- Usage in publication:
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- Old Rag granite
- Modifications:
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- Named
- Dominant lithology:
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- Granite
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Intent to name not stated. Author states that the most typical and extensive exposure of this intrusive is Old Rag Mountain. Common occurrence in Shenandoah Park, especially on the east side of the mountain. Described as coarse-grained, blue-quartz granite, resembling a facies of the Marshall granite. Composed of light gray or nearly white untwinned feldspar (orthoclase and microcline) and blue or smoky quartz. Where it occurs in large masses, it may be as coarse or coarser than the hypersthene granodiorite that it intrudes. Also intrudes Catoctin schist and is intruded by Air Point granite. Age is Precambrian.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Old Rag Granite
- Modifications:
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- Revised
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Old Rag Granite is here assigned to the Saddleback Mountain Suite, newly named in the Pedlar massif in the Blue Ridge of northern Virginia. The suite also contains a mesocharnockite facies. Age is Middle Proterozoic.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Old Rag granite
- Modifications:
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- Overview
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Unit used informally on the VA State map. Described as leucocratic, coarse-grained, foliated, alkali feldspar-blue quartz granite with accessory biotite, muscovite, garnet, magnetite, and zircon. [Virginia Blue Ridge Complex not used.]
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Old Rag Granite*
- Modifications:
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- Geochronologic dating
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Old Rag Granite is an alaskite with a U-Pb zircon upper intercept of 1115+/-2 Ma (Lukert, 1982).
Source: GNU records (USGS DDS-6; Reston GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).