Houjiashan Fm
Type Locality and Naming
Type section of Houjiashan Formation is the Houjiadashan section. It is located in Shanwang Township, Bagongshann, Nuainan, northern Jiangsu Province, lying about 4.7 km west of the Shanwang Town (116°46’08” E, 32°39’43”N). The type section was remeasured by the Anhui Regional GeologicalSurvey Team in 1979. In the type section the formation is 100.87 m thick. The Houjiashan Formation was named by Xu (1956). The name is derived from Houjiadashan Hill in Shanwang Township, Bagongshann District, Huainan City, northern Anhui Province. Originally, Xu (1956) called the formation Houjiashan Series. Subsequently Yang (1960) replace the series with Houjiashan Formation and restricted the formation to the Obollela-bearing low-middle part of the series, and assigned the upper part to Manto Fm.
Lithology and Thickness
The Houjiashan Fm is mainly a carbonate sequence. In the type section, the formation is divided into four beds, from bottom up: (1) greyish yellow, thick-bedded sandy limestone with grey phosphorite layer of 5 cm thick at the base (2.71 m); (2) light grey, greyish yellow, medium-bedded calcareous dolomite, alternated with purplish red, brick-red, thin-bedded dolomitic marlstone (72.82 m); (3) yellowish green silty shale and thin-bedded marlstone (18.42 m); (4) light greyish yellow, medium-bedded siliceous calcareous dolomite with siliceous lumps (6.92 m).
Relationships and Distribution
Lower contact
The Houjiashan Fm rests in disconformable contact on the Yutaishan Fm or Fengtai Fm of Cambrian System or the Sidingshan Fm of Ediacaran System. The lower boundary of the Houjiashan Fm is defined by the appearance of phosphorite (or phosphoric breccia) at the base of the formation.
Upper contact
It is overlain conformably by the Changping Fm. The upper boundary is defined by the disappearance of the dolomite at the top of the formation.
Regional extent
The Houjiashan Formation is exposed in the Xuzhou-Huaibei Area of North China Region, distributed in northern Anhui (Huaibei and Huainan cities and Huoqiu, Suxian, and Dingyuan counties) and northern Jiangsu (Tongshan and Jiawang counties). In Huainan and Huoqiu, the formation is dominated by phosphorite, phosphoritic breccia and sandy limestone, forming the phosphorite ore body. In Suxian and Jiawang counties, the lower part of the formation increases muddy contents, dominated by purple red, yellowish green and greyish yellow shale bearing rich micro-paleoplants.
GeoJSON
Fossils
Only brachiopod Obollela is collected from the basal part of the type section. In Fengyang and Huoqiu counties of north-central Anhui Province, the formation yields trilobites Redlichia and Estaingia and hyolithid Hyolithes. In northern Anhui and northern Jiangsu provinces, the shale interbeds in the lower part of the formation yield rich taxa of micro-paleoplants, including Archaeodiscina sp., Archaeofavosina sp., Asperatapsophosphaera umishanensis, Granomarginata prima, Hubeisphaera radiata, Laminarites sp., Leiofusa sp., Lophominuscula sp., Micrhystridiunm sp., Monotrematosphaeridium asperum, Paleamorpha figurata, P. punctulata, Polyedryxium sp., Pseudosonosphaera sp., Psophosphaera obscura, Taeniatum crassum, Taeniatum sp., Trachysphaeridium rude, T. hyalinun, T. simplex, T. cultun, Trachyrytidodiacrodium cf. verticale, and Triangumorpha tenera, etc.
Age
Depositional setting
The Houjiashan Formation represents phosphoric sediments in shallow sea.
Additional Information