Surface-water acidification and extinction at the Cretaceous-Tertiary boundary

• Published in: Geology (Boulder) 1994-11, Vol.22 (11), p.983-986
• Main Authors: D'Hondt, Steven, Pilson, Michael E. Q, Sigurdsson, Haraldur, Hanson, Jr, Carey, Steven
• Format: Article
• Language: English
• Subjects: Acid rain; acidification; atmospheric precipitation; buffers; Cenozoic; Cretaceous; Endangered & extinct species; geochemistry; Geology; inorganic acids; K-T boundary; lower Paleocene; Marine; mass extinctions; Mesozoic; nitric acid; nitrous oxide; paleo-oceanography; paleoatmosphere; Paleocene; paleoecology; Paleogene; paleohydrology; Prehistoric era; rain; stratigraphic boundary; Stratigraphy; sulfur dioxide; sulfuric acid; Tertiary; theoretical studies; Upper Cretaceous
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/0091-7613(1994)022<0983:SWAAEA>2.3.CO;2

If published estimates of SO2 volatilization and NOx generation by the Cretaceous-Tertiary (K-T) impact were atmospherically converted to sulfuric and nitric acid, globally dispersed, and rapidly rained out, the resulting acid concentrations would bracket a critical threshold in surface-ocean chemistry. Rapid and globally uniform deposition of masses corresponding to the lowest estimates would have had no major effect on sea-surface chemistry. However, similar deposition of masses corresponding to the highest estimates would have provided enough acid to destroy the carbonate-buffering capacity of the upper 100 m of the world ocean and catastrophically reduce surface-ocean pH. Despite the possible effect of the highest estimated acid yields, scenarios that rely on acid rain as the primary explanation of global K-T extinctions are not readily compatible with K-T records of terrestrial and marine survival or culturing studies of modern marine plankton. The possibility that acid rain was a primary cause of K-T extinctions can be tested further by analysis of geographic variation in extinction intensity, because such variation was a likely consequence if the impact resulted in global dispersal and rapid globally uniform deposition of more than ∼6 × 1016 mol of H2SO4 or 1.2 × 1017 mol of HNO3.