Shangshuangjiaoshan Gr
Type Locality and Naming
Northwesternmost Jiangxi. The Shangshuangjiaoshan Gr was named by the Jiangxi Party of Regional Geological Survey in 1974 (Guidebook of 1: 500 000 Scale Geological Map of Jiangxi Province). The typical section is situated in the core and two limbs of Jiuling anticline (including Xiushui, Wuning, Tonggu, Ruichang and De'an counties) in northwest Jiangxi Province.
Synonym: （上双桥山群） , Shangshuangjiaoshan Fm
Lithology and Thickness
Lower part is dominated by tuffaceous slate, silty slate and chlorite sericite schist (greenish gray to dark gray), intercalated with metamorphic fine tuffite, meta-quartz keratophyre and blasto-tuffaceous siltstone, with basal conglomerate (in Xiushui area). Upper part is thin- to medium-bedded tuffaceous slate (bluish gray to black) intercalated with medium-bedded metamorphic silty tuffite and meta-tuffaceous siltstone, with blasto-diamictite at the base and the occurrence of Bouma sequence upward.
Relationships and Distribution
Lower contact
The Shangshuangjiaoshan Gr unconformably overlies the underlying Xiashuangjiaoshan Gr [Not in current Lexicon?] [Regionally in NW Jiangxi, the next older unit may be the Yifeng Fm?]
Upper contact
It is unconformably overlain by the Dongmen Fm (conglomerate of basal Nanhuan)
Regional Extent:
Northwest Jiangxi Province
Regional extent
Northwesternmost Jiangxi.
GeoJSON
Fossils
The Shangshuangjiaoshan Gr yields abundant microplants Leiopsophosphaera infriata, Leiominuscula minuta. Zonosphaeridium minutum, Trachysphaeridium hyalinum T· rugosum, Lophosphaeridium rugosum, Dictyosphaera sinica, Margominuscula rugosa, Zonosphaeridium sp., Pseudozonosphaera sinica, Laminarites sp. etc.
Age
Depositional setting
Additional Information