Sanshui Fm
Type Locality and Naming
The Sanshui Formation was erected by Zhang Xianqiu in 1973. The section for the designation is down the well No.7 in Baoyue at the mouth of the Sanshui river of Guangdong.
Lithology and Thickness
The Sanshui Formation is represented by purple red siltstone, fine sandstone with sandy conglomerate and dark gray and gray green mudstone and marl with massive gypsum. It is 575.5 m thick.
Relationships and Distribution
Lower contact
Its base is an unconformable contact marked by gray purple and dark purple siltstone with sandy conglomerate is distinguished from the Baihedong Fm marked by dark gray and gray green mudstone and marl.
Upper contact
Its top is a conformable contact bounded by grayish purple and dark purple red sandy conglomerate with silty mudstone appearing at the base of the Dalangshan Fm.
Regional extent
The formation mainly occurs in Gaoyao-Sanshui-Guangzhou and Xinhui-Shunde of central Guangdong. In the Baoyue area of the Sanshui basin, the lower member of the formation is dominated by fluvial-alluvial sediments, with a thickness of 258 m. In the Guangzhou area, it is dominated by diluvial macroclastic rocks, with a thickness of 300 m. In Nanhai-Shunde, it becomes coarser in grain size, and is 83 m thick. The upper part of the formation is dominated by shallow lacustrine sediments consisting of purple red marl and gray marl with gypsum lumps, ranging from 143 to 442 m in thickness, at maximum in the Baoyue area. It shows disconformable contact or an angular discordance with the underlying strata and a conformable contact with the overlying strata.
GeoJSON
Fossils
The formation yields ostracods Cypridea cavernosa, C. recta, C. gigantea, C. subtera, Talicypridea amoena, T. obesa, Cyclocypris minuta, Candona declivis, Eucypris vulgaris, Paracandona hunanensis, Cyprois guangchouensis, Charophytes Glbichara nigra, Sphaerochara paravula, Euaclistochara indistincta, E. deserta, Obtusochara culmina.
Age
Depositional setting
It belongs to fluvial-lacustrine deposition.
Additional Information