New biological zonation of a late Jurassic coral reef complex (Lorraine, France)

Late Jurassic coral assemblages and their ecological reef zonation (as a function of water depth) were studied in 490 m deep shafts dug for the underground laboratory of the French National Agency for Radioactive Waste Management (ANDRA). Based on a quantitative approach, several ecozones are distinguished. Identified ecozones represent evolution from the initiation of the reef during a shallowing of depositional environments to the end of the platform progradation in sheltered settings. Ecozones are defined by the most abundant genera Dimorpharaea , Microsolena , Rhabdophyllia, Comoseris , and Stylina . The slight differences between these coral associations when compared to regional outcrops can be explained by the more distal palaeogeographical location of the studied section, close to the platform margin. This study strengthens the zonation model proposed for coeval Oxfordian outcrops in the Jura Mountains with the exception that the Rhabdophyllia ecozone replaces the Dendraraea ecozone. Other comparisons are proposed and take into account the progress in coral taxonomy in the past 15 years.