Carbon-isotope analyses of fossil plants as a chemostratigraphic and palaeoenvironmental tool



A review of carbon-isotope analysis (δ13C) of terrestrial organic matter indicates that this has become a valuable tool for stratigraphic correlation between marine and non-marine sequences as well as providing palaeoenvironmental information. Early Cretaceous fossil wood was collected over a 64 cm section from Flat Rocks, southeastern Australia, and analysed for carbon-isotope ratios. Three positive δ13Cplant shifts were recorded, and a similar pattern was found in the carbon/nitrogen (C/N) ratio of the plant fragments. Comparisons of δ13Cplant values and C/N ratios with sedimentology indicate that positive shifts occur in sand-rich horizons, while negative shifts occur in mud-rich horizons. This trend most likely represents diagenetic-taphonomic changes caused by changes in the oxidation state and/or bacterial activity during deposition and fossilization of the plant matter. The application of carbon-isotope analyses on fossil plants can provide invaluable information with respect to the environment on a local, regional or global scale; however, caution must be exercised in interpreting these data accurately.