EVALUATION OF GLACIAL FEATURES IN NORTHWESTERN OHIO USING LIDAR DATA

The Ohio Geological Survey's current STATEMAP project is the glacial mapping of the Defiance 1:100K quadrangle, in northwestern Ohio. Part of the data preparation for the project included mosaicing of LiDAR-derived elevation raster data sets (DEMs) for the six counties included in the mapping area, as well as a hillshade raster produced from the mosaic. Scrutiny of the resultant regional elevation model revealed many interesting landscape features which require stratigraphic and depositional process explanations.

Quaternary mapping of the study area has not changed much in detail or geologic understanding in this nearly unstudied area since Leverett's mapping of a century ago. 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. NRCS SSURGO soils data indicates 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 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 last Erie Lobe moraine in the area is the Defiance Moraine, most of which was submerged by proglacial lakes that occupied the basin. Parts of this moraine contain many small raised sand flats, which are also likely ice-walled lake plains. West of the Defiance Moraine, the moraine-controlled Auglaize and Tiffin Rivers join the Maumee River at Defiance, Ohio. These three meandering rivers become a much straighter mainstem downstream from the confluence, where the Maumee is on bedrock. Straighter high-level cut terraces on the rivers above the confluence are graded to the various higher level proglacial lakes that were in the Erie Basin.