The age model is derived from comparison of the 18O stratigraphy (Cibicidoides wuellerstorfi) with that of the reference record from ODP Site 607 (Raymo et al., 1992, updated by Bickert et al., 1997) (see Vidal et al., submitted, this volume [N2]). Glacial/interglacial periods (on Fig. F2 as gray/white bands, respectively) were derived from the midpoint between peaks and troughs in 18O following the procedure of Tiedemann et al. (1994) and provide the basis for interpretation in this study. The 18O curve indicates a significant trend toward glacial conditions at ~2.54 Ma. This corresponds to the INHG and associated increase in ice sheet volume in North America (e.g., by Maslin et al., 1995; 1998; Shackleton et al., 1984; 1995; Tiedemann et al., 1994).