The formation consists of alternating marine clay and sand strata, deposited during the late Eocene.
In the northern parts of Flanders it forms an up to 50 meters thick sequence in the subsurface.
Further south and to the east (in the Campine of the province of Antwerp) the formation pinches out and can be only a few meters in thickness.
The Maldegem Formation is not part of a stratigraphic group and forms an independent unit in the lithostratigraphy of Belgium.
Stratigraphically on top of it is usually the Zelzate Formation (green grey sand with a Priabonian to Rupelian age), part of the Tongeren Group.