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Baltimore Gneiss

Baltimore Gneiss - Biotite-quartz-feldspar gneiss and biotite-hornblende gneiss; amphibolite widespread but subordinate; texturally varied; granitic gneiss, veined gneiss, augen gneiss, banded gneiss, and migmatite, in places complexly intermingled; age 1,1000 m.y. * by radiogenic dating. Layered paragneiss in Baltimore City southeast of Relay Quartz Diorite.
StateMaryland
NameBaltimore Gneiss
Geologic agePrecambrian
Original map labelpCbg
Comments* Radiogenic date from Wetherill et al., 1966 (ref. MD003)
Primary rock typegranitic gneiss
Secondary rock typeamphibolite
Other rock typesparagneiss
Lithologic constituents
Major
Metamorphic > Gneissincludes granitic gneiss and paragneiss
Incidental
Metamorphic > Metasedimentary > ParagneissLayered paragneiss in Baltimore City southeast of Relay Quartz Diorite.
Metamorphic > Amphibolite
Map references
Cleaves, E.T., Edwards, J., Jr., Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.
Unit references
Cleaves, E.T., Edwards, J., Jr., Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.
Unpublished digital version of the Maryland state geologic map that was digitized by the USGS Water Resources Office in Towson, MD
Wetherill, G.W., Tilton, G.R., Davis, G.L., Hart, S.R., and Hopson, C.A., 1966, Age measurements in the Maryland Piedmont: Journal of Geophysical Research, v. 71, p. 2139-2155.
Geographic coverageBaltimore - Carroll - Harford - Howard - Baltimore

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URL: http://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=MDpCAbg;4
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