An abrupt climate and carbon cycle perturbation occurred at the Paleocene/Eocene boundary, ~55 million years ago. The carbon cycle perturbation is illustrated here in several ocean sediment cores. The abrupt decrease in carbon isotope values implies that a large amount of 12C-enriched carbon was added to the ocean/atmosphere. The sharp lithologic change from light-colored carbonate rich sediment to red carbonate-poor sediment in three of the cores shown (1209, 527, 549) indicates acidification of ocean deep waters due to increased CO₂ content.

Figure from B.S. Cramer and D.V. Kent, Bolide summer:
the Paleocene/Eocene thermal maximum as a response to an extraterrestrial trigger, Palaeogeography, Palaeoclimatology, Palaeoecology, in press.

Submitted by Benjamin Cramer
Institute of Geology and Paleontology
Tohoku University, Aoba, Aramaki
Sendai 980-8578, Japan