SEARCHING FOR MACROSCALE FOLDS IN THE NASHVILLE DOME, CENTRAL TENNESSEE

In some parts of the Nashville dome, central Tennessee, gentle folds probably formed long ago through the movement of sub-surface faults. Searching for faults, the author examined folds in the Gallatin and Bethpage 7.5’ quadrangles on the northern flank of the Nashville dome. Using the software program ArcGIS, a digital geologic map, and the National Elevation Dataset (NED), the author extracted elevations to points on the contact between the upper Ordovician Sequatchie formation and the underlying Ordovician Leipers and Catheys formations. These points were then used to create a structure surface and structure contours showing the elevation of the geologic contact. Contours which are relatively closely-spaced and linear reveal relatively steep fold limbs, and these relatively steep limbs might reveal the locations of sub-surface dip-slip faults. This analysis led to the hypothesis that there might be a north-side-down sub-surface fault striking ~290^o and having an associated structural relief of ~15 m. The hypothetical fault is ~3.2 km in length, and it is located in the vicinity of Dry Fork Creek ~11 km NE of Gallatin, TN.