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Preece, S.J., 1991

Tephrostratigraphy of the late Cenozoic Gold Hill Loess, Fairbanks area, Alaska

Bibliographic Reference

Preece, S.J., 1991, Tephrostratigraphy of the late Cenozoic Gold Hill Loess, Fairbanks area, Alaska: Toronto, Ontario, Canada, University of Toronto, M.S. thesis, 164 p., illust.


Late Cenozoic loess blankets much of the Fairbanks region of interior Alaska, preserving a rich palaeoenvironmental record. Gold Hill Loess is the pre-Sangamon part of the loess cover in the Fairbanks area. Twenty distinctive tephra beds have been characterized by stratigraphy, petrography, and glass major-/trace-element geochemistry. Five tephra beds are correlated by cluster analysis of major and trace elements supported by stratigraphy and petrography. Two tephra beds are also found in other areas of Alaska and in the Yukon Territory. Tephra compositions range from andesite to rhyolite and many have bimodal compositions. Type I tephra are tholeiitic and calcalkaline, two-pyroxene andesites to rhyolites and have fractionated trace elements. Type II are calcalkaline, hornblende-orthopyroxene rhyolites with relatively unfractionated trace elements. Type III is represented by one biotite, calcalkaline, fractionated rhyolite. Source vents are located in the Aleutian Arc, Alaskan Peninsula, and the Wrangell Volcanic Field. Type II vents are rare and appear to be constrained to the continental portions of the Alaska Peninsula. Type I vents are found throughout the source regions and Type III rocks are known only from dikes at Recheshnoi Volcano.

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