Dating Early and Middle (Reid) Pleistocene Glaciations in Central Yukon by Tephrochronology

• Published in: Quaternary Research
• Main Authors: Westgate, John A., Preece, Shari J., Froese, Duane G., Walter, Robert C., Sandhu, Amanjit S., Schweger, Charles E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2001
• Subjects: Ash Bend; Dawson City; Fort Selkirk; Gulf of Alaska; Midnight Dome; Ogilvie; Ogilvie Mountains; Yukon; Dawson; glaciers; Ice Sheet; Alaska
• Online Access: http://dx.doi.org/10.1006/qres.2001.2274; http://api.elsevier.com/content/article/PII:S0033589401922744?httpAccept=text/xml; http://api.elsevier.com/content/article/PII:S0033589401922744?httpAccept=text/plain; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S003358940001036X

Abstract The late Cenozoic deposits of central Yukon contain numerous distal tephra beds, derived from vents in the Wrangell Mountains and Aleutian arc–Alaska Peninsula region. We use a few of these tephra beds to gain a better understanding on the timing of extensive Pleistocene glaciations that affected this area. Exposures at Fort Selkirk show that the Cordilleran Ice Sheet advanced close to the outer limit of glaciation about 1.5 myr ago. At the Midnight Dome Terrace, near Dawson City, exposed outwash gravel, aeolian sand, and loess, related to valley glaciers in the adjacent Ogilvie Mountains, are of the same age. Reid glacial deposits at Ash Bend on the Stewart River are older than oxygen isotope stage (OIS) 6 and likely of OIS 8 age, that is, about 250,000 yr B.P. Supporting evidence for this chronology comes from major peaks in the rates of terrigeneous sediment input into the Gulf of Alaska at 1.5 and 0.25 myr B.P.