Beyond the 100-kyr and 41-kyr dichotomy: ~76- and ~52-kyr signals and forbidden periodicities in Quaternary glacial cycles

Takahito Mitsui 

While the Mid-Pleistocene Transition (MPT) is often termed a shift from 41-kyr to ∼100-kyr glacial cycles, this binary perspective fails to capture the nuanced spectral evolution of Quaternary climate. Using weighted wavelet spectral analysis of benthic δ¹⁸O records, we identified previously underappreciated signals—∼52 kyr before 1.2 Ma and ∼76 kyr thereafter—marking the MPT's onset. These timescales primarily correspond to integer multiples (n) of the climatic precession period (T_p), with modulation by obliquity. We find that when Tp falls within an intermediate range (20.5–22 kyr), high eccentricity triggers deglaciation, precluding cycles of 60–65 kyr and 100–110 kyr. These findings refine the conventional dichotomy of the ‘‘41-kyr and 100-kyr worlds,’’ revealing that the pre-MPT regime—∼41-kyr but including ∼52-kyr cycles—evolved into a post-MPT sequence of quantized ∼76, ∼95, and ∼120-kyr cycles. Ultimately, our results restore precession-based pacing as a fundamental driver throughout the Quaternary, showing that glacial dynamics are consistently governed by the interplay between precession and obliquity.