Geology

Natural Features & Ecosystems

The Big South Fork watershed lies within the Cumberland Plateau, which is in the southern portion of the Appalachian Plateaus structural province. The geology of the Big South Fork is characterized by parallel, horizontally-bedded sedimentary rock of Pennsylvanian and Mississippian age rock. The Pennsylvanian rocks are predominantly sandstone and shale, and include siltstone, conglomerate, and coal. The weathering processes on these rocks have produced an impressive array of formations, including arches, mesas, chimneys, cracks, and rockshelters. The underlying Mississippian age limestone contains oil and gas deposits which are found both within and outside the Big South Fork.

The stream topography of the area is characterized by a dendritic drainage pattern and narrow, v-shaped gorges. A focal point of the area is the Big South Fork River gorge with its many sheer bluffs at the gorge rim towering over wooded talus slopes. The river valleys of the area are dotted with huge boulders which have broken from the cliff faces. The park's rivers and streams are characterized by stretches of fast, rugged whitewater and quiet pools.

Rivers & Streams

The Big South Fork watershed covers approximately 1,123 square miles primarily in Fentress and Scott Counties, Tennessee and McCreary County Kentucky with smaller areas of Anderson, Campbell, Morgan and Pickett Counties, Tennessee. The Big South Fork protects the lower 14% of this area with the Big South Fork River draining the Cumberland Plateau northward, flowing into Lake Cumberland. A PDF file (51kb) delinating the watershed and the lands protected by Big South Fork in each county is available for viewing.

Big South Fork waters are generally considered good quality, however, the rivers and streams which flow through the park are not without impacts nor safe from threats. Acid mine drainage, agricultural chemicals and excessive sediment from logging, substandard road construction, and other past and present ground disturbing activities significantly can affect both tributary streams and the Big South Fork River.

Tennessee and Kentucky have designated their portions of the Big South Fork River as an Outstanding National Resource Waters. Kentucky has also recognized the section of the Big South Fork from the state line to Blue Heron mine as a Kentucky Wild River.

Both Kentucky and Tennessee use stream classification systems through which they are able to protect surface water quality. Tennessee has classified all streams within the Big South Fork for primary contact recreation and fish and aquatic life. Kentucky classifies all Big South Fork streams for primary contact recreation and for either warm water or cold water aquatic habitat. Unfortunately a number of streams in the Big South Fork, in both states, do not meet these standards, primarily due to acid mine drainage and/or sedimentation.

Sandstone Arches

The Big South Fork National River and Recreation Area abounds in dramatic cliffs, arches, and rockshelters. The region may contain more natural arches that any other region in the eastern United States.

Natural arches are found frequently in the Big South Fork at the edges of the tableland surface, there the resistant Rockcastle Conglomerate slowly succumbs to erosion. Arches form along gorge edges where the resistant sandstone is able to support its own weight when layers below erode away.

Arches of varying sizes and descriptions can be found throughout the area but only a few have hiking trails leading to them. Below is a list of easily accessible arches and their general locations.

TWIN ARCHES were formed by headward erosion along a narrow ridge . The arches are considered to be the largest arches in the Big South Fork and quite possibly in the Eastern United States. They may be reached by a number of routes, the shortest being a .7 mile hike from the Twin Arches Trailhead.

NEEDLE ARCH is a thin, delicate arch that was left standing alone when the back of the rockshelter of which it was once a part eroded. It can be reached from the Sawmill Trailhead on Fork Ridge Road.

SPLIT BOW ARCH is unusual in that a narrow finger of the bluff split away from the main bluff. When large chunks of rock fell, a high, thin bridge was all that was left. You can see the arch from an overlook or hike a 0.7 loop trail that will take you through the arch. Signs at the Bear Creek Scenic Area in Kentucky (just off KY 742) will direct you to the arch.

NATURE & SCIENCE

The Big South Fork is located in north central Tennessee and southeastern Kentucky in some of the most rugged terrain of the Cumberland Plateau. The park encompasses approximately 125,000 acres of both rugged forested gorge and adjacent forested plateau. Together with the state and federal lands which share the north and western boundaries the area offers a wide variety of habitats in which plants and animals may abound.

Within the Big South Fork numerous pristine streams flow into the free-flowing Big South Fork of the Cumberland River. Over the eons, this ceaseless moving water has carved the sandstones of the plateau into the impressive cliffs, arches and chimneys found throughout the park.