Sevier orogeny
The Sevier orogeny was one of the most prominent stages in the orogeny process of western North America . Their sphere of influence extended from Canada in the north to Mexico in the south. Its name-giving type locality is in the area of the Sevier River in Utah , its time frame extends from about 140 million years BP ( Lower Cretaceous ) to 50 million years BP ( Lower Eocene ). The Sevier orogeny was preceded by several major orogenic movements, such as the Nevadische orogeny that Sonomische orogeny and the Antler orogeny . It is very difficult to distinguish it from the subsequent orogenic phase, the Laramian orogeny , with which it overlaps spatially and temporally.
The Sevier orogeny is an example of the effects of convergent plate boundaries ; the causes of the orogenic movements are likely to be the collision of the oceanic Farallon plate with the oceanic Kula plate - both precursors of the Pacific plate - and their subsequent subduction under the continental one North American plate to be looked for.
Since the Sevier orogeny is so closely interwoven with the Laramian orogeny in terms of space and time, the two phases are often confused. In general, it can be said that the Sevier orogeny represents a compressive tectonic phase that generally unfolded further west of the Laramian orogeny, using mostly mechanically “weak” layer boundaries in the overlying Paleozoic and Mesozoic overburden as shear paths . The narrowing of the crust meant that the resulting compressive stresses were transferred to mechanically weaker sediment sequences and produced thin-layer thrusts that gradually advanced eastward over time.
This tectonic behavior is very different from that of the Laramian orogeny. This led to block-like uplifts in the basement, which mostly took place on already existing faults. The weak zones of the basement used for this had already been created during the breakup ( continental rifting ) of the supercontinent Rodinia or the subsequent mountain building process of the so-called Ancestral Rocky Mountains , the forerunners of the Rocky Mountains .
The Sevier and also the Laramian orogeny ceased at the time when the subduction taking place on the western continental margin of North America came to an end.
See also
swell
Willis, Grant C: Utah's Sevier Thrust System. Utah Geological Survey Notes, v. 32, no. January 1, 2000