Mount Wrangell younger andesitic flows and dikes (Pleistocene). Flows are dark-gray, sparsely porphyritic to microporphyritic andesite that contains phenocrysts and microphenocrysts of plagioclase (5-8%, 0.1-0.5 mm), augite (1-3%, 0.1-0.3 mm), and hypersthene (trace, 0.2 mm). Dikes are mineralogically similar to flows but also contain trace to 2% fresh olivine. * * * Source of flows may be fissure that extends west from unnamed 11,610-ft (3,539-m) peak (sec. 21, T. 3 N., R. 7 E.) on west flank of Mount Wrangell. Unit may be as much as 300 m thick.
Geologic map of the Gulkana A-1 Quadrangle, south-central Alaska