High Quality Content by WIKIPEDIA articles! The Piora Oscillation was an abrupt cold and wet period in the climate history of the Holocene Epoch; it is generally dated to the period of c. 3200 to 2900 BCE. Some researchers associate the Piora Oscillation with the end of the Atlantic climate regime, and the start of the Sub-Boreal, in the Blytt-Sernander sequence of Holocene climates.