Sanbaoao Fm
Type Locality and Naming
In 1974, Jiang Jiagong et al. of Hunan Coal Exploration Group named the Middle Triassic sediments dominated by dolomitic limestone near the Laowu Reservoir in Yongxing, Hunan as the "Laowu Section". In 1986, the "Laowu Member" and the underlying bivalve strata at about 100 m were combined into one and named as the Sanbao Au Formation to represent the Middle Triassic deposits.
Synonym:
Lithology and Thickness
It is composed of a set of argillaceous limestone, marl, dolomitic argillaceous limestone, limestone, dolomitic limestone and dolomite. Mainly argillaceous limestone and marl, sandwiched with mica calcareous siltstone at the bottom, and the dolomitic limestone and dolomite appear when the content of dolomite increases in the upper part. The thickness is 320 ~ 609 m.
Relationships and Distribution
Lower contact
It is conformable contact with the underlying Guanzishan Fm
Upper contact
Next younger regional unit is the Chutanlong Fm of Carnian.
Regional extent
The distribution of this group is limited and can only be seen in Songjia, Xiaonanqiao, Sanbao Au and Gongting, Yongxing, Hunan. The measured thickness is residual thickness, because the distribution in the core of syncline is denudated without peaking.
GeoJSON
Fossils
It contains bivalve fossils Posidonia wengensis, Asoella subillyrica, Posidonia ussurica, P. cf. Japonica, Entolium liscaviensis; foraminifera fossils Glomospira-Meandrospira zone and brachiopod fossils.
Age
Depositional setting
It is interpreted as semi-closed shallow sea deposit.
Additional Information