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Wissahickon Formation

Wissahickon Formation - Includes oligoclase-mica schist, some hornblende gneiss, some augen gneiss, and some quartz-rich and feldspar-rich members due to various degrees of granitization.
State Pennsylvania
Name Wissahickon Formation
Geologic age Probably lower Paleozoic
Primary rock type mica schist
Secondary rock type mafic gneiss
Other rock types augen gneiss; granitoid
Lithologic constituents
Major
Metamorphic > Schist > Mica-schistoligoclase-mica schist
Minor
Metamorphic > Gneiss > Hornblende-gneisssome hornblende gneiss, some augen gneiss
Igneous > Plutonic > Graniticsome quartz-rich and feldspar-rich members due to various degrees of granitization.
Map references
Pennsylvania Bureau of Topographic and Geologic Survey, Department of Conservation and Natural Resources, 2001, Bedrock Geology of Pennsylvania, edition: 1.0, digital map. Retrieved from internet 9-30-2004; <http://www.dcnr.state.pa.us/topogeo/map1/bedmap.aspx> DL Data: pageoexp.zip
Unit references
Berg, T. M., Edmunds, W. E., Geyer, A. R., and others, compilers, 1980, Geologic map of Pennsylvania: Pennsylvania Geological Survey, 4th ser., Map 1, 2nd ed., 3 sheets, scale 1:250,000.
Pennsylvania Bureau of Topographic and Geologic Survey, Department of Conservation and Natural Resources, 2001, Bedrock Geology of Pennsylvania, edition: 1.0, digital map. Retrieved from internet 9-30-2004; <http://www.dcnr.state.pa.us/topogeo/map1/bedmap.aspx> DL Data: pageoexp.zip
Counties Bucks - Delaware - Montgomery - Philadelphia