Oxygen and carbon isotopic records of the Late Triassic Carnian pluvial event deposits in northwestern Sichuan Province
Wang Yanyan1, Zhang Biao2, Shi Zhiqiang2, Yi Haisheng2
1 College of Materials and Chemistry ＆ Chemical Engineering，Chengdu University of Technology，Chengdu 610059，Sichuan 2 Institute of Sedimentary Geology，Chengdu University of Technology，Chengdu 610059，Sichuan
Abstract：Distinct lithological mutations from grey ooides，sponge reef limestone to grayish black shale，and then argillaceous siltstone are distinguished from the Upper Triassic Carnian marine sediments in the Mianzhu and Anxian counties in northwestern Sichuan Province，which is very similar to the sediments representing the Carnian pluvial event in western Tethys area.The stable oxygen and carbon isotopic compositions of the Carnian fossils of foraminifer，bivalve and brachiopodous shells and plant leaves are analyzed using laser micro-sampling technique.The analysis results indicate the slightly lowerδ18O values and remarkable lower δ13C values of the Upper Carnian than those of the Lower Carnian.Its believed that the isotopic compositions reflect that fresh water input into the Paleotethys ocean.We suggest that the Carnian pluvial event severely affected the deposits in the eastern Tethys area.The freshwater input in the humid conditions is one of the causes that triggered the periodic deaths and finally disappearing of the sponge reefs in the study area.
Wang Yanyan,Zhang Biao,Shi Zhiqiang et al. Oxygen and carbon isotopic records of the Late Triassic Carnian pluvial event deposits in northwestern Sichuan Province[J]. JOPC, 2012, 14(3): 375-382.
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