Silurian Boundary Section in Ziyang, Ankang, Shaanxi

This section is along the boundary between the Silurian Llandovery Series (First Series) and the Wenlockian Series (Second Series). The section is well developed in East Qinling, especially in the Ziyang area in Ankang, Shaanxi Province, where the outcrop is adequately exposed with a continuous graptolite bed that has attracted the attention of academics in China and abroad. The section is also located at Xianzhong Goukou in Bajiaokou Village, Ziyang County, Shaanxi Province. Its lower bed (top of the Llandovery Series) is called the ‘Wujiahe Formation’ and is made up of a thin to moderately thick layer of silty slate and a thick layer of sandstone that are rich in graptolite fossils with a Cyrtogaptus sakmaricus fossil layer at the top. The upper bed (Wenlockian Series) is called the ‘Xianzhong Gou Formation’ and consists of a thin to moderately thick layer of sandstone that is also rich in graptolite fossils. The lowest Cyrtogaptus centrfugus fossil layer represents the boundary...