Yinchanggou Fm

The type section of the Yinchanggou Formation was is Yinchanggou section. It lies about 7 km northeast of Jinjiang Town and was measured by the No. 4 Brigade of Yunnan Regional Survey Team in 1984 (99°53’E, 27°12’N). In the type section, only upper 310 m of the formation is exposed. In the type section the formation is 310.0 m thick. The Yinchanggou Formation was named by Leng (1983). The name is derived from Yinchanggou Gully in Jinjiang Township, Shangri-La City (county level), Diqing Tibetan Autonomous Prefecture, northwestern Yunnan Province.

Synonym: （银厂沟组）

The Yinchanggou Formation is principally a sequence alternated by fine clastic and carbonate rocks. The outcrops of the formation in the type section is divided into six lithologic beds, from bottom up: 1, dark grey, thin- to medium-bedded siltstone, alternated with muddy slate (over 14.6 m thick); 2, grey, dark grey, thin- to medium-bedded slate, alternated with dolomite and dolomite, and with a layer of dolomitic breccia in the lower part (91.7 m); 3, grey, dark grey, thin- to medium-bedded dolomite (85.1 m); 4, greyish white dolomitic siltstone and slate with interbeds of dolomite (19.9 m); 5, Dark grey, thin- to medium-bedded dolomite (19.9 m); 6, grey, greyish white, medium- to thin-bedded dolomitic siltstone with interbeds of dolomite and silty slate, and with ripple mark on bedding surface (32.8 m).

The Bed 1 of the formation yields trilobites Kunmingaspis yunnanesis (Figure 1.44), Kailiella guizhouensis? Pseudosolenoparia cf. yankongensis, Wuxunaspis guizhouensis?, Douposella cf. peudoqingzhenensis and the Bed 2 yields brachiopod Eoorthis aff. edwardsi, and Oncolite Osagia sp.

[Figure: Kunmingaspis yunnanensis Zhang, 1964, from Yinchanggou Formation, Yinchanggou in Jinjiang Township, Shangri-La City, northwestern Yunnan Province, all dorsal views. 1, 2 cranidium and the same cranidium retrodeformed, NIGP124308; 3, incomplete cranidium, NIGP124309; 4, incomplete cranidium NIGP124310. Scale bar = 2 mm.]