Longlinqiao Fm
Type Locality and Naming
The type section is located between Longlinqiao and Mapoli, 28 km south of Lixian County, Gansu Province. It was named by Xi’an Institute of Geology and Mineral Resources in 1971; Qin Fong and Gan Yiyan formally quoted it in 1976.
Lithology and Thickness
Slate, limestone. The lower part of this formation is dominated by blackish-gray to dark-gray carbonaceous sericite slate and silty slate, intercalated with thin-bedded siltstone and clayey limestone. The limestone content increases upward, and the upper part of the formation mainly consists of medium- to thick-bedded limestone. It is more than 1529 m in total thickness, with no top exposed at its type location.
Relationships and Distribution
Lower contact
The formation conformably overlies on the thin-bedded limestone intercalated with slate of the Pingtou Fm.
Upper contact
At Zhayuhenao in Dangchang County the formation conformably contacts the overlying QiguDev Fm.
Regional extent
This formation is mainly distributed in Dangchang and Lixian areas west of Xihanshui; it is 771 m thick at Zhayuhenao in Dangchang County where it conformably contacts both the underlying Pingtou Fm and the overlying QiguDev Fm. Eastwards, at Dongshan in Xihe County, the formation has a facies transition to mainly carbonate rock in the upper part of the Honglingshan Fm.
GeoJSON
Fossils
Fossils are mainly found in the limestone of middle and upper parts, with coral Disphyllum kostetskae, Sinodisphyllum simplex, Alveolites obtortus and brachiopods Pugnax sinensis, Schizophoria kansuensis, Spinatrypa bodini, Cyrtospirifer.
Age
Depositional setting
Additional Information