Canadian Arctic Rift System
Canadian Arctic Rift System | |
---|---|
Rift system | |
Coordinates: 65°N 58°W / 65°N 58°W | |
Location | Canada/Greenland |
Age | Paleozoic-to-Cenozoic |
Dimensions | |
• Length | 4,800 km (3,000 mi) |
The Canadian Arctic Rift System is a major
.Development of the Canadian Arctic Rift System was accompanied by two
Geology
The Canadian Arctic Rift System is a branch of the Mid-Atlantic Ridge that extends 4,800 km (3,000 mi) into the North American continent. It is an incipient structure that diminishes in degree of development northwestward, bifurcates at the head of Baffin Bay and disappears into the Arctic Archipelago. The rift system is mainly an extensional structure, which has allowed Greenland and Canada to rotate apart and form intervening seaways.[1] The segment extending from the Labrador Sea to Baffin Bay is sometimes referred to as the Labrador Sea–Baffin Bay rift system or the North Atlantic–Labrador Sea rift system.[2][3]
Tectonic evolution
Two rifting episodes created the Canadian Arctic Rift System. The first is referred to as the Boreal Rifting Episode which followed
Boreal Rifting Episode
The Boreal Rifting Episode began in the
Eurekan Rifting Episode
The Eurekan Rifting Episode commenced in the Early Cretaceous as the Boreal Rifting Episode declined.[5][4] Crustal stretching began at the south end of the rift system 130 million years ago, during which time supercontinent Laurasia was in the process of breaking apart.[6] Rifting began from the Atlantic Ocean then propagated northwest where the Labrador Sea started opening in the Late Cretaceous.[4][7] Seafloor spreading commenced in the southern Labrador Sea 75–60 million years ago, during which time Greenland moved north relative to mainland North America. This northward movement gave rise to compressive forces between northern Greenland and the Arctic Archipelago, setting the stage for the Eurekan orogeny. Seafloor spreading reached the northern Labrador Sea 60–40 million years ago and Greenland moved simultaneously past Ellesmere Island along the Nares Strait.[7] Approximately 170 km (110 mi) of Paleocene separation occurred between Greenland and Baffin Island, producing oceanic crust within Baffin Bay.[8]
With the commencement of active seafloor spreading in the
The final phase of rifting was marked by continental extension in the mid-Tertiary.[4] It breached the North American continent and reached the Arctic Ocean, resulting in the formation of the Parry and Nares submarine rift valleys, the Queen Elizabeth Islands and the Queen Elizabeth Islands Subplate.[4][11] This rifting lasted until the Early Miocene or later.[4]
The rift system today
Little seismicity takes place on the Canadian Arctic Rift System, indicating that it is now a nearly inactive structure and that the entire system is travelling as a part of the North American Plate. Several earthquakes occur but their patterns indicate that tectonic forces characteristic of plate margins are not acting directly within the Canadian Arctic today. As a result, there are questions as to whether the Greenland Plate should still be considered a separate plate.[4] The present seismic activity may be mainly an expression of readjustment of existing rift structures to a regional stress field associated with post-glacial rebound.[4][12]
The area between Greenland and Baffin Island is one of the most seismically active regions in eastern Canada.
