Chishan Fm
Type Locality and Naming
Subei Basin. Liu Jichen and Zhao Rujun erected the Chishan bed in 1924. The locality for the designation is in Chishan of the Jurong County of Jiangsu and the reference section is in Chishan of Sancha 13 km southwest of the Jurong County, Jiangsu.
The Chishan bed erected by Liu Jichen and Zhao Rujun stands for the bright red massive sandstone that lies unconformably on the Pukou bed and under the Yuhuatai bed, which was attributed to Late Cretaceous. No section was measured when it was erected. In 1935 Li Yurao, Li Jie and Zhu Sen called it the Chishan Sandstone and assigned it to “Tertiary”. It was then renamed the Chishan Formation during the National Stratigraphic Conference held in 1959.
Lithology and Thickness
The Chishan Formation is represented by purple red, break red and gray green medium and thin-bedded calcareous and clayey feldspar quartz fine sandstone and siltstone interbedded with calcareous marl, intercalated with calcareous clayey shale, with the lower limit unclear. It is 694.77 m thick.
Relationships and Distribution
Lower contact
Conformably with the underlying Pukou Fm.
Upper contact
Its upper purple red and gray black mudstone contacts unconformably with the overlying Taizhou Fm conglomerate. In the type sections, it is overlain unconformably by the Quaternary.
Regional extent
The formation is widespread, ranging from Yutai, Huaian and Sheyang in the north, to Liyang, Yixing and Kunshan in the south; and from Jiangpu and Liuhe in the west to Dafeng in the east. In Fangshan of Jiangning of south Jiangsu, it is represented by break red fine sandstone, locally with gravels and silty shale, with a thickness exceeding 520 m. In Fenghuangshan of the Jiangning County, on the surface, the upper part of the formation is built up by break red and brown red siltstone and fine sandstone and mudstone; and the lower part brown red sandy conglomerate with greywacke conglomerate, with a total thickness of 215 m. In Lijiashan of the Maoshan area, it is built up by break red siltstone with thin-bedded mudstone and conglomerate lenses, of 38 m in thickness. Down the No.10 borehole south of Shetou of the Jintan City, it is represented by break red siltstone, mudstone and gray green silty mudstone, with a layer of purple red breccia at the base, measuring 270 m in thickness. On the surface in Niudushan of the Yixing City, it is represented by gray purple fine-grained lithic sandstone and break red feldspar lithic sandstone, bearing Dinosaurian eggs, 108 m in thickness. In Bochi of the Jiangyin County, the borehole No.110-1 can be considered as the representative of the formation where it is 369 m thick and contacts conformably with the underlying Pukou Formation, and its upper limit consisting of purple red and gray black mudstone contacts unconformably with the conglomerate of the overlying Taizhou Formation.
GeoJSON
Fossils
The formation yields Ostracods Cypridea sp. in Bochi of the Huaiyin County; Talicypridea sp., Cypridea cavernosa, Eucypris sp. in Shengli of Nanjing.
Age
Depositional setting
It is of piedmont and fluvial-lacustrine facies.
Additional Information