Lanmutan Fm

The Lanmutan Fm was named by Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences in 1977, and was published by Zhang Wentang et al. (1982). The Guizhou Bureau of Geology and Mineral Resources (1987) reported the type section in the vicinity of the Lanmutan parking lot west of Yangnengzhai in Sandu, Guizhou.

Following the naming of the Lanmutan Fm, Guizhou Bureau of Geology and Mineral Resources (1987) restricted it to the siliceous limestone in the upper part of the previously defined Lanmutan Fm, and correlated its lower part with the Guniutan Fm. Considering the different lithology of the lower part from the typical Guniutan Fm and its less and variable thickness (2-21 m), the present book maintains the previous definition of Lanmutan Fm.

Synonym: (烂木滩组）

In the type area, the Lanmutan Fm is divided into two parts. Lower part is 2-21 m thick, and is composed of purple limestone. Upper part is represented by 60 m thick bluish gray thin-bedded cherty limestone intercalated with siliceous mudstone and chert, and contains rare fossils.

It yields abundant cephalopods Vaginoceras, Michelinoceras, Protocycloceroides, Dideroceras and conodont of Pygodus serra assemblage at the lower part, and only sponge-spicule has been found from the upper part.