The formation is taken from Belgian lithostratigraphy, although it is considered a group in Belgium.
The age in which the formation formed is the Rupelian (34 to 28 million years ago), a subdivision of the Oligocene epoch.
The age and the formation are both named after the Belgian river Rupel.
During the Rupelian age the Netherlands (and Belgium) were covered by a shallow sea, which became deeper towards the northwest.
In the east, on the Middel-Netherlands High, the base of the formation can also be a nonconformity with Mesozoic deposits.