LESSONS LEARNED AND NEW PERSPECTIVES FROM THE DESCRIPTION AND CHARACTERIZATION OF WEATHERING PROFILES IN THE BELGIAN ARDENNES AREA.

Weathering profiles are widespread in the Ardenne area. In the upper part of the lithosphere, Paleozoic rocks experienced several phases/periods of weathering leading to major petrographic, mineralogic, geochemical and rheologic modifications of the primary protolites. The weathering profiles, reaching 65 meters thick in some areas, are mainly saprolites. Their large occurrences have significant consequences for many applied domains, such as mineral resources, hydrogeology, engineering, waste disposal, geoprospective, agronomy, environmental risks (erosion, landslides, flooding). They are however most frequently not clearly mentioned in the (geological, hydrogeological, pedological) maps of Wallonia. I will show numerous examples of weathering profiles of the Belgian Ardenne, focusing on i) mineralogical/geochemical modifications due to weathering, ii) periods of weathering in Belgium, iii) associated mineral resources. I will initiate a debate about the need of better knowledge of these essential rocks of Belgium and Luxembourg.

Prof Johan YANS

Director of the Geology department, University of Namur