Laozhai Fm
Type Locality and Naming
The type section is at Shanpianshan-Laozhai in Gum Township, Wenshan County, Yunnan. The Laozhai Fm was named by No.2 Yunnan Party of Regional Geological Survey in 1973, and was published by Yunnan Bureau of Geology and Mineral Resources (1987). The term Laozhai Fm was not used until 1980 when Wang Ruzhi suggested that it should be available.
Synonym: (老寨组）
Lithology and Thickness
The formation is composed of light gray, grayish yellow medium-bedded quartz sandstone and feldspathic quartz sandstone intercalated with grayish green and yellowish green shale. Developed cross-bedding, ripple mark and trace fossils are found within the sandstone. In the type area, the Laozhai Fm is 786 m thick.
Relationships and Distribution
Lower contact
This formation lies conformably on the limestone at the top of the Shanpianshan Fm
Upper contact
It is conformably overlain by the marl and siltstone at the base of the Lengshuigou Fm (present Shizipu Fm).
Regional extent
The Laozhai Fm is exposed in Wenshan, Pingbian and Xichou, Yunnan, with a thickness of 638-798 m, coarsening sediments and thinning bedding from southeast to northwest.
GeoJSON
Fossils
The Laozhai Fm yields trilobites Megalaspides, Taihungshania cf. omeishanensis, Psilocephalina sp.; brachiopods Tritoechia sp., Mimella sp.; graptolites Didymograptus eobifidus, D. protobifidus, D. bifidus; cystoids and bivalves.
Age
Depositional setting
Additional Information