XiukangTri Fm

Type locality located in Xiukang Beishan in Zhongbei Region, Lazi County, Tibet. Yin Jixiang et al. (1983) named this Formation. In 1983, Tibet Geology and Mineral Bureau District Survey Team named the upper Triassic strata in the Lazi area "Xiukang Gr" in the 1:1 million Xigaze sheet regional geological survey report. [NOTE: In this same Lazi and Zhongba region, the Permian Lexicon also has a Xiukang Fm, which is 200 m of dolomitic limestone, named by Shen Huaibin in 1984; and currently assigned as late Middle Permian. Therefore, until this potential mis-dating (?) is resolved, then this Triassic one is given a qualifier-suffix in this Lexicon entry.]

Synonym: In 1978, the Second Geological Team of the Tibet Geological Bureau named the Middle and Lower Triassic in the Lazi area as the Zhongbei Gr. Yang Zunyi et al. (2000) continue to use this meaning and believe that the main age of this group is the Anisian period, and whether it is extended to the Ladinian period remains to be confirmed

The XiukangTri is dominated by carbonate rocks with a small number of clastic rocks. Lower part is interbedded with limestone and shale, with a thickness of 46 m. Middle part is shale interbedded with limestone lens and sandstone with a thickness of 55 m. Upper part is limestone interbedded with (or contain) shale a thickness greater than 77 m.

The lower and upper limestones are rich in thin-shelled bivalve fossils, while marls generally contain calcified radiolarian fossils. Bivalves in the lower part: Halobia rugosoides, H. sp., H. aff. subcomata, Daonella moussoni; Bivalves in the upper part: Halobia sp., Daonella indica.

It is interpreted as deep-water sediment environment.