Duliujiang Fm

The type section of the Duliujiang Formation is the Sandu section lying on the riverside of the Duliujiang River, located between Zhalagou and Sanhe towns, about 2 km east of Sanhe Town, the seat of Sandu Shui Autonomous County. Except for the thickness and the fossils collected from the formation, no lithology was described by Qian (1961) when he publishes the formation. A better section measured at the Yatang Village in Sandu County was selected as representative section of the formation (117°55’E, 26°03’N) by Guizhou Bureau of Geology and Mineral Recourses (1987). The Yatang section lies 5 km north of the Sanhe Town, and was measured by Cai Ying, Yin Gongzheng and others in 1983. The Duliujiang Formation was first published by Qian (1961). The name is derived from Duliujiang River in southeast of Guizhou Province. The river originates from Dushan County, Qiannan Buyi-Miao Autonomous Prefecture, Guizhou Province, flows eastward through Sandu, Rongjiang, and Congjiang counties of Guizhou and then enters into Guangxi Zhang Autonomous Region. The formation name was originally appeared in a 1959 manuscript by Yang Jingzhi, Qian Yiyuan and colleagues from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.

Synonym: （都柳江组）

The Duliujiang Formation is a clastic and carbonate sequence. Lower part of the formation consists of greyish yellow and bluish grey varicolored shale with deposits of spotted cinnabar, intercalated with argillaceous limestone or limestone lenses; Upper part is dominated by blackish grey or brownish yellow sandy shale and sandstone, intercalated with thin-bedded unpurified limestone with a tendency of increasing limestone and decreasing argillaceous rocks upwards in section. Occasionally, the formation contains carbonaceous shale and has highly-carbonaceous shale at the top. In the Yatang section, the formation is 405.50 m thick.

The lower part of Duliujiang Formation yields trilobites Kunmingaspis sp. and Pagetia latilimbata, and the upper part yields trilobites Lisania sp., Peronopsis sp., Oryctocephalus sp., and Pagetia latilimbata. The formation also yields sponge spicule Protospongia sp.