A linear belt of medium-amplitude earthquakes known as the Labrador Sea Seismic Zone is coincident with the extinct spreading axis of the Mid-Labrador Ridge.[15] Earthquakes as large as magnitude 5.0 have been recorded along this zone since 1982.[16]
Structure
Faults
The
Situated on
Extending several hundred kilometres through
The Kaltag Fault is a northeast trending structure that extends along the continental margin northwest of the Queen Elizabeth Islands. It forms a boundary between the Canadian Arctic Rift System and other rifted structures to the northwest.[4] The Kaltag acted as a transform fault with intermittent pulses of both extension and strike-slip displacement during three time intervals.[4][26] Tectonism during the first time interval from Carboniferous to Permian was coeval with an early stage of the Boreal Rifting Episode. This was followed by a second time interval of tectonism from the latest Cretaceous to early Tertiary when the Boreal Rifting Episode was active and the Eurekan Rifting Episode was in an early stage of development. A third and final time interval of tectonism during the Miocene or Pliocene coincided with the final phase of the Eurekan Rifting Episode, during which time the Kaltag Fault was the northwestern boundary of the Queen Elizabeth Islands Subplate.[26]
Trending along the north side of Lancaster Sound is a major steeply dipping normal fault called the Parry Channel Fault.[27][8] As much as 8 km (5.0 mi) of vertical displacement took place along this fault during the Eurekan Rifting Episode.[4] The Northern Baffin and Admiralty faults trend along the south side of Lancaster Sound, the former of which is dominant. It extends from Admiralty Inlet in the west then trends eastward along the north coasts of Baffin and Bylot islands to Baffin Bay where it possibly connects with other rift structures.[27]
The Prince Regent Fault is a major fault that trends along the east coast of Somerset Island. It forms the southwestern boundary of the Lancaster Aulacogen and is west of the inferred Brodeur Peninsula Fault, which presumably trends along the northwest coast of Baffin Island's Brodeur Peninsula. The main evidence of the Prince Regent Fault is the straightness of Somerset Island's east coast, but the southern end of this fault also connects with a lineament that is a known fault on land.[27]
A series of fracture zones are present in the Labrador Sea. These include the northeasterly trending Julian Haab and Cartwright fracture zones, as well as the north-northeasterly trending Hudson, Snorri, Minna and Leif fracture zones.[6] The change in trend corresponds with a more northerly spreading direction of the Mid-Labrador Ridge during the Eocene.[28]
Basins
Sverdrup Basin is a Carboniferous rift basin in the Queen Elizabeth Islands that formed during the Boreal Rifting Episode.[5][29] It has a northeast–southwest axis of about 1,300 km (810 mi) and a width of up to 400 km (250 mi), encompassing an area of 313,000 km2 (121,000 sq mi).[29]
Baffin Basin is a north-northwest trending geologic structure underlying much of central Baffin Bay.[30] It formed as a result of seafloor spreading during the Tertiary opening of Baffin Bay around 56 million years ago. The northern extent of the basin is bounded by the Jones Sound, Lancaster Sound and Nares Strait aquatic sills 150 to 200 m (490 to 660 ft) below sea level while its southern extent is delimited by the Davis Strait aquatic sill roughly 600 m (2,000 ft) below sea level.[31]
Lancaster Basin is a half-graben forming the eastern mouth of the larger Parry Submarine Rift Valley.[27][8] It contains several block faulted structures and is filled with Mesozoic, Tertiary and Quaternary sediments.[29]
Barrow Basin is a prominent topographic depression and, like Lancaster Basin to the east, represents a half-graben of the Parry Submarine Rift Valley bounded on the north by high-angle normal faults. Non-marine Tertiary sediments up to approximately 1,100 m (3,600 ft) thick exist in the Barrow Basin.[32]
Lady Franklin Basin is one of the deepest basins offshore
Labrador Basin is an immense structural
Situated on Bylot Island and northern Baffin Island are a series of grabens and horsts that constitute the North Baffin Rift Zone. These structures formed intermittently from late Proterozoic to early Tertiary time, with the latest period of reactivation having taken place during the Eurekan Rifting Episode.[27]
Igneous petrology
Like many rifts worldwide, the Canadian Arctic Rift System was a site of
The Sverdrup Basin Magmatic Province in the east-central Sverdrup Basin is an Early Cretaceous to Paleogene large igneous province. It consists of pyroclastic deposits, thin lava flows, flood basalts and central volcanoes, as well as hypabyssal sills and dikes. Argon–argon dating of mafic igneous rocks from the province suggests that mafic magmatism peaked during two time intervals. The first time interval between 127 and 129 million years ago was characterized by the widespread intrusion of sills and dikes. Flood basalt volcanism during the second time interval between 92 and 98 million years ago was coeval with the development of the proto-Arctic Ocean. Sills and flood basalts of the Sverdrup Basin Magmatic Province are well-exposed in the Princess Margaret Range, a north–south trending mountain range extending across the length of Axel Heiberg Island. Basaltic lava flows occur in the Isachsen and Strand Fiord formations. Sills intrude the entire Mesozoic succession and are particularly abundant in the Triassic shales of the Blaa Mountain Group.[38]
A volcanic suite of Eocene age occurs in the Freemans Cove area of Bathurst Island. It is confined to the Southeast Bathurst Fault Zone, consisting of sills, dikes,
A major episode of Tertiary magmatism related to the opening of Baffin Bay emplaced mafic intrusions and volcanic rocks on Baffin Island and in West Greenland.
