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Ottawa-Bonnechere Graben

April 10, 2024

The Ottawa-Bonnechere Graben (also known as the Ottawa Graben) is a geological structure that coincides with a 55 km (34 mi) wide topographic depression extending from near Montréal through Ottawa. It is part of the Saint Lawrence rift system that also includes the seismically active Saguenay graben.[1] This rift valley was formed when the Earth's crust moved downward about a kilometre between two major fault zones known as the Mattawa and Petawawa faults.[2]

Ottawa-Bonnechere Graben
Graben
Map of the Ottawa-Bonnechere and Timiskaming grabens
LocationOntario and Quebec, Canada
Part ofSaint Lawrence rift system
AgeLate Proterozoic to Early Paleozoic
GeologyGraben
Dimensions
 • Length700 km (435 mi)

Geography edit

The Ottawa-Bonnechere Graben measures about 700 km (435 mi), running from the Montreal area on the east to near Sudbury and Lake Nipissing on the west.[2] On the east, it joins the Saint Lawrence rift system, a half-graben which extends more than 1000 km along the Saint Lawrence River valley and links the Ottawa and Saguenay Graben.[3][4]

The 200 km (124 mi) segment of the Ottawa-Bonnechere Graben west of Ottawa was the first to be recognized as a graben. Since then, it has been traced west to Lake Nipissing, and northwestwards from the confluence of the Mattawa and Ottawa Rivers up the valley of the latter stream to Lake Timiskaming and the Montreal River valley. This latter branch is the Timiskaming Graben. At the rifts' western termini, the main faults split into divergent smaller faults.[2] The graben has been interpreted as a Late Proterozoic to Early Paleozoic failed arm of the Iapetus Ocean, the precursor to the Atlantic Ocean.[2][3] The main Ottawa-Bonnechere Graben is associated with collapse of the regional carbonate platform and formation of deep water shale basins by ~452 mya (million years ago); similar events formed the Temiskaming Graben ~449–451 mya.[5] These grabens were reactivated during the breakup of supercontinent Pangaea some 150 mya.[6]

Geology edit

 
Three of the central Monteregian Hills viewed from space (from left: Mont Saint-Hilaire, Mont Rougemont and Mont Yamaska).

Since the Late Proterozoic to Early Paleozoic, erosion has removed the volcanic peaks, exposing a number of relic volcanic pipes, such as Callander Bay and the Manitou Islands in Lake Nipissing.[7]

These features are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. Batholiths and dikes were also exposed by erosion, such as the Timber Lake, Mulock, West Arm, Powassan and Bonfield batholiths.[7] The expressions of a thick pile of dominantly mafic, bimodal volcanics and the Tibbit Hill volcanics in the Humber Zone of the Quebec Appalachians are believed to be related to the formation of the Ottawa-Bonnechere Graben.[2] The precise age of these volcanics is unknown but they are either early Cambrian and late Precambrian.[2] This volcanism was probably coeval with the emplacement of the Grenville dike swarm.[citation needed]

Minor but significant igneous activity occurred during the Mesozoic era, including kimberlite emplacement during the Jurassic period, and the development of alkalic intrusions along the Ottawa-Bonnechere Graben and elsewhere in Ontario. This second episode of alkalic volcanism occurred along the eastern part of the graben in the early Cretaceous.

The products of this event are the Monteregian Hills in Montérégie, Quebec. These are thought to have formed as a result of the North American Plate sliding westward over a long-lived center of upwelling magma called the New England hotspot,[8] and is the eroded remnants of intrusive stocks.

These intrusive stocks have been variously interpreted as the feeder intrusions of long extinct volcanoes, which would have been active about 125 million years ago,[2][9][10] or as intrusives that never breached the surface in volcanic activity.[11] Of all these features, Mont Saint-Hilaire is the best known as a source of rare specimens.

 
View of the Ottawa Valley from the Gatineau Hills

Along the northern side of the Ottawa-Bonnechere Graben lies a dramatic escarpment that forms the southern edge of the Gatineau Hills. This escarpment, called the Eardley Escarpment, makes this part of the graben an attractive location for rock climbers and hikers, offering a beautiful view of the relatively flat fields below, which extend to the Ottawa River.

