Kurkak Fm

Tieklik region (SW Tarim Basin). The Kurkak Fm was named by Ma Shipeng et al. in 1980 and formally published on the Geology of Xingjiang in 1980 by Fang Xilian. The typical section is situated in Qiakmaklik valley (for the lower part) and Kzisuhumu valley (for the upper part) in the north slope of Kunlun Mountain in Yexian County, Xinjiang Weiwuerzhu Zizhiqu (Xinjiang Uygur Autonomous Region).

Synonym: （库尔卡克组）

The Kurkak Fm is dominated by clastic rock, including dark gray or gray siltstone, silty shale and shale interbedded with sandstone, sandy conglomerate and olistostromes. Lower part is dark gray, interbedded with grayish purple, pelitic ferruginous siltstone intercalated with lamellar dolomite, and the basal part is a bed of dolomite as a good index bed bounded by the underlying strata. Upper part is occasionally interbedded with thin bandings of phosphorite. As the outcrop is incomplete, the lower part is represented by the sequence (1-4 members) exposed in the Qiakmaklik valley and Klixi valley, and the upper part is represented by that exposed in Kzisuhumu valley (5-6 members). The thickest exposure is 674 m along the Xinjiang-Tibet Road, but going westward to Tufuluk valley the thickness is 100 m and to Jigeyuenir valley, only about 50 m.

The Kurkak Formation yields microplants (49 genera and 91 species) dominated by Archaeohystrichosphaeridium sp., Asperatopsophosphaera sp., Macroptycha sp., Micrhystridium sp., Monotrematosphaeridium sp., Pseudozonosphaera sp., Orygmatosphaeridium sp., Nucellosphaeridium sp., Baltisphaeridium sp., Dictyosphaera sp., Leiopsophosphaera sp., Leiominuscula sp., Protoleiosphaeridium sp., Trachysphaeridium sp., Quadratimorpha sp., Polyporata sp. etc.