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Paleoclimatic significance of chemical weathering in loess-derived paleosols of subarctic central Alaska

Arctic, Antarctic, and Alpine Research

By:
, , , , ,
DOI: 10.1657/1523-0430(07-022)[MUHS]2.0.CO;2

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Abstract

Chemical weathering in soils has not been studied extensively in high-latitude regions. Loess sequences with modern soils and paleosols are present in much of subarctic Alaska, and allow an assessment of present and past chemical weathering. Five sections were studied in detail in the Fairbanks, Alaska, area. Paleosols likely date to mid-Pleistocene interglacials, the last interglacial, and early-to-mid-Wisconsin interstadiale. Ratios of mobile (Na, Ca, Mg, Si) to immobile (Ti or Zr) elements indicate that modern soils and most interstadial and interglacial paleosols are characterized by significant chemical weathering. Na2O/TiO2 is lower in modern soils and most paleosols compared to parent loess, indicating depletion of plagioclase. In the clay fraction, smectite is present in Tanana and Yukon River source sediments, but is absent or poorly expressed in modern soils and paleosols, indicating depletion of this mineral also. Loss of both plagioclase and smectite is well expressed in soils and paleosols as lower SiO 2/TiO2. Carbonates are present in the river source sediments, but based on CaO/TiO2, they are depleted in soils and most paleosols (with one exception in the early-to-mid-Wisconsin period). Thus, most soil-forming intervals during past interglacial and interstadial periods in Alaska had climatic regimes that were at least as favorable to mineral weathering as today, and suggest boreal forest or acidic tundra vegetation. ?? 2008 Regents of the University of Colorado.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Paleoclimatic significance of chemical weathering in loess-derived paleosols of subarctic central Alaska
Series title:
Arctic, Antarctic, and Alpine Research
DOI:
10.1657/1523-0430(07-022)[MUHS]2.0.CO;2
Volume
40
Issue:
2
Year Published:
2008
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Arctic, Antarctic, and Alpine Research
First page:
396
Last page:
411