These isotopes have revealed that dozens of major glacial-interglacial episodes have taken place during the Quaternary.
Even more detailed records have been recovered from cores through glacial describe cold periods of the greatest duration, whereas the intervening warm periods are called interglacials.
The ICS abandoned the sub-era structure in 2008, deciding instead to formally designate the Quaternary as the uppermost period of the Cenozoic Era, following the aforementioned Paleogene and Neogene periods.
In 2009 the International Union of Geological Sciences (IUGS) officially ratified the decision to set the beginning of the Quaternary at 2,588,000 years ago, a time when rock strata show extensive evidence of widespread expansion of ice sheets over the northern continents and the beginning of an era of dramatic climatic and oceanographic change.
Continental ice sheets formed and extended into temperate latitudes numerous times in the Quaternary, but the terrestrial record of these events is somewhat incomplete.