Terrace and Chert Gravel at Lake Kahola, East-Central Kansas

A prominent terrace underlain by up to 2 m of alluvial chert gravel is located along the northern margin of Lake Kahola in southeastern Morris County, east-central Kansas. This landscape feature is designated as the Kahola Terrace. No quartzite nor other exotic pebbles have been found in the gravel; all material is derived from the local drainage basin in the Flint Hills. Since deposition of the Kahola Terrace gravel in the Early Pleistocene, Kahola Creek has incised its valley some 18 m and has migrated southward. This pattern is consistent with valley asymmetry for other east-flowing streams across eastern Kansas; subtle regional crustal tilting downward to the south is the most likely cause. In addition to valley asymmetry, the Kahola Creek basin also demonstrates an offset drainage divide. Ancestral Kahola Creek is considered to be an upstream tributary of the ancestral Marais des Cygnes River during the Early Pleistocene. Since then, headward erosion and stream captures have rearranged the drainage patterns of the upper Neosho River and upper Marais des Cygnes River basins.