Linkuanggou Fm

The type section of Linkuanggou Formation is located at Linkuanggou (Guozigou) gully, southwest of the Kensay Mountain Pass (older highway), Houcheng, Ili, Xinjiang Uygur Autonomous Region (81°10’06” E, 44°28’24” N). The section lies about 52 km northeast of the seat of Huocheng County, Xinjiang Uygur Autonomous Region and was measured by Joint Team of the Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences, Xinjiang Institute of Geology and the Regional Geological Survey Team of Xinjiang Uygur Autonomous Region in 1977. The Linkuanggou Formation was first published by Cheng (1979). The name is derived from Linkuanggou, a gully with phosphorite in Houcheng County, Ili Kazak Autonomous Prefecture, Xinjiang Uygur Autonomous Region. The name was originally appeared a 1977 manuscript by the Joint Team of Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences and Xinjiang Institute of Geology, and Regional Geological Survey of Xinjiang Uygur Autonomous Region.

Synonym: （磷矿沟组）; Based on the biostratigraphic contents, Wang and Cheng (1985) named the upper part of the Linkuanggou Formation as Huocheng Fm, which is a form of lithostratigraphic unit with biostratigraphic meaning. To return to property of lithological unit, Cai (1999) merged back the Huocheng Fm into Linkuanggou Formation.

The Linkuanggou Formation is a phosphoric clastic and carbonate sequence. Lower part of the formation consists of dark grey, phosphoric siliceous and carbonaceous sandstone, siltstone, shale, and limestone, nodular limestone, alternated in non-uniform thickness. Usually a layer, 0.5 m thick, of black and dark grey phosphoric conglomerate occurs at the base of the formation. Upper part of the formation consists of grey, thick-bedded bioclastic limestone.

The lower part of the Linkuanggou Formation yields incomplete trilobite cranidia of Redlichia, algae and small shelly fossils (mainly sponge spicule Protospongia). The upper part yields trilobites Calodiscus spp., Dinesus cf. granuosa, Kootenia spp., Pagetides sp. and Tannudiscus sp.