Geological event sequences of the Permian-Triassic transition recorded in the microfacies in Meishan section  

作　　者：CAO ChangQun ZHENG QuanFeng 

机构地区：[1]State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China

出　　处：《Science China Earth Sciences》2009年第10期1529-1536,共8页中国科学（地球科学英文版）

基　　金：Supported by Chinese Academy of Sciences (Grant No. KZCX2-YW-122);Project of the Ministry of Science and Technology of China (Grant No. 2006CB806400);National Natural Science Foundation of China (Grant No. 40473003)

摘　　要：The microfacies sequence in the key interval of Beds 24―29 of the Meishan section comprehensively recorded the geological events during the Permian-Triassic transition, including the anoxia, storm disturbance, hard-ground/firm-ground form, volcanic eruption, weathering input, and microbialite development. This investigation of event sequences on the microfacies provided synthetically some clues to clarifying the previously proposed mechanisms of the end-Permian extinction. The deposit succession in Bed 24 of the Changxing Formation was developed dominantly with organic-rich lamina, but interrupted intermittently by storm disturbances. It indicates characteristically a stagnated, stratified and anoxic ocean during the latest Permian. The latest Permian transgression occurred rapidly at the top of Bed 24d and was characterized by the hard-ground interface. Abundant clay mineral of illite indicates the occurrence of persistent weathering of continental volcanics and then buried in ocean throughout this key Permo-Triassic transitional interval. However, the "boundary ash clay" of Bed 25 yielding normal grading of hyaloclastite was the result of precipitation of volcanic dusts. The firm-ground substrate in Unit 27-2 was lithe and excavated intensively by trace fossil Glossifungites; it means also the occurrence of the earliest Triassic rapid transgression and coincides with the first appearance of conodont Hindeodus parvus. Dune-shaped microbialite in Unit 27-5 defines biostrati-graphically that its development, especially in the carbonate platform of South China, should corre-spond to the earliest Triassic; and it also indicates the final episode of the end-Permian extinction event.The microfacies sequence in the key interval of Beds 24–29 of the Meishan section comprehensively recorded the geological events during the Permian-Triassic transition, including the anoxia, storm disturbance, hard-ground/firm-ground form, volcanic eruption, weathering input, and microbialite development. This investigation of event sequences on the microfacies provided synthetically some clues to clarifying the previously proposed mechanisms of the end-Permian extinction. The deposit succession in Bed 24 of the Changxing Formation was developed dominantly with organic-rich lamina, but interrupted intermittently by storm disturbances. It indicates characteristically a stagnated, stratified and anoxic ocean during the latest Permian. The latest Permian transgression occurred rapidly at the top of Bed 24d and was characterized by the hard-ground interface. Abundant clay mineral of illite indicates the occurrence of persistent weathering of continental volcanics and then buried in ocean throughout this key Permo-Triassic transitional interval. However, the “boundary ash clay” of Bed 25 yielding normal grading of hyaloclastite was the result of precipitation of volcanic dusts. The firm-ground substrate in Unit 27-2 was lithe and excavated intensively by trace fossil Glossifungites; it means also the occurrence of the earliest Triassic rapid transgression and coincides with the first appearance of conodont Hindeodus parvus. Dune-shaped microbialite in Unit 27-5 defines biostratigraphically that its development, especially in the carbonate platform of South China, should correspond to the earliest Triassic; and it also indicates the final episode of the end-Permian extinction event.

关 键 词：MEISHAN PERMIAN-TRIASSIC TRANSITION MICROFACIES event SEQUENCES 

分 类 号：P534.46[天文地球—古生物学与地层学]