Natural versus anthropogenic genesis of mardels on the Gutland plateau a geoecological study of mysterious landforms

Mardels, small closed depressions, are distinctive landforms on the Luxembourger Gutland plateau. In the present landscape most mardels are shallow fens, filled with colluvial sediments. The genesis of mardels has been studied intensively, inside and outside Luxembourg. In research reports published before 2000, a natural genesis has been suggested. In more recent publications the researchers suggested also anthropogenic causes.
In the Gutland, mardels occur on various substrates. Mardels on the Strassen marls (li3) are abandoned quarries, related to clay excavation in Roman Time; (li2) the clay was deposited in depressions, related to joints in the underlying Luxembourger sandstone formation. Mardels on the Keuper marls (km1,3) are originally subsidence basins, related to subsurface dissolutions of gypsum lenses and veins, filled with colluvial clay. The results of pollen analysis and archaeometrical tests point to Roman extraction of mardel clay for the production of pottery. In conclusion, the natural depressions have been enlarged to the present mardels. After the depart of the Romans, the sedimentation of clayey colluvium restarted in the abandoned quarries.