Geodiversity Atlas—Appalachian Highlands Network Index

photo of mountain ranges and cloud filled valleys — View from Blue Ridge Parkway.
NPS image.

Geology and Stratigraphy of the Appalachian Highlands Network Parks

The Appalachian Highlands Network consists of four national park areas in Kentucky, North Carolina, Tennessee, and Virginia including: Big South Fork National River and Recreation Area, Blue Ridge Parkway, Great Smoky Mountains National Park, and Obed Wild and Scenic River. The network parks are divided between two ecologically distinct physiographic regions: the Cumberland Plateau of Kentucky and Tennessee, and the Southern Appalachian Mountains of Georgia, North Carolina, Tennessee, and Virginia. Both these regions are characterized by high levels of biological diversity and endemism (Santucci et al. 2008).

The Appalachian Mountains are one of the oldest mountain ranges in the world. The long stability of the Appalachian Mountains, combined with its great variation in geology, landforms, and climate, have supported the evolution of a rich diversity of fauna and flora, especially in the southern regions which were not directly impacted by glacial activity. Within the Southern Appalachians, the Blue Ridge Mountains (Blue Ridge Province ) rise abruptly above the rolling Piedmont to the east and form the backbone of the Appalachians in this region. The Southern Appalachians ecoregion is one of the most biologically diverse terrestrial ecosystems in the world.

To the west of the Blue Ridge Mountains are the Valley and Ridge Province and the Cumberland Plateau. The Valley and Ridge Province consists of folded and unmetamorphosed Paleozoic sedimentary rocks that include sandstones, shales, and limestones, with some Pennsylvanian-age coal beds (see geologic time scale). These sedimentary units are underlain by large thrust faults generated by intercontinental collisions during the late Paleozoic. The Cumberland Plateau is an extensive tableland of sandstone and shale carved by water into a labyrinth of rocky ridges and deep gorges. The Cumberland River system includes the Big South Fork and Obed rivers.

A Brief Geologic History—Appalachian Highlands Network

The Appalachian Mountains were significantly uplifted and deformed during the Paleozoic due to a series of orogenies that include the Taconic Orogeny (475–405 million years ago), Acadian Orogeny (390–350 million years ago), and Alleghenian Orogeny (300–245 million years ago). Paleozoic rocks occur in all four of the Appalachian Highlands Network parks. The Cambrian is represented by seven units in BLRI and seven units in GRSM. The only Cambrian unit to occur in both parks is the Shady Dolomite. Lower and Middle Ordovician units (Jonesboro Limestone and Chickamauga Group) are mapped in GRSM. The only Devonian formation occurring in any of the Appalachian Highlands Network parks is the Chattanooga Shale, which is present in Great Smoky Mountains.

The Upper Mississippian is most extensively exposed at BISO in the form of a sandstone belt of cliffs and steep-sided, narrow-crested valleys. Terrestrial Mississippian sandstones and siltstones are the result of a great influx of mud, silts, and sands brought in by rivers and streams from uplands many miles to the northeast and deposited as a great delta. The Mississippian limestones of the region were deposited 350 million years ago in the bottom of a warm, shallow sea. Mississippian rocks also occur in limited exposures in Great Smoky Mountains.

At the end of the Mississippian (approximately 320 million years ago) the seas receded and were overlain by Pennsylvanian-aged sediments. The warm climate of the Pennsylvanian allowed 5 extensive forests to grow and great coastal swamps to develop at the edges of water bodies. Marine waters advanced and receded many times, which produced many layers of sandstone, shale, and coal. Pennsylvanian-age plants were buried under blankets of sediments, which over long geologic time were compressed into coal.

At Big South Fork the Pennsylvanian rocks are predominantly sandstone and shale, and include siltstone, conglomerate, and coal. A dendritic drainage pattern resulted in narrow and V-shaped gorges. The weathering processes on these rocks have produced an impressive array of geologic features, including arches, mesas, chimneys, cracks, and rock shelters. Lower and Middle Pennsylvanian units, including sandstone, shale, conglomerate and coal, dominate the bedrock at Obed Wild & Scenic River and large portions of Big South Fork.

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Last updated: December 9, 2024

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Geodiversity Atlas—Appalachian Highlands Network Index

Geology and Stratigraphy of the Appalachian Highlands Network Parks

A Brief Geologic History—Appalachian Highlands Network

Cenozoic Era—66 Million Years Ago to Today

Mesozoic Era—252 Million to 66 Million Years Ago

Paleozoic Era—541 Million to 252 Million Years Ago

The Precambrian—4.5 Billion to 541 Million Years Ago

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