The geological map of Belgium

Frédéric Boulvain has provided us with a brief history of the Geological Map of Belgium (1).

Many agree that Jean-Baptiste d'Omalius d'Halloy from Liège (1783-1875) is the father of Belgian geology. His studies were synthesised in 1822 by a “Test of a geological map of France, the Netherlands and several other neighbouring countries”. The map was based on surveys carried out between 1803 and 1814, upon Napoleon’s request. It was another man from Liège, André Dumont (1809-1857), who was to revolutionise the profession. He became known, at the age of 21, through a geological description of the Province of Liège.

André Dumont
Jean-Baptiste d'Omalius d'Halloy

He pointed out the importance of the fold in the arrangement of the formations in southern Belgium, one of his major contributions to geological science. In 1836, the government asked him to draw a geological map of the young kingdom. He only finished this massive piece of work 12 years later. This led him to cover approximately 90,000 km and perform 20,914 geological reading! This map of a scale of 1:160000, where we can see the main geological units in Belgium, remained a model of its type for a long time.

Carte géologique d'Omalius d'Halloy EN

Between 1878 and 1885, an attempt was made to create a map on a larger scale, 1:20000, but only a few parts were completed. Finally, it was a map of a scale of 1:40000 that was created in 1903, except for one sheet (out of the 226 sheets of the map) that was only submitted in 1913 and published in 1919. Belgium then had a large-scale geological map that was the envy of the world (many European countries had to wait decades before achieving a similar result). The result was so enviable that many years passed before it was improved. Hence, we were left lagging behind!

It was not until a Walloon initiative in 1988 that work began on a new map, which is still in progress today, and certainly for another decade or so. Under the responsibility of the University of Liège’s Department of Geology, a dozen geologists have been working on the map of Wallonia’s substratum on a scale of 1:10000 since 1990. Flanders is doing likewise (owing to regionalisation) but more rapidly owing to a smaller scale (1:50000) considering the nature of the terrains.

carte géologique 1/40000  EN

Such maps are, of course, based on observations made in the field, but also by boring the ground. Until regionalisation occurred, everyone who bored the country’s ground (for whatever reason: search for water, coal, etc.) had to submit the result to the Service Géologique de Belgique. But since the substratum was regionalised, the Service is no longer qualified to deal with this. And no other body has replaced it. It is no longer obligatory to keep the results of boring, thus depriving geologists of an important tool.

For the history of the geological map of Belgium, see Frédéric Boulvain’s class (French):

For more information on the Walloon map, go to:

(1) Un historique de la carte géologique de Belgique, by Frédéric Boulvain, Service géologique de Belgique, Professional Paper, 1993/4, N262, 88p, 8pl. Brussels