334 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



heig-lit from 10 feet up to fully 60 feet and are sharp and nearly conical. 

 They are all in a lowland tract on the south side of the valley, their bases 

 being but 40 to 50 feet above Clear Creek, while the uplands on the south 

 rise to a heiglit of fully 200 feet above the creek. Occasional gravel knolls 

 occur along Clear Creek Valley between this group and the western end of 

 the large gravel ridge. They appear to contain much gravel and may owe 

 their presence in this lowland tract to the same stream which formed the 

 ridge, though the method of deposition is even more problematical than, 

 that of the ridge. 



CHARACTER OF THE OUTWASH. 



In the district outside the Hartwell moraine three quite distinct classes 

 of deposits appear above the consolidated rocks: First, the earlier or 

 lUinoian drift which, covering the uplands, extends south to the glacial 

 boundary; second, the silt deposits which cover the Illinoian drift and 

 extend into the unglaciated districts; third, the morainic outwash, including 

 the gravel aprons and such valley drift as seems to be connected with the 

 moraine. The first and second having been considered, it remains only to 

 discuss the third class. In connection with this the gravel aprons and 

 valley drift in the reentrants are also considered. 



In the reentrant between the Scioto and Miami lobes there is a com- 

 plex series of gravel plains. Probably all are of somewhat later date than 

 the Hartwell moraine, and the latest are of late Wisconsin age. The broad 

 gravel plain leading down Mad River is evidently of late Wisconsin age, 

 the source of the gravel being in' the late Wisconsin moraine, which encir- 

 cles the head of the river. East from the valley of Mad River there are 

 other gravel plains, which are somewhat older than the one along the stream. 

 One which leads from West Liberty southward past King's Creek Station 

 to Urbana, connecting both at the north and south with Mad River, stands 

 but little above the Mad River gravel plain and may also belong to the late 

 Wisconsin series. It appears to be an outwash from a weak moraine lying 

 between it and Mad River Valley. 



East from this gravel plain there is a prominent moraine, noted above, 

 which extends from southern Logan County, southward past Urbana, to 

 Springfield, as indicated on the glacial maps, PI. II and XI. On the east 

 side of this moraine a gravel plain appears which leads southward near the 

 east border of the Mad River drainage basin to the headwaters of the Little 



