U/Th dating of the Annevoie-Rouillon travertines
Service de Géologie Fondamentale et Appliquée, Faculté Polytechnique de Mons, Rue de Houdain, 9, B-7000 Mons. E-mail: Yves.quinif@fpms.ac.be
Abstract
The carbonated travertine’s accumulations near sources or in rivers constitute very good environmental indicators (Ford & Pedley, 1996; Guendon J.-L. et al., 1997; Guendon J.-L. et al., 2003; Ollivier, 2006 ; Roiron, 1997). They can record climate variations, fluctuations of the basis level, epirogenic movement and eustatic variations. Among climate substitution variables, let’s quote the pollen collections, the plants debris and the geochemistry. Moreover, the travertines can be dated by the uranium series disequilibrium method, or radiocarbon. In Belgium, there are some sites of travertines deposits: Annevoie-Rouillon, Casteau, Chaumont-Gistoux, Hoyoux’s valley, Orval, Treignes, Vierset-Barse (Geurts, 1976). The travertines of Annevoie-Rouillon are famous because they have been the subjects of litho-stratigraphic, palynological and geochemical studies (Paepe, 1965; Bastin et al., 1968; Geurts, 1976; Janssen & Swennen, 1997). These studies have been made in the stratigraphic series of the behind-dam in the carbonated rudites and arenites carbonates and clays. A new examination of the deposit has permitted to discover the witnesses of the dam basis which present more compact facies with plant debris. Those facies are able to be dated by the uranium series disequilibrium method. The sampling has been made in two types of facies: the travertine itself and speleothems in little cavities in the travertines. The first have not permitted to have reliable ages because of impurities in the calcite. The second have been dated from the beginning of the Holocene. Those datings confirm the Holocene ages of the stratigraphic series studied by Bastin and Geurts. Moreover, those ages imply that the Meuse River occupied an altitudinal level equal or lower than its present level just after the last glaciation. Future studies would consist in drillings under the level of the river to look for the basis of the travertine edifice.
Holocene, Meuse valley, environment indicator, speleothem