EVALUATING THE ORIGIN OF THE "WASHED" LOWER MAUMEE SHORELINE OF ANCESTRAL LAKE ERIE NEAR WINAMEG, OHIO

The purpose of this study is to evaluate the stratigraphy of the lower Maumee shoreline in the ancestral basin of Lake Erie. Previous research in the basin focused on the reconstruction of lake levels and landform geomorphology rather than on landform stratigraphy. Ground penetrating radar (GPR), electrical resistivity, Schlumberger soundings surveys, the excavation of shallow pits, hand auger and Giddings probe borings, and soils maps were used to reconstruct ridge stratigraphy and lithology. Samples were also collected for particle analysis and for optically stimulated dating to better constrain the timing of events. A 7.5 series surficial map was constructed to evaluate the regional setting. Mapped environmental terrains include, modern alluvial, eolian, glacial lacustrine, glacial fluvial, and hummocky (likely ice marginal). The relatively high relief, discontinuity, and broad shape of the ridge are not consistent with the morphologic properties of nearby shorelines at higher and lower elevations. The ridge is bordered to the east by an abandon stream channel, which abruptly ends immediately south, and to the west by hummocky terrain recently mapped as a subaqueous section of the Defiance Moraine. The ridge is underlain by Paleozoic shale. The shale is overlain by a thick, > 50m unit of diamicton which is commonly described as till in well logs. The main body of the ridge is comprised of approximately 4 m thick layers of sorted sand and gravels. The sand and gravel layers are capped by a thin veneer of massive fine sand with interspersed Precambrian cobbles. GPR reflectors are hummocky to wavy discontinuous and show a sharp contact between the sand and gravel and diamicton units. The southern end of the ridge contains more fine grained sands and lacks both cobbles and the sorted sand and gravel present in the main body of the ridge. In summary, the morphology and stratigraphy of the ridge is not consistent with other strandlines in the basin and the previous explanation for its formation, that it was transgressed or “washed” by an advance of the lake, is questioned.