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How did the International Commission on Stratigraphy formally define the Quaternary Period in 2008?
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Cenozoic Era
Principal Cenozoic faunal migration routes and barriers.
In 2008, the International Commission on Stratigraphy (ICS) formally designated the Quaternary as the uppermost period of the Cenozoic Era, following the Paleogene and Neogene periods. This decision abandoned the previous structure that had relegated the Quaternary to an informal sub-era.1
Subsequently, in 2009, the International Union of Geological Sciences (IUGS) ratified the formal start of the Quaternary at 2,588,000 years ago. This date aligns with the beginning of the Gelasian Stage, which was also redefined as the lowermost stage of the Pleistocene Epoch. This boundary is marked by evidence of widespread ice sheet expansion across northern continents and significant climatic and oceanographic shifts.12