3C-O1-1000 PDF
隕石衝突が引き起こす海洋酸性化と白亜紀末の生物大量絶滅事件
The Cretaceous–Palaeogene (K–Pg) mass extinction event at 65.5 Ma is now widely believed to be triggered by a meteoritic impact, but the actual mechanism of the extinctions caused by the impact remains highly controversial. The global marine plankton record, which provides important clues for understanding the extinction mechanisms, indicates that planktonic foraminifera in near-surface ocean suffered severe declines, in contrast to the relatively high survival rates of benthic foraminifera. No extinction mechanism proposed thus far can account for this globally observed marine extinction pattern. Here, we show that sulfur trioxide-rich impact vapor was released during the K–Pg impact and resulted in the sudden onset of globally extensive acid rainfall and severe ocean acidification. Our results are based on data from impact experiments at velocities (>10 km/s) much greater than those used in previous experiments and theoretical calculations on aerosol coagulation processes. Sudden severe ocean acidification can account for many geologic records at the K–Pg boundary, including the severe extinction of planktonic foraminifera. This extinction mechanism requires impact degassing of sulfate, which is not necessarily found at impact sites other than Chicxulub, suggesting that the degree of mass extinction was controlled greatly by target lithology.