Abstract The variance of the Quaternary carbonate record of core RC11-209 from the equatorial Pacific is almost twice as large as that for the Upper Miocene of DSDP site 158 from the same region. Spectral analysis of the carbonate time series shows that the Miocene record is dominated by very low frequency components with a concentration of variance near the frequency corresponding to a period of about 400 kyr. The Quaternary record is also dominated by low frequency components, but has in addition concentrations of variance (spectral peaks) at frequencies corresponding to periods near 100 and 40 kyr. Cross-spectral analysis indicates that both records are coherent with the calculated record of eccentricity of the Earth's orbit and that the Quaternary record, in addition, shows coherence with the calculated record of axial tilt. These variations in the Earth's orbital parameters can then be used to “tune” the time scales of these two records. Based on the similarity in the amount of variance in the two records near the 400 kyr period and the observed relationship between carbonate fluctuations and variations in global ice volume (as indicated by oxygen isotope measurements), it is proposed that the dominant 400 kyr cycle has been associated directly or indirectly with long-term fluctuations in the Antarctic ice cap since its formation in Mid-Miocene times. The major difference in the Quaternary carbonate spectrum lies in the marked increase in variance at frequencies associated with the 100 kyr period. This increase is thought to be linked directly or indirectly with glacial to interglacial fluctuations of the Northern Hemisphere ice sheets.