Local overprints on the global carbonate δ13C signal in Devonian-Carboniferous boundary successions of South China

An integrated study of the litho-, bio-, and chemostratigraphy of the Devonian-Carboniferous boundary at four sections (Qilinzhai, Malanbian, Gedongguan and Long'an) in South China was undertaken in order to better understand paleoenvironmental changes and controls on δ13Ccarb variation during the Hangenberg Crisis. Sedimentological data record a major regression in the Middle Siphonodella praesulcata Zone, which coincided with the Hangenberg Extinction (HE) in South China. Our new δ13Ccarb data document a negative δ13Ccarb shift near the base of the Middle S. praesulcata Zone, which may have been related to the HE. Prior to and during the HE, respiration of organic matter contributed abundant 12C-enriched dissolved inorganic carbon (DIC) to the restricted Nanning carbonate platform, resulting in a negative vertical δ13CDIC gradient in the study area. In the Upper S. praesulcata Zone, all four sections exhibit a positive δ13Ccarb shift, suggesting that a vigorous biological pump existed in the aftermath of the latest Devonian glaciation. However, peak δ13Ccarb values differ markedly among the study sections, suggesting that local carbon cycling processes played an important role during the initial post-glacial transgression.