GEOMORPHIC COMPARISON OF THE LAKE WHITTLESEY AND LAKE ARKONA PALEO-SHORELINES IN THE LAKE ERIE BASIN

The shorelines of glacial Lakes Whittlesey and Arkona are adjacent to each other in elevation within the Lake Erie Basin, but they are distinctly different in geomorphic character. The Lake Whittlesey shoreline is well-defined, with prominent and continuous barrier islands or strandlines against the upland. In contrast, the Lake Arkona shoreline is very low-relief and discontinuous around the basins of the Maumee River and River Raisin valleys. For both shorelines, the relative sizes of spit complexes on the updrift and downdrift ends of shoreline segments were used to infer the dominant direction of sediment transport by wave energy. To evaluate the physical setting, each of these two shorelines was partitioned into coastal compartments with similar characteristics. For example, two prominent headlands effectively segregate the study area into two sub-basins; position within the sub-basins determined wave energy received. To compare coastal segments within each shoreline and to compare the two shorelines, a geometrical model of the shoreface was developed to generate coefficients for statistical analysis. Individual elevation transects of the shoreface were extracted from a DEM produced from 3-m LiDAR data using ESRI ArcMap 3D Analyst. Transects extended 4.5-5 km into the basin from the shoreline ridge, and were spaced 60-100 m apart. Transects were located to avoid modification of the land surface from stream drainage or human activities. The three parameters – k, H and M – of the model equation reliably capture the steepness and curvature of the upper shoreface and the slope of the lower shoreface. Best-fit lines through the shoreface profiles were evaluated with MANOVA to identify dissimilarity among coastal compartments, and to compare the Whittlesey and Arkona shorelines. Overall, the statistical evaluation was consistent with the qualitative assessment of the two shorelines based on interpreting geomorphic features. Consistently, the dominant direction of wave attack was from the north and northeast quadrants. The steepness and prominence of the Whittlesey shoreline resulted from its position against the flank of an existing topographic high, and moderate sediment input during the highstand. The Arkona shoreline was farther into the flatter central part of the basin, and it received minimal sediment.