Carbon isotope composition of the Lower Triassic marine carbonates, Lower Yangtze Region, South China  

作　　者：ZUO Jingxun1,2, TONG Jinnan3, QIU Haiou4 & ZHAO Laishi3 1. Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China 2. Henan Institute of Geological Survey, Zhengzhou 450007, China 3. State Key Laboratory of Geological Processes and Mineral Resources at China University of Geosciences, Wuhan 430074, China 4. Faculty of Material Sciences and Chemical Engineering, China University of Geosciences, Wuhan 430074, China 

出　　处：《Science China Earth Sciences》2006年第3期225-241,共17页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.40325004);the Ministry of Science and Technology of China(Grant No.G2000077705).

摘　　要：Studies on three Lower Triassic sections located on the shallow water platform, the deep water slope and in the deep water basin in the Lower Yangtze Region, South China, show the similar trend of carbon isotope evolution. Biostratigraphic correlations among the Lower Triassic sections on the basis of standard conodont zones indicate that three negative shifts occurred in the Griesbachian, the Smithian and the late Spathian stages respectively, and one distinctly positive shift occurred in the early Spathian stage. Trend of carbon isotope evolution of the Lower Triassic reflects some significant changes in the global carbon cycle. Moreover, δ 13C background values are intensively controlled by palaeogeographic environment. In general, δ 13C values from deep-water slope carbonates are lighter than those from carbonate platform and heavier than those from deep-water basin carbonates. The positive carbon isotope excursion may be induced by a significant amount of organic carbon burial in marine sediments and increase in primary productivity. The large negative carbon isotope excursions during the Early Triassic in Lower Yangtze Region are interpreted to relate to volcano eruptions based on tuffaceous claystone interlayers observed near the Permian-Triassic boundary, the Induan- Olenekian boundary and the Lower Triassic-Middle Triassic boundary.Studies on three Lower Triassic sections located on the shallow waterplatform, the deep water slope and in the deep water basin in the Lower Yangtze Region, South China,show the similar trend of carbon isotope evolution. Biostratigraphic correlations among the LowerTriassic sections on the basis of standard conodont zones indicate that three negative shiftsoccurred in the Griesbachian, the Smithian and the late Spathian stages respectively, and onedistinctly positive shift occurred in the early Spathian stage. Trend of carbon isotope evolution ofthe Lower Triassic reflects some significant changes in the global carbon cycle. Moreover, δ^(13)Cbackground values are intensively controlled by palaeogeographic environment. In general, δ^(13)Cvalues from deep-water slope carbonates are lighter than those from carbonate platform and heavierthan those from deep-water basin carbonates. The positive carbon isotope excursion may be induced bya significant amount of organic carbon burial in marine sediments and increase in primaryproductivity. The large negative carbon isotope excursions during the Early Triassic in LowerYangtze Region are interpreted to relate to volcano eruptions based on tuffaceous claystoneinterlayers observed near the Permian-Triassic boundary, the Induan-Olenekian boundary and the LowerTriassic-Middle Triassic boundary.

关 键 词：LOWER Triassic  carbon isotope compositions  palaeogeography  VOLCANIC eruptions  LOWER YANGTZE Region. 

分 类 号：P588.245[天文地球—岩石学] P597[天文地球—地质学]