Bijdrage tot de kennis der genese van de vuursteenhorizonten

In the cretacious chalk of the Netherlands, Belgium, France, England and Denmark most flint horizons have been developed in hardground horizons. Significant examples can be studied near Maastricht and at the French channelcoast. In accurate statigrafic profiles flint horizons represent an important litho-stratigrafic value. The existance of flint horizons in hardground horizons indicates that they must be postgenetic to the hardground horizons. In the lower layers of the overlaying chalk no reworked flint occurs in discordant levels between chalks with flint, while many reworked fossiles do occur in such levels. This indicates that at the time of the formation of the discordance levels no flint was present in the quality as we find it now.