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Geology of North America

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This article discusses the regional geology of North America as outlined by this picture. This may or may not overlap with other definitions of "North America".

The geology of North America is a subject of regional geology and covers the North American continent, third-largest in the world. Geologic units and processes are investigated on a large scale to reach a synthesized picture of the geological development of the continent.

The divisions of regional geology are drawn in different ways, but are usually outlined by a common geologic history, geographic vicinity or political boundaries. The regional geology of North America usually encompasses the geographic regions of Alaska, Canada the continental United States, Mexico, Central America, and the Caribbean[citation needed]. The parts of the North American Plate that are not occupied by North American countries are usually not discussed as part of the regional geology. The regions that are not geographically North American but reside on the North American Plate include Siberia (see the Geology of Russia),[1] Greenland, Iceland and Bermuda. A discussion of North American geology can also include other continental plates including the Cocos and Juan de Fuca plates being subducted beneath western North America.

North American Craton

Canadian Shield

Main article: Canadian Shield
On a map showing only metamorphic rocks, the Canadian Shield forms a circular pattern north of the Great Lakes around Hudson Bay.

The Canadian Shield is a large area of Archean through Proterozoic igneous and metamorphic rocks in eastern Canada and north central and northeastern United States.

The earliest part of the shield is metamorphosed Archean rocks, originally volcanic in origin. Numerous terranes were accreted onto this Archean core during the Proterozoic to form the Canadian Shield.[2] The southern Archean province is the Superior Craton, it is formed by the combination of a greenstone-granite and a gneiss terrane.[3] The margins of the Canadian Shield have been covered by sedimentary rocks, such as in Michigan where a series of sediments has filled in the Michigan Basin.[2] The exposed sections are often where glaciers have removed this overlying regolith to reveal the underlying glacially scarred crystalline rock.[4]

Stable platform

The North American craton
Main article: Laurentia

The stable platform is an area in which the North American Craton forms a basement and is covered by sediment. This area now forms much of the great plains and the slope of the Appalachians below the mountains proper.[5] This area has been covered by a shallow inland sea, which became the site of deposition for most of the overlying sedimentary rock. The sea receded as the continent rose becoming covered by stream, lake, and wind deposits.[6] Orogenies in the surrounding provinces have had little effect on the craton, making it an epeirogenic region,[7] and, as such, the stable platform is mostly a crystalline basement, covered by sedimentary rocks, interrupted only by occasional domes, such as the Cincinnati Arch, Wisconsin Dome, and Ozark Dome.[5]

Midcontinent rift system

One billion years ago, the Midcontinent rift system began to extend along a 2,000 kilometres (1,200 mi) path,[8] across both the Canadian Shield and the Stable Platform; however, the rift failed, and then crustal movement reversed and a range formed, which eroded, forming basins on either side of a horst. These rocks have been buried beneath sediment in many areas, but are exposed in some areas, especially around Lake Superior.[9]

Grenville Orogen

The Grenville Orogen developed during the Proterozoic along eastern and southern margin of the North American Craton.[10][11] The largest outcrop of Grenville age rocks is an approximately 400 kilometres (250 mi) wide band southeast of the Grenville Front which stretches from the central Labrador coast southwest across southern Quebec and southeastern Ontario to Georgian Bay on Lake Huron. The southeastern boundary of this area is approximately the St. Lawrence River. Rocks of the Grenville outcrop in the Adirondack Mountains of northern New York and throughout the Appalachians.[11] The Llano Uplift of central Texas and the Franklin and Hueco Mountains of west Texas have been correlated with the Grenville as have occurrences in Mexico.[11]

Appalachian Orogen

Main article: Geology of the Appalachians
Map of Appalachian geological provinces

