The group is named after the region of Hesbaye in the south of Limburg.
The Houthem Formation consists of shallow marine sandy limestones of early to middle Danian age (about 65-63 million years old).
This formation also occurs in the Netherlands, where it is considered part of the Chalk Group.
The Opglabbeek Formation is an alternation of continental to lagunary clay, sand and lignite layers of early Selandian age (about 60 million years old).
The late Paleocene Hannut Formation (marine clays, sands and limestones) is normally lying stratigraphically on top of the Hesbaye Group.