Climatic Conditions in the Western and Northern Cordillera During the Last Glaciation: Paleoecological Evidence
In the southern Cordillera, paleoecological evidence suggests that climate was variable, from cooler than present by up to 3°C, to possibly similar to modern during the Olympia non-glacial interval (> 59 TO 25-29 ka). The development of open subalpine parkland vegetation in lowlands after 25 ka r...
| Published in: | Géographie physique et Quaternaire |
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| Main Author: | |
| Format: | Text |
| Language: | English |
| Published: |
Les Presses de l'Université de Montréal
1991
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| Subjects: | |
| Online Access: | http://id.erudit.org/iderudit/032879ar https://doi.org/10.7202/032879ar |
| Summary: | In the southern Cordillera, paleoecological evidence suggests that climate was variable, from cooler than present by up to 3°C, to possibly similar to modern during the Olympia non-glacial interval (> 59 TO 25-29 ka). The development of open subalpine parkland vegetation in lowlands after 25 ka reflects slow cooling to glacial conditions. Assumptions about continuously cold and dry glacial conditions are tested and disputed. Between 18-19 ka, pollen, plant macrofossil and beetle evidence suggest relatively warm and moist conditions in the Fraser/Puget Lowlands. A tentative correlation can be inferred with the recently defined "Hanging Lake thermal event" around 18-22 ka in the unglaciated Yukon. Further work should be done to test this inference. Paleobotanical data suggest that increasing moisture, rather than increased cooling, was responsible for the late Vashon ice advance in the southwestern Cordillera. The controversy regarding the nature of the vegetation cover in eastern Beringia, north of the main Cordilleran ice sheet, is not yet settled, although evidence to date favours a complex mosaic of tundra and "steppe-tundra" plant communities supporting a greater diversity of grazing large mammals than exist in the area today. Dans le sud de la Cordillère, les données paléoécologiques indiquent que le climat était variable au cours de l'intervalle non glaciale d'environ 3°C que maintenant, il est devenu semblable à celui d'aujourd'hui. Le développement d'une végétation de toundra-parc subalpine dans les basses terres après 25 ka montre qu'il y eut refroidissement lent jusqu'à des températures glaciaires. Les hypothèses selon lesquelles les conditions de froid glaciaire sec ont été continues sont ici éprouvées et contestées. Ainsi, entre 18 et 19 ka, les données palynologiques, les macrofossiles de plantes et les coléoptères montrent que le climat était chaud et humide dans les basses terres de Fraser-Puget. À titre d'essai on fait la corrélation avec l'événement thermique récemment déterminé et appelé « ... |
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