The fold and thrust belt of the Appalachians is continuously exposed for 2,000 kilometres (1,200 mi) from Pennsylvania to Alabama.[5] In the south, it extends under the coastal plain, but is covered by Mesozoic sediments.[12] North of this fold and thrust belt, the Acadian Orogen of the middle Devonian is an area where deformation has exposed granite plutons.[13] The center of the range is a pair of provinces running north and south parallel to each other, the eastern Blue Ridge Province and the western Valley and Ridge provinces. These are surrounded by the Appalachian Plateau on the west, and the Piedmont Province to the east.[14] Faulting extends throughout the region and is caused by numerous spatially and temporally varied sources.[15]

Inliers of Late Mesoproterozoic age are present on the west of the core of the Appalachians, and these inliers are associated with the Grenville orogeny.[16] During the Proterozoic terranes were accreted onto the province.[17] During the Taconic orogeny 445 to 435 million years ago, accretion continued, an island arc collided with the North American continent, and mountains were raised. These mountains slowly eroded and deposited sediment into the Catskill delta, stretching from New York to Pennsylvania.[18]

Piedmont

Main article: Geology of the Piedmont

The eastern portion of the orogen is made up of the Piedmont plateau, a 150 to 300 metres (490 to 980 ft) elevation area composed of Paleozoic marine and volcanic sediments deformed into crystalline metamorphic rocks and intruded by granite domes.[19]

During the Proterozoic a series of terranes were accreted onto the North American craton, forming the Piedmont of the central Appalachians.[20] Following the Grenville orogeny, mountains eroded, and the sediments from this erosion were deposited below the mountains.[21] The bedrock of the plateau formed about 470 million years ago during the Taconic orogeny, when a volcanic island arc collided with the ancestral North American Continent.[22]

Passive Margin

As the Atlantic separated the Atlantic Coast turned from an active margin into a passive one. Terranes were no longer accreted onto the margin, instead, sediment eroded off the Appalachians began to be deposited on the coast, forming a coastal plain and continental shelf.[21] During the Jurassic and Triassic, marine and other sediment was deposited to form the atlantic coastline.[23] The sediment has formed a clastic wedge making up most of the coastal plain and continental shelf.[21]

The passive margin of the Gulf of Mexico is a series of sediments deposits from upland areas surrounding the margin. The environment of deposition for these sediments has changed, varying spatially and temporally. When the ocean level was high shallow marine deposits occurred; when they were low fluvial and deltaic deposits form the majority of mass.[24] From the Triassic until the early Jurassic, faulting localized as extension faulting and wrench faulting. As the basement subsided, sediment accumulated, during the Mesozoic and Cenozoic, forming the modern wedge, containing salt basins.[25]

The passive margin in eastern Mexico is made up of a series of basins. These basins are mostly igneous or metamorphic rocks covered by sediments,[26] except in the Burgos Basin, where Cenozoic Volcanism has occurred.[27] Much of the sediment is from erosion of the thrust belts west of the margin.[28]

The Yucatán Peninsula is a Cretaceous to Oligocene carbonate platform. Uplift started in the Oligocene and lasted till the Pleistocene. Today the platform is exposed and under the influence of karstification.[29]

American Cordillera

On a map showing only volcanic rocks, the west coast of North America shows a continues north-south striking structure, the American Cordillera.

The American cordillera extends roughly from the Great Plains westward to the Pacific Ocean, narrowing somewhat from north to south. It includes the Cascades, Sierra Nevada, and Basin and Range province; the Rocky Mountains are sometimes excluded from the cordillera proper, in spite of their tectonic history. The geology of Alaska is typical of that of the cordillera.

