Sevier orogeny Sevier thrust faults. 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
Eburnean orogeny (LRC). Around 2090 Ma, a syntectonic trondhjemitic pluton intruded into the Archaean reelects of the Chegga series. Around 2070 Ma an asthenospheric upwelling released a large volume of post-orogenic magmas. Eburnian trends within the Eglab shield were repeatedly reactivated from the Neoproterozoic to the Mesozoic. Eburnean orogeny The Eburnean orogeny, or Eburnean cycle was a series of tectonic, metamorphic and plutonic events in what is now West Africa during the Paleoproterozoic era about 2200–2000 million years ago. During this period the Birimian domain in West Africa was established and structured. Eburnian faults are found in the Eglab shield to the