The Coupling Relationship Between Nanzhang-Yuanan Fauna And Volcanic Material In The Early Triassic Of Western Hubei

There have been many mass extinctions in the Earth's geological history,and the PermianTriassic mass extinctions have been one of the research focuses.Although there is much debate about the mechanism and cause of this extinction and environmental degradation,there is growing evidence of a temporal link between volcanism and this extinction,the volcanic ash layer in the Permian-Triassic transition of South China is one of the best evidence.On the other hand,the global ecosystem experienced a long recovery process in the early Triassic after the extinction,and the cause of the slow recovery of the early Triassic ecological environment has been own,the research on the recovery and evolution of early Triassic marine organisms is still lacking.Therefore,the study of the relationship between Early Triassic volcanism and living things can not only have a better understanding of the intensity and frequency of volcanism at that time,it can also be used to analyze the coupling relationship between volcanism and biological flexuous recovery during this period.The paper deals with the early Triassic Nanzhang-Yuan'an County fauna,which is one of the earliest Marine reptile in the world and an important carrier for the study of Triassic biological recovery.The fauna was found in the lamellar limestone in the upper part of the second member of the Jialingjiang Formation in the Nnanzhang-Yuan'an County area of southwestern Hubei Province,it provides preconditions for exploring the relationship between volcanism and living things.In order to study the internal relationship between volcanism and fauna in this period,the best exposed Zhangjiawan section in Yuan'an was selected as the research object,this paper intends to reveal the rule by studying the algal lamellae,fossil abundance and Hg/TOC ratio in the occurrence horizon of faunas.The results show that: 1.Fossils of marine reptiles are mostly preserved in algal laminar limestone,and the development of algal laminae is slightly earlier than the number of marine reptile fossils,indicating that algae may provide for the prosperity of marine reptiles in the Nanzhang-Yuanan fauna.Conditions.2.According to the fine change curve of the number of fossils in the occurrence layer of the fauna,the development process of the marine reptiles of the NanzhangYuan'an fauna is divided into the initial development period,the unstable period,and the second During the development period,the fauna disappeared in four stages.3.Using the ratio of Hg/TOC as the volcanic material index,the change curve of the ratio in the stratum was divided into four stages,and it was found that the ratio of Hg/TOC in the second stage was high and fluctuating Larger formations happen to correspond to lower levels of faunal fossil numbers.As far as this study is concerned,the bottom-up evolution of algae and marine reptiles in fauna and the changes of volcanic materials in the strata reflect the good coupling relationship between Nanzhang-Yuan'an fauna and volcanic materials.,the enhanced volcanism in the Nanzhang-Yuan'an fauna in the late Early Triassic may have caused periodic global warming,ocean hypoxia and other environmental changes,thus inhibiting the survival of organisms in the Nanzhang-Yuan'an fauna.