Sandaoqiao Fm
(65), Guadalupian Epoch (Middle Permian)
Type Locality and Naming
The type section is located at the locality extending from the Toudao Village of the Dongda River to the Dashipao area 50 km to the north of the Baoxing County Town, Sichuan Province. It was named by the West Sichuan Research Team under the Chinese Academy of Geological Sciences in 1965.
Lithology and Thickness
Limestone. Composed mainly of grey-black brecciated limestone, with its top being a layer of 1.7-m-thick black thin-bedded limestone. Thickness is 47 m.
Relationships and Distribution
Lower contact
Disconformable contact with the underlying Dongdahe Fm whose top part consists of a layer of thin- and medium-bedded limestone intercalated with shale
Upper contact
Disconformable contact with the basic volcanic rocks at the base of the overlying Dashibao Fm
Regional extent
The lithology of the formation is variable. It is distributed in the Kangding (303 m), Baoxing (50 m), Wenchuan (40 m). In the Songpan area (200 m) there are found dolomitic limestone and dolomite, yielding Fusulinida represented by Neoschwagerina craticulifera, Neomisellina, as well as corals.
GeoJSON
Fossils
Fusulinida fossils represented by Neoschwagerina simplex and Verbeekina crassispira.
Age
Depositional setting
It is interpreted as a shallow-sea carbonate-platform.
Additional Information