Carbon isotope (δ13Ccarb) stratigraphy of the Lower-Upper Ordovician of the Yangtze Platform, South China: Implications for global correlation and the Great Ordovician Biodiversification Event (GOBE)

We present new high-resolution carbonate carbon isotope data (delta C-13(carb)) from four sections in the Yangtze Platform, South China, ranging in age from Tremadocian to early Katian. The data have five distinct characteristics: 1) A prominent delta C-13(carb) increase from -2.79 parts per thousand to 0.13 parts per thousand at the base of the Ordovician within the Tremadocian Cordylodus angulatus-Rossodus manitouensis Zone. 2) A positive delta C-13(carb) excursion from -2.56 parts per thousand to 0.58 parts per thousand in the Paltodus deltifer Zone during the late Tremadocian. 3) A gradual increase in delta C-13(carb) from -1.16 parts per thousand at the top of the Oepikodus communis Zone to a peak of similar to 0.74 parts per thousand in the Baltoniodus triangularis Zone at the Floian-Dapingian boundary. 4) A moderate rise in delta C-13(carb) from 0.59 parts per thousand to 1.24 parts per thousand in the middle Darriwilian Dzikodus tablepointensis Zone. 5) A distinct positive delta C-13(carb) excursion from 0.86%o to 2.32 parts per thousand at the base of the Amorphognathus superbus-Hamarodus europaeus Zone during the early Katian. These excursions can be correlated with C-isotopic trends identified in age-equivalent successions in South China, Argentine Precordillera, North America, and Central Sweden, demonstrating their potential for global correlations and providing a composite, high-resolution chemostratigraphic framework for sedimentary records of the Lower-Upper Ordovician in South China. Besides, our data demonstrate a temporal coincidence between the long-term rise in delta C-13(carb) and the Great Ordovician Biodiversification Event, suggesting that enhanced organic matter burial and accompanied climatic cooling and oxygenation may have played an important role in promoting the increases in biodiversity during the Ordovician.

Automated summary

High-resolution carbonate carbon isotope data from the Yangtze Platform in South China reveal five distinct characteristics of δ13C(carb) variations, which can be correlated with equivalent successions in other regions, demonstrating their potential for global correlations. The data also suggest a temporal coincidence between long-term rises in δ13C(carb) and the Great Ordovician Biodiversification Event, indicating a possible role of enhanced organic matter burial in promoting biodiversity during the Ordovician.