Zhuozishan Fm
Type Locality and Naming
The type section is in Yilehaituo Hill south of Lashizhong in Wuhai City, Inner Mongolia. The Zhuozishan Fm is derived from the Zhuozishan Limestone proposed by Guan Shicong and Che Shuzheng in 1955.
Synonym: (桌子山组）
Reference Section:
The reference section is in Dongshan in Laoshidan, Gangder Hill, Wuhai City (An et al., 1990).
Lithology and Thickness
The formation is composed dominantly of thick-bedded limestone with local argillaceous or siliceous nodules of epicontinental sea to enclosed basin. In the type area, the Zhuozishan Fm is 375 m thick.
Relationships and Distribution
Lower contact
It rests conformably on the dolomitic limestone intercalated with quartz sandstone of Sandaokan Fm
Upper contact
It is conformably overlain by the thin-bedded limestone and black calcareous mudstone at the base of the Kelimoli Fm
Regional extent
The Zhuozishan Fm has a persistent lithology and a thickness of 300-400 m, and is exposed in Zhuozi Hill, Gangder Hill, Qipanjing, Lasengmiao, Qianli Hill and Wuhu Hill in Wuhai City, Inner Mongolia. Moreover, drilling data show that at Hengshanbao in Lingwu County, Ningxia also exists the strata of the Zhuozishan Fm, with a thickness of 682.5 m (Ningxia Bureau of Geology and Mineral Resources, 1990).
GeoJSON
Fossils
Zhang Ridong (1959, 1960) established three cephalopod zones, in ascending order, Polydesmia zuezshanensis zone, Ordosoceras quasilineatum zone and Chisiloceras undulatum zone. Chen Junyuan et al. (1984) replaced Zhang's top zone with Pomphoceras-Dideroceras undulatum zone. Wang Zhihao and Luo Kunquan (1984) established two conodont zones, i.e. the lower Paroistodus originalis zone and the upper Amorphognathus variabilis zone, which were replaced by A. leptosomatus-L. clissectus zone and A. antivariabilis zone by An et al. (1990). Additionally, the Zhuozishan Fm also yields trilobites Pseudasaphus sp., Nileus cf. liangshanensis, Ovalocephalus (Hammatocnemis) primitivus, and is roughly equivalent to the I. gibberulus zone to D. (E.) hirundo zone in Britain. Zhang Ridong (1959) studied the cephalopods from the Zhuozishan Limestone. Mu Enzhi (1959) renamed it Zhuozishan Fm Zhang Wentang renamed it Zhuozishan Limestone Fm in 1962, and established the cephalopods Polydesmia-Ordosoceras zone.
Age
Depositional setting
Epicontinental sea to enclosed basin
Additional Information