Oceanography
Extending through northern North America is a major seaway system connecting the Atlantic and Arctic oceans. This system was created by geological events of the Canadian Arctic Rift System and is still controlled by rift structures. It includes the Northwest Passage, which cuts through the Labrador Sea, Baffin Bay, Parry Channel and other channels within and adjacent to the Arctic Archipelago.[4] Inflow from the Atlantic Ocean and outflow from the Arctic Ocean has resulted in ocean currents flowing along the rifted continental margins of West Greenland, Baffin Island and Labrador.[42][43]
Waterbodies
Nares Strait lies within the Nares Submarine Rift Valley between North Greenland and Ellesmere Island.[44] It is a north-northeast trending channel connecting Baffin Bay in the south with the Arctic Ocean in the north. From south to north, the strait includes Smith Sound, Kane Basin, Kennedy Channel, Hall Basin and Robeson Channel.[45]
Parry Channel is a waterway in the Arctic Archipelago formed by the Parry Submarine Rift Valley.[26][46] It consists of four waterbodies: Lancaster Sound, M'Clure Strait, Viscount Melville Sound and Barrow Strait. With a length of over 1,100 km (680 mi), Parry Channel connects Baffin Bay in the east with Beaufort Sea in the west. The north and south sides of the channel are opened by a number of smaller waterways. Of these, Admiralty Inlet penetrates deep into the northwestern part of Baffin Island from the south side of Lancaster Sound. At the west end of Parry Channel, Prince of Wales Strait leads southwest from the junction of Viscount Melville Sound and M'Clure Strait into Amundsen Gulf.[47]
Jones Sound occupies a rift valley between Ellesmere Island in the north and Devon Island in the south.[1][48] It has an east–west length of roughly 210 km (130 mi) and a width varying from about 47 to 116 km (29 to 72 mi).[48] Surface data and the existence of corresponding seaward-dropping fault blocks on the north coast of Devon Island and on the south coast of Ellesmere Island suggest that Jones Sound may be a graben structure.[49]
Baffin Bay is a 1,200 km (750 mi) long and 500 km (310 mi) wide semi-enclosed sea surrounded by Ellesmere Island and Devin Island in the north, Greenland in the east and Baffin Island in the west.[31] It is an example of a failed proto-ocean, centrally underlain by oceanic crust of the Baffin Basin which is surrounded by extended continental crust that varies approximately 25 to 30 km (16 to 19 mi) thick.[1][50][51] Connected to the North Atlantic Ocean in the south through Davis Strait and to the Arctic Ocean in the north through Nares Strait, Jones Sound and Lancaster Sound, the ocean water in Baffin Bay is highly stratified. The surface water, of Arctic origin, is cold and fresh. Below the Arctic layer is a layer of Atlantic origin, which is warm and saline. Below the Atlantic layer are Baffin Bay Deep Water and Baffin Bay Bottom Water, both of which are cold and saline. On a net annual basis, approximately 1.7 Sv of water flows out of the Arctic Ocean through Baffin Bay, making the bay the second most important conduit between the Arctic Ocean and the rest of the world's oceans.[31]
The Labrador Sea is an arm of the North Atlantic Ocean occupying the Labrador Basin between Greenland and Labrador.
