THE MISSISSIPPIAN-PENNSYLVANIAN DISCONFORMITY AT GREETER FALLS, GRUNDY COUNTY, TENNESSEE

The Mississippian-Pennsylvanian disconformity is well exposed at Greeter Falls along Piney Creek, northeast of Altamont in Grundy County, TN. The Mississippian Pennington Formation is cut by a 6 m-deep paleochannel with a steep-to-vertical edge in fossiliferous limestones. Red and green shales of the Pennington form the channel base. The eastern edge of the channel is clearly defined at the falls and appears 40 m to the south on the opposite side of the plunge pool. Above the disconformity the immature, heavily burrowed sandstones and siltstones of the Raccoon Mountain Formation of the Morrowan Gizzard Group dip roughly parallel to the channel edge and are cut by a reverse fault striking N21E and dipping 46SE.

The disconformity at Boardtree Falls 1.0 km NE of Greeter Falls exhibits very little relief. Here the extensively burrowed Raccoon Mountain sandstones, siltstones, and shales contain thin discontinuous coal seams up to 5 cm thick. Escape structures in burrows indicate rapid sedimentation. Basal sandstones in the Raccoon Mountain Formation are composed primarily of terrigenous clastics cemented by calcite and siderite, indicating deposition in proximity to a marine environment.

Thin, discontinuous beds of transported marine fossils are found in basal portions of the Raccoon Mountain Formation near Greeter Falls. These are interpreted as marine washover deposits and further demonstrate proximity to the ocean during deposition of the lower Raccoon Mountain Formation.