The Study of Nanhua-Cambrian Systems and Their Sedimentary Environment Analysis in the Boundary Areas of Shaanxi, Henan and Hubei Provinces

According to the systematic investigation of the cross-sections in the boundary areas of Shaanxi, Henan and Hubei provinces, a new division of Nanhua-Cambrian is made on the previously measured sections in the area. It is suggested that the Liantuo formation of Nanhua era should exist in the district. The upper Cambrian should be restored as a formation name, and Shiwenzi formation should no longer represent both Wugongya formation in upper Cambrian and Shuihetian formation in lower Ordovician, due to the fact that the Shiwengzi formation in Zhashui area is merely magnesian carbonate deposits without fossils, located above the carbonaceous and silicious slate. According to the collected fossils and relics, the Cambrian can be clearly divided into lower, middle and upper (including Furongian) parts. The lithofacies palaeogeography features of each formation are systematically described, and provide significant foundation for regional strata division and provincial comparison.