Figure F10. A composite of the Cibicidoides spp. stable carbon and oxygen isotope records for Sites 522, 744, and 689 plotted as a function of age for the period from 31 to 35 Ma (Zachos et al., 1996; Diester-Haass and Zahn, 1996). The earliest Oligocene Glacial Maximum (EOGM) spans the interval 33.0–33.4 Ma. The age model is based on the geomagnetic polarity timescale of Cande and Kent (1992). The lower scale shows the bottom water temperature for an ice-free world (pre-EOGM), assuming calcite formation in oxygen isotope equilibrium (Zachos et al., 1996). PDB = Peedee belemnite. S.W. = seawater, SMOW = standard mean ocean water.