Marine Jurassic strata of Graze-Litang structural belt in western Sichuan, China

A set of Jurassic stratum along Graze – Litang structural belt in western Sichuan plateau has been discovered newly, and has been set for the Lizhou Formation and the Ruihuanshan Formation. The Lizhou Formation was formed by terrigenous clastic rocks, basic volcanic rocks, and belongs to the mountain depression–fluvio-lacustrine–littoral sedimentary environment. The Ruihuanshan Formation belongs to shallow marine carbonate rock mesa sedimentary environment with reefs .The Lizhou Formation includes plant sporule, and the Ruihuanshan Formation is abundant fossils of coral, hydra, stromatoporoids, pleopod, moss and alga. From bottom to top, the latter can be divided into three biologic assemblages: Verrucosisporites sp.-Punctatisporites sp., Thecosmilia cf .weberi -Pyotethmos cf. discus and Cladocoropsis mirabilis -Bauneia sp..According to the sporule in the rocks of Lizhou Formation and the age of 194.8Ma of basalt(Ar-Ar method), it is tentatively scheduled for the Early-Middle Jurassic. The Ruihuanshan Formation contains abundant biologic fossils, its era pertains to Late Jurassic.