ASYMMETRIES IN THE MIAMI-SCIOTO INTERLOBATE AREA, WEST-CENTRAL OHIO, UNITED STATES

Interlobate areas, or areas of complex drift deposition between lobes of a continental ice sheet, were first reported in the geologic literature by Chamberlin (1882) as “interlobate moraines.” Since this time there has been a paucity of publications, with only two workers (Punkari, 1997; Martini, et al., 2001) proposing models to explain the genesis of interlobate areas. Both models suggest a simple, symmetric retreat of equally active ice lobes; whereby, sub-, supra- and en-glacial debris is concentrated and deposited into a re-entrant between the ice lobes. These models, however, are too general to explain the observed geomorphology and glacial history of even the more basic interlobate areas. Recent mapping in west-central Ohio (Miami-Scioto interlobate area; Stewart, 2002), however, has suggested an alternative model for interlobate genesis, geomorphology and glacial history that is based on asymmetries in the drift deposits.

These asymmetries in interlobate landforms are both compositional and geomorphological and have been recently noted through field mapping, aerial photography and digital elevation model (DEM) analyses. Compositionally, the drift deposits comprise stagnant- versus active-ice deposits, which have been interpreted as kame versus till-based moraines (respectively). This revelation of asymmetric drift deposits associated with two adjacent lobes suggests that as one lobe stagnates, the adjacent lobe remains active; thereby, leaving behind a large-scale (>1:100,000) geomorphological signature. This signature, explicated primarily by DEM analyses, is recognized by rough, dissected high ground of gravel-and-sand-based landforms adjacent to a flatter, smoother, lower ground of finer grained landforms. Continued research in Miami-Scioto and other interlobate areas around the Michigan Basin may prove that they are generated by asymmetric ice-lobe activity, which is preserved in their respective deposits.