Laolongtou Fm

The type section is located in the area of the Jixin River, Longjiang County, Heilongjiang Province, of which the lower and middle segments of the type section are situated in the Laolongtou area, while the upper segment of the particular section is located in the Dongshan Mt. of the Sunjiafen area.It was named by the 2^nd Regional Geological Survey Party of Heilongjiang Province in 1973, and was cited officially by the Compiling Group for the Regional Stratigraphic Chart of Heilongjiang Province in 1979.

Clastics and Volcanics. Composed mainly of siltstone and sandy slate, intercalated with many layers of volcanic rocks. It is divisible into three members: Lower member consisting of yellow-green siltstone, intercalated with acidic volcanic rocks, with base of quartz-sandstone and a thickness of 330-1250 m. Middle member consisting of variegated clayey siltstone and slate, intercalated with such intermediate and acidic volcanic rocks as andesitic porphyrite and rhyolite; with a thickness of 213-969 m. Upper member consisting of yellow-brown and grey slaty clayey siltstone, intercalated with sericite-slate, and/or interbeds of micrite and intermediate-acidic volcanic rocks, with a thickness of 154-969 m. Total thickness of 2987 m.

Bivalves such as Palaeomutela cf. lunulata, P. subparallela, Palaeanodonta?; Estheria represented by Notocrypta, Bipemphigus?; Ostracoda represented by Kemeroviana?; and Plant fossils (phytolites) represented by Noeggerathiopsis derzavinii?, Schizoneura?.

It is interpreted as a lake-facies clastic-rock and intermediate-acidic volcanic-rock formation.