Abstract

After a brief consideration of the character of the outcrops of the Devonian in Belgium and northern France, illustrated by a map including the published data of French oil companies and a brief summary of the previous and current works, the structure and tectonic evolution of the region, responsible for the facies variations, are briefly described. This structure implies the existence of a pre-Gedinnian stratigraphic sequence under the Paris basin and in the Devonian basins older than the Belgian basin.

The sedimentary history is outlined with the purpose of defining the stratigraphic problem of the Devonian of the Ardennes. It can be divided into three phases: an eodevonian eoterrigenous phase, a mesodevonian and Frasnian calcareous phase, and a Famennian neoterrigenous phase. A new bathymetric method is applied to the stratigraphic analysis of this complex, particularly to the mesodevonian and Frasnian uhases.

The results presented in the plates are accompanied by a description of the palaeogeography, the difficulties and the uncertainties, the recent changes and the correlations between the facies north and south and east and west. The influence of the reefal regime on the stratigraphy is particularly studied. The facies variations, both vertical and lateral, in the basin and on the shelf, are discussed in the light of the bathymetric method expression of the tectonic evolution of the basin.

The stratigraphic correlations within the various parts of the basins of Dinant and Namur are compared with the facies correlations.

The last part is devoted to the problem of the boundaries: Siluro-Devonian, eo-mesodevonian and meso-neodevonian.