Algues et microfossiles problématiques du Dévonien Moyen du « Fondry des Chiens » (bord sud du Synclinorium de Dinant, Belgique) : implications paléobathymétriques

This study is concerned with the distribution of algae and microproblematica observed in a regressive sequence of carbonate rocks that accumulated open marine to lagoonal palaeoenvironments. The basal algal microflora is reduced to a few chlorophytes (Udoteacean, Dasycladales), but increases rapidly in number and diversity in the flanks of the bioconstructions, then explodes in the restricted facies (“Pseudo-udoteaceans”). An attempt to estimate the bathymetry is based on the palaeoecological constraints of the identified algae. We conclude that the maximum water depth did not exceed the twenty meters. The regressive sequences being made of around sixty meters (of reefal, perireefal and lagoonal carbonates), subsidence is believed to be the main mechanism controlling accommodation space.