Guomugou Fm

It was named by the Seventh Geological Team of Qinghai Geological Bureau and Nanjing Institute of Geology and Palaeontology of Chinese Academy of Sciences in 1976, and was first publicly cited by Qinghai Geological and Mining Bureau in 1991. The named section is located in Guomugou-Jiangligo, Tongren County, Qinghai.

Synonym: In 1955, Liu Dongsheng named the section around the mouth of Longwuji River (also known as Baoan River) in Jianzha County, Qinghai Province, and created the name Longwuji River System to represent a set of black-green and partly purplish-red metamorphic slate sandstone system of the Lower Triassic in eastern Qinghai (actually including the Middle Triassic). 1976, a meeting on the stratigraphy of the marine Triassic and Jurassic faults in the northwest area decided to call the Lower Triassic in the area the Longwuji Group. 1976 The Seventh Geological Team of Qinghai Geological Bureau and Nanjing Institute of Geology and Paleontology divided the group into two groups, the lower part is called Guomugou Group and the upper part is called Jiangligou Group. They represent the clastic-based deposits of the Early Triassic Indian and Olenekian stages in eastern Qinghai, respectively. It was later used by Qinghai Geological and Mining Bureau (1991).

Black and dark gray conglomerate, coarse sandstone and sandstone dominate, interspersed with siltstone, mudstone, muddy striped tuff and tuff, with hieroglyphic impressions, interlacing laminations, wave marks, scouring surfaces and other surface structures on the bottom surface of the upper sandstone. It is 2172 m thick.

Ammonoids: Lytophiceras sp., Gyronites sp., Ophiceras sp., Dieneroceras sp., Ambites sp. and Gyrophiceras sp.; Bivalves: Posidonia cf. circularis, Pesudoclaraia cf. wangi, P. cf. wangi minor, Claraia cf. griesbachi.

This group is turbid-flow sediment.