × 1° longitude) free-air anomalies and a residual gravity field derived by removing the satellite gravity field (Goddard Earth Model 8, GEM 8) from the observed and predicted fields. These maps indicate anomalous gravitational features of wavelengths in excess of 100 km. Bowin and others (1982) presented a comprehensive free-air gravity anomaly atlas of the world, including a map of the Arctic region north of 70° at a scale of about 1:14,000,000. The intent of the present
Abstract Extensive magnetic surveys have been made over the Arctic Ocean since 1946. The survey techniques have varied, as have the methods and forms of data presentation. This chapter reviews the magnetic anomaly information from the Arctic Ocean region and discusses the significant contributions made by magnetic surveys to the understanding of this region of the earth’s crust. The magnetic anomaly field is the only geophysical parameter in the Arctic that has been reasonably uniformly measured. It is critical to the study of Arctic structure and evolution.
Geothermal observations in the Arctic region
Abstract A fundamental goal of geothermal studies in the Arctic region is to determine the rate of heat flow from deep in the earth’s crust. Research during the past 25 years has shown heat flux is closely related to the tectonic evolution of a geological province. When combined with other geological and geophysical data, accurate heat-flow measurements can set constraints on crustal temperatures, age and evolution of the lithosphere, and the distribution of radiogenic heat in the crust. At an even more fundamental level, accurate measurements help determine the total rate of heat loss from the Earth and define the global variation of heat flow and its correlation with other long-wavelength geophysical features. In addition to the fundamental scientific interest, the subsurface thermal regimes of continents and continental margins of the Arctic are of practical concern for natural resource development. Mean annual surface temperatures on land are well below freezing, which results in a permafrost layer hundreds of meters thick in some places; for example Judge and others (1981) reported a permafrost thickness of 726 m on Cameron Island in the Canadian Arctic Archipelago. The ice-bearing permafrost presents many obstacles to the development of resources and the maintenance of facilities in the Arctic, and as a consequence, a considerable effort has been made by the Canadian and United States governments and industry to evaluate the subsurface thermal regime from an engineering perspective. These efforts have provided many drill holes for subsurface temperature and thermal properties data. Many of these holes will provide
Seismic reflection and refraction
Abstract The ice cover of the Arctic Ocean restricts research vessels, limiting the number of miles of seismic reflection and refraction lines in the area. Figures 1 and 2 show the distribution of the lines, andTables 1 and 2 provide references keyed to those figures. This paper describes the distribution, collection, and processing of the seismic reflection and refraction data available in the deep basins and major ridges in the Arctic Ocean and briefly discusses the salient geological results by region. In addition, the position of seismic surveys on the continental margins and adjacent landmasses of the North American plate have been compiled for completeness. These peripheral areas are documented with recent review papers Table 1) including Eldholm and others (this volume) and Larsen (this volume). Most of the seismic reflection information in the Arctic Ocean has been collected on drifting ice stations; thus, the direction of the lines is controlled by the whims of nature. The data set presented here is incomplete due to the inaccessibility of information collected by Soviet scientists. No seismic profiling has been run from the northern margin of Greenland, and only three refraction surveys and one reflection line exist on the Canadian Polar margin from Greenland to the Beaufort Sea. Most of the reflection lines in the Canada Basin were acquired with power sources of insufficient strength to penetrate the sedimentary section. Even with this meager collection of erratically spaced and variable quality information, important trends can be seen, interesting features
The North American plate boundary
Abstract 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).
Abstract Geologically, the East Greenland Shelf remained virtually unexplored for many years while the onshore East Greenland Mesozoic basin stratigraphy was intensely studied and served as a reference for the interpretation of the offshore East Greenland and northwest European margins. This development was a natural consequence of the excellent onshore basin exposure while polar pack ice is found almost year-around on the East Greenland shelf. The first geophysical information from the East Greenland shelf was published by Vogt (1970), Eldholm and Windisch (1974), Johnson and others (1975a, b), B. Larsen (1975), H. C. Larsen (1975, 1978), Henderson (1976), and Featherstone and others (1977). Results of the first multichannel reflection seismic surveying on the shelf were reported by Hinz and Schlüter (1978, 1980). On the basis of this information and initial results from an aeromagnetic survey (H. C. Larsen and Thorning, 1979, 1980), a regional geological model for the East Greenland Shelf was proposed by H. C. Larsen (1980). This model involved early Tertiary oceanic crust thought to be present below parts of the outer shelf off central East Greenland and subsided continental crust thought to be present up to approximately 100 km seaward of the shelf break off southeastern Greenland. The actual position of the shelf edge was found to be controlled mainly by post-rift sedimentation rather than deep crustal features (H. C. Larsen, 1980). It was further suggested that Cenozoic basins might dominate the southern half of the shelf while Mesozoic and Paleozoic basins were likely to be present beneath the northern shelf.
Abstract 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).
