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 that biotic crises are coupled with changes in the global carbon cycle. The isotopic evolution during the end-Triassic extinction is far less documented than that for the other major Phanerozoic extinctions. Here we report a sharp and short-lived -3.5‰ excursion in carbon isotope values for carbonate (δ13Ccarb) corresponding to a -2‰ excursion in the isotopic composition of marine organic matter (δ13Corg) and other geochemical changes from the topmost Triassic in the Csovár section in Hungary. The Triassic- Jurassic boundary is defined by ammonoid and conodont biostratigraphy in a marine limestone sequence. A decline in primary productivity, release of methane through dissociation of gas hydrates, or a combination of the two may account for the correlative biotic and isotopic events.