Skip to main content

Chemung Formation (redefined as Foreknobs Formation)

Chemung Formation - Shale and sandstone with a few thin, quartz-pebble conglomerates and red-beds.
State Virginia
Name Chemung Formation (redefined as Foreknobs Formation)
Geologic age Devonian
Comments Appalachian Plateaus and Valley and Ridge. From expanded explanation (ref. VA002): 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).
Primary rock type shale
Secondary rock type sandstone
Other rock types conglomerate
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone > Shale
Sedimentary > Clastic > Sandstone
Minor
Sedimentary > Clastic > Conglomerate
Map references
Digital Representation of the 1993 Geologic Map of Virginia", 2003, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, viewing software not included. This is a digital version of "Geologic Map of Virginia" published in 1993. Available from: https://www.dmme.virginia.gov/commerce/
Unit references
Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000
Digital Representation of the 1993 Geologic Map of Virginia - expanded explanation: 2003, Commonwealth of Virginia, Department of Mines, Minerals, and Energy, Divsion of Mineral Resources, Publication 147, 85 pp
Digital Representation of the 1993 Geologic Map of Virginia", 2003, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, viewing software not included. This is a digital version of "Geologic Map of Virginia" published in 1993. Available from: https://www.dmme.virginia.gov/commerce/
Counties Alleghany - Bath - Bland - Botetourt - Craig - Frederick - Highland - Lee - Montgomery - Pulaski - Roanoke - Rockbridge - Rockingham - Shenandoah - Smyth - Washington - Wythe