Oldest Dryas

The Oldest Dryas^[a] is a biostratigraphic subdivision layer corresponding to a relatively abrupt climatic cooling event, or stadial, which occurred during the last glacial retreat.^[1]^[2] The time period to which the layer corresponds is poorly defined and varies between regions,^[1] but it is generally dated as starting at 18.5–17 thousand years (ka) before present (BP) and ending 15–14 ka BP.^[3]^[4]^[5]^[6]^[7] As with the Younger and Older Dryas events, the stratigraphic layer is marked by abundance of the pollen and other remains of Dryas octopetala, an indicator species that colonizes arctic-alpine regions.

In the Alps, the Oldest Dryas corresponds to the Gschnitz stadial of the Würm glaciation. The term was originally defined specifically for terrestrial records in the region of Scandinavia, but has come to be used both for ice core stratigraphy in areas across the world, and to refer to the time period itself and its associated temporary reversal of the glacial retreat.^[1]

Flora

During the Oldest Dryas, Europe was treeless and similar to the Arctic tundra, but much drier and grassier than the modern tundra. It contained shrubs and herbaceous plants such as the following:

Poaceae, grasses
Artemisia
Betula nana, dwarf birch
Salix retusa, dwarf willow
Dryas octopetala

Grassland (Inner Mongolia)
Artemisia vulgaris
Betula nana
Dryas octopetala

Fauna

Species were mainly Arctic but during the Glacial Maximum, the warmer weather species had withdrawn into refugia and began to repopulate Europe in the Oldest Dryas.

The brown bear, Ursus arctos, was among the first to arrive in the north. Genetic studies indicate North European brown bears came from a refugium in the Carpathians of Moldavia. Other refugia were in Italy, Spain and Greece.

The bears would not have returned north except in pursuit of food. The tundra must already have been well populated. It is likely that the species hunted by humans at Lake Neuchâtel in Switzerland by the end of the period were present during it. Here are other animals present:

Aves

Gavia arctica, black-throated diver
Podiceps nigricollis, black-necked grebe
Cygnus cygnus, whooper swan
Aquila chrysaetos, golden eagle

Gavia arctica
Podiceps nigricollis
Cygnus cygnus
Aquila chrysaetos

The above birds are primarily maritime. They must have fed in the copious glacial waters of the north that were just beginning to be released.

Fish

Lota lota, burbot
Thymallus thymallus, grayling
Rutilus rutilus, roach
Salmo trutta, trout
Salvelinus alpinus, char

Glacial stream
Lota lota
Salmo trutta
Salvelinus

The smaller mammals of the food chain inhabited the herbaceous blanket of the tundra:

Cricetidae

Discrotonyx torquatus, collared lemming
Microtus oeconomus, root vole
Microtus arvalis, common vole
Chionmys nivalis, snowy vole

Leporidae

Lepus timidus, Arctic hare

Sciuridae

Marmota marmota, marmot

Microtus oeconomus
Microtus arvalis
Lepus timidus
Marmota marmota

In addition to bears and birds were other predators of the following small animals:

Carnivora

Felis lynx, lynx
Alopex lagopus, Arctic fox
Canis lupus, wolf

Lynx (or Felis) lynx
Alopex lagopus
Canis lupus
Icelandic horse, perhaps like Equus ferus

Humans were interested in the large mammals, which included:

Rangifer tarandus, reindeer
Equus ferus, wild horse
Capra ibex, ibex

At some point, the larger mammals arrived: hyena, woolly rhinoceros, cave bear and mammoth.

Rangifer tarandus
Capra ibex
Woolly rhinoceros
Mammoth

Notes

^ A widely-employed nomenclature for climatic change during the last glacial termination is the sequence Oldest Dryas (stadial), Bølling oscillation, Older Dryas (relatively cool), Allerød oscillation, and Younger Dryas (stadial).