Abstract The polar continental margin described here lies between M’Clure Strait and the Lincoln Sea (Fig. 1). It clearly separates continental sequences of the Queen Elizabeth Islands from presumed oceanic crust beneath the deep Canada Basin and, near Axel Heiberg and Ellesmere Islands, from rocks of the submarine Alpha and Lomonosov Ridges. Systematic studies in the region began in the late 1940s with Soviet air-lifted spot soundings over the outer continental slope and rise. In the 1950s and 1960s, the Alpha Ridge and adjacent parts of the outer continental shelf and slope were identified by multiparameter measurements from a series of drifting U.S. ice stations. In Canada, onshore geological studies began in 1955, and reconnaissance investigations of the polar shelf and slope were underway by 1960. The reader is referred to Weber (1983) and Weber and Roots (this volume) for further details of early studies. Comprehensive reviews that include onshore geology adjacent to the polar margin begin with Fortier and others (1963) with later syntheses by Thorsteinsson and Tozer (1970), Trettin and others (1972), Trettin and Balkwill (1979), Hea and others (1980), Miall (1981), and Kerr (1981). Offshore, chiefly geophysical data over the polar shelf and slope are summarized by Trettin and others (1972), Sweeney and others (1978), Vogt and others (1982), Sweeney (1982), and Forsyth and others (1988). From the information available up to the early 1980s, it was considered that the polar margin formed when the Canada Basin opened in Jurassic or Early Cretaceous time, that the crust
Abstract The Canadian Beaufort Sea extends from offshore Banks Island to 141 °W longitude (Fig. 1). It is rimmed to the south by the Yukon Coastal Plain, the outer Mackenzie Delta, including Richards Island, and Tuktoyaktuk Peninsula. The narrow coastal plain of northern Yukon is bounded to the south by the British Mountains and the Porcupine Plateau (Fig. 1). The broad Amundsen Gulf separates the Anderson and Horton plains of the Northwest Territories mainland from Banks Island and Victoria Island. The continental margin beneath the Beaufort Sea can be divided into several physiographic regions. The shallow-water shelf is 50–100 km wide and is characterized by low, uniform slope gradients of 1–2 m/km. An abrupt increase in the sea-floor slope gradient marks the shelf edge. Water depths at the shelf break vary from 60 m near 141°W to almost 500 m west of Banks Island. Two channel-like features cut across the Beaufort shelf. Northeast of Herschel Island, the Mackenzie Trough (formerly Mackenzie Canyon) cuts obliquely across the shelf in a northwesterly direction (Fig. 1). Southwest of Banks Island, the broad Amundsen Gulf channel cuts across the shelf in a northwesterly direction. Both of these bathymetric troughs are 100–500 m deep and are geologically recent in origin. The continental slope seaward of the shelf edge is 20–50 km wide and is characterized by variable slope gradients of 5–30 m/km. The outer continental slope north of the Mackenzie Trough is marked by a steep, sea-floor escarpment with local slope gradients of up to 170 m/km (Fig. 1)
Geology of the Arctic Continental Margin of Alaska
Abstract Alaska faces the Canada Basin of the Arctic Ocean along an arcuate continental margin, gently concave to the north, that stretches unbroken from the Mackenzie Delta, near 137°W to Northwind Ridge of the Chukchi Borderland near 162°W. (These and other regional geographic features mentioned below can be found in Plates 1 and 11.) This margin, with an arc-length of about 1,050 km, marks one side of a continental rift along which the Canada Basin opened by rotation about a pole in the Mackenzie Delta region during middle Cretaceous time. The rift- margin structures, which lie beneath the inner shelf and coastal plain in the eastern Alaskan Beaufort Shelf and beneath the outer shelf in the western Beaufort and Chukchi Shelf, are now buried by a thick middle Lower Cretaceous to Holocene progradational continental terrace sedimentary prism. We divide the Arctic continental margin of Alaska into three sectors of strongly contrasting geologic structure and physiographic expression. In the Barter Island sector (see Figs. 3 and 4) the structure is dominated by the effects of Eocene to Holocene convergence and uplift, and the continental slope is upwardly convex; in the Barrow sector the structure is dominated by the effects of middle Early Cretaceous rifting and continental breakup, and the continental slope is upwardly concave; and in the Chukchi sector the structure is controlled by an easterly trending middle Early Cretaceous rift, and the continental slope abuts the Chukchi Borderland. Physiographically, the Alaska continental margin is expressed by the Alaska continental
The Arctic continental margin of eastern Siberia
Abstract The Arctic Ocean margin of the North American plate in Asia forms a continental shelf up to 800 km wide, which underlies the East Siberia Sea (Fig. 1). The New Siberian Islands separate the East Siberian Sea from the Laptev Sea on the west, and Wrangel Island (Ostrov Vrangelya) separates the East Siberian Sea from the Chukchi Sea on the east. The area of the East Siberian Sea is about 1,500,000 km 2 , and it is connected to the Chukchi Sea by Long Strait (Proliv Longa) and to the Laptev Sea by several straits through the New Siberian Islands. The shelf of the East Siberian Sea is shallow, less than 50 m deep, and flat. The shelf is cut by two valleys, a few tens of meters deeper than the surrounding shelf, which are extensions of the Indigirka and Kolyma rivers (Naugler and others, 1974). The continental slope of the East Siberian Sea is gentle (slope ~1°), and alluvial cones spread out into the adjacent abyssal plain from submarine canyons (Lastochkin, 1980). The shelf appears to be connected to the Arlis Plateau, but is separated from the Lomonosov Ridge by a sediment-filled trough (Dementiskaya and Hunkins, 1971) (Fig. 2). Since the geology of the East Siberian Shelf is poorly known, most tectonic and geologic models are extrapolations of the geology of the New Siberian Islands. Wrangel Island, and northern Eurasia. Rather than present the details of these speculations, in this chapter we summarize the known geology of