New oxygen isotope evidence for long-term Cretaceous climatic change in the Southern Hemisphere

A new composite delta(18)O record, generated from calcareous fine-fraction and bulk sediments from the Exmouth Plateau. details long-term Cretaceous c limatic change at mid-latitudes in the Southern Hemisphere. Assessment of n ew and previously published delta(18)O data indicates that a mid-Cretaceous global climatic optimum was achieved sometime between the time of the Ceno manian-Turonian boundary and the middle Turonian, when surface-ocean paleot emperatures were the highest of the past 115 m.y. Periods of cooling and wa rming that reversed the general patterns were superimposed on long-term Apt ian-Turonian warming and Turonian-Maastrichtian cooling trends, respectivel y. Extrapolation of Southern Hemisphere paleotemperature trends to Maastric htian paleotemperature data from a low-latitude Pacific guyot implies that maximum mid-Cretaceous low-latitude paleotemperatures could have been in ex cess of 33 degrees C.