260 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



westward to the Scioto Basin, and it became necessary to open a new line 

 of drainage toward the south. 



In much of the interval between Salt Creek and Hocking River, as 

 indicated above, the Wisconsin drift apparently extends to the limits of 

 glaciation. The lUinoian drift border, however, probably lies only a short 

 distance back beneath the Wisconsin. Possibly an attenuated margin of 

 lUinoian drift may be found outside the Wisconsin in a part of this interval, 

 but from the examination already made it is evident that no conspicuous 

 sheet of lUinoian drift is exposed. In the Hocking Valley and its tribu- 

 taries, and also in an abandoned valley east of Lancaster, large knolls of 

 lUinoian drift, similar to those found in the Ohio River and Paint Creek 

 valleys, appear, sometimes in clusters and sometimes isolated. In some 

 cases they are 50 to 75 feet in height. Aside from these knolls, which 

 seem confined chiefly to the valleys, the drift surface in that part of the 

 border is plane. The filling of ravines is sufficient there, and also in the 

 part of the drift border farther north, to cause a striking contrast between 

 the drift-covered and the driftless tracts. Very few knolls appear along the 

 portion of the border between the Hocking and Licking rivers. 



In the Licking Valley east of Hanover is an accumulation of sand, 

 gravel, and silt at the drift border, ^Jresenting the form of a great dam 

 across the valley. It stands more than 100 feet higher than portions of 

 the valley above and below it, and occupies the whole width of the valley 

 for a space of about 2 miles. The valley being about a mile wide, the 

 area occupied is not less than 2 square miles. The top is nearly plane, 

 but descends gradually eastward; the west, or inner face, is very abrupt. 

 The deposit appears to be an outwash from the ice sheet into a body of 

 water held in the valley to the east. Much of the material is a fine silt, 

 and there is none coarser than fine gravel. The surface capping is coarser 

 than the deeper part. West from this great dam there are low knolls in 

 the bottoms and on the slopes of the valley which were probably formed 

 beneath the ice margin. They are much less conspicuous than the dam. 

 Prominent drift knolls occur in the valley of Wilkins Run a few miles 

 northwest of Hanover, as noted by Wright,^ which appear to be of Illinoian 

 age. They rise 75 to 90 feet above the creek level, and are classed 

 by Wright as " extramarginal kames." They apparently lie outside the 



^ Glacial Boundary in Ohio, p. 52. 