A rupture in Rodinia 750 million years ago formed a passive margin in the eastern Pacific Northwest. The breakup of Pangea 200 million years ago began the westward movement of the North American plate, creating an active margin on the western continent. As the continent drifted West, accretion of various terranes onto the west coast occurred.[30] As these accretions occurred, crustal shortening accompanied them during the Sevier orogeny and during the Mesozoic into the early Cenozoic, and was accompanied by faulting.[31] During the Cenozoic, crustal extension began accompanied by magmatism that came to characterize much of the area.[32]

Rocky Mountains

Main article: Geology of the Rocky Mountains

The Rocky Mountains were formed by a series of events, the last of which is the Laramide Orogeny.[33] One of the outstanding features of the Rocky Mountains is the distance of the range from a subducting plate; this has led to the theory that the Laramide Orogeny took place when the Farallon plate subducted at a low angle, causing uplift far from the margin under which the plate subducted.[34] The Rocky Mountains in the north are a series of carbonate and shale series overlying shale or argillite series between sandstone or carbonate layers.[35]

The Colorado Plateau is a stable region dating back at least 600 million years. As a relatively lowland, it had been a site of deposition for sediment that has eroded off surrounding orogens.[36] Then, during the Laramide Orogeny, the entire plateau uplifted until about six million years ago when erosion began to remove sediment from the plateau, which removed a load from the crust causing isostatic uplift and a second passive rise for the plateau.[37]

Intermontane Province

Main article: Geology of the Basin and Range Province
Cedar Breaks National Monument, Utah.

Between the Rocky Mountains and the coast ranges is an area dominated by extensional forces. The extension of this region has occurred both regionally and locally in events beginning in the Jurassic; however, most extension was localized until the mid Miocene. These local events occurred in the Jurassic, late Cretaceous, and one spanning from the Eocene until the Oligocene. Regional extension occurred during the middle of the Miocene from around 20 million years ago until 10 million years ago.[38]

The Basin and Range Province is a series of linear block fault mountains with adjacent sediment filled downfaulted valleys. The valley floors are made up thick sediment deposits which have covered the low bedrock sections and filled the valleys, so that the region is ridges spaced out by flat sediment valleys.[39]

Coast

Main article: Geology of the Pacific Coast Ranges

On the West coast of North America, the coast ranges and the coastal plain form the margin. Most of the land is made of terranes that have been accreted onto the margin. In the north, the insular belt is an accreted terrane, forming the margin. This belt extends from the Wrangellia Terrane in Alaska to the Chilliwack group of Canada.[30]

The timing of the accretion of the insular belt is uncertain, although the closure did not occur until at least 115 million years ago.[30] Other Mesozoic terranes that accreted onto the continent include the Klamath Mountains, the Sierra Nevada, and the Guerrero super-terrane of western Mexico.[40] 80 to 90 million years ago the subducting Farallon plate split and formed the Kula Plate to the North.[30] Many of the major batholiths date from the late Cretaceous.[40] As the Larmide Orogeny ended around 48 million years ago, the accretion of the Siletzia terrane began in the Pacific Northwest. This began the volcanic activity in the Cascadia subduction zone, forming the modern Cascade Range, and lasted into the Miocene. As extension in the Basin and Range Province slowed by a change in North American Plate movement circa 7 to 8 Million years ago, rifting began on the Gulf of California.[41]

Southern Cordillera

The Sierra madre mountain ranges are separated by the Mexican plateau, and transected by the Trans-Mexican Volcanic Belt. The Southern extent of the American Cordillera makes up Western Mexico, excluding Baja California, and northern Central America.[42] This includes the Sierra Madre Occidental, the Sierra Madre del Sur, and the Trans-Mexican Volcanic Belt.

The Cordillera ends in the south in a belt of miogeosynclines, including the Sierra Madre Oriental fold and thrust belt, the Mesa Central, and parts of the Sierra Madre del Sur. This belt also extends into Central America.[42]

