Sixiakou Fm
Type Locality and Naming
The type section is located at Sixiakou, 80 km northwest of Yunxi, Hubei. It was named by the Shaanxi Party of Regional Geological Survey in 1966.
Lithology and Thickness
Sandstone, Claystone and Limestone. Composed of two suites of limestone containing chert nodules and bands and a suite of clastic rocks. Lower part consists of black-gray shale intercalated with quartz sandstone, conglomerate and multi-layered micritic limestone. Upper part is of gray-black clayey shale interbedded with siltstone. Thickness 913−1077 m. Regionally, limestone increases in the west and clastic rock increases in the east. In the Xikou area of Zhen’an, mudstone and shale are well developed, containing rich fossil plants.
Relationships and Distribution
Lower contact
Conformable contact with the underlying Yuanjiagou Fm (upper Devonian)
Upper contact
Conformable contact with the overlying Xiaoyaozi Fm
Regional extent
The formation is distributed from Xikou to Xunyang of Zhen’an, Shaanxi and Yunxi of Hubei, and may extend westward to southern Huixian County of Gansu. Coeval with the Fanjiaping Fm (same column 44).
GeoJSON
Fossils
Lower part contain Plants Cardiopteridium spetsbergense, Neuropteris gigantea; brachiopods Striatifera striata, Gigantoproductus sp., Phricodothyris asiatica, etc.; Corals Diphyphyllum gracilis, Dibunophyllum cf. multiseptatum, Koninckophyllum cf. irregulare, Lithostrotion cf. sunanense, etc. Upper part contain Plants Neuropteris gigantea, N. kaipingiana, Rhodea parasparsa, Sphenopteris sp., Linopteris sp., etc.
Age
Depositional setting
It is interpreted as neritic lagoon deposits
Additional Information