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Laurentia, also called the +n craton">North America+n craton+n craton" style="color: #CCCCCC;">+
'''Laurentia''' ('''North American Craton''') is a large continental craton+, which forms the ancient geological core of the North America+n continent. Many times in its past, Laurentia has been a separate continent+ as it is now in the form of North America, although originally it also included the cratonic areas of Greenland+ and also the northwestern part of Scotland+, known as the Hebridean Terrane+. During other times in its past, Laurentia has been part of larger continents and supercontinents+ and itself consists of many smaller terranes+ assembled on a network of Early Proterozoic+ orogenic+ belts. Small microcontinents+ and oceanic islands collided with and sutured onto the ever-growing Laurentia, and together formed the stable Precambrian+ craton seen today.

The craton is named after the Laurentian Shield+, which in turn is named after the Laurentian Mountains+.

In eastern and central Canada, much of the stable craton is exposed at the surface as the Canadian Shield+; when subsurface extensions are considered, the wider term Laurentian Shield+ is more common, not least because large parts of the structure extend outside Canada. In the United States, the craton bedrock is covered with sedimentary rocks of the interior platform in the Midwest+ and Great Plains+ regions. Only in northern Minnesota, Wisconsin, the Adirondacks+ of New York and the Upper Peninsula of Michigan is the craton bedrock exposed. The sequence of rocks varies from about 1,000 to in excess of 6,100 m (3,500–20,000 ft) in thickness. The cratonic rocks are metamorphic+ and igneous+, while the overlying sedimentary rock+s are composed mostly of limestone+s, sandstone+s, and shale+s. These sedimentary rocks were deposited from 650 to 290 million years ago.

The metamorphic and igneous rocks of the "basement complex+" were formed 1.5 to 1.0 billion years ago in a tectonically active setting. It was a setting of great pressure and temperature. The younger sedimentary rocks that were deposited on top of this basement complex were formed in a setting of quiet marine and river waters. During much of Mississippian time, the craton was the site of an extensive marine carbonate platform on which mainly limestones and some dolostones and evaporites were deposited. This platform extended either from the present Appalachian Mountains or Mississippi Valley to the present Great Basin. The craton was covered by shallow, warm, tropical epicontinental or epicratonic sea+ (meaning literally "on the craton") that had maximum depths of only about 60 m (200 ft) at the shelf edge. During Cretaceous+ times, such a sea, the Western Interior Seaway+, ran from the Gulf of Mexico+ to the Arctic Ocean+, dividing North America into eastern and western land masses. Sometimes, land masses or mountain+ chains rose up on the distant edges of the craton and then eroded down, shedding their sand across the landscape.

The southwestern portion of Laurentia consists of Precambrian basement rocks deformed by continental collisions (violet area of the image above). This area has been subjected to considerable rifting+ as the Basin and Range Province+ and has been stretched up to 100% of its original width. The area contains numerous large volcanic eruptions+.

* Around 4.03 to 3.58 Ga+, the oldest intact rock formation on the planet, the Acasta Gneiss+, was formed in what is now Northwest Territories+ (older individual mineral grains are known, but not whole rocks).
* Around 2.5 Ga, Arctica+ formed as an independent continent.
* Around 2.45 Ga, Arctica was part of the major supercontinent Kenorland+.
* Around 2.1 Ga, when Kenorland shattered, the Arctican craton was part of the minor supercontinent Nena+ along with Baltica+ and Eastern Antarctica+.
* Around 1.8 Ga, Laurentia was part of the major supercontinent Columbia+.
* Around 1.5 Ga, Laurentia was an independent continent.
* Around 1.1 Ga, Laurentia was part of the major supercontinent Rodinia+.
* Around 750 Ma, Laurentia was part of the minor supercontinent Protolaurasia+. Laurentia nearly rifted apart.
* Around 600 Ma, Laurentia was part of the major supercontinent Pannotia+.
* Around Cambrian+ (542 ±0.3 to 488.3 ±1.7 Ma), Laurentia was an independent continent.
* Around Ordovician+ (488.3 ±1.7 to 443.7 ±1.5 Ma), Laurentia was shrinking and Baltica got bigger.
* Around Devonian+ (416 ±2.8 to 359.2 ±2.5 Ma), Laurentia collided against Baltica, forming the minor supercontinent Euramerica+.
* Around Permian+ (299.0 ±0.8 to 251.0 ±0.4 Ma), all major continents collide against each other for forming the major supercontinent Pangaea+.
* Around Jurassic+ (199.6 ±0.6 to 145.5 ±4 Ma), Pangaea rifted into two minor supercontinents: Laurasia+ and Gondwana+. Laurentia was part of the minor supercontinent Laurasia.
* Around Cretaceous+ (145.5 ±4 to 66 Ma), Laurentia was an independent continent called North America.
* Around Neogene+ (23.03 ±0.05 Ma until today or ending 2.588 Ma), Laurentia, in the form of North America, crashed into South America+, forming the minor supercontinent America.
* Around 250 Ma from now, all continents may crash together, forming the major supercontinent Pangaea Ultima+. Laurentia would be part of Pangaea Ultima.
* Around 450-600 Ma from now, Pangea Ultima will eventually rift apart. Laurentia may break off.

North America craton map used courtesy and with permission providing proper from http://www.mapsorama.com/north-america-craton-map/

North America craton map colors defined: The brown area shows the part of the North American continent that has been stable for over 600 million years. The green area on the illustration shows new continental material added relatively recently, within the last 600 million years. The purple area fringing the stable continental core is made up of older Precambrian basement that was deformed during plate collisions that occurred within the last 600 million years.
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*, paleogeographic history of southwestern Laurentia, goes back to 1.7 billion years ago.
* - Paleogeographic history of western Laurentia, goes back to the Permian period.
*
* from The Smithsonian National Museum of Natural History
*



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Laurentia+ Laurentia (North American Craton) is a large continental craton, which forms the ancient geological core of the North American continent.
Laurentian Library+ The Laurentian Library (Biblioteca Medicea Laurenziana) is a historical library in Florence, Italy, containing a repository of more than 11,000 manuscripts and 4,500 early printed books.
Laurentian Mountains+ The Laurentian Mountains (French: Laurentides) are a mountain range in southern Quebec, Canada, north of the St.
Laurentia Tan+ Laurentia Tan Yen Yi BBM PBM (/lɒˈrɛnʃə/ lo-REN-shə; Chinese: 陈雁仪; pinyin: Chén Yànyí, pronounced [tʂə̌n jɛ̂n í]) (born 24 April 1979), is a United Kingdom-based Singaporean Para-equestrian competitor.
Laurentian University+ Laurentian University (Université Laurentienne), which was incorporated on March 28, 1960, is a mid-sized bilingual university in Greater Sudbury, Ontario, Canada.
Laurentian Hills+ Laurentian Hills is a municipality in Eastern Ontario, Canada, on the Ottawa River in Renfrew County. It surrounds (by land) Deep River on the Ontario side of the river.
Laurentian Valley+ Laurentian Valley is an incorporated township in Renfrew County in eastern Ontario, Canada. It borders on the Ottawa River, the city of Pembroke and the town of Petawawa.
Laurentian Bank of Canada+ The Laurentian Bank of Canada (LBC) (French: Banque Laurentienne du Canada) is a Schedule I bank in the province of Quebec.
Laurentian Mixed Forest Province+ The Laurentian Mixed Forest Province, also known as the North Woods, is a forested ecoregion in the United States and Canada.
 Laurentian+ Laurentian (French: Laurentides or Laurentien) may refer to: