Chitinozoan biostratigraphy of the Upper Ordovician of Faulx-les-Tombes (central Condroz Inlier, Belgium)

The chitinozoan biostratigraphy of the Upper Ordovician Vitrival-Bruyère and Fosses formations (Bois de Presles and Faulx-les-Tombes members) in the Faulx-les-Tombes area (Condroz Inlier, Belgium) is documented. The Baltoscandian Spinachitina cervicornis and Conochitina rugata chitinozoan biozones are recognised, and possibly also the Fungochitina fungiformis and Tanuchitina bergstroemi zones. Correlation with the Cautley Mudstones Formation of the Avalonian type Ashgill area is done with the C. rugata and the Bursachitina umbilicata chitinozoan biozones and possibly also with the F. fungiformis and T. bergstroemi chitinozoan biozones. The correlation allows an accurate dating of both formations. The Vitrival-Bruyère Formation is shown to span a much larger time interval than previously thought. The combination of litho- and biostratigraphical results from this study and those from the Puagne Inlier (western Condroz Inlier) shows diachronic boundaries for both members of the Fosses Formation. At some time during the deposition of the rugata and umbilicata chitinozoan biozones, simultaneous deposition took place of calcareous shale in the Puagne Inlier and mottled mudstone on a deeper shelf position in the Faulx-les-Tombes area.