The Carboniferous is a Paleozoic period between the Permian and Devonian.
It is commonly divided into Pennsylvanian and Mississippian in North America. However, in much of the world it has historically been subdivided into Lower (Early) and Upper (Late). Because the boundary between the two varied globally, the International Commission on Stratigraphy has established that the American names should be used throughout the world.
- Heckel, P. H. and G. Clayton, 2006, Use of the new official names for the subsystems, series and stages of the Carboniferous System in international journals: Proceedings of the Geologists’ Association, v. 117, p. 1-4.