Metarhyolite and Aasociated Pyroclastic Sediments

Metarhyolite - Dense, blue, cryptocrystalline, with white feldspar phenocrysts and glassy quartz; red porphyritic metarhyolite at contact with Catoctin Metabasalt; and Pyroclastic sediments - tuff breccia, blue slaty tuff, white tuffaceous sericitic schist, and banded green slate.
State Maryland
Name Metarhyolite and Aasociated Pyroclastic Sediments
Geologic age Late Precambrian
Lithologic constituents
Major
Metamorphic > Metaigneous > Metavolcanic > MetarhyoliteDense, blue, cryptocrystalline, with white feldspar phenocrysts and glassy quartz; red porphyritic metarhyolite at contact with Catoctin Metabasalt
Minor
Metamorphic > Metasedimentary > Metaclastic > Slatebanded green slate
Metamorphic > Schist > Mica-schistwhite tuffaceous sericitic schist
References

Cleaves, E.T., Edwards, J., Jr., and Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.

In 1995 the Water Resources Division of the U.S. Geological Survey digitized the geologic map of Maryland from the 1968 paper map (Reference MD001). Information about products from the Maryland Geological Survey can be found at http://www.mgs.md.gov/.

NGMDB product
Counties Frederick - Washington