On or near a branch of the Ottawa-Bonnechere Graben lies the Brent impact crater.[7] It is 3.8 km (2.4 mi) in diameter and the age is estimated about 400 million years (Early Devonian). The impact crater, which was first recognized in 1951 from aerial photographs, formed in Precambrian gneisses. [12] Geophysical and diamond drilling investigations show that the crater has a present depth of about 425 m (1,390 ft) but is partly filled with sedimentary rocks with a thickness of about 274 m (899 ft).[12] The rocks beneath the crater floor are thoroughly fragmented over a depth of about 610 m (2,000 ft). Like the similar Pingualuit crater, the Brent crater is attributed to the high speed impact of a giant meteorite. It is calculated that the impact released energy equaling 250 megatons of TNT and occurred when this area was probably covered by a shallow sea.

History edit

The depressions formed by the graben across the rugged Canadian Shield were a spillway for the Great Lakes after the last ice age.[13] Later they became a thoroughfare for exploration and trade. These depressions now contain the Ottawa River and its tributary the Mattawa, which rises at Trout Lake near Lake Nipissing. The latter is the source of the French River, which drains into Lake Huron. This water route, with few portages, connected Lake Huron and the Saint Lawrence River by a much shorter route than through the lower Great Lakes. It was the mainline of the French-Canadian voyageurs engaged in the fur trade; they took canoes on the waterways along this route from Montreal to the upper Great Lakes and the pays d'en haut—the "upper country" in the old Northwest.[13][14] The valley of the Ottawa and Montreal Rivers and Lake Timiskaming was also part of a branch route to James Bay in the days of the fur brigades.[15] The valleys are now used by more modern forms of transportation, including the Canadian Pacific Railway and the Trans-Canada Highway.[16]

After the arrival of European settlers in North America, the Mattawa River was an important transportation corridor for native peoples of the region and formed part of the water route leading west to Lake Superior in the days of the fur trade. Canoes travelling north up the Ottawa turned left to enter the Mattawa, reaching Lake Nipissing by way of "La Vase Portage", an 11 km (7 mi) stretch of water and portages. In the 19th century, the river provided access to large untouched stands of white pine. The river was also used to transport logs to sawmills. While logging is still an important industry in this region, almost the full length of the river has been designated as a Canadian Heritage River, and as such, its shores are now protected from further development and logging. Today, the river and lakes are mainly used for recreation.

