Kuche Fm

Kuqa Depression, NW Tarim. The type section is located at the south wing of the East Jidike anticline (E83°29′, N42°07′), Kuche (Kuqa) City, northern Tarim Basin in Xinjiang. Its name is derived from the “Kuche Bed” proposed by Norin (1935) in his “Tertiary of the Tarim Basin”, and was formally erected by the Regional Stratigraphic Chart Editorial Group of Xinjiang Uygur Autonomous Region (RSCEGXUAR) (1981).

Synonyms: Kuqa Fm. Gao et al. (2014a) treated the Qiulitake Fm and the Cangzongse Fm (barn brown color) as synonyms of the Kuche Fm.

Its bottom is formed by yellowish-green conglomerates. Lower part consists of yellowish-grey sandstones interbedded with yellowish-green sandstones, with conglomerates and small amount sandy mudstones. Middle part is formed by brown sandstones and sandy mudstones with greyish-black lenses of conglomerates. Top is characterized by the dark yellow sandstones and gravels, which lower part is a set of light yellow coarse sandstones and sandy mudstones. It contains ostracod fossils, which are deposited in the river delta facies. Its thickness is in range of 1000~2850 m.

Ostrocoda: Candona (Pseudocandona) rostrata, C. (Lineocypris) asseptis, C. (Candona) neglecta，Subulacypris subtilis, Paracandona euplectella, Cyclocypris regularis, Cypridopsis vidua，Zonocypris membranae, Limnocythere lenuie, Eucypris inflate.

The ostracod fossils from the Kuche Fm are common in the Pliocene Dushanzi Fm of the Junngar Basin and in the Neogene Putaogou Fm in the Turpan Basin.

It is interpreted as a river delta depositional system or a curvilinear river depositional system developed on the floodplain.