Sargan Fm
Type Locality and Naming
The Sargan Fm is derived from the Sargan Series proposed by No.13 Xinjiang Team of Geology in 1955-1957, and was published by Zhang et al. (1959). The type section is at Subashigou in the vicinity of Kalpin City, Xinjiang. Xiao Bing (1979) renamed it the Sargan Fm. Xinjiang Compiling Group for Regional Stratigraphic Scale (1980) restricted the Sargan Fm to the 14 m thick sequence of black graptolite shale intercalated with limestone, and established four graptolite zones. Zhou Zhiyi et al. (1990) remeasured the type section, and restudied the graptolite zones and other biozones.
Synonym: (萨尔干组); Saergon Fm
Lithology and Thickness
The Formation is composed of black calcareous graptolite shale intercalated with limestone lenses. In the type area, the Sargan Fm is 14 m thick.
Relationships and Distribution
Lower contact
It rests conformably on the limestone at the top of the Dawangou Fm
Upper contact
It is conformably overlain by the nodular limestone at the base of the Kanling Fm. The Sargan Series had previously been referred to all Ordovician overlying the Qiulitag Fm (Zhang, 1959).
Regional extent
The Sargan Fm is distributed in the vicinity of Kalpin, and is in narrow SW-NE strip. Southward, facies changes occur very rapidly. To Puchang and Sanchakou, the corresponding strata are composed of carbonate rock (Zhou et al., 1990). In Kalpin, the Sargan Fm was deposited continuously, and the type section can be considered as the boundary stratotype for the Caradoc and Llanvirn.
GeoJSON
Fossils
This stratigraphic unit yields graptolites of the D. murchisoni assemblage and N. gracilis assemblage, conodonts of P. serra assemblage and P. anserinus assemblage, and the trilobite Shumardia tarimuensis.
Age
Depositional setting
Additional Information