Castle of Beersel

The castle of Beersel is a typical example of medieval brick construction, in contrast to some other castles in the region that are largely built of natural stone. Wood and charcoal from the surrounding area were used for baking these bricks, which is also mentioned in a document from 1306. There was sufficient suitable clay available at the castle site to produce bricks, and using locally available materials was cheaper and logistically simpler than sourcing natural stone from the area.

The clay used for the bricks of Beersel Castle comes from the local clay layers of the Brussels Formation, which also includes the Lede Formation and the Maldegem Formation. These formations belong to the geological period of the Late Eocene, approximately 42 to 37 million years ago.

The region around Brussels was then located at the edge of a shallow, warm sea that covered large parts of present-day Belgium. The landscape consisted of a coastal plain with tidal influences, where alternating marine clay and sand layers were deposited by the sea. The climate was subtropical, as evidenced by the fossils and the composition of the deposits.

Further up, you will find coarse sand associated with the Brussels Formation (the Brussels Formation), strongly linked to channels. During the Eocene, specifically the Brussels period, deep channels were carved into the substrate by tides and currents. These channels could locally reach a thickness of 40 to even more than 80 meters and were subsequently filled with sandy deposits.

Pascal Brackman