Yuanbaoshan Fm
Type Locality and Naming
The name was proposed by the 2nd Party of Regional Geological Survey, Gansu Bureau of Geology in 1979 and published in Regional Geology of Inner Mongolia (in the series Geological Memoirs, Ministry of Geology and Mineral Resources) in 1991. The type section is located at Yuanbaoshan in western part of Erjin Banner, the Inner Mongol Zizhiqu.
Synonym: (圆包山组)
Lithology and Thickness
It is dominated by yellow green siltstone, intercalated with light gray, dark gray and grayish black silty shale, which yields rich graptolites, and with micritic sandstone and limestone lenses. There is also thin-bedded medium- to fine-grained arkosic quartzose sandstone in the upper part and pelitic slate with chert partings, which bears also graptolites.
Relationships and Distribution
Lower contact
The lower boundary of the formation is in fault contact with the underlying Xianshuihu Fm of the Middle Ordovician.
Upper contact
The upper boundary is conformably (?) overlain by the volcanic rock of the Gongpoquan Fm
Regional extent
The formation, approximately 1600 m in thickness, is exposed in the border area in northern part of Erjin Banner, and also in Alxa Left Banner.
GeoJSON
Fossils
The graptolites includes: Monograptus cf. pandus, M. priodon, Monoclimacis cf. griestoniensis, M. cf. gracilis, Pristiograptus , Climacograplus cf. scalaris, Streptograplus, and Monograptus sedgwickii at the base as well.
Age
Depositional setting
Additional Information