Cuiyibi Fm

The type section is located in Weixi County, Yunnan Province, which was named by regional geological survey of Yunnan Bureau of Geology and Mineral Resources in 1984. Originally, the Cuiyibi Fm represented intermediate-basic volcanic rocks predominated strata around the Weixi County of Yunnan Province, and stratigraphically between the Pantiange Fm of Middle Triassic and Shizhongshan Fm of Upper Triassic, and suggestive of Carnian of Late Triassic. However, the Cuiyibi Fm was regarded as partial of coeval Pantiange Fm (acid volcanic rocks) by Bureau of Geology and Mineral Resources of Yunnan (1990) and therefore, not used. After detailed comparison of the Cuiyibi Fm and Pantiange Fm by Chengdu Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences and regional geological group of Bureau of Geology and Mineral Resources of Sichuan in 1992, these formations were suggested of Anisian to lower Ladinian of Middle Triassic. The later definition was followed herein, but the time interval of these two formations was ascribed tentatively to Ladinian of Middle Triassic to Carnian of Late Triassic.

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This formation is consisted by 9 eruption cycles, and each cycle is dominated by andesitic basalt, almond basalt, brigitte keratophyre, andesite, rhyolite, volcanic breccia, tuff, sandy slate, mudstone, limestone, and radiolarian chert. Thickness is more than one thousand meters.

Ammonoid: Trachyceras? sp.; Bivalves: Radulonectites? sp., Chlamys sp., Comptochlamys? sp., Syncyclonema? sp., Psedomytilaides sp., Inoceramidae. Crinoid: Cyclocylicus sp. Brachiopod: Oxycolpella sp. and gastropods and conchostracans.

Marine volcanic-sediments sequence