Wissahickon Formation; Upper Pelitic Schist

(Formerly mapped as albite facies of Wissahickon Formation.) Albite-chlorite-muscovite-quartz schist with sporadic thin beds of laminated micaceous quartzite; coarsens from west to east; primary sedimentary structures include normal bedding, graded bedding, and soft-sediment deformational structures; apparent thickness 14,000 feet or more.
State Maryland
Name Wissahickon Formation; Upper Pelitic Schist
Geologic age Late Precambrian (?)
Lithologic constituents
Major
Metamorphic > Schist > Quartz-feldspar-schist
Incidental
Metamorphic > Metasedimentary > Metaclastic > Quartzite
Stratigraphic units Wissahickon Formation; Glenarm Series
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 Montgomery