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Geochemical evidence for the origin of late Quaternary loess in central Alaska

Canadian Journal of Earth Sciences

By:
and
DOI: 10.1139/E05-115

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Abstract

Loess is extensive in central Alaska, but there are uncertainties about its source and the direction of paleo-winds that deposited it. Both northerly and southerly winds have been inferred. The most likely sources of loess are the Tanana River (south), the Nenana River (southeast), and the Yukon River (north). Late Quaternary loess in central Alaska has immobile trace-element compositions (Cr/Sc, Th/Ta, Th/ Sc, Th/U, Eu/Eu*, GdN/YbN) that indicate derivation mostly from the Tanana River. However, other ratios (As/Sb, Zr/Hf, LaN/YbN) and quantitative modeling indicate that the Yukon River was also a source. During the last glacial period, there may have been a longer residence time of the Siberian and Canadian high-pressure cells, along with a strengthened Aleutian low-pressure cell. This would have generated regional-scale northeasterly winds and explains derivation of loess from the Yukon River. However, superim-posed upon this synoptic-scale circulation, there may have been strong, southerly katabatic winds from expanded glaciers on the northern flank of the Alaska Range. These winds could have provided eolian silt from the Tanana River. Yukon River and Tanana River sediments are highly calcareous, whereas Fairbanks-area loess is not. This suggests that carbonate leaching in loess kept ahead of sedimentation and that late Quaternary loess in central Alaska was deposited relatively slowly. ?? 2006 NRC Canada.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geochemical evidence for the origin of late Quaternary loess in central Alaska
Series title:
Canadian Journal of Earth Sciences
DOI:
10.1139/E05-115
Volume
43
Issue:
3
Year Published:
2006
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Canadian Journal of Earth Sciences
First page:
323
Last page:
337
Number of Pages:
15