Huangdongkou Fm
Type Locality and Naming
The type section is Tanchong-Peidi-Luoshikou (Huangdong) section, lying, about 8.5 km west of Daning Town, Babu District, Hezhou City, Guangxi Zhuang Autonomous Region (111°41’E, 24°25’N) and was measured by the Guangxi Regional Geological Exploration Team in 1965. Huangdongkou Formation was first published by Guangxi Bureau of Geology and Mineral Resources (1985). The name is derived from Huangdong 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: （黄洞口组）
Lithology and Thickness
The Huangdongkou Formation is a set of clastic sequence (flysch), dominated by greyish green and yellowish green, hetero-granular quartzose sandstone, feldspathic quartzose sandstone and siltstone, intercalated with shale, minor carbonaceous shale and lenticular limestone and with fine gravel-bearing coarse- and fine-grained sandstone at the basal part. In the type section, the exposed Huangdongkou Formation is 1971 m thick.
Relationships and Distribution
Lower contact
The Huangdongkou Fm rests conformably on Xiaoneichong Fm. The lower boundary of the Huangdongkou Fm is marked by lithological change from silty shale of the underlying Xiaoneichong Fm to the gravel-bearing coarse-grained sandstone at the base of the Huangdongkou Fm.
Upper contact
Its upper boundary is unknown in the type section as the top part of the formation is not exposed. However, other sections show the formation is conformably overlain by the Liuchen Fm of Ordovician System. The upper boundary of the formation is marked by the appearance of the graptolite-bearing shale of the overlying Liuchen Fm.
Regional extent
The Huangdongkou Formation is exposed in 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, Jinxiu Yao Autonomous County of Laibin City, Menshan, Cangwu and Tengxian counties of Wuzhou City, Qingtang and Gangbei districts and Guiping County of Guigang City, Zhaoping County and Babu District of Hezhou City). The thickness of the formation ranges from 453 to 3654 m.
GeoJSON
Fossils
In the type section, the Huangdongkou Formation yields common sponge-spicules Protospongia sp. In other localities, the formation yields additional fossils, including trilobites Charchaqia sp., Hedinaspis sp., and Lotagnostus sp. etc., brachiopods Acrothele sp., A. aff. cheni, Homotreta sp., Lingulella sp., Obolus sp., O. aff. shansiensis, and Paterina sp., etc., and micro-paleoplant fossils Asperatopsophosphaera sp., Leiofusa sp., Leiopsophosphaera spp., Lophosphaeridium sp., Micrhystridium sp., Polyedryxium sp., Trachysphaeridium spp., and Trematosphaeridium sp. etc.
Age
Depositional setting
Additional Information