Huayenssu Fm
Type Locality and Naming
The type section of Huayenssu Formation is the Tianmashan section, located at Tianmashan Hill, 0.22 km southwest of Changshan Town, the seat of Changshan County, Zhejiang Province (118°29’E, 28°52’N). The section was measured by Lu et al. in 1954 (Lu et al., 1955). In the type section, the formation does not completely expose, but in other sections nearby the Changshan Town, the totally exposed formation has a thickness of 110.10 m. The Huayenssu Formation was named by Lu et al. (1955). The name is derived from Huayenssu (spelled Huayansi in Hanyu Pinyin) Temple, built on the east slope of Tianmashan Hill, Changshan County, Quzhou Prefectural City, Zhejiang Province. Originally it was called Huayenssu Limestone by Lu et al. (1955), and was renamed Huayenssu Formation by Lu et al. (1963).
Synonym: （华严寺组）
Lithology and Thickness
The Huayenssu Formation is a carbonate sequence, consisting mainly of grayish black, thin- to medium-bedded striped limestone with interbeds of thin-bedded argillaceous limestone, calcareous mudstone, shale and brecciated limestone. The limestone is characterized by development of lamination and argillaceous bands.
Relationships and Distribution
Lower contact
The Huayenssu Fm is in conformable contact with underlying Yangliugang Fm. As the Huayenssu Formation and its underlying formation are all carbonate sequences, the lower boundary of the formation is defined only by minor lithological differences. No lower boundary of the formation is exposed in the type section (Lu and Lin, 1989), and other sections nearby show that there is no clear lithologic boundary between the Huayenssu Formation and Yangliugang Formation, and the boundary between these two formations is usually placed by the change from thin-bedded laminated and dolomitic argillaceous limestone bearing limestone lenses to thin-bedded striped limestone.
Upper contact
The Huayenssu Fm is in conformable contact with overlying Siyangshan Fm. As the Huayenssu Formation and its overlying formation are all carbonate sequences, the upper boundary of the formation is defined only by minor lithological differences. The upper boundary of Huayenssu Formation is placed by the change from thin-bedded striped limestone to the podiform argillaceous limestone of Siyangshan Formation.
Regional extent
The Huayenssu Formation is exposed in the Jiangnan Slope Area of South China Region, including western and northwestern Zhejiang Province (Jiangshan, Changshan, Tonglu, Fuyang, Kaihua, Changhua, and Anji counties); northern Jiangxi (Wuning County) and southeastern Anhui Province (Ningguo, Jixi, Shitai, Xiuning, and Yixian counties). The formation is mostly stable in lithology and increases thickness northwestward, ranging 99.2 to 213 m thick.
GeoJSON
Fossils
The Huayenssu Formation is well fossiliferous with trilobites, especially with agnostoid trilobites. In the type section the formation yields rich trilobites (Lu and Lin, 1989), including Agnostotes clavatus, Ammagnostus sp., Aspidagnostus chekiangensis, A. pentagonus, A. sp., Clavagnostus subconicus, C. sp., Glyptagnostus reticulatus, G. stolidotus, Goniagnotus nodibundus, Kormagnostus？sp., Lejopyge sinensis, Peratagnostus zhejiangensis, Proceratopyge distensa, Pseudagnostus communis, P. transversus, P. sp., Tomagnostella tianmashanensis, and T.？invalida. In other localities, the formation yields additional trilobites, Agnostus inexpectans, Ajrikina fengzuensis, A. fuyangensis, Ammagnostus duibianensis, A. yaogongbuensis, A. pentagonus, A. cf. stictus, Buttsia globosa, Eolotagnostus duibianensis, Erixanium rectangularis, Homagnortus sp., Irvingella angustilimbata, I. major, Kormagnostus？clavatus, Linguagnostus？sp., Oidalegnostus tienshanicus, Malladiodella spp., Palaeadotes hunanensis, Paradamesella paratypica, Peratagnostus distinctus, Proceratopyge conifrons, P. fenghwangensis, P. fuyangensis, P. mirabilis, P. zhejiangensis, Pseudagnostus dubius, P. idalis, P. vigilax, P. cf. bulgosus, P. cf. cyclopyge, P. cf. mestus, Sinoproceratopyge distincta, S. kiangshanensis, S. sinuata, Teinistion sp., and Tomagnostella spp.
Age
Depositional setting
Additional Information