Isotope reconstruction of plant palaeoecology. Case study of Cenomanian floras from Bohemia

Palaeoenvironments inferred from stable carbon isotope ratios of fossil plants collected from various environments of the Cenomanian of Bohemia were compared with palaeobotanical and sedimentological data to test the use of isotope ratios as a record of local palaeoenvironments and fossil-plant ecology. A number of isotope and biogeochemical patterns suggested that stable carbon isotope ratios in the Cenomanian plants from Bohemia have not been significantly affected by diagenesis. Stable carbon isotope ratios of the palaeoflora from one of the sections studied were used as a reference for a non-stressed habitat since both sedimentological and palaeobotanical evidence suggested that the fossil flora underwent no environmental stresses that could have influenced its δ13C values. Comparisons of δ13C values of the other palaeofloras with that of the reference section, allowed inference of the palaeoenvironmental stresses undergone by fossil plants. These palaeoenvironmental patterns deduced from 13C/12C ratios are in agreement with the palaeoenvironments previously reconstructed by sedimentological and palaeobotanical studies. Combining evidence from those studies with isotope data provided detailed insights into the palaeoecology of the plants studied. Finally, stable carbon isotope ratios allowed precise characterisation of the ecology of the best-represented species of the deposits studied, the ginkgoalean plant Eretmophyllum obtusum and the conifer Frenelopsis alata, which were quite common in the salt-marsh environments in Europe during the Cenomanian. Hence, stable carbon isotope ratios can help in evaluating the environmental stresses undergone by fossil plants and the combination of these results with palaeobotanical and sedimentological data can provide detailed insights into fossil-plant ecology.