Chushatung Fm
Type Locality and Naming
The type locality is around the Zhushadong Village, but no type section was assigned when the formation was erected by Zhang (1952). An auxiliary section, the Yaomeng section (113°15’ E, 33°44’N), was proposed to be representative of the formation by Pei et al. in Xi and Pei (1997). The section is located at Yaomeng Village in Zhanhe District, Pingdingshan City and was measured by Deng Xiaode from China University of Geosiences (Wuhan) in 1989. The section lies about 5 km southeast of Zhushadong Village or 6.5 km southeast of Pindingshan City. In this section the formation is 63.5 m thick. The Chushatung Formation was named by Zhang (1952). The name is derived from Chushatung (spelled Zhushadong in Hanyu Pinyin) Village, Xinhua District, southwest of Pindingshan City, central Henan Province. Originally Feng and Zhang (1952) called the unit Chushatung Limestone Series, and subsequently it was renamed as Chushatung Formation in a 1962 manuscript by the Henan Institute of Geology with excluding the phosphate-bearing sandstone at the basal part of the Chushatung Limestone Series. The phosphate-bearing sandstone was named by the institute as a new formation, the Xinji Phosphate-bearing Formation, which was subsequently called Xinji Formation by Henan Regional Geological Survey Team (1964). The reduced Chushatung Formation was formally published later by Zhang Z et al., (1994) and is followed herewith.
Synonym: （朱砂洞组）
Lithology and Thickness
The Chushatung Formation is the first Cambrian carbonate sequence in North China platform and can be roughly divided into two parts. Lower part consists of micritic limestone, striped marlstone, laminated crystalline limestone, stromatolitic algal limestone, pink cherty micritic limestone, reddish grey dolomitic limestone and evaporite-solution breccia (ca. 25 m). Upper part mainly consists of grey and pink medium-bedded dolomitic limestone with a few of interbeds of sandy oolitic limestone and algal-coating limestone (ca. 38 m). The thickness of the formation varies between 20 and 94 m with a deceasing tendency northward.
Relationships and Distribution
Lower contact
The Chushatung Fm rests conformably on the underlying phosphoric sandstone, or on the sandy limestone of Xinji Fm in central Henan Province or on the sandstone of Liguan Fm in northwestern Shandong Province.
Upper contact
It is conformably overlain by the fine clastic Manto Fm.
Regional extent
The Chushatung Formation is exposed in the Shanxi-Henan-Shaanxi, and the Western Shandong areas of North China Region, distributed in central Henan Province (Dengfeng, Lushan, Yexian and Baofeng counties), south-central Shaanxi Province (Longxian, Qishan and Luonan counties), and western Shandong Province (Changqing, Feixian, Linqu, and Yishui counties). In Lushan County of central Henan, large-scaled commercial gypsum deposits are developed in this formation. The gypsum horizons are also known in Baofeng and Yexian counties. In Luonan of Shaanxi Province, the formation consists of purplish red, light grey thick-bedded dolomitic breccia, dolomitic limestone, dolomite, which contain cherty nodules or cherty bands with mud cracks, cross-bedding and halite pseudocrystals. Limited outcrops of the formation are observed in southern Shanxi Province, merely confined in the area of Ruicheng County in Zhongtiaoshan Mountain, where the formation increases dolomitic content and is dominated by dolomite, argillaceous dolomite and dolomitic limestone containing cherty nodules.
GeoJSON
Fossils
Chushatung Formation is scarce in fossil. Only in some places of Dengfeng City, north-central Henan, trilobites Redlichia noetlingi and R. sinensis were collected from the formation.
Age
Depositional setting
The formation is deposited in tidal-flat and subtidal gentle slope sedimentation.
Additional Information