Tongzuyuan Fm
Type Locality and Naming
It was named by the Regional Survey Party of Hubei Province in 1973. The naming section is located in the area of Tongzhuyuan of Dangyang County, Hubei Province, with its reference section being situated at Xietan of Zigui County.
Synonym: （桐竹园组）; A the terms “Xiangxi System” or the “Xiangxi Gr” have been known for a long time and have long been used basically as a greater diachronous stratigraphic unit, so its group name should be reserved, and at the same time it is reasonable to subdivide the strata within the group concerned into different formations. And for this reason, the term “Tongzuyuan Formation” is used in the present lexicon.
Lithology and Thickness
It is composed of grey-green medium-, and thin-bedded clayey siltstone and silty clay rocks, intercalated with sandy shales and coal beds, with its upper part being intercalated with shelly limestone, and with its basal part with a layer of grey-white and yellow-green thick-bedded and medium-grained quartz-sandstone or pebble-bearing sandstone and conglomerate serving as its base.
Relationships and Distribution
Lower contact
It is in a disconformable contact with the underlying upper Triassic Wanglongtan Fm or the Shazhenxi Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Xietan Fm
Regional extent
It is distributed largely in the Lichuan-Zigui and Jigmen-Dangyang Basins in western Hubei. In the Zigui Basin the formation is composed mainly of yellow-grey and grey-black poststone, siltstone, mudstone and carbonaceous mudstone, intercalated with coal beds and coal seams, containing siderite concretions or its thin ore-layers, with a thickness varying in a range from 180 m to 263 m. All the biotic fossils yielded there are correlatable with those found in the Jingmen-Danggang Basin.
GeoJSON
Fossils
It yields abundant animal and plant fossils, among which the bivalve fossils are represented by the Qiyangia xianxiensis-Sibireconcha anodontoides assemblage; the plant fossils belong to the Todites princeps-Ptilophyllum assemblage; and the spore-pollen fossils are divisible into the upper and lower assemblages, with the lower assemblage being represented by the Dictyophyllidites-Classopollis-Cerebropollenites, and with the upper assemblage being represented by the Dictyophyllidites-Cyathidites-Classopollis.
Age
Depositional setting
The formation belongs to continental fluvial-lacustrine and swamp-facies coal-bearing deposits.
Additional Information