| Text Description: |
Thick lobate flows of dacite and minor rhyodacite that form massive piles along west, northwest, north, and northeast flanks of Mount Drum, apparently erupted from central vent. Rocks are light to pinkish medium gray, weather dark reddish brown, and are porphyritic with phenocrysts (1-3 mm) of plagioclase, hypersthene, hornblende, and rare to minor biotite and augite in a pilotaxitic to trachyitic groundmass. Probably related in age to late hornblende-biotite dacite domes (Qldd). |