The stratigraphy of the Pennington Formation (Upper Mississippian) and the Gizzard (Mississippian and Pennsylvanian) and Crab Orchard Mountains Groups (Lower Pennsylvanian) reflects a suite of littoral sedimentary environments which prograded west and south into the southern Cumberland Plateau of Tennessee from the central Appalachians. Because rock-stratigraphic nomenclature in southern Tennessee evolved separately from nomenclature in Kentucky and Virginia, and because stratigraphic relations are complex, different classification schemes and formational boundaries are used in different places for similar sequences of strata. In the southern Cumberland Plateau of Tennessee, distribution of Gizzard depositional environments seems to be in part tectonically controlled, with barrier sandstones along the more stable shelf and with lagoon and marsh deposits in adjacent sedimentary basins.