There have been five significant glaciations (ice ages) during Earth’s history. During each ice age there were major advances (glacials) and major retreats (interglacials) of the ice. Within each glacial there were cooler periods (stadials) succeeded by warmer periods (interstadials).
The sequence of these periods during the most recent ice age, the Quaternary, has been correlated with data drawn from deep sea core samples. Marine isotope stages (MIS) having high levels of oxygen-18 relate to cold stages (designated by even numbers), and low levels relate to warmer stages (odd numbers).
In the Last Glacial Period (MIS 5d-1: 115-11.7 kya), the final glacial of the Pleistocene, the ice at its greatest extent during the Last Glacial Maximum (MIS 2; 27-19 kya) covered much of Asia, northern Europe and North America.
Pollen Zoning
Pollen zoning is a system of subdividing the Last Glacial Period and Holocene Period using the data from pollen cores.
| PZ | Period | kya | Flora | Fauna | Age |
| – | Last Glacial Maximum | 22-19 | tundra | bison, horse, mammoth, reindeer | Upper Palaeolithic |
| Ia | Oldest Dryas | 18.0 | Late Upper Palaeolithic | ||
| Ib | Bølling | 15.5 | park tundra | bison, elk, red deer, reindeer | |
| 1c | Older Dryas | 14.0 | tundra | ||
| II | Allerød | 13.7 | tundra, park tundra, birch forest | ||
| III | Younger Dryas | 12.8 | tundra | ||
| IV | Pre-Boreal | 11.7 | taiga: birch, pine forest | auroch, elk | Mesolithic |
| pig, red deer, roe deer | |||||
| V/VI | Boreal | 10.2 | mixed forest: birch, hazel, oak, pine | ||
| VII | Atlantic | 8.33 | wildwood: mixed elm, lime, oak | Neolithic | |
| Bronze Age | |||||
| VIII | Sub-Boreal | 5.17 | mixed: oak, ash | ||
| grass | domestic animals | Iron Age | |||
| IX | Sub-Atlantic | ||||
| 2.79-0.00 | cereals, pine beech |
The Oldest Dryas is one of three Dryas stadials named after a marker species of Alpine plant, Dryas octopetala. The Bølling interstadial is named after a peat sequence discovered at Bølling Lake in central Jutland, Denmark. The Allerød stadial is named after the geologic record found in a clay pit near the town of Allerød in Zealand, Denmark. The Pre-Boreal is one of three separate rates of Boreal warming stages. The Atlantic is one of two Atlantic warming phases.
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