Hongzaoshan Fm

North-central Qinghai. The Hongzaoshan Fm was named by Wang Yunshan et al., in 1980. The typical section is situated in Hongzaoshan east of Hongtiegou of Quanji Mountain, Qinghai Province. Upper formation of Quangji Gr.

Synonym: （红藻山组）

The Hongzaoshan Formation is dominated by dolomite and subdivided into three parts. Lower part is composed of gray, grayish purple thin-to medium-bedded tuffaceous psepholite [not in dictionary; seems to be lithic sandstone?], siltstone, micritic dolomite, dolomite intercalated with pisolitic tuff and green jasper, bearing stromatolites in the dolomite. Middle part is dark gray lamellar dolomite, bearing siliceous bandings and rubble horizons of intraclasts, most of which are dolomite and chert. Upper part is thick-bedded to massive dolomite, bearing stromatolites and red algae fossils. The thickness varies from 119 to 298 m and in Annanba area increases to 1410 m.

The upper part includes stromatolites: Conophyton quan jishanense, C. hongtiegouence, Anabaria f., Cryptozoon f., Katavia f., microphytolites: Plicatella quanjiensis, microplants: Asperatopsophosphaera cf. umishanensis, Trematosphaeridium holtedahlii, Polyporata obsoleta, Protosphaeridium sp., Micrhystridium sp., Symplassosphaeridium sp. etc.