Composition and significance of the Katian (Upper Ordovician) conodont fauna of the Vaux Limestone (“Calcaire des Vaux”) in Normandy, France

摘要

Study of new conodont collections from the Vaux Limestone exposed at its classical locality at Saint-Hilaire-la-Gérard in the Sées syncline, the conodont fauna of which was previously described in a preliminary way by Weyant et al. (1977, Un épisode calcaire ashgillien dans l'est du Massif armoricain; incidence sur l'âge des dépôts glacio-marins fini-ordoviciens. Comptes Rendus de l’Académie des Sciences, Paris, 284, Série D, 1147-1149), has provided significant new information about Late Ordovician conodonts from Normandy. A more precise age of this formation has been established based on an unexpectedly abundant conodont fauna of low diversity. Representatives of Amorphognathus, Hamarodus, Sagittodontina, Scabbardella and Eocarniodus are present and the fauna is referable to the middle Katian-lower Hirnantian A. ordovicicus Zone. Our study, the first illustrating Ordovician conodonts from Normandy, shows that the fauna is closely similar to middle Katian faunas from other parts of continental Europe and represents the Sagittodontina robusta-Scabbardella altipes biofacies of the Mediterranean Province.