Nanduan Gr

The type section is located at the northwest side of Nanduan Township, Menglian County, Yunnan. It was named by the Yunnan Party of Regional Geological Survey in 1982.

Turbidites of Sandstone and Claystone. Gray, light-gray and yellow-gray lightly metamorphosed poorly sorted quartz sandstone, intercalated with yellow-green, gray, dark-gray and gray-black thin-bedded clayey slate, being a suite of flysch sedimentary assemblage. Besides the extremely thick-bedded massive structure, occasionally seen in the group are gravity flow, flute cast and pillow flow structures, shale fragment-bearing tear structure, and Neonerites facies deep-water ichnofossils. From Nanduan to Nuofu, the single-layer thickness shows a reducing trend from east to west. It is thus inferred that this group represents the products of abnormal turbidity of the deep-water continental slope on the west margin of the Lincang terrane (Liu Benpei et al., 1993). Thickness >3000 m.

The middle part yields Ammonoids Acrocanites, Epicanites sp., Kazakhoceras sp., etc. of the late Visean or early Namurian Age; the top contains abundant Visean Spore-pollen assemblages (Liu Benpei et al., 1993). Therefore, the animal fossils in the middle part might be re-deposited after having been transported by turbidity current (Fang Zongjie et al., 1992).

It is interpreted as a deep-water continental slope on the west margin of the Lincang terrane.