The Upper Ordovician Microfossil Assemblages from the Pagoda Formation in Zigui, Hubei Province

The Pagoda Formation is a lithologically and biologically distinctive unit among the Upper Ordovician. The strata are characterized by a nodular limestone, which yields fossil assemblages of high diversity. Conodonts of 14 genera 20 species(6 undetermined species) and ostracods of 14 genera 26 species(16 undetermined species) are identified. In addition, spherical radiolarians and minute-walled foraminifers were first reported from this formation in South China. The conodont assemblage is attributed to the Hamarous europaeus Zone, which indicates the Early Katian Age. The conodont HDS biofacies, along with thin-shelled ostracods, spherical radiolarians and foraminifers, suggest relatively deep and quiet water depositional environment. Accordingly, these fossil materials not only enrich the diversity of the Pagoda biota, but also provide evidence for discussion of depositional environments and stratigraphic correlations for the Pagoda Formation.