See also

References

  1. ^ Khain, Victor E. (1985). Geology of the USSR. Berlin: Gebr. Borntraeger. ISBN 978-3-443-11017-8.
  2. ^ a b "The Precambrian Era". Michigan State University. Retrieved 10 Mar 2013.
  3. ^ Precambrian Geology of the Southern Canadian Shield and the Eastern Baltic Shield (PDF). USA-USSR-Canada Joint Seminar. Minnesota Geological Survey. 21–23 August 1990. Retrieved 10 Mar 2013.{{cite conference}}: CS1 maint: date format (link)
  4. ^ Larson, Phillip (2008). Quantification of Glacial Sediment Erosion, Entrainment, and Transport Processes and Their Implications for the Dynamic History of the Laurentide Ice Sheet (PDF) (Ph.D.). University of Minnesota.
  5. ^ a b c Christiansen, Eric (2009). "23". Earth's Dynamic Systems (Web Edition 1.0 ed.). Retrieved 1 Mar 2013.
  6. ^ Trimble, Donald (1980). "The Geologic Story of the Great Plains". Geological Society of America. Retrieved 11 Mar 2013.
  7. ^ DiPietro, Joseph (2012). Landscape Evolution in the United States. Elsevier. Retrieved 15 Mar 2013.
  8. ^ Bornhorst; Woodruff; Nicholson. "Stratigraphy, Structure, and Ore Deposits of the Southern Limb of the Midcontinent Rift System". Retrieved 14 April 2013.
  9. ^ Anderson, Raymond (1997). "The Midcontinent Rift: Iowa's Almost Ocean". Iowa Department of Natural Resources. Retrieved 5 Mar 2013.
  10. ^ "The Grenville".
  11. ^ a b c Tollo, Richard P., et al., Proterozoic Tectonic Evolution of the Grenville Orogen in North America, Geological Society of America, 2004 isbn 0813711975
  12. ^ Thomas, William (1973). "Southwestern Appalachian Structural System Beneath the Gulf Coastal Plain" (PDF). American Journal of Science. 273: 372–390. Retrieved 5 Mar 2013.
  13. ^ Dewey; Kidd (November 1974), "Continental Collisions in the Appalachian-Caledonian Orogenic Belt" (PDF), Geology, 2: 543–546, retrieved 5 Mar 2013
  14. ^ "Automated IFSAR Terrain Analysis System". US Army Aviation and Missile Command. 2001. Retrieved 7 Mar 2013.
  15. ^ Hatcher, Robert; Odom; Engelder, Terry; Dunn; Wise; Geiser; Schamel, Steven; Kish (February 1988). "Characterization of Appalachian Faults" (PDF). Geology. 16: 178–181. Retrieved 14 April 2013.
  16. ^ Tollo, Richard; Corriveau, Louise; McLelland, James; Bartolomew, Mervin (2004), Proterozoic tectonic evolution of the Grenville orogen in North America, retrieved 8 Mar 2013
  17. ^ Levin, Vadim; Park, Jeffrey; Brandon, Mark; Menke, William. "Thinning of the upper mantle during late Paleozoic Appalachian orogenesis". Geology. 28 (3): 239–242. Retrieved 8 Mar 2013.
  18. ^ Tagg, John P. "Building the Appalachian Mountains". Retrieved 5 May 2013.
  19. ^ Aber, James (2001). "Appalachian Mountains". Retrieved 5 Mar 2013.
  20. ^ Drake, Avery; Brezinski, David; Wintsch, Robert; Kunk, Michael; Aleinkoff, John; Naeser (2006). "Central Appalachian Piedmont and Blue Ridge tectonic transect, Potomac River corridor" (PDF). Geological Society of America. Retrieved 10 Mar 2013.
  21. ^ a b c Stoffer, Phil; Messina, Paula (1996). "The Atlantic Coastal Plain". Retrieved 10 Mar 2013.
  22. ^ Geology of the Southern Appalachian Mountains (Map). USGS. Retrieved 5 Mar 2013.
  23. ^ Hanner, Charlie; Davis, Susan; Brewer, James (2006). "Central Appalachian Piedmont and Blue Ridge tectonic transect, Potomac River corridor" (PDF). USDA Resources Conservation Service. Retrieved 10 Mar 2013.
