1. An age in the Middle Eocene, preceded by the Lutetian, followed by the Priabonian (Late Eocene) and with an upper boundary dated at 38.6 Ma ( Harland et al., 1989).
2. The name of the corresponding European stage, which is roughly contemporaneous with most of the upper Narizian (N. America), upper Bortonian and Kaiatan (New Zealand), and part of the Aldingan (Australia). It was originally considered to be a lateral equivalent of the Priabonian Stage (Upper Eocene). (The name should not be confused with Bortonian.)
"Bartonian." A Dictionary of Earth Sciences. . Encyclopedia.com. (September 19, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/bartonian
"Bartonian." A Dictionary of Earth Sciences. . Retrieved September 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/bartonian