Shaiwa Gr
Type Locality and Naming
The type section is located at Shaiwa Village 5 km to the northeast of the Sidazhai Country, Houchang Region, Ziyun County, Guizhou Province. It was named by the Regional Geological Reconnaissance Party of Guizhou Province in 1981.
Lithology and Thickness
Claystone and Chert. The particular group comprises the Baxian Fm and Linghao Fm. In the Shaiwa section the lower member of the Baxian Fm is known as the Siliceous Rock Member with it basal part is composed of dark-grey thin-bedded siliceous rocks, intercalated with shale, and is 275-m thick, while the upper member is known as the Sandstone Member, and is commonly 200-400-m thick. The lower member of the Linghao Fm is known as the Clayrock Member, with a thickness of about 100 m, while the upper member of the formation concerned is known as the Breccia Member, with its top part consisting of siliceous rocks intercalated with shale, and with a thickness of 150-200 m.
Relationships and Distribution
Lower contact
Conformable contact with the underlying Sidazhai Fm
Upper contact
Conformable contact with the overlying Luolou Fm
Regional extent
On the northern side of the Yunnan-Guizhou-Guangxi Basin the particular group in its extension from Shaiwa area northward to Baxian and Douluo areas of Zhenning County, Guizhou Province with the decrease in the amount of carbonate and clastic rocks, the thickness of the group has been enlarged remarkably, with its maximum thickness reaching as many as 1650 m; still further north it is composed mainly of claystones and thin-bedded micrite, with its thickness being reduced sharply to be of 300-400 m, and it is overlying directly the Houziguan Limestone. Till the margin of the Basin in the Ceheng, Wangmo and Luodian areas, the facies changes into the Wujiaping Fm (Wuchiaping Fm), Southward, except for the Nashui area of Luodian County where in its lower part there are still developed carbonate and clastic rocks, in most parts of the region the lithological subdivision of the four members is not distinct, and the whole group is composed completely of thick-bedded positively graded lithoclastic sandstone, siltstone, claystones and siliceous rocks. On both sides of the Basin in the Nasuo of Guangnan-Lide of the Funing County in Yunnan Province, the Shaiwa Gr is in a disconformable contact with the underlying Emeishan Basalt Fm, and is composed of grey-green silty siltstone and clayey rock, intercalated with tuffaceous siltstone and limestone and is distributed in the form of a narrow belt, with a total thickness of 40-127 m.
GeoJSON
Fossils
Baxian Fm yields Fusulinida represented by Codonofusiella sp., etc.; while the upper part of the Linghao Fm yields Palaeofusulina sp., which are belonging respectively to the Wuchiapingian and the Changhsingian Stages of the Lopingian Epoch.
Age
Depositional setting
Additional Information