Kentucky's Cumberland Falls is the largest waterfall in southeastern Amercia. It is located along the Cumberland River near the towns of Williamsburg and Corbin in southeastern Kentucky. Water cascades downward between ~55 to ~70 feet, depending on river level. The rocks at the falls and along the upstream & downstream riverbanks are hard, erosion-resistant beds of the Rockcastle Sandstone (a member of the Bee Rock Formation, aka Lee Formation, Lower Pennsylvanian).
Cumberland Falls (panoramic view - be sure to scroll all the way to the left). Photo provided by Mary Ellen St. John.
Cumberland Falls (looking ~SW) - these are the rapids immediately upstream from the waterfall. The rocks are fluvial quartzose sandstones and pebbly quartzose sandstones of the Rockcastle Sandstone (Lower Pennsylvanian).
Rockcastle Sandstone (looking ~SW) - cross-bedded, fluvial, quartzose sandstones floor much of the Cumberland River just upstream from Cumberland Falls. The cross beds are dipping upstream (to the left), indicating the original depositional current direction.
Rockcastle Sandstone - this unit's lithologies range from cross-bedded quartzose sandstones to pebbly sandstones to conglomeratic sandstones to conglomerates. Almost all the pebbles are composed of quartz, and are dominantly subrounded in shape. These features indicate that the Rockcastle was deposited in an ancient fluvial (river) setting.
Coal gravel bar - abundant, river-worn pebbles of Pennsylvanian-aged bituminous coal occur in gravel bars upstream from Cumberland Falls. Some geologic literature I've examined suggests these are naturally occurring. The Barren Fork Coal outcrops in the hillsides along the river here. However, the park service at Cumberland Falls doubts that the coal gravel is natural, and encourages visitors to collect samples. Regardless, this is an interesting sight. This is not an everyday river clast lithology!