139 / 2014-09-05 16:35:07

Inorganic Carbon Isotopic Anomalies Across The Ordovician--silurian Boundary On The Yangtze Platform, South China: An Environmental Event Interpretation

end-Ordovician glaciation,carbon and oxygen isotope,the Kuanyinchiao Bed,218

Completely recording the end-Ordovician glaciations (Hirnantian) with the mass extinction and associated environmental changes, a set of strata across the Ordovician-Silurian boundary from the Guanyinqiao Section, Chongqing and the Huanghuachang Section, Hubei are sampled for high-resolution inorganic carbon and oxygen isotope. The compilation of the new δ13Ccarb curves with other sections in South China shows different magnitude of negative δ13Ccarb excursions in the Upper Ordovician Kuanyinchiao Bed, which contradicts the global positive Hirnantian Isotopic Curve Excursion event (HICE). This inorganic carbon anomaly in South China indicates the injection of massive extra light carbon (12C) component into the dissolved inorganic carbon reservoir (DIC) of the Yangtze Sea at the Hirnantian glaciations, owing to aerobic or/and anaerobic oxidation of methane (AOM) and organic matters during the glacio-eustatic sea-level drop in South China.