Abstract

The Chattanooga Shale was deposited on a continental platform in central Tennessee, and in a slope/peripheral trough setting in eastern Tennessee. Careful examination of shale samples shows distinct differences between these two settings. A total of 14 shale types has been distinguished on the basis of sedimentary features, lithologic associations and small scale sedimentary sequences. Sedimentary features attributable to fine grained turbidites characterize most of the shales from eastern Tennessee. On the basis of the clay/silt ratio two types of fine grained turbidites can be distinguished. They may represent deposition in an interlobe slope (large clay/silt ratio) and lobe margin environment (small clay/silt ratio). Silt laminae produced by storm induced wave and current reworking characterize the shales of the platform region. Differences in energy levels, probably reflecting seafloor morphology, are indicated by sedimentary features of the various shale types.

Bioturbation in these shales is subtle and has been under-estimated in the past. Burrows of the platform region are more elaborate and complex than those of the trough region. Even units that lack visible signs of bioturbation contain peloids that could be fecal pellets of polychaete worms or similar surface dwellers. This observation indicates that oxygen levels in the bottom waters were not as low as previously assumed and that truly anoxic conditions were rare in the Appalachian Basin.