1. The final epoch in the Pennsylvanian, comprising the Klazminskian and Noginskian Ages (these are also stage names in eastern European stratigraphy). The Gzelian is preceded by the Kasimovian Epoch, followed by the Asselian Age (Early Permian), and has its upper boundary (the Carbo—Permian boundary) dated at 290 Ma ( Harland et al., 1989).
2. The name of the corresponding eastern European series, which is roughly contemporaneous with the upper Virgilian (N. America) and upper Stephanian (western Europe).
"Gzelian." A Dictionary of Earth Sciences. . Encyclopedia.com. (September 25, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/gzelian
"Gzelian." A Dictionary of Earth Sciences. . Retrieved September 25, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/gzelian