Bukatuwei Fm

SW Tarim Basin. The Bukatuwei Fm was named by Ma Shipeng, Wang Yu zhen and others in 1991. The type locality is Xuxugou, upstream of Qipan River, southwest of Yecheng County, Xinjiang Weiwuerzhu Zizhiqu (Xinjiang Uygur Autonomous Region).

Synonym: （布卡吐维组）

The Bukatuwei Fm was subdivided into 4 lithological members, from bottom to top: (1) Variegated quartzose sandstone slate member of purple-brown of red-tone sandstone and quartz-rich sandstone, intercalated with minor black, yellow and grey slate, and with a argillo-arenaceous limonite in the base. The coarse quartzose sandstone contains pebbles and oblique bedding. In Xuxugou gully, it is about 25 m thick. (2) Variegated stromatolite carbonate rock intercalated with slate, sandstone and conglomerate. It is about 37 m thick in Xuxu-gou. The lower 17 m consists of grey-yellow carbonate rock yielding stromatolites. (3) Brown and rose thick-bedded stromatolitic dolomite, 69 m thick, composed completely of dolomite, except the lower 17 m which consists of interbedded grey-black carbonaceous slate and medium-thick-bedded stromatolitic dolomite. (4) Grey-black, grey-green basalt member, 83 m thick. Its lower part, 50 m thick in Xuxugou gully, is composed of basalt, bentonitized tuff and greyish chert. The upper part is composed of purple-red medium-thick-bedded iron-bearing and muddy dolomite with chert bands. Siderite and siltstone are occasionally seen in the top of the member. The Bukatuwei Fm varies greatly in thickness, at the north slope of west sector of Kunlun Mts., for example it is less than 1650 m thick near Kandilik, south of Yarkant River, west Qipanhe Township. However, it thins quickly to 87 m toward south, and 350 m thick in upstream of Qipanhe River.

Microplants in the second member include 13 genera and 19 species, the main elements are: Leiominuscula, Margominuscula, Trachysphaeridium, Leiopsophosphaera. The stromatolites occurring in this formation are Gruneria, Colonella, Tungussia and Aldania.

The paleomagnetic pole when the formation deposited was located at 41.3°N, 190.6°E.