Nanhuishan Fm
Type Locality and Naming
Type section Nanhuishan Formation is the No. XVI section in Kawabulak area, the upper portion of the same section with the underlying Huangshan Fm. It was measured between Huangshan and Huishan hills, about 2 km west of the Huangshan Hill, southwest of Kawabulak, Shanshan, Turpan, Xinjiang Uygur Autonomous Region (91°43'20”E, 41°24’50”N). In the type section, the formation is 317 m thick. The Nanhuishan Formation was first published by Cheng (1979). The name is derived from Huishan Hill in Kawabulak area, Shanshan City (county level), Turpan City, Xinjiang Uygur Autonomous Region. The name was originally appeared in a 1976 manuscript by the Compiling Group for Xinjiang Regional Stratigraphical Scale, which was published in 1981. Originally the unit was called Nanhuishan Group, and was lowered in rank as Nanhuishan Formation by Cai (1999). The formation spans the Cambrian-Ordovician boundary.
Synonym: （南灰山组）
Lithology and Thickness
The Nanhuishan Formation is basically a silicate sequence. It is dominated by greyish black and greyish brown chert, interbedded inhomogeneously with limestone and marlstone with banded chert at the base.
Relationships and Distribution
Lower contact
The Nanhuishan Fm is in conformable contact with the underlying Huangshan Gr. The lower boundary of the formation is defined by appearance of siliceous rock at its base, which lies on the brown sandstone of the Huangshan Fm.
Upper contact
The Nanhuishan Fm is in conformable contact with the overlying Xiabaishan Fm of Middle Ordovician. The upper boundary is defined by disappearance of siliceous rock and appearance of black marlstone at the base of the Xiabaishan Fm. However, regionally, there may be an intervening Xiangguletag Fm of early Ordovician.
Regional extent
The Nanhuishan Formation is exposed in southern Tianshan Area of Tarim Region, restricted to the area of Huangshan, southeast of Kawabulak, western Xinjiang. The thickness of the formation varies significantly, ranging from 30 to 948 m.
GeoJSON
Fossils
The middle part of the formation yields trilobites Hedinaspis sp., Lotagnostus sp., Procerotopyge sp., and Westergaardites sp. and brachiopod Acrothele sp.
Age
Depositional setting
Additional Information