- Sevier orogeny
The Sevier orogeny was a mountain-building event that affected western
North America from Canada to the north to Mexico to the south. This orogeny was the result ofconvergent boundary tectonism between approximately 140 million years (Ma) ago, and 50 Ma. TheSevier River area of centralUtah is the namesake of this event. Thisorogeny was produced by the collision of the oceanicFarallon Plate andKula Plate , predecessors of thePacific Plate , and theirsubduction underneath the continentalNorth American Plate . The Sevier orogeny was preceded by several other mountain-building events including theNevadan orogeny , the Sonoman orogeny, and theAntler orogeny , and partially overlapped in time and space with theLaramide orogeny .Since the Sevier and Laramide orogenies occurred at similar times and places, they are sometimes confused. In general the Sevier orogeny defines a more western compressional event that took advantage of weak bedding planes in overlying
Paleozoic andMesozoic sedimentary rock. As the crust was shortened, pressure was transferred eastward along the weak sedimentary layers, producing “thin-skinned”thrust fault s that generally get younger to the east. In contrast, the Laramide orogeny produced “basement-cored” uplifts that often took advantage of preexisting faults that formed duringrifting in the Late Precambrian during the breakup of the supercontinentRodinia or during theAncestral Rocky Mountains orogeny.The Sevier and Laramide orogenies ended when subduction along the western edge of North America ceased.
ee also
*
Geology of the Rocky Mountains References
Willis, Grant C. "Utah's Sevier Thrust System" Utah Geological Survey Notes. v. 32 no. 1 January 2000
External links
* [http://ugs.utah.gov/utahgeo/geo/thrustfault.htm Utah's Sevier Thrust System]
* [http://www.geowords.com/histbooknetscape/g17.htm Laramide and Sevier orogenies: thin skinned thrust tectonics]
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