MULTIPLE DELTA-13C EXCURSIONS SPANNING THE CAMBRIAN EXPLOSION TO THE BOTOMIAN CRISIS IN SIBERIA

New high-resolution deltaC-13 data through the Lower Cambrian of Siber ia reveal multiple, positive excursions coincident with phases in the ''explosion'' of invertebrate phyla (Nemakit-Daldynian to middle Botom ian stages). Comparison of the deltaO-18 and trace element (Mg, Fe, Mn , Sr) chemistry indicate that six new deltaC-13 cycles are primary rat her than diagenetic features, with potential for global correlation. P ositive deltaC-13 excursions up to +3 parts per thousand indicate that fractional organic carbon burial rates were high but variable through the Cambrian explosion. Values for deltaC-13 dropped sharply from aro und +2.2 parts per thousand to -1.6 parts per thousand in Botomian tim e, coincident with mass extinction of the archaeocyathan reef biota. T he rapid fluctuation of the deltaC-13 signal and the temporal coincide nce of the pronounced negative shift with the extinction event hint th at the deltaC-13 record may record productivity variations during the Early Cambrian radiation.