Abstract

Previously paleocurrent data from the Chattanooga Shale and its lateral equivalents suggested deposition on a westward dipping paleoslope (westward paleoflow). However, new paleocurrent data (measurements of anisotropy of magnetic susceptibility, AMS) are not in agreement with that view. They indicate eastward flowing paleocurrents in eastern Tennessee and irregular flow in central Tennessee.

Macroscopic sedimentary features also point to significant differences in the sedimentary setting between eastern and central Tennessee. In eastern Tennessee the Chattanooga Shale intertongues with turbidites of the Brallier Formation, lacks shallow water features and may have been deposited in depths between 100-200 m. In central Tennessee HCS siltstones and sandstones, shale-on-shale erosion surfaces, lag deposits (bone beds) and ripples suggest relatively shallow water (tens of metres) and reworking of the sea bed by waves and strong currents.

A shallow water platform in central Tennessee and deeper water conditions in eastern Tennessee require an eastward dipping sea floor (paleoslope) between these two areas. Further east however, where the Chattanooga Shale interfingers with the Brallier Formation, the paleoslope was inclined in the opposite direction (westward flowing paleocurrents). These opposing slopes formed an elongate trough along the eastern margin of the Appalachian Basin.

The portions of the Chattanooga Shale whose AMS data suggest eastward paleoflow occur between the shallow water Chattanooga of platform origin and the area where it interfingers with the Brallier Formation. Thus the eastward dipping paleoslope suggested by sedimentary features is in good agreement with AMS paleocurrent data.