Structural and stratigraphic effects on geomorphology and groundwater movement in Knox dolostone terrane

The relationship of joints and fractures, geomorphology, and geohydrology, in terrain underlain by carbonate rocks of the Cambro-Ordovician Knox Group has been investigated. Detailed field data and fracture traces for a 241 acre ecology study area, entitled the Walker Branch Watershed, located at the Oak Ridge National Laboratory were compared with sinkhole morphometry data and fracture traces observable on maps and imagery for nearby areas underlain by the same rock units.

Detailed studies of the watershed included:

1. Measurement of bedrock joint and fracture orientations.

2. Fracture trace analysis.

3. Sinkhole morphometry and orientation and alignment of geohydrologic feature analyses.

4. Mapping of stratigraphy, geomorphology (karst), and geohydrologic features (i.e., springs, potholes, stream-sinks) with construction of a detailed areal geohydrologic map.

Comparison of the directional histograms prepared from the above data collected for Walker Branch Watershed and surrounding areas underlain by Knox dolostone reveals a close parallelism between the various studies, indicating each separate analysis is a viable method for predicting areas of more intense fracturing of bedrock, thus preferred groundwater movement directions. The results of this study also indicate that at least in part groundwater movement in the Knox Group is stratigraphically controlled.

Although the Knox in general is not ideally suited for waste storage/disposal, because of the abundant jointing which results in the formation of solution cavities and creates a highly variable groundwater regime with respect to space and time, the upper Mascot Formation after a site-specific study could have some utility for such purposes.