Nanzhuangzi Fm

The type section is at Kushuigou south of Nanzhuangzi in Chedao, Huanxian, Gansu. The Nanzhuangzi Fm was named by Lin Baoyu, Lai Caigen and Guo Zhenming in 1975, and was named by Gansu Compiling Group for Regional Stratigraphic Scale (1980). Fei Anqi et al. (1983) included the Nanzhuangzi Fm in the overlying Chedao Fm. An et al. (1990) suggest that the lithology of the Nanzhuangzi Fm and the Chedao Fm are different, and the Nanzhuangzi Fm should be maintained.

Synonym: (南庄子组）

The Nanzhuangzi Fm is composed of thick-bedded to massive calcirudite and thin-bedded limestone intercalated with calcareous and dolomitic mudstone. In the type area, the Nanzhuangzi Fm recorded an incomplete thickness of 29.4 m.

This stratigraphic unit yields abundant trilobites and conodonts of Pygodus serra zone (lower) and Spinodus spinatus zone (upper), and is roughly equivalent to graptolite Husterograptus teretiusculus zone.