Annandale Group - Lake Barcroft Metasandstone

Lake Barcroft Metasandstone (Drake and Lyttle, 1981). Light-greenish-gray to light-gray, medium-grained meta-arenite; and, very-light-gray, fine- to medium-grained metagraywacke. Meta-arenite beds are massive, up to 2 m thick, and probably result from sedimentary amalgamation; metagraywacke beds are regular, sharp, and flat based, containing graded and parallel-laminated intervals; thickness ranges from 10 to 15 cm. Mineralogy: (meta-arenite), quartz + epidote + plagioclase + chlorite + muscovite + magnetite; (metagraywacke), quartz + biotite + muscovite + plagioclase + garnet + epidote + magnetite. Unit is about 1200 feet thick; grades downward into Accotick schist.
State Virginia
Name Annandale Group - Lake Barcroft Metasandstone
Geologic age Proterozoic Z-Cambrian
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > Metasandstonemeta-arenite and metagraywacke
Metamorphic > Metasedimentary > Metaclastic > Metasandstone > Metagraywackemeta-arenite and metagraywacke
Comments Western Piedmont (Northern)
References

Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.

Virginia Division of Mineral Resources, 2003, Digital Representation of the 1993 Geologic Map of Virginia, Publication 174, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, scale 1:500,000.

NGMDB product
Counties Fairfax