Bio- and chemostratigraphic assessment of carbon isotope records across the Triassic–Jurassic boundary at Csővár quarry (Hungary) and Kendlbachgraben (Austria) and implications for global correlations

Carbon isotope trends are useful for stratigraphic correlation, especially for time intervals when major perturbations of the global carbon cycle occurred. Such perturbations have been documented for the Triassic–Jurassic (T–J) boundary, and several successions from this time interval are characterized by (1) an initial negative excursion, followed by (2) a pronounced positive excursion and a subsequent (3) main negative carbon isotope excursion. These features, however, are not present in all T–J boundary sections, or the stratigraphic position of the positive or the main negative excursion has variable locations. In the present study, we analysed carbon isotopes in bulk carbonate from the pelagic Csővár quarry section in Hungary and from the intra-platform basin to shallow subtidal marine Kendlbachgraben section in Austria. Both T–J boundary successions are biostratigraphically well controlled enabling – with particular focus on the bio- and chemostratigraphy of other T–J boundary sections – correlation of the carbon isotope trends. This evaluation shows that the apex of the initial negative δ13C excursion occurred slightly, but distinctly, below the mass extinction event and represents an excellent stratigraphic correlation tool.