GENERAL FEATURES OF TLLINOIAN DRIFT SHEET. 279 



deposit completely displaces the till, extending from the top to the bottom 

 of the cutting. Its beds dip and curve greatly, conditions which seem to 

 suggest that they were deposited beneath the ice sheet and disturbed by its 

 movement. There are also horizontal breaks in the till with thin beds of 

 assorted material between, features indicating an alternation of aqueous 

 with glacial deposition. The upper surface of the till is eroded and a bed 

 of assorted material 6 or 8 feet in thickness rests unconformably upon it. 

 This assorted material is principally coarse sand, but is, in places, of a 

 gravelly character, and it grades upward into a silt or fine sand nearly 

 free from pebbles. Between this assorted material and the underlying till 

 there appears in places a dark-colored band, which is sometimes of a peaty 

 character and contains bits of wood but quite as often consists simply of 

 a stain on the pebbles. In one place there was found a thin bed of very 

 fine sand between the peat and the underlying till, and in this sand minute 

 gasteropod shells were embedded. The evidence is, therefore, decisive that 

 the assorted material is a later deposit than the till, but its precise age is not 

 yet determined. The silt which overlies it and forms the surface of this 

 lowland district does not appear to be of markedly later age than the sand 

 and gravel, there being- no distinct line of separation or unconformity 

 between them. The pi-eservation of the peat beds and the shell-bearing 

 sands, as well as the sandy character of the assorted beds overlying them, 

 seems to indicate that the depositing waters had not violent movement. 

 Since the assorted beds stand only 40 to 50 feet above the ten-aces which 

 were formed in connection with the Wisconsin ice invasion and at a point 

 where the Great Miami makes an abrupt change in its course, the question 

 arises whether an unusual flood or a temporary ice gorge may not have 

 caused the water to rise to a sufficient height to pass across this low gap 

 into the Ohio and thiis produce this deposit. There appears to be nothing 

 in the character of the beds to oppose this interpretation, yet it may not 

 prove an adequate one. 



In the abandoned valley north of Cincinnati connecting Mill Creek 

 and the Little Miami River (see PI. V) there are several exposures of the 

 upper portion of the drift, from which it appears that the structure presents 

 considerable variation. The structure of the lower portion of the drift, as 

 shown by well sections, is also vai-iable, there being in places heavy beds 

 of blue silt, while in other places there is gravel, and in still others till. 