References

^ ^a ^b ^c Rasmussen, Sune O.; Bigler, Matthias; Blockley, Simon P.; Blunier, Thomas; Buchardt, Susanne L.; Clausen, Henrik B.; Cvijanovic, Ivana; Dahl-Jensen, Dorthe; Johnsen, Sigfus J.; Fischer, Hubertus; Gkinis, Vasileios; Guillevic, Myriam; Hoek, Wim Z.; Lowe, J. John; Pedro, Joel B.; Popp, Trevor; Seierstad, Inger K.; Steffensen, Jørgen Peder; Svensson, Anders M.; Vallelonga, Paul; Vinther, Bo M.; Walker, Mike J.C.; Wheatley, Joe J.; Winstrup, Mai (December 2014). "A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy". Quaternary Science Reviews. 106. Amsterdam: Elsevier: 14–28. Bibcode:2014QSRv..106...14R. doi:10.1016/j.quascirev.2014.09.007.
^ Hoek, Wim (2009). "Bølling-Allerød Interstadial". In Gornitz, Vivien (ed.). Encyclopedia of Paleoclimatology and Ancient Environments. Dordrecht: Springer. ISBN 978-1-4020-4551-6. Retrieved 15 January 2021.
^ Carlson, Anders E.; Winsor, Kelsey (26 August 2012). "Northern Hemisphere ice-sheet responses to past climate warming" (PDF). Nature Geoscience. 5 (9). London: Nature Portfolio: 607–613. Bibcode:2012NatGe...5..607C. doi:10.1038/NGEO1528. Retrieved 5 July 2019.
^ Clark, P. U.; Shakun, J. D.; Baker, P. A.; Bartlein, P. J.; Brewer, S.; Brook, E.; Carlson, A. E.; Cheng, H.; Kaufman, D. S.; Liu, Z.; Marchitto, T. M.; Mix, A. C.; Morrill, C.; Otto-Bliesner, B. L.; Pahnke, K.; Russell, J. M.; Whitlock, C.; Adkins, J. F.; Blois, J. L.; Clark, J.; Colman, S. M.; Curry, W. B.; Flower, B. P.; He, F.; Johnson, T. C.; Lynch-Stieglitz, J.; Markgraf, V.; McManus, J.; Mitrovica, J. X.; Moreno, P. I.; Williams, J. W. (13 February 2012). "Global climate evolution during the last deglaciation" (PDF). Proceedings of the National Academy of Sciences. 109 (19). Washington: National Academy of Sciences: E1134–E1142. doi:10.1073/pnas.1116619109. PMC 3358890. PMID 22331892. Retrieved 5 December 2019.
^ Roberts, Neil (2014). The Holocene: an environmental history (3rd ed.). Oxford: John Wiley & sons, Ltd. p. 98. ISBN 978-1-4051-5521-2.
^ Shakun, Jeremy D.; Carlson, Anders E. (July 2010). "A global perspective on Last Glacial Maximum to Holocene climate change" (PDF). Quaternary Science Reviews. 29 (15–16). Amsterdam: Elsevier: 1801–1816. Bibcode:2010QSRv...29.1801S. doi:10.1016/j.quascirev.2010.03.016. Retrieved 5 July 2019.
^ Zheng, Yanhong; Pancost, Richard D.; Liu, Xiaodong; Wang, Zhangzhang; Naafs, B.D.A.; Xie, Xiaoxun; Liu, Zhao; Yu, Xuefeng; Yang, Huan (2 October 2017). "Atmospheric connections with the North Atlantic enhanced the deglacial warming in northeast China". Geology. 45 (11). Boulder: Geological Society of America: 1031–1034. Bibcode:2017Geo....45.1031Z. doi:10.1130/G39401.1.

External links

[1] A widely-employed nomenclature for climatic change during the last glacial termination is the sequence Oldest Dryas (stadial), Bølling oscillation, Older Dryas (relatively cool), Allerød oscillation, and Younger Dryas (stadial).

