Carbon isotope anomaly and other geochemical changes at the Triassic-Jurassic boundary from a marine section in Hungary

Most mass extinctions are linked with carbon isotope excursions, implying t hat biotic crises are coupled with changes in the global carbon cycle. The isotopic evolution during the end-Triassic extinction is far less documente d than that for the other major Phanerozoic extinctions. Here we report a s harp and short-lived -3.5 parts per thousand excursion in carbon isotope va lues for carbonate (delta C-13(carb)) corresponding to a -2 parts per thous and excursion in the isotopic composition of marine organic matter (delta C -13(org)) and other: geochemical changes from the topmost Triassic in the C sovar section in Hungary. The Triassic-Jurassic boundary is defined by ammo noid and conodont biostratigraphy in a marine limestone sequence. A decline in primary productivity, release of methane through dissociation of gas hy drates, or a combination of the two may account for the correlative biotic and isotopic events.