TUNNEL VALLEYS OF THE MIAMI AND SCIOTO INTERLOBATE AREA, BELLEFONTAINE, OHIO: GENERAL IMPLICATIONS

The interlobate area between the Miami and Scioto sublobes near the Bellefontaine Outlier, the topographic high of Ohio, has tunnel valleys reflecting multiple generations of meltwater discharge. These northwest to southeast trending drainage ways are generally linear, up to 3.8 km long, 0.42 km wide and 9 to 15 m deep, have steep-sided walls and may have a steep downstream end wall. A linear string of kettles typically marks the valley bottom. A discontinuous esker lies in the floor of one drainage way, another has pockmarks or small kettles downstream from the trunk drainage way, and several smaller pathways may splay from a main trunk. Regionally, an extensive till sheet and kettles developed on it are indicative of a re-advance, and therefore some of the drainage ways were re-occupied. In sum, these drainage ways fit the description of tunnel valleys reported elsewhere.

The pockmarks emanating from one of the tunnel valleys represent a single episodic high discharge event; whereas, the presence of multiple interconnecting splayed pathways indicates that the tunnel valleys developed during multiple drainage events. Preliminary observations suggest that similar tunnel valleys exist throughout the interlobate area of central Ohio, and that these constitute perhaps the southernmost tunnel valleys of the Laurentide Ice Sheet. A deglaciated radiocarbon age near one tunnel valley indicates formation after 15,000 14C yr BP making these features Late Wisconsin in age.