EVALUATION OF GLACIAL FEATURES IN NORTHWESTERN OHIO USING LIDAR DATA

The Ohio Geological Survey's recent and current STATEMAP projects involve glacial mapping of the Defiance and Adrian 1:100,000 quadrangles in northwesternmost Ohio. Since Frank Leverett's mapping of a century ago, geologic understanding and glacial mapping of this area of the state has remained largely unchanged. Data preparation for the projects included mosaicking of LiDAR-derived, elevation raster data sets (or DEMs) for the six counties included in the mapping area, as well as a hillshade raster produced from the mosaic. Analysis of the resultant regional DEM revealed many landforms unusual for Ohio that require stratigraphic and depositional process interpretations. The northwest corner of the area includes the Wabash and Ft. Wayne Moraines, both deposited on the northwest side of retreating Erie Lobe ice. The highest features on the Wabash are flat-topped 'plateaus' surrounded by closed depressions. Data from soils mapping indicate that the 'plateaus' are primarily sand-filled and probably represent ice-walled lake plains. Many of the closed depressions contain bogs and/or lakes, with minimal integrated drainage. The St. Joseph River valley is between the Ft. Wayne and Wabash Moraines. Multiple, segmented linear depressions—perhaps interpreted as abandoned subice tunnels—are oriented subparallel to the moraine crests and river valley. Beach ridges mark the edge of the proglacial Maumee Lake Plain that dominates the rest of the study area. The final Erie Lobe ice in the area built the Defiance Moraine, most of which was submerged by proglacial lakes that occupied the Erie Basin. Parts of this moraine contain many small, raised sand flats, which are also probable ice-walled lake plains. West of the Defiance Moraine, the moraine-controlled Auglaize and Tiffin Rivers join the Maumee River at Defiance, Ohio. Above the confluence, the three rivers meander greatly. The river becomes much straighter downstream from the confluence; this is due to the Maumee being incised into bedrock. High-level cut terraces on the rivers above the confluence are graded to the elevations of the various high-level proglacial lakes that occupied the Erie Basin.