This is a result of orogenic activity Non-marine shales and sandstones deposited in lower Mississippian Development of extensive limestone platforms of the Mississippian . Late Mississippian regression associated with initiation of glaciation in southern hemisphere. Western craton in Devonian experienced limestone, shale, and reef deposition with some restricted circulation and evaporites. Absaroka Sequence Widespread regional unconformities. Absaroka begins in the Pennsylvanian .
Pennsylvanian sedimentation reflects coastal lowland settings and thick peat swamps.
Continental sandstones, shales, mudstones, and coal predominate. Terrestrial clastic rocks alternate cyclically with shallow marine deposits. In mid-continent marine limestones alternate with sandstone and shale. If you've got the time or the inclination, take the Kentucky Geological Survey's virtual field trip to Red River Gorge where you'll be able to examine Late Paleozoic rocks. Evaporites surrounded by limestones and reef complexes.