GEOPHYSICAL AND GIS INVESTIGATIONS OF THE OAK OPENINGS SAND RIDGE IN NW OHIO

The Oak Openings sand belt of northwestern Ohio and southeastern Michigan formed during the recession of the Huron–Erie Lobes, when northwest Ohio was inundated by a series of ancestral lakes of modern Lake Erie. This feature consists of uniformly fine to medium grained sand up to 12 m thick in an irregular ridge 1.5 to 3 km broad deposited on lacustrine clay. Ground penetrating radar (GPR), digital elevation models (DEM), and electrical resistivity data were collected, analyzed and compared with similar features from modern coastlines. Light Detection and Ranging (LIDAR) images reveal subtle geomorphic features not previously recognized, while GPR reveals sedimentary structures within the sand. The Oak Openings belt was probably once a barrier island. The DEM, supported by GPR profiles, indicates that a recurved spit formed in what is today Secor Metropark and that this spit was incised by a channel, resulting in a delta forming to the southeast. Large-scale cross bedded reflections dipping southeast along the barrier island are probably former shoreface surfaces, and GPR profiles on the spit show sediment building from northeast to southwest, consistent with the hypothesis that this landform developed as a spit. Aeolian processes reworked higher elevations of this spit into parabolic dunes. Where the barrier is incised by a stream, a delta lies east of the barrier and GPR profiles reveal a cut-and-fill stratigraphy consistent with a delta interpretation.