Four steps are required to derive the isotopic variation from a combined sediment core log of density, P wave velocity, magnetic susceptibility, and gray value.(a) Variance-normalized and linearly detrended d18O record of N. pachyderma and variance normalized record of the combined sediment core log.(b) Combined sediment core log converted to the variance scale of d18O of N. pachyderma by linear regression.(c) Linear regression used to correlate the combined sediment core log of Figure 3b to the d18O record of Figure 3b.(d) Comparison of the combined sediment core log of Figure 3c, corrected for the linear trend of d18O and calculated on the true d18O%scale and the original d18O record of N. pachyderm.(e) Correlation coefficient determined with moving window of 50 data points (2.5 m). The offset of the window from one analysis to another is 1 data point (5 cm).