Ecological Succession from Corals to Coralline Algae in Eocene Patch Reefs, Northern Spain

Abstract

Both corals and coralline algae can be dominant reef-building organisms in the Recent and Tertiary. The best-documented co-occurrence is where corallines replace corals in the intertidal zone producing the coralline algal ridges to reefs (Adey 1975, Littler and Doty 1975). In this paper we investigate the repeated overgrowth of corals by thick coralline algal encrustations in an Eocene patch reef. In this case the overgrowing coralline genera are not those typical of exposed intertidal algal ridges, but today occur either at moderate depths in the tropics or as shallow shaded floras. The evidence in these reefs points to a shallow shaded flora, since the coralline crusts occur both over and around the corals and, in this siliciclastic setting, were probably living in turbid waters.