The Geopark, a landscape of contrasts between Famenne & Ardenne

THE LANDSCAPES TO BE FOUND WITHIN THE GEOPARK REFLECT THE NATURE OF THE SUBSURFACE.

Sandstone is more resistant than limestone, which in turn is more resistant than shale. Shales, as a result of their flaky, fragile nature, are more easily eroded by freezing (gelifraction). Shales are thus found in depressions, as the Famenne depression perfectly illustrates. Sandstone and conglomerates are highly resistant to erosion and make up the uplands of the Ardenne. Limestone occupies an intermediate position. It is surrounded by shales, and differential erosion has neatly exposed the limestone strip : this is the Calestienne, the central theme of the Geopark.

The term CALESTIENNE is derived from the German « Kalkstein » for limestone, or from a prefix referring either to limestone or to heat, because the vegetation of limestone regions is more thermophilic. « Tienne » is a Walloon word for height.

FIG 1 Relief map (« Data source : SPW ») showing the position of the Calestienne.

FIG 2 North / south section at the Tier des Falizes between Famenne and Ardenne.

FIG 3 Diagram illustrating rock strength

FIG 4 La Roche aux Corneilles is a surprising limestone outcrop on the right bank of the Ourthe.

FIG 5 La Roche à Frêne is a rocky bar on the right bank of the Aisne, consisting of a quartz-pebble and sandstone conglomerate. Known locally as Wéris Puddingstone, it forms a strip that is less well known but just as visible as the Calestienne. This particularly hard rock is the basic material of the Wéris megaliths.

FIG 6 The Martouzin (Beauraing) lookout point on the summit of the Calestienne offers an uninterrupted view over the Famenne depression.