In southeastern Tennessee, northwestern Georgia, and northeastern Alabama, the Cumberland Plateau (Walden Ridge and its southwestern extension, Sand Mountain) is underlain by a relatively small Pennsylvanian basin known as the Raccoon Mountain basin.
Stratigraphic units in this basin, of most interest to our discussion, are the uppermost Mississippian Pennington Formation and lowermost Pennsylvanian Gizzard Group (Signal Point, Warren Point, and Raccoon Mountain formations). The Mississippian-Pennsylvanian boundary (between Pennington and Raccoon Mountain) is transitional, and much of the upper part of the Pennington consists of siliciclastics.
Previous workers have suggested that Mississippian-Pennsylvanian rocks are regionally facies equivalent, with the Pennington Formation representing a shallow marine environment and the Warren Point-Raccoon Mountain formations representing marginal-marine, barrier, and back-barrier environments. This suggestion was based largely on inferences made on observed sedimentary structures, particularly the alleged occurrence of low-angle beach-face beds.
New insight, based on sedimentary structures exposed in roadcuts and stripmine highwalls throughout the Raccoon Mountain basin, has enabled reinterpretation of environments of deposition of Pennsylvanian sandstones and shales. It is suggested that most of these Lower Pennsylvanian rocks accumulated in fluvial and paludal environments.