Tonggao Fm

The type section is at Wuliguan in Datang north of Sandu City, Guizhou. The Tonggao Fm is derived from the Tonggao Shale proposed by South Guizhou Party of Stratigraphy, Chinese Academy of Sciences in 1958, and was published by Li Jijin and Chen Xu (1962). “Tonggao” is probably the mistaken writing of “Gaotong”. Considering the widely accepted name Tonggao Fm, Guizhou Bureau of Geology and Mineral Resources (1987) suggested that the name Tonggao Fm should be maintained. Li and Chen (1962) reported the graptolite sequences of the Tonggao Shale. In 1977, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences renamed it the Tonggao Fm, and confined it to be a sequence of graptolite-bearing shale. At the same time, they named the strata overlying the Tonggao Fm the Yangnengzhai Fm, a suggestion followed by Zhang Wentang (1982). Guizhou Bureau of Geology and Mineral Resources (1987) suggested that the lithology of the redefined Tonggao Fm and Yangnengzhai Fm change transitionally, and included the Yangneng Fm in the Tonggao Fm, which is divided into the Xiayangao Shale Member in the lower part, and the Yangnengzhai Member in the upper part.

Synonym: (同高组）

The formation is divided into two members. Lower member, i.e., the Xiayangao Member, is composed of first gray, grayish green and then yellowish gray shale. Upper member, i.e., the Yangnengzhai Member, is represented by sandstone and shale intercalated with mudstone. The Tonggao Fm is 290-600 m thick.

The lower member yields abundant graptolites of Tetragraptus approximatus assemblage, Didymograptus filiformis assemblage and D. deflexus assemblage, in ascending order, and the upper member yields graptolites of Undulograptus austrodentatus assemblage, trilobite and brachiopod.