Lewis (1966) mapped two cross-lake moraines: The Erieau-Cleveland moraine 

 and the Pelee-Lorain moraine. The Erieau-Cleveland moraine extends from 

 Erieau, Ontario, to east of Cleveland, Ohio. The survey for the current study 

 did not extend far enough offshore to encounter this feature, but the trend of 

 the feature toward the U.S. shore (Fig. 21 in Lewis, 1966) indicates that the 

 feature might be related to the broad till platform mapped west of Fairport 

 Harbor. No evidence has been found of an end moraine along the Ohio shore that 

 would tie into this feature. Perhaps the moraine was eroded by streams follow- 

 ing glacial retreat or by waves and currents during the early lake stages. 



The Pelee-Lorain moraine extends from Pelee Point, Ontario, to Lorain- 

 Vermilion, Ohio. The southern part of this feature was mapped in the survey; 

 however, as with the Erieau-Cleveland moraine, no evidence has been found of an 

 end moraine along the Ohio shore. As an alternate hypothesis perhaps the above 

 named tills were deposited by a glacier limited in extent to the present lake 

 boundaries and thus are younger than the hypothesized tills. 



The overall scarcity of glaciolacustrine clay may be the result of Holocene 

 erosion. Erosion of the clay probably took place both subaerially and sub- 

 aqueously following retreat of the last Wisconsinan glacier from the Lake Erie 

 basin. This hypothesis is supported by modern erosion rates, which indicate 

 appreciably higher erosion rates of glaciolacustrine clay than of till (Carter, 

 1976). Coarse lag deposits overlying till, particularly in the Fairport Harbor 

 area, and beach deposits on the moraine off Erie, Pennsylvania (Williams and 

 Meisburger, 1982), appear to be good evidence for wave erosion during times of 

 lower lake levels. Lewis (1966) found coarse deposits overlying a smooth till 

 and glaciolacustrine clay surface along the north shore of Lake Erie; he inter- 

 preted the surface as a wave-cut terrace. This surface may be correlative with 

 the broad till surface between Fairport Harbor and Cleveland. 



4. Postglacial Sediment . 



Holocene sedimentation has contributed to a general filling in and flatten- 

 ing of the lake bottom. The sand deposits at Fairport Harbor, Lorain-Vermilion, 

 and Cedar Point (Williams, et al., 1980) are likely the product of different 

 depositional environments and different ages ranging from the early Holocene, 

 when lake levels were lower than at present, to the late Holocene. Two radio- 

 carbon ages were obtained from wood fragments in core 62 at Fairport Harbor 

 (T.L. Lewis, Cleveland State University, personal communication, 1979). At a 

 depth of 414 centimeters below the lake floor the radiocarbon age is 8250 ± 145 

 years B.P.; between 210 and 228 centimeters the radiocarbon age is 4020 ± 190 

 years B.P. These ages indicate that the deposit was built up during a rising 

 lake level, possibly the result of a combination of fluvial, deltaic, and beach- 

 nearshore environments. Aside from the sand deposits, the finer grained sedi- 

 ments appear, for the most part, to reflect present-day wave and current 

 conditions in the lake, perhaps largely related to fetch and prevailing winds 

 as hypothesized by Thomas, et al. (1976). 



V. SUMMARY 



The southern Ohio waters of Lake Erie (commonly from 1 to 7 kilometers off- 

 shore) between Conneaut and Marblehead were surveyed in August of 1977 and 1978. 

 Primary survey data consist of 576 kilometers of seismic reflection trackline 



40 



