Tangjiaba Fm
Type Locality and Naming
The type section of the Tangjiaba Formation is the Tianpeng-Bocaitian section (105°23’E, 23°21’N). It is the upper-middle portion of same section shared by the underlying Tianpeng Fm and Longha Fm and the overlying Bocaitian Fm, lying 9.5 km northwest of the Tianpeng Town, or about 40 km southwest of the seat of Funing County. It is a long section that spans the border between Funing and Malipo counties with the Tianpeng Fm belonging to Funing County on the east and Bocaitian Fm belonging to Malipo County on the west. The section was measured by the Guangxi Bureau of Geology and Guangxi Regional Geological Survey Team in 1965. The Tangjiaba Formation was published by Liu Yuanzheng et al. (1965) from Geological Bureau of Guangxi Zhuang Autonomous Region. The name is derived from Tangjiaba Village, Funing County, southeastern Yunnan Province, and was originally appeared in a 1964 manuscript by the No. 4 Brigade of Yunnan Regional Geological Survey Team.
Synonym: （唐家坝组）; A Xiechang Fm, originally erected by faunal content was positioned between the Longha Fm below and the Tangjiaba Fm above. Based on its lithology, Zhang (1996) lumped it with Tangjiaba Formation as both formations share almost the same lithological features. The expended concept of the Tangjiaba Formation by Zhang (1996) is followed in this Lexicon.
Lithology and Thickness
The Tangjiaba Formation is mainly a clasctic and carbonate sequence. Lower part consists mainly of greyish green and yellowish grey, silty mudstone, argillaceous striped limestone, interbedded with dark grey, thick-bedded dolomitic limestone and thick-bedded limestone. Upper part consists mainly of light and dark argillaceous limestone, dolomitic limestone, interbedded with greyish green siltstone and silty mudstone. In the type section, the Tangjiaba Fm is 1521 m thick.
Relationships and Distribution
Lower contact
The Tangjiaba Fm is in conformable contact with the underlying Longha Fm. The lower boundary of the formation is defined by lithological change from the medium-bedded dolomite (or limestone) at the top of the Longha Fm to the silty mudstone of the Tangjiaba Fm
Upper contact
The Tangjiaba Fm is in conformable contact with the overlying Bocaitian Fm. The upper boundary is marked by the lithological change from argillaceous limestone at the top of the Tangjiaba Fm to the sandy mudstone that is dominant in the basal part of the Bocaitian Fm.
Regional extent
Tangjiaba Formation is exposed in the southeastern part of the Yangtze Area of South China Region, very close to the Jiangnan Slope Area, distributed in the counties merely in southeastern corner Yunnan Province, including Finning, Guangnan, Maguan, Wenshan and Xichou counties belonging to the Wenshan Zhaun-Miao Autonomous Prefecture and Menzi and Pingbian counties belonging to the Honghe Hani-Yi Autonomous Prefecture. The formation increases interbeds of sandstone and shale southeastward whereas decreases carbonate rocks. Thickness of the formation varies between 735.9 and 1521 m.
GeoJSON
Fossils
In the lower part of the Tangjiaba Formation yields trilobites Annanmitia spinifera, Blackwelderia paronai, B. sinensis, Teinistion sp., Homagnostus sp., Liaoningaspis sp., Parablackwelderia sp., P. deprati, Paracoosia sp., Pseudagnostus sp., Pterocephalia s,, Stephanocare cf. richthofeni, and the upper part of the formation fields trilobites Changshania sp., Chuangia sp. Irvingella sp., Kaolishania sp., Shirakiella sp., Lioparia sp., Maladiodes sp., Prochungia sp., Pseudagnostus sp. and Shihuigouia sp. The formation yields also brachiopods Acrothele sp., Apheorthis sp., Billingsella simplex, Huenella orientalis, Lingulella sp., Mesonomia sp., Nisusia sp., Obolus sp., Palaeobolus sp., and Palaeostrophia orthia
Age
Depositional setting
Additional Information