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
Svecofennian orogeny Svecofennian orogeny The Svecofennian orogeny is a series of related orogenies that resulted in the formation of much of the continental crust in what is today Sweden and Finland plus some minor parts of Russia. The orogenies lasted from about 2000 to 1800 million years ago during the Paleoproterozoic Era. The resulting orogen is known as the Svecofennian orogen or Svecofennides. To the west and southwest the Svecofennian orogen limits with the generally younger Transscandinavian Igneous Belt. It is assumed that the westernmost fringes of the Svecofennian orogen have been reworked by the Sveconorwegian orogeny just as the western parts