Xishuanghu Fm
Type Locality and Naming
Wu Ruizhong et al. named this formation in 1985. The named section is located about 3 km southwest of the Xishuanghu in northern Shuanghu County, Tibet. In 1985, Wu Ruizhong et al. discovered a set of carbonate rocks and fine clastic rocks with rich ammonoids overlying the Yingshuiquan Fm, and named it as Xishuanghu Fm and its age was determined to late Early Triassic. Rao Rongbiao et al (1987) classified the corresponding strata into the Yingshuiquan Fm. The original meaning of the Xishuanghu Fm is maintained.
Synonym: Chen Dequan (1987) named the “XiShuanghu Formation” (representing the early Triassic Indian strata in the Shuanghu area) with the same name as this formation, and should be abandoned.
Lithology and Thickness
Mainly dark gray microcrystalline limestone, gravel limestone, marl limestone, with a small amount of calcareous quartz sandstone. Thickness is 540 m.
Relationships and Distribution
Lower contact
The bottom boundary is marked by the appearance of gray microcrystalline limestone above the underlying Lower Triassic Yingshuiquan Fm. The Xishuanghu Fm and the underlying Lower Triassic Yingshuiquan Fm are continuous deposits.
Upper contact
The top boundary is marked by the appearance of gray green sandstone at the bottom of the overlying Upper Kangnan Fm. Xishuanghu Fm and the overlying Middle Triassic Kangnan Fm are continuous deposits.
Regional extent
The group is mainly distributed around the Shuanghu County office in Shuanghu County, Tibet, from Rechaka to Kangruchaka
GeoJSON
Fossils
Ammonoids are the main fossils; and include Albanites sp., Xenodiscoides sp., Hungarites sp., Gymnites sp., Ptychites cf. eusomus etc.
Age
Depositional setting
Additional Information