Seems you're closer than I was when discussing the major cycles or maximums. Included within these maximums are lesser cycles. For example, wasn't much of Canada and the northern U.S. covered in ice ~18,000 - 20,000 years ago? Found this interesting piece on my first google. Pics wouldn't transfer without doing the HTML thing, so this may post funnily ;^):
A New Theory of Glacial CyclesDoing some more snooping around...a quick summary
Spectral analysis of climate data and orbital parameters.
For many decades it has been widely accepted that the 100 kyr cycle of the ice ages is caused by changes in the eccentricity of the Earth's orbit. However this model is contradicted by high-resolution spectral and bispectral analysis of oxygen isotopes in sea-floor cores. Nonlinear models that depend on eccentricity or the envelope of the precession curve are also ruled out. We present an alternative theory: that the climate is related to changes in the Earth's orbital inclination, and to varying extraterrestrial accretion as the orbit moves in and out of the Sun's Zodiacal ring.
Spectral analysis of 600 kyrs of global climate data is shown at right. The data show a strong peak at 100 kyr (Figures a and b) that the Milankovitch theory attributes to changes in the Earth's eccentricity (Figure c). Comparison of the data (figures a and b) with the theory (figures c and d) show that the Milankovitch hypothesis does not properly account for the data. We proposed that changes previously ignored orbital parameter, the inclination of the Earth's orbit, account for the 100 kyr cycle. The spectrum of these changes, shown in Figure e, is a good match to the data. The new theory provides an excellent match to the data, solves the "Stage-11 problem," accounts for anomolous behavior seen in noctilucent clouds and He-3 data, accounts for the structure of the bispectra, and can be further tested by looking for cycles of iridium in Greenland ice. Recent measurements of He-3 in sea floor cores appear to confirm the theory.
FGS