Biyunshan Fm
(29), lower to middle Kungurian Stage (late Cisuralian Epoch; late-Early Permian)
Type Locality and Naming
The type section is located at Harxiaklike to the east of the Kalwa County, Xinjiang. It was named by the 1st Regional Geological Reconnaissance Expedition under the Xinjiang Geological Bureau in 1981.
Lithology and Thickness
Clastics: Grey and light-grey coarse-grained calcareous and medium-grained calcareous feldspar-lithoclast sandstones, intercalated with black limestone and carbonaceous siltstone, containing a small amount of conglomerate. Thickness is 718 m (type section; but see regional extent).
Relationships and Distribution
Lower contact
Unknown; no base of the formation has been found. Regionally, disconformity onto Karamiran Gr of latest Carboniferous-earliest Permian
Upper contact
Unknown contact relationship with the overlying strata. Regionally, disconformity to the mid-Permian Karwa Fm.
Regional extent
This formation has a thickness of over 2148 m at Qieditage in the northern belt; with its lower part gradating into limestone through facies change westerly at a point of 15 km. To the south of the Aqikele Lake, the thickness of the formation reaches as great as over 900 m, and being of 2880 m till the Biyun Mt. The formation is distributed in the form of a NW-SE-trending belt in the area from the middle reaches of the Kalamilan River to the Aqiang area. And the southern belt extends from the Muzitag to the Amapaxia area to enter the territory of Tibet, and is distributed in a nearly East-West-trending belt with its scattered exposures in the Liushitag area
GeoJSON
Fossils
Fusulinida such as Misellina claudiae, M. ovalis, Brevaxina sp., Staffella sphaerica; Corals such as Chaetetes sp., Protomichelinia sp., Szechuanophyllum sp.; and Brachiopods such as Neospirifer orientalis. In the southeastern part of the Biyun Mt. it yields such Fusulinida as Parafusulina sp., Corals as represented by Paracaninia sp., and Brachiopods as represented by Marginifera sp. and Choristites sp.
Age
Depositional setting
It is interpreted as deep-water turbidites.
Additional Information