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How is the Gelasian Age connected to the beginning of the Quaternary Period?

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Quaternary paleogeography — Quaternary Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the Quaternary Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.

The Gelasian Age is fundamentally connected to the beginning of the Quaternary Period because its base marks the official start of both the Pleistocene Epoch and the Quaternary System.12

Prior to 2009, the beginning of the Pleistocene and the Quaternary was often associated with the Calabrian Stage, which was understood to have begun approximately 1.8 million years ago. However, in 2009, the International Union of Geological Sciences (IUGS) ratified a decision to move the base of the Quaternary and the Pleistocene to 2,588,000 years ago, making them coincident with the start of the Gelasian Stage.12

This boundary is defined by a Global Stratotype Section and Point (GSSP) located at Monte San Nicola near Gela, Sicily. This shift aligned the start of the period with significant geological evidence of widespread ice sheet expansion and major climatic and oceanographic changes.12