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WEATHER
Rhyolitic Intrusive Rocks (SDTr;0)
Geologic Formation
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Geologic Age
Paleocene – Eocene (66 Ma – 33.9 Ma ago)
Geologic Unit Label
Tr
Light-tan to light-gray stocks and small laccoliths of rhyolite. Contains phenocrysts of oligoclase, quartz, and biotite in a finely crystalline orthoclase or sanidine-quartz groundmass.
—
USGS
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Geologic Formation
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