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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).
StateSouth Dakota
NameMetamorphosed Siltstone
Geologic ageProterozoic | Paleoproterozoic
Original map labelXsi
Primary rock typephyllite
Secondary rock typeslate
Other rock typesschist; chert; amphibolite; gabbro
Lithologic constituents
Major
Metamorphic > Schist
Metamorphic > Metasedimentary > Metaclastic > Slate
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Minor
Igneous > Plutonic > Gabbroic > Gabbro (Dike or sill)
Metamorphic > Amphibolite
Sedimentary > Chemical > Chert (Bed)
Map 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
Unit 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
Geographic coverageLawrence - Pennington

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