Middle To Late Ordovician Carbon Isotope Chemostratigraphy Of The Lower Yangtze Platform: Implications For Global Correlation

Middle to Late Ordovician carbonates were collected in South China (Anhui Province) from the Kuniutan, Datianba, and Pagoda formations in the Dingxiang and Daling sections and analysed for high-resolution carbon isotope chemostratigraphy. An increase by 0.4 parts per thousand in delta C-13(carb) is observed in the upper part of the Kuniutan Formation (Eoplacognathus pseudoplanus Biozone), representing the rising limb of the Middle Darriwilian Isotopic Carbon Excursion (MDICE). In the upper part of the Datianba Formation, positive shifts of ca. 1 parts per thousand are recorded in the studied section which compare with the carbon shifts reported in North America and Baltoscandia. A pronounced positive delta C-13(carb) excursion of ca. 1.5 parts per thousand from the lower part of the Pagoda Formation can be correlated with the global Guttenberg Isotopic Carbon Excursion (GICE). The documentation of three carbon isotope shifts in this study provides new evidence for changes in the global carbon cycle from Darriwilian to Early Katian which could have been influenced by changes in global climate and primary productivity.