|Geologic age||Late Precambrian (?)|
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Metamorphic > Metasedimentary > Metaclastic > Slate
Metamorphic > Metasedimentary > Metaclastic > Metasiltstone
Metamorphic > Metasedimentary > Metaclastic > Metasandstone > Metagraywacke
Metamorphic > Metaigneous > Greenstone
Metamorphic > Metasedimentary > Metaclastic > Quartzite
|Comments||secondary unit description from USGS Geologic Names Lexicon (ref MD004): Based on stratigraphic interpretation, the age of the Ijamsville Phyllite is changed to Late Proterozoic(?) and Early Cambrian(?). Consists of dusky blue, grayish blue, very dusky red purple, greenish gray to pale olive phyllite and phyllonite with abundant quartz veins and minor slate. Also contains aphanitic to porphyritic greenstone and yellowish gray, fine- to medium-grained sericitic quartzite.|
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/.
USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/
|Counties||Carroll - Frederick - Montgomery|