Triassic trace fossils from Dinggye and Tingri,Xizang and their geological significance

The trace fossils occur in significant quantities in the Triassic strata in Dinggye and Tingri,Xizang,and may be arranged into four trace fossil assemblages roughly corresponding to the Skolithos,Cruziana and Zoophycos ichnofacies.The examination of the above-mentioned trace fossil assemblages mainly from the Qulonggongba Formation in the study areas shows that these regions were once in the continental shelf environment during the Early and Middle Triassic and in the littoral environment during the Late Triassic.In addition,there existed a temporary anoxic event during the Early Triassic,