Crozier Strait between Bathurst Island and Little Cornwallis Island dominates the Crozier Strait Fault Zone.[25] It is a narrow but extremely deep body of water measuring roughly 30 km (19 mi) long and 8 km (5.0 mi) wide at its narrowest point.[58] The strait, an arm of the Arctic Ocean, connects Queens Channel in the north with McDougall Sound in the south.[59]
Prince Regent Inlet occupies a southern branch of the Lancaster Aulacogen between Baffin Island and Somerset Island.[27] It is a deep waterbody measuring 64 km (40 mi) wide at its northern end and over 105 km (65 mi) at its southern end. The inlet connects Lancaster Sound in the north with the Gulf of Boothia in the south.[60]
Davis Strait is a narrow and relatively shallow area connecting Baffin Bay in the north with the Labrador Sea in the south. It varies in width from 300 km (190 mi) to over 950 km (590 mi), with the shallowest waters found along the Davis Sill. This aquatic sill is a submarine ridge 350 to 550 m (1,150 to 1,800 ft) below sea level extending from Baffin Island in the west to Greenland in the east.[61] Unlike Baffin Bay and the Labrador Sea, Davis Strait is bounded by volcanic passive margins. Paleogene volcanic rocks are exposed on both sides of the strait: the Disko-Svartenhuk area of West Greenland in the east and near Cape Dyer on Baffin Island in the west.[19]
Hudson Strait–Evans Strait–Foxe Channel is a 1,000-kilometre-long (620 mi) waterbody connecting Hudson Bay and Foxe Basin in the west-northwest with the Labrador Sea in the south-southeast. It comprises several half-grabens that may have developed during the initial stages of extension in the Labrador Sea. They form sub-basins that are controlled by steeply-dipping normal faults, which predominately dip toward the north.[62]
Ocean currents
West Greenland Current originates from the movement of Atlantic water flowing around the southern point of Greenland caused by the East Greenland and Irminger currents.[42][63][64] It transports freshwater into the Labrador Sea, influencing the formation of Labrador Sea Water.[57] The current flows north along the coast of West Greenland, steadily losing volume through low-velocity westward branching as water is fed into the anticyclonic circulatory system of the Labrador Sea.[64] Just south of Davis Sill, a major westward branching occurs, the remainder of the West Greenland Current continuing across Davis Sill into Baffin Bay where it eventually peters out.[42][64]
Baffin Island Current consists mainly of relatively fresh Arctic waters that enter northern Baffin Bay through Nares Strait, Jones Sound and Lancaster Sound.[65] First detectable off Devon Island, the Baffin Island Current flows south along the length of western Baffin Bay and the western half of Davis Strait.[30][66] It then divides at Hudson Strait; one branch sets westward along the northern half of Hudson Strait; another branch continues southward towards the Labrador Sea.[66][67]
See also
- Geology of Greenland
- Geology of Newfoundland and Labrador
- Geology of the Northwest Territories
- Geology of Nunavut
- List of largest rifts, canyons and valleys in the Solar System
- Opening of the North Atlantic Ocean
References
- ^ a b c d Kerr, J. W. (1973). "Canadian Arctic Rift System—A Summary". Arctic Geology. 19. American Association of Petroleum Geologists: 587.
- ISSN 1911-4850.
- ^ Nunami Stantec Limited (2018). "Strategic Environmental Assessment for Baffin Bay and Davis Strait: Environmental Setting and Review of Potential Effects of Oil and Gas Activities". Nunavut Impact Review Board: 3.56.
{{cite journal}}
: Cite journal requires|journal=
(help) - ^ ISBN 978-1-4757-1250-6.
- ^ a b c d Jollimore, Wayne (1986). Analyses of Dyke Swarms within the Sverdrup Basin, Queen Elizabeth Islands (BSc). Halifax, Nova Scotia: Dalhousie University. p. 8.
- ^ ISSN 0956-540X.
- ^ ISSN 0956-540X.
- ^ ISSN 0956-540X.
- ISSN 0148-0227.
- ISSN 1365-3121.
- ISBN 978-1-4612-9005-6.
- ISSN 0094-8276.
- ^ "The 1933 Baffin Bay earthquake". Natural Resources Canada. 2016-02-10. Retrieved 2018-11-18.
- ISSN 0956-540X.
