Xiaoneichong Fm
Type Locality and Naming
The type section is the Tanchong-Peidi-Luoshikou (Xiaoneichong) section, lying about 8.5 km west southwest of Daning Town, Hezhou City (111°45’E, 24°25’N) and was measured by Guangxi Regional Geological Reconnaissance Team in 1965. The Xiaoneichong Formation was first published by Guangxi Bureau of Geology and Mineral Resources (1985). The name is derived from Xiaoneichong Village in Daning Township, Babu District, Hezhou City, Guangxi Zhuang Autonomous Region. It was originally appeared in a 1976 manuscript by the Guangxi Regional Geological Survey Team.
Synonym: （小内冲组）
Lithology and Thickness
The Xiaoneichong Formation is a clastic sequence. It consists of yellowish green and greyish green, massive sandstone, feldspathic quartzose sandstone, quartzose sandstone, and hetero-granular sandstone, alternated with sandy shale, siltstone, and carbonaceous mudstone and intercalated with a layer of phosphoric nodules-bearing carbonaceous shale and yellowish green sandy shale, 7 m thick, near its base. In the type section, the formation is 1413.00 m thick.
Relationships and Distribution
Lower contact
The Xiaoneichong Fm is in conformable contact with the underlying Peidi Fm. The lower boundary of the Xiaoneichong Fm is defined by the disappearance of siliceous rock of the Peidi Fm and the appearance of sandy shale at its base.
Upper contact
The Xiaoneichong Fm is in conformable contact with the overlying Huangdongkou Fm. The upper boundary is defined by lithological change from sandy shale to the gravel-bearing coarse-grained sandstone at the base of Huangdongkou Fm.
Regional extent
The Xiaoneichong Formation is exposed in the Cathaysia Area of South China Region, distributed in southern and eastern Guangxi Zhuang Autonomous Region (Daxin County of Chongzuo City, Yongning District of Nanning City, Cangwu and Tengxian counties of Wuzhou City, Qingtang District and Guiping County of Guigang City, Zhaoping County and Babu District of Hezhou City). The thickness of the formation ranges from 319 to 1780 m.
GeoJSON
Fossils
In the type section, the Xiaoneichong Formation yields common sponge-spicules Protospongia sp. In other localities, the formation yields micro-paleoplant fossils Acanthotriletes sp., Conglobulosphaera incrustus, Lophotriletes sp., Trachyotrites sp., and Tyloligotriletes induratus etc.
Age
Depositional setting
Additional Information