Leijiatun Fm
Type Locality and Naming
It was named by Yang Yugang, Rong Jiayu et al in 1970 (the Nanjing Institute of Geology and Paleontology, the Academy of China, 1974). The type section is located at west of the roadside from Shiqian to Longtang, approximately 1.5 km northwest of Leijiatun Village, about 5 km north of the Shiqian County seat, Guizhou Province.
Synonym: (雷家屯组)
Lithology and Thickness
The formation, 87 m in thickness, can be subdivided into three parts. The Lower and Middle parts consist of yellow green, gray blue shale and mudstone with limestone lenses. The Upper part is composed of shale intercalated with thin layers of knotty marl which upwards increasing in layers and reaching nearly 4 m thick at the top.
Relationships and Distribution
Lower contact
The Leijiatun Fm is in continuous sedimentation with the underlying Xiangshuyuan Fm
Upper contact
The Leijiatun Fm is in continuous sedimentation with the overlying Majiaochong Fm.
Regional extent
The formation is exposed in the areas of northeast Guizhou and western parts of Hunan and Hubei Provinces. In Sinan, Wuchuan and Fenggang, slight changes in argillaceous content and thickness can be observed. The formation is well developed at Longjinpuo of Wuchuan and bears rich fossils like several graptolite beds: Pristiograptus xiushanensis, Monograptus sp., Dictyonema cf. desmoids. In the area of northwest Hunan and southwest Hubei it is dominated by limestone and knotty limestone and the argillaceous content decreases considerably in comparison with that observed in the type section area. The Leijiatun Fm has widespread limestone at its top, which represents the highest horizon of the Llandovery layered limestone in the above-mentioned areas.
GeoJSON
Fossils
The middle and lower parts are rare in fossils, but the upper part includes brachiopods Beitaia cf. modica, Isorthis sp., Zygospiraella sp., Striispirifer sp., Nalivkinia sp., Nucleospira sp.; trilobites Shiqiania, Astroproetus, Ptilillaenus; anthozoa Amplexoides, Brachyelasma, Ceriaster, Stauria, Pilophyllia, Codonophyllum, Tryplasma, Rhizophyllum, Qianbeilites, Microplasma, Parastriatopora, Schedohalysites, Palaeofavosites, Mesofavosites, Favosites; crinoid columnal Petalocrinus sinensis, P. chiai, Spirocrinus typicus, Sinopetalocrinus robustus. In addition, Gan Liangyu (1990) found chitinozoa assemblages the Conochitina cf. iklaensis and the C. shiqianensis, etc. in the lower part.
Age
Depositional setting
Additional Information