Natural Gamma-Ray Anomaly and Environmental Implication in Late Changhsingian,Wolonghe Area,Eastern Sichuan Basin

The present study shows that deep water environment's hypoxia group diffusing to shallow water environment is the most important reason for the biological crisis at the end of Permian.However,there is still a considerable controversy on its mechanism.Eastern Sichuan Basin is mainly platform environment in Changhsingian,Late Permian.Based on the correlation of the continuous deposition of well profiles of Wolonghe structure in the study area,we find that the natural gamma-ray value of the carbonate formation became anomaly positive excursion before the end of the Permian extinction boundaries.Natural gammaray can reflect the variation of uranium content,when the content of argillaceous,thorium and potassium is low in carbonate formation,indicating the redox conditions of sea water.The platform environment in the study area shows different degrees of hypoxia effect in Late Changhsingian,which continues to develop until the coming of the biological extinction.The natural gamma-ray value in the study area recorded oxidation-reduction process of sea water in Late Changhsingian,and also witnessed the instability of the environment in major geological transitions period.