High-resolution isotope stratigraphy of the Devonian-Carboniferous boundary in the Namur-Dinant Basin, Belgium

The Devonian-Carboniferous (D-C) boundary sequence of the Namur-Dinant Basin in southern Belgium consists of marine platform carbonates. Global biostratigraphic correlation of the boundary has been a dilemma due to the absence of index conodont zones. Despite the scarcity of brachiopods, we managed to sample twenty-five calcitic shells from boundary beds at the Royseux-Gare section, to reconstruct biochemostratigraphic profiles of oxygen-, carbon- and strontium-isotopes for correlations with established global counterparts. The delta O-18 and delta C-13 values of the well-preserved shells range from - 7.8 to - 6.3%. VPDB (- 7.2 +/- 0.4, n = 25) and from + 1.1 to + 2.4 parts per thousand VPDB (1.8 +/- 0.3, n = 25). respectively. The shells also yielded Sr-87/Sr-86 ratios between 0.708185 and 0.708297. The Royseux isotope signatures are within the ranges documented for the global D-C boundary but their isotope profiles, however, show no significant shifts or excursions. Evaluation of the Royseux isotope profiles and correlation with their global counterparts may suggest a stratigraphic hiatus approximately from the middle Siphonodella praesulcata to the lower Siphonodella sulcata zones on the global D-C boundary conodont biostratigraphic scheme, while corresponding to the Hangenberg Event in Belgium. (C) 2009 Elsevier B.V. All rights reserved.