See also edit

References edit

  1. ^ Rimando, Rolly E.; Benn, Keith (2005). "Evolution of faulting and paleo-stress field within the Ottawa graben, Canada". Journal of Geodynamics. 39 (4): 337–360. Bibcode:2005JGeo...39..337R. doi:10.1016/j.jog.2005.01.003.
  2. ^ a b c d e f g Kumarapeli, S. (1981). "Origin and development of the Ottawa Graben". Processes of Planetary Rifting. 457: 114. Bibcode:1981LPICo.457..114K., pages 114, 115, and 116.
  3. ^ a b Tremblay, Alain; Lemieux, Yvon (2001). "Supracrustal Faults of the St. Lawrence rift System between Cap Tourments and Baie-Saint-Paul, Quebec" (PDF). Current Research 2001-D15. Geological Survey of Canada. Retrieved 2007-06-20.
  4. ^ . Archived from the original on 2008-04-10. Retrieved 2007-12-15.
  5. ^ Sajal, Sharma; Dix, George R.; Coniglio, Mario; Achad, Aicha; Riva, John F. V. (2005-09-27). (PDF). Calgary, Alberta: searchanddiscovery.net. Archived from the original (PDF) on 2008-04-10. Retrieved 2007-12-16. Poster presentation at AAPG Annual Convention, Calgary, Alberta, June 19–22, 2005, and abstract.
  6. ^ The Ottawa Bonnechere Graben Retrieved on 2007-11-18
  7. ^ a b c . Archived from the original on 2007-12-20. Retrieved 2007-12-15.
  8. ^ Eaton, David W.; Frederiksen, Andrew (2007). "Inferred track of the Great Meteor hotspot". Nature. 446 (7134): 428–431. doi:10.1038/nature05675. PMID 17377580.
  9. ^ . Archived from the original on 2006-05-03. Retrieved 2007-11-16.
  10. ^ . Geoscape Montreal. Natural Resources Canada. Archived from the original on 2009-04-26. Retrieved 2006-11-16.
  11. ^ . McGill University. Archived from the original on 2007-12-20. Retrieved 2007-12-16.
  12. ^ a b Currie, K.L.; Shafiqullah, M. (1967-08-12). "Carbonatite and Alkaline Igneous Rocks in the Brent Crater, Ontario". Letters to Nature. 215 (5102): 725–726. Bibcode:1967Natur.215..725C. doi:10.1038/215725a0.
  13. ^ a b . National Heritage Information Center. Ontario Ministry of National Resources. 2005-06-05. Archived from the original on November 9, 2005. Retrieved 2007-12-15.
  14. ^ Morse, Eric (1979). Fur Trade Routes of Canada. Minoqua, WI: NorthWord Press. pp. 48–61. ISBN 978-1-55971-045-9.
  15. ^ Morse, Eric (1979). Fur Trade Routes of Canada. Minoqua, WI: NorthWord Press. pp. 67–69. ISBN 978-1-55971-045-9.
  16. ^ (PDF). Archived from the original (PDF) on 2008-04-10. Retrieved 2007-12-15.. Lake Nissiping area, showing Canadian Pacific Railway, Highway 17, and other routes.

External links edit

  • , a Canadian Geographic article about the valley
  • at Great Canadian Rivers
  • , G'Day G'Day and Welcome to the Valley

