James C. Zachos

Uses the geochemistry of fossils and sediments to reconstruct the climatic, chemical, and biological evolution of Cretaceous and Cenozoic oceans. Studies shifts in ocean temperature, the carbon cycle, and ice-volume, focusing on episodes of dramatic change in both warm and cool intervals in earth history. Established the relationship between ocean temperature and carbon chemistry over the past 65 million years. Evaluated the effects of past rapid infusions of CO[sub]2 into the ocean-atmosphere system, notably rapid warming and acidification of the oceans, as well as the cooling associated with a reduction of CO₂ that preceded the formation of the Antarctic ice sheet. Produced high resolution geochemical histories, and correlated them with orbital variations to understand how orbital parameters drive changes in biogeochemical cycles and climate.