INVESTIGATION OF QUATERNARY DISPLACEMENT ON THE UNIONTOWN FAULT, WESTERN KENTUCKY

A prominent north-trending scarp on the flood plain of the Ohio River extends 5 km from Union County into Henderson County, Kentucky. This west-facing scarp marks the boundary between the flood plain and a low terrace of the Ohio River. Scarp height diminishes from 2.5 m at its southern end to zero at the northern end where Holocene flood plain sediments appear to bury the scarp. Although it is possible that this scarp is an erosional terrace scarp, we believe that it is primarily tectonic in origin. A 30 m long by 3 m deep trench excavated across the scarp exposed flat lying flood plain strata east of the scarp and a 3 m down-to-the-west monoclinal flexure at the scarp. Five 6 m deep cores collected adjacent to the trench supports this tectonic flexure interpretation. The scarp displaces Quaternary sediment and thus represents Quaternary folding. Shallow seismic reflection lines obtained across the scarp reveal faulting that extends from the Paleozoic bedrock, up into the Quaternary alluvium, to near the base of the scarp. We believe that the monoclinal flexure formed as a consequence of underlying Quaternary reverse faulting. The fault, herein called the Uniontown fault, is a part of the Wabash Valley fault system that extends from southwestern Indiana into western Kentucky. The Ohio River makes a pronounced bend around the Uniontown fault. Movement on the Uniontown fault appears to have controlled the course of the Ohio River in a fashion similar to the New Madrid bend of the Mississippi River around the north-trending Reelfoot fault in southwestern Kentucky.