ORIGIN OF SANDSTONE ROCK SHELTERS ON THE SOUTHERN CUMBERLAND PLATEAU IN THE VICINITY OF SEWANEE, TENNESSEE

The mode of formation of sandstone rock shelters has received limited attention to date. On the southern Cumberland Plateau in the vicinity of Sewanee, Tennessee over 200 sandstone rock shelters provide evidence for the complex geological processes responsible for the formation of such shelters. Shelters are developed within the Warren Point Sandstone and the overlying Sewanee Conglomerate, both Pennsylvanian quartz arenites of fluvial origin. Shelters are larger and more numerous within the Warren Point Sandstone. Two distinct modes of shelter formation are recorded by these units. Within the Sewanee Conglomerate shelter formation is caused primarily by the action of ground water. Here ground water moves preferentially along more permeable horizontal zones defined by quartz pebbles and extensive secondary porosity. These zones experience higher rates of erosion and when exposed in a cliff face may develop into large cavities capable of acting as shelters. Within the Warren Point Sandstone rock shelter formation is much more complex. Shelters form here by one or more of the following processes: 1) preferential erosion of intercalated layers of shale or coal at a cliff base with subsequent roof collapse; 2) erosion and undercutting of cliffs by small streams draining the plateau; and 3) preferential erosion of poorly cemented beds of sandstone at the base of a cliff, followed by roof collapse. Artifacts within the upper, smaller shelters of the Sewanee Conglomerate have been carbon-14 dated and show occupation back to 6210 +/- 40 years BP.