Chilhowee Group; Harpers Formation (MDhf;2)

State	Maryland
Name	Chilhowee Group; Harpers Formation
Geologic age	Cambrian
Original map label	hf
Comments	secondary unit description from USGS Geologic Names lexicon (ref MD005): The Harpers Formation is predominantly a dark-greenish-gray to brownish-gray, very fine-grained, laminated to massively bedded, phyllitic metasiltstone. The base of the unit is locally sharp, but is transitional with the underlying quartz-pebble conglomeratic quartzite of the upper member of the Weverton Formation. The metasiltstone is highly cleaved and bedding is obscure. Thickness of the Harpers in the mapped area is 732 meters. The Harpers Formation overlies the Weverton Formation and underlies the Antietam Quartzite. The unit is of Early Cambrian age.
Primary rock type	shale
Secondary rock type	phyllite
Other rock types	slate
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > Phyllite Sedimentary > Clastic > Mudstone > Shale Minor Metamorphic > Metasedimentary > Metaclastic > Slate
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 Unpublished digital version of the Maryland state geologic map that was digitized by the USGS Water Resources Office in Towson, MD USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Carroll - Frederick - Washington