Dark-green amphibolite, actinolite schist, and greenstone. Interflow units consists of graphitic schist, chert, and carbonate- and silicate-facies iron-formation. Thickness of individual flows 50-400 ft (244-1,524 m).
State South Dakota
Name Metabasalt
Geologic age Early Proterozoic
Lithologic constituents
Metamorphic > Metaigneous > Greenstone
Metamorphic > Amphibolite
Metamorphic > Schist > Amphibole-schistactinolite schist, graphitic schist
Sedimentary > Chemical > Chert
Sedimentary > Chemical > Banded-iron-formation (Bed)

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 Custer - Lawrence - Pennington