Hongshan Fm

The type section is located at 1 km to the northwest of the Hongshan Mt., Yichun City, Heilongjiang Province; and the reference section is situated at Shangganling Ridge of Yichun City. It was named by Zhang Hairi et al., of the 1^st Regional Geological Survey Party under the Geological Bureau of Heilongjiang Province in 1971.

Sandstone. It can be divided into three parts: Lower part is composed of grey-white coarse-, and fine-grained sandstones, intercalated with black slate and carbonaceous slate, with a thickness of 181 m. Middle part is composed of alternation of beds of pebble-bearing-coarse-grained sandstone, siltstone, fine-grained sandstone and slate, with a thickness of 323 m. Upper part is composed of grey-black and light-grey fine-grained sandstone, siltstone and sandy slate, intercalated with pebble-bearing coarse-grained sandstone, with a thickness of over 195 m. Its total thickness is 699 m.

Plant fossils (phytolites) such as the Comia yichunensis, Lobatannularia multifolia, Callipteris zeilleri, Pecopteris, Noeggerathiopsis angustifolia, Compsopteris, Supaia, Rhipidopsis and Taeniopteris, with the members of the Angara flora being predominant. Jin Jianhua et al. (1992) would think that the plant assemblage of the Lower Member of the Sanjiaoshan Fm is more or less similar to that of the Hongshan Fm.

It is interpreted as river-lake clastics.