The discovery of conodonts fossils and the strontium isotope composition of Labuchari Formation in Tanggula Range and their stratigraphic significance

Conodont fossils were found for the first time in the Late Permian Labuchari Formation in the Tanggula Range. The conodonts include Hindeodus typicalis, H. eurypyge and H. praeparvus. According to their significance and the investigation of sequence stratigraphy and sea-level changes, the Permian/Triassic boundary may be determined between the top of 29 and the bottom of 30 of the measured section. Here, the carbonatite ⁸⁷Sr/⁸⁶Sr ratios of Labuchari Formation were determined. At the Permian/Triassic boundary, ⁸⁷Sr/⁸⁶ Sr ratios are from 0.707017 to 0.707032, which are significantly lower than those in other areas. The main reasons for the remarkable difference might be the existence of extensive volcanic activities in Tangula Range at the Permian/Triassic boundary and the basalt eruptions in Yangtze region during the late Permian. In addition, the comparison between the strontium isotope curve and sea-level curve shows that the minimum ⁸⁷Sr/⁸⁶Sr ratio has a good consistency with the data of the first flooding surface, suggesting that global sea level change was the main factors controlling the strontium isotope.