The Azimuth Project
The Bølling oscillation was a warm interstadial period? between the Oldest Dryas? and Older Dryas? stadials?, at the end of the last glacial period?. It lasted roughly from 12,650 BC to 12,000 BC.
In regions where there is no evidence for the Older Dryas?, the Bølling and Allerød are lumped into a single interstadial period, the Bølling–Allerød.