Lithology as an Erosional Control on the Cave Branch and Horn Hollow Fluviokarst Watersheds in Carter County, Kentucky

Variation in rock erodibility controls the rate of surface development providing information on the landscape evolution. In fluviokarst systems, the contrast between carbonate and non-carbonate rocks may alter the topographic evolution of the system. In Carter County, Kentucky, the Cave Branch and Horn Hollow fluviokarst systems comprise limestone overlain and capped by sandstone. Streams in the watersheds illustrate erosional differences associated with lithology. Developing as a function of the rock erodibility, uplift rates, and stream power, longitudinal stream profiles provide a means to evaluate variability in denudation rates. Using the integral method of channel profile analysis, we examine if variation in lithology has created a state of disequilibrium in the Cave Branch and Horn Hollow watersheds and if the overall development of the system is a function of erosional resistance and of differential weathering between sandstone and limestone. By scaling erosion with drainage area, the integral method allows for the comparison of streams of varying watershed areas. Streams within the sandstone portions of the watersheds displayed a greater degree of equilibrium than the limestone watersheds. Limestone stream segments generated a greater steepness index, mean value of 0.03, than sandstone segments, mean 0.01. The greater degree of disequilibrium and greater steepness index of the limestone are related to the soluble nature of limestone and the glacial-fluvial development of this area. The erosion signature recorded in the sandstone appears to represent the conditions prior to the Ohio River incision. The rapid development of the karst system is in response to the Ohio River incision disproportionally eroding the limestone. The erosional differences between the limestone and sandstone segments represent the response of the fluvial system during glacial and interglacial periods