Keankuduk Fm

Eastern Junggar. The type section is located at 1.8 km southeast of Ke’ankuduk near Kokesairgy Mt., north of Zhifang in eastern Junggar. It was named by No 2 branch Team of Xinjiang No 1 Team of Regional Geological Survey in 1975, and Yang Shipu et al quoted it formally in 1981.

Synonym: Ke'ankuduk Fm

Tuffaceous sandstone. This formation outcrops in northeast direction along the slope of Kokesairgy Mt., north of Zhifang. It is 1049 m in thickness.

Lower part is composed of yellowish-green, thin- to medium-bedded tuffaceous sandstone, sandy conglomerate, intercalated with radiolaria-bearing chert.

Upper part consists of variegate beds, dominated by tuffaceous sandstone, often intercalated with tuffaceous conglomerate, breccia and many beds of radiolaria-bearing sedimentary tuff.

The well-developed bands and laminations, composed of different components, colors and grain sizes, form Bouma sequences. One of the characteristics of this formation is the well-developed dazzlingly beautiful bluish green, sky blue and emerald green sedimentary tuff bands with horizontal bedding, which are usually caused by varying enrichment in radiolarians. In some places, boulder conglomerate beds of 10-20 m in thickness may extend for several kilometers. Pebble compositions are complex, and include intermediate to acidic eruptive rock clasts and crinoidal limestones, most of them are rounded-angular in shape and poorly sorted.

Lower part yields Plant fossil Lepidodendropsis, Lepidosigillaria. Upper part yields Plant fossil Lepidophloeum rhombicum, Radiolaria Spongentaclinia.