DEPOSITIONAL ENVIRONMENT OF LOWER PENNSYLVANIAN SEWANEE CONGLOMERATE, LOOKOUT MOUNTAIN, GEORGIA
Despite its name, these are largely composed of a pebbly conglomerate that fines upward to a medium-grained (mL) sandstone. The Sewanee Conglomerate also contains large-scale trough cross bedding, planar lamination, and lateral accretion surfaces in sets up to 4 m thick. Sigmoidal cross bedding and reactivation surfaces are also present. The Sewanee overlies the Signal Point Shale and is overlain by the Newton Shale; both contacts are sharp. At Cloudland Canyon, the channel bodies are multi-storied. In the section measured at Cloudland Canyon bedding ranges from 10 cm to 3.4 m and forms multi-storied sand bodies.
The presence of lateral accretion surfaces, trough cross bedding, and fining-upward grain size profile indicate a channelized setting with a moderately high shear stress. The presence of sigmoidal cross-stratification and reactivation surfaces are evidence of tidal influence (Shanley et al. 1992). Collectively, these features suggest deposition within tidally influenced river channels. The presence of multi-story channel bodies suggests accumulation during relatively low accommodation rates, likely as an incised valley system.