AGE ET ORIGINE DES SHALES AYANT SERVI À LA CONFECTION DES ANNEAUX PRÉHISTORIQUES (SECOND AGE DU FER) DE BASÈCLES (BELGIQUE)
Paléobotanique, Paléopalynologie et Micropaléontologie, Université de Liège Sart Tilman B18, B-4000 Liège
Paléobotanique, Paléopalynologie et Micropaléontologie, Université de Liège Sart Tilman B18, B-4000 Liège
Abstract
ABSTRACT. Provenance and age of the shales used in the making of prehistorical stone rings found in Basècles (Belgium) and attributed to the second Iron Age. An archaeological site in Basècles yielded many shale pieces. They are the remnants of a stone rings industry, dated to the second Iron Age (300-400 BC). The source material was not excavated in Basècles since its basement consists of Dinantian limestone, Thanetian and Ypresian sand and clay. Where did this material come from?
A biostratigraphical analysis with acritarchs dates the source material to the upper Telychian (Llandovery, Lower Silurian). Since the analysed samples yield very similar palynological results and show the same lithological facies, it is assumed that they come from the same deposit in a single locality. In Belgium, Silurian rocks are found in two different areas: the Sambre-Meuse Inlier and the Brabant Massif. Silurian rocks have just been discovered in the Boulonnais (Northern France), but their Wenlock-Ludlow age and the great distance from Basècles preclude they may be the source material. A former study (Vanguestaine, 1995) hypothesised that the source material may come from the Dendre valley. However, no reference samples were available at that time and no formal evidence could be shown. The present study investigates rock debris from the Dendre valley that show a lithological facies similar to the source rocks of the stone rings. Their lithological and palynological likeness to the stone ring material confirms the former hypothesis and allows to be more specific about the source area of the material. They likely belong to the Fallais Formation. Moreover, these results exclude the presence of Deville Group rocks south to the porphyric sill of Lessines.