Isothermal plateau fission‐track age of the Late Pleistocene Old Crow Tephra, Alaska

Abstract

Hydrated glass shards of the widespread Old Crow tephra in Alaska have been dated by the isothermal plateau fission‐track method, which corrects for partial track fading, if present. The weighted mean age of 149±13 ka is older than previous estimates, which range from 86 to 109 ka. These new data support the view that Old Crow tephra was deposited during the cold interval that immediately preceded the last interglacial, which is dated in the marine record at 125 ka B.P. It is likely, therefore, that the buried forest beds and numerous ice‐wedge pseudomorphs, preserved in sediments just above Old Crow tephra in interior Alaska, relate to the last interglacial and not a younger warm event of early Wisconsin age.