Chumulong Fm

South Lhasa Block - Linzhou Basin. The Chumulong Formation was established by Luo Zhongshu in 1973. The section for the designation is in Chumulong of the Lhunzhub County, Xizang (Chen Chuzhen and Wang Yujing, 1984). The reference section is in the Quesang Village of the Doilungdeqen County of Lhasa, Xizang.

In 1953 Li Pu et al called the coal-bearing strata and red beds as the Jurassic-Cretaceous series. In 1973 Luo Zhongshu called the lower part of the series as the Lhasa Group in the “Age and Classification of the Coal Series and the Red Beds in the Lhasa Area of Xizang”. The lower part of the Lhasa Group is called the Linbuzong Fm and the upper part the Chumulong Formation, which have been assigned to the Lower Cretaceous. In 1979 the Comprehensive Geological Survey Team of the Xizang Bureau of Geology and Mineral Resources called the Linbuzong Fm the Linbuzong Gr of which the lower part is called the coal-bearing member equivalent to the Linbuzong Fm and the upper part is called the clastic rock member equivalent to the Chumulong Formation, which were assigned to the Lower Cretaceous. In 1983 Wang Naiwen et al continued to use the Chumulong Formation established by Luo Zhongshu, but did not used the name of the Lhasa Group. They partially assigned mudstone, marl and limestone bearing marine fossils in the upper part of the Chumulong Formation to the Takena Fm above it. The Chumulong Formation named by Wang Naiwen et al is adopted in the present lexicon.

Lower part of the Chumulong Formation is represented by dark gray, gray green and purple red phyllitic slate, siltstone, quartz sandstone, gravel-bearing quartz sandstone and gray conglomerate with slate. Middle part is dark gray siltstone intercalated with gray white quartz sandstone and dark gray calcareous sandstone. Upper part is dark gray and gray black thick-bedded siltstone and mudstone. The formation is 795 m thick.

The formation yields floras Zamiophyllum buchianum in the Lhasa area.