The latest Tremadocian messaoudensis-trifidum acritarch assemblage from the upper part of the Lierneux Member (Salm Group, Stavelot Inlier, Belgium)

The acritarch assemblage occurring in the upper part of the Lierneux Member (Jalhay Formation, Salm Group, Stavelot Inlier, Belgium) has recently been attributed to the messaoudensis-trifidum microflora and dated as latest Tremadocian. It contains most of the characteristic species of the English Lake District sub-assemblage 3 except for the two galeate species Cymatiogalea deunfii and C. messaoudensis. The reinvestigation of all available material has established a very diverse association of over 40 species. It shows a great potential from both stratigraphic and palaeogeographic points of view. A formal Stelliferidium trifidum–Veryhachium lairdii Biozone defined by the appearance of 11 species is proposed. Athabascaella playfordii has been observed in all samples. Previously known only from areas of low to intermediate latitudes, the species is shown for the first time to occur also at higher latitudes. Most of the identified species, including Dactylofusa velifera, Kladothecidium eligmosum and Palaiosphaeridium kamax are illustrated. Some are briefly described. The synonymy between Priscogalea chevronensis and Stelliferidium trifidum is confirmed.