The Sevier orogeny was a mountain-building event that affected western North America between aproximately 140 million years ago (Ma), and 50 Ma. The Sevier River area of central Utah is the namesake of this event, which was a result of convergent boundary tectonism; a fold-thrust belt formed during this event. World map showing North America A satellite composite image of North America North America is a continent in the northern hemisphere bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the south by the Caribbean Sea, and on the west by the... The Sevier River (SUH-veer) is a river, approximately 280 mi (450 km) long, in southwestern Utah in the United States. ... Utah is one of the Four Corners states, and is bordered by: Idaho (at 42°N) and Wyoming (at 41°N and 111°W) in the north, by Colorado (at 109°W) in the east, at a single point by New Mexico to the southeast (at the Four Corners Monument... In plate tectonics, a convergent boundary (convergent fault boundary, convergent plate boundary, or active margin) is where two tectonic plates slide towards each other and usually collide forming either a subduction zone with its associated island arc or an orogenic belt and associated mountain range. ...

According to the State of Utah Geological Survey service, the Sevier orogeny is often confused with the Laramide orogeny, even by geologists, because they overlap in time and location. The two orogenies were produced by the same crustal shortening event, namely, the collision of the Farallon Plate and North American plate, but they are distinguished by disparate styles of deformation. The Sevier orogeny defines a more western compressional event that took advantage of weak bedding planes in overlying Paleozoic and Mesozoic sedimentary rock. The Laramide orogeny was a 30 million year period of mountain building in western North America that started in the Late Cretaceous, 70 million years ago, and ended in the Late Paleogene 40 million years ago. ... A geologist is a contributor to the science of geology. ... The Farallon Plate is an ancient tectonic plate which began subducting as Pangaea broke apart during the Jurassic period. ... The North American plate is shown in brown on this map The North American Plate is a continental tectonic plate covering the continent of North America, extending eastward to the Mid-Atlantic Ridge and westward to the Cherskiy Range in East Siberia. ... The Paleozoic is a major division of the geologic timescale, one of four geologic eras. ... The Mesozoic is one of three geologic eras of Phanerozoic eon. ...

As the thrust belt shortened the underlying Precambrian basement metamorphic and igneous rocks, pressure was transferred eastward along the weak sedimentary layers, producing “thin-skinned” thrust faulting that, in its eastern reaches, involved only the overlying sedimentary strata. Low angle thrusts, which detached the overlying from the underlying, terminated in anticline fold crumplings. Whereas, the Laramide orogeny produced “basement-cored” uplifts because the thin sedimentary rock in those areas did not easily “decouple” from the basement rock. The Precambrian is an informal name for the eons of the geologic timescale that came before the current Phanerozoic eon. ... A thrust fault is a particular type of fault, or break in the fabric of the Earths crust with resulting movement of each side against the other, in which one side is pushed up relative to the other and somewhat over it. ... In geology, an anticline is a type of fold that involves a downward slope to either side. ...

References

Willis, Grant C. "Utah's Sevier Thrust System" Utah Geological Survey Notes. v. 32 no. 1 January 2000

External links

Utah's Sevier Thrust System

Laramide and Sevier orogenies: thin skinned thrust tectonics