From this terrace level the bedrock rises gradually to the 700 feet (210 m) on the Lexington pene-plain surface. These terraces probably correspond in age to an erosional surface in the unglaciated areas known as the Parker strath, which was the result an erosion cycle that ended before the Kansan phase of the pre-Illinoian glaciation.[8] More recent correlation[9] places its age as pre-Nebraskan.