Mount Rogers Formation - Conglomerate, graywacke, laminated siltstone, and shale.

Graywacke conglomerate, graywacke, tuffaceous sandstone, laminated siltstone, shale, and minor greenstone and rhyolite. Most of the sedimentary rocks are volcanigenic but contain a significant detrital contribution from the underlying crystalline rocks of the Grenville-age basement.
State Virginia
Name Mount Rogers Formation - Conglomerate, graywacke, laminated siltstone, and shale.
Geologic age Proterozoic Z
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone > Graywacke
Sedimentary > Clastic > Conglomerate
Minor
Sedimentary > Clastic > Siltstone
Sedimentary > Clastic > Mudstone > Shale
Incidental
Metamorphic > Metaigneous > Greenstone
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 - Washington