Zhangjiatun Fm
Type Locality and Naming
It was named by the Research Group, Faculty of Geology and Exploration, Changchun College of Geology in 1975 and published by Liu Fa and Huang Zhuxi (1977). The type section is located at Beishan, Zhangjiatun of Soudengzhan Township, Yongji County, Jilin Province, which is about 15 km west of the Yongji County seat.
Synonym: (张家屯组)
Lithology and Thickness
It consists of a suite of yellow green, gray purple, dark gray, yellow brown clastic rock and pyroclastic rock: Basal conglomerate with granite gravels; Lower part of pebbly granitic grit; Middle part of pelitic siltstone with micritic sandstone partings and rich fossils; Upper part consists of sandstone with limestone lenses; and Topmost purple pebbly tuffaceous siltstone.
Relationships and Distribution
Lower contact
The formation rests disconformably on the Caledonian alkaline granite. Regionally, the next older units are the Hulan Gr (central Jilin; Silur 8 column) or volcanics of the Taoshan Fm (Jilin-Liaoning-Inner Mongolia corner; Silur 9 column) of Silurian.
Upper contact
No upper boundary observed. Regionally, the next younger unit is the Xiaosuihu Fm of uppermost Silurian.
Regional extent
The formation, approximately 370 m in thickness, is only observed at Hanguangfutun-Zhangjiatun, Soudengzhan Township, Yongji County, Jilin Province. According to brachiopod and other fossils discovered the formation is comparable with the Xibiehe Fm in the central part of Inner Mongol.
GeoJSON
Fossils
The main fossils of the formation are represented by brachiopods, the Retziella simplex-Protoreticularia fimbriata assemblage, including the main elements as follows: Salopina classiformis, Chonetoidea, Coelospirella, Retziella simplex, Reticulatrypa variabilis, Striispirifer, Hedeina aff. Annanias Howellella nucula, Protoreticularia fimbriata, etc.; anthozoa Schlotheimophyllum, Aulopora, Heliolites; trilobites Coronocephalus (Paracoronocephalus), Encrinuroides, Odontopleura, etc.
Age
Depositional setting
Additional Information