- ^ Jauer, Christopher D.; Oakey, Gordon N.; Williams, Graham; Wielens, Hans (2012). "The Saglek Basin in the Labrador Sea; past exploration history, current estimates and future opportunities". Calgary: GeoConvention: 2.
{{cite journal}}
: Cite journal requires|journal=
(help) - ISSN 0007-4802.
- ^ ISSN 1604-8156.
- ^ Peace, Alexander Lewis (2016). Structural inheritance and magmatism during continental breakup in West Greenland and Eastern Canada (PhD). Durham, England: Durham University. p. 242.
- ^ ISSN 0148-0227.
- ISSN 0956-540X.
- S2CID 201084292.
- ^ ISSN 1480-3313.
- ISSN 0148-0227.
- ^ doi:10.4095/222524.
- ^ ISSN 0007-4802.
- ^ ISSN 0080-4614.
- ^ a b c d e f Kerr, J. Wm. (1979). "Structural Framework of Lancaster Aulacogen, Arctic Canada". Open File 619. Geological Survey of Canada: 4, 26, 28, 29, 31, 36.
- ISSN 2169-9356.
- ^ ISBN 0-662-23120-1.
- ^ ISSN 0711-6764.
- ^ ISBN 1-57958-439-X.
- ^ Bornhold, B. D.; Lewis, C. F. M. (1976). "Marine Geology of Western Lancaster Sound". 1. Geological Association of Canada: 81.
{{cite journal}}
: Cite journal requires|journal=
(help) - ^ S2CID 130442048.
- ISBN 978-1-86239-226-7.
- ^ ISBN 978-94-009-6247-7.
- ISSN 0004-0843.
- ISSN 1553-040X.
- ISBN 978-0-8137-2483-6.
- ISBN 978-87-635-1150-6.
- ^ a b Kristjansson, L. G.; Deutsch, E. R. (1973). "Magnetic Properties of Rock Samples from the Baffin Bay Coast". Earth Science Symposium on Offshore Eastern Canada. Geological Survey of Canada. pp. 545, 546.
- ISSN 0016-7568.
- ^ ISBN 0-08-037953-2.
- )
- ISSN 0007-4802.
- ISBN 1-57785-753-4.
- ISBN 978-1-4612-8022-4.
- ^ Dodd, G. J.; Benson, G. P.; Watts, D. T. (1976). Arctic Pilot: Davis Strait and Baffin Bay with the west and north-west coasts of Greenland, the north coast of Canada including Hudson Bay and the Arctic Archipelago. Vol. 3 (6 ed.). Hydrographer of the Navy. p. 305.
- ^ Queen's Printer. p. 365.
- ^ Christie, R. L. (1978). "A Structural Reconnaissance of Eastern Devon Island, Arctic Archipelago". Geological Survey of Canada: 20.
{{cite journal}}
: Cite journal requires|journal=
(help) - ISSN 0148-0227.
- ISSN 0956-540X.
- ISBN 0-07-025010-3.
- ^ Tanner, V. (1944). "Outlines of the geography, life and customs of Newfoundland-Labrador". Acta Geographica. 8. Helsingfors: 255.
- )
- ISSN 1042-8275.
- ^ Yashayaev, I. V.; Clarke, R. A.; Lazier, J. R. N. (2000). "Recent Decline of the Labrador Sea Water" (PDF). International Council for the Exploration of the Sea. p. 1. Retrieved 2019-02-24.
- ^ ISSN 2169-9275.
- ISSN 0317-2244.
- ISSN 0004-0843.
- ISBN 90-247-2979-3.
- ISSN 1499-3848.
- ISSN 0264-8172.
- ISSN 0079-6611.
- ^ a b c d e United States Hydrographic Office (1942). Sailing Directions for Newfoundland: Including the Coast of Labrador from Long Point to St. Lewis Sound (6 ed.). Washington, D.C.: United States Government Publishing Office. p. 55.
- ISSN 0711-6764.
- ^ ISBN 0-7735-0925-9.
- ^ Mussells, Olivia (2015). Observing Pressured Sea Ice in the Hudson Strait Using RADARSAT: Implications for Shipping (Thesis). University of Ottawa. p. 8.