Allerød Oscillation


Allerød Oscillation

The Allerød period is a part of a temperature oscillation toward the end of the last glaciation, during which temperatures in the northern Atlantic region rose from glacial to almost present day level. The Allerød is a warm, moist Blytt-Sernander period named after a type site in Allerød municipality in Sjælland, Denmark (near Copenhagen), where deposits created during the period were first identified and published in 1901 by Hartz and Milthers. The Allerød corresponds to Pollen zone 2.

The oscillation occurred in the Bølling and Allerød periods, with a brief intermission in some regions known as the Older Dryas period. Temperatures returned to glacial levels in the succeeding Younger Dryas period. Subsequently the climate warmed and the present interglacial period started.

Dating

The start of the Allerød depends on whether an Older Dryas is present and how much time is to be allotted to the latter. A conventional date of 14,000 BP is typical. Roberts (1998) uses 13,000 BP for the end of the period.

The Greenland Oxygen isotope record shows the warming identified with the Allerød to be after about 14,100 BP and before about 12,900 BP. C-14 dates from an excavation on the shore of Lake Neuchatel, Switzerland, furnish a date of 14,000 BP, calibrated, for the start of the Allerød. Pollen cores from Berezina plain, Belarus, give 11,800-10,900 BP uncal. Various researchers have similar ranges: 12,000-11,000, 11,700-11,000, etc. They all seem to roughly concur.

The Allerød occurred during the last interstadial of the Pleistocene: the Windermere of Britain, the Woodgrange of Ireland and the Two Creeks Interval of North America. Although interstadials are defined by region, the Allerød period is not, being global in its effects; that is, the temperature and sea level rose everywhere, not just in north Europe.

Flora

During the Allerød, which foreshadowed the modern climate, mixed evergreen and deciduous forests prevailed in Eurasia, more deciduous toward the south, just as today. Birch, Aspen, spruce, pine, larch and juniper were to be found extensively, mixed with Quercus and Corylus. Poaceae was to be found in more open regions.

Fauna

Some animals hunted were the red deer, moose, horse, Irish elk and beaver. The ubiquitous brown bear was present as well.

Man

Man in north Eurasia was still in the reindeer hunting stage. A variety of Palaeolithic cultures prevailed in Europe: the Federmesser, Lyngby, Bromme, Ahrensburg and Swiderian. To the south and far east the Neolithic had already begun.

External links

* [http://www.ac.by/publications/litho/litho16.html Belarus]


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