Alleghanian orogeny

The collision provoked the orogeny: it exerted massive stress on what is today the Eastern Seaboard of North America, forming a wide and high mountain chain.

[3] Evidence for the Alleghanian orogeny stretches for many hundreds of kilometres on the surface from Alabama to New Jersey and can be traced further subsurface to the southwest.

The sedimentary rock in the eastern Appalachian Basin region was squeezed into great folds that ran perpendicular to the direction of forces.

The influence of Alleghanian deformation on the regions east of the Valley and Ridge Province must have been even more intense; however, there is little evidence preserved.

Thus, the coastal plain and Piedmont are largely the byproducts of erosion that took place from 150+ million years ago to the present.

[9] A portion of the Alleghanian mountain system departed with Africa when Pangaea broke up and the Atlantic Ocean began to form.

Location of the Hercynian/Variscan/Alleghanian mountain chains in the Carboniferous period. Large labels are continents that joined during these orogenies. Present day coastlines in gray. Sutures are red.
The Alleghanian orogeny, a result of three separate continental collisions. USGS
Major fault at the dividing line between the Allegheny Plateau and the true Appalachian Mountains ( Williamsport, Pennsylvania ).