Wangjiadian Fm

The type section is located at Wangjiadian, 24 km southwest of Zhangxian County, Gansu. The reference section is north of Dazhuang, 40 km west of Zhangxian County, Gansu. It was named by Xi’an Institute of Geology and Mineral, and Qin Feng, Gan Yiyan formally quoted it in 1976.

Siltstone. In the Wangjiadian section, only the Lower part of this formation outcrops and is dominated by thin-bedded dark-gray clayey siltstone, intercalated with few beds of fine-grained sandstone and clayey limestone, and calcareous siltstone. The outcropping thickness is more than 1985 m.

Sandstone. In the Dazhuang section located 23 km west of Wangjiadian section, the formation is dominated by dark-gray to dark-greenish-gray thin- to medium-bedded fine-grained quartz sandstone, intercalated with thin-bedded siltstone with four beds of thin- to medium-bedded and lens-like bioclastic limestone; and it more than 778 m thick.

The lower part of Wangjiadian section yields brachiopods Hunanospirifer ninghsiangensis, Cyrtospirifer sp., Cleiothyridina kusbassica, Ptychomaletoechia cf. kinlingensis, Plicochonetes cf. elegans, Rugosochonetes cf. hardrensis, Semiproductus tykhtensis, plant fossils Leptophloeum rhombicum and spores; and the upper part of the Dazhuang section yields coral-brachiopoda fauna Beichuanophyllum paragenesis, Enniskillenia enniskilleni, Sychnoelasma cf. konincki, Hunanospirifer aff. wangi, Plicatifera cf. zyabrovensis, Schuchertella gelaohoensis etc.