Multiple δ13C excursions spanning the Cambrian explosion to the Botomian crisis in Siberia

New high-resolution δ 13 C data through the Lower Cambrian of Siberia reveal multiple, positive excursions coincident with phases in the "explosion" of invertebrate phyla (Nemakit-Daldynian to middle Botomian stages). Comparison of the δ 18 O and trace element (Mg, Fe, Mu, Sr) chemistry indicate that six new δ 13 C cycles are primary rather than diagenetic features, with potential for global correlation. Positive δ 13 C excursions up to +3‰ indicate that fractional organic carbon burial rates were high but variable through the Cambrian explosion. Values for δ 13 C dropped sharply from around +2.2‰ to -1.6‰ in Botomian time, coincident with mass extinction of the archaeocyathan reef biota. The rapid fluctuation of the δ 13 C signal and the temporal coincidence of the pronounced negative shift with the extinction event hint that the δ 13 C record may record productivity variations during the Early Cambrian radiation.