|Name||Ijamsville Formation and Marburg Schist|
|Geologic age||Late Precambrian (?)|
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Metamorphic > Metasedimentary > Metaclastic > Metasiltstoneincludes meta-argillite
Metamorphic > Metasedimentary > Metaclastic > Metasandstone > Metagraywacke
Metamorphic > Schist > Mica-schist > Muscovite-schistmuscovite-chlorite-albite-quartz schist
Metamorphic > Metasedimentary > Metaclastic > Slate
Metamorphic > Metasedimentary > Metaclastic > Quartzite
|Comments||secondary unit description from USGS Geologic Names Lexicon (ref MD004): Marburg Schist of Jonas and Stose (1938) is here reinstated as Marburg Formation. Fisher (1978) abandoned Marburg and included its rocks within Ijamsville Phyllite. Ijamsville is distinctive purple phyllite, whereas the Marburg is a lithologically mixed unit and therefore is reinstated as a separate, mappable unit. Rank term is changed to Formation because it consists predominantly of phyllite, paragonite phyllite, muscovite phyllite, siltstone, greenstone, quartzite, and graywacke. It also now includes some rocks previously called Pleasant Grove Schist (here abandoned), because it has been determined that Pleasant Grove was composed of sheared Mather Gorge Formation, Prettyboy Schist, and Marburg Formation. Age of Marburg is changed to Late Proterozoic and Early Cambrian.|
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||Frederick - Howard - Montgomery|