Older Dryas

The Older Dryas^[a] was a stadial (cold) period between the Bølling and Allerød interstadials (warmer phases),^[1] about 14,000 years Before Present, towards the end of the Pleistocene. Its date range is not well defined, with estimates varying by 400 years, but its duration is agreed to have been around two centuries.

The gradual warming since the Last Glacial Maximum (27,000 to 24,000 years BP) has been interrupted by two cold spells: the Older Dryas and the Younger Dryas (c. 12,900–11,650 BP). In northern Scotland, the glaciers were thicker and deeper during the Older Dryas than the succeeding Younger Dryas, and there is no evidence of human occupation of Britain.^[2] In Northwestern Europe there was also an earlier Oldest Dryas (18.5–17 ka BP 15–14 ka BP).^[3] The Dryas are named after an indicator genus, the Arctic and Alpine plant Dryas octopetala, the remains 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,^[4] dependent on latitude. In regions in which it is not observed, the Bølling–Allerød is considered a single interstadial period. Evidence of the Older Dryas is strongest in northern Eurasia, particularly part of Northern Europe, roughly equivalent to Pollen zone Ic.

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^ Björck, Svante (6 January 2010). "Bio- and chronostratigraphic significance of the Older Dryas Chronozone — on the basis of new radiocarbon dates". Geologiska Föreningen i Stockholm Förhandlingar. 106 (1): 81–91. doi:10.1080/11035898409454612. Retrieved 15 April 2023.
^ Pettit, Paul; White, Mark (2012). The British Palaeolithic: Human Societies at the Edge of the Pleistocene World. Abingdon, UK: Routledge. pp. 374 477. ISBN 978-0-415-67455-3.
^ Allaby, Michael (2013). Oxford Dictionary of Geology & Earth Sciences (4th ed.). Oxford University Press. p. 181. ISBN 978-0-19-965306-5.
^ Broecker, Wallace S. (20 January 2017). "Defining the Boundaries of the Late-Glacial Isotope Episodes". Quaternary Research. 38 (1): 135–138. doi:10.1016/0033-5894(92)90036-I.

[2] Björck, Svante (6 January 2010). "Bio- and chronostratigraphic significance of the Older Dryas Chronozone — on the basis of new radiocarbon dates". Geologiska Föreningen i Stockholm Förhandlingar. 106 (1): 81–91. doi:10.1080/11035898409454612. Retrieved 15 April 2023.

[3] Pettit, Paul; White, Mark (2012). The British Palaeolithic: Human Societies at the Edge of the Pleistocene World. Abingdon, UK: Routledge. pp. 374 477. ISBN 978-0-415-67455-3.

[4] Allaby, Michael (2013). Oxford Dictionary of Geology & Earth Sciences (4th ed.). Oxford University Press. p. 181. ISBN 978-0-19-965306-5.

[WallaceBroeckerDefiningBoundariesLateGlacialIsotopeEpisodes-5] Broecker, Wallace S. (20 January 2017). "Defining the Boundaries of the Late-Glacial Isotope Episodes". Quaternary Research. 38 (1): 135–138. doi:10.1016/0033-5894(92)90036-I.

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