HISTORY OF ATMOSPHERIC CO2: CONSTRAINTS FROM THE DEEP-SEA RECORD

The carbon chemistry of deep ocean water is quantitatively reflected in carbonate preservation and in the delta C-13 values of foraminifera. By using benthic delta C-13 ranges to estimate total dissolved CO2 and correcting for the aging effect of deep water ("back-aging") the pCO(2) of the atmosphere can be reconstructed. Data at hand are insufficient for detailed studies, but allow the calculation of an upper limit of pCO(2) for selected periods within the last 100 million years. The limit is probably near a factor of 2.5 times present atmospheric CO2 for post-Eocene time, and below a factor of 10 for the late Cretaceous.