EXPLOITATION OF DIGITAL ELEVATION MODELS TO CORRELATE REGIONAL TERRACE GENERATIONS FOR ACCURATE GEOLOGIC MAPPING: AN EXAMPLE FROM THE LICKING RIVER, KENTUCKY

Geologic maps provide a foundation for earth science, biology, ecology, and engineering investigations by guiding analyses, interpretations, and conclusions. Many of these studies are constrained by personnel, time, and cost, thereby limiting geologic map data to existing or reconnaissance-style maps that may not meet the precision requirements for modern applications. With the accessibility of high-resolution elevation datasets, it is now practical to efficiently produce project-specific geologic map data. The Kentucky Geological Survey has specifically focused on mapping surficial deposits since 2004, and exploitation of our statewide LiDAR dataset has served as a means to develop methods that allow rapid production of accurate geologic maps.

One problem common to most geographic settings involves fluvial incision, aggradation, and degradation that can produce a complex distribution of surficial deposits. Correlation of these deposits can be complicated by an extensive study area that prevents complete coverage in the field, interpolating between areas of more detailed control, smaller study areas that may not have a complete geomorphic section, or asymmetric preservation of unpaired terraces. Surface profile and histogram analysis of elevation data in fluvial valleys have the potential to solve these issues. The process consists of defining a stream centerline, constructing surface profiles normal to the centerline, histogram analysis of elevations along surface profiles, and plotting long-profile distance against histogram peaks; peaks thus represent mean terrace tread surfaces along the stream long profile. Mean terrace tread elevations can then be plotted against long-profile distance, which allows for correlation of terrace generations, estimation of paleogradients, and aids in interpretation of depositional setting. This method has been employed along the lower reach of the Licking River in northern Kentucky, a tributary of the Ohio River and major drainage throughout the Quaternary. Utilization of this model increases efficiency, maximizes field and analytical time, and yields results that aid in mapping geology of poorly exposed areas. The method can also be easily transferred and customized to any field location, but is limited by the availability of accurate elevation data.