Terrestrial carbon-isotope records from coastal deposits (Algarve, Portugal): a tool for chemostratigraphic correlation on an intrabasinal and global scale |
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| Authors: | Ulrich Heimhofer Peter A Hochuli Stefan Burla Nils Andersen Helmut Weissert |
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| Institution: | Geological Institute, ETH Zürich, CH-8092 Zürich, Switzerland;;Paläontologisches Institut und Museum, Universität Zürich, CH-8006 Zürich, Switzerland;;Leibniz Labor for Radiometric Dating and Isotope Research, Christian-Albrechts-University Kiel, D-24118 Kiel, Germany |
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| Abstract: | ABSTRACT The carbon-isotope signature of terrestrial organic matter (OM) offers a valuable tool to develop stratigraphic correlations for near-shore deposits. A mid-Cretaceous coastal succession of the western Algarve Basin, Portugal, displays a marked negative δ13C excursion ranging from ? 21.2‰ to ? 27.8‰ in the Early Aptian followed by two shifts towards higher values (up to ? 19.3‰) during the Early and Late Aptian, respectively. The dominance of cuticle and leaf debris in the bulk OM fraction is confirmed by optical studies, Rock-Eval pyrolysis and by comparison with the δ13C signature of four different types of fossilized land-plant particles. Correlation of two terrestrial δ13Cbulk OM records from different study sites leads to a significant enhancement of the intrabasinal stratigraphic correlation within the Algarve Basin. Three prominent excursions in the Portuguese records can be correlated with existing δ13C curves from pelagic and terrestrial environments. The general carbon-isotope pattern is superimposed by small-scale fluctuations which can be explained by compositional variations within the OM. |
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