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The Dawson Cut Forest Bed in the Fairbanks area, Alaska, is about two million years old☆

Published online by Cambridge University Press:  20 January 2017

John A. Westgate ,
Shari J. Preece  and
Troy L. Péwé
John A. Westgate*
Affiliation:
Department of Geology, University of Toronto, Toronto, Ontario, Canada M5S 3B1
Shari J. Preece
Affiliation:
Department of Geology, University of Toronto, Toronto, Ontario, Canada M5S 3B1
Troy L. Péwé
Affiliation:
Department of Geology, University of Arizona, Tempe, AZ 85287, USA
*
*Corresponding author. Department of Geology, University of Toronto, Earth Sciences Centre, 22 Russell Street, Toronto, Ontario, M5S 3B1 Canada. Fax: +416-978-3938. Email address:[email protected] (J.A. Westgate).
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Abstract

The Dawson Cut Forest Bed lies in the lower part of thick, late Cenozoic loess deposits in the Fairbanks area. It is associated with several distal tephra beds that provide age control and offer the opportunity of its recognition elsewhere in central Alaska. EC tephra (named herein) occurs in the uppermost part of the Dawson Cut Forest Bed and its petrographic and chemical properties point to a co-magmatic relationship with PA tephra, which has not been found in direct association with the forest bed. Both tephra beds are pink and have unusually high Cl in their glass shards, which readily separates them from all other tephra beds in the Fairbanks area. They were produced by discrete eruptions, closely spaced in time. PA tephra has a glass-fission-track age of 2.02 ± 0.14 myr, indicating that the Dawson Cut Forest Bed must be about 2 million years old. The Palisades tephra (named herein) has very similar properties to these two tephra beds, suggesting that the buried forest bed just above it at the Palisades site on the Yukon River, about 250 km west of Fairbanks, correlates with the Dawson Cut Forest Bed.

Keywords

Tephra bedsGlass-fission-track datingLate CenozoicFairbanksAlaskaGold Hill LoessDawson Cut Forest Bed
Type
Research Article
Information
Quaternary Research , Volume 60 , Issue 1 , July 2003 , pp. 2 - 8
Copyright
University of Washington

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Footnotes

☆

Supplementary data associated with this article can be found at doi:10.1016/S0033-5894(03)00061-9.

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