MIGRATING LANDFORM PATTERNS THROUGH TIME: LANDSCAPE EVOLUTION IN THE KENTUCKY RIVER VALLEY

The Kentucky River flows across central and southeastern Kentucky, crossing two major physiographic provinces. The river flows across the crest of the Cincinnati Arch, and traverses a variety of gently dipping Paleozoic sedimentary strata. Previous workers have noted numerous paleochannels and fluvial deposits well above the modern course of the river. Careful examination of the modern Kentucky River Valley in central Kentucky, from Beattyville to Carrollton, reveals eight distinct valley-morphology patterns, based on alluvial width and river meander patterns. These valley-morphology patterns correspond directly with the dominant lithologies of the valley walls. Projection of these modern valley-morphology patterns to the corresponding bedrock-stratigraphy positions in the upland can explain the distribution of most of the ancient river deposits, supporting the notion that lithologically controlled landform patterns have persisted through time in this area. Entrenched meanders in the Kentucky River Palisades result from oblique bedrock quarrying in smaller meanders inherited from landform patterns developed in softer overlying strata.

Previous studies have described a “Lexington Peneplain” across much of the upland surface, and invoked cyclic landform theories to explain incision of the Kentucky River into this peneplain as a “rejuvenation” of a mature regional erosional surface. This study concludes instead that the distribution of fluvial deposits in central Kentucky does not support the erosional-cycle hypothesis, and that in fact no regional low-relief erosional surface exists or has existed in central Kentucky. The apparent accordance of ridgetops in the region results from stratigraphic control and downwasting/degradation of the original late Paleozoic depositional surface from the Alleghanian Orogeny.