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Pocahontas Formation

Pocahontas Formation - Sandstone, siltstone, shale, and coal.
StateVirginia
NamePocahontas Formation
Geologic agePennsylvanian
Original map label@p
CommentsAppalachian Plateaus and Valley and Ridge From expanded explanation: Pocahontas Formation (Campbell, 1896; also mapped with Pz and Pl ). Sandstone, siltstone, shale, underclay, and coal. Sandstone, feldspathic, micaceous, dark and light lithic fragments, pale-orange, light-brownish-gray, and medium to dark-gray, very-fine- to medium-grained, fine- to coarse-grained in northern outcrop area, thin- to thick-bedded and massive, sparsely cross-bedded, ripple-marked, with local shale interbeds and dark laminations; contains well-rounded quartz pebbles as much as 1 inch in diameter, locally in channel-fill deposits and basal beds; thin-bedded sandstone contains shale interbeds, shale fragments, ironstone nodules, coal debris, and sparse plant fossils. Few quartzose sandstones commonly interbedded with thin, dark-gray shales and siltstones in subsurface in Buchanan, Dickenson, and Wise counties (Miller, 1974). Sandstone comprises 70 per cent of formation (Englund,1979). Siltstone and shale, medium- to dark-gray, laminated, even- to irregulary bedded, fissile to fl ggy, fossiliferous with fresh and brackish water animal and plant fossils (Englund, 1979). Coal, finely cleated. Underclay, medium-gray, clayey to silty, contains root casts. Basal part gradational to intertonguing with underlying Bluestone Formation of the Pennington Group; base placed at top of red, green, or gray calcareous, marine shales of the underlying Bluestone Formation (Miller, 1974). The Pocahontas wedges out in the subsurface in the northwestern parts of Lee, Wise, Dickenson, and Buchanan Counties (Englund, 1979; Miller, 1974) and is thickest in western and northern Tazewell County. It ranges from 0 to 970 feet in thickness.
Primary rock typesandstone
Secondary rock typesiltstone
Other rock typesshale; coal
Lithologic constituents
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", 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/
Geographic coverageTazewell

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