The Middle Permian Guadalupian witnessed significant environmental changes in the Phanerozoic such as large-scale sea-level drop,supercontinent Pangaea assembly,and transition from Early Permian glaciation to Late Per...The Middle Permian Guadalupian witnessed significant environmental changes in the Phanerozoic such as large-scale sea-level drop,supercontinent Pangaea assembly,and transition from Early Permian glaciation to Late Permian non-glacial intervals.Carbonisotope tracers can provide insights for these environmental changes.Theδ^13C studies of the entire Guadalupian epoch are rare,and most of them has focused on near the end of Guadalupian and carb on isotopes of ino ragnics.Here,we present carbon isotopic compositions of organic matters in the Guadalupian from two sections(Chaohu and Xiaolao)in the Lower Yangtze area.South China.Our results show that 313Corg profiles in the Guadalupian show a peak in the Roadian and a gradual negative shift from the Roadian to the middle Capitanian.These trends can be matched by(δ^13C changes of carbonate rocks or organic matter in South China and other places in the world,representi ng a global carb on cycle signal.The Roadian positive peak was probably due to high productivity which was caused by upwelling during cooling time.The gradual negative shift of(δ^13C was caused mainly by a decrease of organic matter burial on land and in the ocean,resulting from global sea-level drop and anoxia-caused benthos decline,respectively.The less important causes for the gradualδ^13C negative shift are volcanic-gases releasing,decreased mountain belts,and the resultant reduced silicate weathering-consumption of CO2.The gradual negative shift ofδ^13C coincides with the gradual extinction in the Guadalupian.Therefore,global sea-level drop and marine reducing conditions may be the main causes of the gradual extinction in the Guadalupian.展开更多
基金We thank two anonymous reviewers for their constructive comments.This work was funded by the National Natural Science Foundation of China(No.41762003).
文摘The Middle Permian Guadalupian witnessed significant environmental changes in the Phanerozoic such as large-scale sea-level drop,supercontinent Pangaea assembly,and transition from Early Permian glaciation to Late Permian non-glacial intervals.Carbonisotope tracers can provide insights for these environmental changes.Theδ^13C studies of the entire Guadalupian epoch are rare,and most of them has focused on near the end of Guadalupian and carb on isotopes of ino ragnics.Here,we present carbon isotopic compositions of organic matters in the Guadalupian from two sections(Chaohu and Xiaolao)in the Lower Yangtze area.South China.Our results show that 313Corg profiles in the Guadalupian show a peak in the Roadian and a gradual negative shift from the Roadian to the middle Capitanian.These trends can be matched by(δ^13C changes of carbonate rocks or organic matter in South China and other places in the world,representi ng a global carb on cycle signal.The Roadian positive peak was probably due to high productivity which was caused by upwelling during cooling time.The gradual negative shift of(δ^13C was caused mainly by a decrease of organic matter burial on land and in the ocean,resulting from global sea-level drop and anoxia-caused benthos decline,respectively.The less important causes for the gradualδ^13C negative shift are volcanic-gases releasing,decreased mountain belts,and the resultant reduced silicate weathering-consumption of CO2.The gradual negative shift ofδ^13C coincides with the gradual extinction in the Guadalupian.Therefore,global sea-level drop and marine reducing conditions may be the main causes of the gradual extinction in the Guadalupian.
