Toupossu Fm
Type Locality and Naming
The type section of the Toupossu Formation is located on the top flat ground of a hill, close to Laoshenken Village (103°11’E, 24°49’N), and the Douposi Temple (now called Yunquan Temple) was built at half way of the hill slope. At the type locality, the formation is poorly outcropped. A section, measured at Chenguanying, 2.5 km northwest of Douposi in Yiliang County (103°11’E, 24°49’N) by Zhang Wentang and colleagues from the Nanjing Institute of Geology and Palaleontology in 1973, was commonly regarded a representative section of the Toupossu Formation. The Chenguanying section lies about 14 km southeast of the seat of Yiliang County. A section, the Longzhaosi section on the east slope of the Longzhaosi Hill is selected as auxiliary section for the formation by Luo et al. (1993), who measured the section parallel to and at about 1 km south of the Chenguanying section and by Zhang (1996). The Toupossu Formation was first published by Xie (1941). The name is derived from Toupossu (spelled Douposi in Hanyu Pinyin) Temple, Yiliang County, Kunming City, eastern Yunnan Province. The name was originally appeared in a 1939 manuscript by Lu Yanhao and Wang Hongzhen, who called the unit Toupossu Bed, which is followed by Xie (1941). Lu (1963, p. 324) renamed the unit Toupossu Formation.
Synonym: （陡坡寺组）
Lithology and Thickness
The Toupossu Formation is a clastic and carbonate sequence. In the type section, the formation consists of yellowish green siltstone, shale, argillaceous dolomitic limestone, and bioclastic dolomite. Lower part, 7 m thick, consists of yellowish green quartzose silty shale, yellow thin-bedded feldspathic micaceous quartzose siltstone, and yellow thin-bedded dolomitic feldspathic siltstone and fine-grained sandstone; Upper part, 49 m thick, consists of grey and yellow, thin-bedded to massive bioclastic dolomite and dark grey, thin-bedded argillaceous dolomitic limestone with interbeds of minor argillaceous shale.
In most areas, the Lower part of the formation is dominated by clastic rocks, and the Upper member is chiefly composed of magnesium-rich carbonate (dolomitic) rocks. However, at Shuanglongtan in Qujing County, Yunnan Province, both the upper and lower parts are composed of sandstone with interbeds of limestone in the middle part. In Ermei and Nanjiang of Sichuan Province, the formation increases the purplish red and brick red siltstone and mudstone to the clastic rocks.
Relationships and Distribution
Lower contact
The Toupossu Fm rests conformably on the Lungwangmiao Fm or Shihlungtong Fm. Its lower boundary is defined by the disappearance of dolomite of the underlying formation and appearance of siltstone or silty shale of the formation.
Upper contact
It is conformably overlain by the Shuanglongtan Fm (Shuanglungtan Fm), Hsiwangmiao Fm or Loushankuan Fm. the upper boundary is defined by the appearance of either the dolomite of Shuanglongtan Fm (Shuanglungtan Fm) or Loushankuan Fm or the purple and brick red, greyish green siltstone or mudstone of the Hsiwangmiao Fm.
Regional extent
The Toupossu Formation is exposed in the west part of the Yangtze Area of South China Region, distributed in central and northeastern Yunnan Province and eastern and south-central Sichuan Province. Its exposure coverage is slightly narrower than that of the Lungwangmiao Fm as the formation is absent in the areas south to Kunming City and northeast to Qujing City in Yunnan Province (e,g., Jingning and Xuanwei counties) and the areas west of Guangyuan‒Renshou‒Ganluo‒Xichang city line in Sichuan Province. The thickness of the formation ranges 26‒55 m in eastern Yunnan, and 20‒80 m in Ermei and Huili counties, central and southern Sichuan, and 135‒228 m in Nanjing, northeastern Sichuan.
GeoJSON
Fossils
The Toupossu Formation yields trilobites Chittidilla similis, C. yunnannensis, C. oblonga, C. nanjiangensis, C. yunshancunensis, Douposella douposiensis, D. yiliangensis, Kuetsingocephalus kuetsingensis, Kunminggaspis yunnanensis, Mufushania xundianensis, Sanhuangshania brevis, S. pulchra. Sinoptychoparia tubercilata and Solenoparia minuta, and brachiopod Lingulella sp.
Age
Additional Information