The Houthem Formation consists of maximally 30 metres of light grey to light yellow calcareous arenites. The arenite can contain calcareous concretions, fossils and hardgrounds with shell fragments. At other places lenses of boundstone occur, formed by red algae.
Dutch stratigraphers see the Houthem Formation as the youngest formation of the Chalk Group, because it has a similar lithology with the older formations in this group. Belgian stratigraphers see it as part of the Hesbaye Group, which contains Paleocene formations.
Bless, M.J.M.; Dusar, M.; Felder, P.J. & Swennen, R.; 1993: Lithology and biostratigraphy of Upper Cretaceous-Paleocene carbonates in the Molenbeersel borehole (NE Belgium), Geologie en Mijnbouw 71, pp. 239-257.
Laga, P.; Louwye, S. & Geets, S.; 2001: Paleogene and Neogene lithostratigraphic units (Belgium), Geologica Belgica 4, pp. 135-152.
Felder, W.M.; 1975: Lithostratigrafie van het Boven-Krijt en het Dano-Montien in Zuid-Limburg en het aangrenzende gebied, in: Toelichting bij de geologische overzichtskaarten van Nederland, Rijks Geologische Dienst, Haarlem, pp. 63-72.
Romein, B.J.; 1962: On the type locality of the Maastrichtian (Dumont, 1849), the upper boundary of that stage and on the transgression of a Maastrichtian s.l. in Southern Limburg, Mededelingen Geologische Stichting, nieuwe serie 15, pp. 77-84.