The Aachen Formation consists of
glauconite-bearing
sand. It was deposited during the
Santonian and
Campanian ages (85.8 to 70.6 million years ago) of the Cretaceous Period. The formation rests
unconformably on top of
Carboniferous rocks of the
Limburg Group, which are more than three times as old. Overlying the Aachen Formation is the
Vaals Formation, equivalent to the upper part of the Chalk Group of England. == Fossil content ==