Carbonatite alkaline magmatism associated with continental flood basalts at stratigraphic boundaries: Cause for mass extinctions

The debate between the impact scenario and the hypothesis of the Deccan vol canism leading to Cretaceous/Tertiary (K/T) extinctions is far from settled . We add a new dimension to this debate by introducing an overlooked aspect of the Deccan volcanism, the emplacement and eruption of associated carbon atite-alkaline complexes, which are capable of rapidly injecting catastroph ic amounts of CO2 and SO2 into the atmosphere. Ar-40-Ar-39 dating of one of the several coeval late-Deccan alkaline pulses has revealed that this alka line volcanism took place at the K/T boundary. A conservative estimate show s that these activities can indeed emit a substantial amount of CO2 and SO2 , comparable to that of an impact scenario, which could have enhanced the c atastrophic effects of the ongoing basaltic eruptions. Other major Phaneroz oic extinctions also show contemporaneity with the late carbonatite-alkalin e pulses of associated flood basalt provinces, suggesting a causal relation ship between such carbonatite-alkaline magmatisms and the mass extinctions.