45°34′36″N 76°54′58″W / 45.5767°N 76.9162°W / 45.5767; -76.9162

April 10, 2024
ottawa, bonnechere, graben, also, known, ottawa, graben, geological, structure, that, coincides, with, wide, topographic, depression, extending, from, near, montréal, through, ottawa, part, saint, lawrence, rift, system, that, also, includes, seismically, acti. The Ottawa Bonnechere Graben also known as the Ottawa Graben is a geological structure that coincides with a 55 km 34 mi wide topographic depression extending from near Montreal through Ottawa It is part of the Saint Lawrence rift system that also includes the seismically active Saguenay graben 1 This rift valley was formed when the Earth s crust moved downward about a kilometre between two major fault zones known as the Mattawa and Petawawa faults 2 Ottawa Bonnechere GrabenGrabenMap of the Ottawa Bonnechere and Timiskaming grabensLocationOntario and Quebec CanadaPart ofSaint Lawrence rift systemAgeLate Proterozoic to Early PaleozoicGeologyGrabenDimensions Length700 km 435 mi Contents 1 Geography 2 Geology 3 History 4 See also 5 References 6 External linksGeography editThe Ottawa Bonnechere Graben measures about 700 km 435 mi running from the Montreal area on the east to near Sudbury and Lake Nipissing on the west 2 On the east it joins the Saint Lawrence rift system a half graben which extends more than 1000 km along the Saint Lawrence River valley and links the Ottawa and Saguenay Graben 3 4 The 200 km 124 mi segment of the Ottawa Bonnechere Graben west of Ottawa was the first to be recognized as a graben Since then it has been traced west to Lake Nipissing and northwestwards from the confluence of the Mattawa and Ottawa Rivers up the valley of the latter stream to Lake Timiskaming and the Montreal River valley This latter branch is the Timiskaming Graben At the rifts western termini the main faults split into divergent smaller faults 2 The graben has been interpreted as a Late Proterozoic to Early Paleozoic failed arm of the Iapetus Ocean the precursor to the Atlantic Ocean 2 3 The main Ottawa Bonnechere Graben is associated with collapse of the regional carbonate platform and formation of deep water shale basins by 452 mya million years ago similar events formed the Temiskaming Graben 449 451 mya 5 These grabens were reactivated during the breakup of supercontinent Pangaea some 150 mya 6 Geology edit nbsp Three of the central Monteregian Hills viewed from space from left Mont Saint Hilaire Mont Rougemont and Mont Yamaska Since the Late Proterozoic to Early Paleozoic erosion has removed the volcanic peaks exposing a number of relic volcanic pipes such as Callander Bay and the Manitou Islands in Lake Nipissing 7 These features are subterranean geological structures formed by the violent supersonic eruption of deep origin volcanoes Batholiths and dikes were also exposed by erosion such as the Timber Lake Mulock West Arm Powassan and Bonfield batholiths 7 The expressions of a thick pile of dominantly mafic bimodal volcanics and the Tibbit Hill volcanics in the Humber Zone of the Quebec Appalachians are believed to be related to the formation of the Ottawa Bonnechere Graben 2 The precise age of these volcanics is unknown but they are either early Cambrian and late Precambrian 2 This volcanism was probably coeval with the emplacement of the Grenville dike swarm citation needed Minor but significant igneous activity occurred during the Mesozoic era including kimberlite emplacement during the Jurassic period and the development of alkalic intrusions along the Ottawa Bonnechere Graben and elsewhere in Ontario This second episode of alkalic volcanism occurred along the eastern part of the graben in the early Cretaceous The products of this event are the Monteregian Hills in Monteregie Quebec These are thought to have formed as a result of the North American Plate sliding westward over a long lived center of upwelling magma called the New England hotspot 8 and is the eroded remnants of intrusive stocks These intrusive stocks have been variously interpreted as the feeder intrusions of long extinct volcanoes which would have been active about 125 million years ago 2 9 10 or as intrusives that never breached the surface in volcanic activity 11 Of all these features Mont Saint Hilaire is the best known as a source of rare specimens nbsp View of the Ottawa Valley from the Gatineau HillsAlong the northern side of the Ottawa Bonnechere Graben lies a dramatic escarpment that forms the southern edge of the Gatineau Hills This escarpment called the Eardley Escarpment makes this part of the graben an attractive location for rock climbers and hikers offering a beautiful view of the relatively flat fields below which extend to the Ottawa River On or near a branch of the Ottawa Bonnechere Graben lies the Brent impact crater 7 It is 3 8 km 2 4 mi in diameter and the age is estimated about 400 million years Early Devonian The impact crater which was first recognized in 1951 from aerial photographs formed in Precambrian gneisses 12 Geophysical and diamond drilling investigations show that the crater has a present depth of about 425 m 1 390 ft but is partly filled with sedimentary rocks with a thickness of about 274 m 899 ft 12 The rocks beneath the crater floor are thoroughly fragmented over a depth of about 610 m 2 000 ft Like the similar Pingualuit crater the Brent crater is attributed to the high speed impact of a giant meteorite It is calculated