Antietam and Harpers Formations, undivided (PACAah;22)

State	Pennsylvania
Name	Antietam and Harpers Formations, undivided
Geologic age	Cambrian
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > Quartzite Minor Metamorphic > Schist Metamorphic > Metasedimentary > Metaclastic > PhylliteHarpers Formation (CAh)
Comments	Secondary unit description from USGS Geologic Names lexicon (ref. PA003): Antietam sandstone is a fine-grained white sandstone, 250 feet thick, with scolithus and Early Cambrian fossils. Underlies Cambrian limestone and overlies Harper's Ferry shales [Harpers shale]. Named for exposures east of Antietam Creek, in Harpers Ferry quad. [In southeastern PA, the lithologic character of the formation changes and it is there called Antietam quartzite in some areas and Antietam schist in other areas.]. 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.
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, Miles, C.E., and Whitfield, T.G., compilers, 2001, Bedrock Geology of Pennsylvania, edition: 1.0, digital map, scale 1:250,000. USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/ https://ngmdb.usgs.gov/Geolex/search
NGMDB product	NGMDB product page for 34341
Counties	Adams - Berks - Chester - Lancaster - Montgomery - York

State

Pennsylvania

Name

Antietam and Harpers Formations, undivided

Geologic age

Cambrian

Lithologic constituents

Major

Metamorphic > Metasedimentary > Metaclastic > Quartzite

Minor

Metamorphic > Schist

Metamorphic > Metasedimentary > Metaclastic > PhylliteHarpers Formation (CAh)

Comments

Secondary unit description from USGS Geologic Names lexicon (ref. PA003): Antietam sandstone is a fine-grained white sandstone, 250 feet thick, with scolithus and Early Cambrian fossils. Underlies Cambrian limestone and overlies Harper's Ferry shales [Harpers shale]. Named for exposures east of Antietam Creek, in Harpers Ferry quad. [In southeastern PA, the lithologic character of the formation changes and it is there called Antietam quartzite in some areas and Antietam schist in other areas.]. 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.

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, Miles, C.E., and Whitfield, T.G., compilers, 2001, Bedrock Geology of Pennsylvania, edition: 1.0, digital map, scale 1:250,000.

USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/

https://ngmdb.usgs.gov/Geolex/search

NGMDB product

NGMDB product page for 34341

Counties

Adams - Berks - Chester - Lancaster - Montgomery - York