A negative carbon isotope excursion defines the boundary from Cambrian Series 2 to Cambrian Series 3 on the Yangtze Platform, South China

A globally recorded negative carbon isotope excursion characterizes the transition from Cambrian Series 2 to Cambrian Series 3. This transition is also well exposed in sedimentary successions on the Yangtze Platform, and the Wuliu–Zengjiayan section, Guizhou Province, South China has been proposed as a potential Global Stratotype Section and Point (GSSP) for this boundary. Here, we report δ13Ccarb values for the Jianshan and the Wuliu–Zengjiayan sections. Both sections display a progressive decrease in δ13C from values around + 3‰ upwards in stratigraphy to a pronounced δ13C minimum with values as low as − 6.9‰ at the proposed boundary level, and a return to δ13C values between 0 and + 1‰ in the upper part of the sections. The δ13C minimum is thought to be caused by a transgressive event, flooding the shelf area with 13C depleted basinal anoxic bottom water. Our δ13C data are in good agreement with carbon isotope profiles recorded elsewhere. These define the so called ROECE event (Redlichiid–Oleneliid Extinction Carbon Isotope Excursion, cf. Zhu et al., 2006, 2007) and may reflect the perturbation of the global carbon cycle during the Cambrian Series 2 to Cambrian Series 3 transition.