Puqi Fm
Type Locality and Naming
It was named as the "Puqi Purple Sandstone Formation", originally referring to the purple mica sandstone and sandy shale in the continental facies distributed around the county seat of Puqi (Puxi), Hubei Province, and the age was designated as the Triassic. Wang Zunzhou et al. (1992) maintained the lithostratigraphic range of the original "Purple Sandstone Formation of Puqi" and defined the time limit of the formation as Middle Triassic Ladinian to Early Late Triassic.
Synonym: Puxi Fm
Lithology and Thickness
It is a set of purple sand and shale with an occasional gray-green underside. Lower part is purplish red sandy mudstone interbedded with light gray fine sandstone, siltstone and grey-green sandy mudstone interbedded with yellow-green siltstone, with a thickness of 44 m. Middle part is a medium thick layer of purple and grayish purple siltstone interbedded with argillaceous siltstone and fine sandstone, with a thickness of 126 m. Upper part is purplish red silty mudstone interbedded with siltstone, fine sandstone, occasionally interbedded with thin layers of conglomerate or conglomerate lens. The mudstone is rich in calcareous nodules and pebbles with a thickness of 239 m.
Relationships and Distribution
Lower contact
At the bottom, purplish red sandy mudstone is integrated with the limestone of the underlying Middle Triassic Lushuihe Fm.
Upper contact
At the top, a pseudo-conformable surface is demarcated with the overlying Upper Triassic Jigongshan Fm
Regional extent
The formation is mainly distributed in the southeast of Hubei Province, with stable horizon and little lithologic change, but the thickness varies greatly from 50 to 1260 m, generally from 300 to 500 m. The thickness of Puqi gate is more than 364 m, and the thickness of Tu Jia is only 57 m. The thickness of Echeng Chengchao is 54 m, and that of Wangchong is 483 m. Daye Jinshan shop area thickness is greater than 766 m; The brain thickness of Huangshi lower continental peak is the largest, about 1268 m. There was only a small amount of exposure in Yangxin area.
GeoJSON
Fossils
It contains bivalve fossils Mytilus eduliformis, Modiolus sp., Bakevellia sp., Pteria sp., Pleuromya sp., Promyalina sp.; brachiopod fossils Lingula sp. and phytolith Annulepis sp. In Huadiqiao, Chengchao Daye, Echeng, in the middle and upper part of the group, it contains bivalve fossils Unionites guizhouensis, Bakevellia intermedia, Modiolus weiyuanensis, Isognomon obrupta.
Age
Depositional setting
It is interpreted as mainly continental sedimentary with a small amount of Marine intercalation.
Additional Information