Alleghanian orogeny Province must have been even more intense; however, there is little evidence preserved. Rocks of Mississippian, Pennsylvanian, and Permian age are missing along the Eastern Seaboard. The mountains formed by the Alleghanian orogeny were once rugged and high, but in our time are now eroded into only a small remnant: the heavily-eroded hills of the Piedmont. Sediments that were carried eastward formed the coastal plain and part of the continental shelf. Thus, the coastal plain and Piedmont are largely the byproducts of erosion that took place from 150+ million years ago to the present. Sediments that were carried westward formed
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