[RasmETAL2014-2] Rasmussen, Sune O.; Bigler, Matthias; Blockley, Simon P.; Blunier, Thomas; Buchardt, Susanne L.; Clausen, Henrik B.; Cvijanovic, Ivana; Dahl-Jensen, Dorthe; Johnsen, Sigfus J.; Fischer, Hubertus; Gkinis, Vasileios; Guillevic, Myriam; Hoek, Wim Z.; Lowe, J. John; Pedro, Joel B.; Popp, Trevor; Seierstad, Inger K.; Steffensen, Jørgen Peder; Svensson, Anders M.; Vallelonga, Paul; Vinther, Bo M.; Walker, Mike J.C.; Wheatley, Joe J.; Winstrup, Mai (December 2014). "A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy". Quaternary Science Reviews. 106. Amsterdam: Elsevier: 14–28. Bibcode:2014QSRv..106...14R. doi:10.1016/j.quascirev.2014.09.007.

[HoekEnc2009-3] Hoek, Wim (2009). "Bølling-Allerød Interstadial". In Gornitz, Vivien (ed.). Encyclopedia of Paleoclimatology and Ancient Environments. Dordrecht: Springer. ISBN 978-1-4020-4551-6. Retrieved 15 January 2021.

[CarlsonWinsor2012-4] Carlson, Anders E.; Winsor, Kelsey (26 August 2012). "Northern Hemisphere ice-sheet responses to past climate warming" (PDF). Nature Geoscience. 5 (9). London: Nature Portfolio: 607–613. Bibcode:2012NatGe...5..607C. doi:10.1038/NGEO1528. Retrieved 5 July 2019.

[CalTechPNAS2012-5] Clark, P. U.; Shakun, J. D.; Baker, P. A.; Bartlein, P. J.; Brewer, S.; Brook, E.; Carlson, A. E.; Cheng, H.; Kaufman, D. S.; Liu, Z.; Marchitto, T. M.; Mix, A. C.; Morrill, C.; Otto-Bliesner, B. L.; Pahnke, K.; Russell, J. M.; Whitlock, C.; Adkins, J. F.; Blois, J. L.; Clark, J.; Colman, S. M.; Curry, W. B.; Flower, B. P.; He, F.; Johnson, T. C.; Lynch-Stieglitz, J.; Markgraf, V.; McManus, J.; Mitrovica, J. X.; Moreno, P. I.; Williams, J. W. (13 February 2012). "Global climate evolution during the last deglaciation" (PDF). Proceedings of the National Academy of Sciences. 109 (19). Washington: National Academy of Sciences: E1134–E1142. doi:10.1073/pnas.1116619109. PMC 3358890. PMID 22331892. Retrieved 5 December 2019.

[Roberts_2014-6] Roberts, Neil (2014). The Holocene: an environmental history (3rd ed.). Oxford: John Wiley & sons, Ltd. p. 98. ISBN 978-1-4051-5521-2.

[ShakunCarlson2010-7] Shakun, Jeremy D.; Carlson, Anders E. (July 2010). "A global perspective on Last Glacial Maximum to Holocene climate change" (PDF). Quaternary Science Reviews. 29 (15–16). Amsterdam: Elsevier: 1801–1816. Bibcode:2010QSRv...29.1801S. doi:10.1016/j.quascirev.2010.03.016. Retrieved 5 July 2019.

[8] Zheng, Yanhong; Pancost, Richard D.; Liu, Xiaodong; Wang, Zhangzhang; Naafs, B.D.A.; Xie, Xiaoxun; Liu, Zhao; Yu, Xuefeng; Yang, Huan (2 October 2017). "Atmospheric connections with the North Atlantic enhanced the deglacial warming in northeast China". Geology. 45 (11). Boulder: Geological Society of America: 1031–1034. Bibcode:2017Geo....45.1031Z. doi:10.1130/G39401.1.

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