Older Dryas

The Older Dryas was a stadial (cold) period between the Bølling and Allerød oscillations (warmer phases) approximately 14,000 years ago (BP), towards the end of the Pleistocene epoch. The gradual warming since the peak of the last glacial period 22,000 years BP has been interrupted by three cold spells, the Older Dryas having been preceded by the Oldest Dryas and followed by the Younger Dryas. They are named after an indicator genus, the arctic and alpine plant Dryas, the fossils of which are found in higher concentrations in deposits from colder periods.

The Older Dryas was a variable cold, dry Blytt-Sernander period, observed in climatological evidence in only some regions, depending on latitude. In regions where it is not observed, the Bølling-Allerød is considered a single interstadial (warm) period. Evidence of the Older Dryas is strongest in northern Eurasia, particularly part of North Europe roughly equivalent to Pollen zone Ic.