Yunmengshan Fm
Type Locality and Naming
West Henan. The Yunmengshan Fm was named by Han Yingshan, Li Shengsi, Yan Lianquan in 1952. The naming section is at Sigou, Shimengen-Baitanggen, Ruyang County, Henan Province. It is the lower formation of the Ruyang Gr.
Synonym: （云梦山组）
Lithology and Thickness
The Yunmengshan Fm is composed of purple-red, grey-purple in-equigranular quartz sandstone, intercalated with shale. The base consists of conglomerate sandwiched with iron ore. The sandstone bears cross-bedding and tabular oblique bedding, and the ripple marks can be seen on the bedding surfaces. The Yunmengshan Fm is 276 m thick.
Relationships and Distribution
Lower contact
The basal conglomerate covers disconformably the underlying Bingmagou Fm (in Songshan Mt., Wangwu Mt. area). But in most of the distribution area, the formation overlaps unconformably onto the underlying volcanics of the Xiong'er Gr or onto the Dengfeng Gr.
Upper contact
The upper surface of the quartzite is taken as the upper boundary of the formation, which is conformably overlain by the Baicaoping Fm (middle formation of the Ruyang Gr).
Regional extent
West Henan. The formation is distributed mainly in western Henan and Taihang Mts. The thickness varies greatly: 93-293 m in Jiyuan, 826 m in Mianchi, 108 m in Songshan Mt. and 225-408 m around Wuyang-Xiping.
GeoJSON
Fossils
It bears small amounts of microplants: Trematosphaeridium minutum, T. holtedahlii.
Age
Depositional setting
Additional Information