Xiangnan Fm
Type Locality and Naming
The type section of the Xiangnan Formation is the Xiangnan section at Xiangnanping. It lies about 12 km southeast of the Shuikou Town, the seat of Shuikou Township (111°03’E，24°59’N), and was measured by the Hunan Regional Survey Team in 1971. The Xiangnan Formation was first published by Zhang (1997). The name is derived from the Xiangnanping (Level Ground), Shuikou Township, southwestern Jianghua County, Hunan Province. The name was originally appeared in a 1988 manuscript by Luo Haiyan and Huang Weipei.
Synonym: （香楠组）
Lithology and Thickness
The Xiangnan Formation is mainly an epi-metamorphic clastic sequence, composed mainly of dark grey, thick-bedded sandstone, intercalated with greyish slate, which is dominated by carbonaceous slate. In the type section, the formation is 761 m thick, and the thickness of the formation in the exposed areas is about 547−761 m.
Relationships and Distribution
Lower contact
The Xiangnan Fm rests conformably on the Ediacaran Dingyaohe Fm that is consists of siliceous rocks.
Upper contact
The Xiangnan Fm is conformably overlain by the Chayuantou Fm. Because the Chayuantou Fm is also an epi-metamorphic clastic sequence, dominated by quartz sandstone and felsic sandstone, the boundary interval between the Xiangnan Fm and Chayuantou Fm is transitional in lithology. The intercalated beds of carbonaceous slate are largely reduced in the overlying Chayuantou Fm.
GeoJSON
Fossils
The fossils are rare in the Xiangnan Fm. Besides sponge spicule Protospongia sp., the formation yields also acritarchs, i.e., Brocholaminaria sp., Leiopsophosphaera sp., Lophominuscula sp., sp., Orygmatosphaeridium sp., Paleamorpha punctulata Xing & Liu, Quadratimorpha sp., Taeniatum crassum Xing & Liu, Trachysphaeridium sp., Trematosphaeridium holtedahlii Timofeev, Triangumorpha sp. etc.
Age
Depositional setting
Additional Information