Age of Tephra Beds at the Ocean Point Dinosaur Locality, North Slope, Alaska, Based on K-Ar and (40)Ar/39Ar Analyses (Chapter C).

摘要

Tephra layers exposed above and below dinosaur-bone-bearing beds of the Prince Creek Formation, North Slope, Alaska, provide an opportunity to date these beds by radiometric methods. Although the tephra layers contain few or no potassium-bearing minerals, they are composed of apparently unaltered glass shards that appear to be suitable for K-Ar dating. (40)Ar/(39)Ar incremental-heating analyses were conducted in order to evaluate the accuracy of the K-Ar ages, and these analyses indicate that most of the tephra layers have undergone only minor argon loss. Most of the K-Ar and (40)Ar/(39)Ar ages are analytically indistinguishable and indicate that the bone-bearing beds are between 68 and 71 Ma. The dinosaur-bone-bearing beds of the Prince Creek Formation therefore appear to be of latest Cretaceous age.