Mahantango Formation (VADma;0)

State	Virginia
Name	Mahantango Formation
Geologic age	Devonian
Original map label	Dma
Comments	Appalachian Plateaus and Valley and Ridge. From expanded explanation: Mahantango Formation (Willard, 1935). Shale, siltstone, and sandstone. Shale, gray, pale-green, and black, weathers silvery gray, silty with minor interbedded siltstones; lower contact gradational with underlying Marcellus Shale. Siltstone, greenish-gray with interbedded shale. Sandstone, greenish-gray to grayish-brown, fine-grained, fossiliferous. Spheroidal weathering common in all lithologies. Thickness ranges from 0 in southwestern Shenandoah County (Butts, 1940) to approximately 1100 feet in Frederick County (Butts and Edmundson, 1966). Southwest of Shenandoah County the Mahantango Formation is indistinguishable from the underlying Marcellus Shale. They are combined and mapped as a single unit, the Millboro Shale, from southern Shenandoah County to Southwest Virginia (Rader, 1982).
Primary rock type	sandstone
Secondary rock type	siltstone
Other rock types	shale
Lithologic constituents	Major Sedimentary > Clastic > Sandstone Minor Sedimentary > Clastic > Siltstone Sedimentary > Clastic > Mudstone > Shale
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/ [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/ [https://www.dmme.virginia.gov/commerce/]
Geographic coverage	Frederick - Shenandoah