Yanwashan Fm

The type section is at Village Yanwashan 15 km east of Changshan City, Zhejiang. The Yanwashan Fm is derived from the Yanwashan Series proposed by Liu Jichen and Zhao Yazeng (Chao Y.T.) in 1927. Lu Yanhao et al. (1955) renamed the Yanwashan Series the Yanwashan Fm. Zhang Ridong (1964) reported the nautiloids from the Yanwashan in Huangnigang, Jiangshan, and correlated it with the Baota Fm. An (1987) established the conodont zones.

Synonym: (砚瓦山组)

The formation is composed of purple, grayish green thick-bedded nodular limestone, with calcareous shale in the upper part. In the type area, the Yanwashan Fm is 54 m thick.

In Jiangshan and Changshan, the lower part of the Yanwashan Fm yields conodonts of P. anserinus assemblage and P. lingulatus assemblage. Additionally, the Yanwashan Fm generally yields nautiloids Sinoceras chinense yanwashanense, Michelinoceras huangnigangense and trilobites Hammatocnemis tetrasulcatus, Paraphillipsinella. In Xiushui of northwestern Jiangxi and southern Anhui, the Yanwashan Fm is composed of dark gray and gray nodular limestone intercalated with thin-bedded limestone and argillite. Zhou Zhiyi, Lu Yanhao et al. (1976) described the trilobite Jiangxilithus latimargins and Xiushuilithus xiushuiensis from the Yanwashan Fm in Xiushui of northwestern Jiangxi and southern Anhui.