Porphyritic biotite dacite tuff. Flow-foliated glassy groundmass containing phenocrysts of plagioclase (An 66) and biotite and opaque minerals after hornblende. Some lithic fragments, which appear to have granitic textures, have clinopyroxene interiors. Some mafic grains are entirely replaced by opaque minerals. Sparse, rounded quartz phenocrysts or fragments.
Map and tables showing geochronology and whole-rock geochemistry of selected samples, Ugashik and part of Karluk quadrangles, Alaska