Rhyolitic Intrusive Rocks

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.
State South Dakota
Name Rhyolitic Intrusive Rocks
Geologic age Eocene to Paleocene
Lithologic constituents
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-rhyolite (Stock or pipe, Laccolith)

Martin, J.E., Sawyer, J.F., Fahrenbach, M.D., Tomhave, D.W., and Schulz, L.D., 2004, Geologic Map of South Dakota: South Dakota Geological Survey, GM 10, scale 1:500,000.

NGMDB product
Counties Lawrence - Meade