THE ANCESTORS OF LAKE ERIE IN NORTHEASTERN OHIO: WHAT WE KNOW AND DON'T KNOW

Several lines of inquiry have augmented our knowledge of the effects of the ancestors of Lake Erie on the distribution of surficial materials in the lakeshore counties of northeastern Ohio. Parts of the Painesville Moraine, a near-lake element of the Ashtabula Moraine, were eroded and partially covered by the Waite Hill delta graded to the 237-m level of Lake Maumee. The 30 X 60 quadrangle maps of surficial geology prepared by the Ohio Geological Survey show many features other than beaches such as deltas, bars, and spits. Alluvial terraces of many northward-flowing rivers are graded to ancestral levels of Lake Erie, and radiocarbon age dates appear to be associated with particular lake levels. Analysis of samples and cross sections from deep borings in the delta of the Cuyahoga River have delineated a possible channel graded to Early Lake Erie formed after the initiation of Niagara Falls.

There are several gaps in our knowledge about the history of the Erie Basin. The location of the Tertiary or Early Pleistocene Erigan River channel under modern Lake Erie is unknown. The effects of the ancestral lake-level changes on the surrounding landscape are problematic. Although many alluvial terraces can be traced a considerable distance upstream, there has been no study to estimate the timing of drainage reversals related to the baselevel change caused by the catastrophic drop to the level of Early Lake Erie. Many sand bodies mapped as beach ridges associated with a certain ancestral lake level are composite features consisting of littoral and deltaic deposits capped by eolian sand of unknown age. Moreover there is the more than century-old question about the sequence of lake levels. One hypothesis involves ancestral lake levels changing in response to oscillations of the ice front to the north; the other questions the survival of lower beach levels as ancestral lakes rose to higher levels. The latter hypothesis would invoke an overall drop in lake level in stages.