BORDER OF THE ILLINOIAN DRIFT. 259 



the Ohio River and the head of Brush Creek, but from Wright's desoi-iption 

 it appears to be plane surfaced and rather attenuated.^ 



From the head of Brush Creek, in Pike County, Ohio, eastward to the 

 Scioto, the Wisconsin and Illinoian drift borders are nearly coincident. 

 The Illinoian drift, ho^¥ever, appears along the south side of Paint Creek 

 Valley outside the limits of the Wisconsin. It shows a marked tendency 

 to aggregate in knolls, there being several prominent clusters between 

 Bainbridge and Chillicothe. These knolls, like those on tributaries of the 

 Ohio in southeastern Indiana, are banked against the base or stand on the 

 slope of the bluff. They rise abruptly in several instances to a height 

 of fully 100 feet above the low parts of the creek valley. Around and 

 back of these knolls there are deposits of, drift, but the high uplands south 

 of Paint Creek appear to be unglaciated. On the east border of the Scioto 

 Valley, opposite Chillicothe, a high glacial terrace, standing about 60 feet 

 above the Wisconsin terraces, or 120 feet above the Scioto River, apparently 

 connects with the Illinoian sheet of drift. Near the point of connection it 

 carries shallow basins similar to those so often found on outwash aprons 

 bordering morainic systems of Wisconsin age. The drift immediately north 

 of the head of this terrace is of gravelly constitution, and it grades into the 

 terrace in the manner so common in moraines of Wisconsin age. How- 

 ever, no knolls or ridges of morainic type were found in this portion of the 

 Illinoian drift border. 



On the hilly country between the Scioto Valley and Salt Creek Valley 

 the drift border on the high ridges is attenuated, consisting only of bowlders 

 and thin patches of till. In the ravines, however, deposits of considerable 

 depth appear. 



In Salt Creek Valley, below Adelphi, for a distance of 5 miles there are 

 heavy accumulations of drift, with nearly plane surfaces, which rise about 

 150 feet above the creek level and give the appearance of terraces on the 

 valley borders. These deposits terminate abruptly at the drift border, there 

 being a low plain extending from bluff to bluff along the portion of Salt 

 Creek east of the drift border. It is probable that a lake occupied this part 

 of the creek valley during part, if not all, of the Illinoian stage of glacia- 

 tion, for the preglacial course of the stream, as noted on page 178, was 



' Glacial Boundary in Oliio, pp. 68-72. 



