The seven fourth-order cycles occur at approximately the same frequency as the oxygen isotope warm and cold cycles. The oxygen isotope cycles are interpreted as glacial-inter-glacial cycles corresponding with relative high- and lowstands of sea level.<ref name=ch04r113 /> The clinoforms generally correlate with trends in upward enrichment in isotope values, suggesting progradation during onset of glacial climates as a consequence of lowering sea level as continental ice formed. | The seven fourth-order cycles occur at approximately the same frequency as the oxygen isotope warm and cold cycles. The oxygen isotope cycles are interpreted as glacial-inter-glacial cycles corresponding with relative high- and lowstands of sea level.<ref name=ch04r113 /> The clinoforms generally correlate with trends in upward enrichment in isotope values, suggesting progradation during onset of glacial climates as a consequence of lowering sea level as continental ice formed. |