Boda Fm

The type section is located in Boda Village, Yanyuan County, Sichuan Province, which was named by the first survey team of Bureau of Geology of Sichuan in 1971. The Boda formation was divided into lower, middle and upper part of Boda formation when named, representing shallow marine to continental deposits in Yanyuan, Sichuan province, and indicative of Carnian, Norian and Rhaetian, respectively. Subsequently, this definition was abandoned by the First Regional Geological Team of Bureau of Geology of Sichuan (1974), and the lower and the upper Boda formation was renamed as Shemulong Fm and Donggualing Fm, respectively, and the middle Boda formation was ascribed to Boda Formation. The revised Boda Formation was used by regional geological team of Bureau of Geology of Sichuan and Nanjing Institute of Geology and Biology, Chinese Academy of Sciences (1982), and suggestive of Norian of Late Triassic. This definition was used herein.

Synonym:

The Boda formation is characterized by clastic interbedded with carbonates. It consists of grey and dark grey medium-massive sandstone, siltstone and shale intervened by coal stem and carbonaceous shale. Limestone, bioclastic limestone, oolitic limestone and chert nodular limestone are common in the lower-middle part. Base and top of the Boda Formation were marked by the first and last occurrence of grey, white feldspathic sandstone with lenticular marlstone interlayers, respectively. Thickness for this formation is around 800-1100 m.

Mainly bivalve and ammonoid, with a few coral, brachiopod, foraminifer, crinoid, sea urchin, gastropod, and plant fragments. Bivalve: Burmesia lirata-Costatoria napengensis assemblage or Pergamidia eumenea-Suchuania difformus assemblage. Ammonoid: Gonionotites-Juvavites assemblage

Nearshore marine facies