Metamorphosed Siltstone

Medium-gray to dark-greenish-gray phyllite, slate, and biotite schist containing minor chert and amphibolite. Locally intruded by thin metagabbro sills. Thickness 1,000-3,000 ft (305-914 m).
State South Dakota
Name Metamorphosed Siltstone
Geologic age Early Proterozoic
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > Slate
Metamorphic > Schist > Mica-schist > Biotite-schist
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Minor
Metamorphic > Amphibolite
Sedimentary > Chemical > Chert (Bed)
Metamorphic > Metaigneous > Metaintrusive > Metagabbro
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
Counties Lawrence - Pennington