Shuishi Fm
Type Locality and Naming
The type section of the Shuishi Formation is the Shuishi section, located at Shuishi Village, Chongyi, Jiangxi Province (114°16’E, 25°45’N). It is a northwestern extension of the Gaotan-Yangmeitang section (type section for underlying Gaotan Formation), lying about 11 km northwest of the seat of Chongyi County and was measured by Jiangxi Regional Geological Survey Team in 1966. The Shuishi Formation was first published by Compiling Group for Jiangxi Regional Stratigraphic Scale (1980). The name is derived from Shuishi Village in Guobu Township, Chongyi County, Ganzhou City, southwestern Jiangxi Province. It was originally appeared in a 1966 manuscript by Wei Xiuzhe from Jiangxi Regional Geological Survey Team. Originally the formation was called Shuishi Group, and was lowered in rank to Shuishi Formation in a 1988 manuscript by Liu Bangxiu from the Jiangxi Bureau of Geology and Mineral Resources. The formation name was finally published by Liu (1997)
Synonym:
Lithology and Thickness
The Shuishi Formation is a clastic sequence, consisting of blasto-arkosic-quartzose sandstone, blasto-arkosic greywacke, blasto-arkosic sandstone and blasto-graywacke, and greyish green slate and silty slate, intercalated with minor carbonaceous slate and tuffaceous slate. In general, the lower part of the formation is dominated by sandstone intercalated slate, and the upper part, with more muddy slate added, by slate intercalated sandstone. The entire formation is characterized by flysch rhythmicity formed by sandstone and slate. Usually the sandstone has size-grade and parallel bedding and the slate has horizon bedding. Occasionally there developed small oblique bedding in siltstone. In the type section, the formation is 2387.86 m thick.
Relationships and Distribution
Lower contact
The Shuishi Fm rests conformably on the underlying Gaotan Fm. The lower boundary of the formation is defined by the lithological change from the lenticular limestone or calcareous sandstone or striped calcareous slate of the Gaotan Fm to the thick- to mega-thick-bedded blasto-arkosic-quartzose sandstone at the base of Shuishi Fm.
Upper contact
It is conformably overlain by the graptolite-bearing Maoping Fm of Lower Ordovician Series. The upper boundary is marked by the appearance of greyish green, mega-thick-bedded slate at the base of Maoping Fm in southern Jiangxi Province or yellowish green quartzose sandstone of Jueshan Fm in southeastern Hunan Province.
Regional extent
The Shuishi Formation is exposed in the Cathaysia Area of South China Region, distributed in southwestern Jiangxi Province (Chongyi and Shangyou counties) and northern, western and central Guangdong Province (Deqing, Gaoyao, Kaiping, Longmen, Nanxion, Qujiang, Taishan and Yunan counties). The formation is stable in lithology and is usually 2100 to 2400 m thick but the thickness varies from 900 to 3200 m.
GeoJSON
Fossils
The Shuishi Formation yields brachiopods Acrothele recta, Homotreta pileata, H. lisani, H. orientalis, Lingulella manchuriensis, L. liui, L. maricia, Obolus luanhsuensis, O. minimus, O. cf. taianensis, and Paterina sp. and sponge spicule Protospongia sp.
Age
Depositional setting
Based on the formation’s composition and sedimentary features, it principally belongs to deposits of peri-continental sea-basin setting. However the upmost deposits of the formation are dominated by argillaceous rocks intercalated with limestone, indicating a change of the sedimentary environment into shallow-water basin during the terminal stage of deposition.
Additional Information