Mount Rogers Formation - Phenocryst-poor rhyolite

Phenocryst-poor rhyolite (Whitetop Rhyolite Member and Buzzard Rock Member, Mt. Rogers volcanic center). Whitetop Rhyolite Member, phenocryst-poor, very dusky purple, high-silica, metaluminous rhyolite lava fl ows and minor tuff containing 0 to 10 percent phenocrysts of quartz and mesoperthite. Buzzard Rock Member, blackish-red, low-silica, metaluminous rhyolite lava flows containing 5 to 20 percent prominant phenocrysts of mesoperthite and plagioclase; includes minor interbedded volcaniclastic sedimentary rocks. The Buzzard Rock is a thin unit that occurs beneath the Whitetop Rhyolite Member.
State Virginia
Name Mount Rogers Formation - Phenocryst-poor rhyolite
Geologic age Proterozoic Z
Lithologic constituents
Major
Igneous > Volcanic > Felsic-volcanic > Rhyolite
Comments In Grayson, Washington, and Smyth Counties only; Blue Ridge Anticlinorium (Southwest)
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 Grayson - Smyth - Washington