The Williamsburgh Bed is a regionally extensive bed found across western New York State. It is rich in conodonts, carbonized wood, and pyrite and represents a disconformity in the upper West River Shale. It is located approximately 2 m below the base of the Middlesex Shale, the base of the Sonyea Group. The conodont fauna is dominated by Mesotaxis asymmetrica, M. ovalis, Ancyrodella rugosa, Ad. alata, Ad. gigas, Ad. n. sp. V, Ad. n. sp. W, Polygnathus ectypus, Po. dubius dubius, Po. alatus, Po. pennatus, Po. sp., and Palmatolepis transitans, which are indicative of MN Zone 4 of the Frasnian conodont zonation.