Abstract

The main palaeogeographic conclusions arrived at during the course of systematic work on the acritarchs of the Middle Frasnian (F2) and Upper Frasnian (F3) of the Dinant basin and the southern border of the Namur basin are presented. Details will appear in another publication.

It seems from this study that, generally speaking, the pure limestones belonging to the bioherms or biostromes contain no palynomorphs. On the other hand, the shales and argillaceous limestones, when not too greatly altered, generally contain many acritarchs. As regards the distribution of the acritarchs in the Frasnian, it is noticeable that the populations are very monotonous in those shales deposited at the same time as biohermal growth; the genus Micrhystridium generally dominates. On the other hand, in the argillaceous sequence which correspond to phases of subsidence separating reefal horizons, the populations are much more varied. Spores were fairly rare in the sequence studied.