SEDIMENTARY ENVIRONMENTS OF THE CHERT(SILICEOUS ROCKS)FROM THE LOWER PERMIAN GUFENG FORMATION IN NORTHEASTERN SICHUAN

There is considerable debate concerning the genesis of the chert (i.e. siliceous rocks from the Maokou Formation) from the Lower Permian Gufeng Formation in northeastern Sichuan in recent years. It is notorious that it is formed in an intraplatform trench environment with a water depth of more than 60 m, or in a deep-sea basin to deep-sea trench environments. The authors feel instead that the siliceous rocks in the Gufeng Formation should be interpreted as having formed in the shallow-water lagoon gulf and restricted platform with a water depth of only several metres in terms of the study of the Permian petrographic sections in Nanjiang and Wangcang coupled with plentiful geological data from northeastern Sichuan.