Chemung Formation (redefined as Foreknobs Formation)

Chemung Formation (Hall, 1839). Redefined as the Foreknobs Formation (Dennison, 1970). Sandstone and shale, dark-gray and greenish-gray, fine-grained, thin- to thick-bedded, lithic sandstone and interbedded greenish gray, fissile, clay shale. Minor quartz-pebble conglomerate, thin red sandstone, and locally, fossil shell beds. Very thin or absent in southwestern Virginia; thickens to about 2500 feet northeastward in Frederick County. Gradational contact with underlying Brallier Formation and equivalent to part of the Chattanooga Shale to the southwest. Redefined and described as part of the Greenland Gap Group by Dennison (1970).
State Virginia
Name Chemung Formation (redefined as Foreknobs Formation)
Geologic age Devonian
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone > Shale
Sedimentary > Clastic > Sandstone
Minor
Sedimentary > Clastic > Conglomerate
Comments Appalachian Plateaus and Valley and Ridge
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 Alleghany - Augusta - Bath - Bland - Botetourt - Craig - Frederick - Highland - Lee - Montgomery - Pulaski - Roanoke - Rockbridge - Rockingham - Shenandoah - Smyth - Tazewell - Washington - Wythe