Research project

The aim of the project is a global, high resolution 13C record of Devonian to Permian rocks. Carbonates are susceptible to diagenetic alteration. Therefore, only primary low magnesium calcite components (brachiopods, marine cements) or phosphates (conodonts) are suitable for oxygen isotope analysis. In contrast, the carbon reservoir of carbonates is so huge that late diagenetic recrystallization will not change the isotope ratios significantly. But early diagenesis under the influence of freshwater or remineralized organic carbon can alter the original signal considerably. I will show that the carbon isotope ratio is well preserved when early diagenetic stabilization and cementation of the carbonates took place under the presence of marine pore water and absence of CO2 from organic matter. Local diagenetic overprint can be excluded, when the same changes in the isotope curve can be observed in several sections. An additional test is the covariance of 13Ccarb and 13Corg because their diagenetic alterations follow different paths. The advantage of using whole rock carbonates is that they are available to such an extent that a high stratigrapic resolution can be obtained. In order to proof that an isotope shift or excursion is global, it has to be detected in different paleoozeanographic settings (e.g. Panthalassia and Paleotethys).