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 of convergent boundary tectonism between approximately 140 million years (Ma) ago, and 50 Ma. The Sevier River area of central Utah is the namesake of this event. This orogeny was produced by the collision of the oceanic Farallon Plate and Kula Plate, predecessors of the Pacific Plate, and their subduction underneath the continental North American Plate. The Sevier orogeny was preceded by several other mountain-building events including the Nevadan orogeny, the Sonoman orogeny, and the Antler orogeny, and partially overlapped in time and space with the Laramide 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 and Mesozoic sedimentary rock. As the crust was shortened, pressure was transferred eastward along the weak sedimentary layers, producing “thin-skinned” thrust faults 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 during rifting in the Late Precambrian during the breakup of the supercontinent Rodinia or during the Ancestral Rocky Mountains orogeny.

The Sevier and Laramide orogenies ended when subduction along the western edge of North America ceased.

[edit] See also

• Geology of the Rocky Mountains

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 of convergent boundary tectonism between approximately 140 million years (Ma) ago, and 50 Ma. The Sevier River area of central Utah is the namesake of this event. This orogeny was produced by the collision of the oceanic Farallon Plate and Kula Plate, predecessors of the Pacific Plate, and their subduction underneath the continental North American Plate. The Sevier orogeny was preceded by several other mountain-building events including the Nevadan orogeny, the Sonoman orogeny, and the Antler orogeny, and partially overlapped in time and space with the Laramide 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 and Mesozoic sedimentary rock. As the crust was shortened, pressure was transferred eastward along the weak sedimentary layers, producing “thin-skinned” thrust faults 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 during rifting in the Late Precambrian during the breakup of the supercontinent Rodinia or during the Ancestral Rocky Mountains orogeny.

The Sevier and Laramide orogenies ended when subduction along the western edge of North America was overcome by western extension of the North American Plate to start the Basin and Range Orogeny.

[edit] References

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

[edit] External links

• Utah's Sevier Thrust System
• Laramide and Sevier orogenies: thin skinned thrust tectonics

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