Sisuo Fm
Type Locality and Naming
The type section lies at Sisuo, between the south slope of Deriangma Mt. to Xiala Mt., 6 km northeast of Yunzhug Township, Xianza, Tibet. It was named by Yang Shipu and Fan Yingnian in 1982.
Synonym: upper Yongzhu Fm (as implied by Shuzhong Shen et al (2019; Permian integrated stratigraphy and time scale)
Lithology and Thickness
Sandstone. Dominated by light-gray and gray-green moderately thick-bedded medium- to coarse-grained and fine-grained quartz-rich sandstone, feldspar-rich sandstone and siltstone, intercalated with thin-bedded clayey limestone or limestone lenses; 142 m thick.
Relationships and Distribution
Lower contact
Conformable contact with the underlying Yongzhu Fm
Upper contact
Conformable contact with the overlying Laga Fm?
Regional extent
Distributed at Yunzhug Township of Xianza County and the Gemangco area on both wings of the Tarma anticline.
GeoJSON
Fossils
Corals Cyathaxonia lomonosovi, C. tenuiseptatus, C. sisunensis, Stereolasma minor, Rhopalolasma sisunensis, Lophophyllidium sp., Amplexus stuckenbergi; Brachiopods Pugnax tibetensis, Krotoria pustulata, Phricodothyris asiatica, Rugoconcha xainzaensis.
Age
Depositional setting
It is interpreted as a
Additional Information
The C and O isotope analyses of the formation show that the δ13C values vary from −2.89‰ to −18.58‰, averaging −6.06‰; the δ18O values from −4.52‰ to −12.94‰, averaging −10.08‰. According to paleomagnetic determination, the Xainza area lay at 21°S during the Carboniferous.