CGRG Bibliography of Canadian Geomorphology
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Author : Beaudoin, A.B.; Robinson, S.; Froese, D.G.; and Schweger, C.E.
Date : 2009.
Title : Pleistocene spruce macrofossils and pollen from the Yukon Flats: Implications for the history of spruce in Eastern Beringia.
Publication : CANQUA–CGRG Biennial Meeting. May 3-8, 2009. Simon Fraser University, Burnaby Campus, Burnaby, British Columbia.
Issue : Programme and Abstracts Volume
Page(s) : 36.
Abstract
Two hypotheses have been previously advanced to explain the post-glacial expansion of spruce in eastern Beringia. The first posits that spruce was extirpated in unglaciated eastern Beringia and subsequently migrated northwards from refugia south of the Laurentide Ice Sheet following the Last Glacial Maximum (LGM). The principal evidence adduced for this is the low levels of spruce pollen and a lack of plant macrofossils dated between ca. 25,000 and 9,400 14C yrs BP in Yukon and Alaska. The second hypothesis suggests that spruce survived the harsh cold conditions of the LGM within eastern Beringia in small scattered populations, and re-expanded during the late Pleistocene - early Holocene. This hypothesis is based on a re-interpretation of low spruce pollen percentages in eastern Beringia, genetic evidence from extant spruce populations across northwestern North America, and the assumption that inferred rates of late Pleistocene and early Holocene plant migration from southern refugia are unrealistic. We examined eight paleosols and their associated plant macrofossils and pollen within eolian deposits at two sites ranging from 10,700 – 6,900 14C yrs BP along the Yukon River in central Alaska. Spruce macrofossils were found within a paleosol dated at 10,710 ± 60 14C yrs BP (Beta 214272) and high spruce pollen percentages (ca. 26%) were found just above the paleosol. This is the earliest post-LGM evidence for spruce in Alaska. Comparison with other post-glacial spruce records in Alaska, Yukon Territory and the Northwest Territories suggests the existence of a northern spruce refugium during the late Wisconsinan glaciation, perhaps in northwestern Canada.
Bibliography of Canadian Geomorphology