  24. ^ Grubb, Hayes; Carillo, J. Joel. (1988). "Chapter 26: Region 23, Gulf of Mexico Coastal Plain". In Back, William; Rosenshein, Joseph; Seaber, Paul (eds.). The Geology of North America. The Geological Society of America. pp. 219–228. Retrieved 28 Feb 2013.
  25. ^ Mancini, Ernest; Obid, Jamal; Badali, Marcello; Liu, Kaiyu; Parcell, William (December 2008). "Sequence-stratigraphic analysis of Jurassic and Cretaceous strata and petroleum exploration in the central and eastern Gulf coastal plain, United States". AAPG Bulletin. 92 (12): 1655–1686. Retrieved 28 Feb 2013.
  26. ^ Humapa. 2012. Retrieved 27 Jan 2013.
  27. ^ Cruz, Guillermo (1993). Geological evolution of the Burgos Basin, northeastern Mexico (Thesis).
  28. ^ Hickman, Robert; Cuervo, Arturo; Valdivieso, Victor; Caraveo, Carlos; Rivera, Sergio; Espinoza, Miguel; Cuevas, Marie; Ghosh, Santosh; Kroener, Robert; Marrullier, Carl (Oct 2002). "Geology and Exploration Potential of the Veracruz Basin". Houston Geological Society Bulletin. 45 (2): 15, 17.
  29. ^ "A Condensed Geological Chronicle of the Yucatan Platform". Retrieved 17 January 2013.
  30. ^ a b c d Townsend, Catherine; Figge, John (2002). "Northwest Origins". The Burke Museum.
  31. ^ Bendick, Rebecca; Baldwin, Julia (2009). "Dynamic models for metamorphic core complex formation and scaling" (PDF). Tectonophysics. Retrieved 19 April 2013.
  32. ^ Liu, Mian (2001). "Cenozoic extension and magmatism in the North American Cordillera" (PDF). Tectonophysic (342): 407–433. Retrieved 19 April 2013.
  33. ^ English, Joseph; Johnston, Stephen; Wang, Kelin. "Thermal modelling of the Laramide orogeny" (PDF). {{cite journal}}: Cite journal requires |journal= (help)
  34. ^ Bunge, Hans-Peter; Grand, Stephen (18 May 2000). "Mesozoic plate-motion history below the Pacific Ocean from seismic images of the subducted Farallon slab". Nature. 405: 337–340. {{cite journal}}: |access-date= requires |url= (help)
  35. ^ McMechan, Margot; Macey, Elizabeth. Geology of the Rocky Mountains west of Calgary, Alberta in the Kananaskis west half map area (PDF). GeoConvention 2012:Vision. Retrieved 15 Mar 2013.
  36. ^ Foos, Annabelle. "Geology of the Colorado Plateau" (PDF). Retrieved 5 March 2013.
  37. ^ Hanson, Erik (2009). "The Grand Canyon". Canyons. Infobase Publishing. Retrieved 15 March 2013.
  38. ^ Gans, Phillip; Miller, Elizabeth (1993). "Extension of the Basin and Range Province". Retrieved 15 Mar 2013.
  39. ^ "Geologic Provinces of the United States:Basin and Range Province". US Department of the Interior. 13 Jan 2004. Retrieved 15 Mar 2013.
  40. ^ a b Dickinson, William (2004). "Evolution of the North American Cordillera" (PDF). Annual Revised Earth Planet Science. 32: 13–45. Retrieved 9 April 2013.
  41. ^ Humphreys, Eugene (2009). "Relation of flat subduction to magmatism and deformation in the Western United States". GSA. {{cite journal}}: |access-date= requires |url= (help); Cite journal requires |journal= (help)
  42. ^ a b King, Philip (1969). The Tectonics of North America. p. 48. {{cite book}}: Cite has empty unknown parameter: |1= (help)

Further reading

  • Bally, Albert W. (1989). Allison R. Palmer (ed.). The geology of North America: An Overview. Boulder, Colo.: Geological Society of America. p. 629. ISBN 978-0813752075.
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