Chetaslina eruptive center dacite flow (Pleistocene). Pale-red to medium-gray, massive porphyritic dacite that contains phenocrysts of plagioclase (5-10%, 1-2 mm), aligned oxyhornblende (5-10%, as long as 6 mm), and opaque minerals (trace to 1%, 1 mm) in microtrachytic groundmass of plagioclase microlites and cryptocrystalline material. * * * Hornblende from sample (loc. 36) yielded K-Ar age of 0.84+/-0.14 Ma. Thickness about 300 m, but top not exposed.
Geologic map of the Gulkana A-1 Quadrangle, south-central Alaska