It is named after the East Anglian town of Cromer in Great Britain where interglacial deposits that accumulated during part of this stage were first discovered.
The stratotype for this interglacial is the Cromer Forest Bed situated at the bottom of the coastal cliff near West Runton.
[1] The core of the Cromerian is the first half of the Middle Pleistocene stage (Ionian) approximately 800-500 ka ago, just before the Anglian glaciation.
However, the Aftonian, along with the Yarmouthian (Yarmouth), Kansan, and Nebraskan, have been abandoned by North American Quaternary geologists and merged into the Pre-Illinoian.
Great potential for a full breakdown has been provided by the extensive, continental series at Gorleben.