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Fig. 14. Extended spectral analysis ofCEARlS stack. References are (a) spectrum of Fig. 13a, (b) raw and (e) averaged periodogram of signal section spanning the CEARIS age range (377-6 ka). Analogously, (c) and (1) depict the
raw and averaged periodogram ofCEARlS stack. In (d) the eight individual CEARIS periodograrns are stacked. The
initially narrow standard deviation band widens towards higher frequencies. The coherency spectrum (g) of reference ( e) and proxy signal (f) yields high squared coherencies not only for the basic Milankovitch periods but also
for spectral maxima near 30 kyr, 15 kyr, 13 kyr, 11.5 kyr, 10.5 kyr, and 9 kyr. Combined with the overall coincidence of
spectral patterns this identifies these CEARIS sub-Milankovitch peaks as the hypothesized combination tones.