Siegenian and Emsian Acritarcha in the Synclinorium of Dinant originate from redistributed Silurian and Ordovician sediments. The assemblages on the northem side are exclusively Silurlan. On the southem flank Silurian and Ordovician are mixed in sorne localities. These data imply distinct source areas: a northem Silurian one feeding the entire basin, a ? southern Ordovician one just feeding the southern margin. It seems likely that the northem source area should not be located at a higher latitude than the Brabant Massif and then should correspond to the presently removed thick late Silurian sediments that are needed to explain the slaty cleavage affecting the Cambro-Silurian rocks of the Brabant area. The southern source area could be searched in one of the internal highs of the Variscan geosyncline like the Mid-German Swell.