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The terrestrial Triassic and Jurassic sequences are continuously cropped out in the Sichuan Basin,China yielding diverse fossil biota.The Upper Triassic deposits are represented by the Xujiahe Formation with abundant and diverse fossil,including plants,spore-pollen,bivalves,conchostracans and ostrocodes,indicating Norian to Rhaetian age.The Lower Jurassic sequences Zhenzhuchong and Ziliujing Formations consist of shell limestones,purple red mudstone and limestones with sandstone or variegated bed.The former formation is the basal part of the sequence (ca.corresponding to the Hettangian).The Triassic/Jurassic boundary is defined in between the Upper Jurassic Xujiahe Formation and the base of Lower Jurassic Zhenzhuchong Formation.