Yesanggang Fm
Type Locality and Naming
The type section is located in the Gudaqia-Yesanggang region of Qiemo County, Xinjiang. It was named by the Regional Geological Survey Party under the Xinjiang Bureau of Geology and Mineral Resources in 1974, and was cited officially by the Compiling Group for the Regional Stratigraphic Chart of the Xinjiang Uygur Autonomous Region.
Lithology and Thickness
Sandstone-siltstone with minor limestone. Lower part is composed of purplish-red thick-bedded sandstone and siltstone. Upper part is composed of unequal interbeds of medium-bedded and medium- and fine-grained calcareous sandstone, light-grey-green thick-bedded tuffaceous sandstone together with grey-white and grey-black and thick-bedded limestones. Along the strike of the strata, the facies of its Lower part changes into a complex of siltstone, siltstone, or tuff, andesitic porphyrite, intercalated with several layers of gypsum, with its basal part being cut by a fault, with a thickness of less than 2000 m.
Relationships and Distribution
Lower contact
Disconformity onto Karamiran Gr of latest Carboniferous-earliest Permian
Upper contact
Not known
Regional extent
Formation occurs in the Kepa to Aqiang, the Gudaqia and Yesanggang areas on the northern slope of the Kunlun Mts. in the northern belt, and in the area of the middle reaches of the Karamilan River in the southern belt. The lithology of the formation is a bit changeable, which lies in its being composed largely of thick-bedded calcareous sandstone and greywacke, intercalated unequally with the massive limestone, with the volcanic rocks occurring under the limestone while their extending westerly to the middle and upper reaches of the Molika River. Uppermost part is coeval with Karwa Fm; lowermost part is coeval with the
GeoJSON
Fossils
In the Gudaqia area of the northern belt the Yesanggang Fm yields Fusulinids represented by Eopolydiexodina sp.; brachiopods such as Dictyoclostus graclosus, Marginifera ornuta, M. cf. lasallenois, Juresania aff. nehroscensis, Martinia semiglobosa, Camerophoria cf. superstes, Dielasma itaitubense, D. formosum, Spirifer subtesta, Orthotichia magnifica. In the southern belt it yields such Fusulinids as the Schwagerina sp., Parafusulina sp.; such corals as Waagenophyllum sp., Polythecalis sp., brachiopods such as Dictyoclostus sp., Choristites sp., Athyris sp.; Ammonoids such as Agathiceras altunense, Popanoceras aff. bowmani, Propinacoceras kunlunense, Kunlunnoceras kunlunense, Peritrochia cf. porkor, Perrinites cf. beedei; and bivalves, etc.
Age
Depositional setting
It is interpreted as a marine-facies
Additional Information