Zhaertaishan Gr

Southeast-central Inner Mongolia (north of Yellow River loop). The Zhartaishan Gr was named by the No. 1 Party of Regional Geological Survey, Inner Mongolia Bureau of Geology in 1972. The naming locality is the Zhartai Mt. area in the juncture between Urad Qianqi and Urad Zhongqi, Bayannur Meng, Inner Mongolia.

Synonym: （渣尔泰山群）

The Zhartaishan Gr is a set of continental to neritic sediments which experienced greenschist facies (temperature and pressure) metamorphism and multiple stages of tectonic deformations. It is a set of clastic rock, shale and carbonate rock, which changes upward to fine-grained and then coarse grained. In Zhartai Mountain area, the formation is over 3000 m thick. At present, Zhartaishan Group is subdivided into four formations:

Liuhongwan Fm (uppermost formation) was established in Liuhongwan and Shilongwan District, Xiaoshetai Township, Urad Qianqi. The main rock is composed of medium- to thin-bedded light-colored fine-grained quartzite with gravel-bearing quartzite, feldspar quartzite of littoral facies. The thickness is recorded as about 300 m to 500 m. It conformably contacts with underlying Agulugou Fm. No direct overlying strata onto the formation has been seen, except for Quaternary cover.

Agulugou Fm: The type locality is the northwest periphery of Zhartai Moutain, and the naming section is the beds from No. 1 to No. 19 beds of Shujigou section. The main rocks are all carbonaceous. Lower part is composed of dark grey slate. Middle part is grey and dark grey microcrystalline limestone sandwiched with slate and muddy dolomite. Upper part is dark-grey slate accompanied with sandy crystalline limestone. The formation is 1520 m thick. It conformably overlies the underlying Zenglongchang Fm.

Zenglongchang Fm: The naming section is around Zenglongchang, Urad Qianqi. Lower part is fine feldspar-quartz sandstone and grey silty slate of coastal facies. Middle part is carbonaceous, muddy slate. sandy microcrystal-line limestone. Upper part is dolomitic limestone and siliceous-banded crystalline limestone of stromatolite- bearing carbonate platform facies. It contacts conformably onto the underlying Shujigou Fm.

Shujigou Fm (lowermost formation): The naming section is located in Shujigou, Xiaoshetai Township, Urad Qianqi. The formation is mainly composed of grey, grey-white medium- to thick-bedded sandy conglomerate, sandstone, quartzite siltstone and slate; the middle part is intercalated with meta-basalt, andesite, about 1000 m thick. It unconformably covers on Neo-Archean strata.

The stromatolites in the Zenglongchang Fm are Gruneria f., Omachtenia f., Eucapsiphora f., Xiayingella f., Scopulimorpha f., Kussiella f., Conophyton ocularaideum. The microplants: Trematosphaeridium holtedahlii. Stromatolites in upper part of the Agulugou Fm are Conophyton f., Conistratifera f., Scopulimorpha f. The carbonaceous slate in the Agulugou Fm has microplants such as Quadratimorpha simplicis, Stictosphaeridium formosum, Pseudozonosphaera sinica, Asperatopsophosphaera umishannensis (Sun Shufen, 1995).

Currently, despite past attempts, there is not yet an undoubtedly approved isotopic geological age for the Zhartaishan Gr. Therefore, it is only roughly attributed to Paleo-Mesoproterozoic. For this reason, the "formation" level stratigraphic units included in the group cannot be cited separately as entries, and are described here together under the group.