Nadu Fm

The naming section is located in the vicinity of Nadu and Xiaotang, Tiandong County, Bose (Baise) basin, Guangxi. Named by the Guangxi Petroleum Party in 1959.

In ascending order the formation is divided into three members: Lower Coal-bearing Member, grayish green siltstone with lime mudstone and sandy mudstone, containing several coal beds and locally intercalated with organic marlstone beds, the base of which contains pebbly sandstone; Mudstone Member in the middle, brown mudstone and dark brown mudstone with calcareous and siderite concretions; Upper Coal-bearing Member, alternating beds of gray and greenish gray mudstone and sandy mudstone, with several coal beds and sandy conglomerate lenses. The total thickness is ~700 m.

It yields abundant mammals, including 20 genera and over 25 species such as Eomoropus cf. quadridentatus, Caenolophus sp., Anthracothema rubrica, Anthracokeryx birmanicus, Huananothema imparilica, Heothema bellia, Indomeryx cotteri and Notomeryx beisensis. This fossil assemblage is characterized by the dominance of artiodactyls and especially anthracotheres. Many genera in the underlying Dongjun Formation, such as Andrewsarchus, Eusmilus and Eudinoceras, are no longer found in this formation; on the contrary, typical late Eocene genera and species such as Anthracokeryx, Indomeryx appear. They may correlate with related genera and species in the upper part of the Lumeiyi Formation, Yunnan, and in the Pondaung sandstones of Burma. Therefore, the age of this formation should be late Eocene. According to Xu Jie’s identification, the fossil mollusks collected from the Nadu Formation include 12 genera or species, such as Kwangsispira accelerate, Tulotoma kwangsiensis. Ostracods such as Limnocythere sp. and Candoniella sp. are found in strata equivalent to the Upper Coal-bearing Member in Linfeng and Nadu. In addition, there also occur plants, sporopollen and other groups of fossil. Wu Yushu’s (1981) study of sporopollen suggests that angiosperms are the main assemblage, the sporopollen assemblage is dominated by angiosperms, in which Ulmus and Quercus are the dominant genera; gymnosperms are mainly composed of Pinaceae pollen; spores of pteridophytes are only found sparsely. This assemblage suggests the development of lakes and swamps, occurrence of mixed forest composed of deciduous broadleaf forest and evergreen forest and a warm and moist climate.

It is lakes and swamps.