Tying platform drowning to perturbations of the global carbon cycle with adelta C-13(Org)-curve from the Valanginian of DSDP Site 416

The carbonate carbon isotope record of the Phanerozoic is marked by repeate d high-amplitude excursions towards more positive values. Although the inte rpretation of C-isotope events remains controversial, they are regarded as a proxy of the global C-cycle. Using delta (13) C-org-measurements of sampl es from DSDP Site 416, it is shown that a classic example of platform drown ing coincided with the onset of the mid-Valanginian carbon-cycle excursion. Widespread carbonate platform drowning would have contributed to the obser ved positive shift in the C-isotope record. As choking of carbonate product ion was compensated by increased organic production, both processes favoure d a shift in marine carbon partitioning from the oxidized to the reduced ca rbon reservoir. This would have resulted in an increased flux of CO2 from t he atmosphere into the marine and sedimentary carbon reservoir.