Dashizhai Fm

The type section is located in the vicinity of Dashizhai area, Youyiqian Banner, Kelqin, Inner Mongolia. It was named by the 2^nd Regional Geological Survey Party under the Geological Bureau of Inner Mongolia in 1965.

Volcanics and volcaniclastics. Composed of a suite of slightly metamorphosed intermediate-acidic lavas and tuffs, intercalated with a small amount of normal deposits. Acidic-Lava Member of its lower part represents grey-white rhyolitic porphyry, quartz-porphyry and tuff, with thickness of 115 m. Intermediate-Lava Member of its middle part is predominated by the grey-green and grey-yellow amygdaloidal andesite, intercalated with tuffaceous sandstone, slate and breccia, with a thickness of 1320 m. In the vicinity of the Dashizhai area the Intermediate-Volcaniclastics Member of the upper part of the formation is composed of grey-green and yellow-green tuff, tuffaceous sandstone, clayey slate, intercalated with limestone lenses and andesite, containing limonite and glauconite, with a thickness of 1452 m. The total thickness is 2887 m.

Brachiopod fossils are abundant, which are divisible into the lower Anidanthus aagardi-Muirwoodia mammata assemblage zone, and the upper Anidanthus ussuricus-Marginifera morrisi-Permundaria assemblage zone. In addition, its lower part yields Corals such as Bradyphyllum, and Ammonoids such as Popanoceras. Its upper part yields a fossil community as represented by Coral such as Tachylasma, etc.