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 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.
Willis, Grant C. "Utah's Sevier Thrust System" Utah Geological Survey Notes. v. 32 no. 1 January 2000
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Utah's Sevier Thrust SystemLaramide and Sevier orogenies: thin skinned thrust tectonics
