Shuidong Fm

Type section of Shuidong Formation is located at Shuidong Village in Da’an Township, about 25 km north of the Da’an Town, the seat of Tonghua County (126°08’E, 41°45’N). The section was measured by Tonghua Team of Jilin Institute of Geology in 1977. In the type section, the Shuidong Formation is 45.19 m thick. The Shuidong Formation was first published by Jilin Bureau of Geology and Mineral Resources (1988). The name is derived from Shuidong Village, Da’an Township, Tonghua County, Tonghua City, Jilin Province. It was originally appeared in a 1983 manuscript by Peng Yujing and Liu Eryi from the Institute of Regional Survey and Mineral Resources of Jilin Province.

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The Shuidong Formation is basically a clastic sequence. The formation is roughly divided into three parts: Lower part consists of yellowish and purplish red siltstone, glauconitic fine-sandstone bearing cellophane (phosphate-bearing) gravels; Middle part consists of purple and yellow collophane-bearing conglomerate, silty phosphorite, ferruginous phosphorite with interbeds of glauconitic fine-sandstone; Upper part consists of purplish red and mud-yellow, thin-bedded siltstone and calcareous siltstone.

The formation yields diverse small shelly fossils Aimitus? sp., Alatheca degeeni, Botsfordis cealata, Circotheca maxima, Eiffelia sp., Hyolithellus sp., Linevites daphnis, L. cf. angaicus, Lingnacea saltem, Microcornus sp., M. cf. parvulus, Ortheca koloi, Paragloborilus sp., Quadratheca jilinensis, Turcutheca sp., Yankongotheca disulcata, and Zhijinites sp.; and trace fossils Bergaueria aff. perata, and Triptichnus pedum.