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The Trans-Hudson orogeny or Trans-Hudsonian orogeny was the major mountain building event (orogeny) that formed the Precambrian Canadian Shield, the North American Craton (also called Laurentia), and the forging of the initial North American continent. It gave rise to the Trans-Hudson orogen (THO), or Trans-Hudson Orogen Transect (THOT), (also referred to as the Trans-Hudsonian Suture Zone (THSZ) or Trans-Hudson suture) which is the largest Paleoproterozoic orogenic belt in the world. It consists of a network of belts that were formed by Proterozoic crustal accretion and the collision of pre-existing Archean continents. The event occurred 2.0-1.8 billion years ago. The Trans-Hudson orogen sutured together the Hearne-Rae, Superior, and Wyoming cratons to form the cratonic core of North America in a network of Paleoproterozoic orogenic belts. These orogenic belts include the margins of at least nine independent microcontinents that were themselves sections of at least three former major supercontinents, including Laurasia, Pangaea and Kenorland (ca. 2.7 Ga), and contain parts of some of the oldest cratonic continental crust on Earth. These old cratonic blocks, along with accreted island arc terranes and intraoceanic deposits from earlier Proterozoic and Mesozoic oceans and seaways, were sutured together in the Trans-Hudson Orogen (THO) and resulted in extensive folding and thrust faulting along with metamorphism and hundreds of huge granitic intrusions.〔 Retrieved on 2008-02-11〕 The THO is a right-angled suture zone that extends eastward from Saskatchewan through collisional belts in the Churchill province, through northern Quebec, parts of Labrador and Baffin Island, and all the way to Greenland as the Rinkian belt and Nagssugtodidian Orogen. Westward it goes across Hudson Bay through Saskatchewan and then extends 90 degrees south through eastern Montana and the western Dakotas, downward through eastern Wyoming and western Nebraska, and is then cut off by the Cheyenne belt - the northern edge of the Yavapai province (see Trans-Hudson Orogen map〔 Retrieved on 2008-02-11〕 and the THOT Transect map. To the south, the orogen contributed to the subsurface Phanerozoic strata in Montana and the Dakotas that created the Great Plains. ==Overview== The Trans-Hudson orogeny was the culminating event of the Paleoproterozoic Laurentian assembly, which occurred after the Wopmay orogeny (West of Hudson Bay, ca. 2.1-1.9 Ga.). The Trans-Hudson orogeny resulted from the collision of the Superior Craton of eastern Canada with the Hearne Craton in northern Saskatchewan and the Wyoming Craton of the western United States, with the Archean microcontinent Sask Craton trapped in the THO western interior. Similar to the Himalayas, the Trans-Hudson orogeny was also the result of continent-continent collision along a suture zone. Only the roots of this mountain chain remain, but these can be seen in northeastern Saskatchewan and in the Black Hills of South Dakota. The Trans-Hudson orogeny and the consequent upheaval of the continental crust in the middle Proterozoic eon caused the area around the Great Lakes to become a flattened plain, which in turn led to the creation of the intercontinental basin and the interior and central plains of the United States (the Great Plains are the westernmost portion of North America's Interior Plains, which extend east to the Appalachian Plateau). The Black Hills of South Dakota is one of the few remaining exposed portions of the Trans-Hudson orogenic belt. The peaks of the Black Hills are 3,000 to 4,000 feet above the surrounding plains, while Harney Peak - the highest point in South Dakota - has an altitude of 7,242 feet above sea level.〔 Retrieved on -02-04〕 These central spires and peaks all are carved from granite and other igneous and metamorphic rocks that form the core of the uplift. The nature and timing of this portion of the THO event in southern Laurentia is poorly understood compared to the exposed northern segments in Canada. The Black Hills offer the only surface exposure of the deformed and metamorphosed belt of Paleoproterozoic continental margin rocks in the collisional zone between the Archean Wyoming and Superior provinces. Based on geophysical evidence, this zone has been broadly interpreted to be the southern extension of the THO that was later truncated by the ~1.680 Ga. Central Plains orogen.〔 Retrieved on -01-28〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Trans-Hudson orogeny」の詳細全文を読む スポンサード リンク
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