Significant increases in global weathering during Oceanic Anoxic Events 1a and 2 indicated by calcium isotopes

Calcium-isotope ratios (δ44/42Ca) were measured in carbonate-rich sedimentary sections deposited during Oceanic Anoxic Events 1a (Early Aptian) and 2 (Cenomanian–Turonian). In sections from Resolution Guyot, Mid-Pacific Mountains; Coppitella, Italy; and the English Chalk at Eastbourne and South Ferriby, UK, a negative excursion in δ44/42Ca of ~ 0.20‰ and ~ 0.10‰ is observed for the two events. These δ44/42Ca excursions occur at the same...