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Text Description: Wrangell Lava. Older andesites, undifferentiated (Pliocene). Chiefly flat lying to gently dipping, medium to thick (3-20 m) flows, exhibiting scoriaceous tops and bottoms, and rare to locally common intercalated mudflows, breccias, and bedded tephra. Flows range from medium gray and dark gray to olive gray in color, are locally amygdaloidal and generally porphyritic containing 5-25% phenocrysts. Principal types include hypersthene andesite, and olivine andesite. * * * Whole-rock K-Ar ages of samples 81-ASj-77B (map locality 21) and 81-ASj-85 (map locality 22) are 1.99 +/- 0.08 Ma and 2.21 +/- 0.09 Ma, respectively. Thickness greater than 900 m; base not exposed. References:  Geologic map of the Nabesna B-6 Quadrangle, south-central Alaska |
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