Akeshak Fm

The type section is located at Akeshak Mt., 15 km north of Zhaosu City, Xinjiang. It was named by Tan Hongbing et al. in 1975−1976, and formally cited in Regional Stratigraphical Scale of Xinjiang in 1981.

Limestone. A suite of dark-gray to gray neritic carbonate rocks and lesser amounts of continental clastic rocks. Consists mainly of bioclastic limestone, oolitic limestone, crystalline limestone, sandy limestone, marl, sandy shale, sandstone, conglomerate, siltstone, tuff, tuffite and tuffaceous sandstone. At Akeshak Mt. type section, the lower part is composed of grayish green−grayish purple volcanic tuff, tuffaceous sandstone, tuffaceous siltstone, volcanic breccia and pebbled coarse-grained sandstone; and the upper part is dominated by bio-limestone, clastic limestone, oolitic limestone and marl intercalated with siltstone and calcareous sandstone; with an exposed thickness is 1040 m. The thickness varies greatly from 300 m to 9338 m, generally less than 2000 m.

Contains Brachiopods Linoproductus sp., Gigantoproductus sp., Striatifera striata, Echinoconchus elegangs, Dictyoclostus sp., and Waagenoconcha sp.; corals Arachnolasma sinense, Caninophyllum sp., Gangamophyllum sp., Kueichouphyllum sp., and Yuanophyllum kansuense; Fusulinid: Eostaffella sp.; as well as gastropods, trilobites, bryozoans, etc.

It is interpreted as a neritic shelf facies, and locally with paralic facies.