GENERAL FEATURES OF ILLINOIAN DRIFT SHEET. 281 



plain in Mill Creek Valley, immediately west aud about 160 feet above the 

 Ohio River. The method of deposition of this sand is not clearly under- 

 stood. Occasional small pebbles, one-eighth inch or more in diameter, 

 contained in the sand seem to indicate that it is not entirely a wind-di'ifted 

 formation. The till with its capping of silt passes beneath this sand, a fact 

 implying that the sand is more recent than the silt. The sand is probably 

 connected in some way with the floods attending the Wisconsin ice invasion. 

 The features suggest that it may have been deposited during a rise of water 

 occasioned b)- an ice gorge in the valley of Mill Creek below Carthage, 

 the width of the valley being somewhat reduced in passing Walnut Hills 

 just before it enters the Ohio Valley. 



In passing' through this lowland tract the Panhandle Railway makes 

 numerous cuttings 10 to 20 feet deep, wlaich in nearly every instance expose 

 a silt 4 to 5 feet thick, below which there is ordinary till. In one cut near 

 Pleasant Ridge there is a bed of assorted material (sand and gravel) between 

 the yellow and blue tills, but in the majority of cuttings the yellow till 

 grades downward into the blue. 



Within the village of Madisonville there is an abrupt change in the 

 substrata, the western portion of the village being underlain by till to a 

 depth of 40 to 50 feet or more, while the eastern is underlain by gravel at 

 slight depth. Above the gravel there is in some places only a silt deposit; 

 in other places there is a deeply oxidized (reddish-brown) clay carrying a 

 few pebbles. The age of the reddish clay is not known, the situation being- 

 such that it is difficult to determine. It occupies a basin or slightly 

 depressed tract and may, therefore, have received contributions in post- 

 glacial times by the wash from the neighboring highlands. It is also 

 sufficiently low to have been flooded by the Little Miami, at least down to 

 the time of the Wisconsin ice invasion. The bearing of these conditions 

 upon the question of the Madisonville chipped stone, which was found at 

 the base of this red clay, was discussed by the writer some years ago, 

 and the conclusion was reached that the deposit can not be referred with 

 certainty to glacial agencies; in fact it may be much more recent than the 

 last stage of glaciation.^ 



^ Supposed Glacial man in southwestern Ohio, by Frank Leverett: Am. Geologist, Vol. XI, 1893, 

 pp. 186-189. 



