Upper Darriwilian graptolite and conodont zonation in the global stratotype section of the Darriwilian stage (Ordovician) at Huangnitang, Changshan, Zhejiang, China

Investigation of the previously little known upper Darriwilian graptolite biozone succession in the Darriwilian GSSP at Huangnitang, Changshan, China has led to the recognition of three biozones above the basal Darriwilian Undulograptus austrodentatus Biozone, namely the Acrograptus ellesae Biozone, the Nicholsonograptus fasciculatus Biozone, and the Pterograptus elegans Biozone. The Hustedograptus teretiusculus Biozone has not been identified and the post-Darriwilian Nemagraptus gracilis Biozone is separated from the P. elegans Biozone by a stratigraphic interval without stratigraphically diagnostic graptolites. Several levels in the succession have yielded index conodonts, making it possible to recognize international conodont biozones in part of the sequence. The virtually complete Darriwilian graptolite biozone succession, the good to excellent preservation of many graptolite taxa, the comprehensive construction of facilities to facilitate the study of the section, and the designation of this section as a protected National Geopark make Huangnitang an internationally unique and important geological site.