West Virginia Geology: Physiographic Provinces

Dividing Line

The geology of West Virginia was examined by numerous individuals in the mid and late 1700s and early 1800s, but the first comprehensive examination was by William Barton Roger, State Geologist of Virginia, from 1835 to 1841. When the West Virginia Geological and Economic Survey was established in 1897, Israel Charles White initiated a program to geologically map the entire State, county by county, at a scale of one inch to one mile. This program, from 1906 to 1939, provided maps and reports for the State that are still in use. During the late 1800s through the present, many detailed studies have been carried out that better defined the coal areas, subsurface, paleontology, oil and gas fields, depositional environments, and mineral resouces. Present investigations including geological mapping, coal studies, and stratigraphic correlations, are being done in more detail with 1:24,000-scale maps, aerial photographs, geophysics, and computers.

West Virginia is basically composed of two areas: the western two-thirds of relatively flat-lying rocks containing minable coal, and the eastern one-third comprised of folded and faulted rocks with no minable coal. The former area is the Appalachian Plateau Province and the latter is the Valley and Ridge Province and they are separated by the Allegheny Front. In the extreme eastern part of the State are the oldest rocks, and as one proceeds westward, the rocks are younger and younger (see general geologic map). More specifically, the oldest rocks in the east are very late Precambrian (the Catoctin Formation) and then a nearly complete section of the Paleozoic is exposed moving to the west (see stratigraphic column). There are no significant Mesozoic or Cenozoic rocks in the State, but overlying most formations is Quaternary alluvium.

Valley and Ridge Province The Valley and Ridge Province in the east is composed of folded and faulted rocks that range in age from late Precambrian to early Mississippian. The late Precambrian Catoctin Formation is technically in the Blue Ridge Province, but we only have limited outcrops exposed on the Blue Ridge Mountains. From the Blue Ridge Mountains westward for about 20 miles is the Great Valley. This relatively flat, agriculturally rich region is composed of complexly folded and faulted Cambrian and Ordovician limestone and dolomite with one prominent Ordovician shale (the Martinsburg Shale). The Great Valley ends at North Mountain and from here to the Allegheny Front, a distance of about 50 miles, are a series of northeast-trending mountains and valleys. The rocks in this part of the Valley and Ridge range in age from late Ordovician to early Mississippian. The valleys are primarily composed of less-resistant shale and siltstone, while the mountain ridges are mainly resistant sandstone and limestone. The structural geology of the Valley and Ridge is complex with extensive thrust faults and folds that contribute to the repetition of all the rock formations. In addition, three major allochthonous thrust sheets have displaced the surface and subsurface rocks westward in the order of 30 to 50 miles. The interested reader may wish to examine recent geological maps and reports noted in the Survey's publications list.

Appalachian Plateau Province The Appalachian Plateau Province covers the western two-thirds of the State where the rock formations are relatively flat, except for several distinct folds and faults on the eastern side of the Province. The oldest rocks are located in these eastern fold sequences and range in age from late Ordovician up through the Mississippian. The majority of the Appalachian Plateau is comprised of Pennsylvanian and Permian strata and is where all the minable coal is located. The rocks exposed in the northern part of the Plateau are younger than those exposed in the southern part. This is also reflected in the age of the minable coal seams; younger to the north and older in the south. Although some natural gas has been obtained from the Valley and Ridge Province, by far the majority of natural gas (perhaps 95 to 98 percent) and all the oil comes from the Plateau (see also the sections on coal and oil and gas on this web site). The boundary between the two provinces, the Allegheny Front, is a complex and rather abrupt change in the topography, stratigraphy, and structure. This boundary extends southwestward across the eastern part of the State, passes through Virginia, and reenters the State in the southeast in Monroe County.

(by Peter Lessing, July 1996)

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