Appalachian Basin Geologic Mapping Project

Science Center Objects

The Appalachian Basin Geologic Mapping Project performs geologic mapping at local and regional scales, and geologic research in The Valley and Ridge and Appalachian Plateaus physiographic provinces. These provinces include parts of 11 states and mainly borders the Blue Ridge / Piedmont and North Interior Lowlands Provinces. Two states have Valley and Ridge geology only (GA, NJ), two have Appalachian Plateaus geology only (KY, OH), and seven have both provinces represented (AL, MD, PA, NY, TN, VA, and WV). The Valley and Ridge province is a fold and thrust terrain that changes to low dipping and flat lying rocks of the Appalachian Plateaus.

 

Location of the Appalachian Basin Geologic Mapping Project

Figure 1. Location of the Appalachian Basin Geologic Mapping Project. The study area comprises the Valley and Ridge and Appalachian Plateaus physiographic provinces. (USGS. Public domain.)

The Appalachian Basin extends from central Alabama to the Adirondack Mountains in New York. The Basin, which contains up to 40,000 ft of stratified rocks (Colton, 1962), underlies the Valley and Ridge and Appalachian Plateaus physiographic provinces and includes parts of 11 states (fig.1). Both of these provinces are mountainous. Two states have Valley and Ridge geology only (GA, NJ), two have Appalachian Plateaus geology only (KY, OH), and seven include parts of both provinces represented (AL, MD, PA, NY, TN, VA, and WV). The Appalachian Basin Project area adjoins, along its eastern boundary, the Blue Ridge and Piedmont Provinces which constitute the National Cooperative Geologic Mapping Program Blue Ridge and Piedmont Project and along its northern boundary the Adirondacks and New England Provinces that comprise the Northeast Bedrock Mapping Project.

 

The Valley and Ridge Province is characterized by folded and faulted Paleozoic sedimentary rocks that have eroded to form strike-parallel topographic valleys and ridges with local relief from ridge top to valley floor usually on the order of about 1000 feet (fig. 2). Elevations in the Valley and Ridge range from about 300 ft to about 4000 ft above sea level. Most ridges in the province are held up by weathering-resistant quartz-rich sandstone or conglomerates and most of the valleys are floored by softer shale and/or soluble carbonate rocks. Ages of the rocks exposed at the surface in the Valley and Ridge typically range from Cambrian through Mississippian. The Valley and Ridge hosts karst terrain in areas where carbonate rocks, chiefly of Cambrian, Ordovician, and Devonian ages are exposed. In karst areas groundwater, high biological diversity, recreation value, and tourism are potential resources.  However, these same areas have potential for karst collapse hazards and sensitivity to ground water pollution from some land use practices or spills from transportation of various materials. Rocks of the Valley and Ridge contain limited oil and gas reserves and are generally thermally over mature for oil source rocks. These strata also serve as important sources of limestone, aggregate, and glass and proppant sand. Residual ores of manganese and other metals exist and have potential for exploitable rare earth elements associated with them.

 

The Valley and Ridge Province transitions relatively abruptly to gently dipping rocks of the Appalachian Plateaus along the Allegheny structural front (fig. 2).

Folded Sandstone, Siltstone, and Shale in the Brallier Formation near Higginsville, West Virginia

Figure 2. Folded Sandstone, Siltstone, and Shale in the Brallier Formation near Higginsville, West Virginia. (Credit: Daniel H. Doctor, USGS. Public domain.)

The Appalachian Plateaus are underlain by the same Paleozoic strata as the Valley and Ridge but tends to preserve and expose younger rocks (Mississippian – Permian ages). Average local relief in the Plateaus is generally lower than that in the Valley and Ridge, usually on the order of about 500 ft, but where incised by large rivers it can be more extreme. The New River Gorge in south central West Virginia has a relief of about 1000 ft from the river to the gorge rim. Elevations range from about 500 ft where the western Province boundary crosses the Ohio river to 4862 ft at Spruce Knob, the highest point in West Virginia. The Plateaus Province contains well developed karst terrains particularly in areas underlain by the Mississippian Greenbrier Group limestones and their equivalents. The Greenbrier karst in southern West Virginia is world renowned for its well-developed karst topography and numerous large caves. The Appalachian Plateaus contain much of the coal, oil, and shale gas resources of the eastern U.S. and, like the Valley and Ridge, possesses chiefly non-metallic geologic resources.