that the impact released energy equaling 250 megatons of TNT and occurred when this area was probably covered by a shallow sea History editThe depressions formed by the graben across the rugged Canadian Shield were a spillway for the Great Lakes after the last ice age 13 Later they became a thoroughfare for exploration and trade These depressions now contain the Ottawa River and its tributary the Mattawa which rises at Trout Lake near Lake Nipissing The latter is the source of the French River which drains into Lake Huron This water route with few portages connected Lake Huron and the Saint Lawrence River by a much shorter route than through the lower Great Lakes It was the mainline of the French Canadian voyageurs engaged in the fur trade they took canoes on the waterways along this route from Montreal to the upper Great Lakes and the pays d en haut the upper country in the old Northwest 13 14 The valley of the Ottawa and Montreal Rivers and Lake Timiskaming was also part of a branch route to James Bay in the days of the fur brigades 15 The valleys are now used by more modern forms of transportation including the Canadian Pacific Railway and the Trans Canada Highway 16 After the arrival of European settlers in North America the Mattawa River was an important transportation corridor for native peoples of the region and formed part of the water route leading west to Lake Superior in the days of the fur trade Canoes travelling north up the Ottawa turned left to enter the Mattawa reaching Lake Nipissing by way of La Vase Portage an 11 km 7 mi stretch of water and portages In the 19th century the river provided access to large untouched stands of white pine The river was also used to transport logs to sawmills While logging is still an important industry in this region almost the full length of the river has been designated as a Canadian Heritage River and as such its shores are now protected from further development and logging Today the river and lakes are mainly used for recreation See also editMidcontinent Rift System Geological rift in the center of the North American continent Ottawa Valley Valley in Ontario and Quebec in Canada Volcanology of Canada Volcanic activity in CanadaPages displaying short descriptions of redirect targets Volcanology of Eastern Canada volcanic areas and lava formations in Eastern CanadaPages displaying wikidata descriptions as a fallbackReferences edit Rimando Rolly E Benn Keith 2005 Evolution of faulting and paleo stress field within the Ottawa graben Canada Journal of Geodynamics 39 4 337 360 Bibcode 2005JGeo 39 337R doi 10 1016 j jog 2005 01 003 a b c d e f g Kumarapeli S 1981 Origin and development of the Ottawa Graben Processes of Planetary Rifting 457 114 Bibcode 1981LPICo 457 114K pages 114 115 and 116 a b Tremblay Alain Lemieux Yvon 2001 Supracrustal Faults of the St Lawrence rift System between Cap Tourments and Baie Saint Paul Quebec PDF Current Research 2001 D15 Geological Survey of Canada Retrieved 2007 06 20 Map Archived from the original on 2008 04 10 Retrieved 2007 12 15 Sajal Sharma Dix George R Coniglio Mario Achad Aicha Riva John F V 2005 09 27 Records of Punctuated Tectonism in Platform Interior Graben Systems Ontario Canada Far Flung from Contemporaneous Taconic Orogenesis in the Northern Appalachians PDF Calgary Alberta searchanddiscovery net Archived from the original PDF on 2008 04 10 Retrieved 2007 12 16 Poster presentation at AAPG Annual Convention Calgary Alberta June 19 22 2005 and abstract The Ottawa Bonnechere Graben Retrieved on 2007 11 18 a b c Background Geology of the North Bay area Archived from the original on 2007 12 20 Retrieved 2007 12 15 Eaton David W Frederiksen Andrew 2007 Inferred track of the Great Meteor hotspot Nature 446 7134 428 431 doi 10 1038 nature05675 PMID 17377580 A Hundred Million Year History of the Corner Rise and New England Seamounts Archived from the original on 2006 05 03 Retrieved 2007 11 16 The Monteregian Hills Igneous Intrusions Geoscape Montreal Natural Resources Canada Archived from the original on 2009 04 26 Retrieved 2006 11 16 Geology of Gault Nature Reserve Mont St Hilaire McGill University Archived from the original on 2007 12 20 Retrieved 2007 12 16 a b Currie K L Shafiqullah M 1967 08 12 Carbonatite and Alkaline Igneous Rocks in the Brent Crater Ontario Letters to Nature 215 5102 725 726 Bibcode 1967Natur 215 725C doi 10 1038 215725a0 a b Natural Areas Report Mattawa River National Heritage Information Center Ontario Ministry of National Resources 2005 06 05 Archived from the original on November 9 2005 Retrieved 2007 12 15 Morse Eric 1979 Fur Trade Routes of Canada Minoqua WI NorthWord Press pp 48 61 ISBN 978 1 55971 045 9 Morse Eric 1979 Fur Trade Routes of Canada Minoqua WI NorthWord Press pp 67 69 ISBN 978 1 55971 045 9 Geological Highway map PDF Archived from the original PDF on 2008 04 10 Retrieved 2007 12 15 Lake Nissiping area showing Canadian Pacific Railway Highway 17 and other routes External links editWelcome to the Ottawa Valley a Canadian Geographic article about the valley Ottawa River article at Great Canadian Rivers Preview of the Canadian Geographic article G Day G Day and Welcome to the Valley45 34 36 N 76 54 58 W 45 5767 N 76 9162 W 45 5767 76 9162 Retrieved from https en wikipedia org w index php title Ottawa Bonnechere Graben amp oldid 1187836686, wikipedia, wiki, book, books, library,

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