Figure 6    A generalized late Quaternary varnish microstratigraphy and its tentative correlation with the SPECMAP oxygen isotope record. Evidence from this and other studies (Liu, 2003; Liu and Broecker, 2007) indicates that wet events represented by dark layers (WP0-WP20) in the varnish record most likely correlate with cold periods represented by oxygen isotopic troughs in the SPECMAP record during the past three glacial-interglacial cycles (i.e., 0-300 ka). The SPECMAP chronology is from Imbrie et al. (1984) and Martinson et al. (1987). Age assignments for dark layers WP0 - WP6 are from Liu (2003) (see Fig. 3), and those for WP7 - WP20 are largely based on the tentative correlation of the varnish record with the SPECMAP record (also see Fig. 7). The shorthand arrows identify cold periods (represented by substage isotopic troughs in the SPECMAP record) that likely correlate with dark layers within each layering unit. The color scheme represents relative concentrations of Mn and Ba in varnish microstratigraphy (see Fig. 3 for explanation). H = Heinrich event, LU = layering unit, MIS = marine isotope stage, WH = wet event in Holocene, WP = wet event in Pleistocene, YD = Younger Dryas.