Tying platform drowning to perturbations of the global carbon cycle with a δ13COrg-curve from the Valanginian of DSDP Site 416 |
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| Authors: | Ulrich G Wortmann & Helmut Weissert |
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| Institution: | GEOMAR Research Center for Marine Sciences, Wischoffstr. 1–3, D–24148 Kiel, Germany;Geological Institute, Swiss Federal Institute of Technology, Zurich, CH–8092 Zürich, Switzerland |
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| Abstract: | The carbonate carbon isotope record of the Phanerozoic is marked by repeated high-amplitude excursions towards more positive values. Although the interpretation of C-isotope events remains controversial, they are regarded as a proxy of the global C-cycle. Using δ13COrg-measurements of samples from DSDP Site 416, it is shown that a classic example of platform drowning coincided with the onset of the mid-Valanginian carbon-cycle excursion. Widespread carbonate platform drowning would have contributed to the observed positive shift in the C-isotope record. As choking of carbonate production was compensated by increased organic production, both processes favoured a shift in marine carbon partitioning from the oxidized to the reduced carbon reservoir. This would have resulted in an increased flux of CO2 from the atmosphere into the marine and sedimentary carbon reservoir. |
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