Rhyolitic Intrusive Rocks (SDTr;0)

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	Major Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-rhyolite (Stock or pipe, Laccolith)
References	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	NGMDB product page for 72317
Counties	Lawrence - Meade

Rhyolitic Intrusive Rocks

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.