INVESTIGATION OF THE SOUTHEAST REELFOOT FAULT

The Reelfoot fault, a major active fault within the New Madrid seismic zone, is projected to cross from the Mississippi River flood plain into the loess-covered Mississippi River bluffs immediately southeast of Reelfoot Lake in northwestern Tennessee. It is the objective of this research to ascertain if the Reelfoot fault displaces Tertiary and Quaternary strata within the bluff. Geologic mapping along a 12 km north-south section of the bluff line reveals that the base of the 3.1 Ma Pliocene Upland Complex (ancestral Mississippi River terrace) is displaced approximately 6 m down-to-the-north across a fault that appears to be the southeastern continuation of the Reelfoot fault. A seismic reflection line was acquired perpendicular to the projected Reelfoot fault along the base of the bluff line that reveals 15 m of down-to-the-north displacement on the top of the subsurface Eocene Memphis sand. An unpublished USGS seismic reflection line acquired in 2008, also along the bluff line but south of our line, shows an 8 m down-to-the-south fault displacement of the Memphis sand that may be a back thrust of the Reelfoot fault. The Reelfoot fault and this down-to-the-south fault appear to be the bounding faults of the southeastern extension of the Tiptonville dome within the bluffs.

River terrace mapping was also conducted along small west-flowing streams within the bluffs using LiDAR imagery. The terraces are primarily confined to the southeastern projection of the Tiptonville dome, with 2 terrace levels occurring close to the Reelfoot fault. The highest terrace is 5 m above the tributary floodplain and the lower terrace is 3 m above the floodplain thus suggesting two Quaternary displacement events on the Reelfoot fault.