Sanjiacun Fm
Type Locality and Naming
The type section of the Sanjiacun Formation is the upper portion of Yinchanggou section (99°53’E, 27°12’N), the same section shared by the Yinchanggou Formation. The section lies about 7 km northeast of Jinjiang Town and was measured by the No. 4 Brigade of Yunnan Regional Geological Survey Team in 1984. In the type section, the formation is 355.9 m thick. The Sanjiacun Formation was named by Yunnan Bureau of Geology and Mineral Resources (1990). The name is derived from Sanjiacun near Yinchangou in the Jinjiang Township, Shangri-La City, Diqing Tibetan Autonomous Prefecture, northwestern Yunnan Province.
Synonym: （三家村组）
Lithology and Thickness
The exposed interval of the formation is mainly a carbonate sequence that was divided into three lithologic beds, from bottom up: 1, light grey to dark grey, thin- to medium-bedded dolomite (290.3 m thick); 2, light grey, thin-bedded silty dolomitic muddy slate (17.5 m); 3, greyish white to dark grey, thin- to medium-bedded dolomite bearing nodular chert in part, with a layer of greyish muddy slate of 4 m thick at the top (48.1 m).
Relationships and Distribution
Lower contact
The Sanjiacun Fm rests conformably on the Yinchanggou Fm
Upper contact
It has no upper boundary exposed.
Regional extent
The Sanjiacun Formation is exposed in the Northern Qangtang-Simao Region. Like the underlying Yinchanggou Formation, it is distributed also limitedly, known only in the southern part of the Diqing Tibetan Autonomous Prefecture.
GeoJSON
Fossils
Age
Depositional setting
Additional Information