Suzhong Fm

The type section of Suzhong Formation is located 3.5 km north of Suhuhe Station of the Yirsie-Suyuan Forest Railway; or 5.5 km southwest of the Station of Suzhong Working Area of the Forest Railway (120°07’30”E, 47°23’40”N). It was measured by Tang (1984). The Suzhong Formation was named by Tang (1984). The name is derived from the railway station of Suzhong Working Area of the Yirsie-Suyuan Forest Railway in Yirsie Township, Arxan City, Xinggan Meng, Inner Mongolia Autonomous Region.

Synonym: （苏中组）

The Suzhong Formation is a carbonate sequence with minor clastic rocks; and in the type section the formation is 151.12 m thick. The formation in type section are divided into 6 beds, from bottom up: 1, greyish white honeycomb-like crystalline limestone with the basal part cut by fault (>56.42 m thick); 2, grey honeycomb-like crystalline limestone (24.97 m); 3, dark grey, thick-bedded crystalline limestone (14.59 m); 4, black shale (9.00 m); 5, black crystalline limestone (18.68 m); 6, bluish grey, thick-bedded limestone with the upper part cut by fault (>33.26 m).

The Bed 5 of the type section yields fragment of trilobite; The Bed 6 yields rich archaeocyathids Ajaciacyathus sp., Archaeocyathus yavorskii, A. sp., Coscinocyathus sp., Densocyathus sp., Ethmophyllum hinganense, E. simplex, E. sp., Protopharetra cf. bipartita, P. sp., Robustocyathus yavorskii, Syringocnema sp., and Syringocyathus？sp.