The Cao Bang basin is a pull-apart structure formed along the Cao Bang-Tien Yen fault and surrounded by low mountain and hill ranges, 20km in length and 7-8km in width. Basement rocks are Lower Triassic volcanic-terrigenous sediments, sometimes Carboniferous-Permian limestone. The section includes two parts, the lower part being rocks of Cao Bang Formation (E2cb), and the upper part being rocks of Na Duong Formation (E3-N1nd), containing coal seams and plenty of leaf imprints and mollusk fossils. The leaf imprints are present in almost every rock layer, consisting of about 63 species of the subtropical forest plants Quercus cf. lobbii-Diospyros brachysepala (Trinh Danh, 1993, 1996, 1998). Mollusca fossils mainly consist of the bivalves: Acuticosta caobangensis, Solenaia sp., Pseudobaphia cf. biessiana, Cristaria sp., Cuneopsis sp., Oxynaia aff. jourdyi, Discomya af. radulosa. Gastropods are rare and consist only of small sized Viviparous sp. (Tchelsov Iu. G., Trinh Danh, 1966; Tchelsov Iu. G., 1968). This section is among the best of its kind in Vietnam and can be used for scientific research, education while the surrounding landscape is very spectacular, suitable for sightseeing.
Neogene coal-bearing sections in Cao Bang City