AGE MODEL

We assigned preliminary ages to our samples from paleomagnetic identification of the Brunhes/Matuyama Chron (81.21 mcd; Heider et al., Chap. 28, this volume) and assuming a constant sedimentation rate of ~10 cm/k.y. The complete ¹⁸O record from Site 1020 is not yet available as this is written. Data are available for isotope Stages 1.0-3.3, 5.1-6.4, 7.1-8.4, and 8.5-10.2 (A. Mix, pers. comm., 1998). Our spliced record (Fig. 3) bears a striking resemblance to ice-volume changes as inferred from SPECMAP ¹⁸O and other Brunhes Chron ¹⁸O records. We have matched our SST estimates to the SPECMAP composite (Imbrie et al., 1984), Site 677 (Shackleton et al., 1990), and to the preliminary benthic ¹⁸O record from Site 1020 (A. Mix, pers. comm., 1998). The most striking feature is the co-occurrence of maximum SST and interglacial ¹⁸O. This correlation is documented directly at Site 1020 for benthic ¹⁸O Stages 5.1-5.5 and 7.1-8.4 (A. Mix, pers. comm., 1998). Based on this relationship between warmest SST and lightest benthic ¹⁸O, we tied our warmest SSTs from Site 1020 with Site 677 interglacial ¹⁸O (Shackleton et al., 1990) at Stages 5.5, 7.0, 9.0, 11.1, 15.1, 15.3, 17.0, and 19.0. We linearly interpolated ages using the Site 677 time scale (Shackleton et al., 1990) between oxygen isotope Stages (OIS) 5.5, 7.0, 11.1, 15.1, 15.3, and 17.0 at Site 677 and the Brunhes/Matuyama boundary at Site 1020 (Fig. 5). We remind the reader that Site 677 ¹⁸O is used only because its length is similar to our alkenone record. Our references to "leads" or "lags" are speculative, but we are confident that we will observe similar phase relationships with the complete Site 1020 ¹⁸O record when it becomes available.