Figure 7    Tentative correlation of dark layers WP0 - WP20 in the varnish record with the oxygen isotopic troughs in the deep sea sediment records of SPECMAP (blue line, right ordinate; Imbrie et al., 1984; Martinson et al., 1987) and ODP 980 (green line, left ordinate; McManus et al., 1999). Previous studies (Liu et al., 2000; Liu, 2003) have shown that such correlation exists for dark layers WP0 - WP6, as illustrated in Fig. 3. By the same token, similar correlation likely exists for dark layers WP7 - WP20, as depicted in this figure. The shorthand arrows denote the climatic correlation-based ages for the upper boundaries of these dark layers in Fig. 6. Vertical bars represent the marine isotope stage (MIS) boundaries.